Laser-induced retinal injury thresholds: variation with retinal irradiated area

NASA Astrophysics Data System (ADS)

Lund, David J.; Schulmeister, Karl; Seiser, Bernhard; Edthofer, Florian

2005-04-01

The retinal injury threshold for exposure to a laser source varies as a function of the irradiated area on the retina. Currently accepted guidelines for the safe use of lasers provide that the MPE will increase as the diameter of the irradiated area for retinal diameters between 25 mm and 1700 mm, based on the ED50 data available in the late 1970s. Recent studies by Zuclich and Lund produced data showing that the ED50 for ns-duration exposures at 532 nm and ms duration exposures at 590 nm varied as the square of the diameter of the irradiated area on the retina. This paper will discuss efforts to resolve the disagreement between the new data and the earlier data though an analysis of all accessible data relating the retinal injury threshold to the diameter of the incident beam on the retina and through simulations using computer models of laser-induced injury. The results show that the retinal radiant exposure required to produce retinal injury is a function of both exposure duration and retinal irradiance diameter and that the current guidelines for irradiance diameter dependence do not accurately reflect the variation of the threshold data.

Exposure to nature gardens has time-dependent associations with mood improvements for people with mid- and late-stage dementia: Innovative practice.

PubMed

White, Piran Cl; Wyatt, Jonathan; Chalfont, Garuth; Bland, J Martin; Neale, Christopher; Trepel, Dominic; Graham, Hilary

2017-01-01

Exposure to green space and nature has a potential role to play in the care of people with dementia, with possible benefits including improved mood and slower disease progression. In this observational study at a dementia care facility in the UK, we used carer-assessed measures to evaluate change in mood of residents with mid- to late-stage dementia following exposure to a nature garden. We found that exposure to nature was associated with a beneficial change in patient mood. There was a non-linear relationship between time spent outdoors and mood outcome. Improvements in patient mood were associated with relatively short duration exposures to nature, and no additional measureable increases in mood were found with exposures beyond 80-90 minutes duration. Whilst further investigation is required before causality can be determined, these results raise important questions for policy about the integration of outdoor space into the design of dementia care facilities and programmes.

Estrogen-withdrawal migraine. I. Duration of exposure required and attempted prophylaxis by premenstrual estrogen administration.

PubMed

Somerville, B W

1975-03-01

The minimum exposure to estrogen required to cause estrogen-withdrawal migraine has been studied by giving long-acting estradiol valerate to four women and short-acting estradiol benzoate to two women. It was found that several days of exposure to high estrogen levels were needed to cause migraine on estrogen withdrawal. Oral administration of estrogen supplements in the form of estradiol valerate or as conjugated equine estrogens during the premenstrual phase in four women did not significantly affect plasma levels of estradiol, nor was it effective in preventing menstrual migraine.

Quantification of Estradiol Uptake in Zebrafish Embryos and Larvae.

PubMed

Souder, Jaclyn Paige; Gorelick, Daniel A

2017-08-01

Zebrafish are a powerful model system to assess the molecular and cellular effects of exposure to toxic chemicals during embryonic development. To study the effects of environmental endocrine disruptors, embryos and larvae are commonly exposed to supraphysiologic concentrations of these compounds in the water, but their bioavailability in zebrafish is largely unknown. One hypothesis is that supraphysiologic concentrations of estrogens in the water are required to achieve physiologic levels in vivo; however, this has not been directly tested. To test this hypothesis, we developed an assay using radiolabeled estradiol ([3H]E2) to measure uptake from water at multiple concentrations and exposure durations in developing zebrafish from 0 to 5 days postfertilization (dpf). We found that [3H]E2 uptake increased with increasing concentration, duration, and developmental stage. Percent uptake from the total volume of treatment solution increased with increasing exposure duration and developmental stage, but remained constant with increasing concentration. We also found that the chorion, an acellular envelope surrounding embryos through 3 dpf, did not substantially affect [3H]E2 uptake. Finally, we found that at 1 dpf, E2 was preferentially taken up by the yolk at multiple exposure durations, while at 2 dpf E2 was preferentially taken up into the embryonic body. Our results support the hypothesis that exposing zebrafish embryos and larvae to supraphysiologic concentrations of estrogens is required to achieve physiologically relevant doses in vivo. The isotopic assay reported here will provide a foundation for determining the uptake of other compounds for teratogenicity, toxicology and drug discovery studies. © The Author 2017. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

The reduction of retinal autofluorescence caused by light exposure.

PubMed

Morgan, Jessica I W; Hunter, Jennifer J; Merigan, William H; Williams, David R

2009-12-01

A prior study showed that long exposure to 568-nm light at levels below the maximum permissible exposure safety limit produces retinal damage preceded by a transient reduction in the autofluorescence of retinal pigment epithelial (RPE) cells in vivo. The present study shows how the effects of exposure power and duration combine to produce this autofluorescence reduction and find the minimum exposure causing a detectable autofluorescence reduction. Macaque retinas were imaged using a fluorescence adaptive optics scanning laser ophthalmoscope to resolve individual RPE cells in vivo. The retina was exposed to 568-nm light over a square subtending 0.5 degrees with energies ranging from 1 to 788 J/cm(2), where power and duration were independently varied. In vivo exposures of 5 J/cm(2) and higher caused an immediate decrease in autofluorescence followed by either full autofluorescence recovery (exposures or= 247 J/cm(2)). No significant autofluorescence reduction was observed for exposures of 2 J/cm(2) and lower. Reciprocity of exposure power and duration held for the exposures tested, implying that the total energy delivered to the retina, rather than its distribution in time, determines the amount of autofluorescence reduction. That reciprocity held is consistent with a photochemical origin, which may or may not cause retinal degeneration. The implementation of safe methods for delivering light to the retina requires a better understanding of the mechanism causing autofluorescence reduction. Finally, RPE imaging was demonstrated using light levels that do not cause a detectable reduction in autofluorescence.

The Reduction of Retinal Autofluorescence Caused by Light Exposure

PubMed Central

Morgan, Jessica I. W.; Hunter, Jennifer J.; Merigan, William H.; Williams, David R.

2009-01-01

Purpose We have previously shown that long exposure to 568 nm light at levels below the maximum permissible exposure safety limit produces retinal damage preceded by a transient reduction in the autofluorescence of retinal pigment epithelial (RPE) cells in vivo. Here, we determine how the effects of exposure power and duration combine to produce this autofluorescence reduction and find the minimum exposure causing a detectable autofluorescence reduction. Methods Macaque retinas were imaged using a fluorescence adaptive optics scanning laser ophthalmoscope to resolve individual RPE cells in vivo. The retina was exposed to 568 nm light over a square subtending 0.5° with energies ranging from 1 J/cm2 to 788 J/cm2, where power and duration were independently varied. Results In vivo exposures of 5 J/cm2 and higher caused an immediate decrease in autofluorescence followed by either full autofluorescence recovery (exposures ≤ 210 J/cm2) or permanent RPE cell damage (exposures ≥ 247 J/cm2). No significant autofluorescence reduction was observed for exposures of 2 J/cm2 and lower. Reciprocity of exposure power and duration held for the exposures tested, implying that the total energy delivered to the retina, rather than its distribution in time, determines the amount of autofluorescence reduction. Conclusions That reciprocity holds is consistent with a photochemical origin, which may or may not cause retinal degeneration. The implementation of safe methods for delivering light to the retina requires a better understanding of the mechanism causing autofluorescence reduction. Finally, RPE imaging was demonstrated using light levels that do not cause a detectable reduction in autofluorescence. PMID:19628734

Animal-associated exposure to rabies virus among travelers, 1997-2012.

PubMed

Gautret, Philippe; Harvey, Kira; Pandey, Prativa; Lim, Poh Lian; Leder, Karin; Piyaphanee, Watcharapong; Shaw, Marc; McDonald, Susan C; Schwartz, Eli; Esposito, Douglas H; Parola, Philippe

2015-04-01

Among travelers, rabies cases are rare, but animal bites are relatively common. To determine which travelers are at highest risk for rabies, we studied 2,697 travelers receiving care for animal-related exposures and requiring rabies postexposure prophylaxis at GeoSentinel clinics during 1997-2012. No specific demographic characteristics differentiated these travelers from other travelers seeking medical care, making it challenging to identify travelers who might benefit from reinforced pretravel rabies prevention counseling. Median travel duration was short for these travelers: 15 days for those seeking care after completion of travel and 20 days for those seeking care during travel. This finding contradicts the view that preexposure rabies vaccine recommendations should be partly based on longer travel durations. Over half of exposures occurred in Thailand, Indonesia, Nepal, China, and India. International travelers to rabies-endemic regions, particularly Asia, should be informed about potential rabies exposure and benefits of pretravel vaccination, regardless of demographics or length of stay.

29 CFR 1926.52 - Occupational noise exposure.

Code of Federal Regulations, 2010 CFR

2010-07-01

... protective equipment as required in subpart E, shall be provided and used to reduce sound levels within the... Noise Exposures Duration per day, hours Sound level dBA slow response 8 90 6 92 4 95 3 97 2 100 11/2 102... sample computation showing an application of the formula in paragraph (d)(2)(ii) of this section is as...

29 CFR 1926.52 - Occupational noise exposure.

Code of Federal Regulations, 2011 CFR

2011-07-01

... protective equipment as required in subpart E, shall be provided and used to reduce sound levels within the... Noise Exposures Duration per day, hours Sound level dBA slow response 8 90 6 92 4 95 3 97 2 100 11/2 102... sample computation showing an application of the formula in paragraph (d)(2)(ii) of this section is as...

Effects of radiofrequency exposure emitted from a GSM mobile phone on proliferation, differentiation, and apoptosis of neural stem cells

PubMed Central

Eghlidospour, Mahsa; Ghanbari, Amir

2017-01-01

Due to the importance of neural stem cells (NSCs) in plasticity of the nervous system and treating neurodegenerative diseases, the main goal of this study was to evaluate the effects of radiofrequency radiation emitted from a GSM 900-MHz mobile phone with different exposure duration on proliferation, differentiation and apoptosis of adult murine NSCs in vitro. We used neurosphere assay to evaluate NSCs proliferation, and immunofluorescence assay of neural cell markers to examine NSCs differentiation. We also employed alamarBlue and caspase 3 apoptosis assays to assess harmful effects of mobile phone on NSCs. Our results showed that the number and size of resulting neurospheres and also the percentage of cells differentiated into neurons decreased significantly with increasing exposure duration to GSM 900-MHz radiofrequency (RF)-electromagnetic field (EMF). In contrast, exposure to GSM 900-MHz RF-EMF at different durations did not influence cell viability and apoptosis of NSCs and also their astrocytic differentiation. It is concluded that accumulating dose of GSM 900-MHz RF-EMF might have devastating effects on NSCs proliferation and neurogenesis requiring more causations in terms of using mobile devices. PMID:28713615

Effects of radiofrequency exposure emitted from a GSM mobile phone on proliferation, differentiation, and apoptosis of neural stem cells.

PubMed

Eghlidospour, Mahsa; Ghanbari, Amir; Mortazavi, Seyyed Mohammad Javad; Azari, Hassan

2017-06-01

Due to the importance of neural stem cells (NSCs) in plasticity of the nervous system and treating neurodegenerative diseases, the main goal of this study was to evaluate the effects of radiofrequency radiation emitted from a GSM 900-MHz mobile phone with different exposure duration on proliferation, differentiation and apoptosis of adult murine NSCs in vitro . We used neurosphere assay to evaluate NSCs proliferation, and immunofluorescence assay of neural cell markers to examine NSCs differentiation. We also employed alamarBlue and caspase 3 apoptosis assays to assess harmful effects of mobile phone on NSCs. Our results showed that the number and size of resulting neurospheres and also the percentage of cells differentiated into neurons decreased significantly with increasing exposure duration to GSM 900-MHz radiofrequency (RF)-electromagnetic field (EMF). In contrast, exposure to GSM 900-MHz RF-EMF at different durations did not influence cell viability and apoptosis of NSCs and also their astrocytic differentiation. It is concluded that accumulating dose of GSM 900-MHz RF-EMF might have devastating effects on NSCs proliferation and neurogenesis requiring more causations in terms of using mobile devices.

Dose-rate effects of ethylene oxide exposure on developmental toxicity.

PubMed

Weller, E; Long, N; Smith, A; Williams, P; Ravi, S; Gill, J; Henessey, R; Skornik, W; Brain, J; Kimmel, C; Kimmel, G; Holmes, L; Ryan, L

1999-08-01

In risk assessment, evaluating a health effect at a duration of exposure that is untested involves assuming that equivalent multiples of concentration (C) and duration (T) of exposure have the same effect. The limitations of this approach (attributed to F. Haber, Zur Geschichte des Gaskrieges [On the history of gas warfare], in Funf Vortrage aus den Jahren 1920-1923 [Five lectures from the years 1920-1923], 1924, Springer, Berlin, pp. 76-92), have been noted in several studies. The study presented in this paper was designed to specifically look at dose-rate (C x T) effects, and it forms an ideal case study to implement statistical models and to examine the statistical issues in risk assessment. Pregnant female C57BL/6J mice were exposed, on gestational day 7, to ethylene oxide (EtO) via inhalation for 1.5, 3, or 6 h at exposures that result in C x T multiples of 2100 or 2700 ppm-h. EtO was selected because of its short half-life, documented developmental toxicity, and relevance to exposures that occur in occupational settings. Concurrent experiments were run with animals exposed to air for similar periods. Statistical analysis using models developed to assess dose-rate effects revealed significant effects with respect to fetal death and resorptions, malformations, crown-to-rump length, and fetal weight. Animals exposed to short, high exposures of EtO on day 7 of gestation were found to have more adverse effects than animals exposed to the same C x T multiple but at longer, lower exposures. The implication for risk assessment is that applying Haber's Law could potentially lead to an underestimation of risk at a shorter duration of exposure and an overestimation of risk at a longer duration of exposure. Further research, toxicological and statistical, are required to understand the mechanism of the dose-rate effects, and how to incorporate the mechanistic information into the risk assessment decision process.

Animal-Associated Exposure to Rabies Virus among Travelers, 1997–2012

PubMed Central

Harvey, Kira; Pandey, Prativa; Lim, Poh Lian; Leder, Karin; Piyaphanee, Watcharapong; Shaw, Marc; McDonald, Susan C.; Schwartz, Eli; Esposito, Douglas H.; Parola, Philippe

2015-01-01

Among travelers, rabies cases are rare, but animal bites are relatively common. To determine which travelers are at highest risk for rabies, we studied 2,697 travelers receiving care for animal-related exposures and requiring rabies postexposure prophylaxis at GeoSentinel clinics during 1997–2012. No specific demographic characteristics differentiated these travelers from other travelers seeking medical care, making it challenging to identify travelers who might benefit from reinforced pretravel rabies prevention counseling. Median travel duration was short for these travelers: 15 days for those seeking care after completion of travel and 20 days for those seeking care during travel. This finding contradicts the view that preexposure rabies vaccine recommendations should be partly based on longer travel durations. Over half of exposures occurred in Thailand, Indonesia, Nepal, China, and India. International travelers to rabies-endemic regions, particularly Asia, should be informed about potential rabies exposure and benefits of pretravel vaccination, regardless of demographics or length of stay. PMID:25811076

Newly postulated neurodevelopmental risks of pediatric anesthesia: theories that could rock our world.

PubMed

Hays, Stephen Robert; Deshpande, Jayant K

2013-04-01

General anesthetics can induce apoptotic neurodegeneration and subsequent maladaptive behaviors in animals. Retrospective human studies suggest associations between early anesthetic exposure and subsequent adverse neurodevelopmental outcomes. The relevance of animal data to clinical practice is unclear and to our knowledge the causality underlying observed associations in humans is unknown. We reviewed newly postulated neurodevelopmental risks of pediatric anesthesia and discuss implications for the surgical care of children. We queried the MEDLINE®/PubMed® and EMBASE® databases for citations in English on pediatric anesthetic neurotoxicity with the focus on references from the last decade. Animal studies in rodents and primates demonstrate apoptotic neuropathology and subsequent maladaptive behaviors after exposure to all currently available general anesthetics with the possible exception of α2-adrenergic agonists. Similar adverse pathological and clinical effects occur after untreated pain. Anesthetic neurotoxicity in animals develops only after exposure above threshold doses and durations during a critical neurodevelopmental window of maximal synaptogenesis in the absence of concomitant painful stimuli. Anesthetic exposure outside this window or below threshold doses and durations shows no apparent neurotoxicity, while exposure in the context of concomitant painful stimuli is neuroprotective. Retrospective human studies suggest associations between early anesthetic exposure and subsequent adverse neurodevelopmental outcomes, particularly after multiple exposures. The causality underlying the associations is unknown. Ongoing investigations may clarify the risks associated with current practice. Surgical care of all patients mandates appropriate anesthesia. Neurotoxic doses and the duration of anesthetic exposure in animals may have little relevance to clinical practice, particularly surgical anesthesia for perioperative pain. The causality underlying the observed associations between early anesthetic exposure and subsequent adverse neurodevelopmental outcomes is unknown. Anesthetic exposure may be a marker of increased risk. Especially in young children, procedures requiring general anesthesia should be performed only as necessary and general anesthesia duration should be minimized. Alternatives to general anesthesia and the deferral of elective procedures beyond the first few years of life should be considered, as appropriate. Participation in ongoing efforts should be encouraged to generate further data. Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Minimum health and safety requirements for workers exposed to hand-transmitted vibration and whole-body vibration in the European Union; a review

PubMed Central

Griffin, M

2004-01-01

In 2002, the Parliament and Commission of the European Community agreed "minimum health and safety requirements" for the exposure of workers to the risks arising from vibration. The Directive defines qualitative requirements and also quantitative requirements in the form of "exposure action values" and "exposure limit values". The quantitative guidance is based on, but appears to conflict with, the guidance in International Standards for hand-transmitted vibration (ISO 5349) and whole-body vibration (ISO 2631). There is a large internal inconsistency within the Directive for short duration exposures to whole-body vibration: the two alternative methods give very different values. It would appear prudent to base actions on the qualitative guidance (i.e. reducing risk to a minimum) and only refer to the quantitative guidance where there is no other reasonable basis for the identification of risk (i.e. similar exposures are not a suspected cause of injury). Health surveillance and other precautions will be appropriate wherever there is reason to suspect a risk and will not be restricted to conditions where the exposure action value is exceeded. PMID:15090658

Gravity, the third dimension of life support in space

NASA Technical Reports Server (NTRS)

Burton, Russell R.

1994-01-01

The ascent of the human into high altitudes required a 2-D life support system that supplied: oxygen, and heat. At lower altitudes, increased oxygen concentration in the inhaled gases was useful, but at higher altitudes for longer durations, this 'clever' life support approach was no longer adequate--physiologic requirements had to provide a natural pressure-based environment. In space, the life support system requires a third dimension, gravity. Although substituting for gravity has been successful on a limited number of physiologic functions for short-duration stays in space, long durations will require the effects of the real thing for critical physiologic functions. It has been known for over a hundred years that the forces of acceleration (G) and gravity are equivalent. Therefore, gravitational stimulation in space can be achieved with centrifugation. However, for this stimulation to be effective, the dosage of G required to maintain normal physiologic function must be determined. An approximation of this dosage of G for the human can be determined with 3-day bed-rest studies including periodic centrifuge exposure. Recent research on this topic is reviewed.

The effect of exposure duration on the subjective discomfort of aircraft cabin noise.

PubMed

Huang, Yu; Jiang, Weikang

2017-01-01

The time dependency for subjective responses to noise has been a controversial question over many years. For durations of up to 10 min, the discomfort produced by three levels of noise (ie 60, 70 and 80 dBA) was investigated in this experimental study to determine the relation of discomfort to the time duration of noise. The rate of increase in discomfort with increasing duration was 1.5 dB per doubling of exposure duration, whereas it is currently assumed to be 3 dB per doubling of exposure duration. The sound dose level (SDL) was proposed to predict the discomfort caused by noise of long duration. The combination of SDL and vibration dose value (VDV) provided more consistent estimates of the equivalent comfort contours between noise and vibration over durations from 2 to 32 s than the combination of sound exposure level and VDV or that of sound pressure level and r.m.s. acceleration. Practitioner Summary: The discomfort produced by noise of long duration can be well predicted from a new definition of sound dose level, where the discomfort increases at 1.5 dB per doubling of exposure duration.

Microbiological Monitoring for the Constellation Program: Current Requirements and Future Considerations

NASA Technical Reports Server (NTRS)

Ott, C. Mark

2007-01-01

Microbiological requirements for spaceflight are based on assessments of infectious disease risk which could impact crew health or mission success. The determination of risk from infectious disease is composed of several factors including (1) crew susceptibility, (2) crew exposure to the infectious disease agent, (3) the concentration of the infectious agent, and (4) the characteristics of the infectious agent. As a result of the Health Stabilization Program, stringent monitoring, and cleaning protocols, in-flight environmental microbial monitoring is not necessary for short-duration spaceflights. However, risk factors change for long-duration missions, as exemplified by the presence of medically significant organisms in the environments of both the Mir and International Space Station (ISS). Based upon this historical evidence, requirements for short duration usage aboard the Orion Crew Exploration Vehicle and Lunar Lander Vehicle will not require in-flight monitoring; however, as mission duration increases with a Lunar Outpost, an ability to detect microbial hazard will be necessary. The nature of the detection requirements will depend on the maturity of technology in a rapidly evolving marketplace. Regardless, the hardware will still need to maximize information to discipline experts and the crew, while minimizing the size, mass, power consumption, and crew time usage. The refinement of these monitors will be a major goal in our efforts to travel successfully to Mars.

Acute inhalative exposure assessment: derivation of guideline levels with special regard to sensitive subpopulations and time scaling.

PubMed

Mielke, Hans; Gundert, Anna; Abraham, Klaus; Gundert-Remy, Ursula

2005-10-30

Risk assessment for acute airborne exposure to volatile organic compounds (VOCs), including exposure to chemical warfare agents, requires consideration of local and systemic effects at high concentrations. The operating procedure developed by the US Acute Exposure Guideline Level (AEGL) committee has gained special attention, in part because of the international collaboration in the project. The procedure defines three levels (AEGL-1: discomfort; AEGL-2: irreversible or other serious, long-lasting adverse effects; AEGL-3: life-threatening effects or death) for different exposure times (10 and 30 min, and 1, 4 and 8 h). In this article, the methodology for deriving AEGL values is reported. Extending the areas covered by the existing AEGL methodology, sensitive subpopulations are dealt with in more detail. Sensitive persons are expected to suffer from stronger effects when exposed to a given external concentration. Using a kinetic model with the sample substance dichloromethane (DCM), the higher internal exposure of children is quantified and compared to a healthy, young adult. The difference is shown to depend on age, on dose, and on duration of exposure. Furthermore, several ways are presented to derive AEGL values for exposure times which differ from the exposure duration in animal studies ('time scaling'). In comparison to the conventional procedure, the alternative approaches are based on mechanistic models of the toxicodynamic effect. Use of these models results in AEGL values which are biologically justified.

Meconium Atazanavir Concentrations and Early Language Outcomes in HIV-Exposed Uninfected Infants With Prenatal Atazanavir Exposure.

PubMed

Himes, Sarah K; Huo, Yanling; Siberry, George K; Williams, Paige L; Rice, Mabel L; Sirois, Patricia A; Frederick, Toni; Hazra, Rohan; Huestis, Marilyn A

2015-06-01

To investigate whether prenatal atazanavir (ATV) exposure, assessed by meconium antiretroviral (ARV) quantification, predicts early child language outcomes. Prenatal ATV exposure previously was associated with poorer language development in 1-year olds. Pregnant women with HIV and their uninfected infants enrolled in the Surveillance Monitoring of Antiretroviral Therapy Toxicities study. Meconium ARV concentrations were quantified by liquid chromatography-tandem mass spectrometry. Language development at 1 year was assessed with MacArthur-Bates Communicative Development Inventory (CDI) and Bayley Scales of Infant and Toddler Development-Third Edition (Bayley-III). Late language emergence was defined as ≥ 1 of 4 CDI scores ≤ 10th percentile for age. Associations between fetal ATV exposure timing and duration, meconium ATV concentration, and language outcomes were evaluated, adjusting for potential confounders. Through 2013, meconium samples were available from 175 of 432 infants with prenatal ATV exposure. Valid Bayley-III (n = 93) and CDI (n = 106) assessments also were available. After adjustment for potential confounders, higher ATV meconium concentrations were associated with lower late language emergence risk (P = 0.04) and cumulative ATV exposure duration also was associated with higher Bayley-III Language scores (P = 0.03). Maternal ATV duration and initiation week correlated with ATV meconium concentrations (positively and negatively, respectively). Higher meconium ATV concentrations were protective against developmental language delays at 1 year, suggesting the importance of fetal ATV detoxification into meconium. This information supports ATV exposure safety for infant language development. ATV is a preferred ARV for pregnant women with HIV, suggesting the importance of ATV safety investigations. Additionally, further pursuit of the influences on language development in HIV-exposed uninfected infants is required.

Benzofuran ketone dosage-dependent rayless goldenrod (Isocoma pluriflora) toxicosis in a caprine model

USDA-ARS?s Scientific Manuscript database

The objectives of this study were to determine the dosage of benzofuran ketone compounds (tremetone, 3-hydroxytremetone, dehydrotremetone, and 3-oxyangeloyltremetone) and the duration of exposure to these compounds required to produce clinical signs and the associated pathological changes of rayles ...

Emotion self-regulation and empathy depend upon longer stimulus exposure.

PubMed

Ikezawa, Satoru; Corbera, Silvia; Wexler, Bruce E

2014-10-01

Observation of others in pain induces positive elevation (pain effect) in late event-related potentials (ERP). This effect is associated with top-down attention regulating processes. It has previously been shown that stimulus exposure duration can affect top-down attentional modulation of response to threat-related stimuli. We investigated the effect of exposure duration on ERP response to others in pain. Two late ERP components, P3 and late positive potentials (LPP), from 18 healthy people were measured while they viewed pictures of hands in painful or neutral situations for either 200 or 500 ms, during two task conditions (pain judgment and counting hands). P3 and LPP pain effects during the pain judgment condition were significantly greater with 500 ms than 200 ms stimulus presentation. Ours is the first study to suggest that engagement of empathy-related self-regulatory processes reflected in late potentials requires longer exposure to the pain-related stimulus. Although this is important information about the relationship between early sensory and subsequent brain processing, and about engagement of self-regulatory processes, the neural basis of this time-dependence remains unclear. It might be important to investigate the relationship between stimulus duration and empathic response in clinical populations where issues of self-regulation, empathic response and speed of information processing exist. © The Author (2013). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

Estimating pediatric general anesthesia exposure: Quantifying duration and risk.

PubMed

Bartels, Devan Darby; McCann, Mary Ellen; Davidson, Andrew J; Polaner, David M; Whitlock, Elizabeth L; Bateman, Brian T

2018-05-02

Understanding the duration of pediatric general anesthesia exposure in contemporary practice is important for identifying groups at risk for long general anesthesia exposures and designing trials examining associations between general anesthesia exposure and neurodevelopmental outcomes. We performed a retrospective cohort analysis to estimate pediatric general anesthesia exposure duration during 2010-2015 using the National Anesthesia Clinical Outcomes Registry. A total of 1 548 021 pediatric general anesthetics were included. Median general anesthesia duration was 57 minutes (IQR: 28-86) with 90th percentile 145 minutes. Children aged <1 year had the longest median exposure duration (79 minutes, IQR: 39-119) with 90th percentile 210 minutes, and 13.7% of this very young cohort was exposed for >3 hours. High ASA physical status and care at a university hospital were associated with longer exposure times. While the vast majority (94%) of children undergoing general anesthesia are exposed for <3 hours, certain groups may be at increased risk for longer exposures. These findings may help guide the design of future trials aimed at understanding neurodevelopmental impact of prolonged exposure in these high-risk groups. © 2018 John Wiley & Sons Ltd.

29 CFR Appendix A to Subpart T to... - Examples of Conditions Which May Restrict or Limit Exposure to Hyperbaric Conditions

Code of Federal Regulations, 2012 CFR

2012-07-01

... duration of isolation. History of seizure disorder other than early febrile convulsions. Malignancies... or drug use. Conditions requiring continuous medication for control (e.g., antihistamines, steroids, barbiturates, moodaltering drugs, or insulin). Meniere's disease. Hemoglobinopathies. Obstructive or...

29 CFR Appendix A to Subpart T of... - Examples of Conditions Which May Restrict or Limit Exposure to Hyperbaric Conditions

Code of Federal Regulations, 2013 CFR

2013-07-01

... duration of isolation. History of seizure disorder other than early febrile convulsions. Malignancies... or drug use. Conditions requiring continuous medication for control (e.g., antihistamines, steroids, barbiturates, moodaltering drugs, or insulin). Meniere's disease. Hemoglobinopathies. Obstructive or...

29 CFR Appendix A to Subpart T to... - Examples of Conditions Which May Restrict or Limit Exposure to Hyperbaric Conditions

Code of Federal Regulations, 2011 CFR

2011-07-01

... duration of isolation. History of seizure disorder other than early febrile convulsions. Malignancies... or drug use. Conditions requiring continuous medication for control (e.g., antihistamines, steroids, barbiturates, moodaltering drugs, or insulin). Meniere's disease. Hemoglobinopathies. Obstructive or...

29 CFR Appendix A to Subpart T of... - Examples of Conditions Which May Restrict or Limit Exposure to Hyperbaric Conditions

Code of Federal Regulations, 2014 CFR

2014-07-01

... duration of isolation. History of seizure disorder other than early febrile convulsions. Malignancies... or drug use. Conditions requiring continuous medication for control (e.g., antihistamines, steroids, barbiturates, moodaltering drugs, or insulin). Meniere's disease. Hemoglobinopathies. Obstructive or...

29 CFR Appendix A to Subpart T to... - Examples of Conditions Which May Restrict or Limit Exposure to Hyperbaric Conditions

Code of Federal Regulations, 2010 CFR

2010-07-01

... duration of isolation. History of seizure disorder other than early febrile convulsions. Malignancies... or drug use. Conditions requiring continuous medication for control (e.g., antihistamines, steroids, barbiturates, moodaltering drugs, or insulin). Meniere's disease. Hemoglobinopathies. Obstructive or...

Physiological performance of the intertidal Manila clam (Ruditapes philippinarum) to long-term daily rhythms of air exposure

PubMed Central

Yin, Xuwang; Chen, Peng; Chen, Hai; Jin, Wen; Yan, Xiwu

2017-01-01

Intertidal organisms, especially the sessile species, often experience long-term periodic air exposure during their lives. Learning the biochemical and physiological responses of intertidal organisms to long-term periodic air exposure and the relationship to duration of air exposure provides insight into adaptation to this variably stressful environment. We studied the Manila clam, Ruditapes philippinarum, an important species in world aquaculture, as a model to evaluate survival, growth, lipid composition, oxygen consumption, oxidative damage, and antioxidant enzyme activity in relation to the duration of air exposure in a long-term (60 days) laboratory study of varying durations of periodic emersion and re-immersion. Our results show: (1) clams undergoing a longer period of air exposure had lower survival and growth compared to those given a shorter exposure, (2) levels of oxidative damage and activities of antioxidant enzymes were higher in all air exposure treatments, but did not increase with duration of air exposure, and (3) the content of docosahexaenoic acid increased with duration of air exposure. Our results can largely be interpreted in the context of the energy expenditure by the clams caused by aerobic metabolism during the daily cycle of emersion and re-immersion and the roles of docosahexaenoic acid against oxidative stress. PMID:28128354

The Effect of Exposure Duration on Visual Character Identification in Single, Whole, and Partial Report

ERIC Educational Resources Information Center

Petersen, Anders; Andersen, Tobias S.

2012-01-01

The psychometric function of single-letter identification is typically described as a function of stimulus intensity. However, the effect of stimulus exposure duration on letter identification remains poorly described. This is surprising because the effect of exposure duration has played a central role in modeling performance in whole and partial…

Brief oral stimulation, but especially oral fat exposure, elevates serum triglycerides in humans

PubMed Central

Mattes, Richard D.

2009-01-01

Oral exposure to dietary fat results in an early initial spike, followed by a prolonged elevation, of serum triglycerides in humans. The physiological and pathophysiological implications remain unknown. This study sought to determine the incidence of the effect, the required fat exposure duration, and its reliability. Thirty-four healthy adults participated in four to six response-driven trials held at least a week apart. They reported to the laboratory after an overnight fast, a catheter was placed in an antecubital vein, and a blood sample was obtained. Participants then ingested 50 g of safflower oil in capsules with 500 ml of water within 15 min to mimic a high fat meal but without oral fat exposure. Blood was collected 0, 10, 20, 30, 40, 50, 60, 120, 240, 360, and 480 min after capsule ingestion with different forms (full fat, nonfat, none) and durations of oral fat exposures (10 s, 5 min, 20 min, and/or 2 h). A triglyceride response (increase of triglyceride >10 mg/dl within 30 min) was observed in 88.2%, 70.5%, and 50% of participants with full-fat, nonfat, and no oral exposure, respectively. Test-retest reliability was 75% with full-fat exposure but only 45.4% with nonfat exposure. Full-fat and nonfat exposures led to comparable significant elevations of triglyceride over no oral stimulation with 10-s exposures, but full fat led to a greater rise than nonfat with 20 min of exposure. These data indicate that nutritionally relevant oral fat exposures reliably elevate serum triglyceride concentrations in most people. PMID:19074638

In Vivo and In Vitro Nitinol Corrosion Properties

NASA Astrophysics Data System (ADS)

Lonn, Melissa K.; Metcalf, Justin M.; Choules, Brian D.

2015-09-01

Regulatory authorities often require in vitro testing on medical devices prior to approval. Current standardized corrosion testing methods (ASTM F2129) require testing in a non-physiologic, de-oxygenated solution for a pre-exposure time of ≤1 h; however, no correlations between the prescribed simulated environment and whole blood conditions have been elucidated. This study compared open circuit potential (OCP), breakdown potentials (Eb), Eb - OCP, and cyclic polarization curves tested in vivo (OCP only) and in vitro in whole blood to those tested in phosphate-buffered saline (PBS). Two oxide thicknesses of Nitinol, two solution oxygen contents (deaerated and aerated solutions), and two pre-exposure durations (acute and chronic) were investigated. The in vitro OCP in whole blood was not significantly different than the in vivo OCP, suggesting that whole blood in vitro can be used to determine baseline corrosion behavior of medical implants. Eb - OCP tested per ASTM F2129 was comparable to acute whole blood and was conservative compared to chronic whole blood for both oxide thicknesses. However, OCP, Eb, and cyclic polarization curves were not always comparable to whole blood. Testing in aerated PBS achieved Eb, Eb - OCP, and cyclic polarization curves that were comparable to or more conservative than whole blood testing, regardless of pre-exposure duration and oxide thickness.

Acidic sulfate aerosols: characterization and exposure.

PubMed Central

Lioy, P J; Waldman, J M

1989-01-01

Exposures to acidic aerosol in the atmosphere are calculated from data reported in the scientific literature. The majority of date was not derived from studies necessarily designed to examine human exposures. Most of the studies were designed to investigate the characteristics of the atmosphere. However, the measurements were useful in defining two potential exposure situations: regional stagnation and transport conditions and local plume impacts. Levels of acidic aerosol in excess of 20 to 40 micrograms/m3 (as H2SO4) have been observed for time durations ranging from 1 to 12 hr. These were associated with high, but not necessarily the highest, atmospheric SO4(2)- levels. Exposures of 100 to 900 micrograms/m3/hr were calculated for the acid events that were monitored. In contrast, earlier London studies indicated that apparent acidity in excess of 100 micrograms/m3 (as H2SO4) was present in the atmosphere, and exposures less than 2000 micrograms/m3/hr were possible. Our present knowledge about the frequency, magnitude, and duration of acidic sulfate aerosol events and episodes is insufficient. Efforts must be made to gather more data, but these should be done in such a way that evaluation of human exposure is the focus of the research. In addition, further data are required on the mechanisms of formation of H2SO4 and on what factors can be used to predict acidic sulfate episodes. PMID:2651103

Silver-halide sensitized gelatin (SHSG) processing method for pulse holograms recorded on VRP plates

NASA Astrophysics Data System (ADS)

Evstigneeva, Maria K.; Drozdova, Olga V.; Mikhailov, Viktor N.

2002-06-01

One of the most important area of holograph applications is display holography. In case of pulse recording the requirement for vibration stability is easier than compared to CW exposure. At the same time it is widely known that the behavior of sliver-halide holographic materials strongly depends on the exposure duration. In particular the exposure sensitivity drastically decreases under nanosecond pulse duration. One of the effective ways of the diffraction efficiency improvement is SHSG processing method. This processing scheme is based on high modulation of refractive index due to microvoids appearance inside emulsion layer. It should be mentioned that the SHSG method was used earlier only in the cases when the holograms were recorded by use of CW lasers. This work is devoted to the investigation of SHSG method for pulse hologram recording on VRP plates. We used a pulsed YLF:Nd laser with pulse duration of 25 nanoseconds and wavelength of 527 nm. Both transmission and reflection holograms were recorded. The different kinds of bleaching as well as developing solutions were investigated. Our final processing scheme includes the following stages: 1) development in non-tanning solution, 2) rehalogenating bleach, 3) intermediate alcohol drying, 4) uniform second exposure, 5) second development in diluted developer, 6) reverse bleaching, 7) fixing and 8) gradient drying in isopropyl alcohol. Diffraction efficiency of transmission holograms was of about 60 percent and reflection mirror holograms was of about 45 percent. Thus we have demonstrated the SHSG processing scheme for producing effective holograms on VRP plates under pulse exposure.

Lithium cell tests at Langley Research Center. [for the long duration exposure facility

NASA Technical Reports Server (NTRS)

Bene, J.

1977-01-01

The long duration exposure facility mission places temperature requirements of from -30 F to +150 F on the batteries to be used. A hermetically sealed lithium sulfur dioxide cell was tested to predict what the temperature of the battery would be over a given spectrum of temperatures of operation. Near the end of cell discharge, as the voltage started collapsing, a very high heat output rise due to chemical reaction took place. However, if the cells were thermally insulated, they vented, ignited, and burned if an attempt was made to discharge them all the way. The cells do not go into reversal. It was determined that the root of the problem was probably the chemical reaction between the lithium and the acetonitrite solvent. A redesigned cell is discussed as well as some alternates.

40 CFR 721.4568 - Methylpolychloro aliphatic ketone.

Code of Federal Regulations, 2010 CFR

2010-07-01

... this rule, as long as the duration of exposure to P-91-1321 is less than 2 h per work shift. If the... requirements. The provisions of § 721.185 apply to this significant new use rule. (3) Determining whether a... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical...

Summary of ionizing radiation analysis on the Long Duration Exposure Facility

NASA Technical Reports Server (NTRS)

Parnell, T. A.

1992-01-01

The ionizing radiation measurements flown on the Long Duration Exposure Facility (LDEF) were contained in 15 experiments which utilized passive detectors to pursue objectives in astrophysics and to measure the radiation environment and dosimetric quantities. The spacecraft structure became sufficiently radioactive to permit additional important studies. The induced activity allows extensive radiation mapping in the structure, and independent comparison with experiment dosimetric techniques, and significant studies of secondary effects. The long exposure time, attitude stability, and number and types of measurements produced a unique and critical set of data for low Earth orbit that will not be duplicated for more than a decade. The data allow an unprecedented test, and improvement if required, of models of the radiation environment and the radiation transport methods that are used to calculate the internal radiation and its effects in spacecraft. Results of measurements in the experiments, as well as from radioactivity in the structure, have clearly shown effects from the directional properties of the radiation environment, and progress was made in the dosimetric mapping of LDEF. These measurements have already influenced some Space Station Freedom design requirements. Preliminary results from experiments, reported at this symposium and in earlier papers, show that the 5.8 years exposure considerably enhanced the scientific return of the radiation measurements. The early results give confidence that the experiments will make significant advances in the knowledge of ultra heavy cosmic rays, anomalous cosmic rays, and heavy ions trapped in the radiation belts. Unexpected phenomena were observed, which require explanation. These include stopping iron group ions between the energy ranges anticipated for anomalous and galactic cosmic rays in the LDEF orbit. A surprising concentration of the Be-7 nuclide was discovered on the 'front' surface of LDEF, apparently transported up from the stratosphere with exceptional efficiency.

Predictive Associations of Music, Anxiety, and Sedative Exposure on Mechanical Ventilation Weaning Trials

PubMed Central

Hetland, Breanna; Lindquist, Ruth; Weinert, Craig R.; Peden-McAlpine, Cynthia; Savik, Kay; Chlan, Linda

2017-01-01

Background Weaning from mechanical ventilation requires increased respiratory effort, which can heighten anxiety and later prolong the need for mechanical ventilation. Objectives To examine the predictive associations of music intervention, anxiety, sedative exposure, and patients’ characteristics on time to initiation and duration of weaning trials of patients receiving mechanical ventilation. Methods A descriptive, correlational design was used for a secondary analysis of data from a randomized trial. Music listening was defined as self-initiated, patient-directed music via headphones. Anxiety was measured daily with a visual analog scale. Sedative exposure was operationalized as a daily sedation intensity score and a sedative dose frequency. Analyses consisted of descriptive statistics, graphing, survival analysis, Cox proportional hazards regression, and linear regression. Results Of 307 patients, 52% were women and 86% were white. Mean age was 59.3 (SD, 14.4) years, mean Acute Physiology and Chronic Health Evaluation III score was 62.9 (SD, 21.6), mean duration of ventilatory support was 8 (range, 1–52) days, and mean stay in the intensive care unit was 18 (range, 2–71) days. Music listening, anxiety levels, and sedative exposure did not influence time to initial weaning trial or duration of trials. Clinical factors of illness severity, days of weaning trials, and tracheostomy placement influenced weaning patterns in this sample. Conclusions Prospective studies of music intervention and other psychophysiological factors during weaning from mechanical ventilation are needed to better understand factors that promote successful weaning. PMID:28461543

Creation of a retrospective job-exposure matrix using surrogate measures of exposure for a cohort of US career firefighters from San Francisco, Chicago and Philadelphia

PubMed Central

Dahm, Matthew M; Bertke, Stephen; Allee, Steve; Daniels, Robert D

2015-01-01

Objectives To construct a cohort-specific job-exposure matrix (JEM) using surrogate metrics of exposure for a cancer study on career firefighters from the Chicago, Philadelphia and San Francisco Fire Departments. Methods Departmental work history records, along with data on historical annual fire-runs and hours, were collected from 1950 to 2009 and coded into separate databases. These data were used to create a JEM based on standardised job titles and fire apparatus assignments using several surrogate exposure metrics to estimate firefighters’ exposure to the combustion byproducts of fire. The metrics included duration of exposure (cumulative time with a standardised exposed job title and assignment), fire-runs (cumulative events of potential fire exposure) and time at fire (cumulative hours of potential fire exposure). Results The JEM consisted of 2298 unique job titles alongside 16 174 fire apparatus assignments from the three departments, which were collapsed into 15 standardised job titles and 15 standardised job assignments. Correlations were found between fire-runs and time at fires (Pearson coefficient=0.92), duration of exposure and time at fires (Pearson coefficient=0.85), and duration of exposure and fire-runs (Pearson coefficient=0.82). Total misclassification rates were found to be between 16–30% when using duration of employment as an exposure surrogate, which has been traditionally used in most epidemiological studies, compared with using the duration of exposure surrogate metric. Conclusions The constructed JEM successfully differentiated firefighters based on gradient levels of potential exposure to the combustion byproducts of fire using multiple surrogate exposure metrics. PMID:26163543

Creation of a retrospective job-exposure matrix using surrogate measures of exposure for a cohort of US career firefighters from San Francisco, Chicago and Philadelphia.

PubMed

Dahm, Matthew M; Bertke, Stephen; Allee, Steve; Daniels, Robert D

2015-09-01

To construct a cohort-specific job-exposure matrix (JEM) using surrogate metrics of exposure for a cancer study on career firefighters from the Chicago, Philadelphia and San Francisco Fire Departments. Departmental work history records, along with data on historical annual fire-runs and hours, were collected from 1950 to 2009 and coded into separate databases. These data were used to create a JEM based on standardised job titles and fire apparatus assignments using several surrogate exposure metrics to estimate firefighters' exposure to the combustion byproducts of fire. The metrics included duration of exposure (cumulative time with a standardised exposed job title and assignment), fire-runs (cumulative events of potential fire exposure) and time at fire (cumulative hours of potential fire exposure). The JEM consisted of 2298 unique job titles alongside 16,174 fire apparatus assignments from the three departments, which were collapsed into 15 standardised job titles and 15 standardised job assignments. Correlations were found between fire-runs and time at fires (Pearson coefficient=0.92), duration of exposure and time at fires (Pearson coefficient=0.85), and duration of exposure and fire-runs (Pearson coefficient=0.82). Total misclassification rates were found to be between 16-30% when using duration of employment as an exposure surrogate, which has been traditionally used in most epidemiological studies, compared with using the duration of exposure surrogate metric. The constructed JEM successfully differentiated firefighters based on gradient levels of potential exposure to the combustion byproducts of fire using multiple surrogate exposure metrics. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Space Station as a Long Duration Exposure Facility

NASA Technical Reports Server (NTRS)

Folley, Adrienne; Scheib, Jim

1995-01-01

There is need for a space platform for experiments investigating long duration exposure to space. This platform should be maintainable in the event of a malfunction, and experiments should be easily recoverable for analysis on Earth. The International Space Station provides such a platform. The current Space Station configuration has six external experiment attachment sites, providing utilities and data support distributed along the external truss. There are also other sites that could potentially support long duration exposure experiments. This paper describes the resources provided to payloads at these sites, and cites examples of integration of proposed long duration exposure experiments on these sites. The environments to which external attached payloads will be exposed are summarized.

Secondhand smoke exposure in the workplace.

PubMed

Skeer, Margie; Cheng, Debbie M; Rigotti, Nancy A; Siegel, Michael

2005-05-01

Currently, there is little understanding of the relationship between the strength of workplace smoking policies and the likelihood and duration, not just the likelihood, of exposure to secondhand smoke at work. This study assessed self-reported exposure to secondhand smoke at work in hours per week among a cross-sectional sample of 3650 Massachusetts adults who were employed primarily at a single worksite outside the home that was not mainly outdoors. The sample data were from a larger longitudinal study designed to examine the effect of community-based tobacco control interventions on adult and youth smoking behavior. Participants were identified through a random-digit-dialing telephone survey. Multiple logistic regression and zero-inflated negative binomial regression models were used to estimate the independent effect of workplace smoking policies on the likelihood and duration of exposure to secondhand smoke. Compared to employees whose workplace banned smoking completely, those whose workplace provided designated smoking areas had 2.9 times the odds of being exposed to secondhand smoke and 1.74 times the duration of exposure, while those with no restrictions had 10.27 times the odds of being exposed and 6.34 times the duration of exposure. Workplace smoking policies substantially reduce the likelihood of self-reported secondhand smoke exposure among employees in the workplace and also greatly affect the duration of exposure.

Dose-response patterns for vibration-induced white finger

PubMed Central

Griffin, M; Bovenzi, M; Nelson, C

2003-01-01

Aims: To investigate alternative relations between cumulative exposures to hand-transmitted vibration (taking account of vibration magnitude, lifetime exposure duration, and frequency of vibration) and the development of white finger (Raynaud's phenomenon). Methods: Three previous studies have been combined to provide a group of 1557 users of powered vibratory tools in seven occupational subgroups: stone grinders, stone carvers, quarry drillers, dockyard caulkers, dockyard boilermakers, dockyard painters, and forest workers. The estimated total operating duration in hours was thus obtained for each subject, for each tool, and for all tools combined. From the vibration magnitudes and exposure durations, seven alternative measurements of cumulative exposure were calculated for each subject, using expressions of the form: dose = ∑amiti, where ai is the acceleration magnitude on tool i, ti is the lifetime exposure duration for tool i, and m = 0, 1, 2, or 4. Results: For all seven alternative dose measures, an increase in dose was associated with a significant increase in the occurrence of vibration-induced white finger, after adjustment for age and smoking. However, dose measures with high powers of acceleration (m > 1) faired less well than measures in which the weighted or unweighted acceleration, and lifetime exposure duration, were given equal weight (m = 1). Dose determined solely by the lifetime exposure duration (without consideration of the vibration magnitude) gave better predictions than measures with m greater than unity. All measures of dose calculated from the unweighted acceleration gave better predictions than the equivalent dose measures using acceleration frequency-weighted according to current standards. Conclusions: Since the total duration of exposure does not discriminate between exposures accumulated over the day and those accumulated over years, a linear relation between vibration magnitude and exposure duration seems appropriate for predicting the occurrence of vibration-induced white finger. Poorer predictions were obtained when the currently recommended frequency weighting was employed than when accelerations at all frequencies were given equal weight. Findings suggest that improvements are possible to both the frequency weighting and the time dependency used to predict the development of vibration-induced white finger in current standards. PMID:12499452

Europa Propulsion Valve Seat Material Testing

NASA Technical Reports Server (NTRS)

Addona, Brad M.

2017-01-01

The Europa mission and spacecraft design presented unique challenges for selection of valve seat materials that met the fluid compatibility requirements, and combined fluid compatibility and high radiation exposure level requirements. The Europa spacecraft pressurization system valves will be exposed to fully saturated propellant vapor for the duration of the mission. The effects of Nitrogen Tetroxide (NTO) and Monomethylhydrazine (MMH) propellant vapors on heritage valve seat materials, such as Vespel SP-1 and Polychlorotrifluoroethylene (PCTFE), were evaluated to determine if an alternate material is required. In liquid system applications, Teflon is the only available compatible valve seat material. Radiation exposure data for Teflon in an air or vacuum environment has been previously documented. Radiation exposure data for Teflon in an oxidizer environment such as NTO, was not available, and it was unknown whether the effects would be similar to those on air-exposed samples. Material testing was conducted by Marshall Space Flight Center (MSFC) and White Sands Test Facility (WSTF) to determine the effects of propellant vapor on heritage seat materials for pressurization valve applications, and the effects of combined radiation and NTO propellant exposure on Teflon. The results indicated that changes in heritage pressurization valve seat materials' properties rendered them unsuitable for the Europa application. The combined radiation and NTO exposure testing of Teflon produced results equivalent to combined radiation and air exposure results.

A 4-Week Model of House Dust Mite (HDM) Induced Allergic Airways Inflammation with Airway Remodeling.

PubMed

Woo, L N; Guo, W Y; Wang, X; Young, A; Salehi, S; Hin, A; Zhang, Y; Scott, J A; Chow, C W

2018-05-02

Animal models of allergic airways inflammation are useful tools in studying the pathogenesis of asthma and potential therapeutic interventions. The different allergic airways inflammation models available to date employ varying doses, frequency, duration and types of allergen, which lead to the development of different features of asthma; showing varying degrees of airways inflammation and hyper-responsiveness (AHR) and airways remodeling. Models that also exhibit airway remodeling, a key feature of asthma, in addition to AHR and airway inflammation typically require 5-12 weeks to develop. In this report, we describe a 4-week mouse model of house dust mite (HDM)-induced allergic airways inflammation, and compare the phenotypic features of two different doses of HDM exposures (10 µg and 25 µg) for 5 days/week with a well-characterized 8-week chronic HDM model. We found that 4 weeks of intranasal HDM (25 µg in 35 µl saline; 5 days/week) resulted in AHR, airway inflammation and airway remodeling that were comparable to the 8-week model. We conclude that this new 4-week HDM model is another useful tool in studies of human asthma that offers advantages of shorter duration for development and decreased costs when compared to other models that require longer durations of exposure (5-12 weeks) to develop.

Corneal thermal damage threshold dependence on the exposure duration for near-infrared laser radiation at 1319 nm

NASA Astrophysics Data System (ADS)

Wang, Jiarui; Jiao, Luguang; Chen, Hongxia; Yang, Zaifu; Hu, Xiangjun

2016-01-01

The corneal damage effects induced by 1319-nm transitional near-infrared laser have been investigated for years. However, the damage threshold dependence on exposure duration has not been revealed. The in vivo corneal damage thresholds (ED50s) were determined in New Zealand rabbits for 1319-nm laser radiation for exposure durations from 75 ms to 10 s. An additional corneal ED50 was determined at 1338 nm for a 5-ms exposure. The incident corneal irradiance diameter was fixed at 2 mm for all exposure conditions to avoid the influence of spot size on threshold. The ED50s given in terms of the corneal radiant exposure for exposure durations of 5 ms, 75 ms, 0.35 s, 2 s, and 10 s were 39.4, 51.5, 87.2, 156.3, and 311.1 J/cm2, respectively. The 39.4 J/cm2 was derived from the ED50 for 1338 nm (27.0 J/cm2). The ED50s for exposure durations of 75 ms to 10 s were correlated by a power law equation, ED50=128.9t0.36 in J/cm2, where t was the input in the unit of second, with correlation coefficient (R) of 0.997. Enough safe margins existed between the ED50s and the maximum permitted exposures from current laser safety standard.

Mortality Among Workers Exposed to Toluene Diisocyanate in the US Polyurethane Foam Industry: Update and Exposure-Response Analyses

PubMed Central

Pinkerton, Lynne E.; Yiin, James H.; Daniels, Robert D.; Fent, Kenneth W.

2017-01-01

Background Mortality among 4,545 toluene diisocyante (TDI)-exposed workers was updated through 2011. The primary outcome of interest was lung cancer. Methods Life table analyses, including internal analyses by exposure duration and cumulative TDI exposure, were conducted. Results Compared with the US population, all cause and all cancer mortality was increased. Lung cancer mortality was increased but was not associated with exposure duration or cumulative TDI exposure. In post hoc analyses, lung cancer mortality was associated with employment duration in finishing jobs, but not in finishing jobs involving cutting polyurethane foam. Conclusions Dermal exposure, in contrast to inhalational exposure, to TDI is expected to be greater in finishing jobs and may play a role in the observed increase in lung cancer mortality. Limitations include the lack of smoking data, uncertainty in the exposure estimates, and exposure estimates that reflected inhalational exposure only. PMID:27346061

Effect of intermittent standing and walking on physiological changes induced by head-down bed rest

NASA Technical Reports Server (NTRS)

Vernikos, J.; Ludwig, D. A.; Ertl, A. C.; Wade, C. E.; Keil, L.; OHara, D.

1994-01-01

Continuous exposure to gravity may not be necessary to prevent compromised physiological function resulting from exposure to microgravity. However, minimum gravity (G) exposure requirements, effectiveness of passive Gz versus activity in a G field, and optimal G stimulus amplitude, duration, and frequency are unknown. To partially address these questions, a 4-day, 6 degree head-down bed rest (HDBR) study (one ambulatory control day, 4 full HDBR days, one recovery day) was conducted. Nine males, 30-50 yr, were subjected to four different +1 Gz (head-foot) exposure protocols (periodic standing or controlled walking for 2 or 4 h/day in 15 min doses), plus a continuous HDBR (0 Gz) control. Standing 4 h completely prevented and standing 2 h partially prevented post-HDBR orthostatic intolerance. Both walking conditions (2 h and 4 h) attenuated the decrease in peak VO2 and prevented the increased urinary Ca2+ excretion associated with HDBR. Both 4 h conditions (standing and walking) attenuated plasma volume loss during HDBR. It was concluded that various physiological systems benefit differentially from passive +1 Gz or activity in +1 Gz and the duration (2 h vs. 4 h) of the stimulus may be an important moderating factor.

Learned helplessness: effects of response requirement and interval between treatment and testing.

PubMed

Hunziker, M H L; Dos Santos, C V

2007-11-01

Three experiments investigated learned helplessness in rats manipulating response requirements, shock duration, and intervals between treatment and testing. In Experiment 1, rats previously exposed to uncontrollable or no shocks were tested under one of four different contingencies of negative reinforcement: FR 1 or FR 2 escape contingency for running, and FR1 escape contingency for jumping (differing for the maximum shock duration of 10s or 30s). The results showed that the uncontrollable shocks produced a clear operant learning deficit (learned helplessness effect) only when the animals were tested under the jumping FR 1 escape contingency with 10-s max shock duration. Experiment 2 isolated of the effects of uncontrollability from shock exposure per se and showed that the escape deficit observed using the FR 1 escape jumping response (10-s shock duration) was produced by the uncontrollability of shock. Experiment 3 showed that using the FR 1 jumping escape contingency in the test, the learned helplessness effect was observed one, 14 or 28 days after treatment. These results suggest that running may not be an appropriate test for learned helplessness, and that many diverging results found in the literature might be accounted for by the confounding effects of respondent and operant contingencies present when running is required of rats.

Exposure Is Not Enough: Suppressing Stimuli from Awareness Can Abolish the Mere Exposure Effect

PubMed Central

Newell, Ben R.; Pearson, Joel

2013-01-01

Passive exposure to neutral stimuli increases subsequent liking of those stimuli – the mere exposure effect. Because of the broad implications for understanding and controlling human preferences, the role of conscious awareness in mere exposure has received much attention. Previous studies have claimed that the mere exposure effect can occur without conscious awareness of the stimuli. In two experiments, we applied a technique new to the mere exposure literature, called continuous flash suppression, to expose stimuli for a controlled duration with and without awareness. To ensure the reliability of the awareness manipulation, awareness was monitored on a trial-by-trial basis. Our results show that under these conditions the mere exposure effect does not occur without conscious awareness. In contrast, only when participants were aware of the stimuli did exposure increase liking and recognition. Together these data are consistent with the idea that the mere exposure effect requires conscious awareness and has important implications for theories of memory and affect. PMID:24147067

Exposure is not enough: suppressing stimuli from awareness can abolish the mere exposure effect.

PubMed

de Zilva, Daniel; Vu, Luke; Newell, Ben R; Pearson, Joel

2013-01-01

Passive exposure to neutral stimuli increases subsequent liking of those stimuli--the mere exposure effect. Because of the broad implications for understanding and controlling human preferences, the role of conscious awareness in mere exposure has received much attention. Previous studies have claimed that the mere exposure effect can occur without conscious awareness of the stimuli. In two experiments, we applied a technique new to the mere exposure literature, called continuous flash suppression, to expose stimuli for a controlled duration with and without awareness. To ensure the reliability of the awareness manipulation, awareness was monitored on a trial-by-trial basis. Our results show that under these conditions the mere exposure effect does not occur without conscious awareness. In contrast, only when participants were aware of the stimuli did exposure increase liking and recognition. Together these data are consistent with the idea that the mere exposure effect requires conscious awareness and has important implications for theories of memory and affect.

Why, when and how should exposure be considered at the within-host scale? A modelling contribution to PRRSv infection.

PubMed

Go, Natacha; Belloc, Catherine; Bidot, Caroline; Touzeau, Suzanne

2018-05-21

Understanding the impact of pathogen exposure on the within-host dynamics and its outcome in terms of infectiousness is a key issue to better understand and control the infection spread. Most experimental and modelling studies tackling this issue looked at the impact of the exposure dose on the infection probability and pathogen load, very few on the within-host immune response. Our aim was to explore the impact on the within-host response not only of the exposure dose, but also of its duration and peak, for contrasted virulence levels. We used an integrative modelling approach of the within-host dynamics at the between-cell level. We focused on the porcine reproductive and respiratory syndrome virus, a major concern for the swine industry. We quantified the impact of exposure and virulence on the viral dynamics and immune response by global sensitivity analyses and descriptive statistics. We found that the area under the viral curve, an indicator of the infection severity, was fully determined by the exposure intensity. The infection duration increased with the strain virulence and, for a given strain, exhibited a positive linear correlation with the exposure intensity logarithm and the exposure duration. Taking into account the exposure intensity is hence necessary. Besides, representing the exposure due to contacts by a single punctual dose would tend to underestimate the infection duration. As the infection severity and duration both contribute to the pig infectiousness, a prolonged exposure of the adequate intensity would be recommended in an immuno-epidemiological context.

Expanding Exposure: Can Increasing the Daily Duration of Head Start Reduce Childhood Obesity?

ERIC Educational Resources Information Center

Frisvold, David E.; Lumeng, Julie C.

2011-01-01

Coinciding with the work requirements of welfare reform in the mid-1990s, the early childhood education program, Head Start, significantly expanded to increase the availability of full-day classes. Using unique administrative data, we examine the effect of full-day compared to half-day attendance on childhood obesity. This effect is identified…

Investigations of high-speed digital imaging of low-light-level events using pulsed near-infrared laser light sources

NASA Astrophysics Data System (ADS)

Jantzen, Connie; Slagle, Rick

1997-05-01

The distinction between exposure time and sample rate is often the first point raised in any discussion of high speed imaging. Many high speed events require exposure times considerably shorter than those that can be achieved solely by the sample rate of the camera, where exposure time equals 1/sample rate. Gating, a method of achieving short exposure times in digital cameras, is often difficult to achieve for exposure time requirements shorter than 100 microseconds. This paper discusses the advantages and limitations of using the short duration light pulse of a near infrared laser with high speed digital imaging systems. By closely matching the output wavelength of the pulsed laser to the peak near infrared response of current sensors, high speed image capture can be accomplished at very low (visible) light levels of illumination. By virtue of the short duration light pulse, adjustable to as short as two microseconds, image capture of very high speed events can be achieved at relatively low sample rates of less than 100 pictures per second, without image blur. For our initial investigations, we chose a ballistic subject. The results of early experimentation revealed the limitations of applying traditional ballistic imaging methods when using a pulsed infrared lightsource with a digital imaging system. These early disappointing results clarified the need to further identify the unique system characteristics of the digital imager and pulsed infrared combination. It was also necessary to investigate how the infrared reflectance and transmittance of common materials affects the imaging process. This experimental work yielded a surprising, successful methodology which will prove useful in imaging ballistic and weapons tests, as well as forensics, flow visualizations, spray pattern analyses, and nocturnal animal behavioral studies.

Chronic Respiratory Symptoms and Lung Function in Agricultural Workers - Influence of Exposure Duration and Smoking.

PubMed

Stoleski, Saso; Minov, Jordan; Mijakoski, Dragan; Karadzinska-Bislimovska, Jovanka

2015-03-15

Job exposure in agricultural workers often leads to respiratory impairment. To assess the influence of exposure duration and smoking on chronic respiratory symptoms and ventilatory capacity in agricultural workers. A cross-sectional study covered 75 agricultural workers, compared with an equal number of office workers matched by age, exposure duration and smoking status. Standardized questionnaire was used to obtain data on chronic respiratory symptoms, job and smoking history. Lung functional testing was performed by spirometry. The prevalence of respiratory symptoms was higher in agricultural workers, with significant difference for cough (P = 0.034), and dyspnea (P = 0.028). Chronic respiratory symptoms among agricultural workers were significantly associated with duration of exposure (P < 0.05) and daily smoking (P < 0.01), as well as with daily smoking in controls (P < 0.01). The average values of spirometric parameters in exposed workers were significantly different for MEF50 (P = 0.002), MEF75 (P = 0.000), and MEF25-75 (P = 0.049). Obstructive changes in small airways in exposed workers were strongly related to exposure duration (P < 0.05) and smoking (P < 0.01). Agricultural workers with job exposure more than 15 years had more expressed adverse respiratory symptoms and lung function decline. The results confirmed the influence of agricultural exposure and daily smoking on chronic respiratory symptoms and airflow limitation, primarily targeting the small airways.

UV-B light contributes directly to the synthesis of chiloglottone floral volatiles

PubMed Central

Amarasinghe, Ranamalie; Poldy, Jacqueline; Matsuba, Yuki; Barrow, Russell A.; Hemmi, Jan M.; Pichersky, Eran; Peakall, Rod

2015-01-01

Background and Aims Australian sexually deceptive Chiloglottis orchids attract their specific male wasp pollinators by means of 2,5-dialkylcyclohexane-1,3-diones or ‘chiloglottones’, representing a newly discovered class of volatiles with unique structures. This study investigated the hypothesis that UV-B light at low intensities is directly required for chiloglottone biosynthesis in Chiloglottis trapeziformis. Methods Chiloglottone production occurs only in specific tissue (the callus) of the labellum. Cut buds and flowers, and whole plants with buds and flowers, sourced from the field, were kept in a growth chamber and interactions between growth stage of the flowers and duration and intensity of UV-B exposure on chiloglottone production were studied. The effects of the protein synthesis inhibitor cycloheximide were also examined. Key Results Chiloglottone was not present in buds, but was detected in buds that were manually opened and then exposed to sunlight, or artificial UV-B light for ≥5 min. Spectrophotometry revealed that the sepals and petals blocked UV-B light from reaching the labellum inside the bud. Rates of chiloglottone production increased with developmental stage, increasing exposure time and increasing UV-B irradiance intensity. Cycloheximide did not inhibit the initial production of chiloglottone within 5 min of UV-B exposure. However, inhibition of chiloglottone production by cycloheximide occurred over 2 h of UV-B exposure, indicating a requirement for de novo protein synthesis to sustain chiloglottone production under UV-B. Conclusions The sepals and petals of Chiloglottis orchids strongly block UV-B wavelengths of light, preventing chiloglottone production inside the bud. While initiation of chiloglottone biosynthesis requires only UV-B light, sustained chiloglottone biosynthesis requires both UV-B and de novo protein biosynthesis. The internal amounts of chiloglottone in a flower reflect the interplay between developmental stage, duration and intensity of UV-B exposure, de novo protein synthesis, and feedback loops linked to the starting amount of chiloglottone. It is concluded that UV-B light contributes directly to chiloglottone biosynthesis. These findings suggest an entirely new and unexpected biochemical reaction that might also occur in taxa other than these orchids. PMID:25649114

Estimation of optimal hologram recording modes on photothermal materials

NASA Astrophysics Data System (ADS)

Dzhamankyzov, Nasipbek Kurmanalievich; Ismanov, Yusupzhan Khakimzhanovich; Zhumaliev, Kubanychbek Myrzabekovich; Alymkulov, Samsaly Amanovich

2018-01-01

A theoretical analysis of the hologram recording process on photothermal media to estimate the required laser radiation power for the information recording as the function of the spatial frequency and radiation exposure duration is considered. Results of the analysis showed that materials with a low thermal diffusivity are necessary to increase the recording density in these media and the recording should be performed with short pulses to minimize the thermal diffusion length. A solution for the heat conduction equation for photothermal materials heated by an interference laser field was found. The solution obtained allows one to determine the required value of the recording temperature for given spatial frequencies, depending on the thermal physical parameters of the medium and on the power and duration of the heating radiation.

Sunlight Exposure and Vitamin D Status in Breastfed Infants.

PubMed

Meena, Pinky; Dabas, Aashima; Shah, Dheeraj; Malhotra, Rajeev Kumar; Madhu, S V; Gupta, Piyush

2017-02-15

To correlate the sunlight exposure in first 6 months to vitamin D status at 6 months of age in predominantly breastfed infants; and to quantify the sunlight exposure required to achieve serum 25(OH)D level >20 ng/mL, by 6 months of age. Design: Prospective cohort. Tertiary-care hospital predominantly catering to urban poor population in Delhi. 132 healthy infants, delivered at term, and predominantly breastfed were enrolled at 6-8 weeks of age. Of these, 100 infants were available for final evaluation at 6 months of age (mean (SD) follow-up: 126 (17) days). Baseline maternal vitamin D (serum 25(OH)D) levels were obtained at enrolment. The mothers were asked to maintain a daily record of duration of sunlight exposure, timing of exposure, and body surface area exposed, for the infant, on a pre-designed proforma, till the child was 6 months of age. Infant's serum 25(OH)D was measured at 6 months of age. Cumulative Sun Index was calculated as a composite measure of overall duration/time/body surface area exposed to sunlight; and correlated with the infant serum 25(OH)D after adjusting for baseline maternal serum 25(OH)D levels, season of exposure, and skin color of the infant. Sun index for exposure in morning (before 10 am) and afternoon (10 am-3 pm) were also correlated to vitamin D status. Of 100 mother-infant pairs completing the study, 90 mothers had vitamin D deficiency (serum 25(OH)D <12 ng/mL). The median duration of exposure of infants to sunlight was 17 min per week, on 6% of body surface area. Vitamin D levels of 67 (67%) infants at 6 months were less than 12 ng/mL and another 23% had insufficient levels (12-20 ng/mL). Cumulative sun index correlated positively to infant's serum 25(OH)D level at 6 months of age (r= 0.461, P<0.001). Increment in afternoon sun index by 1 unit increased the serum 25(OH)D level by 1.07 ng/mL (95% CI 0.37, 1.78; P= 0.003). A minimum 30 minute weekly afternoon sunlight exposure, between 10 am and 3 pm, over 40% body area (infant clothed in diapers, in prone position) for at least 16 weeks, was estimated requirement to achieve sufficient vitamin D levels (>20 ng/mL) by 6 months of age. There is a significant positive correlation between afternoon sunlight exposure and infant's vitamin D levels, independent of maternal vitamin D status. Randomized controlled trials are suggested to explore the effectiveness of this simple intervention to prevent or treat vitamin D deficiency in children.

Frequency-risk and duration-risk relations between second-hand smoke exposure and menopausal symptoms among middle-aged women in Guangzhou, China.

PubMed

Ye, X; Yao, Z; Xu, Y; Zhou, S; Gao, Y; Chen, S; Yang, Y

2015-04-01

Tobacco smoking and menopausal symptoms are strongly associated, but the possible effects of second-hand smoke (SHS) have not been evaluated. This study aimed to explore the possible frequency-risk and duration-risk relations between SHS exposure and menopausal symptoms among non-smoking, middle-aged women. A cross-sectional survey was conducted in Guangzhou, China using a stratified three-stage sampling method. Menopausal symptoms were measured by the modified Kupperman Index with a cut-off point of 7. The frequency-risk and duration-risk relations between SHS exposure and menopausal symptoms were examined using logistic regression models. Compared with non-exposure, SHS exposure was associated with increased menopausal symptoms (odds ratio (OR) = 1.69, 95% confidence interval (CI) 1.22-2.33 for exposure in any of the venues). The trend analysis showed that there were frequency-risk (OR = 1.43 for occasional exposure; OR = 2.30 for regular exposure; p for linear trend < 0.001) and duration-risk (OR = 1.09 for 1-15 years; OR = 1.99 for > 15 years; p for linear trend < 0.001) relations. When examining the frequency-risk and duration-risk relations by source of exposure (in homes or in workplaces), there was still evidence of increasing trend for risk of menopausal symptoms. Findings from the present study suggest that SHS exposure is positively associated with menopausal symptoms in middle-aged women in a dose-response manner and highlight the need for further research to establish the mechanisms of the association.

Comparison of Biological Responses in Rats Under Various Cigarette Smoke Exposure Conditions

PubMed Central

Tsuji, Hiroyuki; Fujimoto, Hitoshi; Matsuura, Daiki; Nishino, Tomoki; Lee, K Monica; Yoshimura, Hiroyuki

2013-01-01

A variety of exposure regimens of cigarette smoke have been used in animal models of lung diseases. In this study, we compared biological responses of smoke exposure in rats, using different smoke concentrations (wet total particulate matter [WTPM]), daily exposure durations, and total days of exposure. As a range-finding acute study, we first compared pulmonary responses between SD and F344 strains after a single nose-only exposure to mainstream cigarette smoke or LPS. Secondly, F344 rats were exposed to cigarette smoke for 2 or 13 weeks under the comparable daily exposure dose (WTPM concentration x daily exposure duration; according to Haber’s rule) but at a different WTPM concentration or daily exposure duration. Blood carboxylhemoglobin was increased linearly to the WTPM concentration, while urinary nicotine plus cotinine value was higher for the longer daily exposure than the corresponding shorter exposure groups. Gamma glutamyl transferase activity in bronchoalveolar lavage fluid (BALF) was increased dose dependently after 2 and 13 weeks of cigarette smoke exposure, while the neutrophil content in BALF was not increased notably. Smoke-exposed groups showed reduced body weight gain and increased relative lung and heart weights. While BALF parameters and the relative lung weights suggest pulmonary responses, histopathological examination showed epithelial lesions mainly in the upper respiratory organs (nose and larynx). Collectively, the results indicate that, under the employed study design, the equivalent daily exposure dose (exposure concentration x duration) induces equivalent pulmonary responses in rats. PMID:23914058

Evaluative Processing of Food Images: A Conditional Role for Viewing in Preference Formation

PubMed Central

Wolf, Alexandra; Ounjai, Kajornvut; Takahashi, Muneyoshi; Kobayashi, Shunsuke; Matsuda, Tetsuya; Lauwereyns, Johan

2018-01-01

Previous research suggested a role of gaze in preference formation, not merely as an expression of preference, but also as a causal influence. According to the gaze cascade hypothesis, the longer subjects look at an item, the more likely they are to develop a preference for it. However, to date the connection between viewing and liking has been investigated predominately with self-paced viewing conditions in which the subjects were required to select certain items from simultaneously presented stimuli on the basis of perceived visual attractiveness. Such conditions might promote a default, but non-mandatory connection between viewing and liking. To explore whether the connection is separable, we examined the evaluative processing of single naturalistic food images in a 2 × 2 design, conducted completely within subjects, in which we varied both the type of exposure (self-paced versus time-controlled) and the type of evaluation (non-exclusive versus exclusive). In the self-paced exclusive evaluation, longer viewing was associated with a higher likelihood of a positive evaluation. However, in the self-paced non-exclusive evaluation, the trend reversed such that longer viewing durations were associated with lesser ratings. Furthermore, in the time-controlled tasks, both with non-exclusive and exclusive evaluation, there was no significant relationship between the viewing duration and the evaluation. The overall pattern of results was consistent for viewing times measured in terms of exposure duration (i.e., the duration of stimulus presentation on the screen) and in terms of actual gaze duration (i.e., the amount of time the subject effectively gazed at the stimulus on the screen). The data indicated that viewing does not intrinsically lead to a higher evaluation when evaluating single food images; instead, the relationship between viewing duration and evaluation depends on the type of task. We suggest that self-determination of exposure duration may be a prerequisite for any influence from viewing time on evaluative processing, regardless of whether the influence is facilitative. Moreover, the purported facilitative link between viewing and liking appears to be limited to exclusive evaluation, when only a restricted number of items can be included in a chosen set. PMID:29942273

Evaluative Processing of Food Images: A Conditional Role for Viewing in Preference Formation.

PubMed

Wolf, Alexandra; Ounjai, Kajornvut; Takahashi, Muneyoshi; Kobayashi, Shunsuke; Matsuda, Tetsuya; Lauwereyns, Johan

2018-01-01

Previous research suggested a role of gaze in preference formation, not merely as an expression of preference, but also as a causal influence. According to the gaze cascade hypothesis, the longer subjects look at an item, the more likely they are to develop a preference for it. However, to date the connection between viewing and liking has been investigated predominately with self-paced viewing conditions in which the subjects were required to select certain items from simultaneously presented stimuli on the basis of perceived visual attractiveness. Such conditions might promote a default, but non-mandatory connection between viewing and liking. To explore whether the connection is separable, we examined the evaluative processing of single naturalistic food images in a 2 × 2 design, conducted completely within subjects, in which we varied both the type of exposure (self-paced versus time-controlled) and the type of evaluation (non-exclusive versus exclusive). In the self-paced exclusive evaluation, longer viewing was associated with a higher likelihood of a positive evaluation. However, in the self-paced non-exclusive evaluation, the trend reversed such that longer viewing durations were associated with lesser ratings. Furthermore, in the time-controlled tasks, both with non-exclusive and exclusive evaluation, there was no significant relationship between the viewing duration and the evaluation. The overall pattern of results was consistent for viewing times measured in terms of exposure duration (i.e., the duration of stimulus presentation on the screen) and in terms of actual gaze duration (i.e., the amount of time the subject effectively gazed at the stimulus on the screen). The data indicated that viewing does not intrinsically lead to a higher evaluation when evaluating single food images; instead, the relationship between viewing duration and evaluation depends on the type of task. We suggest that self-determination of exposure duration may be a prerequisite for any influence from viewing time on evaluative processing, regardless of whether the influence is facilitative. Moreover, the purported facilitative link between viewing and liking appears to be limited to exclusive evaluation, when only a restricted number of items can be included in a chosen set.

OZONE-INDUCED RESPIRATORY SYMPTOMS AND LUNG FUNCTION DECREMENTS IN HUMANS: EXPOSURE-RESPONSE MODELS

EPA Science Inventory

Short duration exposure to ozone (<8 hr) is known to result in lung function decrements and respiratory symptoms in humans. The magnitudes of these responses are functions of ozone concentration (C), activity level measured by minute ventilation (Ve), duration of exposure (T), a...

Long-Duration Orbit Exposure Experiment with Sub-Surface Microorganism from a Mars Terrestrial Analog

NASA Astrophysics Data System (ADS)

Davila, A. F.; Lim, D.; Fairen, A. G.; Uceda, E. R.; Zavaleta, J.; McKay, C.

2007-07-01

Orbit Exposure Experiments (OEE) allow us to test the possibility of life transfer between planets and moons. Deep sub-surface microorganisms may be the best candidates to survive long-term exposure to space conditions. A long duration OEE is proposed to test our hypothesis.

Acute respiratory symptoms and evacuation-related behavior after exposure to chlorine gas leakage.

PubMed

Han, Sung-Woo; Choi, Won-Jun; Yi, Min-Kee; Song, Seng-Ho; Lee, Dong-Hoon; Han, Sang-Hwan

2016-01-01

A study was performed on the accidental chlorine gas leakage that occurred in a factory of printed circuit boards manufactured without chlorine. Health examination was performed for all 52 workers suspected of exposure to chlorine gas, and their evacuation-related behaviors were observed in addition to analyzing the factors that affected the duration of their acute respiratory symptoms. Behavioral characteristics during the incidence of the accidental chlorine gas leakage, the estimated time of exposure, and the duration of subjective acute respiratory symptoms were investigated. In addition, clinical examination, chest radiography, and dental erosion test were performed. As variables that affected the duration of respiratory symptoms, dose group, body weight, age, sex, smoking, work period, and wearing a protective gear were included and analyzed by using the Cox proportional hazard model. Of 47 workers exposed to chlorine gas, 36 (77 %) developed more than one subjective symptom. The duration of the subjective symptoms according to exposure level significantly differed, with a median of 1 day (range, 0-5 days) in the low-exposure group and 2 days (range, 0-25 days) in the high-exposure group. Among the variables that affected the duration of the acute respiratory symptoms, which were analyzed by using the Cox proportional hazard model, only exposure level was significant (hazard ratio 2.087, 95 % CI = 1.119, 3.890). Regarding the evacuation-related behaviors, 22 workers (47 %) voluntarily evacuated to a safety zone immediately after recognizing the accidental exposure, but 25 workers (43 %) delayed evacuation until the start of mandatory evacuation (min 5, max 25 min). The duration of the subjective acute respiratory symptoms significantly differed between the low- and high-exposure groups. Among the 27 workers in the high-exposure group, 17 misjudged the toxicity after being aware of the gas leakage, which is a relatively high number.

Chronic Medication and or Monitoring for Long Duration Space Flight: What Should The Policy Be?

NASA Technical Reports Server (NTRS)

Hamilton, Douglas R.

2004-01-01

While a private individual with a chronic medical condition could perhaps justifiably claim the right to become a "space tourist" through informed consent, NASA and other International crew members are national assets, trained at government expense to fulfill a mission considered essential to national goals. The medical requirements/policy for selection and certification of crewmembers for long duration missions to the International Space Station (ISS) should address: (1) Crewmembers with chronic conditions that require regular dosing of life-sustaining medication for the purposes of secondary or tertiary prevention (i.e. tumor suppression therapy or anticoagulation). (2) Crew members with conditions that will be worsened by spaceflight exposure, placing them at additional personal health risk though not necessarily increasing mission risk (i.e. previous radiation exposure or preflight osteopenia/osteoporosis) The following policies are recommended. A crewmember should not be assigned to an International Space Station mission who: (3) Requires medications to sustain life or who has a disease, which requires medical procedures or diagnostics to monitor and treat same. (4) Has medical condition, which would prevent participation as a candidate in many scientific and medical operational research studies, as their underlying condition would confound the collected data. (5) Requires specialized medical devices for monitoring or treatment of a medical condition, including conditions that require special provisions to conduct routine required countermeasure activities. (6) Who has a disease or requires treatment for same, and for which the effects of space travel may be deleterious to the short or long term health of the individual, An evidence-based approach will be used to provide rationale for policy recommendations under these scenarios. Operational impacts of allowing these medical conditions to fly on the ISS will also be presented.

Temporal integration property of stereopsis after higher-order aberration correction

PubMed Central

Kang, Jian; Dai, Yun; Zhang, Yudong

2015-01-01

Based on a binocular adaptive optics visual simulator, we investigated the effect of higher-order aberration correction on the temporal integration property of stereopsis. Stereo threshold for line stimuli, viewed in 550nm monochromatic light, was measured as a function of exposure duration, with higher-order aberrations uncorrected, binocularly corrected or monocularly corrected. Under all optical conditions, stereo threshold decreased with increasing exposure duration until a steady-state threshold was reached. The critical duration was determined by a quadratic summation model and the high goodness of fit suggested this model was reasonable. For normal subjects, the slope for stereo threshold versus exposure duration was about −0.5 on logarithmic coordinates, and the critical duration was about 200 ms. Both the slope and the critical duration were independent of the optical condition of the eye, showing no significant effect of higher-order aberration correction on the temporal integration property of stereopsis. PMID:26601010

Radiation environment and shielding for early manned Mars missions

NASA Technical Reports Server (NTRS)

Hall, Stephen B.; Mccann, Michael E.

1986-01-01

The problem of shielding a crew during early manned Mars missions is discussed. Requirements for shielding are presented in the context of current astronaut exposure limits, natural ionizing radiation sources, and shielding inherent in a particular Mars vehicle configuration. An estimated range for shielding weight is presented based on the worst solar flare dose, mission duration, and inherent vehicle shielding.

Epidemiologic tools to study the influence of environmental factors on fecundity and pregnancy-related outcomes.

PubMed

Slama, Rémy; Ballester, Ferran; Casas, Maribel; Cordier, Sylvaine; Eggesbø, Merete; Iniguez, Carmen; Nieuwenhuijsen, Mark; Philippat, Claire; Rey, Sylvie; Vandentorren, Stéphanie; Vrijheid, Martine

2014-01-01

Adverse pregnancy outcomes entail a large health burden for the mother and offspring; a part of it might be avoided by better understanding the role of environmental factors in their etiology. Our aims were to review the assessment tools to characterize fecundity troubles and pregnancy-related outcomes in human populations and their sensitivity to environmental factors. For each outcome, we reviewed the possible study designs, main sources of bias, and their suggested cures. In terms of study design, for most pregnancy outcomes, cohorts with recruitment early during or even before pregnancy allow efficient characterization of pregnancy-related events, time-varying confounders, and in utero exposures that may impact birth outcomes and child health. Studies on congenital anomalies require specific designs, assessment of anomalies in medical pregnancy terminations, and, for congenital anomalies diagnosed postnatally, follow-up during several months after birth. Statistical analyses should take into account environmental exposures during the relevant time windows; survival models are an appropriate approach for fecundity, fetal loss, and gestational duration/preterm delivery. Analysis of gestational duration could distinguish pregnancies according to delivery induction (and possibly pregnancy-related conditions). In conclusion, careful design and analysis are required to better characterize environmental effects on human reproduction.

Exposure to whole-body vibration and mechanical shock: a field study of quad bike use in agriculture.

PubMed

Milosavljevic, Stephan; McBride, David I; Bagheri, Nasser; Vasiljev, Radivoj M; Mani, Ramakrishnan; Carman, Allan B; Rehn, Borje

2011-04-01

The purpose of this study was to determine exposure to whole-body vibration (WBV) and mechanical shock in rural workers who use quad bikes and to explore how personal, physical, and workplace characteristics influence exposure. A seat pad mounted triaxial accelerometer and data logger recorded full workday vibration and shock data from 130 New Zealand rural workers. Personal, physical, and workplace characteristics were gathered using a modified version of the Whole Body Vibration Health Surveillance Questionnaire. WBVs and mechanical shocks were analysed in accordance with the International Standardization for Organization (ISO 2631-1 and ISO 2631-5) standards and are presented as vibration dose value (VDV) and mechanical shock (S(ed)) exposures. VDV(Z) consistently exceeded European Union (Guide to good practice on whole body vibration. Directive 2002/44/EC on minimum health and safety, European Commission Directorate General Employment, Social Affairs and Equal Opportunities. 2006) guideline exposure action thresholds with some workers exceeding exposure limit thresholds. Exposure to mechanical shock was also evident. Increasing age had the strongest (negative) association with vibration and shock exposure with body mass index (BMI) having a similar but weaker effect. Age, daily driving duration, dairy farming, and use of two rear shock absorbers created the strongest multivariate model explaining 33% of variance in VDV(Z). Only age and dairy farming combined to explain 17% of the variance for daily mechanical shock. Twelve-month prevalence for low back pain was highest at 57.7% and lowest for upper back pain (13.8%). Personal (age and BMI), physical (shock absorbers and velocity), and workplace characteristics (driving duration and dairy farming) suggest that a mix of engineered workplace and behavioural interventions is required to reduce this level of exposure to vibration and shock.

Long Duration Exposure Facility (LDEF). Mission 1 Experiments

NASA Technical Reports Server (NTRS)

Clark, L. G. (Editor); Kinard, W. H. (Editor); Carter, D. L., Jr. (Editor); Jones, J. L., Jr. (Editor)

1984-01-01

Spaceborne experiments using the space shuttle payload known as the Long Duration Exposure Facility are described. Experiments in the fields of materials, coatings, thermal systems, power and propulsion, electronic, and optics are discussed.

The association of prenatal media marketing exposure recall with breastfeeding intentions, initiation, and duration.

PubMed

Zhang, Yuanting; Carlton, Ewa; Fein, Sara B

2013-11-01

Infant formula marketing, either directly to consumers or through health care providers, may influence women's breastfeeding intentions, initiation, and duration. However, little is known about the impact of different types of media marketing on infant feeding intentions and behavior. This study investigated whether different types of recalled prenatal media marketing exposure to formula and breastfeeding information are related to breastfeeding intentions and behavior. Data were from the Infant Feeding Practices Study II, a longitudinal study from pregnancy through the infants' first year. Sample sizes ranged from 1384 to 2530. Negative binomial, logistic regression, and survival models were used to examine associations between recalled prenatal exposure to formula or breastfeeding information and breastfeeding intentions and behavior. Exposure to infant formula information from print media was associated with shorter intended duration of exclusive breastfeeding, and formula information from websites was related to lower odds of both intended and actual initiation. Exposure to breastfeeding information from websites was related to higher odds of both intended and actual initiation and longer intended duration of any breastfeeding. Breastfeeding information from print media was associated with longer duration of any breastfeeding, but information from broadcast media was associated with shorter duration of any breastfeeding. Mothers who recall exposure to formula information from print or websites are more likely to intend to use formula or to intend to use formula earlier and are less likely to initiate breastfeeding than mothers who do not recall seeing such information.

RadWorks Storm Shelter Design for Solar Particle Event Shielding

NASA Technical Reports Server (NTRS)

Simon, Matthew A.; Cerro, Jeffrey; Clowdsley, Martha

2013-01-01

In order to enable long-duration human exploration beyond low-Earth orbit, the risks associated with exposure of astronaut crews to space radiation must be mitigated with practical and affordable solutions. The space radiation environment beyond the magnetosphere is primarily a combination of two types of radiation: galactic cosmic rays (GCR) and solar particle events (SPE). While mitigating GCR exposure remains an open issue, reducing astronaut exposure to SPEs is achievable through material shielding because they are made up primarily of medium-energy protons. In order to ensure astronaut safety for long durations beyond low-Earth orbit, SPE radiation exposure must be mitigated. However, the increasingly demanding spacecraft propulsive performance for these ambitious missions requires minimal mass and volume radiation shielding solutions which leverage available multi-functional habitat structures and logistics as much as possible. This paper describes the efforts of NASA's RadWorks Advanced Exploration Systems (AES) Project to design minimal mass SPE radiation shelter concepts leveraging available resources. Discussion items include a description of the shelter trade space, the prioritization process used to identify the four primary shelter concepts chosen for maturation, a summary of each concept's design features, a description of the radiation analysis process, and an assessment of the parasitic mass of each concept.

Safety of Enalapril in Infants Admitted to the Neonatal Intensive Care Unit.

PubMed

Ku, Lawrence C; Zimmerman, Kanecia; Benjamin, Daniel K; Clark, Reese H; Hornik, Christoph P; Smith, P Brian

2017-01-01

Enalapril is used to treat hypertension and congestive heart failure in infants. However, enalapril is not labeled for neonates, and safety data in infants are sparse. To evaluate the safety of enalapril in young infants, we conducted a retrospective cohort study of infants who were exposed to enalapril in the first 120 days of life and were cared for in 348 neonatal intensive care units from 1997 to 2012. We determined the proportion of exposed infants who developed adverse events, including death, hypotension requiring pressors, hyperkalemia, and elevated serum creatinine. Using multivariable logistic regression, we examined risk factors for adverse events, including postnatal age at first exposure, exposure duration, gestational age group, small for gestational age status, race, sex, 5-min Apgar score, and inborn status. Of a cohort of 887,910 infants, 662 infants (0.07%) were exposed to enalapril. Among exposed infants, 142 infants (21%) suffered an adverse event. The most common adverse event was hyperkalemia (13%), followed by elevated serum creatinine (5%), hypotension (4%), and death (0.5%). Significant risk factors for adverse events included postnatal age <30 days at first exposure and longer exposure duration. This study is the largest to date examining the safety of enalapril in young term and preterm infants without significant structural cardiac disease.

The role of eye movements in decision making and the prospect of exposure effects.

PubMed

Bird, Gary D; Lauwereyns, Johan; Crawford, Matthew T

2012-05-01

The aim of the current study was to follow on from previous findings that eye movements can have a causal influence on preference formation. Shimojo et al. (2003) previously found that faces that were presented for a longer duration in a two alternative forced choice task were more likely to be judged as more attractive. This effect only occurred when an eye movement was made towards the faces (with no effect when faces were centrally presented). The current study replicated Shimojo et al.'s (2003) design, whilst controlling for potential inter-stimuli interference in central presentations. As per previous findings, when eye movements were made towards the stimuli, faces that were presented for longer durations were preferred. However, faces that were centrally presented (thus not requiring an eye movement) were also preferred in the current study. The presence of an exposure duration effect for centrally presented faces casts doubt on the necessity of the eye movement in this decision making process and has implications for decision theories that place an emphasis on the role of eye movements in decision making. Copyright © 2012 Elsevier Ltd. All rights reserved.

Space Plant Biology Research at KSC

NASA Technical Reports Server (NTRS)

Romeyn, Matthew

2016-01-01

Long duration space exploration will require the capability for crews to grow their own food. Growing food is desirable from a mass-efficiency standpoint, as it is currently not feasible to carry enough prepackaged food on spacecraft to sustain crews for long duration missions. Nutritionally, fresh produce provides key nutrients that are not preserved well in pre-packaged meals (e.g. vitamins C and K) and those that are able to counteract detrimental effects of space flight, such as antioxidants to combat radiation exposure and lutein for decreasing macular degeneration. Additionally, there are significant psychological benefits of maintaining gardens, one being an indicator for the passage of time.

CS-duration and partial-reinforcement effects counteract overshadowing in select situations

PubMed Central

Urushihara, Kouji; Miller, Ralph R.

2008-01-01

Two experiments used rats in a conditioned lick suppression preparation to investigate how the conditioned stimulus (CS)-duration and partial-reinforcement effects (i.e., weakened responding due to conditioning with a CS of longer duration and presenting nonreinforced CSs intermingled with CS-unconditioned stimulus [US] pairings, respectively) interact with overshadowing. Experiment 1 found that when overshadowing treatment was combined with either extended CS duration or partial reinforcement, the response deficit was weaker than when either of these three treatments was administered alone. In Experiment 2, the generality of the findings in Experiment 1 was investigated by replicating it with various US-US intervals. This time counteraction was observed only when both the absolute duration of total CS exposure and the US-US interval were short. The results support neither the view that the ratio between the total CS exposure and total time in the context determines the CS-duration and the partial-reinforcement effects nor the view that these two effects arise from a loss of effectiveness of the excitatory CS-US association during CS-alone exposures in partial reinforcement or early periods of CS exposure with long CSs. PMID:18047218

International Space Station Urine Monitoring System Functional Integration and Science Testing

NASA Technical Reports Server (NTRS)

Rodriguez, Branelle R.; Broyan, James Lee, Jr.

2008-01-01

Exposure to microgravity during human spaceflight is required to be defined and understood as the human exploration of space requires longer duration missions. It is known that long term exposure to microgravity causes bone loss. Urine voids are capable of measuring the calcium and other metabolic byproducts in a constituent s urine. The International Space Station (ISS) Urine Monitoring System (UMS) is an automated urine collection device designed to collect urine, separate the urine and air, measure the void volume, and allow for syringe sampling. Accurate measuring and minimal cross contamination is essential to determine bone loss and the effectiveness of countermeasures. The ISS UMS provides minimal cross contamination (<0.7 ml urine) and has volume accuracy of +/-2% between 100 to 1000 ml urine voids.

International Space Station Urine Monitoring System Functional Integration and Science Testing

NASA Technical Reports Server (NTRS)

Cibuzar, Branelle R.; Broyan, James Lee, Jr.

2009-01-01

Exposure to microgravity during human spaceflight is required to be defined and understood as the human exploration of space requires longer duration missions. It is known that long term exposure to microgravity causes bone loss. Urine voids are capable of measuring the calcium and other metabolic byproducts in a constituent s urine. The International Space Station (ISS) Urine Monitoring System (UMS) is an automated urine collection device designed to collect urine, separate the urine and air, measure the void volume, and allow for syringe sampling. Accurate measuring and minimal cross contamination is essential to determine bone loss and the effectiveness of countermeasures. The ISS UMS provides minimal cross contamination (<0.7 ml urine) and has volume accuracy of +/-2% between 100 to 1000 ml urine voids.

Effects of space exposure on metals flown on the Long Duration Exposure Facility

NASA Technical Reports Server (NTRS)

Pippin, H. Gary; Bourassa, R. J.

1995-01-01

This report includes measurements on copper, aluminum, and stainless steel from the Long Duration Exposure Facility (LDEF). Summaries of the performance of a variety of metals flown on LDEF are presented. An extensive list of references directs the reader to other detailed investigations. The influence of contamination on a number of measurements is documented.

Daytime Effect of Monochromatic Blue Light on EEG Activity Depends on Duration and Timing of Exposure in Young Men

PubMed Central

Iskra-Golec, Irena; Golonka, Krystyna; Wyczesany, Miroslaw; Smith, Lawrence; Siemiginowska, Patrycja; Wątroba, Joanna

2017-01-01

Growing evidence suggests an alerting effect of monochromatic blue light on brain activity. Little is known about the moderation of those effects by timing and duration of exposure. The present electroencephalography (EEG ) study examined such moderations on delta, theta, alpha1, alpha2, and beta EEG bands. A counterbalanced repeated-measures design was applied. The 16-hr daytime period was divided into three sessions: 07:00-12:20, 12:20-17:40, and 17:40-23:00 (timing of exposure). Two light conditions comparable in luminance but differing in wavelength were applied, namely polychromatic white light and monochromatic blue light (460 nm). There were two durations of exposure—the shorter one lasting 30 min and the longer one lasting 4 hrs. Thirty male students participated in the study. Four factors analyses of variance (ANOV As, for light conditions, timing of exposure, duration of exposure, and brain area) were performed on each EEG band. Results indicated an alerting effect of short exposure to monochromatic blue light at midday and in the evening, which was demonstrated by a decrease in lower frequency bands (alpha1, delta, and theta, respectively). Long exposure to blue light may have a reverse effect, especially in the morning and at midday, when increases in lower frequency bands (theta in the morning and theta and alpha1 at midday) were observed. It can be concluded that the daytime effect of monochromatic blue light on EEG activity depends on timing and duration of exposure. PMID:29062437

Multilayer Insulation Material Guidelines

NASA Technical Reports Server (NTRS)

Finckenor, M. M.; Dooling, D.

1999-01-01

Multilayer Insulation Material Guidelines provides data on multilayer insulation materials used by previous spacecraft such as Spacelab and the Long-Duration Exposure Facility and outlines other concerns. The data presented in the document are presented for information only. They can be used as guidelines for multilayer insulation design for future spacecraft provided the thermal requirements of each new design and the environmental effects on these materials are taken into account.

Career Excess Mortality Risk from Diagnostic Radiological Exams Required for Crewmembers Participating in Long Duration Space Flight

NASA Technical Reports Server (NTRS)

Dodge, C. W.; Gonzalez, S. M.; Picco, C. E.; Johnston, S. L.; Shavers, M. R.; VanBaalen, M.

2008-01-01

NASA requires astronauts to undergo diagnostic x-ray examinations as a condition for their employment. The purpose of these procedures is to assess the astronaut s overall health and to diagnose conditions that could jeopardize the success of long duration space missions. These include exams for acceptance into the astronaut corps, routine periodic exams, as well as evaluations taken pre and post missions. Issues: According to NASA policy these medical examinations are considered occupational radiological exposures, and thus, are included when computing the astronaut s overall radiation dose and associated excess cancer mortality risk. As such, astronauts and administrators are concerned about the amount of radiation received from these procedures due to the possibility that these additional doses may cause astronauts to exceed NASA s administrative limits, thus disqualifying them from future flights. Methods: Radiation doses and cancer mortality risks following required medical radiation exposures are presented herein for representative male and female astronaut careers. Calculation of the excess cancer mortality risk was performed by adapting NASA s operational risk assessment model. Averages for astronaut height, weight, number of space missions and age at selection into the astronaut corps were used as inputs to the NASA risk model. Conclusion: The results show that the level of excess cancer mortality imposed by all required medical procedures over an entire astronaut s career is approximately the same as that resulting from a single short duration space flight (i.e. space shuttle mission). In short the summation of all medical procedures involving ionizing radiation should have no impact on the number of missions an astronaut can fly over their career. Learning Objectives: 1. The types of diagnostic medical exams which astronauts are subjected to will be presented. 2. The level of radiation dose and excess mortality risk to the average male and female astronaut will be presented.

Photochemical mechanisms of ocular photic injury (Abstract Only)

NASA Astrophysics Data System (ADS)

Stuck, Bruce E.; Lund, David J.; Zuclich, Joseph A.

2000-03-01

Mechanisms of photic injury to the eye can be categorized as photochemical, photothermal or photodistruptive. Exposure wavelength, exposure duration, ocular tissue characteristics and response criteria are key factors in the delineation of the ocular injury mechanisms. Depending on the exposure condition, one or all of the laser-tissue interaction mechanisms can be involved. Although photic injury to the eye was initially assumed to involve thermal mechanisms, more recent research has demonstrated that ocular effects can be produced by light exposure without a significant retinal temperature rise. Photochemical mechanisms are also implicated in UV photic injury to the cornea and lens. Exposure of the retina to short visible wavelengths for prolonged durations results in photochemical retinal damage with negligible localized retinal temperature elevation. For exposure conditions where photochemical mechanisms are dominate, the reciprocity of irradiance and exposure duration is apparent. The latency until observation of a photochemical lesion is often 24-48 hours whereas a thermal lesion is observed immediately or within a few hours after the exposure. Action spectra for photochemical injury to the eye are discussed in the context of ocular injury thresholds and current permissible exposure limits.

High temperature stress and spikelet fertility in rice (Oryza sativa L.).

PubMed

Jagadish, S V K; Craufurd, P Q; Wheeler, T R

2007-01-01

In future climates, greater heat tolerance at anthesis will be required in rice. The effect of high temperature at anthesis on spikelet fertility was studied on IR64 (lowland indica) and Azucena (upland japonica) at 29.6 degrees C (control), 33.7 degrees C, and 36.2 degrees C tissue temperatures. The objectives of the study were to: (i) determine the effect of temperature on flowering pattern; (ii) examine the effect of time of day of spikelet anthesis relative to a high temperature episode on spikelet fertility; and (iii) study the interactions between duration of exposure and temperature on spikelet fertility. Plants were grown at 30/24 degrees C day/night temperature in a greenhouse and transferred to growth cabinets for the temperature treatments. Individual spikelets were marked with paint to relate fertility to the time of exposure to different temperatures and durations. In both genotypes the pattern of flowering was similar, and peak anthesis occurred between 10.30 h and 11.30 h at 29.2 degrees C, and about 45 min earlier at 36.2 degrees C. In IR64, high temperature increased the number of spikelets reaching anthesis, whereas in Azucena numbers were reduced. In both genotypesor=33.7 degrees C at anthesis caused sterility. In IR64, there was no interaction between temperature and duration of exposure, and spikelet fertility was reduced by about 7% per degrees C>29.6 degrees C. In Azucena there was a significant interaction and spikelet fertility was reduced by 2.4% degrees Cd-1 above a threshold of 33 degrees C. Marking individual spikelets is an effective method to phenotype genotypes and lines for heat tolerance that removes any apparent tolerance due to temporal escape.

Human responses to bright light of different durations.

PubMed

Chang, Anne-Marie; Santhi, Nayantara; St Hilaire, Melissa; Gronfier, Claude; Bradstreet, Dayna S; Duffy, Jeanne F; Lockley, Steven W; Kronauer, Richard E; Czeisler, Charles A

2012-07-01

Light exposure in the early night induces phase delays of the circadian rhythm in melatonin in humans. Previous studies have investigated the effect of timing, intensity, wavelength, history and pattern of light stimuli on the human circadian timing system. We present results from a study of the duration–response relationship to phase-delaying bright light. Thirty-nine young healthy participants (16 female; 22.18±3.62 years) completed a 9-day inpatient study. Following three baseline days, participants underwent an initial circadian phase assessment procedure in dim light (<3 lux), and were then randomized for exposure to a bright light pulse (∼10,000 lux) of 0.2 h, 1.0 h, 2.5 h or 4.0 h duration during a 4.5 h controlled-posture episode centred in a 16 h wake episode. After another 8 h sleep episode, participants completed a second circadian phase assessment. Phase shifts were calculated from the difference in the clock time of the dim light melatonin onset (DLMO) between the initial and final phase assessments. Exposure to varying durations of bright light reset the circadian pacemaker in a dose-dependent, non-linear manner. Per minute of exposure, the 0.2 h duration was over 5 times more effective at phase delaying the circadian pacemaker (1.07±0.36 h) as compared with the 4.0 h duration (2.65±0.24 h). Acute melatonin suppression and subjective sleepiness also had a dose-dependent response to light exposure duration. These results provide strong evidence for a non-linear resetting response of the human circadian pacemaker to light duration.

Mitomycin C in pterygium treatment

PubMed Central

Martins, Thiago Gonçalves dos Santos; Costa, Ana Luiza Fontes de Azevedo; Alves, Milton Ruiz; Chammas, Roger; Schor, Paulo

2016-01-01

Pterygium is a benign lesion usually growing from the nasal side of the conjunctiva onto the cornea. Most cases of pterygium does not cause problem or requires specific treatment. The exact cause of pterygium is not clear yet, but some factors are pointed as causes, being the most important the long-term ultraviolet ray exposure. Pterygium surgery is usually considered when there are symptoms that do not respond to conservative treatment. Recurrence is the main complication of the surgery, and much has been done to avoid it. Mitomycin C (MMC) has been used as a fibroblast proliferation inhibitor during the surgery to reduce the chance of recurrence of the pterygium. This review describes the use of MMC as an adjunctive, the optimal dosage, the duration of administration of MMC and possible complications, when used during, after and before the surgery. Most studies suggest that increased exposure (dose or duration) of MMC is associated with a lower recurrence, but with higher risks of complications. PMID:27158622

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bodkin, J.L.; Udevitz, M.S.

The authors developed an analytical model (intersection model) to estimate the exposure of sea otters (Enhydra lutris), to oil from the Exxon Valdez oil spill. The authors applied estimated and assumed exposure dependent mortality rates to the Kenai Peninsula sea otter population to provide examples of the application of the model in estimating sea otter mortality. The intersection model requires three distinct types of data: (1) distribution, abundance, and movements of oil, (2) abundance and distribution of sea otters, and (3) sea otter mortality rates relative to oil exposure. Initial output of the model is an estimate of exposure ofmore » otters to oil. Exposure is measured in amount and duration of oil near an otter`s observed location (intersections). The authors provide two examples of the model using different assumptions about the relation between exposure and mortality. Because of an apparent non-linear relation between the degree of oiling and survival of otters from rehabilitation, output from the authors` examples are likely biased.« less

Investigation of the effects of long duration space exposure on active optical system components

NASA Technical Reports Server (NTRS)

Blue, M. D.

1994-01-01

This experiment was exposed to the space environment for 6 years on the Long Duration Exposure Facility (LDEF). It investigated quantitatively the effects of the long-duration space exposure on the relevant performance parameters of a representative set of electron-optic system components, including lasers, radiation detectors, filters, modulators, windows, and other related components. It evaluated the results and implications of the measurements indicating real or suspected degradation mechanisms. This information will be used to establish guidelines for the selection and use of components for space-based, electro-optic systems.

Mortality among workers exposed to toluene diisocyanate in the US polyurethane foam industry: Update and exposure-response analyses.

PubMed

Pinkerton, Lynne E; Yiin, James H; Daniels, Robert D; Fent, Kenneth W

2016-08-01

Mortality among 4,545 toluene diisocyante (TDI)-exposed workers was updated through 2011. The primary outcome of interest was lung cancer. Life table analyses, including internal analyses by exposure duration and cumulative TDI exposure, were conducted. Compared with the US population, all cause and all cancer mortality was increased. Lung cancer mortality was increased but was not associated with exposure duration or cumulative TDI exposure. In post hoc analyses, lung cancer mortality was associated with employment duration in finishing jobs, but not in finishing jobs involving cutting polyurethane foam. Dermal exposure, in contrast to inhalational exposure, to TDI is expected to be greater in finishing jobs and may play a role in the observed increase in lung cancer mortality. Limitations include the lack of smoking data, uncertainty in the exposure estimates, and exposure estimates that reflected inhalational exposure only. Am. J. Ind. Med. 59:630-643, 2016. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Childhood poverty and health: cumulative risk exposure and stress dysregulation.

PubMed

Evans, Gary W; Kim, Pilyoung

2007-11-01

A massive literature documents the inverse association between poverty or low socioeconomic status and health, but little is known about the mechanisms underlying this robust relation. We examined longitudinal relations between duration of poverty exposure since birth, cumulative risk exposure, and physiological stress in two hundred seven 13-year-olds. Chronic stress was assessed by basal blood pressure and overnight cortisol levels; stress regulation was assessed by cardiovascular reactivity to a standard acute stressor and recovery after exposure to this stressor. Cumulative risk exposure was measured by multiple physical (e.g., substandard housing) and social (e.g., family turmoil) risk factors. The greater the number of years spent living in poverty, the more elevated was overnight cortisol and the more dysregulated was the cardiovascular response (i.e., muted reactivity). Cardiovascular recovery was not affected by duration of poverty exposure. Unlike the duration of poverty exposure, concurrent poverty (i.e., during adolescence) did not affect these physiological stress outcomes. The effects of childhood poverty on stress dysregulation are largely explained by cumulative risk exposure accompanying childhood poverty.

Duration of exposure to multiple antibiotics is associated with increased risk of VRE bacteraemia: a nested case-control study.

PubMed

Gouliouris, Theodore; Warne, Ben; Cartwright, Edward J P; Bedford, Luke; Weerasuriya, Chathika K; Raven, Kathy E; Brown, Nick M; Török, M Estée; Limmathurotsakul, Direk; Peacock, Sharon J

2018-03-13

VRE bacteraemia has a high mortality and continues to defy control. Antibiotic risk factors for VRE bacteraemia have not been adequately defined. We aimed to determine the risk factors for VRE bacteraemia focusing on duration of antibiotic exposure. A retrospective matched nested case-control study was conducted amongst hospitalized patients at Cambridge University Hospitals NHS Foundation Trust (CUH) from 1 January 2006 to 31 December 2012. Cases who developed a first episode of VRE bacteraemia were matched 1:1 to controls by length of stay, year, specialty and ward type. Independent risk factors for VRE bacteraemia were evaluated using conditional logistic regression. Two hundred and thirty-five cases were compared with 220 controls. Duration of exposure to parenteral vancomycin, fluoroquinolones and meropenem was independently associated with VRE bacteraemia. Compared with patients with no exposure to vancomycin, those who received courses of 1-3 days, 4-7 days or >7 days had a stepwise increase in risk of VRE bacteraemia [conditional OR (cOR) 1.2 (95% CI 0.4-3.8), 3.8 (95% CI 1.2-11.7) and 6.6 (95% CI 1.9-22.8), respectively]. Other risk factors were: presence of a central venous catheter (CVC) [cOR 8.7 (95% CI 2.6-29.5)]; neutropenia [cOR 15.5 (95% CI 4.2-57.0)]; hypoalbuminaemia [cOR 8.5 (95% CI 2.4-29.5)]; malignancy [cOR 4.4 (95% CI 1.6-12.0)]; gastrointestinal disease [cOR 12.4 (95% CI 4.2-36.8)]; and hepatobiliary disease [cOR 7.9 (95% CI 2.1-29.9)]. Longer exposure to vancomycin, fluoroquinolones or meropenem was associated with VRE bacteraemia. Antimicrobial stewardship interventions targeting high-risk antibiotics are required to complement infection control procedures against VRE bacteraemia.

Occupational Electromagnetic Field Exposures Associated with Sleep Quality: A Cross-Sectional Study

PubMed Central

Liu, Hui; Chen, Guangdi; Pan, Yifeng; Chen, Zexin; Jin, Wen; Sun, Chuan; Chen, Chunjing; Dong, Xuanjun; Chen, Kun; Xu, Zhengping; Zhang, Shanchun; Yu, Yunxian

2014-01-01

Background Exposure to electromagnetic field (EMF) emitted by mobile phone and other machineries concerns half the world’s population and raises the problem of their impact on human health. The present study aims to explore the effects of electromagnetic field exposures on sleep quality and sleep duration among workers from electric power plant. Methods A cross-sectional study was conducted in an electric power plant of Zhejiang Province, China. A total of 854 participants were included in the final analysis. The detailed information of participants was obtained by trained investigators using a structured questionnaire, which including socio-demographic characteristics, lifestyle variables, sleep variables and electromagnetic exposures. Physical examination and venous blood collection were also carried out for every study subject. Results After grouping daily occupational electromagnetic exposure into three categories, subjects with long daily exposure time had a significantly higher risk of poor sleep quality in comparison to those with short daily exposure time. The adjusted odds ratios were 1.68 (95%CI: 1.18, 2.39) and 1.57 (95%CI: 1.10, 2.24) across tertiles. Additionally, among the subjects with long-term occupational exposure, the longer daily occupational exposure time apparently increased the risk of poor sleep quality (OR (95%CI): 2.12 (1.23∼3.66) in the second tertile; 1.83 (1.07∼3.15) in the third tertile). There was no significant association of long-term occupational exposure duration, monthly electric fee or years of mobile-phone use with sleep quality or sleep duration. Conclusions The findings showed that daily occupational EMF exposure was positively associated with poor sleep quality. It implies EMF exposure may damage human sleep quality rather than sleep duration. PMID:25340654

Epidemiologic Tools to Study the Influence of Environmental Factors on Fecundity and Pregnancy-related Outcomes

PubMed Central

Slama, Rémy; Ballester, Ferran; Casas, Maribel; Cordier, Sylvaine; Eggesbø, Merete; Iniguez, Carmen; Nieuwenhuijsen, Mark; Philippat, Claire; Rey, Sylvie; Vandentorren, Stéphanie; Vrijheid, Martine

2014-01-01

Adverse pregnancy outcomes entail a large health burden for the mother and offspring; a part of it might be avoided by better understanding the role of environmental factors in their etiology. Our aims were to review the assessment tools to characterize fecundity troubles and pregnancy-related outcomes in human populations and their sensitivity to environmental factors. For each outcome, we reviewed the possible study designs, main sources of bias, and their suggested cures. In terms of study design, for most pregnancy outcomes, cohorts with recruitment early during or even before pregnancy allow efficient characterization of pregnancy-related events, time-varying confounders, and in utero exposures that may impact birth outcomes and child health. Studies on congenital anomalies require specific designs, assessment of anomalies in medical pregnancy terminations, and, for congenital anomalies diagnosed postnatally, follow-up during several months after birth. Statistical analyses should take into account environmental exposures during the relevant time windows; survival models are an appropriate approach for fecundity, fetal loss, and gestational duration/preterm delivery. Analysis of gestational duration could distinguish pregnancies according to delivery induction (and possibly pregnancy-related conditions). In conclusion, careful design and analysis are required to better characterize environmental effects on human reproduction. PMID:24363355

Design of Two RadWorks Storm Shelters for Solar Particle Event Shielding

NASA Technical Reports Server (NTRS)

Simon, Matthew; Cerro, Jeffery; Latorella, Kara; Clowdsley, Martha; Watson, Judith; Albertson, Cindy; Norman, Ryan; Le Boffe, Vincent; Walker, Steven

2014-01-01

In order to enable long-duration human exploration beyond low-Earth orbit, the risks associated with exposure of astronaut crews to space radiation must be mitigated with practical and affordable solutions. The space radiation environment beyond the magnetosphere is primarily a combination of two types of radiation: galactic cosmic rays (GCR) and solar particle events (SPE). While mitigating GCR exposure remains an open issue, reducing astronaut exposure to SPEs is achievable through material shielding because they are made up primarily of medium-energy protons. In order to ensure astronaut safety for long durations beyond low-Earth orbit, SPE radiation exposure must be mitigated. However, the increasingly demanding spacecraft propulsive performance for these ambitious missions requires minimal mass and volume radiation shielding solutions which leverage available multi-functional habitat structures and logistics as much as possible. This paper describes the efforts of NASA's RadWorks Advanced Exploration Systems (AES) Project to design two minimal mass SPE radiation shelter concepts leveraging available resources: one based upon reconfiguring habitat interiors to create a centralized protection area and one based upon augmenting individual crew quarters with waterwalls and logistics. Discussion items include the design features of the concepts, a radiation analysis of their implementations, an assessment of the parasitic mass of each concept, and the result of a human in the loop evaluation performed to drive out design and operational issues.

Impact of Early Postnatal Androgen Exposure on Voice Development

PubMed Central

Grisa, Leila; Leonel, Maria L.; Gonçalves, Maria I. R.; Pletsch, Francisco; Sade, Elis R.; Custódio, Gislaine; Zagonel, Ivete P. S.; Longui, Carlos A.; Figueiredo, Bonald C.

2012-01-01

Background The impact of early postnatal androgen exposure on female laryngeal tissue may depend on certain characteristics of this exposure. We assessed the impact of the dose, duration, and timing of early androgen exposure on the vocal development of female subjects who had been treated for adrenocortical tumor (ACT) in childhood. Methods The long-term effects of androgen exposure on the fundamental vocal frequency (F0), vocal pitch, and final height and the presence of virilizing signs were examined in 9 adult (age, 18.4 to 33.5 years) and 10 adolescent (13.6 to 17.8 years) female ACT patients. We also compared the current values with values obtained 0.9 years to 7.4 years after these subjects had undergone ACT surgery, a period during which they had shown normal androgen levels. Results Of the 19 subjects, 17 (89%) had been diagnosed with ACT before 4 years of age, 1 (5%) at 8.16 years, and 1 (5%) at 10.75 years. Androgen exposure (2 to 30 months) was sufficiently strong to cause pubic hair growth in all subjects and clitoromegaly in 74% (14/19) of the subjects, but did not reduce their height from the target value. Although androgen exposure induced a remarkable reduction in F0 (132 Hz) and moderate pitch virilization in 1 subject and partial F0 virilization, resulting in F0 of 165 and 169 Hz, in 2 subjects, the majority had normal F0 ranging from 189 to 245 Hz. Conclusions Female laryngeal tissue is less sensitive to androgen exposure between birth and adrenarche than during other periods. Differential larynx sensitivity to androgen exposure in childhood and F0 irreversibility in adulthood are age-, concentration-, duration-, and timing-dependent events that may also be affected by exposure to inhibitory or stimulatory hormones. Further studies are required to better characterize each of these factors. PMID:23284635

Setting Up a Patient Care Call Center After Potential HCV Exposure.

PubMed

Friedman, Candace; Bucholz, Brigette; Anderson, Susan G; Dwyer, Shon A; Aguirre, Josephine

2016-09-01

Notify patients of a potential exposure to hepatitis C virus, coordinate testing, and provide follow-up counseling. A team was convened to identify various needs in developing a patient care call center. The areas addressed included the following: location, hours, and duration; telephone accessibility; tracking calls and test results; billing; staffing; notification; and potential issues requiring additional evaluation. Disclosure letters were sent to 1275 patients; 57 letters were not deliverable. There were 245 calls to the helpline from October 25 through November 15. Lessons learned centered on hours of availability, staffing, use of an automated phone system and email communication, tracking results, and billing issues. A successful patient notification and follow-up effort requires a multidisciplinary team, internal and external communication, collection of data over an extended period, and coordination of patient information.

Stress response in rat brain after different durations of noise exposure.

PubMed

Samson, James; Sheeladevi, Rathinasamy; Ravindran, Rajan; Senthilvelan, Manohar

2007-01-01

The alteration in the levels of plasma corticosterone, brain norepinephrine (NE), and expression of brain heat shock proteins (Hsp70) after different durations of noise exposure (acute, 1 day; sub-acute, 15 days; chronic, 30 days) has been studied to analyze their role in combating time-dependent stress effects of noise. Broadband white noise (100dB) exposure to male Wistar albino rats significantly increased the levels of plasma corticosterone and NE in all three durations of noise exposure. The sustained increase observed in their levels in the chronic group suggests that animals are not getting adapted to noise even after 30 days of exposure. The important role of Hsp70 in combating noise induced stress is evident from the significant increase in its expression after chronic exposure, while there was a reciprocal decrease in the NE and corticosterone when compared with their levels after acute and sub-acute noise exposure. This clearly indicates that the time-dependent stress response to noise exposure is a complex mechanism involving highly interconnected systems such as hypothalamo-pituitary-adrenal (HPA) axis, heat shock proteins and may have serious implications in vital organs, particularly in the brain when there is a prolonged noise exposure.

Considerations for an exercise prescription

NASA Technical Reports Server (NTRS)

Convertino, Victor A.

1989-01-01

A number of past and most recent research findings that describe some of the physiological responses to exercise in man and their relationship with exposure to various gravitational environments are discussed. Most of the data pertain to adaptations of the cardiovascular and body fluid systems. It should be kept in mind that the data from studies on microgravity simulation in man include exposures of relatively short duration (5 hours to 14 days). However, it is argued that the results may provide important guidelines for the consideration of many variables which are pertinent to the development of exercise prescription for long-duration space flight. The following considerations for exercise prescriptions during long-duration space flight are noted: (1) Relatively high aerobic fitness and strength, especially of the upper body musculature, should be a criterion for selection of astronauts who will be involved in EVA, since endurance and strength appear to be predominant characteristics for work performance. (2) Some degree of upper body strength will probably be required for effective performance of EVA. However, the endurance and strength required by the upper body for EVA can probably be obtained through preflight exercise prescription which involves swimming. (3) Although some degree of arm exercise may be required to maintain preflight endurance and strength, researchers propose that regular EVA will probably be sufficient to maintain the endurance and strength required to effectively perform work tasks during space flight. (4) A minimum of one maximal aerobic exercise every 7 to 10 days during space flight may be all that is necessary for maintenance of normal cardiovascular responsiveness and replacement of body fluids for reentry following prolonged space flight. (5) The possible reduction in the amount of exercise required for maintenance of cardiovascular system and body fluids in combination with the use of electromyostimulation (EMS) or methods other than conventional exercise for maintaining size and strength of muscles and bones needs great consideration for further research. These approaches represent a potential solution to the problem of compromising valuable time for exercise that is needed for daily operations.

Predictors of radiation exposure to providers during percutaneous nephrolithotomy

PubMed Central

Wenzler, David L.; Abbott, Joel E.; Su, Jeannie J.; Shi, William; Slater, Richard; Miller, Daniel; Siemens, Michelle J.; Sur, Roger L.

2017-01-01

Background: Limited studies have reported on radiation risks of increased ionizing radiation exposure to medical personnel in the urologic community. Fluoroscopy is readily used in many urologic surgical procedures. The aim of this study was to determine radiation exposure to all operating room personnel during percutaneous nephrolithotomy (PNL), commonly performed for large renal or complex stones. Materials and Methods: We prospectively collected personnel exposure data for all PNL cases at two academic institutions. This was collected using the Instadose™ dosimeter and reported both continuously and categorically as high and low dose using a 10 mrem dose threshold, the approximate amount of radiation received from one single chest X-ray. Predictors of increased radiation exposure were determined using multivariate analysis. Results: A total of 91 PNL cases in 66 patients were reviewed. Median surgery duration and fluoroscopy time were 142 (38–368) min and 263 (19–1809) sec, respectively. Median attending urologist, urology resident, anesthesia, and nurse radiation exposure per case was 4 (0–111), 4 (0–21), 0 (0–5), and 0 (0–5) mrem, respectively. On univariate analysis, stone area, partial or staghorn calculi, surgery duration, and fluoroscopy time were associated with high attending urologist and resident radiation exposure. Preexisting access that was utilized was negatively associated with resident radiation exposure. However, on multivariate analysis, only fluoroscopy duration remained significant for attending urologist radiation exposure. Conclusion: Increased stone burden, partial or staghorn calculi, surgery and fluoroscopy duration, and absence of preexisting access were associated with high provider radiation exposure. Radiation safety awareness is essential to minimize exposure and to protect the patient and all providers from potential radiation injury. PMID:28216931

Space flight rehabilitation.

PubMed

Payne, Michael W C; Williams, David R; Trudel, Guy

2007-07-01

The weightless environment of space imposes specific physiologic adaptations on healthy astronauts. On return to Earth, these adaptations manifest as physical impairments that necessitate a period of rehabilitation. Physiologic changes result from unloading in microgravity and highly correlate with those seen in relatively immobile terrestrial patient populations such as spinal cord, geriatric, or deconditioned bed-rest patients. Major postflight impairments requiring rehabilitation intervention include orthostatic intolerance, bone demineralization, muscular atrophy, and neurovestibular symptoms. Space agencies are preparing for extended-duration missions, including colonization of the moon and interplanetary exploration of Mars. These longer-duration flights will result in more severe and more prolonged disability, potentially beyond the point of safe return to Earth. This paper will review and discuss existing space rehabilitation plans for major postflight impairments. Evidence-based rehabilitation interventions are imperative not only to facilitate return to Earth but also to extend the safe duration of exposure to a physiologically hostile microgravity environment.

Peak expiratory flow rate in handloom weavers.

PubMed

Tiwari, R R; Zodpey, S P; Deshpande, S G; Vasudeo, N D

1998-04-01

The present cross-sectional study with a comparison group was carried out to investigate peak expiratory flow rate (PEFR) in handloom weavers and to study relationship between reduction in PEFR with age, smoking, duration of cotton dust exposure and respiratory morbidity. This study include 319 handloom weavers and equal number of individuals (group matched for age and pair matched for sex) in comparison group. The decline in PEFR was significantly associated with advancing age, longer duration of exposure to cotton dust, tobacco smoking and presence of respiratory morbidity on univariate analysis, whereas on multivariate analysis longer duration of exposure to cotton dust and tobacco smoking was found to be non significant.

Evaluation of seals and lubricants used on the Long Duration Exposure Facility

NASA Technical Reports Server (NTRS)

Dursch, H. W.; Keough, B. K.; Pippin, H. G.

1994-01-01

This report described results from testing and analysis of seals and lubricants subsequent to the 69-month low-earth-orbit (LEO) exposure on the Long Duration Exposure Facility (LDEF). Results show that if the materials were shielded from exposure to LDEF's external environment, the 69-month exposure to LEO resulted in minimal changes to material properties. However, if the materials were exposed to LDEF's exterior environments (atomic oxygen, solar radiation, meteoroids, and/or space debris), a variety of events occurred, ranging from no material change, to changes in properties, to significant erosion of the material.

[Objectivized evaluation of surgeons exposure to radiofrequency electromagnetic fields -- in the context of exposure duration and Polish and new international requirements regarding workers protection].

PubMed

Karpowicz, Jolanta; Gryz, Krzysztof; Leszko, Wieslaw; Zradziński, Patryk

2013-01-01

Use of electro surgery units (ESU) in surgeries is linked with electromagnetic field emission, which is assessed according to the requirements of occupational health and safety legislation. Surgeons' exposure characteristics was monitored during 11 surgeries (proctectomy, patency of artery, hepatectomy, cystectomy, tonsilectomy, laparoscopy) by real time of monopolar ESU activity recorder. Investigations of root-mean-square value of electric and magnetic field strength was also performed at various modes of ESU operations during cutting (output power, 55-150 W; frequency, 330-445 kHz) and coagulating (40-240 W, 335-770 kHz). Statistical parameters of distribution of ESU operation over any 6-min periods (according to international requirements regarding protection against adverse thermal effects of electromagnetic field) were assessed. Electric field strength, measured 10 cm from the cable supplying an active electrode was 147-675 V/m during cutting and 297-558 V/m during coagulating; magnetic field strength was less than 0.2 A/m in both modes. Monitoring of ESUs showed the following ranges of their operation during surgeries 5-66% of time over starting 3 min of surgery, 3-40% over starting 6 min, and the distribution of their use over any 6-min periods 0-12% (median) / 7-43% (maximum value). The real operation time of ESUs ing surgeries was significantly shorter than that declared by workers. The distance of at least 15 cm between cables, connecting electrodes with generator and workers meets the requirements of the Polish legislation on permissible exposure limits. The assessment of localized exposure of the hand needs a detailed analysis of the SAR ratio distribution and further studies are required.

Human health and performance considerations for near earth asteroids (NEA)

NASA Astrophysics Data System (ADS)

Steinberg, Susan; Kundrot, Craig; Charles, John

2013-11-01

Humans are considered as a system in the design of any deep space exploration mission. The addition of many potential near asteroid (NEA) destinations to the existing multiple mission architecture for Lunar and Mars missions increases the complexity of human health and performance issues that are anticipated for exploration of space. We suggest that risks to human health and performance be analyzed in terms of the 4 major parameters related to multiple mission architecture: destination, duration, distance and vehicle design. Geological properties of the NEA will influence design of exploration tasks related to sample handling and containment, and extravehicular activity (EVA) capabilities including suit ports and tools. A robotic precursor mission that collects basic information on NEA surface properties would reduce uncertainty about these aspects of the mission as well as aid in mission architecture and exploration task design. Key mission parameters are strongly impacted by duration and distance. The most critical of these is deep-space radiation exposure without even the temporary shielding of a nearby large planetary body. The current space radiation permissible exposure limits (PEL) limits mission duration to 3-10 months depending on age, gender and stage of the solar cycle. Duration also impacts mission architectures including countermeasures for bone, muscle, and cardiovascular atrophy during continuous weightlessness; and behavioral and psychological issues resulting from isolation and confinement. Distance affects communications and limits abort and return options for a NEA mission. These factors are anticipated to have important effects on crew function and autonomous operations, as well as influence medical capability, supplies and training requirements of the crew. The design of a habitat volume that can maintain the physical and psychological health of the crew and support mission operations with limited intervention from earth will require an integrated research and development effort between NASA's Human Research Program (HRP), engineering and human factors groups. Packaging food to extend shelf life and waste management will be important components of vehicle subsystem design.

Sunlight Exposure, Work Hours, Caffeine Consumption, and Sleep Duration in the Naval Environment.

PubMed

Shattuck, Nita L; Matsangas, Panagiotis

2017-06-01

Sailors in the U.S. Navy are habitual shiftworkers, often experiencing circadian misalignment due to their irregular work/rest schedules. This study assessed the effect of sunlight exposure, work hours, and caffeinated beverage consumption on the daily sleep duration of crewmembers of a U.S. Navy ship during a 2-wk underway period. Working in an artificially lit area with no access to sunlight during work hours, U.S. Navy crew members (N = 91) used daily logs to report their daily activity, caffeinated beverage consumption, and exposure to sunlight while off-duty; sleep was assessed by wrist-worn actigraphy. Hours of sunlight exposure, work duration, and the amount of coffee/tea/soft drinks were statistically significant predictors of sleep duration. On average, crewmembers who reported more than one half-hour of sunlight each day slept on average ∼40 min (10%) less than their peers working the same shifts who received less than one half-hour of sunlight (on average 6.05 ± 0.90 h vs. 6.71 ± 0.91 h, respectively). Exposure to sunlight, work hours, and consumption of caffeinated beverages are important factors when planning watchstanding schedules at sea. Even though further research is needed, our results suggest that even brief exposure to sunlight may contribute to circadian misalignment that negatively affects sleep in the operational environment. Educating crewmembers about sleep hygiene, especially the important roles played by sunlight and caffeine, could potentially improve the sleep and fatigue levels of this population of maritime shiftworkers.Shattuck NL, Matsangas P. Sunlight exposure, work hours, caffeine consumption, and sleep duration in the naval environment. Aerosp Med Hum Perform. 2017; 88(6):579-585.

Light energy attenuation through orthodontic ceramic brackets at different irradiation times.

PubMed

Santini, Ario; Tiu, Szu Hui; McGuinness, Niall J P; Aldossary, Mohammed Saeed

2016-09-01

To evaluate the total light energy (TLE) transmission through three types of ceramic brackets with, bracket alone and with the addition of orthodontic adhesive, at different exposure durations, and to compare the microhardness of the cured adhesive. Three different makes of ceramic brackets, Pure Sapphire(M), Clarity™ ADVANCED(P) and Dual Ceramic(P) were used. Eighteen specimens of each make were prepared and allocated to three groups (n = 6). MARC(®)-resin calibrator was used to determine the light curing unit (LCU) tip irradiance (mW/cm(2)) and TLE (J/cm(2)) transmitted through the ceramic brackets, and through ceramic bracket plus Transbond™ XT Light Cure Adhesive, for 5, 10 and 20 s. Vickers-hardness values at the bottom of the cured adhesive were determined. Statistical analysis used one-way analysis of variance (ANOVA); P = 0.05. TLE transmission rose significantly among all samples with increasing exposure durations. TLE reaching the adhesive- enamel interface was less than 10 J/cm(2), and through monocrystalline and polycrystalline ceramic brackets was significantly different (P < 0.05). Pure Sapphire(M) showed the highest amount of TLE transmission and Vickers-hardness values for 5, 10 and 20 s. Following manufacturer's recommendations, insufficient TLE may be delivered to the adhesive: increasing the exposure durations may be required when adhesive is cured through ceramic brackets. Clinicians are advised to measure the tip irradiance of their LCUs and increase curing time beyond 5 s. Orthodontic clinicians should understand the type of light curing device and the orthodontic adhesive used in their practice.

NIOSH testimony to DOL on the Occupational Safety And Health Administration's proposed rule on occupational exposure to asbestos, tremolite, anthophyllite, and actinolite by J. D. Millar, January 24, 1991

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1991-01-24

The testimony contains the comments of NIOSH regarding the proposed rule on occupational exposure to asbestos (1332214), tremolite (14567738), anthophyllite (17068789) and actinolite (77536664) exposures. NIOSH supports OSHA in proposing changes to the existing asbestos standard to minimize the risk of asbestos related diseases in workers. The current standard is insufficient to protect the health of workers exposed to asbestos, and the proposed changes represent a prudent and necessary approach to accomplish this goal. Specific topics addressed in the testimony include exposure limits for asbestos; methods for sampling and analysis of airborne fibers; use of time weighted averages to measuremore » exposure; use of engineering controls, good work practices and personal protective equipment; use of engineering controls and work practices for brake and clutch repair and service; required use of specific work practices during maintenance of vinyl asbestos floor tile; housekeeping; definitions of small scale and short duration operations; exemption of roofing operations from the requirement for negative pressure enclosures; communication among employers and owners; regulated areas for asbestos removal, maintenance, demolition, and renovation operations; use of glove bags; definition of competent person; and notification to OSHA and method of notification.« less

Dose conversion factors for radon: recent developments.

PubMed

Marsh, James W; Harrison, John D; Laurier, Dominique; Blanchardon, Eric; Paquet, François; Tirmarche, Margot

2010-10-01

Epidemiological studies of the occupational exposure of miners and domestic exposures of the public have provided strong and complementary evidence of the risks of lung cancer following inhalation of radon progeny. Recent miner epidemiological studies, which include low levels of exposure, long duration of follow-up, and good quality of individual exposure data, suggest higher risks of lung cancer per unit exposure than assumed previously by the International Commission on Radiological Protection (ICRP). Although risks can be managed by controlling exposures, dose estimates are required for the control of occupational exposures and are also useful for comparing sources of public exposure. Currently, ICRP calculates doses from radon and its progeny using dose conversion factors from exposure (WLM) to dose (mSv) based on miner epidemiological studies, referred to as the epidemiological approach. Revision of these dose conversion factors using risk estimates based on the most recent epidemiological data gives values that are in good agreement with the results of calculations using ICRP biokinetic and dosimetric models, the dosimetric approach. ICRP now proposes to treat radon progeny in the same way as other radionuclides and to publish dose coefficients calculated using models, for use within the ICRP system of protection.

Duration as a measure of the spiral aftereffect.

DOT National Transportation Integrated Search

1963-01-01

Describes an experiment that studied the reliability of duration as a measure of the spiral aftereffect. The results for 10 Ss indicate that duration is a highly reliable measure and that duration is a simple monotonic function of exposure-time.

Energetic requirements of green sturgeon (Acipenser medirostris) feeding on burrowing shrimp (Neotrypaea californiensis) in estuaries: importance of temperature, reproductive investment, and residence time

USGS Publications Warehouse

Borin, Joshua M.; Moser, Mary L.; Hansen, Adam G.; Beauchamp, David A.; Corbett, Stephen C.; Dumbauld, Brett R.; Pruitt, Casey; Ruesink, Jennifer L.; Donoghue, Cinde

2017-01-01

Habitat use can be complex, as tradeoffs among physiology, resource abundance, and predator avoidance affect the suitability of different environments for different species. Green sturgeon (Acipenser medirostris), an imperiled species along the west coast of North America, undertake extensive coastal migrations and occupy estuaries during the summer and early fall. Warm water and abundant prey in estuaries may afford a growth opportunity. We applied a bioenergetics model to investigate how variation in estuarine temperature, spawning frequency, and duration of estuarine residence affect consumption and growth potential for individual green sturgeon. We assumed that green sturgeon achieve observed annual growth by feeding solely in conditions represented by Willapa Bay, Washington, an estuary annually frequented by green sturgeon and containing extensive tidal flats that harbor a major prey source (burrowing shrimp, Neotrypaea californiensis). Modeled consumption rates increased little with reproductive investment (<0.4%), but responded strongly (10–50%) to water temperature and duration of residence, as higher temperatures and longer residence required greater consumption to achieve equivalent growth. Accordingly, although green sturgeon occupy Willapa Bay from May through September, acoustically-tagged individuals are observed over much shorter durations (34 d + 41 d SD, N = 89). Simulations of <34 d estuarine residence required unrealistically high consumption rates to achieve observed growth, whereas longer durations required sustained feeding, and therefore higher total intake, to compensate for prolonged exposure to warm temperatures. Model results provide a range of per capita consumption rates by green sturgeon feeding in estuaries to inform management decisions regarding resource and habitat protection for this protected species.

Clinical trial considerations on male contraception and collection of pregnancy information from female partner: update.

PubMed

Banholzer, Maria Longauer; Wandel, Christoph; Barrow, Paul; Mannino, Marie; Schmitt, Georg; Guérard, Melanie; Müller, Lutz; Greig, Gerard; Amemiya, Kenjie; Peck, Richard; Singer, Thomas; Doessegger, Lucette

2016-12-01

This is an update to our 2012 publication on clinical trial considerations on male contraception and collection of pregnancy information from female partner, after critical review of recent (draft) guidances released by the International Council for Harmonisation [ICH] the Clinical Trial Facilitation Group [CTFG] and the US Food & Drug Administration [FDA]. Relevant aspects of the new guidance documents are discussed in the context of male contraception and pregnancy reporting from female partner in clinical trials and the approach is updated accordingly. Genotoxicity The concept of a threshold is introduced using acceptable daily intake/permissible daily exposure to define genotoxicity requirements, hence highly effective contraception in order to avoid conception. The duration for highly effective contraception has been extended from 74 to 90 days from the end of relevant systemic exposure. Teratogenicity Pharmacokinetic considerations to estimate safety margins have been contextualized with regard to over- and underestimation of the risk of teratogenicity transmitted by a vaginal dose. The duration of male contraception after the last dose takes into account the end of relevant systemic exposure if measured, or a default period of five half-lives after last dose for small molecules and two half-lives for immunoglobulins (mAbs). Measures to prevent exposure of the conceptus via a vaginal dose apply to reproductively competent or vasectomized men, unless measurements fail to detect the compound in seminal fluid. Critical review of new guidance documents provides a comparison across approaches and resulted in an update of our previous publication. Separate algorithms for small molecules and monoclonal antibodies are proposed to guide the recommendations for contraception for male trial participants and pregnancy reporting from female partners. No male contraception is required if the dose is below a defined threshold for genotoxic concern applicable to small molecules. For men treated with teratogenic mAbs, condom use to prevent exposure of a potentially pregnant partner is unlikely to be recommended because of the minimal female exposure anticipated following a vaginal dose. The proposed safety margins for teratogenicity may evolve with further knowledge.

Translation of Toxicity Data into CW Agent Toxicity Estimates

DTIC Science & Technology

2003-07-01

UNLIMITED UNCLASSIFIED/UNLIMITEDPrepared by Douglas R. Sommerville, PE US Army ECBC, APG, MD Dependence of Toxic Effect on Exposure Time Inhalation (IH...to longer exposure durations. Toxicity estimates for exposure durations ranging from 2 to 360 minutes have been derived for six agents (GA, GB, GD...individuals having effects greater in severity than the defining effect of the ECTYY Cn T = k Toxic load equation 5 6 Edgewood Chemical Biological Center

The confidence-accuracy relationship for eyewitness identification decisions: Effects of exposure duration, retention interval, and divided attention.

PubMed

Palmer, Matthew A; Brewer, Neil; Weber, Nathan; Nagesh, Ambika

2013-03-01

Prior research points to a meaningful confidence-accuracy (CA) relationship for positive identification decisions. However, there are theoretical grounds for expecting that different aspects of the CA relationship (calibration, resolution, and over/underconfidence) might be undermined in some circumstances. This research investigated whether the CA relationship for eyewitness identification decisions is affected by three, forensically relevant variables: exposure duration, retention interval, and divided attention at encoding. In Study 1 (N = 986), a field experiment, we examined the effects of exposure duration (5 s vs. 90 s) and retention interval (immediate testing vs. a 1-week delay) on the CA relationship. In Study 2 (N = 502), we examined the effects of attention during encoding on the CA relationship by reanalyzing data from a laboratory experiment in which participants viewed a stimulus video under full or divided attention conditions and then attempted to identify two targets from separate lineups. Across both studies, all three manipulations affected identification accuracy. The central analyses concerned the CA relation for positive identification decisions. For the manipulations of exposure duration and retention interval, overconfidence was greater in the more difficult conditions (shorter exposure; delayed testing) than the easier conditions. Only the exposure duration manipulation influenced resolution (which was better for 5 s than 90 s), and only the retention interval manipulation affected calibration (which was better for immediate testing than delayed testing). In all experimental conditions, accuracy and diagnosticity increased with confidence, particularly at the upper end of the confidence scale. Implications for theory and forensic settings are discussed.

A Launch Requirements Trade Study for Active Space Radiation Shielding for Long Duration Human Missions

NASA Technical Reports Server (NTRS)

Singleterry, Robert C., Jr.; Bollweg, Ken; Martin, Trent; Westover, Shayne; Battiston, Roberto; Burger, William J.; Meinke, Rainer

2015-01-01

A trade study for an active shielding concept based on magnetic fields in a solenoid configuration versus mass based shielding was developed. Monte Carlo simulations were used to estimate the radiation exposure for two values of the magnetic field strength and the mass of the magnetic shield configuration. For each field strength, results were reported for the magnetic region shielding (end caps ignored) and total region shielding (end caps included but no magnetic field protection) configurations. A value of 15 cSv was chosen to be the maximum exposure for an astronaut. The radiation dose estimate over the total shield region configuration cannot be used at this time without a better understanding of the material and mass present in the end cap regions through a detailed vehicle design. The magnetic shield region configuration, assuming the end cap regions contribute zero exposure, can be launched on a single Space Launch System rocket and up to a two year mission can be supported. The magnetic shield region configuration results in two versus nine launches for a comparable mass based shielding configuration. The active shielding approach is clearly more mass efficient because of the reduced number of launches than the mass based shielding for long duration missions.

Radiation Transport Modeling and Assessment to Better Predict Radiation Exposure, Dose, and Toxicological Effects to Human Organs on Long Duration Space Flights

NASA Technical Reports Server (NTRS)

Denkins, Pamela; Badhwar, Gautam; Obot, Victor

2000-01-01

NASA's long-range plans include possible human exploratory missions to the moon and Mars within the next quarter century. Such missions beyond low Earth orbit will expose crews to transient radiation from solar particle events which include high-energy galactic cosmic rays and high-energy protons. Because the radiation levels in space are high and the missions long, adequate shielding is needed to minimize the deleterious health effects of exposure to radiation. The focus of this study is radiation exposure to the blood-forming organs of the NASA astronauts. NASA/JSC developed the Phantom Torso Experiment for Organ Dose Measurements which housed active and passive dosimeters that would monitor and record absorbed radiation levels at vital organ locations. This experiment was conducted during the STS-9 I mission in May '98 and provided the necessary space radiation data for correlation to results obtained from the current analytical models used to predict exposure to the blood-forming organs. Numerous models (i.e., BRYNTRN and HZETRN) have been developed and used to predict radiation exposure. However, new models are continually being developed and evaluated. The Space Environment Information Systems (SPENVIS) modeling program, developed by the Belgian Institute for Space Aeronomy, is to be used and evaluated as a part of the research activity. It is the intent of this research effort to compare the modeled data to the findings from the STS-9 I mission; assess the accuracy and efficiency of this model; and to determine its usefulness for predicting radiation exposure and developing better guidelines for shielding requirements for long duration manned missions.

[Exposure to static magnetic field and health hazards during the operation of magnetic resonance scanners].

PubMed

Karpowicz, Jolanta; Gryz, Krzysztof; Politański, Piotr; Zmyślony, Marek

2011-01-01

Magnetic resonance imaging (MRI) scanners belong to the most modern imaging diagnostic devices, which involve workers' exposure to static magnetic fields (SMF) during the preparation and performance of MRI examinations. This paper presents the data on workers' exposure to SMF in the vicinity of MRI scanners and the analysis of SMF-related biological effects and health hazards to find out whether softening the legislative requirements concerning protection against SMF exposure of workers involved in MRI diagnostics is justified. Measurements in the vicinity of 1.5 T MRI magnets showed that exposure to SMF by various scanners depends on both SMF of magnets and scanners design, as well as on work organization. In a routine examination of one patient the radiographer is exposed to SMF exceeding 0.5 mT for app. 1.5-7 min, and up to 1.3 min to SMF exceeding 70 mT. In examinations of patients who need more attention, the duration of exposure may be significantly longer. The mean values (B mean) of exposure to SMF are 5.6-85 mT (mean 30 +/- 19 mT, N = 16). These data demonstrate that only well designed procedures, proper organization of workplace and awareness of workers how to attend the patients without being exposed to strong SMF allow for meeting the requirements of labor law concerning workers' exposure to SMF. The analysis of the available literature on biological effects of SMF has disclosed the lack of data on health effects of many years exposure of workers and the abundance of data demonstrating the biological activity of SMF. Therefore, a radical softening of legislative requirements concerning the exposure of workers' head or trunk is premature, and what is more, it is not indispensable for the development of MRI diagnostic. Such an action should be preceded by extensive international investigations on the health status of workers exposed to electromagnetic fields by MRI scanners.

Opportunities for nutritional amelioration of radiation-induced cellular damage

NASA Technical Reports Server (NTRS)

Turner, Nancy D.; Braby, Leslie A.; Ford, John; Lupton, Joanne R.

2002-01-01

The closed environment and limited evasive capabilities inherent in space flight cause astronauts to be exposed to many potential harmful agents (chemical contaminants in the environment and cosmic radiation exposure). Current power systems used to achieve space flight are prohibitively expensive for supporting the weight requirements to fully shield astronauts from cosmic radiation. Therefore, radiation poses a major, currently unresolvable risk for astronauts, especially for long-duration space flights. The major detrimental radiation effects that are of primary concern for long-duration space flights are damage to the lens of the eye, damage to the immune system, damage to the central nervous system, and cancer. In addition to the direct damage to biological molecules in cells, radiation exposure induces oxidative damage. Many natural antioxidants, whether consumed before or after radiation exposure, are able to confer some level of radioprotection. In addition to achieving beneficial effects from long-known antioxidants such as vitamins E and C and folic acid, some protection is conferred by several recently discovered antioxidant molecules, such as flavonoids, epigallocatechin, and other polyphenols. Somewhat counterintuitive is the protection provided by diets containing elevated levels of omega-3 polyunsaturated fatty acids, considering they are thought to be prone to peroxidation. Even with the information we have at our disposal, it will be difficult to predict the types of dietary modifications that can best reduce the risk of radiation exposure to astronauts, those living on Earth, or those enduring diagnostic or therapeutic radiation exposure. Much more work must be done in humans, whether on Earth or, preferably, in space, before we are able to make concrete recommendations.

What is the role of tobacco control advertising intensity and duration in reducing adolescent smoking prevalence? Findings from 16 years of tobacco control mass media advertising in Australia.

PubMed

White, Victoria M; Durkin, Sarah J; Coomber, Kerri; Wakefield, Melanie A

2015-03-01

To examine how the intensity and duration of tobacco control advertising relate to adolescent smoking prevalence. Australian students (aged 12-17 years) participating in a national survey conducted triennially between 1993 and 2008 (sample size range 12 314-16 611). The outcome measure was students' smoking in the previous 4 weeks collected through anonymous, self-completed surveys. For each student, monthly targeted rating points (TRPs, a measure of television advertising exposure) for tobacco control advertising was calculated for the 3 and 12 months prior to surveying. For each time period, cumulative TRPs exposure and exposure to three intensity levels (≥100 TRPs/month; ≥400 TRPs/month; ≥800 TRPs/month) over increasing durations (eg, 1 month, 2 months, etc) were calculated. Logistic regression examined associations between TRPs and adolescent smoking after controlling for demographic and policy variables. Past 3-month cumulative TRPs were found to have an inverse relationship with smoking prevalence. Low TRPs exposure in the past 12 months was positively associated with adolescent smoking prevalence. However, smoking prevalence reduced with cumulative exposure levels above 5800 cumulative TRPs. Additionally, exposure to ≥400 TRPs/month and ≥800 TRPs/month were associated with reduced likelihood of smoking, although the duration needed for this effect differed for the two intensity levels. When intensity was ≥400 TRPs/month, the odds of smoking only reduced with continuous exposure. When intensity was ≥800 TRPs/month, exposure at levels less than monthly was associated with reductions in smoking prevalence. Both antismoking advertising intensity and duration are important for ensuring reductions in adolescent smoking prevalence. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Considerations for development of countermeasures for physiological decrements associated with long-duration space missions

NASA Astrophysics Data System (ADS)

Sawin, Charles F.; Hayes, Judith; Francisco, David R.; House, Nancy

2007-02-01

Countermeasures are necessary to offset or minimize the deleterious changes in human physiology resulting from long duration space flight. Exposure to microgravity alters musculoskeletal, neurosensory, and cardiovascular systems with resulting deconditioning that may compromise crew health and performance. Maintaining health and fitness at acceptable levels is critical for preserving performance capabilities required to accomplish specific mission tasks (e.g.—extravehicular activity) and to optimize performance after landing. To enable the goals of the exploration program, NASA is developing a new suite of exercise hardware such as the improved loading device, the SchRED. This presentation will update the status of current countermeasures, correlate hardware advances with improvements in exercise countermeasures, and discuss future activities for safe and productive exploration missions.

Retrospective assessment of solvent exposure in paint manufacturing.

PubMed Central

Glass, D C; Spurgeon, A; Calvert, I A; Clark, J L; Harrington, J M

1994-01-01

This paper describes how exposure to solvents at two large paint making sites was assessed in a study carried out to investigate the possibility of neuropsychological effects resulting from long term exposure to organic solvents. A job exposure matrix was constructed by buildings and year. A detailed plant history was taken and this was used to identify uniform exposure periods during which workers' exposure to solvents was not thought to have changed significantly. Exposure monitoring data, collected by the company before the study, was then used to characterise exposure within each uniform exposure period. Estimates were made for periods during which no air monitoring was available. Individual detailed job histories were collected for subjects and controls. The job histories were used to estimate exposure on an individual basis with the job exposure matrix. Exposure was expressed as duration, cumulative dose, and intensity of exposure. Classification of exposure by duration alone was found to result in misclassification of subjects. PMID:7951794

Sunscreen use and intentional exposure to ultraviolet A and B radiation: a double blind randomized trial using personal dosimeters

PubMed Central

Autier, P; Doré, J-F; Reis, A C; Grivegnée, A; Ollivaud, L; Truchetet, F; Chamoun, E; Rotmensz, N; Severi, G; Césarini, J-P

2000-01-01

A previous randomized trial found that sunscreen use could extend intentional sun exposure, thereby possibly increasing the risk of cutaneous melanoma. In a similarly designed trial, we examined the effect of the use of sunscreens having different sun protection factor (SPF) on actual exposure to ultraviolet B (UVB) and ultraviolet A (UVA) radiation. In June 1998, 58 European participants 18–24 years old were randomized to receive a SPF 10 or 30 sunscreens and were asked to complete daily records of their sun exposure during their summer holidays of whom 44 utilized a personal UVA and UVB dosimeter in a standard way during their sunbathing sessions. The median daily sunbathing duration was 2.4 hours in the SPF 10 group and 3.0 hours in the SPF 30 group (P = 0.054). The increase in daily sunbathing duration was paralleled by an increase in daily UVB exposure, but not by changes in UVA or UVB accumulated over all sunbathing sessions, or in daily UVA exposure. Of all participants, those who used the SPF 30 sunscreen and had no sunburn spent the highest number of hours in sunbathing activities. Differences between the two SPF groups in total number of sunbathing hours, daily sunbathing duration, and daily UVB exposure were largest among participants without sunburn during holidays. Among those with sunburn, the differences between the two groups tended to reduce. In conclusion, sunscreens used during sunbathing tended to increase the duration of exposures to doses of ultraviolet radiation below the sunburn threshold. © 2000 Cancer Research Campaign PMID:11027441

Modified Blumlein pulse-forming networks for bioelectrical applications.

PubMed

Romeo, Stefania; Sarti, Maurizio; Scarfì, Maria Rosaria; Zeni, Luigi

2010-07-01

Intense nanosecond pulsed electric fields (nsPEFs) have been shown to induce, on intracellular structures, interesting effects dependent on electrical exposure conditions (pulse length and amplitude, repetition frequency and number of pulses), which are known in the literature as "bioelectrical effects" (Schoenbach et al., IEEE Trans Plasma Sci 30:293-300, 2002). In particular, pulses with a shorter width than the plasma membrane charging time constant (about 100 ns for mammalian cells) can penetrate the cell and trigger effects such as permeabilization of intracellular membranes, release of Ca(2+) and apoptosis induction. Moreover, the observed effects have led to exploration of medical applications, like the treatment of melanoma tumors (Nuccitelli et al., Biochem Biophys Res Commun 343:351-360, 2006). Pulsed electric fields allowing such effects usually range from several tens to a few hundred nanoseconds in duration and from a few to several tens of megavolts per meter in amplitude (Schoenbach et al., IEEE Trans Diel Elec Insul 14:1088-1109, 2007); however, the biological effects of subnanosecond pulses have been also investigated (Schoenbach et al., IEEE Trans Plasma Sci 36:414-422, 2008). The use of such a large variety of pulse parameters suggests that highly flexible pulse-generating systems, able to deliver wide ranges of pulse durations and amplitudes, are strongly required in order to explore effects and applications related to different exposure conditions. The Blumlein pulse-forming network is an often-employed circuit topology for the generation of high-voltage electric pulses with fixed pulse duration. An innovative modification to the Blumlein circuit has been recently devised which allows generation of pulses with variable amplitude, duration and polarity. Two different modified Blumlein pulse-generating systems are presented in this article, the first based on a coaxial cable configuration, matching microscopic slides as a pulse-delivery system, and the other based on microstrip transmission lines and designed to match cuvettes for the exposure of cell suspensions.

Photo from Space Shuttle Mission 41-C of the Long Duration Exposure

NASA Image and Video Library

1989-12-06

Photo from Space Shuttle Mission 41-C of the Long Duration Exposure Facility (LDEF) deploy by CHALLENGER and a Langley Research Center (LRC) supplied art concept of the LDEF recovery by COLUMBIA during Space Shuttle Mission STS-32. LRC # L-89-11-720 for JSC # S89-50779

Duration of Exposure and the Dose-Response Model of PTSD

ERIC Educational Resources Information Center

Kaysen, Debra; Rosen, Gerald; Bowman, Marilyn; Resick, Patricia A.

2010-01-01

A dose-response model underlies posttraumatic stress disorder (PTSD) and posits a relationship between event magnitude and clinical outcome. The present study examines whether one index of event magnitude--duration of exposure--contributes to risk of PTSD among female victims of sexual assault. Findings support a small but significant contribution…

The effect of theobromine 200 mg/l topical gel exposure duration against surface enamel hardness resistance from 1% citric acid

NASA Astrophysics Data System (ADS)

Herisa, H. M.; Noerdin, A.; Eriwati, Y. K.

2017-08-01

Theobromine can be used to prevent the demineralization of enamel and can stimulate the growth of new enamels. This study analyzes the effect of theobromine’s gel duration exposure on enamel hardness resistance from 1% citric acid. Twenty-eight specimens were divided into three experimental groups; were exposed to theobromine gel 200 mg/l for 16, 48, and 96 minutes; and were then immersed in 1% citric acid. The control group was only immersed in 1% citric acid. Results: A Wilcoxon test showed a significant increase and decrease in enamel microhardness after exposure to theobromine gel and citric acid (p < 0.05). A Mann-Whitney test showed a significant increase and decrease in enamel microhardness between different durations of exposure to theobromine gel and immersion in citric acid (p < 0.05). The application of theobromine gel 200mg/L increased enamel microhardness but did not contribute to the enamel’s hardness resistance after immersion in 1% citric acid. The duration of theobromine gel application affected enamel microhardness and acid resistance.

Issues on human acceleration tolerance after long-duration space flights

NASA Technical Reports Server (NTRS)

Kumar, K. Vasantha; Norfleet, William T.

1992-01-01

This report reviewed the literature on human tolerance to acceleration at 1 G and changes in tolerance after exposure to hypogravic fields. It was found that human tolerance decreased after exposure to hypokinetic and hypogravic fields, but the magnitude of such reduction ranged from 0 to 30 percent for plateau G forces and 30 to 70 percent for time tolerance on sustained G forces. A logistic regression model of the probability of individuals with 25 percent reduction in +Gz tolerance after 1 to 41 days of hypogravic exposures was constructed. The estimated values from the model showed a good correlation with the observed data. A brief review of the need for in-flight centrifuge during long-duration missions was also presented. Review of the available data showed that the use of countermeasures (such as anti-G suits, periodic acceleration, and exercise) reduced the decrement in acceleration tolerance after long-duration space flights. Areas of further research include quantification of the effect of countermeasures on tolerance, and methods to augment tolerance during and after exposures to hypogravic fields. Such data are essential for planning long-duration human missions.

Inactivation of Ichthyophonus spores using sodium hypochlorite and polyvinyl pyrrolidone iodine

USGS Publications Warehouse

Hershberger, P.K.; Pacheco, C.A.; Gregg, J.L.

2008-01-01

Chlorine and iodine solutions were effective at inactivating Ichthyophonus spores in vitro. Inactivation in sea water increased directly with halogen concentration and exposure duration, with significant differences (P < 0.05) from controls occurring at all chlorine concentrations and exposure durations tested (1.5-13.3 ppm for 1-60 min) and at most iodine concentrations and exposure durations tested (1.2 ppm for 60 min and 5.9-10.7 ppm for 1-60 min). However, 10-fold reductions in spore viability occurred only after exposure to halogen solutions at higher concentrations and/or longer durations (13 ppm total chlorine for 1-60 min, 5.9 ppm total iodine for 60 min, and 10.7 ppm total iodine for 1-60 min). Inactivation efficacy was greater when halogen solutions were prepared in fresh water, presumably because of combined effects of halogen-induced inactivation and general spore instability in fresh water. The results have practical implications for disinfection and biocontainment in research laboratories and other facilities that handle live Ichthyophonus cultures and/or infected fish.

The Cumulative Lifting Index (CULI) for the Revised NIOSH Lifting Equation: Quantifying Risk for Workers With Job Rotation.

PubMed

Garg, Arun; Kapellusch, Jay M

2016-08-01

The objectives were to: (a) develop a continuous frequency multiplier (FM) for the Revised NIOSH Lifting Equation (RNLE) as a function of lifting frequency and duration of a lifting task, and (b) describe the Cumulative Lifting Index (CULI), a methodology for estimating physical exposure to workers with job rotation. The existing FM for the RNLE (FME) does not differentiate between task duration >2 hr and <8 hr, which makes quantifying physical exposure to workers with job rotation difficult and presents challenges to job designers. Using the existing FMs for 1, 2, and 8 hr of task durations, we developed a continuous FM (FMP) that extends to 12 hr per day. We simulated 157,500 jobs consisting of two tasks each and, using different combinations of Frequency Independent Lifting Index, lifting frequency and duration of lifting. Biomechanical stresses were estimated using the CULI, time-weighted average (TWA), and peak exposure. The median difference between FME and FMP was ±1% (range: 0%-15%). Compared to CULI, TWA underestimated risk of low-back pain (LBP) for 18% to 30% of jobs, and peak exposure for an assumed 8-hr work shift overestimated risk of LBP for 20% to 25% of jobs. Peak task exposure showed 90% agreement with CULI but ignored one of two tasks. The CULI partially addressed the underestimation of physical exposure using the TWA approach and overestimation of exposure using the peak-exposure approach. The proposed FM and CULI may provide more accurate physical exposure estimates, and therefore estimated risk of LBP, for workers with job rotation. © 2016, Human Factors and Ergonomics Society.

Evidence Report: Risk of Cardiovascular Disease and Other Degenerative Tissue Effects from Radiation Exposure

NASA Technical Reports Server (NTRS)

Patel, Zarana; Huff, Janice; Saha, Janapriya; Wang, Minli; Blattnig, Steve; Wu, Honglu; Cucinotta, Francis

2015-01-01

Occupational radiation exposure from the space environment may result in non-cancer or non-CNS degenerative tissue diseases, such as cardiovascular disease, cataracts, and respiratory or digestive diseases. However, the magnitude of influence and mechanisms of action of radiation leading to these diseases are not well characterized. Radiation and synergistic effects of radiation cause DNA damage, persistent oxidative stress, chronic inflammation, and accelerated tissue aging and degeneration, which may lead to acute or chronic disease of susceptible organ tissues. In particular, cardiovascular pathologies such as atherosclerosis are of major concern following gamma-ray exposure. This provides evidence for possible degenerative tissue effects following exposures to ionizing radiation in the form of the GCR or SPEs expected during long-duration spaceflight. However, the existence of low dose thresholds and dose-rate and radiation quality effects, as well as mechanisms and major risk pathways, are not well-characterized. Degenerative disease risks are difficult to assess because multiple factors, including radiation, are believed to play a role in the etiology of the diseases. As additional evidence is pointing to lower, space-relevant thresholds for these degenerative effects, particularly for cardiovascular disease, additional research with cell and animal studies is required to quantify the magnitude of this risk, understand mechanisms, and determine if additional protection strategies are required.The NASA PEL (Permissive Exposure Limit)s for cataract and cardiovascular risks are based on existing human epidemiology data. Although animal and clinical astronaut data show a significant increase in cataracts following exposure and a reassessment of atomic bomb (A-bomb) data suggests an increase in cardiovascular disease from radiation exposure, additional research is required to fully understand and quantify these adverse outcomes at lower doses (less than 0.5 gray (SI unit for ionizing radiation dosage, i.e. one joule of radiation energy per one kilogram of matter)) to facilitate risk prediction. This risk has considerable uncertainty associated with it, and no acceptable model for projecting degenerative tissue risk is currently available. In particular, risk factors such as obesity, alcohol, and tobacco use can act as confounding factors that contribute to the large uncertainties. The PELs could be violated under certain scenarios, including following a large SPE (solar proton event) or long-term GCR (galactic cosmic ray) exposure. Specifically, for a Mars mission, the accumulated dose is sufficiently high that epidemiology data and preliminary risk estimates suggest a significant risk for cardiovascular disease. Ongoing research in this area is intended to provide the evidence base for accurate risk quantification to determine criticality for extended duration missions. Data specific to the space radiation environment must be compiled to quantify the magnitude of this risk to decrease the uncertainty in current PELs and to determine if additional protection strategies are required. New research results could lead to estimates of cumulative radiation risk from CNS and degenerative tissue diseases that, when combined with the cancer risk, may have major negative impacts on mission design, costs, schedule, and crew selection. The current report amends an earlier report (Human Research Program Requirements Document, HRP-47052, Rev. C, dated Jan 2009) in order to provide an update of evidence since 2009.

Enhanced cytotoxic effect of cisplatin using diagnostic ultrasound and microbubbles in vitro

NASA Astrophysics Data System (ADS)

Sasaki, Noboru; Nakamura, Kensuke; Murakami, Masahiro; Lim, Sue Yee; Ohta, Hiroshi; Yamasaki, Masahiro; Takiguchi, Mitsuyoshi

2012-10-01

Diagnostic ultrasound has accomplished drug and gene delivery by ultrasound targeted microbubble destruction (UTMD). However, the efficacy of delivery is still relatively low. Therefore, we optimized conditions of UTMD using diagnostic ultrasound and ultrasound contrast agent microbubbles. Canine thyroid adenocarcinoma cells were cultured in a 96-well plate. After addition of cisplatin and Sonazoid®, the plate was inverted to raise microbubbles near cells and incubated. Cells were exposed to diagnostic ultrasound using a linear probe operated in the contrast harmonic imaging mode. The center frequency was 2.5 MHz with a mechanical index of 1.33 and a frame rate of 48 frames/sec. Cytotoxic effect of cisplatin was evaluated 24h after exposure using trypan blue dye exclusion test. We optimized incubation duration, cisplatin concentration, and the relationship between microbubble concentration and exposure duration. The optimum enhancement was observed at incubation duration of 5min, cisplatin concentration of 1 μg/ml, and microbubble concentration of 2.4 × 105 microbubbles/ml. Exposure duration did not influence the enhancement at the microbubble concentration of 2.4 × 105 microbubbles/ml. Our results suggest that relative low concentrations of drug and microbubbles with short exposure duration might be sufficient for drug delivery by UTMD using diagnostic ultrasound.

Occupational asthma due to formaldehyde.

PubMed Central

Burge, P S; Harries, M G; Lam, W K; O'Brien, I M; Patchett, P A

1985-01-01

Bronchial provocation studies on 15 workers occupationally exposed to formaldehyde are described. The results show that formaldehyde exposure can cause asthmatic reactions, and suggest that these are sometimes due to hypersensitivity and sometimes to a direct irritant effect. Three workers had classical occupational asthma caused by formaldehyde fumes, which was likely to be due to hypersensitivity, with late asthmatic reactions following formaldehyde exposure. Six workers developed immediate asthmatic reactions, which were likely to be due to a direct irritant effect as the reactions were shorter in duration than those seen after soluble allergen exposure and were closely related to histamine reactivity. The breathing zone concentrations of formaldehyde required to elicit these irritant reactions (mean 4.8 mg/m3) were higher than those encountered in buildings recently insulated with urea formaldehyde foam, but within levels sometimes found in industry. Images PMID:4023975

Cohort mortality study of garment industry workers exposed to formaldehyde: update and internal comparisons.

PubMed

Meyers, Alysha R; Pinkerton, Lynne E; Hein, Misty J

2013-09-01

To further evaluate the association between formaldehyde and leukemia, we extended follow-up through 2008 for a cohort mortality study of 11,043 US formaldehyde-exposed garment workers. We computed standardized mortality ratios and standardized rate ratios stratified by year of first exposure, exposure duration, and time since first exposure. Associations between exposure duration and rates of leukemia and myeloid leukemia were further examined using Poisson regression models. Compared to the US population, myeloid leukemia mortality was elevated but overall leukemia mortality was not. In internal analyses, overall leukemia mortality increased with increasing exposure duration and this trend was statistically significant. We continue to see limited evidence of an association between formaldehyde and leukemia. However, the extended follow-up did not strengthen previously observed associations. In addition to continued epidemiologic research, we recommend further research to evaluate the biological plausibility of a causal relation between formaldehyde and leukemia. Copyright © 2013 Wiley Periodicals, Inc.

Relationship of hemoglobin to occupational exposure to motor vehicle exhaust.

PubMed

Potula, V; Hu, H

1996-01-01

To study the relationship of hemoglobin to exposure to motor vehicle exhaust. Survey. Traffic police, bus drivers, and auto-shop workers (all exposed to auto exhaust in Madras, India) and unexposed office workers. We measured levels of blood lead (by graphite furnace atomic absorption spectrophotometry), and hemoglobin. Information also was collected on age, employment duration, smoking status, alcohol ingestion, and diet type (vegetarian or nonvegetarian). Increasing exposure to motor vehicle exhaust, as reflected by job category, was significantly associated with lower levels of hemoglobin (p < 0.01). A final multivariate regression model was constructed that began with indicator variables for each job (with office workers as the reference category) and included age, duration of employment, blood lead level, alcohol ingestion, dietary type, and smoking status. After a backward-elimination procedure, employment duration as an auto-shop worker or bus driver remained as significant correlates of lower hemoglobin level and current smoking and long employment duration as significant correlates of higher hemoglobin level. Occupational exposure to automobile exhaust may be a risk factor for decreased hemoglobin level in Madras. This effect appears to be independent of blood lead level and may represent hematopoietic suppression incurred by benzene or accumulated lead burden (which is not well reflected by blood lead levels). Smoking probably increased hemoglobin level through the chronic effects of exposure to carbon monoxide. In this study, a long employment duration may have served as a proxy for better socioeconomic, and therefore, better nutritional status.

Opposite Influence of Perceptual Memory on Initial and Prolonged Perception of Sensory Ambiguity

PubMed Central

de Jong, Maartje Cathelijne; Knapen, Tomas; van Ee, Raymond

2012-01-01

Observers continually make unconscious inferences about the state of the world based on ambiguous sensory information. This process of perceptual decision-making may be optimized by learning from experience. We investigated the influence of previous perceptual experience on the interpretation of ambiguous visual information. Observers were pre-exposed to a perceptually stabilized sequence of an ambiguous structure-from-motion stimulus by means of intermittent presentation. At the subsequent re-appearance of the same ambiguous stimulus perception was initially biased toward the previously stabilized perceptual interpretation. However, prolonged viewing revealed a bias toward the alternative perceptual interpretation. The prevalence of the alternative percept during ongoing viewing was largely due to increased durations of this percept, as there was no reliable decrease in the durations of the pre-exposed percept. Moreover, the duration of the alternative percept was modulated by the specific characteristics of the pre-exposure, whereas the durations of the pre-exposed percept were not. The increase in duration of the alternative percept was larger when the pre-exposure had lasted longer and was larger after ambiguous pre-exposure than after unambiguous pre-exposure. Using a binocular rivalry stimulus we found analogous perceptual biases, while pre-exposure did not affect eye-bias. We conclude that previously perceived interpretations dominate at the onset of ambiguous sensory information, whereas alternative interpretations dominate prolonged viewing. Thus, at first instance ambiguous information seems to be judged using familiar percepts, while re-evaluation later on allows for alternative interpretations. PMID:22295095

Extinction and anti-extinction: the "attentional waiting" hypothesis.

PubMed

Watling, Rosamond; Danckert, James; Linnell, Karina J; Cocchini, Gianna

2013-03-01

Patients with visual extinction have difficulty detecting a single contralesional stimulus when a second stimulus is simultaneously presented on the ipsilesional side. The rarely reported phenomenon of visual anti-extinction describes the opposite behavior, in which patients show greater difficulty in reporting a stimulus presented in isolation than they do in reporting 2 simultaneously presented stimuli. S. J. Goodrich and R. Ward (1997, Anti-extinction following unilateral parietal damage, Cognitive Neuropsychology, Vol. 14, pp. 595-612) suggested that visual anti-extinction is the result of a task-specific mechanism in which processing of the ipsilesional stimulus facilitates responses to the contralesional stimulus; in contrast, G. W. Humphreys, M. J. Riddoch, G. Nys, and D. Heinke (2002, Transient binding by time: Neuropsychological evidence from anti-extinction, Cognitive Neuropsychology, Vol. 19, pp. 361-380) suggested that temporal binding groups contralesional and ipsilesional stimuli together at brief exposure durations. We investigated extinction and anti-extinction phenomena in 3 brain-damaged patients using an extinction paradigm in which the stimulus exposure duration was systematically manipulated. Two patients showed both extinction and anti-extinction depending on the exposure duration of stimuli. Data confirmed the crucial role of duration in modulating the effect of extinction and anti-extinction. However, contrary to Humphreys and colleagues' (2002) single case, our patients showed extinction for short and anti-extinction for long exposure durations, suggesting that different mechanisms might underlie our patients' pattern of data. We discuss a novel "attentional waiting" hypothesis, which proposes that anti-extinction may be observed in patients showing extinction if the exposure duration of stimuli is increased. PsycINFO Database Record (c) 2013 APA, all rights reserved.

Reduced Exposure to Harmful and Potentially Harmful Smoke Constituents With the Tobacco Heating System 2.1

PubMed Central

Baker, Gizelle; Magnette, John; Picavet, Patrick; Weitkunat, Rolf

2017-01-01

Introduction: Heating rather than burning tobacco reduces levels of harmful and potentially harmful constituents, and consumer products using this approach aim to reduce exposure to tobacco toxicants. The Tobacco Heating System (THS) version 2.1 has been enhanced from earlier prototypes with an improved heat control and sensorial experience and thereby user acceptance. Exposure measurements are required to determine whether it may be possible to reduce the individual health risk compared to smoking combustible cigarettes (CCs). Methods: This controlled clinical study randomly assigned 40 smokers to either a group continuing to use of their own CC brand (n = 20) or a group switching to THS 2.1 (n = 20) for 5 days. Biomarkers of exposure were measured at baseline and on day 1 through day 5. Product consumption, Human Puffing Topography, the occurrence of adverse events, and an assessment of subjective effects, such as smoking satisfaction and enjoyment of respiratory tract sensations, were also determined. Results: The group of smokers who switched to THS 2.1 adapted their puffing behavior initially through longer puff duration and more puffs. During the duration of the study, total puff volume returned to baseline levels and the mean daily product consumption increased but with similar nicotine exposure compared to baseline CC use. Biomarkers of exposure to tobacco smoke toxicants which inform product risk assessment were significantly reduced with THS use compared to the CC group. THS 2.1 users experienced less reinforcing effects with THS 2.1 than with their own cigarette brand. Conclusions: THS 2.1 is a promising alternative to smoking CCs. Notwithstanding possible use adaption through consumption or puffing behavior, the exposure to harmful smoke constituents was markedly reduced with the new heated tobacco platform. Implications: Exposure markers to harmful and potentially harmful smoke constituents were lowered with the THS 2.1. Heating tobacco instead of burning can offer a potentially lower risk of delivering nicotine compared to CCs. PMID:27613951

Underwater temporary threshold shift in pinnipeds: effects of noise level and duration.

PubMed

Kastak, David; Southall, Brandon L; Schusterman, Ronald J; Kastak, Colleen Reichmuth

2005-11-01

Behavioral psychophysical techniques were used to evaluate the residual effects of underwater noise on the hearing sensitivity of three pinnipeds: a California sea lion (Zalophus californianus), a harbor seal (Phoca vitulina), and a northern elephant seal (Mirounga angustirostris). Temporary threshold shift (TTS), defined as the difference between auditory thresholds obtained before and after noise exposure, was assessed. The subjects were exposed to octave-band noise centered at 2500 Hz at two sound pressure levels: 80 and 95 dB SL (re: auditory threshold at 2500 Hz). Noise exposure durations were 22, 25, and 50 min. Threshold shifts were assessed at 2500 and 3530 Hz. Mean threshold shifts ranged from 2.9-12.2 dB. Full recovery of auditory sensitivity occurred within 24 h of noise exposure. Control sequences, comprising sham noise exposures, did not result in significant mean threshold shifts for any subject. Threshold shift magnitudes increased with increasing noise sound exposure level (SEL) for two of the three subjects. The results underscore the importance of including sound exposure metrics (incorporating sound pressure level and exposure duration) in order to fully assess the effects of noise on marine mammal hearing.

Duration and Timing of Exposure to Neighborhood Poverty and the Risk of Adolescent Parenthood

PubMed Central

Wodtke, Geoffrey T.

2013-01-01

Theory suggests that the impact of neighborhood poverty depends on both the duration and timing of exposure. Previous research, however, does not properly analyze the sequence of neighborhoods to which children are exposed throughout the early life course. This study investigates the effects of different longitudinal patterns of exposure to disadvantaged neighborhoods on the risk of adolescent parenthood. It follows a cohort of children in the PSID from age 4 to 19 and uses novel methods for time-varying exposures that overcome critical limitations of conventional regression when selection processes are dynamic. Results indicate that sustained exposure to poor neighborhoods substantially increases the risk of becoming a teen parent and that exposure to neighborhood poverty during adolescence may be more consequential than exposure earlier during childhood. PMID:23720166

Inability to induce tympanic squamous metaplasia using organochlorine compounds in vitamin A-deficient red-eared sliders (Trachemys scripta elegans).

PubMed

Kroenlein, Karl R; Sleeman, Jonathan M; Holladay, Steven D; Joyner, Priscilla H; Brown, Justin D; Griffin, Mark; Saunders, Geoffrey; Smith, Stephen A

2008-07-01

Previously, we reported that wild eastern box turtles (Terrapene carolina carolina) with aural abscesses contained higher body burdens of organochlorine (OC) compounds than those without the lesion. This lesion in captive chelonians is associated with turtles that are fed diets deficient in vitamin A. To examine the pathophysiology of this lesion and evaluate the relationship between OC burdens and vitamin A metabolism, we maintained red-eared sliders (Trachemys scripta elegans) under different conditions of OC exposure and dietary vitamin A concentrations from August 2005 to February 2006. Dietary vitamin A concentration (0 or 5 international units/g in the diet) and OC exposure (no OC compound or the mixture of 2 mg/kg chlordane, 0.25 mg/kg aroclor, and 1 mg/kg lindane) did not affect histologic score based on degree of squamous metaplasia of the tympanic epithelium or levels of plasma or liver vitamin A among the study groups. The results of this study suggest that 6 mo of exposure to the selected OC compounds, or similar duration of reduced dietary vitamin A concentrations do not influence the formation of squamous metaplasia and aural abscesses in red-eared sliders. Further studies are required to determine whether the duration of the experiment was insufficient, the OC compounds selected were inappropriate, the dosing was incorrect, and whether there are other unknown mechanisms causing the reported association between OC exposure and aural abscesses seen in eastern box turtles.

Method for the measurement of media player use

NASA Astrophysics Data System (ADS)

Webb, Graham

There has been ongoing concern that prolonged use of MP3 players can lead to noise-induced hearing loss. Acoustic exposure is the product of intensity and duration of exposure. Previous work has utilised measurements of maximum headphone output and output during listening tests to determine acoustic intensity; whilst duration of use is currently assessed with questionnaires and interviews. The subjective nature of these latter methods has led to a wide variation in figures for device use, restricting the scope of media player risk assessment. A need was therefore identified for an improved method of acquiring data of users' listening habits. This need was addressed with the design of a new data-logging device that discretely measures voltage output from the media player, whilst in use. A calibration method is proposed to implement the headphone transfer function into the data-logger, to relate output voltage to exposed pressure. It is proposed that the headphone transfer function is measured using an acoustic manikin, representative of the population of interest. The real ear measurement is put forward as an appropriate tool for validating results gained using this approach. A data-logger was designed and a proof of concept has been demonstrated in a software program written for this purpose. The proposed method has the advantages that an objective measurement can be made of the user's natural listening habits, over a long period of time, with a resolution comparable to personal acoustic dosimetry. A number of practical steps are required to further this work before data can be collected. A software graphic equaliser was used to implement the transfer function, but the chosen filter topology gave an unsatisfactory response, an investigation is required for further work. The device requires migration to hardware and the experimental calibration and validation of the system are also required. The worldwide population of MP3 player users is in the region of hundreds of millions of people. The relationship between user and device is becoming closer and portable music technology is becoming ubiquitous, permitting extended listening durations. There is therefore a strong need to continue this field of research, to increase understanding of the risks of this aspect of recreational noise.

Can ivermectin mass treatments eliminate onchocerciasis in Africa?

PubMed Central

Winnen, M.; Plaisier, A. P.; Alley, E. S.; Nagelkerke, N. J. D.; van Oortmarssen, G.; Boatin, B. A.; Habbema, J. D. F.

2002-01-01

OBJECTIVE: To elucidate the conditions in which mass treatment with ivermectin reduces the transmission of Onchocerca volvulus sufficiently to eliminate infection from an African community. METHODS: ONCHOSIM, a microsimulation model for onchocerciasis transmission, was used to explore the implications of different treatment intervals, coverage levels and precontrol endemicities for the likelihood of elimination. FINDINGS: Simulations suggested that control strategies based exclusively on ivermectin mass treatments could eliminate onchocerciasis. The duration of treatment required to eliminate infection depended heavily on the treatment programme and precontrol endemicity. In areas with medium to high levels of infection, annual mass treatments with 65% coverage for at least 25 years were necessary. Model predictions suggested that durations exceeding 35 years would be required if there were much heterogeneity in exposure to vector bites and, consequently, wide individual variation in microfilaria counts. If the treatment interval were reduced from 12 to 6 months the time for completion of the programme could be more than halved and elimination could be accomplished in areas of hyperendemicity, provided that the effects of each treatment would be the same as with annual treatments. However, it was doubtful whether high coverage levels could be sustained long enough to achieve worldwide eradication. CONCLUSION: Elimination of onchocerciasis from most endemic foci in Africa appears to be possible. However, the requirements in terms of duration, coverage, and frequency of treatment may be prohibitive in highly endemic areas. PMID:12077614

Drosophila melanogaster (fruit fly) locomotion during a sounding rocket flight

NASA Astrophysics Data System (ADS)

Miller, Mark S.; Keller, Tony S.

2008-05-01

The locomotor activity of young Drosophila melanogaster (fruit fly) was studied during a Nike-Orion sounding rocket flight, which included a short-duration microgravity exposure. An infrared monitoring system was used to determine the activity level, instantaneous velocity, and continuous velocity of 240 (120 male, 120 female) fruit flies. Individual flies were placed in chambers that limit their motion to walking. Chambers were oriented both vertically and horizontally with respect to the rocket's longitudinal axis. Significant changes in Drosophila locomotion patterns were observed throughout the sounding rocket flight, including launch, microgravity exposure, payload re-entry, and after ocean impact. During the microgravity portion of the flight (3.8 min), large increases in all locomotion measurements for both sexes were observed, with some measurements doubling compared to pad (1 G) data. Initial effects of microgravity were probably delayed due to large accelerations from the payload despining immediately before entering microgravity. The results indicate that short-duration microgravity exposure has a large effect on locomotor activity for both males and females, at least for a short period of time. The locomotion increases may explain the increased male aging observed during long-duration exposure to microgravity. Studies focusing on long-duration microgravity exposure are needed to confirm these findings, and the relationship of increased aging and locomotion.

Effects of Oral Exposure Duration and Gastric Energy Content on Appetite Ratings and Energy Intake in Lean Men

PubMed Central

Wijlens, Anne G. M.; de Graaf, Cees; Erkner, Alfrun; Mars, Monica

2016-01-01

Studies show that longer oral exposure to food leads to earlier satiation and lowers energy intake. Moreover, higher energy content of food has been shown to lead to higher satiety. Up to now, it has not been studied systematically how oral exposure duration and gastric energy content interact in satiety regulation. Thirty-seven men (22 ± 4 years, 22 ± 2 kg/m2) participated in a randomized cross-over trial, in which we independently manipulated: (1) oral exposure duration by modified sham feeding (MSF) for 1 or 8 min; and (2) energy content of gastric load (GL) by a nasogastric tube: 100 kcal/500 mL or 700 kcal/500 mL. Outcome measures were appetite ratings and subsequent energy intake from an ad libitum meal. Energy intake was 35% lower after the GLs with 700 kcal than with 100kcal (p < 0.0001). All appetite ratings were lower in the 700 kcal than in the 100 kcal treatments (area under the curve (AUC); p-values ≤ 0.002); fullness was higher and prospective consumption was lower in the 8 min than in the 1 min MSF treatments (AUC; p-values ≤ 0.02). In conclusion, the current showed that a GL of 700 kcal/500 mL vs. 100 kcal/500 mL increased satiety and lowered energy intake. No additional effects of oral exposure duration could be observed, presumably due to the high contrast in energy between the manipulations. Future research should also focus on the role of oral exposure as such and not only the duration. PMID:26821045

The Limited Impact of Exposure Duration on Holistic Word Processing.

PubMed

Chen, Changming; Abbasi, Najam Ul Hasan; Song, Shuang; Chen, Jie; Li, Hong

2016-01-01

The current study explored the impact of stimuli exposure duration on holistic word processing measured by the complete composite paradigm (CPc paradigm). The participants were asked to match the cued target parts of two characters which were presented for either a long (600 ms) or a short duration (170 ms). They were also tested by two popular versions of the CPc paradigm: the "early-fixed" task where the attention cue was visible from the beginning of each trial at a fixed position, and the "delayed-random" task where the cue showed up after the study character at random locations. The holistic word effect, as indexed by the alignment × congruency interaction, was identified in both tasks and was unaffected by the stimuli duration in both tasks. Meanwhile, the "delayed-random" task did not bring about larger holistic word effect than the "early-fixed" task. These results suggest the exposure duration (from around 150 to 600 ms) has a limited impact on the holistic word effect, and have methodological implications for experiment designs in this field.

Attention, Exposure Duration, and Gaze Shifting in Naming Performance

ERIC Educational Resources Information Center

Roelofs, Ardi

2011-01-01

Two experiments are reported in which the role of attribute exposure duration in naming performance was examined by tracking eye movements. Participants were presented with color-word Stroop stimuli and left- or right-pointing arrows on different sides of a computer screen. They named the color attribute and shifted their gaze to the arrow to…

Concentrated sodium chloride brine solutions as an additional treatment for preventing the introduction of nonindigenous species in the ballast tanks of ships declaring no ballast on board.

PubMed

Santagata, Scott; Bacela, Karolina; Reid, David F; Mclean, Kevin A; Cohen, Jill S; Cordell, Jeffery R; Brown, Christopher W; Johengen, Thomas H; Ruiz, Gregory M

2009-02-01

Currently, seawater flushing is the only management strategy for reducing the number of viable organisms in residual sediments and water of ballast tanks of vessels declaring no ballast on board (NOBOB) that traffic ports of the eastern United States. Previously, we identified several species of freshwater and brackish-water peracarid crustaceans able to survive the osmotic shock that occurs during open-ocean ballast water exchange and, potentially, to disperse over long distances via ballasted ships and NOBOB vessels. We tested the efficacy of concentrated sodium chloride brine solutions as an additional treatment for eradicating the halotolerant taxa often present in the ballast tanks of NOBOB ships. The lowest brine treatments (30 ppt for 1 h) caused 100% mortality in several species of cladocerans and copepods collected from oligohaline habitats. Several brackish-water peracarid crustaceans, however, including some that can survive in freshwater as well, required higher brine concentrations and longer exposure durations (45-60 ppt for 3-24 h). The most resilient animals were widely introduced peracarid crustaceans that generally prefer mesohaline habitats but do not tolerate freshwater (required brine treatments of 60-110 ppt for 3-24 h). Brine treatments (30 ppt) also required less time to cause 100% mortality for eight taxa compared with treatments using 34 ppt seawater. Based on these experiments and published data, we present treatment strategies for the ballast tank biota often associated with NOBOB vessels entering the Great Lakes region. We estimate the lethal dosage of brine for 95% of the species in our experiments to be 110 ppt (95% confidence interval, 85-192 ppt) when the exposure time is 1 h and 60 ppt (95% confidence interval, 48-98 ppt) when the exposure duration is 6 h or longer.

Reproduction in the space environment: Part II. Concerns for human reproduction

NASA Technical Reports Server (NTRS)

Jennings, R. T.; Santy, P. A.

1990-01-01

Long-duration space flight and eventual colonization of our solar system will require successful control of reproductive function and a thorough understanding of factors unique to space flight and their impact on gynecologic and obstetric parameters. Part II of this paper examines the specific environmental factors associated with space flight and the implications for human reproduction. Space environmental hazards discussed include radiation, alteration in atmospheric pressure and breathing gas partial pressures, prolonged toxicological exposure, and microgravity. The effects of countermeasures necessary to reduce cardiovascular deconditioning, calcium loss, muscle wasting, and neurovestibular problems are also considered. In addition, the impact of microgravity on male fertility and gamete quality is explored. Due to current constraints, human pregnancy is now contraindicated for space flight. However, a program to explore effective countermeasures to current constraints and develop the required health care delivery capability for extended-duration space flight is suggested. A program of Earth- and space-based research to provide further answers to reproductive questions is suggested.

Proteomic Analyses of Corneal Tissue Subjected to Alkali Exposure

PubMed Central

Parikh, Toral; Eisner, Natalie; Venugopalan, Praseeda; Yang, Qin; Lam, Byron L.

2011-01-01

Purpose. To determine whether exposure to alkaline chemicals results in predictable changes in corneal protein profile. To determine whether protein profile changes are indicative of severity and duration of alkali exposure. Methods. Enucleated bovine and porcine (n = 59 each) eyes were used for exposure to sodium, ammonium, and calcium hydroxide, respectively. Eyes were subjected to fluorescein staining, 5-bromo-2′-deoxy-uridine (BrdU) labeling. Excised cornea was subjected to protein extraction, spectrophotometric determination of protein amount, dynamic light scattering and SDS-PAGE profiling, mass spectrometric protein identification, and iTRAQ-labeled quantification. Select identified proteins were subjected to Western blot and immunohistochemical analyses. Results. Alkali exposure resulted in lower protein extractability from corneal tissue. Elevated aggregate formation was found with strong alkali exposure (sodium hydroxide>ammonium, calcium hydroxide), even with a short duration of exposure compared with controls. The protein yield after exposure varied as a function of postexposure time. Protein profiles changed because of alkali exposure. Concentration and strength of the alkali affected the profile change significantly. Mass spectrometry identified 15 proteins from different bands with relative quantification. Plexin D1 was identified for the first time in the cornea at a protein level that was further confirmed by Western blot and immunohistochemical analyses. Conclusions. Exposure to alkaline chemicals results in predictable and reproducible changes in corneal protein profile. Stronger alkali, longer durations, or both, of exposure resulted in lower yields and significant protein profile changes compared with controls. PMID:20861482

Are current guidelines for sun protection optimal for health? Exploring the evidence.

PubMed

Lucas, Robyn M; Neale, Rachel E; Madronich, Sasha; McKenzie, Richard L

2018-06-15

Exposure of the skin to ultraviolet (UV) radiation is the main risk factor for skin cancer, and a major source of vitamin D, in many regions of the world. Sun protection messages to minimize skin cancer risks but avoid vitamin D deficiency are challenging, partly because levels of UV radiation vary by location, season, time of day, and atmospheric conditions. The UV Index provides information on levels of UV radiation and is a cornerstone of sun protection guidelines. Current guidelines from the World Health Organization are that sun protection is required only when the UV Index is 3 or greater. This advice is pragmatic rather than evidence based. The UV Index is a continuous scale; more comprehensive sun protection is required as the UV Index increases. In addition, a wide range of UVA doses is possible with a UVI of 3, from which there may be health consequences, while full sun protection when the UVI is "moderate" (between 3 and 5) may limit vitamin D production. Finally, the duration of time spent in the sun is an essential component of a public health message, in addition to the intensity of ambient UV radiation as measured by the UV Index. Together these provide the dose of UV radiation that is relevant to both skin cancer genesis and vitamin D production. Further education is required to increase the understanding of the UV Index; messages framed using the UV Index need to incorporate the importance of duration of exposure and increasing sun protection with increasing dose of UV radiation.

Circadian Entrainment, Sleep-Wake Regulation and Neurobehavioral Performance During Extended Duration Space Flight

NASA Technical Reports Server (NTRS)

Czeisler, Charles A.

1999-01-01

Long-duration manned space flight requires crew members to maintain a high level of cognitive performance and vigilance while operating and monitoring sophisticated instrumentation. However, the reduction in the strength of environmental synchronizers in the space environment leads to misalignment of circadian phase among crew members, coupled with restricted time available to sleep, results in sleep deprivation and consequent deterioration of neurobehavioral function. Crew members are provided, and presently use, long-acting benzodiazepine hypnotics on board the current, relatively brief space shuttle missions to counteract such sleep disruption, a situation that is only likely to worsen during extended duration missions. Given the known carry-over effects of such compounds on daytime performance, together with the reduction in emergency readiness associated with their use at night, NASA has recognized the need to develop effective but safe countermeasures to allow crew members to obtain an adequate amount of sleep. Over the past eight years, we have successfully implemented a new technology for shuttle crew members involving bright light exposure during the pre-launch period to facilitate adaptation of the circadian timing system to the inversions of the sleep-wake schedule often required during dual shift missions. However for long duration space station missions it will be necessary to develop effective and attainable countermeasures that can be used chronically to optimize circadian entrainment. Our current research effort is to study the effects of light-dark cycles with reduced zeitgeber strength, such as are anticipated during long-duration space flight, on the entrainment of the endogenous circadian timing system and to study the effects of a countermeasure that consists of scheduled brief exposures to bright light on the human circadian timing system. The proposed studies are designed to address the following Specific Aims: (1) test the hypothesis that synchronization of the human circadian pacemaker will be disturbed in men and women by the reduction in LD cycle strength. (2) test the hypothesis that this disturbed circadian synchronization will result in the secretion of the sleep-promoting hormone melatonin during the waking day, disturbed sleep, reduced growth hormone secretion, and impaired performance and daytime alertness; (3) as a countermeasure, test the hypothesis that brief daily exposures to bright light (10,000 lux) will reestablish normal entrained circadian phase, resulting in improved sleep consolidation, normalized sleep structure and endogenous growth hormone secretion and enhanced daytime performance. To date, we have carried out twelve experiments to address Hypotheses I and 2 and data analyses are in progress. The results of the current research may have important implications for the treatment of circadian rhythm sleep disorders, such as delayed sleep phase syndrome and shift-work dyssomnia, which are anticipated to have a high incidence and prevalence during extended duration space flight such as planned for the International Space Station and manned missions to Mars.

Mechanistic investigation of doxycycline photosensitization by picosecond-pulsed and continuous wave laser irradiation of cells in culture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shea, C.R.; Hefetz, Y.; Gillies, R.

1990-04-15

In order to elucidate the photophysical mechanisms of cellular phototoxicity sensitized by doxycycline, MGH-U1 human bladder carcinoma cells in vitro were treated with 20.7 microM doxycycline and irradiated with either a pulsed (lambda = 355 nm, pulse duration = 24 ps) or a continuous wave (lambda = 351 nm) laser. Cumulative radiant exposure and irradiance were systematically varied in experiments with both lasers. Phototoxicity was assessed by epifluorescence microscopy of unfixed cells using rhodamine 123 labeling of mitochondria. With the continuous wave source, the cumulative radiant exposure required for induction of phototoxic injury was independent of irradiance. With the 24-ps-pulsedmore » source, a significantly lower cumulative radiant exposure was required to induce the phototoxicity when the peak irradiance was 5.8 x 10(7) or 1.3 x 10(8) watts cm-2 compared with when peak irradiance was either lower (6.0 x 10(6) watts cm-2) or higher (7.6 x 10(8) watts cm-2). The measured fluorescence lifetimes of doxycycline in buffered saline solution were longer than the laser pulse duration of 24 ps. The increased efficiency of photosensitization at the optimal peak irradiance in the ps domain appears to result from sequential multiphoton absorption involving higher excited states of the singlet manifold. At the highest irradiance studied, on the other hand, reduced efficiency of photosensitization is attributed to increased photodegradation of doxycycline from higher excited states by processes such as photoionization. A model consistent with these observations is presented along with calculations, based on simple rate equations, that fit the essentials of the proposed model.« less

Development of a scintillating optical fiber ionization calorimeter

NASA Astrophysics Data System (ADS)

Takahashi, Y.

1990-10-01

A design study of a scintillation fiber (SF) calorimeter for a cosmic ray observation is made. An evaluation of various fibers and design configuration was made. The proposed design has a dimension of 1 m (W) x 1 m (L) x 16 cm (H) contains 1000 fibers at each of 40 x- or 40 y-layers interleaved with 1mm thick leadplates. Two or four CCD Particle Track Imaging Systems are connected to a bundle of SF edges at x- and y-ends. The overall weight of a calorimeter is 1,200 kg including read-out systems and supporting boards. The designed calorimeter can measure cosmic ray nuclei and gamma-rays with position, angles and energy information suitable for detailed spectrum analysis. The system is particularly beneficial at very high energies where the flux is extremely low and it requires a very long exposure over many years in space. Emulsion chambers have an advantage for cosmic ray measurements if the exposure is limited to several months in space. In fact, the most important energy region for the current cosmic ray studies is at around 1,000 TeV where a drastic change of elemental composition is indicated by various indirect observations. A detector whose size is in the order of 1 m(sup 2) requires several years of exposure in space accumulate sufficient statistics near 1,000 TeV. Emulsions will be strongly contaminated by background radiation for such a long duration flight, while SF calorimeter is totally immune from this concern. This is particularly important for long-duration experiments. The SF calorimeter also allows time-tagging of individual events, extending the experimental capability in various ways.

Development of a scintillating optical fiber ionization calorimeter

NASA Technical Reports Server (NTRS)

Takahashi, Y.

1990-01-01

A design study of a scintillation fiber (SF) calorimeter for a cosmic ray observation is made. An evaluation of various fibers and design configuration was made. The proposed design has a dimension of 1 m (W) x 1 m (L) x 16 cm (H) contains 1000 fibers at each of 40 x- or 40 y-layers interleaved with 1mm thick leadplates. Two or four CCD Particle Track Imaging Systems are connected to a bundle of SF edges at x- and y-ends. The overall weight of a calorimeter is 1,200 kg including read-out systems and supporting boards. The designed calorimeter can measure cosmic ray nuclei and gamma-rays with position, angles and energy information suitable for detailed spectrum analysis. The system is particularly beneficial at very high energies where the flux is extremely low and it requires a very long exposure over many years in space. Emulsion chambers have an advantage for cosmic ray measurements if the exposure is limited to several months in space. In fact, the most important energy region for the current cosmic ray studies is at around 1,000 TeV where a drastic change of elemental composition is indicated by various indirect observations. A detector whose size is in the order of 1 m(sup 2) requires several years of exposure in space accumulate sufficient statistics near 1,000 TeV. Emulsions will be strongly contaminated by background radiation for such a long duration flight, while SF calorimeter is totally immune from this concern. This is particularly important for long-duration experiments. The SF calorimeter also allows time-tagging of individual events, extending the experimental capability in various ways.

Caffeine dependence in rats: effects of exposure duration and concentration.

PubMed

Dingle, Rachel N; Dreumont-Boudreau, Sarah E; Lolordo, Vincent M

2008-09-03

Groups of rats were chronically exposed to a 1.0-g/L caffeine solution for 5, 10, 15 or 20 days. Upon removal of caffeine, rats were given brief exposure to a novel flavour CS (withdrawal CS) followed by 12 days of plain water and then brief exposure to a second flavour CS (neutral CS). Only rats exposed to 20 days of caffeine strongly preferred the neutral CS to the withdrawal CS in a 2-bottle test. In Experiment 2, groups of rats were chronically exposed to caffeine at one of four concentrations (1.0, 0.5, 0.25, or 0.125 g/L) for 21 days, after which withdrawal and neutral CSs were established. Only rats that drank the highest caffeine concentration, 1.0 g/L, preferred the neutral CS to the withdrawal CS. This suggests that long exposure to a strong caffeine solution is required in order to induce dependence in rats such that a CS associated with the withdrawal of caffeine becomes avoided.

Quantified activity pattern data from 6 to 27-month-old farmworker children for use in exposure assessment.

PubMed

Beamer, Paloma; Key, Maya E; Ferguson, Alesia C; Canales, Robert A; Auyeung, Willa; Leckie, James O

2008-10-01

This study was conducted to describe exposure prone behaviors of infants and toddlers in the farmworker community. Analysis of hand and mouth contact frequencies and durations aids understanding of how children interact with their environment and are exposed via contact with surfaces. All 23 participating children (8 female infants, 5 male infants, 5 female toddlers and 5 male toddlers) lived with at least one farmworker. Children were videotaped at home for 2-6 h. Video footage was translated into micro-level activity time series (MLATS) for both hands and the mouth. MLATS were processed to calculate hourly duration in microenvironments, contact frequency, hourly contact duration and median contact duration. The median hourly duration spent indoors was 53 min/h. The median hand-to-mouth frequency was 15.2 events/h and the median object-to-mouth frequency was 27.2 events/h. The hourly mouthing duration was 1.2 and 2.2 min/h with the hands and objects, respectively. The median mouthing duration with hands and objects was 2 s. The median contact frequency for both hands combined was 689.4 events/h with an hourly contact duration of 100.5 min/h and a median contact duration of 3s. Infants had higher mouthing frequencies with non-dietary objects while toddlers had higher mouthing frequencies with objects associated with pica (i.e., paper). Boys had higher contact frequencies while girls had longer contact durations. These sub-group differences indicate factors such as age and gender should be accounted for when conducting exposure assessments. Contact frequencies in this study are higher than current US EPA recommendations, questioning their protective value for infants and toddlers.

Quantified Activity Pattern Data from 6-to-27-Month-Old Farmworker Children for Use in Exposure Assessment

PubMed Central

Beamer, Paloma; Key, Maya E.; Ferguson, Alesia C.; Canales, Robert A.; Auyeung, Willa; Leckie, James O.

2008-01-01

This study was conducted to describe exposure prone behaviors of infants and toddlers in the farmworker community. Analysis of hand and mouth contact frequencies and durations aids understanding of how children interact with their environment and are exposed via contact with surfaces. All 23 participating children (8 female infants, 5 male infants, 5 female toddlers and 5 male toddlers) lived with at least one farmworker. Children were videotaped at home for 2–6 hours. Video footage was translated into micro- level activity time series (MLATS) for both hands and the mouth. MLATS were processed to calculate hourly duration in microenvironments, contact frequency, hourly contact duration and median contact duration. The median hourly duration spent indoors was 53 min/hr. The median hand-to-mouth frequency was 15.2 events/hr and the median object-to-mouth frequency was 27.2 events/hr. The hourly mouthing duration was 1.2 and 2.2 min/hr with the hands and objects respectively. The median mouthing duration with hands and objects was 2 seconds. The median contact frequency for both hands combined was 689.4 events/hr with an hourly contact duration of 100.5 min/hr and a median contact duration of 3 seconds. Infants had higher mouthing frequencies with non-dietary objects while toddlers had higher mouthing frequencies with objects associated with pica (i.e., paper). Boys had higher contact frequencies while girls had longer contact durations. These sub-group differences indicate factors such as age and gender should be accounted for when conducting exposure assessments. Contact frequencies in this study are higher than current U.S. EPA recommendations, questioning their protective value for infants and toddlers. PMID:18723168

Effects of exposure to 56Fe particles or protons on fixed-ratio operant responding in rats

NASA Technical Reports Server (NTRS)

Rabin, Bernard M.; Buhler, Lynn L.; Joseph, James A.; Shukitt-Hale, Barbara; Jenkins, Daniel G.

2002-01-01

On long-duration trips outside of the magnetosphere, astronauts will be exposed to protons and to heavy particles which can affect their performance of required tasks. It is essential to determine the range of behaviors that might be affected by exposure to these types of radiation in order to understand the nature of behavioral deficits and to develop effective countermeasures. The present experiment examined the ability of rats to make an operant response following exposure to protons (250 MeV, 4 Gy) or 56Fe particles (1 GeV/n, 1 or 2 Gy). Following irradiation, rats were trained to press a lever in order to obtain food reinforcement. They were then placed on an ascending fixed-ratio schedule from FR-1 (each lever press rewarded with a food pellet) through FR-35 (35 lever presses required for 1 food pellet). Rats exposed to 4 Gy of protons or 1 Gy of 56Fe particles responded similarly to controls, increasing their rate of responding as the ratio increased. However, rats exposed to 2 Gy of 56Fe particles failed to increase their rate of responding at ratios greater than FR-20, indicating that rats exposed to 2 Gy of 56Fe particles cannot respond appropriately to increasing work requirements.

Impact of Elevated Core Body Temperature on Attention Networks.

PubMed

Liu, Kai; Jiang, Qingjun; Li, Li; Li, Bo; Yang, Zhen; Qian, Shaowen; Li, Min; Sun, Gang

2015-12-01

Cognitive function can be impaired after passive heat exposure and with an elevation in core body temperature (Tcore). This study examined the dynamic correlation among passive heat exposure, Tcore, and cognition. We gave the Attention Network Test of alerting, orienting, and executive control to five groups of five young men who were being exposed to a hyperthermic condition (50°C, 40% relative humidity) for 0, 10, 20, 30, or 40 minutes. We used the participants' reaction time, accuracy (correct responses), efficiency (accuracy÷reaction time), and Tcore to estimate optimal curve models for best fit of data. We could not estimate an appropriate curve model for either alerting or orienting with Tcore, change in Tcore, or duration of passive heat exposure. We estimated quadratic models for Tcore and duration (adjusted R=0.752), change in Tcore and duration (0.906), executive control score and duration (0.509), and efficiency of executive control and duration (0.293). We estimated linear models for executive control score and Tcore (0.479), efficiency of executive control and Tcore (0.261), executive control score and change in Tcore (0.279), and efficiency of executive control and change in Tcore (0.262). Different attentional abilities had different sensitivities to thermal stress. Executive control of attention deteriorated linearly with a rise in Tcore within the normal physiologic range, but deteriorated nonlinearly with longer passive heat exposure.

Two forms of persistence in visual information processing.

PubMed

Di Lollo, Vincent; Dixon, Peter

1988-11-01

Iconic memory, which was initially regarded as a unitary phenomenon, has since been subdivided into several components. In the present work we examined the joint effects of two such components (visible persistence and the visual analog representation) on performance in a partial report task. The display consisted of 15 alphabetic characters arranged around the perimeter of an imaginary circle on the face of an oscilloscope. The observer named the character singled out by a bar-probe. Two factors were varied: exposure duration of the array (10, 50, 100, 150, 200, 300, 400 or 500 ms) and duration of blank period (interstimulus interval, ISI) between the termination of the array and the onset of the probe (0, 50, 100, 150, or 200 ms). Performance was progressively impaired as both exposure duration and ISI were increased. The results were explained in terms of a probabilistic combinatorial model in which the timecourses of visible persistence and of the visual analog representation are regarded as time-locked to the onset and to the end of stimulation, respectively. The impairing effect of exposure duration was attributed to the relatively high spatial demands of the task that could be met optimally by information in visible persistence (which declines as a function of exposure duration), but less adequately by information in the visual analog representation. A second experiment, employing a task with lesser spatial demands, confirmed this interpretation.

M and D SIG progress report: Laboratory simulations of LDEF impact features

NASA Technical Reports Server (NTRS)

Horz, Friedrich; Bernhard, R. P.; See, Thomas H.; Atkinson, Dale R.; Allbrooks, Martha K.

1991-01-01

Reported here are impact simulations into pure Teflon and aluminum targets. These experiments will allow first order interpretations of impact features on the Long Duration Exposure Facility (LDEF), and they will serve as guides for dedicated experiments that employ the real LDEF blankets, both unexposed and exposed, for a refined understanding of the Long Duration Exposure Facility's collisional environment.

Task exposures in an office environment: a comparison of methods.

PubMed

Van Eerd, Dwayne; Hogg-Johnson, Sheilah; Mazumder, Anjali; Cole, Donald; Wells, Richard; Moore, Anne

2009-10-01

Task-related factors such as frequency and duration are associated with musculoskeletal disorders in office settings. The primary objective was to compare various task recording methods as measures of exposure in an office workplace. A total of 41 workers from different jobs were recruited from a large urban newspaper (71% female, mean age 41 years SD 9.6). Questionnaire, task diaries, direct observation and video methods were used to record tasks. A common set of task codes was used across methods. Different estimates of task duration, number of tasks and task transitions arose from the different methods. Self-report methods did not consistently result in longer task duration estimates. Methodological issues could explain some of the differences in estimates seen between methods observed. It was concluded that different task recording methods result in different estimates of exposure likely due to different exposure constructs. This work addresses issues of exposure measurement in office environments. It is of relevance to ergonomists/researchers interested in how to best assess the risk of injury among office workers. The paper discusses the trade-offs between precision, accuracy and burden in the collection of computer task-based exposure measures and different underlying constructs captures in each method.

Exposure to space radiation of high-performance infrared multilayer filters

NASA Technical Reports Server (NTRS)

Seeley, J. S.; Hawkins, G. J.; Hunneman, R.

1991-01-01

The University of Reading experiment exposed IR interference filters and crystal substrates on identical earth facing and leading-edge sites of the Long Duration Exposure Facility (LDEF). Filters mostly comprised multilayer coatings of lead telluride (PbTe)/II-IV on germanium (Ge) and other substrates: crystals comprised CdTe, MgF2, sapphire, quartz, silicon, and some softer materials. Identical control samples were maintained in the laboratory throughout the experiment. The filters were novel in their design, construction and manufacture, and categorized high-performance because of their ability to resolve emission spectra of the important atmospheric gases for various purposes in remote sensing. No significant changes were found in the spectra of the hard-coated filters or in the harder crystals (the softer materials were degraded to an extent). By virtue of this well-documented and long exposure in LDEF, the qualification of the filter type is significantly improved for its future requirements.

Development and management of a radon assessment strategy suitable for underground railway tunnelling projects.

PubMed

Purnell, C J; Frommer, G; Chan, K; Auch, A A

2004-01-01

The construction of underground tunnels through radon-bearing rock poses a radiation health risk to tunnelling workers from exposure to radon gas and its radioactive decay products. This paper presents the development and practical application of a radon assessment strategy suitable for the measurement of radon in tunnelling work environments in Hong Kong. The assessment strategy was successfully evaluated on a number of underground railway tunnelling projects over a 3 y period. Radon measurements were undertaken using a combination of portable radon measurement equipment and track etch detectors (TEDs) deployed throughout the tunnels. The radon gas monitoring results were used to confirm that ventilation rates were adequate or identified, at an early stage, when further action to reduce radon levels was required. Exposure dose estimates based on the TED results showed that the exposure of tunnel workers to radon did not exceed 3 mSv per annum for the duration of each project.

Plasma Vehicle Charging Analysis for Orion Flight Test 1

NASA Technical Reports Server (NTRS)

Lallement, L.; McDonald, T.; Norgard, J.; Scully, B.

2014-01-01

In preparation for the upcoming experimental test flight for the Orion crew module, considerable interest was raised over the possibility of exposure to elevated levels of plasma activity and vehicle charging both externally on surfaces and internally on dielectrics during the flight test orbital operations. Initial analysis using NASCAP-2K indicated very high levels of exposure, and this generated additional interest in refining/defining the plasma and spacecraft models used in the analysis. This refinement was pursued, resulting in the use of specific AE8 and AP8 models, rather than SCATHA models, as well as consideration of flight trajectory, time duration, and other parameters possibly affecting the levels of exposure and the magnitude of charge deposition. Analysis using these refined models strongly indicated that, for flight test operations, no special surface coatings were necessary for the thermal protection system, but would definitely be required for future GEO, trans-lunar, and extra-lunar missions...

Plasma Vehicle Charging Analysis for Orion Flight Test 1

NASA Technical Reports Server (NTRS)

Scully, B.; Norgard, J.

2015-01-01

In preparation for the upcoming experimental test flight for the Orion crew module, considerable interest was raised over the possibility of exposure to elevated levels of plasma activity and vehicle charging both externally on surfaces and internally on dielectrics during the flight test orbital operations. Initial analysis using NASCAP-2K indicated very high levels of exposure, and this generated additional interest in refining/defining the plasma and spacecraft models used in the analysis. This refinement was pursued, resulting in the use of specific AE8 and AP8 models, rather than SCATHA models, as well as consideration of flight trajectory, time duration, and other parameters possibly affecting the levels of exposure and the magnitude of charge deposition. Analysis using these refined models strongly indicated that, for flight test operations, no special surface coatings were necessary for the Thermal Protection System (TPS), but would definitely be required for future GEO, trans-lunar, and extra-lunar missions.

HIF-1 and SKN-1 coordinate the transcriptional response to hydrogen sulfide in Caenorhabditis elegans.

PubMed

Miller, Dana L; Budde, Mark W; Roth, Mark B

2011-01-01

Hydrogen sulfide (H₂S) has dramatic physiological effects on animals that are associated with improved survival. C. elegans grown in H₂S are long-lived and thermotolerant. To identify mechanisms by which adaptation to H₂S effects physiological functions, we have measured transcriptional responses to H₂S exposure. Using microarray analysis we observe rapid changes in the abundance of specific mRNAs. The number and magnitude of transcriptional changes increased with the duration of H₂S exposure. Functional annotation suggests that genes associated with protein homeostasis are upregulated upon prolonged exposure to H₂S. Previous work has shown that the hypoxia-inducible transcription factor, HIF-1, is required for survival in H₂S. In fact, we show that hif-1 is required for most, if not all, early transcriptional changes in H₂S. Moreover, our data demonstrate that SKN-1, the C. elegans homologue of NRF2, also contributes to H₂S-dependent changes in transcription. We show that these results are functionally important, as skn-1 is essential to survive exposure to H₂S. Our results suggest a model in which HIF-1 and SKN-1 coordinate a broad transcriptional response to H₂S that culminates in a global reorganization of protein homeostasis networks.

Airborne concentrations of benzene for dock workers at the ExxonMobil refinery and chemical plant, Baton Rouge, Louisiana, USA (1977-2005).

PubMed

Widner, Thomas E; Gaffney, Shannon H; Panko, Julie M; Unice, Kenneth M; Burns, Amanda M; Kreider, Marisa; Marshall, J Ralph; Booher, Lindsay E; Gelat, Richard H; Paustenbach, Dennis J

2011-03-01

Benzene is a natural constituent of crude oil and natural gas (0.1-3.0% by volume). Materials that are refined from crude oil and natural gas contain some residual benzene. Few datasets have appeared in the peer-reviewed literature characterizing exposures to benzene at specific refineries or during specific tasks. In this study, historical samples of airborne benzene collected from 1977-2005 at the ExxonMobil Baton Rouge, Louisiana, USA, docks were evaluated. Workers were categorized into 11 job titles, and both non-task (≤180 min sample duration) and task-related (<180 min) benzene concentrations were assessed. Approximately 800 personal air samples (406 non-task and 397 task-related) were analyzed. Non-task samples showed that concentrations varied significantly across job titles and generally resulted from exposures during short-duration tasks such as tank sampling. The contractor - tankerman job title had the highest average concentration [N=38, mean 1.4 parts per million (ppm), standard deviation (SD) 2.6]. Task-related samples indicated that the highest exposures were associated with the disconnection of cargo loading hoses (N=134, mean 11 ppm, SD 32). Non-task samples for specific job categories showed that concentrations have decreased over the past 30 years. Recognizing the potential for benzene exposure, this facility has required workers to use respiratory protective equipment during selected tasks and activities; thus, the concentrations measured were likely greater than those that the employee actually experienced. This study provides a job title- and task-focused analysis of occupational exposure to benzene during dock facility operations that is insightful for understanding the Baton Rouge facility and others similar to it over the past 30 years.

A Toxicological Framework for the Prioritization of Children’s Safe Product Act Data

PubMed Central

Smith, Marissa N.; Grice, Joshua; Cullen, Alison; Faustman, Elaine M.

2016-01-01

In response to concerns over hazardous chemicals in children’s products, Washington State passed the Children’s Safe Product Act (CSPA). CSPA requires manufacturers to report the concentration of 66 chemicals in children’s products. We describe a framework for the toxicological prioritization of the ten chemical groups most frequently reported under CSPA. The framework scores lifestage, exposure duration, primary, secondary and tertiary exposure routes, toxicokinetics and chemical properties to calculate an exposure score. Four toxicological endpoints were assessed based on curated national and international databases: reproductive and developmental toxicity, endocrine disruption, neurotoxicity and carcinogenicity. A total priority index was calculated from the product of the toxicity and exposure scores. The three highest priority chemicals were formaldehyde, dibutyl phthalate and styrene. Elements of the framework were compared to existing prioritization tools, such as the United States Environmental Protection Agency’s (EPA) ExpoCast and Toxicological Prioritization Index (ToxPi). The CSPA framework allowed us to examine toxicity and exposure pathways in a lifestage-specific manner, providing a relatively high throughput approach to prioritizing hazardous chemicals found in children’s products. PMID:27104547

Post-Stress Combined Administration of Beta-Receptor and Glucocorticoid Antagonists as a Novel Preventive Treatment in an Animal Model of PTSD

DTIC Science & Technology

2010-05-01

prenatal stress as a factor in vulnerability to develop PTSD upon adult exposure to traumatic stress. Thus, although the duration of this Concept...including fear conditioning and extinction; and 3) test the combined drug treatment using the established model. Although we developed a reliable test...our lab, but had to be modified and adjusted to suit the time frame required by the design of these experiments. Others we had to develop , set up

The Rise and Fall of Priming: How Visual Exposure Shapes Cortical Representations of Objects

PubMed Central

Zago, Laure; Fenske, Mark J.; Aminoff, Elissa; Bar, Moshe

2006-01-01

How does the amount of time for which we see an object influence the nature and content of its cortical representation? To address this question, we varied the duration of initial exposure to visual objects and then measured functional magnetic resonance imaging (fMRI) signal and behavioral performance during a subsequent repeated presentation of these objects. We report a novel ‘rise-and-fall’ pattern relating exposure duration and the corresponding magnitude of fMRI cortical signal. Compared with novel objects, repeated objects elicited maximal cortical response reduction when initially presented for 250 ms. Counter-intuitively, initially seeing an object for a longer duration significantly reduced the magnitude of this effect. This ‘rise-and-fall’ pattern was also evident for the corresponding behavioral priming. To account for these findings, we propose that the earlier interval of an exposure to a visual stimulus results in a fine-tuning of the cortical response, while additional exposure promotes selection of a subset of key features for continued representation. These two independent mechanisms complement each other in shaping object representations with experience. PMID:15716471

Effects of cycloheximide on extinction in an appetitively motivated operant conditioning task depend on re-exposure duration.

PubMed

Mierzejewski, Pawel; Olczak, Mieszko; Rogowski, Artur; Kostowski, Wojciech; Samochowiec, Jerzy; Filip, Malgorzata; Przegalinski, Edmund; Bienkowski, Przemyslaw

2008-08-29

Little is known about the role of new protein synthesis in extinction of operant responding for natural and chemical reinforcers. In the present study, the authors investigated whether the effects of a protein synthesis inhibitor, cycloheximide (CHX) on extinction of operant responding for sweet reward depended on the duration of re-exposure sessions. In addition, the authors investigated whether the effects of CHX on extinction could generalize to relapse of saccharin seeking induced by discrete cues. CHX injected after short re-exposure sessions (5min) accelerated extinction of non-reinforced responding. In contrast, the drug injected after long re-exposure sessions (30min) partially inhibited extinction. Reinstatement of saccharin seeking induced by the saccharin-paired discrete cues was not altered by the previous treatment with CHX. Concluding, the results of the present study indicate that: (i) the protein synthesis inhibitor, CHX can alter extinction of operant responding for sweet reward in rats; (ii) the effects of CHX on extinction critically depend on the duration of re-exposure/extinction sessions and do not generalize to relapse of saccharin seeking induced by discrete cues.

A case-control study of bladder cancer in the United States rubber and tyre industry.

PubMed

Checkoway, H; Smith, A H; McMichael, A J; Jones, F S; Monson, R R; Tyroler, H A

1981-08-01

A case-control study of bladder cancer was conducted in five United States rubber and tyre companies to determine if there were high-risk jobs and work areas within the industry. The study included 220 male cases of bladder cancer, of whom 107 were identified from hospital record reviews and 113 from death certificates. Each case was matched individually with two industry controls by sex, race, year of birth, and company. One control was matched additionally by year of hire and duration of employment. Comparisons of cases and controls not matched by year of hire and age of hire showed no differences for those variables, which suggests that age and calendar period of first exposure to the industry were not risk determinants. When the work histories of both cases and controls were contrasted it was found that cases were more likely than controls to have worked in milling (odds ratio (OR) = 1.91) and calender operation (OR = 2.21) jobs. The relative risk estimates for milling and calender operation both exhibited linear trends of increase with duration of exposure. Milling and calender operation jobs entail potential exposures to volatilised reaction products from heated rubber stock. A better understanding of aetiological associations with job type will require more detailed characterisation of the work environment with regard to the sources and levels of aromatic amines and other suspected bladder carcinogens.

A case-control study of bladder cancer in the United States rubber and tyre industry.

PubMed Central

Checkoway, H; Smith, A H; McMichael, A J; Jones, F S; Monson, R R; Tyroler, H A

1981-01-01

A case-control study of bladder cancer was conducted in five United States rubber and tyre companies to determine if there were high-risk jobs and work areas within the industry. The study included 220 male cases of bladder cancer, of whom 107 were identified from hospital record reviews and 113 from death certificates. Each case was matched individually with two industry controls by sex, race, year of birth, and company. One control was matched additionally by year of hire and duration of employment. Comparisons of cases and controls not matched by year of hire and age of hire showed no differences for those variables, which suggests that age and calendar period of first exposure to the industry were not risk determinants. When the work histories of both cases and controls were contrasted it was found that cases were more likely than controls to have worked in milling (odds ratio (OR) = 1.91) and calender operation (OR = 2.21) jobs. The relative risk estimates for milling and calender operation both exhibited linear trends of increase with duration of exposure. Milling and calender operation jobs entail potential exposures to volatilised reaction products from heated rubber stock. A better understanding of aetiological associations with job type will require more detailed characterisation of the work environment with regard to the sources and levels of aromatic amines and other suspected bladder carcinogens. PMID:7272236

Determination of cellular injury and death thresholds following exposure to high voltage 10ns electrical pulses

NASA Astrophysics Data System (ADS)

Ibey, Bennett L.; Roth, Caleb C.; Bernhard, Joshua A.; Pakhomov, Andrei G.; Wilmink, Gerald J.; Pakhomova, Olga

2011-03-01

Intense, nanosecond-duration electric pulses (nsEP) have been introduced as a novel modality to alter cellular function, with a mechanism of action qualitatively different from micro- and millisecond duration pulses used in electroporation. In this study, we determined the thresholds for plasma membrane injury (within 15 minutes) and cell death (at 24 hours) for 4 different cell types (CHO-K1, HeLa, Jurkat and U937). Plasma membrane injury was measured by flow cytometry using two fluorescent dyes, namely Annexin V-FITC, which binds to phosphatidylserine (PS) upon its externalization (subtle membrane injury), and propidium iodide (PI), which is typically impermeable to the cell, but enters when large pores are formed in the plasma membrane. In all cell types, 10-ns pulses caused phosphatidylserine (PS) externalization at low doses (<150kV/cm and 100 pulses for each cell type) and no PI uptake. Jurkat and U937 cell lines showed substantial cell death without uptake of PI (15 minutes post exposure) suggesting either delayed permeabilization due to swelling, or damage to intracellular components. In CHO-K1 and HeLa cell lines, PI uptake occurred at low doses relative to that necessary to cause cell death suggesting a necrotic death similar to longer pulse exposures. These findings suggest that nanosecond pulses may be beneficial in applications that require selective elimination of specific cell types.

Quantified outdoor micro-activity data for children aged 7-12-years old.

PubMed

Beamer, Paloma I; Luik, Catherine E; Canales, Robert A; Leckie, James O

2012-01-01

Estimation of aggregate exposure and risk requires detailed information regarding dermal contact and mouthing activity. We analyzed micro-level activity time series (MLATS) of children aged 7-12 years to quantify these contact behaviors and evaluate differences by age and gender. In all, 18 children, aged 7-12 years, were videotaped while playing outdoors. Video footage was transcribed via Virtual Timing Device (VTD) software. We calculated the hand and mouth contact frequency, hourly duration and median duration of contact with 16 object categories. Median mouthing frequencies were 12.6 events/h and 2.6 events/h for hands and non-dietary objects, respectively. Median hourly mouthing duration was 0.4 min/h and 0.1 min/h with hands and objects. Median mouthing contact duration was 1 s and 1.5 s with hands and objects, respectively. The median object contact frequency for both the hands combined was 537.3 events/h with an hourly contact duration of 81.8 min/h and a median contact duration of 3 s. There were no significant differences in the mouthing activity between genders or age groups. Female children had longer and more frequent hand contacts with several surface types. Age was negatively correlated with hand contacts of floor and wood surfaces. Contact frequencies in this study are higher than current regulatory recommendations for this age group.

Effect of level, duration, and inter-pulse interval of 1-2 kHz sonar signal exposures on harbor porpoise hearing.

PubMed

Kastelein, Ronald A; Hoek, Lean; Gransier, Robin; Rambags, Martijn; Claeys, Naomi

2014-07-01

Safety criteria for underwater low-frequency active sonar sounds produced during naval exercises are needed to protect harbor porpoise hearing. As a first step toward defining criteria, a porpoise was exposed to sequences consisting of series of 1-s, 1-2 kHz sonar down-sweeps without harmonics (as fatiguing noise) at various combinations of average received sound pressure levels (SPLs; 144-179 dB re 1 μPa), exposure durations (1.9-240 min), and duty cycles (5%-100%). Hearing thresholds were determined for a narrow-band frequency-swept sine wave centered at 1.5 kHz before exposure to the fatiguing noise, and at 1-4, 4-8, 8-12, 48, 96, 144, and 1400 min after exposure, to quantify temporary threshold shifts (TTSs) and recovery of hearing. Results show that the inter-pulse interval of the fatiguing noise is an important parameter in determining the magnitude of noise-induced TTS. For the reported range of exposure combinations (duration and SPL), the energy of the exposure (i.e., cumulative sound exposure level; SELcum) can be used to predict the induced TTS, if the inter-pulse interval is known. Exposures with equal SELcum but with different inter-pulse intervals do not result in the same induced TTS.

Duration of time on shift before accidental blood or body fluid exposure for housestaff, nurses, and technicians.

PubMed

Green-McKenzie, Judith; Shofer, Frances S

2007-01-01

Shift work has been found to be associated with an increased rate of errors and accidents among healthcare workers (HCWs), but the effect of shift work on accidental blood and body fluid exposure sustained by HCWs has not been well characterized. To determine the duration of time on shift before accidental blood and body fluid exposure in housestaff, nurses, and technicians and the proportion of housestaff who sustain a blood and body fluid exposure after 12 hours on duty. This retrospective, descriptive study was conducted during a 24-month period at a large urban teaching hospital. Participants were HCWs who sustained an accidental blood and body fluid exposure. Housestaff were on duty significantly longer than both nursing staff (P=.02) and technicians (P<.0001) before accidental blood and body fluid exposure. Half of the blood and body fluid exposures sustained by housestaff occurred after being on duty 8 hours or more, and 24% were sustained after being on duty 12 hours or more. Of all HCWs, 3% reported an accidental blood and body fluid exposure, with specific rates of 7.9% among nurses, 9.4% among housestaff, and 3% among phlebotomists. Housestaff were significantly more likely to have longer duration of time on shift before blood and body fluid exposure than were the other groups. Almost one-quarter of accidental blood and body fluid exposures to housestaff were incurred after they had been on duty for 12 hours or more. Housestaff sustained a higher rate of accidental blood and body fluid exposures than did nursing staff and technicians.

Safety of spray-dried powder formulated Pseudomonas fluorescens strain CL145A exposure to subadult/adult unionid mussels during simulated open-water treatments

USGS Publications Warehouse

Luoma, James A.; Weber, Kerry L.; Waller, Diane L.; Wise, Jeremy K.; Mayer, Denise A.; Aloisi, Douglas B.

2015-01-01

After exposure, the mussels were consolidated into wire mesh cages and placed in the Black River for a 27-28 day postexposure period, after which time survival of mussels was assessed. Of the 1,170 mussels tested in the study, 3 were confirmed dead and 5 were not recovered and treated as mortalities in the analysis. The effect and interactions of species, SDP exposure concentration, and SDP exposure duration were analyzed and did not affect mussel survival (p > 0.98). The results from this study indicate that SDP exposure at the maximum approved open-water concentration of 100 mg/L for up to 3 times the maximum approved open-water exposure duration of 8 hours (in other words for 24 hours of exposure) is unlikely to reduce survival of subadult or adult mussels.

Effects of cryogen spray cooling and high radiant exposures on selective vascular injury during laser irradiation of human skin.

PubMed

Tunnell, James W; Chang, David W; Johnston, Carol; Torres, Jorge H; Patrick, Charles W; Miller, Michael J; Thomsen, Sharon L; Anvari, Bahman

2003-06-01

Increasing radiant exposure offers a means to increase treatment efficacy during laser-mediated treatment of vascular lesions, such as port-wine stains; however, excessive radiant exposure decreases selective vascular injury due to increased heat generation within the epidermis and collateral damage to perivascular collagen. To determine if cryogen spray cooling could be used to maintain selective vascular injury (ie, prevent epidermal and perivascular collagen damage) when using high radiant exposures (16-30 J/cm2). Observational study. Academic hospital and research laboratory. Twenty women with normal abdominal skin (skin phototypes I-VI). Skin was irradiated with a pulsed dye laser (wavelength = 585 nm; pulse duration = 1.5 milliseconds; 5-mm-diameter spot) using various radiant exposures (8-30 J/cm2) without and with cryogen spray cooling (50- to 300-millisecond cryogen spurts). Hematoxylin-eosin-stained histologic sections from each irradiated site were examined for the degree of epidermal damage, maximum depth of red blood cell coagulation, and percentage of vessels containing perivascular collagen coagulation. Long cryogen spurt durations (>200 milliseconds) protected the epidermis in light-skinned individuals (skin phototypes I-IV) at the highest radiant exposure (30 J/cm2); however, epidermal protection could not be achieved in dark-skinned individuals (skin phototypes V-VI) even at the lowest radiant exposure (8 J/cm2). The red blood cell coagulation depth increased with increasing radiant exposure (to >2.5 mm for skin phototypes I-IV and to approximately 1.2 mm for skin phototypes V-VI). In addition, long cryogen spurt durations (>200 milliseconds) prevented perivascular collagen coagulation in all skin types. Cryogen spurt durations much longer than those currently used in therapy (>200 milliseconds) may be clinically useful for protecting the epidermis and perivascular tissues when using high radiant exposures during cutaneous laser therapies. Additional studies are necessary to prove clinical safety of these protocols.

Establishing Long-Term Efficacy in Chronic Disease: Use of Recursive Partitioning and Propensity Score Adjustment to Estimate Outcome in MS

PubMed Central

Goodin, Douglas S.; Jones, Jason; Li, David; Traboulsee, Anthony; Reder, Anthony T.; Beckmann, Karola; Konieczny, Andreas; Knappertz, Volker

2011-01-01

Context Establishing the long-term benefit of therapy in chronic diseases has been challenging. Long-term studies require non-randomized designs and, thus, are often confounded by biases. For example, although disease-modifying therapy in MS has a convincing benefit on several short-term outcome-measures in randomized trials, its impact on long-term function remains uncertain. Objective Data from the 16-year Long-Term Follow-up study of interferon-beta-1b is used to assess the relationship between drug-exposure and long-term disability in MS patients. Design/Setting To mitigate the bias of outcome-dependent exposure variation in non-randomized long-term studies, drug-exposure was measured as the medication-possession-ratio, adjusted up or down according to multiple different weighting-schemes based on MS severity and MS duration at treatment initiation. A recursive-partitioning algorithm assessed whether exposure (using any weighing scheme) affected long-term outcome. The optimal cut-point that was used to define “high” or “low” exposure-groups was chosen by the algorithm. Subsequent to verification of an exposure-impact that included all predictor variables, the two groups were compared using a weighted propensity-stratified analysis in order to mitigate any treatment-selection bias that may have been present. Finally, multiple sensitivity-analyses were undertaken using different definitions of long-term outcome and different assumptions about the data. Main Outcome Measure Long-Term Disability. Results In these analyses, the same weighting-scheme was consistently selected by the recursive-partitioning algorithm. This scheme reduced (down-weighted) the effectiveness of drug exposure as either disease duration or disability at treatment-onset increased. Applying this scheme and using propensity-stratification to further mitigate bias, high-exposure had a consistently better clinical outcome compared to low-exposure (Cox proportional hazard ratio = 0.30–0.42; p<0.0001). Conclusions Early initiation and sustained use of interferon-beta-1b has a beneficial impact on long-term outcome in MS. Our analysis strategy provides a methodological framework for bias-mitigation in the analysis of non-randomized clinical data. Trial Registration Clinicaltrials.gov NCT00206635 PMID:22140424

Sleep Duration and Quality in Pregnant Women: A Cross-Sectional Survey in China.

PubMed

Xu, Xianglong; Liu, Dengyuan; Zhang, Zhangyi; Sharma, Manoj; Zhao, Yong

2017-07-20

Objectives: Good maternal health and fetal development require sufficient and good quality of sleep during pregnancy. This study investigated sleep duration and quality in pregnant women, assessing factors with possibly influence on sleep. Method: A cross-sectional survey was conducted on pregnant women between June and August in 2015 in 16 hospitals in five provinces in China. A total of 2345 pregnant women aged 18 years and older were surveyed. Insufficient sleeping duration was defined as sleeping of less than 7 h per day. Excessive sleep duration was defined as sleeping of more than 9 h per day. Results: A total of 561 (23.9%) participants reported insufficient sleeping duration, whereas 485 (20.9%) claimed excessive sleep duration. A total of 358 (15.2%) of pregnant women reported problems regarding sleep quality. Compared to pregnant women with sufficient sleeping duration, those with insufficient sleeping duration were prone to have poor sleep quality, whereas those with excessive sleeping duration featured low possibility of poor sleep quality. High-risk groups of insufficient sleep duration include women of Han nationality, with siblings, in their first trimester of pregnancy, receiving care in low-capacity/quality hospital settings, and with daily or 1-3 days of secondhand smoke exposure. High-risk groups of excessive sleep duration include women living in rural areas, unemployed, in their third trimester of pregnancy, and receiving care in medium-capacity/quality hospital settings. High-risk groups of poor sleep quality include women of non-Han nationality, low income level, in their third trimester of pregnancy, and with insufficient sleep duration. Conclusions: Insufficient/excessive sleep duration and poor sleep quality commonly occur during pregnancy in China. Findings provide a better understanding of the influencing factors of insufficient/excessive sleep duration and poor quality of sleep. These findings have some implications for future interventions on sleep among pregnant women.

Sleep Duration and Quality in Pregnant Women: A Cross-Sectional Survey in China

PubMed Central

Liu, Dengyuan; Zhang, Zhangyi; Zhao, Yong

2017-01-01

Objectives: Good maternal health and fetal development require sufficient and good quality of sleep during pregnancy. This study investigated sleep duration and quality in pregnant women, assessing factors with possibly influence on sleep. Method: A cross-sectional survey was conducted on pregnant women between June and August in 2015 in 16 hospitals in five provinces in China. A total of 2345 pregnant women aged 18 years and older were surveyed. Insufficient sleeping duration was defined as sleeping of less than 7 h per day. Excessive sleep duration was defined as sleeping of more than 9 h per day. Results: A total of 561 (23.9%) participants reported insufficient sleeping duration, whereas 485 (20.9%) claimed excessive sleep duration. A total of 358 (15.2%) of pregnant women reported problems regarding sleep quality. Compared to pregnant women with sufficient sleeping duration, those with insufficient sleeping duration were prone to have poor sleep quality, whereas those with excessive sleeping duration featured low possibility of poor sleep quality. High-risk groups of insufficient sleep duration include women of Han nationality, with siblings, in their first trimester of pregnancy, receiving care in low-capacity/quality hospital settings, and with daily or 1–3 days of secondhand smoke exposure. High-risk groups of excessive sleep duration include women living in rural areas, unemployed, in their third trimester of pregnancy, and receiving care in medium-capacity/quality hospital settings. High-risk groups of poor sleep quality include women of non-Han nationality, low income level, in their third trimester of pregnancy, and with insufficient sleep duration. Conclusions: Insufficient/excessive sleep duration and poor sleep quality commonly occur during pregnancy in China. Findings provide a better understanding of the influencing factors of insufficient/excessive sleep duration and poor quality of sleep. These findings have some implications for future interventions on sleep among pregnant women. PMID:28726747

INHALATION EXPOSURE-RESPONSE ASSESSMENTS FOR FIVE CHEMICALS

EPA Science Inventory

Inhalation exposure-response assessments for five chemicals (acrolein, ethylene oxide, hexachlorocyclopentadiene, hydrogen sulfide, and phosgene) for less-than-lifetime durations are being developed to inform the development of the Inhalation Exposure-Response Analysis Methodolog...

Repeated Alcohol Extinction Sessions in Conjunction with MK-801, but not Yohimbine or Propranolol, Reduces Subsequent Alcohol Cue-Induced Responding in Rats

PubMed Central

Williams, Keith L.; Harding, Kaitlyn M.

2014-01-01

Cues associated with alcohol can stimulate subjective states that increase relapse. Alcohol-cue associations may be strengthened by enhancing adrenergic activity with yohimbine or weakened by blocking adrenergic activity with propranolol. Alcohol-cue associations may also be weakened by long cue exposure sessions or strengthened by short cue exposure sessions. A useful treatment approach for alcoholism may combine adrenergic manipulation with cue exposure sessions of a specific duration. The present study sought to determine if cue exposure during long- or short-duration extinction sessions with post-session yohimbine or propranolol would alter alcohol cue-induced responding and self-administration. Rats were trained to respond for alcohol during sessions that included an olfactory cue given at the beginning of the session and a visual/auditory cue complex delivered concurrently with alcohol. Cue-induced responding was assessed before and after the repeated extinction sessions. Repeated alcohol extinction sessions of long duration (45 min) or short duration (5 min) were followed immediately by injections of saline, yohimbine, or propranolol. After the second set of cue-induced responding tests, reacquisition of operant alcohol self-administration was examined. To determine if the experimental procedures were sensitive to memory manipulation through other pharmacological mechanisms, the NMDA receptor antagonist MK-801 was given 20 min prior to long-duration extinction sessions. Both the long- and short-duration extinction sessions decreased cue-induced responding. Neither yohimbine nor propranolol, given post-session, had subsequent effects on cue-induced responding or alcohol self-administration. MK-801 blocked the effect of extinction sessions on cue-induced responding but had no effect on self-administration. The present study shows that manipulation of the NMDA system in combination with alcohol cue exposure therapy during extinction-like sessions may be more effective than manipulation of the adrenergic system in reducing the strength of alcohol-cue associations in this specific model of alcohol relapse. PMID:24269546

Permeabilization of the nuclear envelope following nanosecond pulsed electric field exposure.

PubMed

Thompson, Gary L; Roth, Caleb C; Kuipers, Marjorie A; Tolstykh, Gleb P; Beier, Hope T; Ibey, Bennett L

2016-01-29

Permeabilization of cell membranes occurs upon exposure to a threshold absorbed dose (AD) of nanosecond pulsed electric fields (nsPEF). The ultimate, physiological bioeffect of this exposure depends on the type of cultured cell and environment, indicating that cell-specific pathways and structures are stimulated. Here we investigate 10 and 600 ns duration PEF effects on Chinese hamster ovary (CHO) cell nuclei, where our hypothesis is that pulse disruption of the nuclear envelope membrane leads to observed cell death and decreased viability 24 h post-exposure. To observe short-term responses to nsPEF exposure, CHO cells have been stably transfected with two fluorescently-labeled proteins known to be sequestered for cellular chromosomal function within the nucleus - histone-2b (H2B) and proliferating cell nuclear antigen (PCNA). H2B remains associated with chromatin after nsPEF exposure, whereas PCNA leaks out of nuclei permeabilized by a threshold AD of 10 and 600 ns PEF. A downturn in 24 h viability, measured by MTT assay, is observed at the number of pulses required to induce permeabilization of the nucleus. Copyright © 2015 Elsevier Inc. All rights reserved.

Determination of the exposure parameters that maximise the concentrations of the anaesthetic/sedative eugenol in rainbow trout (Oncorhynchus mykiss) skin-on fillet tissue.

PubMed

Meinertz, J R; Porcher, S T; Smerud, J R; Gaikowski, M P

2014-01-01

Studies were conducted to determine the anaesthetic/sedative concentrations and durations that would maximise anaesthetic/sedative residue concentrations in rainbow trout (Oncorhynchus mykiss) skin-on fillet tissue. Rainbow trout (167-404 g) were exposed to 50 mg l(-1) AQUI-S(®) 20E (10% active ingredient, eugenol) in 17°C freshwater for durations up to 1440 min, 100 and 250 mg l(-1) AQUI-S(®) 20E for durations up to 240 min, and 500 and 1000 mg l(-1) AQUI-S(®) 20E for durations up to 90 min. Fish exposed to 100 mg l(-1) AQUI-S(®) 20E for durations of 30, 60, 120 and 240 min had the greatest eugenol concentrations in the fillet tissue, 50, 58, 54 and 62 µg g(-1), respectively. All other exposure concentrations and durations resulted in significantly lower eugenol concentrations, i.e. all < 39 µg g(-1).

Determination of the exposure parameters that maximise the concentrations of the anaesthetic/sedative eugenol in rainbow trout (Oncorhynchus mykiss) skin-on fillet tissue

USGS Publications Warehouse

Meinertz, Jeffery R.; Porcher, Scott T.; Smerud, Justin R.

2014-01-01

Studies were conducted to determine the anaesthetic/sedative concentrations and durations that would maximize anaesthetic/sedative residue concentrations in rainbow trout (Oncorhynchus mykiss) skin-on fillet tissue. Rainbow trout (167–404 g) were exposed to 50 mg l−1 AQUI-S® 20E (10% active ingredient, eugenol) in 17°C freshwater for durations up to 1440 min, 100 and 250 mg l−1 AQUI-S® 20E for durations up to 240 min, and 500 and 1000 mg l−1 AQUI-S® 20E for durations up to 90 min. Fish exposed to 100 mg l−1 AQUI-S® 20E for durations of 30, 60, 120 and 240 min had the greatest eugenol concentrations in the fillet tissue, 50, 58, 54 and 62 µg g−1, respectively. All other exposure concentrations and durations resulted in significantly lower eugenol concentrations, i.e. all −1.

Organic solvent exposure and depressive symptoms among licensed pesticide applicators in the Agricultural Health Study

PubMed Central

Siegel, Miriam; Starks, Sarah E.; Sanderson, Wayne T.; Kamel, Freya; Hoppin, Jane A.; Gerr, Fred

2017-01-01

Purpose Although organic solvents are often used in agricultural operations, neurotoxic effects of solvent exposure have not been extensively studied among famers. The current analysis examined associations between questionnaire-based metrics of organic solvent exposure and depressive symptoms among farmers. Methods Results from 692 male Agricultural Health Study participants were analyzed. Solvent type and exposure duration were assessed by questionnaire. An “ever-use” variable and years of use categories were constructed for exposure to gasoline, paint/lacquer thinner, petroleum distillates, and any solvent. Depressive symptoms were ascertained with the Center for Epidemiologic Studies Depression Scale (CES-D); scores were analyzed separately as continuous (0-60) and dichotomous (<16 versus ≥16) variables. Multivariate linear and logistic regression models were used to estimate crude and adjusted associations between measures of solvent exposure and CES-D score. Results Forty-one percent of the sample reported some solvent exposure. The mean CES-D score was 6.5 (SD=6.4; median=5; range=0 – 44); 92% of the sample had a score below 16. After adjusting for covariates, statistically significant associations were observed between ever-use of any solvent, long duration of any solvent exposure, ever-use of gasoline, ever-use of petroleum distillates, and short duration of petroleum distillate exposure and continuous CES-D score (p<0.05). Although nearly all associations were positive, fewer statistically significant associations were observed between metrics of solvent exposure and the dichotomized CES-D variable. Conclusions Solvent exposures were associated with depressive symptoms among farmers. Efforts to limit exposure to organic solvents may reduce the risk of depressive symptoms among farmers. PMID:28702848

Extensive but not Limited Repeated Trials in Passive Avoidance Task Induce Stress-like Symptoms and Affect Memory Function in Rats.

PubMed

Tabassum, Saiqa; Haider, Saida

2018-02-10

Stressful and emotionally arousing experiences are remembered, and previous reports show that repeated exposure to stressful condition enhances emotional learning. However, the usefulness of the repeated exposure depends on the intensity and duration. Although repeated training as a strategy to improve memory performance is receiving increased attention from researchers, repeated training may induce stressful effects that have not yet been considered. The present study investigated whether exposure to repetitive learning trials with limited or extensive durations in a passive avoidance task (PAT) would be beneficial or harmful to emotional memory performance in rats. Rats were exposed to repetitive learning trials for two different durations in the limited exposure (exposure to four repetitive trials) and extensive exposure groups (exposure to 16 repetitive trials) in a single day to compare the impact of both conditions on rat emotional memory performance. Alterations in corticosterone content and associated oxidative and neurochemical systems were assessed to explore the underlying mechanism responsible for changes in emotional memory. Following extensive exposure, a negative impact on emotional memory was observed compared with the limited exposure group. A lack of any further improvement in memory function following extensive training exposure was supported by increased corticosterone levels, decreased 5-hydroxytryptamine (5-HT) levels and abnormal oxidative stress levels, which may induce negative effects on memory consolidation. It is suggested that limited exposure to repetitive learning trials is more useful for studying improvement in emotional memory, whereas extensive exposure may produce chronic stress-like condition that can be detrimental and responsible for compromised memory performance. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Planning strategies for development of effective exercise and nutrition countermeasures for long-duration space flight

NASA Technical Reports Server (NTRS)

Convertino, Victor A.

2002-01-01

Exercise and nutrition represent primary countermeasures used during space flight to maintain or restore maximal aerobic capacity, musculoskeletal structure, and orthostatic function. However, no single exercise, dietary regimen, or combination of prescriptions has proven entirely effective in maintaining or restoring cardiovascular and musculoskeletal functions to preflight levels after prolonged space flight. As human space flight exposures increase in duration, identification, assessment, and development of various effective exercise- and nutrition-based protective procedures will become paramount. The application of adequate dietary intake in combination with effective exercise prescription will be based on identification of basic physiologic stimuli that maintain normal function in terrestrial gravity, and understanding how specific combinations of exercise characteristics (e.g., duration, frequency, intensity, and mode) can be combined with minimal nutritional requirements that mimic the stimuli normally produced by living in Earth's gravity environment. This can be accomplished only with greater emphasis of research on ground-based experiments targeted at understanding the interactions between caloric intake and expenditure during space flight. Future strategies for application of nutrition and exercise countermeasures for long-duration space missions must be directed to minimizing crew time and the impact on life-support resources.

Planning strategies for development of effective exercise and nutrition countermeasures for long-duration space flight.

PubMed

Convertino, Victor A

2002-10-01

Exercise and nutrition represent primary countermeasures used during space flight to maintain or restore maximal aerobic capacity, musculoskeletal structure, and orthostatic function. However, no single exercise, dietary regimen, or combination of prescriptions has proven entirely effective in maintaining or restoring cardiovascular and musculoskeletal functions to preflight levels after prolonged space flight. As human space flight exposures increase in duration, identification, assessment, and development of various effective exercise- and nutrition-based protective procedures will become paramount. The application of adequate dietary intake in combination with effective exercise prescription will be based on identification of basic physiologic stimuli that maintain normal function in terrestrial gravity, and understanding how specific combinations of exercise characteristics (e.g., duration, frequency, intensity, and mode) can be combined with minimal nutritional requirements that mimic the stimuli normally produced by living in Earth's gravity environment. This can be accomplished only with greater emphasis of research on ground-based experiments targeted at understanding the interactions between caloric intake and expenditure during space flight. Future strategies for application of nutrition and exercise countermeasures for long-duration space missions must be directed to minimizing crew time and the impact on life-support resources.

Preliminary Assessment of Potential Habitat Composites' Durability when Exposed to a Long-Term Radiation Environment and Micrometeoroid Impacts

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; Graves, Russell; Golden, John; Atwell, William; O'Rouke, Mary Jane; Hill, Charles; Alred, John

2011-01-01

NASA's exploration goals include extending human presence beyond low earth orbit (LEO). As a result, habitation for crew is a critical requirement for meeting this goal. However, habitats are very large structures that contain a multitude of subsystems to sustain human life over long-durations in space, and one of the key challenges has been keeping weight to a minimum in order to reduce costs. Thus, light-weight and multifunctional structural materials are of great interest for habitation. NASA has started studying polymeric composite materials as potential lightweight and multifunctional structural materials for use in long-duration spaceflight. However, little is known about the survivability of these materials when exposed to the space environment outside of LEO for long durations. Thus, a study has been undertaken to investigate the durability of composite materials when exposed to long-duration radiation. Furthermore, as an addition to the primary study, a secondary preliminary investigation has been started on the micrometeoroid and orbital debris (MMOD) susceptibility of these materials after radiation exposure. The combined effects of radiation and MMOD impacts are the focus of this paper.

HUMAN EXPOSURE MODELING: CONCEPTS, METHODS, AND TOOLS

EPA Science Inventory

Understanding human exposure is critical when estimating the occurrence of deleterious effects that could follow contact with environmental contaminants. For many pollutants, the intensity, duration, frequency, route, and timing of exposure is highly variable, particularly whe...

a Comparison of Evaluations and Assessments Obtained Using Alternative Standards for Predicting the Hazards of Whole-Body Vibration and Repeated Shocks

NASA Astrophysics Data System (ADS)

Lewis, C. H.; Griffin, M. J.

1998-08-01

There are three current standards that might be used to assess the vibration and shock transmitted by a vehicle seat with respect to possible effects on human health: ISO 2631/1 (1985), BS 6841 (1987) and ISO 2631-1 (1997). Evaluations have been performed on the seat accelerations measured in nine different transport environments (bus, car, mobile crane, fork-lift truck, tank, ambulance, power boat, inflatable boat, mountain bike) in conditions that might be considered severe. For each environment, limiting daily exposure durations were estimated by comparing the frequency weighted root mean square (i.e., r.m.s.) accelerations and the vibration dose values (i.e.,VDV), calculated according to each standard with the relevant exposure limits, action level and health guidance caution zones. Very different estimates of the limiting daily exposure duration can be obtained using the methods described in the three standards. Differences were observed due to variations in the shapes of the frequency weightings, the phase responses of the frequency weighting filters, the method of combining multi-axis vibration, the averaging method, and the assessment method. With the evaluated motions, differences in the shapes of the weighting filters results in up to about 31% difference in r.m.s. acceleration between the “old” and the “new” ISO standard and up to about 14% difference between BS 6841 and the “new” ISO 2631. There were correspondingly greater differences in the estimates of safe daily exposure durations. With three of the more severe motions there was a difference of more than 250% between estimated safe daily exposure durations based on r.m.s. acceleration and those based on fourth power vibration dose values. The vibration dose values provided the more cautious assessments of the limiting daily exposure duration.

Identification and classification of high risk groups for Coal Workers' Pneumoconiosis using an artificial neural network based on occupational histories: a retrospective cohort study

PubMed Central

Liu, Hongbo; Tang, Zhifeng; Yang, Yongli; Weng, Dong; Sun, Gao; Duan, Zhiwen; Chen, Jie

2009-01-01

Background Coal workers' pneumoconiosis (CWP) is a preventable, but not fully curable occupational lung disease. More and more coal miners are likely to be at risk of developing CWP owing to an increase in coal production and utilization, especially in developing countries. Coal miners with different occupational categories and durations of dust exposure may be at different levels of risk for CWP. It is necessary to identify and classify different levels of risk for CWP in coal miners with different work histories. In this way, we can recommend different intervals for medical examinations according to different levels of risk for CWP. Our findings may provide a basis for further emending the measures of CWP prevention and control. Methods The study was performed using longitudinal retrospective data in the Tiefa Colliery in China. A three-layer artificial neural network with 6 input variables, 15 neurons in the hidden layer, and 1 output neuron was developed in conjunction with coal miners' occupational exposure data. Sensitivity and ROC analyses were adapted to explain the importance of input variables and the performance of the neural network. The occupational characteristics and the probability values predicted were used to categorize coal miners for their levels of risk for CWP. Results The sensitivity analysis showed that influence of the duration of dust exposure and occupational category on CWP was 65% and 67%, respectively. The area under the ROC in 3 sets was 0.981, 0.969, and 0.992. There were 7959 coal miners with a probability value < 0.001. The average duration of dust exposure was 15.35 years. The average duration of ex-dust exposure was 0.69 years. Of the coal miners, 79.27% worked in helping and mining. Most of the coal miners were born after 1950 and were first exposed to dust after 1970. One hundred forty-four coal miners had a probability value ≥0.1. The average durations of dust exposure and ex-dust exposure were 25.70 and 16.30 years, respectively. Most of the coal miners were born before 1950 and began to be exposed to dust before 1980. Of the coal miners, 90.28% worked in tunneling. Conclusion The duration of dust exposure and occupational category were the two most important factors for CWP. Coal miners at different levels of risk for CWP could be classified by the three-layer neural network analysis based on occupational history. PMID:19785771

Photothermal damage is correlated to the delivery rate of time-integrated temperature

NASA Astrophysics Data System (ADS)

Denton, Michael L.; Noojin, Gary D.; Gamboa, B. Giovanna; Ahmed, Elharith M.; Rockwell, Benjamin A.

2016-03-01

Photothermal damage rate processes in biological tissues are usually characterized by a kinetics approach. This stems from experimental data that show how the transformation of a specified biological property of cells or biomolecule (plating efficiency for viability, change in birefringence, tensile strength, etc.) is dependent upon both time and temperature. However, kinetic methods require determination of kinetic rate constants and knowledge of substrate or product concentrations during the reaction. To better understand photothermal damage processes we have identified temperature histories of cultured retinal cells receiving minimum lethal thermal doses for a variety of laser and culture parameters. These "threshold" temperature histories are of interest because they inherently contain information regarding the fundamental thermal dose requirements for damage in individual cells. We introduce the notion of time-integrated temperature (Tint) as an accumulated thermal dose (ATD) with units of °C s. Damaging photothermal exposure raises the rate of ATD accumulation from that of the ambient (e.g. 37 °C) to one that correlates with cell death (e.g. 52 °C). The degree of rapid increase in ATD (ΔATD) during photothermal exposure depends strongly on the laser exposure duration and the ambient temperature.

Calculated values of atomic oxygen fluences and solar exposure on selected surfaces of LDEF

NASA Technical Reports Server (NTRS)

Gillis, J. R.; Pippin, H. G.; Bourassa, R. J.; Gruenbaum, P. E.

1995-01-01

Atomic oxygen (AO) fluences and solar exposure have been modeled for selected hardware from the Long Duration Exposure Facility (LDEF). The atomic oxygen exposure was modeled using the microenvironment modeling code SHADOWV2. The solar exposure was modeled using the microenvironment modeling code SOLSHAD version 1.0.

The immunotoxicological pattern of subchronic and chronic benzene exposure in rats.

PubMed

Karaulov, Alexander V; Mikhaylova, Irina V; Smolyagin, Alexander I; Boev, Viktor M; Kalogeraki, Alexandra; Tsatsakis, Aristides M; Engin, Ayse Basak

2017-06-05

Exposure to benzene and its inevitable metabolites can result in deleterious effects on human health, including lymphocytopenia, hematotoxicity and cancer. However, the duration of exposure might alter the effects including immune consequences. The aim of this study was to determine whether benzene could modulate lymphocyte proliferation induced by the T cell mitogen concanavalin A, in rats, at different exposure durations. 386 Wistar rats were assigned into control and treatment groups which were subdivided into groups for 45, 90 and 135days for 0,6mL/kg of drinking water mixed benzene treatment. The percentage of CD3+, CD4+, CD8+ spleen lymphocytes was defined using the flow cytometer. Interleukin (IL)-4, IL-6, IL-10 and interferon-gamma, in supernatants of splenocyte cultures stimulated with Concanavalin A, were assessed by enzyme-linked immunosorbent assay (ELISA) technique. The decrease in the total lymphocyte and T cell counts were associated with increased benzene exposure duration. Th2-type cytokine, IL-4 significantly increased, whereas IL-6, CD4+T cells, CD4+/CD8+ ratio and CD3+ T cells decreased. Despite the positive correlation between benzene toxicity and indicated increased immune responses, 45-day exposure to benzene appeared to be the most sensitive time point for evaluating benzene cytotoxicity. Copyright © 2017 Elsevier B.V. All rights reserved.

Repeated or long-duration TASER electronic control device exposures: acidemia and lack of respiration.

PubMed

Jauchem, James R

2010-03-01

Conducted energy weapons (CEWs), such as TASER devices, may be applied to subjects in repeated or long-duration modes. Such applications may result in more potentially harmful effects (as reflected in blood factor changes) than shorter exposures. In this review, results from a number of studies of repeated and long-duration CEW exposures in an animal model are examined. Additionally, a few limited investigations of shorter CEW applications to human subjects are considered. Specifically, in anesthetized swine, increased blood acidity (acidemia) and lack of effective respiration were found to be common during or immediately after CEW exposure. The acidemia could have been due to both metabolic and respiratory acidosis. A relatively rapid recovery toward baseline pH levels occurred. The lack of effective respiration has not been verified in experiments of CEW applications to human subjects; however, in some incidents of human deaths after CEW exposures subjects have been reported to stop breathing immediately after the exposure. It is not known if all human subjects exposed to CEW applications in the field (often "on drugs" or "in excited delirium") would be able to maintain adequate breathing. Since a limited number of short CEW applications would be less likely to cause adverse effects, however, CEWs can still be a valuable tool for law enforcement activities.

Use of alternating and pulsed direct current electrified fields for zebra mussel control

USGS Publications Warehouse

Luoma, James A.; Dean, Jan C.; Severson, Todd J.; Wise, Jeremy K.; Barbour, Matthew

2017-01-01

Alternatives to chemicals for controlling dreissenid mussels are desirable for environmental compatibility, but few alternatives exist. Previous studies have evaluated the use of electrified fields for stunning and/or killing planktonic life stages of dreissenid mussels, however, the available literature on the use of electrified fields to control adult dreissenid mussels is limited. We evaluated the effects of sinusoidal alternating current (AC) and 20% duty cycle square-wave pulsed direct current (PDC) exposure on the survival of adult zebra mussels at water temperatures of 10, 15, and 22 °C. Peak voltage gradients of ~ 17 and 30 Vp/cm in the AC and PDC exposures, respectively, were continuously applied for 24, 48, or 72 h. Peak power densities ranged from 77,999 to 107,199 µW/cm3 in the AC exposures and 245,320 to 313,945 µW/cm3 in the PDC exposures. The peak dose ranged from 6,739 to 27,298 Joules/cm3 and 21,306 to 80,941 Joules/cm3 in the AC and PDC exposures, respectively. The applied power ranged from 16.6 to 68.9 kWh in the AC exposures and from 22.2 to 86.4 kWh in the PDC exposures. Mortality ranged from 2.7 to 92.7% in the AC exposed groups and from 24.0 to 98.7% in PDC exposed groups. Mortality increased with corresponding increases in water temperature and exposure duration, and we observed more zebra mussel mortality in the PDC exposures. Exposures conducted with AC required less of a peak dose (Joules/cm3) but more applied power (kWh) to achieve the same level of adult zebra mussel mortality as corresponding PDC exposures. The results demonstrate that 20% duty cycle square-wave PDC requires less energy than sinusoidal AC to inducing the same level of adult zebra mussel mortality.

Carbon Dioxide - Our Common "Enemy"

NASA Technical Reports Server (NTRS)

James, John T.; Macatangay, Ariel

2009-01-01

Health effects of brief and prolonged exposure to carbon dioxide continue to be a concern for those of us who manage this pollutant in closed volumes, such as in spacecraft and submarines. In both examples, considerable resources are required to scrub the atmosphere to levels that are considered totally safe for maintenance of crew health and performance. Defining safe levels is not a simple task because of many confounding factors, including: lack of a robust database on human exposures, suspected significant variations in individual susceptibility, variations in the endpoints used to assess potentially adverse effects, the added effects of stress, and the fluid shifts associated with micro-gravity (astronauts only). In 2007 the National Research Council proposed revised Continuous Exposure Guidelines (CEGLs) and Emergency Exposure Guidelines (EEGLs) to the U.S. Navy. Similarly, in 2008 the NASA Toxicology Group, in cooperation with another subcommittee of the National Research Council, revised Spacecraft Maximum Allowable Concentrations (SMACs). In addition, a 1000-day exposure limit was set for long-duration spaceflights to celestial bodies. Herein we examine the rationale for the levels proposed to the U.S. Navy and compare this rationale with the one used by NASA to set its limits. We include a critical review of previous studies on the effects of exposure to carbon dioxide and attempt to dissect out the challenges associated with setting fully-defensible limits. We also describe recent experiences with management of carbon dioxide aboard the International Space Station with 13 persons aboard. This includes the tandem operations of the Russian Vozduk and the U.S. Carbon Dioxide Removal System. A third removal system is present while the station is docked to the Shuttle spacecraft, so our experience includes the lithium hydroxide system aboard Shuttle for the removal of carbon dioxide. We discuss strategies for highly-efficient, regenerable removal of carbon dioxide that could meet the 1000-day SMAC of 0.5%, which would apply to long-duration voyages to Mars.

Occupational exposures and lung cancer risk among Minnesota taconite mining workers.

PubMed

Allen, Elizabeth M; Alexander, Bruce H; MacLehose, Richard F; Nelson, Heather H; Ryan, Andrew D; Ramachandran, Gurumurthy; Mandel, Jeffrey H

2015-09-01

To examine the association between employment duration, elongate mineral particle (EMP) exposure, silica exposure and the risk of lung cancer in the taconite mining industry. We conducted a nested case-control study of lung cancer within a cohort of Minnesota taconite iron mining workers employed by any of the mining companies in operation in 1983. Lung cancer cases were identified by vital records and cancer registry data through 2010. Two age-matched controls were selected from risk sets of cohort members alive and lung cancer free at the time of case diagnosis. Calendar time-specific exposure estimates were made for every job and were used to estimate workers' cumulative exposures. ORs and 95% CIs were estimated using conditional logistic regression. We evaluated total lung cancer risk and risk of histological subtype by total work duration and by cumulative EMP, and silica exposure by quartile of the exposure distribution. A total of 1706 cases and 3381 controls were included in the analysis. After adjusting for work in haematite mining, asbestos exposure and sex, the OR for total duration of employment was 0.99 (95% CI 0.96 to 1.01). The ORs for quartile 4 versus 1 of EMP and silica exposure were 0.82 (95% CI 0.57 to 1.19) and 0.97 (95% CI 0.70 to 1.35), respectively. The risk of each histological subtype of lung cancer did not change with increasing exposure. This study suggests that the estimated taconite mining exposures do not increase the risk of developing lung cancer. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Occupational Exposures and Lung Cancer Risk among Minnesota Taconite Mining Workers

PubMed Central

Allen, Elizabeth M; Alexander, Bruce H; MacLehose, Richard F; Nelson, Heather H; Ryan, Andrew D; Ramachandran, Gurumurthy; Mandel, Jeffrey H

2015-01-01

Objective To examine the association between employment duration, elongate mineral particle (EMP) exposure, and silica exposure and the risk of lung cancer in the taconite mining industry. Methods We conducted a nested case control study of lung cancer within a cohort of Minnesota taconite iron mining workers employed by any of the mining companies in operation in 1983. Lung cancer cases were identified by vital records and cancer registry data through 2010. Two age-matched controls were selected from risk sets of cohort members alive and lung cancer free at the time of case diagnosis. Calendar time-specific exposure estimates were made for every job and were used to estimate workers’ cumulative exposures. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic regression. We evaluated total lung cancer risk and risk of histological subtype by total work duration and by cumulative EMP and silica exposure by quartile of the exposure distribution. Results A total of 1,706 cases and 3,381 controls were included in the analysis. After adjusting for work in hematite mining, asbestos exposure, and sex, the OR for total duration of employment was 0.99 (95% CI: 0.96–1.01). The ORs for quartile 4 versus 1 of EMP and silica exposure were 0.82 (95% CI: 0.57–1.19) and 0.97 (95% CI: 0.70–1.35) respectively. The risk of each histological subtype of lung cancer did not change with increasing exposure. Conclusions This study suggests that the estimated taconite mining exposures do not increase the risk for the development of lung cancer. PMID:25977445

Biochemical effects of lead exposure on battery manufacture workers with reference to blood pressure, calcium metabolism and bone mineral density.

PubMed

Dongre, Nilima N; Suryakar, Adinath N; Patil, Arun J; Hundekari, Indira A; Devarnavadagi, Basavaraj B

2013-01-01

Lead is one of the most widely scattered toxic metals in the environment and used by mankind for over 9,000 years. Lead in the environment may be derived from natural or anthropogenic sources. In humans, lead can cause a wide range of biological effects depending upon the level and duration of exposure. The purpose of this study was to find out the effect of lead exposure on systolic and diastolic blood pressure, serum calcium, ionized calcium, phosphorus, parathyroid hormone and vitamin D and examine the overall effect of all these parameters on the bone mineral density of battery manufacture workers. For this study ninety battery manufacture workers were selected and divided in three groups depending upon duration of lead exposure. Group I-workers with duration of lead exposure 1-5 years, Group II-workers with duration of lead exposure 6-10 years and Group III-workers with duration of lead exposure more than 10 years. Each group consisted of thirty workers. Thirty age matched healthy control subjects were taken for comparison. Demographic, occupational and clinical data were collected by using questionnaire and interview. The venous blood samples were collected from the study groups and normal healthy control group. At the time of blood collection random urine samples were collected in amber coloured bottles. The biochemical parameters were estimated by using standard assay procedures. Statistical analysis of the data was done using independent student't' test for parametric variables. Values were expressed as mean ± standard deviation (SD). P values of 0.05 or less were considered to be statistically significant. The blood lead levels and urinary lead levels of all workers were significantly increased (P < 0.001) in proportion to the duration of lead exposure as compared to controls. Systolic and diastolic blood pressure were significantly raised (P < 0.001) in all three study groups of battery manufacture workers as compared to controls. Serum Calcium, Ionized calcium, phosphorus were significantly decreased (P < 0.001) in all the three study groups. Serum vitamin D levels were lowered (P < 0.01) and serum PTH was increased (P < 0.01) in workers as compared to controls. The results of this study clearly indicate that the absorption of lead is more in these workers which adversely affects blood pressure, disturbs calcium and phosphorus metabolism which further impairs mineralization of bone resulting in decreased bone mineral density observed in these workers. Lead toxicity is still persistent in battery manufacture workers though they are using sophisticated techniques in these industries. There is a need to protect the workers from the health hazards of occupational lead exposure.

Modeling the Unites States government's economic cost of noise-induced hearing loss for a military population.

PubMed

Tufts, Jennifer B; Weathersby, Paul K; Rodriguez, Francisco A

2010-05-01

The purpose of this paper is to demonstrate the feasibility and utility of developing economic cost models for noise-induced hearing loss (NIHL). First, we outline an economic model of NIHL for a population of US Navy sailors with an "industrial"-type noise exposure. Next, we describe the effect on NIHL-related cost of varying the two central model inputs--the noise-exposure level and the duration of exposure. Such an analysis can help prioritize promising areas, to which limited resources to reduce NIHL-related costs should be devoted. NIHL-related costs borne by the US government were computed on a yearly basis using a finite element approach that took into account varying levels of susceptibility to NIHL. Predicted hearing thresholds for the population were computed with ANSI S3.44-1996 and then used as the basis for the calculation of NIHL-related costs. Annual and cumulative costs were tracked. Noise-exposure level and duration were systematically varied to determine their effects on the expected lifetime NIHL-related cost of a specific US Navy sailor population. Our nominal noise-exposure case [93 dB(A) for six years] yielded a total expected lifetime cost of US $13,472 per sailor, with plausible lower and upper bounds of US $2,500 and US $26,000. Starting with the nominal case, a decrease of 50% in exposure level or duration would yield cost savings of approximately 23% and 19%, respectively. We concluded that a reduction in noise level would be more somewhat more cost-effective than the same percentage reduction in years of exposure. Our economic cost model can be used to estimate the changes in NIHL-related costs that would result from changes in noise-exposure level and/or duration for a single military population. Although the model is limited at present, suggestions are provided for adapting it to civilian populations.

Infant media exposure and toddler development.

PubMed

Tomopoulos, Suzy; Dreyer, Benard P; Berkule, Samantha; Fierman, Arthur H; Brockmeyer, Carolyn; Mendelsohn, Alan L

2010-12-01

To determine whether duration and content of media exposure in 6-month-old infants are associated with development at age 14 months. Longitudinal analysis of 259 mother-infant dyads participating in a long-term study related to early child development, from November 23, 2005, through January 14, 2008. An urban public hospital. Mothers with low socioeconomic status and their infants. Duration and content of media exposure at age 6 months. Cognitive and language development at age 14 months. Of 259 infants, 249 (96.1%) were exposed to media at age 6 months, with mean (SD) total exposure of 152.7 (124.5) min/d. In unadjusted and adjusted analyses, duration of media exposure at age 6 months was associated with lower cognitive development at age 14 months (unadjusted: r = -0.17, P < .01; adjusted: β = -0.15, P = .02) and lower language development (r = -0.16, P < .01; β = -0.16, P < .01). Of 3 types of content assessed, only 1 (older child/adult-oriented) was associated with lower cognitive and language development at age 14 months. No significant associations were seen with exposure to young child-oriented educational or noneducational content. This study is the first, to our knowledge, to have longitudinally assessed associations between media exposure in infancy and subsequent developmental outcomes in children from families with low socioeconomic status in the United States. Findings provide strong evidence in support of the American Academy of Pediatrics recommendations of no media exposure prior to age 2 years, although further research is needed.

Quantification of lower extremity physical exposures in various combinations of sit/stand time duration associated with sit-stand workstation.

PubMed

Pei, Huining; Yu, Suihuai; Babski-Reeves, Kari; Chu, Jianjie; Qu, Min; Tian, Baozhen; Li, Wenhua

2017-05-16

Sit-stand workstations are available for office work purposes but there is a dearth of quantitative evidence to state benefits for lower limb outcomes while using them. And there are no guidelines on what constitutes appropriate sit/stand time duration. The primary aim of this study has been to compare muscle activity and perceived discomfort in the lower extremity during various combinations of sit/stand time duration associated with a sit-stand workstation separately and to evaluate the effects of the sit-stand workstation on the lower extremity during the text entry task. During the 5 days, all participants completed a 2-h text entry task each day for various sit/stand time duration combinations as follows: 5/25 min, 10/20 min, 15/15 min, 20/10 min, 25/5 min. Lower extremity muscular exposure of 12 male and 13 female participants was collected at 8 sites by surface electromyography and body discomfort was calculated by a questionnaire under those 5 conditions. Results have demonstrated that lower extremity muscle activity has been significantly varied among the 5 sit/stand time duration groups. Perceived level of discomfort (PLD) has not differed significantly for 9 out of 10 body parts. The muscle activity of the thigh region was influenced by sit/stand time duration significantly. Ergonomic exposures of lower extremity when using a sit-stand workstation were increased, particularly during the long time standing posture. Results indicate that body mass index (BMI) and gender were not significant factors in this study. Combination of sit/stand time duration 25/5 min appears to show positive effects on relief of muscle exposure of back of thigh in the shifts of sitting and standing work position. Med Pr 2017;68(3):315-327. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

A PROBABILISTIC POPULATION EXPOSURE MODEL FOR PM10 AND PM 2.5

EPA Science Inventory

A first generation probabilistic population exposure model for Particulate Matter (PM), specifically for predicting PM10, and PM2.5, exposures of an urban, population has been developed. This model is intended to be used to predict exposure (magnitude, frequency, and duration) ...

Ocular hazards of light

NASA Technical Reports Server (NTRS)

Sliney, David H.

1994-01-01

The eye is protected against bright light by the natural aversion response to viewing bright light sources. The aversion response normally protects the eye against injury from viewing bright light sources such as the sun, arc lamps and welding arcs, since this aversion limits the duration of exposure to a fraction of a second (about 0.25 s). The principal retinal hazard resulting from viewing bright light sources is photoretinitis, e.g., solar retinitis with an accompanying scotoma which results from staring at the sun. Solar retinitis was once referred to as 'eclipse blindness' and associated 'retinal burn'. Only in recent years has it become clear that photoretinitis results from a photochemical injury mechanism following exposure of the retina to shorter wavelengths in the visible spectrum, i.e., violet and blue light. Prior to conclusive animal experiments at that time, it was thought to be a thermal injury mechanism. However, it has been shown conclusively that an intense exposure to short-wavelength light (hereafter referred to as 'blue light') can cause retinal injury. The product of the dose-rate and the exposure duration always must result in the same exposure dose (in joules-per-square centimeter at the retina) to produce a threshold injury. Blue-light retinal injury (photoretinitis) can result from viewing either an extremely bright light for a short time, or a less bright light for longer exposure periods. This characteristic of photochemical injury mechanisms is termed reciprocity and helps to distinguish these effects from thermal burns, where heat conduction requires a very intense exposure within seconds to cause a retinal coagulation otherwise, surrounding tissue conducts the heat away from the retinal image. Injury thresholds for acute injury in experimental animals for both corneal and retinal effects have been corroborated for the human eye from accident data. Occupational safety limits for exposure to UVR and bright light are based upon this knowledge. As with any photochemical injury mechanism must consider the action spectrum, which describes the relative effectiveness of different wavelengths in causing a photobiological effect. The action spectrum for photochemical retinal injury peaks at approximately 440 nm.

Reduced Exposure to Harmful and Potentially Harmful Smoke Constituents With the Tobacco Heating System 2.1.

PubMed

Lüdicke, Frank; Baker, Gizelle; Magnette, John; Picavet, Patrick; Weitkunat, Rolf

2017-02-01

Heating rather than burning tobacco reduces levels of harmful and potentially harmful constituents, and consumer products using this approach aim to reduce exposure to tobacco toxicants. The Tobacco Heating System (THS) version 2.1 has been enhanced from earlier prototypes with an improved heat control and sensorial experience and thereby user acceptance. Exposure measurements are required to determine whether it may be possible to reduce the individual health risk compared to smoking combustible cigarettes (CCs). This controlled clinical study randomly assigned 40 smokers to either a group continuing to use of their own CC brand (n = 20) or a group switching to THS 2.1 (n = 20) for 5 days. Biomarkers of exposure were measured at baseline and on day 1 through day 5. Product consumption, Human Puffing Topography, the occurrence of adverse events, and an assessment of subjective effects, such as smoking satisfaction and enjoyment of respiratory tract sensations, were also determined. The group of smokers who switched to THS 2.1 adapted their puffing behavior initially through longer puff duration and more puffs. During the duration of the study, total puff volume returned to baseline levels and the mean daily product consumption increased but with similar nicotine exposure compared to baseline CC use. Biomarkers of exposure to tobacco smoke toxicants which inform product risk assessment were significantly reduced with THS use compared to the CC group. THS 2.1 users experienced less reinforcing effects with THS 2.1 than with their own cigarette brand. THS 2.1 is a promising alternative to smoking CCs. Notwithstanding possible use adaption through consumption or puffing behavior, the exposure to harmful smoke constituents was markedly reduced with the new heated tobacco platform. Exposure markers to harmful and potentially harmful smoke constituents were lowered with the THS 2.1. Heating tobacco instead of burning can offer a potentially lower risk of delivering nicotine compared to CCs. © The Author 2016. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco.

Hearing threshold shifts and recovery after noise exposure in beluga whales, Delphinapterus leucas.

PubMed

Popov, Vladimir V; Supin, Alexander Ya; Rozhnov, Viatcheslav V; Nechaev, Dmitry I; Sysuyeva, Evgenia V; Klishin, Vladimir O; Pletenko, Mikhail G; Tarakanov, Mikhail B

2013-05-01

Temporary threshold shift (TTS) after loud noise exposure was investigated in a male and a female beluga whale (Delphinapterus leucas). The thresholds were evaluated using the evoked-potential technique, which allowed for threshold tracing with a resolution of ~1 min. The fatiguing noise had a 0.5 octave bandwidth, with center frequencies ranging from 11.2 to 90 kHz, a level of 165 dB re. 1 μPa and exposure durations from 1 to 30 min. The effects of the noise were tested at probe frequencies ranging from -0.5 to +1.5 octaves relative to the noise center frequency. The effect was estimated in terms of both immediate (1.5 min) post-exposure TTS and recovery duration. The highest TTS with the longest recovery duration was produced by noises of lower frequencies (11.2 and 22.5 kHz) and appeared at a test frequency of +0.5 octave. At higher noise frequencies (45 and 90 kHz), the TTS decreased. The TTS effect gradually increased with prolonged exposures ranging from 1 to 30 min. There was a considerable TTS difference between the two subjects.

Cognitive effects of radiation emitted by cellular phones: the influence of exposure side and time.

PubMed

Luria, Roy; Eliyahu, Ilan; Hareuveny, Ronen; Margaliot, Menachem; Meiran, Nachshon

2009-04-01

This study examined the time dependence effects of exposure to radiofrequency radiation (RFR) emitted by standard GSM cellular phones on the cognitive functions of humans. A total of 48 healthy right-handed male subjects performed a spatial working memory task (that required either a left-hand or a right-hand response) while being exposed to one of two GSM phones placed at both sides of the head. The subjects were randomly divided into three groups. Each group was exposed to one of three exposure conditions: left-side of the head, right-side, or sham-exposure. The experiment consisted of 12 blocks of trials. Response times (RTs) and accuracy of the responses were recorded. It was found that the average RT of the right-hand responses under left-side exposure condition was significantly longer than those of the right-side and sham-exposure groups averaged together during the first two time blocks. These results confirmed the existence of an effect of exposure on RT, as well as the fact that exposure duration (together with the responding hand and the side of exposure) may play an important role in producing detectable RFR effects on performance. Differences in these parameters might be the reason for the failure of certain studies to detect or replicate RFR effects. (c) 2008 Wiley-Liss, Inc.

Working conditions and occupational risk exposure in employees driving for work.

PubMed

Fort, Emmanuel; Ndagire, Sheba; Gadegbeku, Blandine; Hours, Martine; Charbotel, Barbara

2016-04-01

An analysis of the occupational constraints and exposures to which employees facing road risk at work are subject was performed, with comparison versus non-exposed employees. Objective was to improve knowledge of the characteristics of workers exposed to road risk in France and of the concomitant occupational constraints. The descriptive study was based on data from the 2010 SUMER survey (Medical Monitoring of Occupational Risk Exposure: Surveillance Médicale des Expositions aux Risques professionnels), which included data not only on road risk exposure at work but also on a range of socio-occupational factors and working conditions. The main variable of interest was "driving (car, truck, bus, coach, etc.) on public thoroughfares" for work (during the last week of work). This was a dichotomous "Yes/No" variable, distinguishing employees who drove for work; it also comprised 4-step weekly exposure duration: <2h, 2-10h, 10-20h and ≥20h. 75% of the employees with driving exposure were male. Certain socio-occupational categories were found significantly more frequently: professional drivers (INSEE occupations and socio-occupational categories (PCS) 64), skilled workers (PCS 61), intermediate professions and teaching, health, civil service (functionaries) and assimilated (PCS 46) and company executives (PCS 36). Employees with driving exposure more often worked in small businesses or establishments. Constraints in terms of schedule and work-time were more frequent in employees with driving exposure. Constraints in terms of work rhythm were more frequent in non-exposed employees, with the exception of external demands requiring immediate response. On the Karasek's Job Demand-Control Model, employees with driving exposure less often had low decision latitude. Prevalence of job-strain was also lower, as was prevalence of "iso-strain" (combination of job-strain and social isolation). Employees with driving exposure were less often concerned by hostile behavior and, when they did report such psychological violence (inspired on the Leymann questionnaire), it was significantly more frequently due to clients, users or patients. Employees with driving exposure at work showed several specificities. The present study, based on a representative nationwide survey of employees, confirmed the existence of differences in working conditions between employees with and without driving exposure at work. In employees with driving exposure, constraints in terms of work-time and rhythm increased with weekly exposure duration, as did tension at work and exposure to hostile behavior. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Association Between Breastfeeding Exposure and Duration, Neuropsychological Deficits, and Psychopathic Personality Traits in Offspring: The Moderating Role of 5HTTLPR.

PubMed

Jackson, Dylan B; Beaver, Kevin M

2016-03-01

A wealth of research has revealed that a shorter duration of breastfeeding during infancy can increase the risk of various maladaptive traits, including neuropsychological deficits. Despite the number of studies that have been conducted on the topic, few studies have explored whether the effects of breastfeeding on neuropsychological functioning and personality features persist into adulthood. Furthermore, very little research to date has examined whether this relationship is moderated by specific indicators of genetic risk. The current study examines the direct and interactive effects of breastfeeding experiences and the serotonin transporter polymorphism (5HTTLPR) on neuropsychological deficits and psychopathic personality traits. Using data from the National Longitudinal study of Adolescent Health, we find that no exposure to breastfeeding and a shorter duration of breastfeeding significantly increase the risk of exhibiting neuropsychological deficits during adolescence and early adulthood as well as psychopathic personality traits during adulthood. The results also reveal a number of gene × environment interactions between 5HTTLPR, breastfeeding exposure and breastfeeding duration in the prediction of neuropsychological deficits, but not in the prediction of psychopathic personality traits.

Effect of vibration duration on human discomfort. [passenger comfort and random vibration

NASA Technical Reports Server (NTRS)

Clevenson, S. A.; Dempsey, T. K.; Leatherwood, J. D.

1978-01-01

The duration effects of random vertical vibration on passenger discomfort were studied in a simulated section of an aircraft cabin configured to seat six persons in tourist-class style. Variables of the study included time of exposure (0.25 min to 60 min) and the rms amplitude of vibration (0.025g to 0.100g). The vibrations had a white noise spectrum with a bandwidth of 10 Hz centered at 5 Hz. Data indicate that the discomfort threshold occurred at an rms vertical acceleration level of 0.027g for all durations of vibration. However, for acceleration levels that exceeded the discomfort threshold, a systematic decrease in discomfort occurred as a function of increasing duration of vibration. For the range of accelerations used, the magnitude of the discomfort decrement was shown to be independent of acceleration level. The results suggest that discomfort from vertical vibration applied in the frequency range at which humans are most sensitive decreases with longer exposure, which is the opposite of the recommendation of the International Standard ISO 2631-1974 (E) Guide for the Evaluation of Human Exposure to Whole-Body Vibration.

Chronic stress effects and their reversibility on the Fallopian tubes and uterus in rats.

PubMed

Divyashree, S; Yajurvedi, H N

2018-01-01

The durational effects of chronic stress on the Fallopian tubes and uterus were studied by exposing rats to stressors in the form of restraint (1h) and forced swimming (15min) daily for 4, 8 or 12 weeks. One group of stressed rats from each time period was then maintained without exposure to stressors for a further 4 weeks to assess their ability to recover from stress. All time periods of stress exposure resulted in decreased weight of the body and Fallopian tubes; however, the relative weight of the uterus and serum concentrations of oestradiol and insulin increased significantly. The antioxidant potential was decreased with increased malondialdehyde concentrations in the Fallopian tubes following all durations of exposure and after 4 and 8 weeks of stress exposure in the uterus. Interestingly, rats stressed for 12 weeks showed an increase in serum testosterone concentration and antioxidant enzyme activities with a decrease in malondialdehyde concentration in the uterus. The antioxidant enzyme activities and malondialdehyde concentration in the Fallopian tubes of all recovery group rats were similar to stressed rats. However, in the uterus these parameters were similar to controls in recovery group rats after 4 weeks or 8 weeks of exposure, but after 12 weeks of stress exposure these parameters did not return to control levels following the recovery period. These results reveal, for the first time, that chronic stress elicits an irreversible decrease in antioxidant defence in the Fallopian tubes irrespective of exposure duration, whereas the uterus develops reversible oxidative stress under short-term exposure but increased antioxidant potential with endometrial proliferation following long-term exposure.

Lung Cancer and Elemental Carbon Exposure in Trucking Industry Workers

PubMed Central

Laden, Francine; Hart, Jaime E.; Davis, Mary E.; Eisen, Ellen A.; Smith, Thomas J.

2012-01-01

Background: Diesel exhaust has been considered to be a probable lung carcinogen based on studies of occupationally exposed workers. Efforts to define lung cancer risk in these studies have been limited in part by lack of quantitative exposure estimates. Objective: We conducted a retrospective cohort study to assess lung cancer mortality risk among U.S. trucking industry workers. Elemental carbon (EC) was used as a surrogate of exposure to engine exhaust from diesel vehicles, traffic, and loading dock operations. Methods: Work records were available for 31,135 male workers employed in the unionized U.S. trucking industry in 1985. A statistical model based on a national exposure assessment was used to estimate historical work-related exposures to EC. Lung cancer mortality was ascertained through the year 2000, and associations with cumulative and average EC were estimated using proportional hazards models. Results: Duration of employment was inversely associated with lung cancer risk consistent with a healthy worker survivor effect and a cohort composed of prevalent hires. After adjusting for employment duration, we noted a suggestion of a linear exposure–response relationship. For each 1,000-µg/m3 months of cumulative EC, based on a 5-year exposure lag, the hazard ratio (HR) was 1.07 [95% confidence interval (CI): 0.99, 1.15] with a similar association for a 10-year exposure lag [HR = 1.09 (95% CI: 0.99, 1.20)]. Average exposure was not associated with relative risk. Conclusions: Lung cancer mortality in trucking industry workers increased in association with cumulative exposure to EC after adjusting for negative confounding by employment duration. PMID:22739103

Sleep-Wake Actigraphy and Light Exposure During Spaceflight-Long

NASA Technical Reports Server (NTRS)

Czeisler, Charles A.; Barger, Laura K.; Wright, Kenneth P., Jr.; Ronda, Joseph

2009-01-01

Sleep-Wake Actigraphy and Light Exposure During Spaceflight-Long (Sleep-Long) will examine the effects of spaceflight and ambient light exposure on the sleep-wake cycles of the crew members during long-duration stays on the space station.

Response terminated displays unload selective attention

PubMed Central

Roper, Zachary J. J.; Vecera, Shaun P.

2013-01-01

Perceptual load theory successfully replaced the early vs. late selection debate by appealing to adaptive control over the efficiency of selective attention. Early selection is observed unless perceptual load (p-Load) is sufficiently low to grant attentional “spill-over” to task-irrelevant stimuli. Many studies exploring load theory have used limited display durations that perhaps impose artificial limits on encoding processes. We extended the exposure duration in a classic p-Load task to alleviate temporal encoding demands that may otherwise tax mnemonic consolidation processes. If the load effect arises from perceptual demands alone, then freeing-up available mnemonic resources by extending the exposure duration should have little effect. The results of Experiment 1 falsify this prediction. We observed a reliable flanker effect under high p-Load, response-terminated displays. Next, we orthogonally manipulated exposure duration and task-relevance. Counter-intuitively, we found that the likelihood of observing the flanker effect under high p-Load resides with the duration of the task-relevant array, not the flanker itself. We propose that stimulus and encoding demands interact to produce the load effect. Our account clarifies how task parameters differentially impinge upon cognitive processes to produce attentional “spill-over” by appealing to visual short-term memory as an additional processing bottleneck when stimuli are briefly presented. PMID:24399983

Response terminated displays unload selective attention.

PubMed

Roper, Zachary J J; Vecera, Shaun P

2013-01-01

Perceptual load theory successfully replaced the early vs. late selection debate by appealing to adaptive control over the efficiency of selective attention. Early selection is observed unless perceptual load (p-Load) is sufficiently low to grant attentional "spill-over" to task-irrelevant stimuli. Many studies exploring load theory have used limited display durations that perhaps impose artificial limits on encoding processes. We extended the exposure duration in a classic p-Load task to alleviate temporal encoding demands that may otherwise tax mnemonic consolidation processes. If the load effect arises from perceptual demands alone, then freeing-up available mnemonic resources by extending the exposure duration should have little effect. The results of Experiment 1 falsify this prediction. We observed a reliable flanker effect under high p-Load, response-terminated displays. Next, we orthogonally manipulated exposure duration and task-relevance. Counter-intuitively, we found that the likelihood of observing the flanker effect under high p-Load resides with the duration of the task-relevant array, not the flanker itself. We propose that stimulus and encoding demands interact to produce the load effect. Our account clarifies how task parameters differentially impinge upon cognitive processes to produce attentional "spill-over" by appealing to visual short-term memory as an additional processing bottleneck when stimuli are briefly presented.

The Influences of Exposure Pattern and Duration on Elimination Kinetics and Exposure Assessment of Tetrachloroethylene in Humans. Yeh-Chung Chien

EPA Pesticide Factsheets

The current investigation was designed and conducted to examine the body kinetic behaviors by means of breath analysis under various exposure conditions to test the validity of using exhaled breath as a biological marker of exposure.

Laser induced mortality of Anopheles stephensi mosquitoes

NASA Astrophysics Data System (ADS)

Keller, Matthew D.; Leahy, David J.; Norton, Bryan J.; Johanson, Threeric; Mullen, Emma R.; Marvit, Maclen; Makagon, Arty

2016-02-01

Small, flying insects continue to pose great risks to both human health and agricultural production throughout the world, so there remains a compelling need to develop new vector and pest control approaches. Here, we examined the use of short (<25 ms) laser pulses to kill or disable anesthetized female Anopheles stephensi mosquitoes, which were chosen as a representative species. The mortality of mosquitoes exposed to laser pulses of various wavelength, power, pulse duration, and spot size combinations was assessed 24 hours after exposure. For otherwise comparable conditions, green and far-infrared wavelengths were found to be more effective than near- and mid-infrared wavelengths. Pulses with larger laser spot sizes required lower lethal energy densities, or fluence, but more pulse energy than for smaller spot sizes with greater fluence. Pulse duration had to be reduced by several orders of magnitude to significantly lower the lethal pulse energy or fluence required. These results identified the most promising candidates for the lethal laser component in a system being designed to identify, track, and shoot down flying insects in the wild.

Summary of solar cell data from the Long Duration Exposure Facility (LDEF)

NASA Technical Reports Server (NTRS)

Hill, David C.; Rose, M. Frank

1994-01-01

The Long Duration Exposure Facility (LDEF) was composed of many separate experiments, some of which contained solar cells. These solar cells were distributed at various positions on the LDEF and, therefore, were exposed to the space environment with an orientational dependence. This report will address the space environmental effects on solar cells and solar cell assemblies (SCA's), including electrical interconnects and associated insulation blankets where flown in conjunction with solar cells.

Analysis of Silverized Teflon Thermal Control Material Flown on the Long Duration Exposure Facility

NASA Technical Reports Server (NTRS)

Pippin, H. Gary

1995-01-01

Silver backed teflon (Ag/FEP) material used for thermal control on the Long Duration Exposure Facility (LDEF) has been examined in detail. Optical, mechanical, and chemical properties were characterized for specimens exposed to a variety of space environmental conditions. Recession rates were determined for this material. Samples were obtained from virtually every LDEF location except the Earth-end. Atomic oxygen exposed regions changed from specular to diffusely reflective.

SOA does not Reveal the Absolute Time Course of Cognitive Processing in Fast Priming Experiments

PubMed Central

Tzur, Boaz; Frost, Ram

2007-01-01

Applying Bloch's law to visual word recognition research, both exposure duration of the prime and its luminance determine the prime's overall energy, and consequently determine the size of the priming effect. Nevertheless, experimenters using fast-priming paradigms traditionally focus only on the SOA between prime and target to reflect the absolute speed of cognitive processes under investigation. Some of the discrepancies in results regarding the time course of orthographic and phonological activation in word recognition research may be due to this factor. This hypothesis was examined by manipulating parametrically the luminance of the prime and its exposure duration, measuring their joint impact on masked repetition priming. The results show that small and non-significant priming effects can be more than tripled as a result of simply increasing luminance, when SOA is kept constant. Moreover, increased luminance may compensate for briefer exposure duration and vice versa. PMID:18379635

[Modulating effect of weak combined magnetic fields on duration of mealworm beetle Tenebrio molitor metamorphosis stage].

PubMed

Novikov, V V; Sheĭman, I M; Iablokova, E V; Fesenko, E E

2014-01-01

It is shown that an exposure of pupae of the mealworm beetle Tenebrio molitor to the combined static (42 μT) and very weak alternating (250 nT) magnetic fields exerts different influence, depending on the frequency of the alternating magnetic field, on duration of metamorphosis processes in these insects. For instance, an exposure of pupae to weak combined magnetic fields, adjusted to the frequency of ion cyclotron resonance for glutaminic acid (4,4 Hz), stimulates metamorphosis process--a transitional stage from pupae to imago lasts shorter. An inhibiting effect was observed when adjusted to the frequency of ion cyclotron resonance for Ca2 (32,2 Hz). At some frequencies this effect is not seen. For instance, an exposure at a frequency of ion cyclotron resonance for K+ (16,5 Hz) exerts no noticeable effect on the duration of the pupal metamorphosis stage.

An Algorithm for the Transport of Anisotropic Neutrons

NASA Technical Reports Server (NTRS)

Tweed, J.

2005-01-01

One major obstacle to human space exploration is the possible limitations imposed by the adverse effect of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar particle events (SPE) were of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated GCR exposures can be high. Because cancer induction rates increase behind low to rather large thicknesses of aluminum shielding, according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Therefore, a critical issue in the Human Exploration and Development of Space enterprise is cost effective mitigation of risk associated with ionizing radiation exposure. In order to estimate astronaut risk to GCR exposure and associated cancer risks and health hazards, it is necessary to do shield material studies. To determine an optimum radiation shield material it is necessary to understand nuclear interaction processes such as fragmentation and secondary particle production which is a function of energy dependent cross sections. This requires knowledge of material transmission characteristics either through laboratory testing or improved theoretical modeling. Here ion beam transport theory is of importance in that testing of materials in the laboratory environment generated by particle accelerators is a necessary step in materials development and evaluation for space use. The approximations used in solving the Boltzmann transport equation for the space setting are often not sufficient for laboratory work and those issues are a major emphasis of the present work.

Nitrous oxide-related postoperative nausea and vomiting depends on duration of exposure.

PubMed

Peyton, Philip J; Wu, Christine Yx

2014-05-01

Inclusion of nitrous oxide in the gas mixture has been implicated in postoperative nausea and vomiting (PONV) in numerous studies. However, these studies have not examined whether duration of exposure was a significant covariate. This distinction might affect the future place of nitrous oxide in clinical practice. PubMed listed journals reporting trials in which patients randomized to a nitrous oxide or nitrous oxide-free anesthetic for surgery were included, where the incidence of PONV within the first 24 postoperative hours and mean duration of anesthesia was reported. Meta-regression of the log risk ratio for PONV with nitrous oxide (lnRR PONVN2O) versus duration was performed. Twenty-nine studies in 27 articles met the inclusion criteria, randomizing 10,317 patients. There was a significant relationship between lnRR PONVN2O and duration (r = 0.51, P = 0.002). Risk ratio PONV increased 20% per hour of nitrous oxide after 45 min. The number needed to treat to prevent PONV by avoiding nitrous oxide was 128, 23, and 9 where duration was less than 1, 1 to 2, and over 2 h, respectively. The risk ratio for the overall effect of nitrous oxide on PONV was 1.21 (CIs, 1.04-1.40); P = 0.014. This duration-related effect may be via disturbance of methionine and folate metabolism. No clinically significant effect of nitrous oxide on the risk of PONV exists under an hour of exposure. Nitrous oxide-related PONV should not be seen as an impediment to its use in minor or ambulatory surgery.

Sleep duration as a mediator between an alternating day and night shift work schedule and metabolic syndrome among female hospital employees.

PubMed

Korsiak, Jill; Tranmer, Joan; Day, Andrew; Aronson, Kristan J

2018-02-01

The main objective was to determine whether sleep duration on work shifts mediates the relationship between a current alternating day and night shift work schedule and metabolic syndrome among female hospital employees. The secondary objective was to assess whether cumulative lifetime shift work exposure was associated with metabolic syndrome. In this cross-sectional study of 294 female hospital employees, sleep duration was measured with the ActiGraph GT3X+. Shift work status was determined through self-report. Investigation of the total, direct and indirect effects between shift work, sleep duration on work shifts and metabolic syndrome was conducted using regression path analysis. Logistic regression was used to determine the association between cumulative shift work exposure and metabolic syndrome. Shift work is strongly associated with metabolic syndrome (OR Total =2.72, 95% CI 1.38 to 5.36), and the relationship is attenuated when work shift sleep duration is added to the model (OR Direct =1.18, 95% CI 0.49 to 2.89). Sleep duration is an important intermediate between shift work and metabolic syndrome (OR Indirect =2.25, 95% CI 1.27 to 4.26). Cumulative shift work exposure is not associated with metabolic syndrome in this population. Sleep duration mediates the association between a current alternating day-night shift work pattern and metabolic syndrome. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Effects of Long-Term Thermal Exposure on Commercially Pure Titanium Grade 2 Elevated-Temperature Tensile Properties

NASA Technical Reports Server (NTRS)

Ellis, David L.

2012-01-01

Elevated-temperature tensile testing of commercially pure titanium (CP Ti) Grade 2 was conducted for as-received commercially produced sheet and following thermal exposure at 550 and 650 K (531 and 711 F) for times up to 5000 h. The tensile testing revealed some statistical differences between the 11 thermal treatments, but most thermal treatments were statistically equivalent. Previous data from room temperature tensile testing was combined with the new data to allow regression and development of mathematical models relating tensile properties to temperature and thermal exposure. The results indicate that thermal exposure temperature has a very small effect, whereas the thermal exposure duration has no statistically significant effects on the tensile properties. These results indicate that CP Ti Grade 2 will be thermally stable and suitable for long-duration space missions.

Development and Seed Number in Indeterminate Soybean as Affected by Timing and Duration of Exposure to Long Photoperiods after Flowering

PubMed Central

Kantolic, Adriana G.; Slafer, Gustavo A.

2007-01-01

Background and Aims Long photoperiods from flowering to maturity have been found to delay reproductive development in soybean (Glycine max) and to increase the number of seeds per unit land area. This study was aimed to evaluate whether sensitivity to photoperiod after flowering (a) is quantitatively related to the length of exposure to long days and (b) persists throughout the whole pod-setting period. It was also evaluated whether seed number was related to changes in the duration of post-flowering phenophases. Methods Two field experiments were conducted with an indeterminate cultivar of soybean of maturity group V. In expt 1, photoperiods 2 h longer than natural daylength were applied during different numbers of days from the beginning pod stage (R3) onwards, while in expt 2 these photoperiod extensions were imposed during 9 consecutive days starting at different times between R3 and R6 (full seed) stages. Key Results There was a quantitative response of development to the number of cycles with a long photoperiod. The exposure to long photoperiods from R3 to R5 (beginning of seed growth) increased the duration of R3–R6 regardless of the timing of exposure. The stages of development comprised in the R3–R6 phase were delayed by current as well as by previous exposure to long days. A positive relationship was found between seed number and the duration of R3–R6, irrespective of the timing and length of exposure to the long photoperiod. Conclusions Sensitivity to photoperiod remained high during the reproductive period and was highly and positively coupled with the processes of generation of yield. PMID:17452381

Timing and Duration of Drug Exposure Affects Outcomes of a Drug-Nutrient Interaction During Ontogeny.

PubMed

Ling, Binbing; Aziz, Caroline; Wojnarowicz, Chris; Olkowski, Andrew; Alcorn, Jane

2010-10-14

Significant drug-nutrient interactions are possible when drugs and nutrients share the same absorption and disposition mechanisms. During postnatal development, the outcomes of drug-nutrient interactions may change with postnatal age since these processes undergo ontogenesis through the postnatal period. Our study investigated the dependence of a significant drug-nutrient interaction (cefepime-carnitine) on the timing and duration of drug exposure relative to postnatal age. Rat pups were administered cefepime (5 mg/kg) twice daily subcutaneously according to different dosing schedules (postnatal day 1-4, 1-8, 8-11, 8-20, or 1-20). Cefepime significantly reduced serum and heart L-carnitine levels in postnatal day 1-4, 1-8 and 8-11 groups and caused severe degenerative changes in ventricular myocardium in these groups. Cefepime also altered the ontogeny of several key L-carnitine homeostasis pathways. The qualitative and quantitative changes in levels of hepatic γ-butyrobetaine hydroxylase mRNA and activity, hepatic trimethyllysine hydroxlase mRNA, intestinal organic cation/carnitine transporter (Octn) mRNA, and renal Octn2 mRNA depended on when during postnatal development the cefepime exposure occurred and duration of exposure. Despite lower levels of heart L-carnitine in earlier postnatal groups, levels of carnitine palmitoyltransferase mRNA and activity, heart Octn2 mRNA and ATP levels in all treatment groups remained unchanged with cefepime exposure. However, changes in other high energy phosphate substrates were noted and reductions in the phosphocreatine/ATP ratio were found in rat pups with normal serum L-carnitine levels. In summary, our data suggest a significant drug-nutrient transport interaction in developing neonates, the nature of which depends on the timing and duration of exposure relative to postnatal age.

Timing and Duration of Drug Exposure Affects Outcomes of a Drug-Nutrient Interaction During Ontogeny

PubMed Central

Ling, Binbing; Aziz, Caroline; Wojnarowicz, Chris; Olkowski, Andrew; Alcorn, Jane

2010-01-01

Significant drug-nutrient interactions are possible when drugs and nutrients share the same absorption and disposition mechanisms. During postnatal development, the outcomes of drug-nutrient interactions may change with postnatal age since these processes undergo ontogenesis through the postnatal period. Our study investigated the dependence of a significant drug-nutrient interaction (cefepime-carnitine) on the timing and duration of drug exposure relative to postnatal age. Rat pups were administered cefepime (5 mg/kg) twice daily subcutaneously according to different dosing schedules (postnatal day 1-4, 1-8, 8-11, 8-20, or 1-20). Cefepime significantly reduced serum and heart L-carnitine levels in postnatal day 1-4, 1-8 and 8-11 groups and caused severe degenerative changes in ventricular myocardium in these groups. Cefepime also altered the ontogeny of several key L-carnitine homeostasis pathways. The qualitative and quantitative changes in levels of hepatic γ-butyrobetaine hydroxylase mRNA and activity, hepatic trimethyllysine hydroxlase mRNA, intestinal organic cation/carnitine transporter (Octn) mRNA, and renal Octn2 mRNA depended on when during postnatal development the cefepime exposure occurred and duration of exposure. Despite lower levels of heart L-carnitine in earlier postnatal groups, levels of carnitine palmitoyltransferase mRNA and activity, heart Octn2 mRNA and ATP levels in all treatment groups remained unchanged with cefepime exposure. However, changes in other high energy phosphate substrates were noted and reductions in the phosphocreatine/ATP ratio were found in rat pups with normal serum L-carnitine levels. In summary, our data suggest a significant drug-nutrient transport interaction in developing neonates, the nature of which depends on the timing and duration of exposure relative to postnatal age. PMID:27721360

Influence of long-term exposure to simulated acid rain on development, reproduction and acaricide susceptibility of the carmine spider mite, Tetranychus cinnabarinus

PubMed Central

Wang, Jin-Jun; Zhang, Jian-Ping; He, Lin; Zhao, Zhi-Mo

2006-01-01

Development, reproduction and acaricide susceptibility of Tetranychus cinnabarinus (Boisduvals) (Acari: Tetranychidae) were investigated after long-term (about 40 generations) exposure to various levels of acid rain; pH 2.5, 3.0, 4.0, and 5.6. Deionized water (pH 6.8) served as a control. The mites were reared on eggplant leaves at 28°C, 80%RH and a photoperiod of 14:10 (L:D) in the laboratory. The results showed that the duration of the immature stage was significantly affected by acid rain exposure. The shortest duration (8.90 days) was recorded for populations exposed to pH 5.6 acid rain, while the longest duration (9.37 days) occurred after exposure to pH 2.5 acid rain. Compared with the control population, adult longevity was shortened with an increase in acidity. Similarly, the oviposition duration was also shortened by an increase in acidity. Statistically, female fecundity did not differ significantly between pH 5.6, pH 4.0 and control populations, but did differ significantly between the control population and those exposed to pH 2.5 and pH 3.0 acid rain. This suggested that the mite suffered reproductive defects after long-term exposure to acid rain with higher acidity (pH 2.5 and 3.0). The intrinsic rate of increase among different populations was not significantly affected, but the net reproductive rate of populations exposed to pH 2.5 and 3.0 acid rain was significantly less than pH4.0, 5.6, and control populations. Bioassay results showed that after long-term exposure to acid rain, susceptibility of the mites to two acaricides, dichlorvos and fenpropathrin, did not change significantly. PMID:19537978

Distribution of kerosene components in rats following dermal exposure.

PubMed

Tsujino, Y; Hieda, Y; Kimura, K; Eto, H; Yakabe, T; Takayama, K; Dekio, S

2002-08-01

The systemic distribution of kerosene components in blood and tissues was analysed in rats following dermal exposure. Four types of trimethylbenzenes (TMBs) and aliphatic hydrocarbons (AHCs) with carbon numbers 9-16 (C(9)-C(16)) were analysed as major kerosene components by capillary gas chromatography/mass spectrometry (GC/MS). The kerosene components were detected in blood and all tissues after a small piece of cotton soaked with kerosene was applied to the abdominal skin. The amounts of TMBs detected were higher than those of AHCs. Greater increases in TMB levels were found in adipose tissue in an exposure duration-dependent manner. The amounts of TMBs detected were only at trace levels following post-mortem dermal exposure to kerosene. These findings suggest that kerosene components were absorbed percutaneously and distributed to various organs via the blood circulation. Post-mortem or ante-mortem exposure to kerosene could be distinguished when the exposure duration was relatively long. Adipose tissue would seem to be the most useful for estimating the degree of kerosene exposure.

A PCT algorithm for discontinuation of antibiotic therapy is a cost-effective way to reduce antibiotic exposure in adult intensive care patients with sepsis.

PubMed

Kip, Michelle M A; Kusters, Ron; IJzerman, Maarten J; Steuten, Lotte M G

2015-01-01

Procalcitonin (PCT) is a specific marker for differentiating bacterial from non-infective causes of inflammation. It can be used to guide initiation and duration of antibiotic therapy in intensive care unit (ICU) patients with suspected sepsis, and might reduce the duration of hospital stay. Limiting antibiotic treatment duration is highly important because antibiotic over-use may cause patient harm, prolonged hospital stay, and resistance development. Several systematic reviews show that a PCT algorithm for antibiotic discontinuation is safe, but upfront investment required for PCT remains an important barrier against implementation. The current study investigates to what extent this PCT algorithm is a cost-effective use of scarce healthcare resources in ICU patients with sepsis compared to current practice. A decision tree was developed to estimate the health economic consequences of the PCT algorithm for antibiotic discontinuation from a Dutch hospital perspective. Input data were obtained from a systematic literature review. When necessary, additional information was gathered from open interviews with clinical chemists and intensivists. The primary effectiveness measure is defined as the number of antibiotic days, and cost-effectiveness is expressed as incremental costs per antibiotic day avoided. The PCT algorithm for antibiotic discontinuation is expected to reduce hospital spending by circa € 3503 per patient, indicating savings of 9.2%. Savings are mainly due to reductions in length of hospital stay, number of blood cultures performed, and, importantly, days on antibiotic therapy. Probabilistic and one-way sensitivity analyses showed the model outcome to be robust against changes in model inputs. Proven safe, a PCT algorithm for antibiotic discontinuation is a cost-effective means of reducing antibiotic exposure in adult ICU patients with sepsis, compared to current practice. Additional resources required for PCT are more than offset by downstream cost savings. This finding is highly important given the aim of preventing widespread antibiotic resistance.

Occupational and environmental exposure to pesticides and cytokine pathways in chronic diseases (Review).

PubMed

Gangemi, Silvia; Gofita, Eliza; Costa, Chiara; Teodoro, Michele; Briguglio, Giusi; Nikitovic, Dragana; Tzanakakis, George; Tsatsakis, Aristides M; Wilks, Martin F; Spandidos, Demetrios A; Fenga, Concettina

2016-10-01

Pesticides can exert numerous effects on human health as a consequence of both environmental and occupational exposures. The available knowledge base suggests that exposure to pesticides may result in detrimental reproductive changes, neurological dysfunction and several chronic disorders, which are defined by slow evolution and long-term duration. Moreover, an ever increasing amount of data have identified an association between exposure to pesticides and the harmful effects on the immune system. The real impact of alterations in humoral cytokine levels on human health, in particular in the case of chronic diseases, is still unclear. To date, studies have suggested that although exposure to pesticides can affect the immune system functionally, the development of immune disorders depends on the dose and duration of exposure to pesticides. However, many of the respective studies exhibit limitations, such as a lack of information on exposure levels, differences in the pesticide administration procedures, difficulty in characterizing a prognostic significance to the weak modifications often observed and the interpretation of obtained results. The main challenge is not just to understand the role of individual pesticides and their combinations, but also to determine the manner and the duration of exposure, as the toxic effects on the immune system cannot be separated from these considerations. There is a clear need for more well‑designed and standardized epidemiological and experimental studies to recognize the exact association between exposure levels and toxic effects and to identify useful biomarkers of exposure. This review focuses on and critically discusses the immunotoxicity of pesticides and the impact of cytokine levels on health, focusing on the development of several chronic diseases.

Occupational and environmental exposure to pesticides and cytokine pathways in chronic diseases (Review)

PubMed Central

Gangemi, Silvia; Gofita, Eliza; Costa, Chiara; Teodoro, Michele; Briguglio, Giusi; Nikitovic, Dragana; Tzanakakis, George; Tsatsakis, Aristides M.; Wilks, Martin F.; Spandidos, Demetrios A.; Fenga, Concettina

2016-01-01

Pesticides can exert numerous effects on human health as a consequence of both environmental and occupational exposures. The available knowledge base suggests that exposure to pesticides may result in detrimental reproductive changes, neurological dysfunction and several chronic disorders, which are defined by slow evolution and long-term duration. Moreover, an ever increasing amount of data have identified an association between exposure to pesticides and the harmful effects on the immune system. The real impact of alterations in humoral cytokine levels on human health, in particular in the case of chronic diseases, is still unclear. To date, studies have suggested that although exposure to pesticides can affect the immune system functionally, the development of immune disorders depends on the dose and duration of exposure to pesticides. However, many of the respective studies exhibit limitations, such as a lack of information on exposure levels, differences in the pesticide administration procedures, difficulty in characterizing a prognostic significance to the weak modifications often observed and the interpretation of obtained results. The main challenge is not just to understand the role of individual pesticides and their combinations, but also to determine the manner and the duration of exposure, as the toxic effects on the immune system cannot be separated from these considerations. There is a clear need for more well-designed and standardized epidemiological and experimental studies to recognize the exact association between exposure levels and toxic effects and to identify useful biomarkers of exposure. This review focuses on and critically discusses the immunotoxicity of pesticides and the impact of cytokine levels on health, focusing on the development of several chronic diseases. PMID:27600395

Electromagnetic navigation reduces surgical time and radiation exposure for proximal interlocking in retrograde femoral nailing.

PubMed

Somerson, Jeremy S; Rowley, David; Kennedy, Chad; Buttacavoli, Frank; Agarwal, Animesh

2014-07-01

To compare the time required for proximal locking screw placement between a standard freehand technique and the navigated technique, and to quantify the reduction in ionizing radiation exposure. A fresh frozen cadaver model was used for 48 proximal interlocking screw procedures. Each procedure consisted of insertion of 2 anteroposterior locking screws. Standard fluoroscopic technique was used for 24 procedures, and an electromagnetic navigation system was used for the remaining 24 procedures. Procedure duration was recorded using an electronic timer and radiation doses were documented. Mean total insertion time for both proximal interlocking screws was 405 ± 165.7 seconds with the freehand technique and 311 ± 78.3 seconds in the navigation group (P = 0.002). All procedures resulted in successful locking screw placement. Mean ionizing radiation exposure time for proximal locking was 29.5 ± 12.8 seconds. Proximal locking screw insertion using the navigation technique evaluated in this work was significantly faster than the standard fluoroscopic method. The navigated technique is effective and has the potential to prevent ionizing radiation exposure.

Recent Developments in Three Dimensional Radiation Transport Using the Green's Function Technique

NASA Technical Reports Server (NTRS)

Rockell, Candice; Tweed, John; Blattnig, Steve R.; Mertens, Christopher J.

2010-01-01

In the future, astronauts will be sent into space for longer durations of time compared to previous missions. The increased risk of exposure to dangerous radiation, such as Galactic Cosmic Rays and Solar Particle Events, is of great concern. Consequently, steps must be taken to ensure astronaut safety by providing adequate shielding. In order to better determine and verify shielding requirements, an accurate and efficient radiation transport code based on a fully three dimensional radiation transport model using the Green's function technique is being developed

Menopausal hormone therapy and breast cancer phenotype: does dose matter?

PubMed

Garwood, Elisabeth R; Kumar, Anjali S; Shim, Veronica

2008-09-01

Duration and type of menopausal hormone therapy (HT) has been associated with increased breast cancer risk and the development of estrogen receptor (ER)-positive tumors. The effect of HT dose on breast cancer tumor characteristics remains undefined. We sought to determine if HT dosing regimens influence breast cancer phenotype. We conducted a retrospective review of incident female breast cancers occurring in the year 2003 listed in the Kaiser Permanente Northern California Cancer Registry. Type of HT, dose, number of tablets dispensed, tumor phenotype, stage, grade, and histology were obtained from electronic records for women aged >/=50 years who had more than 1 year of uninterrupted pharmacy data (n = 1701). A dose index of HT exposure was created and odds ratios were used to determine if tumor phenotype varied between exposure groups. These results were compared with a previously published analysis of HT duration on tumor phenotype conducted with the same dataset. The cumulative effect of estrogen and progesterone hormone therapy as calculated by factoring both dose and duration of HT use prior to breast cancer diagnosis did not reveal any new associations that were not previously identified by analysis of HT duration of exposure alone. Low-dose-index combination-HT users were less likely to have tumors with an ER-positive phenotype. An overall trend developed in which low- and high-dose-index exposed women had the lowest rates of ER- and progesterone receptor (PR) -positive tumors. Duration of use is an adequate surrogate for determining overall exposure to HT when considering the effect of HT on breast cancer phenotype.

In utero azathioprine exposure and increased utilization of special educational services in children born to mothers with systemic lupus erythematosus

PubMed Central

Marder, Wendy; Ganser, Martha A; Romero, Vivian; Hyzy, Margaret A; Gordon, Caroline; McCune, WJ; Somers, Emily C

2012-01-01

Objective Azathioprine (AZA) is recognized among immunosuppressive medications as relatively safe during pregnancy for women with systemic lupus erythematosus (SLE) requiring aggressive treatment. This pilot study aimed to determine whether SLE therapy during pregnancy was associated with developmental delays in offspring. Methods This cohort study included SLE patients with at least one live birth post-diagnosis. Medical histories were obtained via interviews and chart review. Multiple logistic regression was used to examine associations between SLE therapy during pregnancy and maternal report of special educational (SE) requirements (as proxy for developmental delays) among offspring. Propensity scoring (incorporating corticosteroid use, lupus flare, and lupus nephritis) was used to account for disease severity. Results Of 60 eligible offspring from 38 mothers, 15 required SE services, the most common indication for which was speech delay. 7 of the 13 (54%) children with in utero AZA exposure utilized SE services versus 8 of 47 (17%) non-exposed (p<0.05). After adjustment for pregnancy duration, small for gestational age, propensity score, maternal education and antiphospholipid antibody syndrome, AZA was significantly associated with SE utilization occurring from age 2 onward (OR 6.6, 95% CI 1.0, 43.3), and bordered significance for utilization at any age or age <2 years. Conclusions AZA exposure during SLE pregnancy was independently associated with increased SE utilization in offspring, after controlling for confounders. Further research is indicated to fully characterize developmental outcomes among offspring with in utero AZA exposure. Vigilance and early interventions for suspected developmental delays among exposed offspring may be warranted. PMID:23139238

Quantitative microbial risk assessment model for Legionnaires' disease: assessment of human exposures for selected spa outbreaks.

PubMed

Armstrong, Thomas W; Haas, Charles N

2007-08-01

Evaluation of a quantitative microbial risk assessment (QMRA) model for Legionnaires' disease (LD) required Legionella exposure estimates for several well-documented LD outbreaks. Reports for a whirlpool spa and two natural spring spa outbreaks provided data for the exposure assessment, as well as rates of infection and mortality. Exposure estimates for the whirlpool spa outbreak employed aerosol generation, water composition, exposure duration data, and building ventilation parameters with a two-zone model. Estimates for the natural hot springs outbreaks used bacterial water to air partitioning coefficients and exposure duration information. The air concentration and dose calculations used input parameter distributions with Monte Carlo simulations to estimate exposures as probability distributions. The assessment considered two sets of assumptions about the transfer of Legionella from the water phase to the aerosol emitted from the whirlpool spa. The estimated air concentration near the whirlpool spa was 5 to 18 colony forming units per cubic meter (CFU/m(3)) and 50 to 180 CFU/m(3) for each of the alternate assumptions. The estimated 95th percentile ranges of Legionella dose for workers within 15 m of the whirlpool spa were 0.13-3.4 CFU and 1.3-34.5 CFU, respectively. The modeling for hot springs Spas 1 and 2 resulted in estimated arithmetic mean air concentrations of 360 and 17 CFU/m(3), respectively, and 95 percentile ranges for Legionella dose of 28 to 67 CFU and 1.1 to 3.7 CFU, respectively. The Legionella air concentration estimates fall in the range of limited reports on air concentrations of Legionella (0.33 to 190 CFU/m(3)) near showers, aerated faucets, and baths during filling with Legionella-contaminated water. These measurements may provide some indication that the estimates are of a reasonable magnitude, but they do not clarify the exposure estimates accuracy, since they were not obtained during LD outbreaks. Further research to improve the data used for the Legionella exposure assessment would strengthen the results. Several of the primary additional data needs include improved data for bacterial water to air partitioning coefficients, better accounting of time-activity-distance patterns and exposure potential in outbreak reports, and data for Legionella-containing aerosol viability decay instead of loss of capability for growth in culture.

Assessment of exposures to fecally-contaminated recreational water

EPA Science Inventory

Exposure to fecally-contaminated recreational waters can pose a health risk to swimmers and other recreators. Since 2003, we have interviewed nearly 27,000 respondents at seven beaches impacted by treated sewage discharge. Information was collected about the duration and exposure...

Materials for Shielding Astronauts from the Hazards of Space Radiations

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Cucinotta, F. A.; Miller, J.; Shinn, J. L.; Thibeault, S. A.; Singleterry, R. C.; Simonsen, L. C.; Kim, M. H.

1997-01-01

One major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle (SEP) events was of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated exposures can be high. Because cancer induction rates increase behind low to rather large thickness of aluminum shielding according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Preliminary studies indicate that materials with high hydrogen content and low atomic number constituents are most efficient in protecting the astronauts. This occurs for two reasons: the hydrogen is efficient in breaking up the heavy GCR ions into smaller less damaging fragments and the light constituents produce few secondary radiations (especially few biologically damaging neutrons). An overview of the materials related issues and their impact on human space exploration will be given.

The Emergence of Frequency Effects in Eye Movements

ERIC Educational Resources Information Center

Vanyukov, Polina M.; Warren, Tessa; Wheeler, Mark E.; Reichle, Erik D.

2012-01-01

A visual search experiment employed strings of Landolt "C"s to examine how the gap size of and frequency of exposure to distractor strings affected eye movements. Increases in gap size were associated with shorter first-fixation durations, gaze durations, and total times, as well as fewer fixations. Importantly, both the number and duration of…

Assessing Residential Exposure Risk from Spills of Flowback Water from Marcellus Shale Hydraulic Fracturing Activity

PubMed Central

Abualfaraj, Noura; Olson, Mira S.

2018-01-01

Identifying sources of concern and risk from shale gas development, particularly from the hydraulic fracturing process, is an important step in better understanding sources of uncertainty within the industry. In this study, a risk assessment of residential exposure pathways to contaminated drinking water is carried out. In this model, it is assumed that a drinking water source is contaminated by a spill of flowback water; probability distributions of spill size and constituent concentrations are fit to historical datasets and Monte Carlo simulation was used to calculate a distribution of risk values for two scenarios: (1) use of a contaminated reservoir for residential drinking water supply and (2) swimming in a contaminated pond. The swimming scenario did not produce risks of concern from a single exposure of 1 h duration, but 11 such 1-h exposures did produce risks of 10−6 due to radionuclide exposure. The drinking water scenario over a 30-year exposure duration produced cancer risk values exceeding 10−6 for arsenic, benzene, benzo(a)pyrene, heptachlor, heptachlor epoxide, pentachlorophenol, and vinyl chloride. However, this extended exposure duration is probably not realistic for exposure by a spill event. Radionuclides produced risks in the residential drinking water scenario of 10−6 in just 8 h, a much more realistic timeline for continual exposure due to a spill event. In general, for contaminants for which inhalation exposure was applicable, this pathway produced the highest risks with exposure from ingestion posing the next greatest risk to human health followed by dermal absorption (or body emersion for radionuclides). Considering non-carcinogenic effects, only barium and thallium exceed target limits, where the ingestion pathway seems to be of greater concern than dermal exposure. Exposure to radionuclides in flowback water, particularly through the inhalation route, poses a greater threat to human health than other contaminants examined in this assessment and should be the focus of risk assessment and risk mitigation efforts. PMID:29641504

Assessing Residential Exposure Risk from Spills of Flowback Water from Marcellus Shale Hydraulic Fracturing Activity.

PubMed

Abualfaraj, Noura; Gurian, Patrick L; Olson, Mira S

2018-04-11

Identifying sources of concern and risk from shale gas development, particularly from the hydraulic fracturing process, is an important step in better understanding sources of uncertainty within the industry. In this study, a risk assessment of residential exposure pathways to contaminated drinking water is carried out. In this model, it is assumed that a drinking water source is contaminated by a spill of flowback water; probability distributions of spill size and constituent concentrations are fit to historical datasets and Monte Carlo simulation was used to calculate a distribution of risk values for two scenarios: (1) use of a contaminated reservoir for residential drinking water supply and (2) swimming in a contaminated pond. The swimming scenario did not produce risks of concern from a single exposure of 1 h duration, but 11 such 1-h exposures did produce risks of 10 -6 due to radionuclide exposure. The drinking water scenario over a 30-year exposure duration produced cancer risk values exceeding 10 -6 for arsenic, benzene, benzo(a)pyrene, heptachlor, heptachlor epoxide, pentachlorophenol, and vinyl chloride. However, this extended exposure duration is probably not realistic for exposure by a spill event. Radionuclides produced risks in the residential drinking water scenario of 10 -6 in just 8 h, a much more realistic timeline for continual exposure due to a spill event. In general, for contaminants for which inhalation exposure was applicable, this pathway produced the highest risks with exposure from ingestion posing the next greatest risk to human health followed by dermal absorption (or body emersion for radionuclides). Considering non-carcinogenic effects, only barium and thallium exceed target limits, where the ingestion pathway seems to be of greater concern than dermal exposure. Exposure to radionuclides in flowback water, particularly through the inhalation route, poses a greater threat to human health than other contaminants examined in this assessment and should be the focus of risk assessment and risk mitigation efforts.

Towards Standardization of X-ray Beam Filters in Digital Mammography and Digital Breast Tomosynthesis: Monte Carlo simulations and analytical modelling

PubMed Central

Shrestha, Suman; Vedantham, Srinivasan; Karellas, Andrew

2017-01-01

In digital breast tomosynthesis and digital mammography, the x-ray beam filter material and thickness vary between systems. Replacing K-edge filters with Al was investigated with the intent to reduce exposure duration and to simplify system design. Tungsten target x-ray spectra were simulated with K-edge filters (50μm Rh; 50μm Ag) and Al filters of varying thickness. Monte Carlo simulations were conducted to quantify the x-ray scatter from various filters alone, scatter-to-primary ratio (SPR) with compressed breasts, and to determine the radiation dose to the breast. These data were used to analytically compute the signal-difference-to-noise ratio (SDNR) at unit (1 mGy) mean glandular dose (MGD) for W/Rh and W/Ag spectra. At SDNR matched between K-edge and Al filtered spectra, the reductions in exposure duration and MGD were quantified for three strategies: (i) fixed Al thickness and matched tube potential in kilovolts (kV); (ii) fixed Al thickness and varying the kV to match the half-value layer (HVL) between Al and K-edge filtered spectra; and, (iii) matched kV and varying the Al thickness to match the HVL between Al and K-edge filtered spectra. Monte Carlo simulations indicate that the SPR with and without the breast were not different between Al and K-edge filters. Modelling for fixed Al thickness (700μm) and kV matched to K-edge filtered spectra, identical SDNR was achieved with 37–57% reduction in exposure duration and with 2–20% reduction in MGD, depending on breast thickness. Modelling for fixed Al thickness (700μm) and HVL matched by increasing the kV over [0,4] range, identical SDNR was achieved with 62–65% decrease in exposure duration and with 2–24% reduction in MGD, depending on breast thickness. For kV and HVL matched to K-edge filtered spectra by varying Al filter thickness over [700,880]μm range, identical SDNR was achieved with 23–56% reduction in exposure duration and 2–20% reduction in MGD, depending on breast thickness. These simulations indicate that increased fluence with Al filter of fixed or variable thickness substantially decreases exposure duration while providing for similar image quality with moderate reduction in MGD. PMID:28075335

Astronaut Biography Project for Countermeasures of Human Behavior and Performance Risks in Long Duration Space Flights

NASA Technical Reports Server (NTRS)

Banks, Akeem

2012-01-01

This final report will summarize research that relates to human behavioral health and performance of astronauts and flight controllers. Literature reviews, data archival analyses, and ground-based analog studies that center around the risk of human space flight are being used to help mitigate human behavior and performance risks from long duration space flights. A qualitative analysis of an astronaut autobiography was completed. An analysis was also conducted on exercise countermeasure publications to show the positive affects of exercise on the risks targeted in this study. The three main risks targeted in this study are risks of behavioral and psychiatric disorders, risks of performance errors due to poor team performance, cohesion, and composition, and risks of performance errors due to sleep deprivation, circadian rhythm. These three risks focus on psychological and physiological aspects of astronauts who venture out into space on long duration space missions. The purpose of this research is to target these risks in order to help quantify, identify, and mature countermeasures and technologies required in preventing or mitigating adverse outcomes from exposure to the spaceflight environment

Active shielding for long duration interplanetary manned missions

NASA Astrophysics Data System (ADS)

Spillantini, Piero

The problem of protecting astronauts from the cosmic rays action in unavoidable and was therefore preliminary studied by many space agencies. In Europe, in the years 2002-2004, ESA supported two works on this thematic: a topical team in the frame of the ‘life and physical sciences' and a study, assigned by tender, of the ‘radiation exposure and mission strategies for interplanetary manned missions to Moon and Mars'. In both studies it was concluded that, while the protection from solar cosmic rays can relay on the use of passive absorbers, for long duration missions the astronauts must be protected from the much more energetic galactic cosmic rays during the whole duration of the mission. This requires the protection of a large habitat where they could live and work, and not a temporary small volume shelter, and the use of active shielding is therefore mandatory. The possibilities offered by using superconducting magnets were discussed, and the needed R&D recommended. The technical development occurred in the meantime and the evolution of the panorama of the possible interplanetary missions in the near future require to revise these pioneer studies and think of the problem at a scale allowing long human permanence in ‘deep' space, and not for a relatively small number of dedicated astronauts but also for citizens conducting there ‘normal' activities.

Quantification of Reduction in Forced Vital Capacity of Sand Stone Quarry Workers

PubMed Central

Singh, Suresh Kumar; Chowdhary, G. R.; Chhangani, V. D.; Purohit, Gopal

2007-01-01

This study assessed the reduction in forced vital capacity of lungs of sand stone quarry workers exposed to high respirable suspended particulate concentration. The sand stone quarry workers are engaged in different type of activities like drilling, loading and dressing. These different working places have different concentration of RSPM and these workers are exposed to different concentration of RSPM. It is found that exposure duration and exposure concentrations are main factors responsible to damage respiratory tract of worker. It is also revealed from the study that most of the workers are suffering from silicosis if the exposure duration is more than 15 years. PMID:18180540

Marked depression of time interval between fertilization period and hatching period following exposure to low-dose X-rays in zebrafish.

PubMed

Miyachi, Yukihisa; Kanao, Tomoko; Okamoto, Takehito

2003-10-01

In recent years there has been growing concern over the stimulating effects of very low-dose X-rays. Our laboratory had observed that zebrafish irradiated with low-dose X-rays tended to emerge earlier than sham controls. This observation led us to quantitatively examine the effects of low-dose X irradiation on a series of stages of development in the zebrafish. The embryos were fertilized simultaneously in vitro and incubated at an optimal temperature without crowding. Following exposure of the cleavage period (1.5 h after fertilization) to 0.025-Gy X-rays, the duration to hatching was slightly shorter than that of the sham controls. This tendency was increased when the X-ray exposure occurred during the blastula period (3.5 h). In these embryos, the duration to hatching decreased significantly by an average of 6 h sooner than for sham controls. No differences in duration to hatching were seen when irradiation was given during either the zygote period (45 min) or the segmentation period (12 h). On the contrary, upon exposure to 0.5-Gy X-rays during the blastula period, the duration to hatching increased significantly relative to that of sham controls. These results suggest that the radiation-induced early hatching effect is observed for low doses of X-rays.

Effect of Electromagnetic Waves from Mobile Phones on Spermatogenesis in the Era of 4G-LTE

PubMed Central

Oh, Jong Jin; Byun, Seok-Soo; Lee, Sang Eun; Choe, Gheeyoung

2018-01-01

Objective To investigate the effect of long duration exposure to electromagnetic field from mobile phones on spermatogenesis in rats using 4G-LTE. Methods Twenty Sprague-Dawley male rats were placed into 4 groups according to the intensity and exposure duration: Group 1 (sham procedure), Group 2 (3 cm distance + 6 h exposure daily), Group 3 (10 cm distance + 18 h exposure daily), and Group 4 (3 cm distance + 18 h exposure daily). After 1 month, we compared sperm parameters and histopathological findings of the testis. Results The mean spermatid count (×106/ml) was 398.6 in Group 1, 365.40 in Group 2, 354.60 in Group 3, and 298.60 in Group 4 (p = 0.041). In the second review, the mean count of spermatogonia in Group 4 (43.00) was significantly lower than in Group 1 (57.00) and Group 2 (53.40) (p < 0.001 and p = 0.010, resp.). The sum of the germ cell counts was decreased in Group 4 compared to Groups 1, 2, and 3 (p = 0.032). The mean Leydig cell count was significantly decreased in Group 4 (p < 0.001). Conclusions The longer exposure duration of electromagnetic field decreased the spermatogenesis. Our findings warrant further investigations on the potential effects of EMF from mobile phones on male fertility. PMID:29789776

Increased lung function decline in blue-collar workers exposed to welding fumes.

PubMed

Thaon, Isabelle; Demange, Valérie; Herin, Fabrice; Touranchet, Annie; Paris, Christophe

2012-07-01

There is no consensus at the present time about the effect of welding on lung function decline. This study compared lung function decline between blue-collar workers exposed and not exposed to welding fumes in a French longitudinal cohort of 21,238 subjects aged 37 to 52 years at inclusion. Medical data, occupation, sector of activity, and spirometry were recorded twice by occupational physicians in 1990 and 1995. A job-exposure matrix was used to identify 503 male blue-collar workers exposed to welding fumes and 709 control subjects and to define the weekly duration of exposure to welding fumes. Baseline lung function parameters were higher in workers exposed to welding fumes than in control subjects. After a 5-year follow-up, welding-fume exposure was associated with a nonsignificant decline in FVC (P = .06) and FEV(1) (P = .07) after adjustment for age, pack-years, BMI, and baseline value of the parameter. A significant accelerated decline in FEV(1) (P = .046) was also observed in never smokers exposed to welding fumes. An “exposure-response” relationship was observed between FEV(1) decline and weekly duration of exposure to welding fumes in nonsmokers but not in smokers. Blue-collar workers exposed to welding fumes showed accelerated decline in lung function, which, in nonsmokers, was related to weekly duration of exposure.

Effect of Electromagnetic Waves from Mobile Phones on Spermatogenesis in the Era of 4G-LTE.

PubMed

Oh, Jong Jin; Byun, Seok-Soo; Lee, Sang Eun; Choe, Gheeyoung; Hong, Sung Kyu

2018-01-01

To investigate the effect of long duration exposure to electromagnetic field from mobile phones on spermatogenesis in rats using 4G-LTE. Twenty Sprague-Dawley male rats were placed into 4 groups according to the intensity and exposure duration: Group 1 (sham procedure), Group 2 (3 cm distance + 6 h exposure daily), Group 3 (10 cm distance + 18 h exposure daily), and Group 4 (3 cm distance + 18 h exposure daily). After 1 month, we compared sperm parameters and histopathological findings of the testis. The mean spermatid count (×10 6 /ml) was 398.6 in Group 1, 365.40 in Group 2, 354.60 in Group 3, and 298.60 in Group 4 ( p = 0.041). In the second review, the mean count of spermatogonia in Group 4 (43.00) was significantly lower than in Group 1 (57.00) and Group 2 (53.40) ( p < 0.001 and p = 0.010, resp.). The sum of the germ cell counts was decreased in Group 4 compared to Groups 1, 2, and 3 ( p = 0.032). The mean Leydig cell count was significantly decreased in Group 4 ( p < 0.001). The longer exposure duration of electromagnetic field decreased the spermatogenesis. Our findings warrant further investigations on the potential effects of EMF from mobile phones on male fertility.

Toxicological safeguards in the manned Mars missions

NASA Technical Reports Server (NTRS)

Coleman, Martin E.

1986-01-01

Safeguards against toxic chemical exposures during manned Mars missions (MMMs) will be important for the maintenance of crew health and the accomplishment of mission objectives. Potential sources include offgassing, thermodegradation or combustion of materials, metabolic products of crew members, and escape of chemical from containment. Spacecraft maximum allowable concentration (SMAC) limits will have to be established for potential contaminants during the MMMs. The following factors will be used in establishing these limits: duration of mission, simultaneous exposure to other contaminants, deconditioning of crew members after long periods of reduced gravity, and simultaneous exposure to ionizing radiation. Atmospheric contaminant levels in all compartments of the transit spacecraft and Manned Mars Station (MMS) will be monitored at frequent intervals with a real time analyzer. This analyzer will be highly automated, requiring minimal crew time and expertise. The atmospheric analyzer will find other usages during the MMMs such as analyzing Martian atmospheres and soils, exhaled breath and body fluids of crew members, and reaction products in chemical processing facilities.

Pooling job physical exposure data from multiple independent studies in a consortium study of carpal tunnel syndrome

PubMed Central

Kapellusch, Jay M.; Garg, Arun; Bao, Stephen S.; Silverstein, Barbara A.; Burt, Susan E.; Dale, Ann Marie; Evanoff, Bradley A.; Gerr, Frederic E.; Harris-Adamson, Carisa; Hegmann, Kurt T.; Merlino, Linda A.; Rempel, David M.

2015-01-01

Pooling data from different epidemiological studies of musculoskeletal disorders (MSDs) is necessary to improve statistical power and to more precisely quantify exposure–response relationships for MSDs. The pooling process is difficult and time-consuming, and small methodological differences could lead to different exposure–response relationships. A subcommittee of a six-study research consortium studying carpal tunnel syndrome: (i) visited each study site, (ii) documented methods used to collect physical exposure data and (iii) determined compatibility of exposure variables across studies. Certain measures of force, frequency of exertion and duty cycle were collected by all studies and were largely compatible. A portion of studies had detailed data to investigate simultaneous combinations of force, frequency and duration of exertions. Limited compatibility was found for hand/wrist posture. Only two studies could calculate compatible Strain Index scores, but Threshold Limit Value for Hand Activity Level could be determined for all studies. Challenges of pooling data, resources required and recommendations for future researchers are discussed. PMID:23697792

Health and efficiency in trimix versus air breathing in compressed air workers.

PubMed

Van Rees Vellinga, T P; Verhoeven, A C; Van Dijk, F J H; Sterk, W

2006-01-01

The Western Scheldt Tunneling Project in the Netherlands provided a unique opportunity to evaluate the effects of trimix usage on the health of compressed air workers and the efficiency of the project. Data analysis addressed 318 exposures to compressed air at 3.9-4.4 bar gauge and 52 exposures to trimix (25% oxygen, 25% helium, and 50% nitrogen) at 4.6-4.8 bar gauge. Results revealed three incidents of decompression sickness all of which involved the use of compressed air. During exposure to compressed air, the effects of nitrogen narcosis were manifested in operational errors and increased fatigue among the workers. When using trimix, less effort was required for breathing, and mandatory decompression times for stays of a specific duration and maximum depth were considerably shorter. We conclude that it might be rational--for both medical and operational reasons--to use breathing gases with lower nitrogen fractions (e.g., trimix) for deep-caisson work at pressures exceeding 3 bar gauge, although definitive studies are needed.

Intracellular Retention of ABL Kinase Inhibitors Determines Commitment to Apoptosis in CML Cells

PubMed Central

Dziadosz, Marek; Schnöder, Tina; Heidel, Florian; Schemionek, Mirle; Melo, Junia V.; Kindler, Thomas; Müller-Tidow, Carsten; Koschmieder, Steffen; Fischer, Thomas

2012-01-01

Clinical development of imatinib in CML established continuous target inhibition as a paradigm for successful tyrosine kinase inhibitor (TKI) therapy. However, recent reports suggested that transient potent target inhibition of BCR-ABL by high-dose TKI (HD-TKI) pulse-exposure is sufficient to irreversibly commit cells to apoptosis. Here, we report a novel mechanism of prolonged intracellular TKI activity upon HD-TKI pulse-exposure (imatinib, dasatinib) in BCR-ABL-positive cells. Comprehensive mechanistic exploration revealed dramatic intracellular accumulation of TKIs which closely correlated with induction of apoptosis. Cells were rescued from apoptosis upon HD-TKI pulse either by repetitive drug wash-out or by overexpression of ABC-family drug transporters. Inhibition of ABCB1 restored sensitivity to HD-TKI pulse-exposure. Thus, our data provide evidence that intracellular drug retention crucially determines biological activity of imatinib and dasatinib. These studies may refine our current thinking on critical requirements of TKI dose and duration of target inhibition for biological activity of TKIs. PMID:22815843

Exposure to Sublethal Ammonia Concentrations Alters the Duration and Intensity of Agonistic Interactions in the Crayfish, Orconectes rusticus.

PubMed

Edwards, David D; Klotz, Katie L; Moore, Paul A

2018-02-01

Crayfish extract information from chemical stimuli during social interactions. Commercial fertilizers increase background ammonia concentrations which may interfere with chemical communication. Background pollution can disrupt perception of chemical stimuli in three ways: masking, sensory impairment, physiological impairment or in combination. We investigated whether exposure to ammonia alters agonistic behavior. Crayfish pairs exposed to 0.9 mg/L ammonia fought for a longer duration, while crayfish exposed to 9.0 mg/L ammonia fought for a shorter duration. Altering activity patterns of crayfish may alter crayfish populations leading to a nonproportional impact because of their importance to the structure and function of aquatic ecosystems.

Long Duration Hot Hydrogen Exposure of Nuclear Thermal Rocket Materials

NASA Technical Reports Server (NTRS)

Litchford, Ron J.; Foote, John P.; Hickman, Robert; Dobson, Chris; Clifton, Scooter

2007-01-01

An arc-heater driven hyper-thermal convective environments simulator was recently developed and commissioned for long duration hot hydrogen exposure of nuclear thermal rocket materials. This newly established non-nuclear testing capability uses a high-power, multi-gas, wall-stabilized constricted arc-heater to .produce high-temperature pressurized hydrogen flows representative of nuclear reactor core environments, excepting radiation effects, and is intended to serve as a low cost test facility for the purpose of investigating and characterizing candidate fuel/structural materials and improving associated processing/fabrication techniques. Design and engineering development efforts are fully summarized, and facility operating characteristics are reported as determined from a series of baseline performance mapping runs and long duration capability demonstration tests.

Varied exposure to carcinogenic, mutagenic, and reprotoxic (CMR) chemicals in occupational settings in France.

PubMed

Havet, Nathalie; Penot, Alexis; Morelle, Magali; Perrier, Lionel; Charbotel, Barbara; Fervers, Béatrice

2017-02-01

To explore varied exposure to carcinogenic, mutagenic, and reprotoxic chemicals (CMR) for French employees. Our study assessed data from the French national cross-sectional survey of occupational risks (SUMER) that was conducted in 2010 in a national representative sample of employees. We selected 28 CMR agents that were classified by the International Agency for Research on Cancer or European Union as being known or presumed to have CMR potential in humans. The association of individual and job characteristics with exposure prevalence, duration, and intensity of the CMR agents during a 1-week period was examined using multilevel logistic regression analysis. Overall, 10.4% of employees in 2010 were exposed to one or more CMR agents at their workplace, and 3.4% were subjected to multiple CMR exposures. Blue-collar workers, night-shift workers and workers with short-term employment contracts experienced higher exposure prevalence (p < 0.01) and intensity (p < 0.05). Blue-collar workers and shift workers experienced also longer exposure duration (p < 0.001). Conversely, managers, workers of large companies, and women were less exposed to CMR agents (p < 0.001). The presence of a Committee for Health, Safety, and Working Conditions, and intervention by Occupational Health and Safety officers were significantly associated with reduced exposure intensities (p < 0.001 and p < 0.05). Establishment of European CMR regulations and the existence of an applicable substitution principle reduced the exposure duration (p < 0.001) and intensity (p < 0.05). Our results point out disparities in CMR exposure and identify high-priority targets for prevention measures to help reducing social health discrepancies.

Statistical modelling of formaldehyde occupational exposure levels in French industries, 1986-2003.

PubMed

Lavoué, Jérôme; Vincent, Raymond; Gérin, Michel

2006-04-01

Occupational exposure databanks (OEDBs) have been cited as sources of exposure data for exposure surveillance and exposure assessment in epidemiology. In 2003, an extract was made from COLCHIC, the French national OEDB, of all concentrations of formaldehyde. The data were analysed with extended linear mixed-effects models in order to identify influent variables and elaborate a multi-sector picture of formaldehyde exposures. Respectively, 1401 and 1448 personal and area concentrations were available for the analysis. The fixed effects of the personal and area models explained, respectively, 57 and 53% of the total variance. Personal concentrations were related to the sampling duration (short-term higher than TWA levels), decreased with the year of sampling (-9% per year) and were higher when local exhaust ventilation was present. Personal levels taken during planned visits and for occupational illness notification purpose were consistently lower than those taken during ventilation modification programmes or because the hygienist suspected the presence of significant risk or exposure. Area concentrations were related to the sampling duration (short-term higher than TWA levels), and decreased with the year of sampling (-7% per year) and when the measurement sampling flow increased. Significant within-facility (correlation coefficient 0.4-0.5) and within-sampling campaign correlation (correlation coefficient 0.8) was found for both area and personal data. The industry/task classification appeared to have the greatest influence on exposure variability while the sample duration and the sampling flow were significant in some cases. Estimates made from the models for year 2002 showed elevated formaldehyde exposure in the fields of anatomopathological and biological analyses, operation of gluing machinery in the wood industry, operation and monitoring of mixers in the pharmaceutical industry, and garages and warehouses in urban transit authorities.

Relationship among aqueous copper half-lives and responses of Pimephales promelas to a series of copper sulfate pentahydrate concentrations.

PubMed

Calomeni, Alyssa J; Kinley, Ciera M; Geer, Tyler D; Iwinski, Kyla J; Hendrikse, Maas; Rodgers, John H

2018-04-01

Copper algaecide exposures in situ are often of shorter duration than exposures for static toxicity experiments because aqueous concentrations in situ dissipate as a function of site-specific fate processes. Consequently, responses of organisms to static copper exposures may overestimate effects following in situ exposures. To understand the role of exposure duration for altering responses, Pimephales promelas survival was compared following static (96 h) and pulse (1.5, 4, 8, and 15 h half-lives) exposures of CuSO 4 •5H 2 O. Copper concentrations sorbed by fry indicated a consequence of different exposures. Responses of P. promelas to static exposures resulted in 96 h LC 50 s of 166 µgCu/L (95% confidence interval [CI], 142-189 µgCu/L) as soluble copper and 162 µgCu/L (CI, 140-183 µgCu/L) as acid soluble copper. Relative to static 96 h LC 50 s, exposures with half-lives of 1.5, 4 and 8 h resulted in LC 50 s 10, 3 and 2 times greater, respectively, for responses measured 96 h after exposure initiation. Copper concentrations extracted from fry exposed for 1.5, 4 and 8 h half-lives were less than the static experiment. However, copper sorbed by fry in the 15 h half-life experiment was not different than the static experiment. The relationship between 96 h LC 50 and 1/half-life was expressed using the equations y = 116 + 1360 × (R 2  = 0.97) for soluble copper and y = 147 + 1620 × (R 2  = 0.98) for acid soluble copper. Incorporation of exposure duration for predictions of P. promelas responses to copper pulse exposures increases prediction accuracy by an order of magnitude.

Wavelength dependence of laser-induced retinal injury

NASA Astrophysics Data System (ADS)

Lund, David J.; Edsall, Peter; Stuck, Bruce E.

2005-04-01

The threshold for laser-induced retinal damage is dependent primarily upon the laser wavelength and the exposure duration. The study of the wavelength dependence of the retinal damage threshold has been greatly enhanced by the availability of tunable lasers. The Optical Parametric Oscillator (OPO), capable of providing useful pulse energy throughout a tuning range from 400 nm to 2200 nm, made it possible to determine the wavelength dependence of laser-induced retinal damage thresholds for q-switched pulses throughout the visible and NIR spectrum. Studies using the a tunable TI:Saph laser and several fixed-wavelength lasers yielded threshold values for 0.1 s exposures from 440 nm to 1060 nm. Laser-induced retinal damage for these exposure durations results from thermal conversion of the incident laser irradiation and an action spectrum for thermal retinal damage was developed based on the wavelength dependent transmission and absorption of ocular tissue and chromatic aberration of the eye optics. Long (1-1000s) duration exposures to visible laser demonstrated the existence of non-thermal laser-induced retinal damage mechanisms having a different action spectrum. This paper will present the available data for the wavelength dependence of laser-induced thermal retinal damage and compare this data to the maximum permissible exposure levels (MPEs) provided by the current guidelines for the safe use of lasers.

Effects of free and combined chlorine and exposure duration on rainbow trout, channel catfish, and emerald shiners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brooks, A.S.; Bartos, J.M.

1984-11-01

Laboratory bioassays to determine the acute toxicity of monochloramine, dichloramine, hypochlorous acid, and hypochlorite ion to emerald shiners Notropis atherinoides, channel catfish Ictalurus punctatus, and rainbow trout Salmo gairdneri were conducted. Four exposure regimes typical of chlorination schedules at operating steam electric power plants were used. Fish were exposed for single 15-minute, 30-minute, 120-minute, and 4 x 30-minute periods. Based on median lethal concentrations (LC50s), the nominal solution of hypochlorous acid was the most toxic, followed closely by the solution dominated by dichloramine; nominal monochloramine and hypochlorite ion solutions had a third to a quarter the toxicity of the othermore » two. On the average, emerald shiners were 1.8 times more sensitive than channel catfish and 3.3 times more sensitive than rainbow trout to the four forms of chlorine. The fish were most tolerant of chlorine during short-duration exposures and least tolerant during the continuous 120-minute exposures. The differences in toxicity noted among the chlorine forms suggest that, when chlorination regimes and regulations are established, careful attention should be paid not only to total residual chlorine but to both the chlorine forms and fish species present and the duration of exposure. 24 references, 1 figure, 1 table.« less

A case-control study of lung cancer among refinery workers.

PubMed

Rosamilia, K; Wong, O; Raabe, G K

1999-12-01

This case-control study examined the relationship between lung cancer and the work histories of male employees at a large Texas refinery. The study included 112 lung cancer deaths observed between 1946 and 1987 and 490 matched controls. Employment histories were obtained from personnel records, and smoking information was available from medical records. Both stratification methods and conditional logistic regression were used in data analyses. Overall employment in four general job categories (administrative, engineering/laboratory, process, maintenance/mechanical) was not associated with lung cancer mortality. Results by hire period (< 1940, 1940+) showed that workers hired into process jobs before 1940 had a nonsignificantly elevated odds ratio (OR) of 1.71 (95% confidence interval [CI] = 0.85-3.45) compared with nonprocess workers hired before 1940. Among process workers hired before 1940, there was a significant trend toward increasing OR with increasing duration of employment in process jobs, and the association with lung cancer was strongest among smokers in the highest duration category of 30+ years (OR = 2.98, 95% CI = 1.07-8.31). Latency analyses of process workers hired before 1940 indicated that their lung cancer risk had peaked between 30 and 50 years since first employment. Definitive statements about causal factors are limited because results among process workers were based on small numbers of subjects in some exposure categories, and there was no information on specific workplace exposures. The OR for maintenance/mechanical jobs after adjustment for smoking was 1.00 (95% CI = 0.55-1.82). Furthermore, there was no pattern in relation to duration of employment in maintenance/mechanical jobs. The results from this study do not support the hypothesis that work in maintenance/mechanical jobs increases lung cancer risk. On the basis of analyses in this study, it is unlikely that asbestos exposure contributed to excess lung cancer mortality. Additional analyses were conducted for specific maintenance jobs with potential exposure to asbestos and by duration in jobs with occasional or routine asbestos exposure. No significant increase in lung cancer was found in any subgroup. Furthermore, there was no significant trend toward lung cancer risk in relation to duration of employment in jobs with asbestos exposure.

Long-term exposure to jet fuel. II. A cross-sectional epidemiologic investigation on occupationally exposed industrial workers with special reference to the nervous system.

PubMed

Knave, B; Olson, B A; Elofsson, S; Gamberale, F; Isaksson, A; Mindus, P; Persson, H E; Struwe, G; Wennberg, A; Westerholm, P

1978-03-01

Thirty jet fuel exposed workers selected according to exposure criteria and thirty nonexposed controls from a jet motor factory were examined, with special reference to the nervous system, by occupational hygiene physicians, psychiatrists, psychologists, and neurophysiologists. The controls and the exposed subjects were matched with respect to age, employment duration, and education. Among the exposed subjects the mean exposure duration was 17 years, and 300 mg/m3 was calculated as a rough time-weighted average exposure level. The investigation revealed significant differences between the exposed and nonexposed groups for (a) incidence and prevalence of psychiatric symptoms, (b) psychological tests with the load on attention and sensorimotor speed and (c) electroencephalograms. When the control group was selected, it was ensured that the two groups were essentially equivalent except for exposure to jet fuel. It is concluded, therefore, that the differences found between the groups are probably related to exposure to jet fuel.

Televised antismoking advertising: effects of level and duration of exposure.

PubMed

Dunlop, Sally; Cotter, Trish; Perez, Donna; Wakefield, Melanie

2013-08-01

We assessed the effects of levels and duration of exposure to televised antismoking advertising on cognitive and behavioral changes. We used data from a serial cross-sectional telephone survey with weekly interviews of adult smokers and recent quitters in New South Wales, Australia (n = 13,301), between April 2005 and December 2010. We merged survey data with commercial TV ratings data to estimate individuals' exposure to antismoking advertising. Logistic regression analyses indicated that after adjustment for a wide range of potential confounders, exposure to antismoking advertising at levels between 100 and 200 gross rating points per week on average over 6 to 9 weeks was associated with an increased likelihood of having (1) salient quitting thoughts and (2) recent quit attempts. Associations between exposure for shorter periods and these outcomes were not significant. Broadcasting schedules may affect the success of antismoking ads. Campaign planners should ensure advertising exposure at adequate frequency over relatively sustained periods to maximize impact.

Effect of polychlorinated biphenyls on osmoregulatory response and apoptosis in GIFT tilapia, Oreochromis niloticus.

PubMed

Zheng, Y; Qiu, L; Fan, L; Song, C; Meng, S; Chen, J

2016-09-02

In the present study, GIFT tilapia Oreochromis niloticus were exposed to polychlorinated biphenyls (PCBs) for 7, 14, and 21 days. Over the duration of the exposure, genotoxicity and the activity of Na + /K + -ATPase (NKA) and Ca + /Mg + -ATPase (CMA) were measured in the gill, kidney, and intestine, to evaluate changes in osmoregulatory response in O. niloticus. Our results showed significant decreases in organic NKA (except in gill tissues after 0.5 mg/L PCB-exposure) and CMA activity. The results of the genotoxicity assay showed significant increases in atp1a1a, nkcc2 (only in gill tissue), and fxyd7 (except after 21 days of 5 mg/L PCB exposure). We found significant increases in caspase proteins in the liver in the 5-mg/L PCB exposure group, and the transcripts showed dose-dependent increases between treatment groups over the exposure duration. This study presents evidence that chronic exposure to PCB could result in organic osmoregulatory response and hepatic apoptosis in GIFT tilapia.

Infrared skin damage thresholds from 1319-nm continuous-wave laser exposures

NASA Astrophysics Data System (ADS)

Oliver, Jeffrey W.; Vincelette, Rebecca; Noojin, Gary D.; Clark, Clifton D.; Harbert, Corey A.; Schuster, Kurt J.; Shingledecker, Aurora D.; Kumru, Semih S.; Maughan, Justin; Kitzis, Naomi; Buffington, Gavin D.; Stolarski, David J.; Thomas, Robert J.

2013-12-01

A series of experiments were conducted in vivo using Yucatan miniature pigs (Sus scrofa domestica) to determine thermal damage thresholds to the skin from 1319-nm continuous-wave Nd:YAG laser irradiation. Experiments employed exposure durations of 0.25, 1.0, 2.5, and 10 s and beam diameters of ˜0.6 and 1 cm. Thermal imagery data provided a time-dependent surface temperature response from the laser. A damage endpoint of fifty percent probability of a minimally visible effect was used to determine threshold for damage at 1 and 24 h postexposure. Predicted thermal response and damage thresholds are compared with a numerical model of optical-thermal interaction. Resultant trends with respect to exposure duration and beam diameter are compared with current standardized exposure limits for laser safety. Mathematical modeling agreed well with experimental data, predicting that though laser safety standards are sufficient for exposures <10 s, they may become less safe for very long exposures.

A common neonicotinoid pesticide, thiamethoxam, impairs honey bee flight ability.

PubMed

Tosi, Simone; Burgio, Giovanni; Nieh, James C

2017-04-26

Pesticides can pose environmental risks, and a common neonicotinoid pesticide, thiamethoxam, decreases homing success in honey bees. Neonicotinoids can alter bee navigation, but we present the first evidence that neonicotinoid exposure alone can impair the physical ability of bees to fly. We tested the effects of acute or chronic exposure to thiamethoxam on the flight ability of foragers in flight mills. Within 1 h of consuming a single sublethal dose (1.34 ng/bee), foragers showed excitation and significantly increased flight duration (+78%) and distance (+72%). Chronic exposure significantly decreased flight duration (-54%), distance (-56%), and average velocity (-7%) after either one or two days of continuous exposure that resulted in bees ingesting field-relevant thiamethoxam doses of 1.96-2.90 ng/bee/day. These results provide the first demonstration that acute or chronic exposure to a neonicotinoid alone can significantly alter bee flight. Such exposure may impair foraging and homing, which are vital to normal colony function and ecosystem services.

Televised Antismoking Advertising: Effects of Level and Duration of Exposure

PubMed Central

Cotter, Trish; Perez, Donna; Wakefield, Melanie

2013-01-01

Objectives. We assessed the effects of levels and duration of exposure to televised antismoking advertising on cognitive and behavioral changes. Methods. We used data from a serial cross-sectional telephone survey with weekly interviews of adult smokers and recent quitters in New South Wales, Australia (n = 13 301), between April 2005 and December 2010. We merged survey data with commercial TV ratings data to estimate individuals’ exposure to antismoking advertising. Results. Logistic regression analyses indicated that after adjustment for a wide range of potential confounders, exposure to antismoking advertising at levels between 100 and 200 gross rating points per week on average over 6 to 9 weeks was associated with an increased likelihood of having (1) salient quitting thoughts and (2) recent quit attempts. Associations between exposure for shorter periods and these outcomes were not significant. Conclusions. Broadcasting schedules may affect the success of antismoking ads. Campaign planners should ensure advertising exposure at adequate frequency over relatively sustained periods to maximize impact. PMID:23763419

Periodic catatonia with long-term treatment: a case report.

PubMed

Chen, Ruei-An; Huang, Tiao-Lai

2017-09-29

Periodic catatonia has long been a challenging diagnosis and there are no absolute guidelines for treatment when precipitating factors are also unclear. We report a schizophrenia patient with periodic catatonia with a 15-year treatment course. A possible correlation between decreased daylight exposure and periodic attacks has been observed. We describe a 49-year-old woman with periodic catatonia associated with schizophrenia with 15 years of follow-up. The patient was treated with the antipsychotics risperidone, haloperidol, loxapine and quetiapine, but catatonia still relapsed once per year during the first few years of her disease course. The treatment was consequently been switched to clozapine due to fluctuated psychotic illness, and a longer duration of remittance was achieved. Lorazepam-diazepam protocol was used for rapid relief of catatonic symptoms, and was able to significantly shorten the duration of the symptoms. In addition, we observed a possible correlation between catatonic episodes and decreased daylight exposure during the 15-year duration. Successful treatment of acute periodic catatonia was achieved with a lorazepam-diazepam protocol, and the patient remained in remission for a longer duration under clozapine treatment. Besides, the possibility of decreased daylight exposure acting as a precipitating factor was observed during our 15 years of follow-up.

On the physics of laser-induced selective photothermolysis of hair follicles: Influence of wavelength, pulse duration, and epidermal cooling.

PubMed

Svaasand, Lars O; Nelson, J Stuart

2004-01-01

The physical basis for optimization of wavelength, pulse duration, and cooling for laser-induced selective photothermolysis of hair follicles in human skin is discussed. The results indicate that the most important optimization parameter is the cooling efficiency of the technique utilized for epidermal protection. The optical penetration is approximately the same for lasers at 694, 755, and 800 nm. The penetration of radiation from Nd:yttrium-aluminum-garnet lasers at 1064 nm is, however, somewhat larger. Photothermal damage to the follicle is shown to be almost independent of laser pulse duration up to 100 ms. The results reveal that epidermal cooling by a 30-80-ms-long cryogen spurt immediately before laser exposure is the only efficient technique for laser pulse durations less than 10 ms. For longer pulse durations in the 30-100 ms range, protection can be done efficiently by skin cooling during laser exposure. For laser pulses of 100 ms, an extended precooling period, e.g., by bringing a cold object into good thermal contact with the skin for about 1 s, can be of value. Thermal quenching of laser induced epidermal temperature rise after pulsed exposure can most efficiently be done with a 20 ms cryogen spurt applied immediately after irradiation. (c) 2004 Society of Photo-Optical Instrumentation Engineers.

Predicting the hepatocarcinogenic potential of alkenylbenzene flavoring agents using toxicogenomics and machine learning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Auerbach, Scott S.; Shah, Ruchir R.; Mav, Deepak

Identification of carcinogenic activity is the primary goal of the 2-year bioassay. The expense of these studies limits the number of chemicals that can be studied and therefore chemicals need to be prioritized based on a variety of parameters. We have developed an ensemble of support vector machine classification models based on male F344 rat liver gene expression following 2, 14 or 90 days of exposure to a collection of hepatocarcinogens (aflatoxin B1, 1-amino-2,4-dibromoanthraquinone, N-nitrosodimethylamine, methyleugenol) and non-hepatocarcinogens (acetaminophen, ascorbic acid, tryptophan). Seven models were generated based on individual exposure durations (2, 14 or 90 days) or a combination ofmore » exposures (2 + 14, 2 + 90, 14 + 90 and 2 + 14 + 90 days). All sets of data, with the exception of one yielded models with 0% cross-validation error. Independent validation of the models was performed using expression data from the liver of rats exposed at 2 dose levels to a collection of alkenylbenzene flavoring agents. Depending on the model used and the exposure duration of the test data, independent validation error rates ranged from 47% to 10%. The variable with the most notable effect on independent validation accuracy was exposure duration of the alkenylbenzene test data. All models generally exhibited improved performance as the exposure duration of the alkenylbenzene data increased. The models differentiated between hepatocarcinogenic (estragole and safrole) and non-hepatocarcinogenic (anethole, eugenol and isoeugenol) alkenylbenzenes previously studied in a carcinogenicity bioassay. In the case of safrole the models correctly differentiated between carcinogenic and non-carcinogenic dose levels. The models predict that two alkenylbenzenes not previously assessed in a carcinogenicity bioassay, myristicin and isosafrole, would be weakly hepatocarcinogenic if studied at a dose level of 2 mmol/kg bw/day for 2 years in male F344 rats; therefore suggesting that these chemicals should be a higher priority relative to other untested alkenylbenzenes for evaluation in the carcinogenicity bioassay. The results of the study indicate that gene expression-based predictive models are an effective tool for identifying hepatocarcinogens. Furthermore, we find that exposure duration is a critical variable in the success or failure of such an approach, particularly when evaluating chemicals with unknown carcinogenic potency.« less

Predicting the hepatocarcinogenic potential of alkenylbenzene flavoring agents using toxicogenomics and machine learning.

PubMed

Auerbach, Scott S; Shah, Ruchir R; Mav, Deepak; Smith, Cynthia S; Walker, Nigel J; Vallant, Molly K; Boorman, Gary A; Irwin, Richard D

2010-03-15

Identification of carcinogenic activity is the primary goal of the 2-year bioassay. The expense of these studies limits the number of chemicals that can be studied and therefore chemicals need to be prioritized based on a variety of parameters. We have developed an ensemble of support vector machine classification models based on male F344 rat liver gene expression following 2, 14 or 90 days of exposure to a collection of hepatocarcinogens (aflatoxin B1, 1-amino-2,4-dibromoanthraquinone, N-nitrosodimethylamine, methyleugenol) and non-hepatocarcinogens (acetaminophen, ascorbic acid, tryptophan). Seven models were generated based on individual exposure durations (2, 14 or 90 days) or a combination of exposures (2+14, 2+90, 14+90 and 2+14+90 days). All sets of data, with the exception of one yielded models with 0% cross-validation error. Independent validation of the models was performed using expression data from the liver of rats exposed at 2 dose levels to a collection of alkenylbenzene flavoring agents. Depending on the model used and the exposure duration of the test data, independent validation error rates ranged from 47% to 10%. The variable with the most notable effect on independent validation accuracy was exposure duration of the alkenylbenzene test data. All models generally exhibited improved performance as the exposure duration of the alkenylbenzene data increased. The models differentiated between hepatocarcinogenic (estragole and safrole) and non-hepatocarcinogenic (anethole, eugenol and isoeugenol) alkenylbenzenes previously studied in a carcinogenicity bioassay. In the case of safrole the models correctly differentiated between carcinogenic and non-carcinogenic dose levels. The models predict that two alkenylbenzenes not previously assessed in a carcinogenicity bioassay, myristicin and isosafrole, would be weakly hepatocarcinogenic if studied at a dose level of 2 mmol/kg bw/day for 2 years in male F344 rats; therefore suggesting that these chemicals should be a higher priority relative to other untested alkenylbenzenes for evaluation in the carcinogenicity bioassay. The results of the study indicate that gene expression-based predictive models are an effective tool for identifying hepatocarcinogens. Furthermore, we find that exposure duration is a critical variable in the success or failure of such an approach, particularly when evaluating chemicals with unknown carcinogenic potency. Published by Elsevier Inc.

Work-related lesions of the supraspinatus tendon: a case-control study.

PubMed

Seidler, Andreas; Bolm-Audorff, Ulrich; Petereit-Haack, Gabriela; Ball, Elke; Klupp, Magdalena; Krauss, Noëlle; Elsner, Gine

2011-04-01

To examine the dose-response relationship between cumulative duration of work with highly elevated arms (work above shoulder level) as well as of manual material handling and ruptures of the supraspinatus tendon in a population-based case-control study. In 14 radiologic practices, we recruited 483 male patients aged 25-65 with radiographically confirmed partial (n = 385) or total (n = 98) supraspinatus tears associated with shoulder pain. A total of 300 male control subjects were recruited. Data were gathered in a structured personal interview. To calculate cumulative exposure, the self-reported duration of lifting/carrying of heavy loads (>20 kg) as well as the duration of work with highly elevated arms was added up over the entire working life. The results of our study support a dose-response relationship between cumulative duration of work with highly elevated arms and symptomatic supraspinatus tendon tears. For a cumulative duration of >3,195 h work above shoulder level, the risk of a supraspinatus tendon rupture is elevated to 2.0 (95% CI 1.1-3.5), adjusted for age, region, lifting/carrying of heavy loads, handheld vibration, apparatus gymnastics/shot put/javelin/hammer throwing/wrestling, and tennis. The cumulative duration of carrying/lifting of heavy loads also yields a positive dose-response relation with disease (independent from work above shoulder level and from handheld vibration), with an adjusted odds ratio of 1.8 (95% CI 1.0-3.2) in the highest exposure category (>77 h). We find an increased risk for subjects exposed to handheld vibration with an adjusted OR of 3.2 (95% CI 1.7-5.9) in the highest exposure category (16 years or more in the job with exposure), but a clear dose-response relationship is lacking. This study points to a potential etiologic role of long-term cumulative effects of work with highly elevated arms and heavy lifting/carrying on shoulder tendon disorders.

The effect of shorter exposure versus prolonged exposure on treatment outcome in Tourette syndrome and chronic tic disorders - an open trial.

PubMed

van de Griendt, Jolande M T M; van Dijk, Maarten K; Verdellen, Cara W J; Verbraak, Marc J P M

2018-01-11

Exposure and response prevention has shown to be an effective strategy and is considered a first-line intervention in the behavioural treatment of tic disorders. Prior research demonstrated significant tic reduction after 12 two hour sessions. In this open trial, the question is addressed whether, relative to these prolonged sessions, exposure sessions of shorter duration yield differential outcome for patients with tic disorders. A total of 29 patients diagnosed with Tourette syndrome (TS) or chronic tic disorder were treated with shorter exposure sessions (1 h), and these data were compared to the data from a study about prolonged exposure (2 h, n = 21). Outcome was measured by the Yale Global Tic Severity Scale (YGTSS). Results suggest that after taking the difference in illness duration between the two groups into account, the effectiveness of shorter exposure sessions is not inferior to that of prolonged exposure. Results suggest that treatment with shorter exposure might be more efficient and more patients can be reached. Future research is needed to gain more insight into the mechanisms underlying the efficacy of behavioural treatments for tics.

Reminder duration determines threat memory modification in humans.

PubMed

Hu, Jingchu; Wang, Wenqing; Homan, Philipp; Wang, Penggui; Zheng, Xifu; Schiller, Daniela

2018-06-11

Memory reminders can return a memory into an unstable state such that it will decay unless actively restabilized into long-term memory through reconsolidation. Exposure to a memory reminder, however, does not always lead to destabilization. The 'trace dominance' principle posits that the extent of exposure to memory reminders governs memory susceptibility to disruption. Here, we provide a first systematic investigation of reminder duration effects on threat memory modification in humans. Reminder duration was parametrically varied across 155 participants in a three-day protocol. We found that short reminders (1 s and 4 s) made the memory prone to interference from post-retrieval extinction, suggesting that the memory had been updated. In contrast, no reminder or long reminders (30 s and 3 min) made the memory resistant to such interference, and robustly return. Reminder duration therefore influences memory stability and may be a critical determinant of therapeutic efficacy.

Durational and generational differences in Mexican immigrant obesity: Is acculturation the explanation?

PubMed Central

Creighton, Mathew J.; Goldman, Noreen; Pebley, Anne R.; Chung, Chang Y.

2012-01-01

Using the Los Angeles Family and Neighborhood Survey (L.A.FANS-2; n = 1610), we explore the link between Mexican immigrant acculturation, diet, exercise and obesity. We distinguish Mexican immigrants and 2nd generation Mexicans from 3rd+ generation whites, blacks and Mexicans. First, we examine variation in social and linguistic measures by race/ethnicity, duration of residence and immigrant generation. Second, we consider the association between acculturation, diet and exercise. Third, we evaluate the degree to which acculturation, diet, exercise, and socioeconomic status explain the association between race/ethnicity, immigrant exposure to the US (duration since immigration/generation), and adult obesity. Among immigrants, we find a clear relationship between acculturation measures, exposure to the US, and obesity-related behaviors (diet and exercise). However, the acculturation measures do not clearly account for the link between adult obesity, immigrant duration and generation, and race/ethnicity. PMID:22575698

Noise Exposure Estimates of Urban MP3 Player Users

ERIC Educational Resources Information Center

Levey, Sandra; Levey, Tania; Fligor, Brian J.

2011-01-01

Purpose: To examine the sound level and duration of use of personal listening devices (PLDs) by 189 college students, ages 18-53 years, as they entered a New York City college campus, to determine whether noise exposure from PLDs was in excess of recommended exposure limits and what factors might influence exposure. Method: Free-field equivalent…

Association between sitting and occupational LBP

PubMed Central

Black, Katia M.; Korn, Hayley; Nordin, Margareta

2006-01-01

Low back pain (LBP) has been identified as one of the most costly disorders among the worldwide working population. Sitting has been associated with risk of developing LBP. The purpose of this literature review is to assemble and describe evidence of research on the association between sitting and the presence of LBP. The systematic literature review was restricted to those occupations that require sitting for more than half of working time and where workers have physical co-exposure factors such as whole body vibration (WBV) and/or awkward postures. Twenty-five studies were carefully selected and critically reviewed, and a model was developed to describe the relationships between these factors. Sitting alone was not associated with the risk of developing LBP. However, when the co-exposure factors of WBV and awkward postures were added to the analysis, the risk of LBP increased fourfold. The occupational group that showed the strongest association with LBP was Helicopter Pilots (OR=9.0, 90% CI 4.9–16.4). For all studied occupations, the odds ratio (OR) increased when WBV and/or awkward postures were analyzed as co-exposure factors. WBV while sitting was also independently associated with non-specific LBP and sciatica. Vibration dose, as well as vibration magnitude and duration of exposure, were associated with LBP in all occupations. Exposure duration was associated with LBP to a greater extent than vibration magnitude. However, for the presence of sciatica, this difference was not found. Awkward posture was also independently associated with the presence of LBP and/or sciatica. The risk effect of prolonged sitting increased significantly when the factors of WBV and awkward postures were combined. Sitting by itself does not increase the risk of LBP. However, sitting for more than half a workday, in combination with WBV and/or awkward postures, does increase the likelihood of having LBP and/or sciatica, and it is the combination of those risk factors, which leads to the greatest increase in LBP. PMID:16736200

Association between sitting and occupational LBP.

PubMed

Lis, Angela Maria; Black, Katia M; Korn, Hayley; Nordin, Margareta

2007-02-01

Low back pain (LBP) has been identified as one of the most costly disorders among the worldwide working population. Sitting has been associated with risk of developing LBP. The purpose of this literature review is to assemble and describe evidence of research on the association between sitting and the presence of LBP. The systematic literature review was restricted to those occupations that require sitting for more than half of working time and where workers have physical co-exposure factors such as whole body vibration (WBV) and/or awkward postures. Twenty-five studies were carefully selected and critically reviewed, and a model was developed to describe the relationships between these factors. Sitting alone was not associated with the risk of developing LBP. However, when the co-exposure factors of WBV and awkward postures were added to the analysis, the risk of LBP increased fourfold. The occupational group that showed the strongest association with LBP was Helicopter Pilots (OR=9.0, 90% CI 4.9-16.4). For all studied occupations, the odds ratio (OR) increased when WBV and/or awkward postures were analyzed as co-exposure factors. WBV while sitting was also independently associated with non-specific LBP and sciatica. Vibration dose, as well as vibration magnitude and duration of exposure, were associated with LBP in all occupations. Exposure duration was associated with LBP to a greater extent than vibration magnitude. However, for the presence of sciatica, this difference was not found. Awkward posture was also independently associated with the presence of LBP and/or sciatica. The risk effect of prolonged sitting increased significantly when the factors of WBV and awkward postures were combined. Sitting by itself does not increase the risk of LBP. However, sitting for more than half a workday, in combination with WBV and/or awkward postures, does increase the likelihood of having LBP and/or sciatica, and it is the combination of those risk factors, which leads to the greatest increase in LBP.

Integration of multiple theories for the simulation of laser interference lithography processes

NASA Astrophysics Data System (ADS)

Lin, Te-Hsun; Yang, Yin-Kuang; Fu, Chien-Chung

2017-11-01

The periodic structure of laser interference lithography (LIL) fabrication is superior to other lithography technologies. In contrast to traditional lithography, LIL has the advantages of being a simple optical system with no mask requirements, low cost, high depth of focus, and large patterning area in a single exposure. Generally, a simulation pattern for the periodic structure is obtained through optical interference prior to its fabrication through LIL. However, the LIL process is complex and combines the fields of optical and polymer materials; thus, a single simulation theory cannot reflect the real situation. Therefore, this research integrates multiple theories, including those of optical interference, standing waves, and photoresist characteristics, to create a mathematical model for the LIL process. The mathematical model can accurately estimate the exposure time and reduce the LIL process duration through trial and error.

Integration of multiple theories for the simulation of laser interference lithography processes.

PubMed

Lin, Te-Hsun; Yang, Yin-Kuang; Fu, Chien-Chung

2017-11-24

The periodic structure of laser interference lithography (LIL) fabrication is superior to other lithography technologies. In contrast to traditional lithography, LIL has the advantages of being a simple optical system with no mask requirements, low cost, high depth of focus, and large patterning area in a single exposure. Generally, a simulation pattern for the periodic structure is obtained through optical interference prior to its fabrication through LIL. However, the LIL process is complex and combines the fields of optical and polymer materials; thus, a single simulation theory cannot reflect the real situation. Therefore, this research integrates multiple theories, including those of optical interference, standing waves, and photoresist characteristics, to create a mathematical model for the LIL process. The mathematical model can accurately estimate the exposure time and reduce the LIL process duration through trial and error.

Association between betel quid chewing and carotid intima-media thickness in rural Bangladesh

PubMed Central

McClintock, Tyler R; Parvez, Faruque; Wu, Fen; Wang, Weijia; Islam, Tariqul; Ahmed, Alauddin; Shaheen, Ishrat; Sarwar, Golam; Demmer, Ryan T; Desvarieux, Moise; Ahsan, Habibul; Chen, Yu

2014-01-01

Background: Areca nut, more commonly known as betel nut, is the fourth most commonly used addictive substance in the world. Though recent evidence suggests it may play a role in the development of cardiovascular disease, no studies have investigated whether betel nut use is related to subclinical atherosclerosis. Methods: We evaluated the association between betel nut use and subclinical atherosclerosis in 1206 participants randomly sampled from the Health Effects of Arsenic Longitudinal Study (HEALS). Frequency and duration of betel nut use were assessed at baseline, and carotid IMT was measured on average 6.65 years after baseline. Results: A positive association was observed between duration and cumulative exposure (function of duration and frequency) of betel nut use and IMT, with above-median use for duration (7 or more years) and cumulative exposure (30 or more quid-years) corresponding to a 19.1 μm [95% confidence interval (CI): 5.3-32.8; P ≤ 0.01] and 16.8 μm (95% CI: 2.9-30.8; P < 0.05) higher IMT in an adjusted model, respectively. This association was more pronounced in men [32.8 μm (95% CI: 10.0-55.7) and 30.9 μm (95% CI: 7.4-54.2)]. There was a synergy between cigarette smoking and above-median betel use such that the joint exposure was associated with a 42.4 μm (95% CI: 21.6-63.2; P ≤ 0.01) difference in IMT. Conclusion: Betel nut use at long duration or high cumulative exposure levels is associated with subclinical atherosclerosis as manifested through carotid IMT. This effect is especially pronounced among men and cigarette smokers. PMID:24550247

Association between betel quid chewing and carotid intima-media thickness in rural Bangladesh.

PubMed

McClintock, Tyler R; Parvez, Faruque; Wu, Fen; Wang, Weijia; Islam, Tariqul; Ahmed, Alauddin; Shaheen, Ishrat; Sarwar, Golam; Demmer, Ryan T; Desvarieux, Moise; Ahsan, Habibul; Chen, Yu

2014-08-01

Areca nut, more commonly known as betel nut, is the fourth most commonly used addictive substance in the world. Though recent evidence suggests it may play a role in the development of cardiovascular disease, no studies have investigated whether betel nut use is related to subclinical atherosclerosis. We evaluated the association between betel nut use and subclinical atherosclerosis in 1206 participants randomly sampled from the Health Effects of Arsenic Longitudinal Study (HEALS). Frequency and duration of betel nut use were assessed at baseline, and carotid IMT was measured on average 6.65 years after baseline. A positive association was observed between duration and cumulative exposure (function of duration and frequency) of betel nut use and IMT, with above-median use for duration (7 or more years) and cumulative exposure (30 or more quid-years) corresponding to a 19.1 μm [95% confidence interval (CI): 5.3-32.8; P ≤ 0.01] and 16.8 μm (95% CI: 2.9-30.8; P < 0.05) higher IMT in an adjusted model, respectively. This association was more pronounced in men [32.8 μm (95% CI: 10.0-55.7) and 30.9 μm (95% CI: 7.4-54.2)]. There was a synergy between cigarette smoking and above-median betel use such that the joint exposure was associated with a 42.4 μm (95% CI: 21.6-63.2; P ≤ 0.01) difference in IMT. Betel nut use at long duration or high cumulative exposure levels is associated with subclinical atherosclerosis as manifested through carotid IMT. This effect is especially pronounced among men and cigarette smokers. © The Author 2014; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association.

Exposure of Petrol Station Attendants and Auto Mechanics to Premium Motor Sprit Fumes in Calabar, Nigeria

PubMed Central

Udonwa, N. E.; Uko, E. K.; Ikpeme, B. M.; Ibanga, I. A.; Okon, B. O.

2009-01-01

A population-based-cross-sectional survey was carried out to investigate the potential risk of exposure to premium motor spirit (PMS) fumes in Calabar, Nigeria, among Automobile Mechanics (AM), Petrol Station Attendants (PSA) and the general population. Structured questionnaire was administered on the randomly chosen subjects to elicit information on their exposure to PMS. Duration of exposure was taken as the length of work in their various occupations. Venous blood was taken for methaemoglobin (MetHb) and packed cells volume (PCV). Mean MetHb value was higher in AM (7.3%) and PSA (5.8%) than in the subjects from the general population (2.7%). PCV was lower in PSA (30.8%), than AM (33.3%) and the subjects from the general population (40.8%). MetHb level was directly proportional, and PCV inversely related, to the duration of exposure. The study suggested increased exposure to petrol fumes among AM, PSA, and MetHb as a useful biomarker in determining the level of exposure to benzene in petrol vapour. PMID:19936128

Baseline tensile tests of composite materials for LDEF (Long Duration Exposure Facility) exposure

NASA Technical Reports Server (NTRS)

Witte, William G.

1987-01-01

Tensile specimens of five graphite fiber reinforced composite materials were tested at room temperature to provide baseline data for similar specimens exposed to the space environment in low-Earth orbit on the NASA Long Duration Exposure Facility. All specimens were 4-ply (+ or - 45 deg)s layups; at least five replicate specimens were tested for each parameter evaluated. Three epoxy-matrix materials and two polysulfone-matrix materials, several fiber volume fractions, and two sizes of specimen were evaluated. Stress-strain and Poisson's ratio-stress curves, ultimate stress, strain at failure, secant modulus at 0.004 strain, inplane shear stress-strain curves, and unidirectional shear modulus at .004 shear strain are presented.

The Elephant in the Room: Biomedical Challenges for Long Duration Lunar Habitation

NASA Technical Reports Server (NTRS)

Logan, James S.

2009-01-01

This slide presentation reviews 4 biomedical challenges that are involved in long duration lunar habitation: dust, radiation, hypogravity and synergistic effects. The first two of these challenges are reviewed with more in-depth information. The dangers of dust relate to the particle deposition in the lungs. The dangers of radiation are related to the permissible exposure limit (PEL) and the Risk of Exposure Induced Death (REID), a statistical approach pegged to a single radiation effect: Death from cancer directly attributable to the exposure. There has been a realization that radiation is more harmful than predicted. This is demonstrated by showing the change in the recommended career dose limits, have changed between 1989 and 2000.

Holographic data storage crystals for the LDEF. [long duration exposure facility

NASA Technical Reports Server (NTRS)

Callen, W. Russell; Gaylord, Thomas K.

1992-01-01

Lithium niobate is a significant electro-optic material, with potential applications in ultra high capacity storage and processing systems. Lithium niobate is the material of choice for many integrated optical devices and holographic mass memory systems. For crystals of lithium niobate were passively exposed to the space environment of the Long Duration Exposure Facility (LDEF). Three of these crystals contained volume holograms. Although the crystals suffered the surface damage characteristics of most of the other optical components on the Georgia Tech tray, the crystals were recovered intact. The holograms were severely degraded because of the lengthy exposure, but the bulk properties are being investigated to determine the spaceworthiness for space data storage and retrieval systems.

Human exposure to power frequency magnetic fields up to 7.6 mT: An integrated EEG/fMRI study.

PubMed

Modolo, Julien; Thomas, Alex W; Legros, Alexandre

2017-09-01

We assessed the effects of power-line frequency (60 Hz in North America) magnetic fields (MF) in humans using simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). Twenty-five participants were enrolled in a pseudo-double-blind experiment involving "real" or "sham" exposure to sinusoidal 60 Hz MF exposures delivered using the gradient coil of an MRI scanner following two conditions: (i) 10 s exposures at 3 mT (10 repetitions); (ii) 2 s exposures at 7.6 mT (100 repetitions). Occipital EEG spectral power was computed in the alpha range (8-12 Hz, reportedly the most sensitive to MF exposure in the literature) with/without exposure. Brain functional activation was studied using fMRI blood oxygen level-dependent (BOLD, inversely correlated with EEG alpha power) maps. No significant effects were detected on occipital EEG alpha power during or post-exposure for any exposure condition. Consistent with EEG results, no effects were observed on fMRI BOLD maps in any brain region. Our results suggest that acute exposure (2-10 s) to 60 Hz MF from 3 to 7.6 mT (30,000 to 76,000 times higher than average public exposure levels for 60 Hz MF) does not induce detectable changes in EEG or BOLD signals. Combined with previous findings in which effects were observed on the BOLD signal after 1 h exposure to 3 mT, 60 Hz MF, this suggests that MF exposure in the low mT range (<10 mT) might require prolonged durations of exposure to induce detectable effects. Bioelectromagnetics. 38:425-435, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Elaborated Odor Test for Extended Exposure

NASA Technical Reports Server (NTRS)

Buchanan, Vanessa D.; Henry, Emily J.; Mast, Dion J.; Harper, Susana A.; Beeson, Harold D.; Tapia, Alma S.

2016-01-01

Concerns were raised when incidental exposure to a proprietary bonding material revealed the material had an irritating odor. The NASA-STD-6001B document describes a supplemental test method option for programs to evaluate materials with odor concerns (Test 6, Odor Assessment). In addition to the supplemental standard odor assessment with less than 10 seconds of exposure, the NASA White Sands Test Facility (WSTF) Materials Flight Acceptance Testing section was requested to perform an odor test with an extended duration to evaluate effects of an extended exposure and to more closely simulate realistic exposure scenarios. With approval from the NASA Johnson Space Center Industrial Hygienist, WSTF developed a 15-minute odor test method. WSTF performed this extended-duration odor test to evaluate the odor and physical effects of the bonding material configured between two aluminum plates, after the safety of the gas was verified via toxicity analysis per NASA-STD-6001B Test 7, Determination of Offgassed Products. During extended-duration testing, odor panel members were arranged near the test material in a small room with the air handlers and doors closed to minimize dilution. The odor panel members wafted gas toward themselves and recorded their individual assessments of odor and physical effects at various intervals during the 15-minute exposure and posttest. A posttest interview was conducted to obtain further information. Testing was effective in providing data for comparison and selection of an optimal offgassing and odor containment configuration. The developed test method for extended exposure is proposed as a useful tool for further evaluating materials with identified odors of concern if continued use of the material is anticipated.

Radiation exposure during in-situ pinning of slipped capital femoral epiphysis hips: does the patient positioning matter?

PubMed

Mohammed, Riazuddin; Johnson, Karl; Bache, Ed

2010-07-01

Multiple radiographic images may be necessary during the standard procedure of in-situ pinning of slipped capital femoral epiphysis (SCFE) hips. This procedure can be performed with the patient positioned on a fracture table or a radiolucent table. Our study aims to look at any differences in the amount and duration of radiation exposure for in-situ pinning of SCFE performed using a traction table or a radiolucent table. Sixteen hips in thirteen patients who were pinned on radiolucent table were compared for the cumulative radiation exposure to 35 hips pinned on a fracture table in 33 patients during the same time period. Cumulative radiation dose was measured as dose area product in Gray centimeter2 and the duration of exposure was measured in minutes. Appropriate statistical tests were used to test the significance of any differences. Mean cumulative radiation dose for SCFE pinned on radiolucent table was statistically less than for those pinned on fracture table (P<0.05). The mean duration of radiation exposure on either table was not significantly different. Lateral projections may increase the radiation doses compared with anteroposterior projections because of the higher exposure parameters needed for side imaging. Our results showing decreased exposure doses on the radiolucent table are probably because of the ease of a frog leg lateral positioning obtained and thereby the ease of lateral imaging. In-situ pinning of SCFE hips on a radiolucent table has an additional advantage that the radiation dose during the procedure is significantly less than that of the procedure that is performed on a fracture table.

Surveillance of hearing loss among older construction and trade workers at Department of Energy nuclear sites.

PubMed

Dement, John; Ringen, Knut; Welch, Laura; Bingham, Eula; Quinn, Patricia

2005-11-01

Medical screening programs at three Departments of Energy (DOE) nuclear weapons facilities (Hanford Nuclear Reservation, Oak Ridge, and the Savannah River Site) have included audiometric testing since approximately 1996. This report summarizes hearing evaluations through March 31, 2003. Occupational examinations included a medical history, limited physical examination, and tests for medical effects from specific hazards, including audiometric testing. Hearing thresholds by frequency for DOE workers were compared to age-standardized thresholds among an external comparison population of industrial workers with noise exposures <80 dBA. Multivariate analyses were used to explore the risk of hearing impairment by duration of construction trade work and self-reported noise exposure, while controlling for potential confounders such as age, race, sex, smoking, elevated serum cholesterol, hypertension, solvent exposures, and recreational noise exposures. Hearing thresholds among DOE workers were much higher than observed in a comparison population of industrial workers with low noise exposures. Overall, 59.7% of workers examined were found to have material hearing impairment by NIOSH criteria. Age, duration of construction work, smoking, and self-reported noise exposure increased the risk of hearing loss. The risk of material hearing impairment was significantly elevated for construction trade workers compared to the external comparison population (odds-ratio = 1.6, 95% CI = 1.3-2.1) and increased with the duration of trade work. These medical screening programs confirm worker concerns about risks for hearing loss and the need for hearing conservation programs for construction workers, with emphasis on the prevention of noise exposures.

EMF radiations (1800 MHz)-inhibited early seedling growth of maize (Zea mays) involves alterations in starch and sucrose metabolism.

PubMed

Kumar, Arvind; Singh, Harminder Pal; Batish, Daizy R; Kaur, Shalinder; Kohli, Ravinder Kumar

2016-07-01

The present study investigated the impact of 1800-MHz electromagnetic field radiations (EMF-r), widely used in mobile communication, on the growth and activity of starch-, sucrose-, and phosphate-hydrolyzing enzymes in Zea mays seedlings. We exposed Z. mays to modulated continuous wave homogenous EMF-r at specific absorption rate (SAR) of 1.69±0.0 × 10(-1) W kg(-1) for ½, 1, 2, and 4 h. The analysis of seedlings after 7 days revealed that short-term exposure did not induce any significant change, while longer exposure of 4 h caused significant growth and biochemical alterations. There was a reduction in the root and coleoptile length with more pronounced effect on coleoptile growth (23 % reduction on 4-h exposure). The contents of photosynthetic pigments and total carbohydrates declined by 13 and 18 %, respectively, in 4-h exposure treatments compared to unexposed control. The activity of starch-hydrolyzing enzymes-α- and β-amylases-increased by ∼92 and 94 %, respectively, at an exposure duration of 4 h, over that in the control. In response to 4-h exposure treatment, the activity of sucrolytic enzymes-acid invertases and alkaline invertases-was increased by 88 and 266 %, whereas the specific activities of phosphohydrolytic enzymes (acid phosphatases and alkaline phosphatases) showed initial increase up to ≤2 h duration and then declined at >2 h exposure duration. The study concludes that EMF-r-inhibited seedling growth of Z. mays involves interference with starch and sucrose metabolism.

E057: Renal Stone Risk Assessment During Space Flight: Assessment and Countermeasure Validation

NASA Technical Reports Server (NTRS)

Whitson, Peggy A.; Pietrzyk, Robert A.; Jones, Jeffrey A.; Sams, Clarence F.

2001-01-01

Exposure to the microgravity environment results in many metabolic and physiological changes to humans. Body fluid volumes, electrolyte levels, and bone and muscle undergo changes as the human body adapts to the weightless environment. Changes in the urinary biochemistry occur as early as flight day 3-4 in the short duration Shuttle crewmembers. Significant decreases were observed both in fluid intake and urinary output. Other significant changes were observed in the urinary pH, calcium, potassium and uric acid levels. During Shuttle missions, the risk of calcium oxalate stone formation increased early in the flight, continued at elevated levels throughout the flight and remained in the increased risk range on landing day. The calcium phosphate risk was significantly increased early in-flight and remained significantly elevated throughout the remainder of the mission. Results from the long duration Shuttle-Mir missions followed a similar trend. Most long duration crewmembers demonstrated increased urinary calcium levels despite lower dietary calcium intake. Fluid intake and urine volumes were significantly lower during the flight than during the preflight. The calcium oxalate risk was increased relative to the preflight levels during the early in-flight period and continued in the elevated risk range for the remainder of the space flight and through two weeks postflight. Calcium phosphate risk for these long duration crewmembers increased during flight and remained in the increased risk range throughout the flight and following landing. The complexity, expense and visibility of the human space program require that every effort be made to protect the health of the crewmembers and ensure the success of the mission. Results from our early investigations clearly indicate that exposure to the microgravity environment of space significantly increases the risk of renal stone formation. The early studies have indicated specific avenues for development of countermeasures for the increased renal stone risk observed during and following space flight. Increased hydration and implementation of pharmacological countermeasures are being tested for their efficacy in mitigating the in-flight risk of renal stones. Maintaining the health and well-being of crewmembers during space flight requires a means of minimizing potential detrimental health effects of microgravity. The formation of a renal stone during flight obviously has severe consequences for the affected crewmember as well as the success of the mission.

Occupational exposure to dust and lung disease among sheet metal workers.

PubMed Central

Hunting, K L; Welch, L S

1993-01-01

A previous large medical survey of active and retired sheet metal workers with 20 or more years in the trade indicated an unexpectedly high prevalence of obstructive pulmonary disease among both smokers and non-smokers. This study utilised interviews with a cross section of the previously surveyed group to explore occupational risk factors for lung disease. Four hundred and seven workers were selected from the previously surveyed group on the basis of their potential for exposure to fibreglass and asbestos. Selection was independent of health state, and excluded welders. A detailed history of occupational exposure was obtained by telephone interview for 333 of these workers. Exposure data were analysed in relation to previously collected data on chronic bronchitis, obstructive lung disease, and personal characteristics. Assessment of the effects of exposure to fibreglass as distinct from the effects of exposure to asbestos has been difficult in previous studies of construction workers. The experienced workers studied here have performed a diversity of jobs involving exposure to many different types of materials, and this enabled exposure to each dust to be evaluated separately. The risk of chronic bronchitis increased sharply by pack-years of cigarettes smoked; current smokers had a double risk compared with those who had never smoked or had stopped smoking. The occurrence of chronic bronchitis also increased with increasing duration of exposure to asbestos. Workers with a history of high intensity exposure to fibreglass had a more than doubled risk of chronic bronchitis. Obstructive lung disease, defined by results of pulmonary function tests at the medical survey, was also related to both smoking and occupational risk factors. Number of pack years smoked was the strongest predictor of obstructive lung disease. Duration of direct and indirect exposure to welding fume was also a positive predictor of obstructive lung disease. Duration of exposure to asbestos was significantly associated with obstructive lung disease but the dose-response relation was inconsistent, especially for those with higher pack-years of smoking exposure. Exposure to fibreglass was not a risk factor for obstructive lung disease. PMID:8507596

Effect modification of the association of cumulative exposure and cancer risk by intensity of exposure and time since exposure cessation: a flexible method applied to cigarette smoking and lung cancer in the SYNERGY Study.

PubMed

Vlaanderen, Jelle; Portengen, Lützen; Schüz, Joachim; Olsson, Ann; Pesch, Beate; Kendzia, Benjamin; Stücker, Isabelle; Guida, Florence; Brüske, Irene; Wichmann, Heinz-Erich; Consonni, Dario; Landi, Maria Teresa; Caporaso, Neil; Siemiatycki, Jack; Merletti, Franco; Mirabelli, Dario; Richiardi, Lorenzo; Gustavsson, Per; Plato, Nils; Jöckel, Karl-Heinz; Ahrens, Wolfgang; Pohlabeln, Hermann; Tardón, Adonina; Zaridze, David; Field, John K; 't Mannetje, Andrea; Pearce, Neil; McLaughlin, John; Demers, Paul; Szeszenia-Dabrowska, Neonila; Lissowska, Jolanta; Rudnai, Peter; Fabianova, Eleonora; Stanescu Dumitru, Rodica; Bencko, Vladimir; Foretova, Lenka; Janout, Vladimir; Boffetta, Paolo; Forastiere, Francesco; Bueno-de-Mesquita, Bas; Peters, Susan; Brüning, Thomas; Kromhout, Hans; Straif, Kurt; Vermeulen, Roel

2014-02-01

The indiscriminate use of the cumulative exposure metric (the product of intensity and duration of exposure) might bias reported associations between exposure to hazardous agents and cancer risk. To assess the independent effects of duration and intensity of exposure on cancer risk, we explored effect modification of the association of cumulative exposure and cancer risk by intensity of exposure. We applied a flexible excess odds ratio model that is linear in cumulative exposure but potentially nonlinear in intensity of exposure to 15 case-control studies of cigarette smoking and lung cancer (1985-2009). Our model accommodated modification of the excess odds ratio per pack-year of cigarette smoking by time since smoking cessation among former smokers. We observed negative effect modification of the association of pack-years of cigarette smoking and lung cancer by intensity of cigarette smoke for persons who smoked more than 20-30 cigarettes per day. Patterns of effect modification were similar across individual studies and across major lung cancer subtypes. We observed strong negative effect modification by time since smoking cessation. Application of our method in this example of cigarette smoking and lung cancer demonstrated that reducing a complex exposure history to a metric such as cumulative exposure is too restrictive.

Effect Modification of the Association of Cumulative Exposure and Cancer Risk by Intensity of Exposure and Time Since Exposure Cessation: A Flexible Method Applied to Cigarette Smoking and Lung Cancer in the SYNERGY Study

PubMed Central

Vlaanderen, Jelle; Portengen, Lützen; Schüz, Joachim; Olsson, Ann; Pesch, Beate; Kendzia, Benjamin; Stücker, Isabelle; Guida, Florence; Brüske, Irene; Wichmann, Heinz-Erich; Consonni, Dario; Landi, Maria Teresa; Caporaso, Neil; Siemiatycki, Jack; Merletti, Franco; Mirabelli, Dario; Richiardi, Lorenzo; Gustavsson, Per; Plato, Nils; Jöckel, Karl-Heinz; Ahrens, Wolfgang; Pohlabeln, Hermann; Tardón, Adonina; Zaridze, David; Field, John K.; 't Mannetje, Andrea; Pearce, Neil; McLaughlin, John; Demers, Paul; Szeszenia-Dabrowska, Neonila; Lissowska, Jolanta; Rudnai, Peter; Fabianova, Eleonora; Stanescu Dumitru, Rodica; Bencko, Vladimir; Foretova, Lenka; Janout, Vladimir; Boffetta, Paolo; Forastiere, Francesco; Bueno-de-Mesquita, Bas; Peters, Susan; Brüning, Thomas; Kromhout, Hans; Straif, Kurt; Vermeulen, Roel

2014-01-01

The indiscriminate use of the cumulative exposure metric (the product of intensity and duration of exposure) might bias reported associations between exposure to hazardous agents and cancer risk. To assess the independent effects of duration and intensity of exposure on cancer risk, we explored effect modification of the association of cumulative exposure and cancer risk by intensity of exposure. We applied a flexible excess odds ratio model that is linear in cumulative exposure but potentially nonlinear in intensity of exposure to 15 case-control studies of cigarette smoking and lung cancer (1985–2009). Our model accommodated modification of the excess odds ratio per pack-year of cigarette smoking by time since smoking cessation among former smokers. We observed negative effect modification of the association of pack-years of cigarette smoking and lung cancer by intensity of cigarette smoke for persons who smoked more than 20–30 cigarettes per day. Patterns of effect modification were similar across individual studies and across major lung cancer subtypes. We observed strong negative effect modification by time since smoking cessation. Application of our method in this example of cigarette smoking and lung cancer demonstrated that reducing a complex exposure history to a metric such as cumulative exposure is too restrictive. PMID:24355332

Effect of alterations in metabolic rate on the duration of tolerance in neonatally injected animals.

PubMed

St Rose, J E; Murray, G W; Howe, S A

1976-01-01

Exposure to low environmental temperature caused a decrease in the half-life of human albumin (HA) in rabbits injected with 20 mg HA at birth, and a twofold increase in the proportion of animals which lost their tolerance by 150 days of age. Administration of thyroxin produced an even greater effect with respect to tolerance loss. Simlar mechanisms may be involved in the effects of cold exposure and thyroxin administration on tolerance duration. One possible mecahnism is that the duration of tolerance is dependent upon the metabolic half-life of the tolerance-inducing antigen. An alternative mechanism could be a cold- or thyroxin-induced enhancement of the recruitment of immunologically competent cells from an undifferentiated population of stem cells.

Absence of an increase in the duration of the circadian melatonin secretory episode in totally blind human subjects

NASA Technical Reports Server (NTRS)

Klerman, E. B.; Zeitzer, J. M.; Duffy, J. F.; Khalsa, S. B.; Czeisler, C. A.

2001-01-01

The daily rhythm of melatonin influences multiple physiological measures, including sleep tendency, circadian rhythms, and reproductive function in seasonally breeding mammals. The biological signal for photoperiodic changes in seasonally breeding mammals is a change in the duration of melatonin secretion, which in a natural environment reflects the different durations of daylight across the year, with longer nights leading to a longer duration of melatonin secretion. These seasonal changes in the duration of melatonin secretion do not simply reflect the known acute suppression of melatonin secretion by ocular light exposure, but also represent long-term changes in the endogenous nocturnal melatonin episode that persist in constant conditions. As the eyes of totally blind individuals do not transmit ocular light information, we hypothesized that the duration of the melatonin secretory episode in blind subjects would be longer than those in sighted individuals, who are exposed to light for all their waking hours in an urban environment. We assessed the melatonin secretory profile during constant posture, dim light conditions in 17 blind and 157 sighted adults, all of whom were healthy and using no prescription or nonprescription medications. The duration of melatonin secretion was not significantly different between blind and sighted individuals. Healthy blind individuals after years without ocular light exposure do not have a longer duration of melatonin secretion than healthy sighted individuals.

Atomic research

NASA Technical Reports Server (NTRS)

Hadaway, James B.; Connatser, Robert; Cothren, Bobby; Johnson, R. B.

1993-01-01

Work performed by the University of Alabama in Huntsville's (UAH) Center for Applied Optics (CAO) entitled Atomic Research is documented. Atomic oxygen (AO) effects on materials have long been a critical concern in designing spacecraft to withstand exposure to the Low Earth Orbit (LEO) environment. The objective of this research effort was to provide technical expertise in the design of instrumentation and experimental techniques for analyzing materials exposed to atomic oxygen in accelerated testing at NASA/MSFC. Such testing was required to answer fundamental questions concerning Space Station Freedom (SSF) candidate materials and materials exposed to atomic oxygen aboard the Long-Duration Exposure Facility (LDEF). The primary UAH task was to provide technical design, review, and analysis to MSFC in the development of a state-of-the-art 5eV atomic oxygen beam facility required to simulate the RAM-induced low earth orbit (LEO) AO environment. This development was to be accomplished primarily at NASA/MSFC. In support of this task, contamination effects and ultraviolet (UV) simulation testing was also to be carried out using NASA/MSFC facilities. Any materials analysis of LDEF samples was to be accomplished at UAH.

Exploring the time course of face matching: temporal constraints impair unfamiliar face identification under temporally unconstrained viewing.

PubMed

Ozbek, Müge; Bindemann, Markus

2011-10-01

The identification of unfamiliar faces has been studied extensively with matching tasks, in which observers decide if pairs of photographs depict the same person (identity matches) or different people (mismatches). In experimental studies in this field, performance is usually self-paced under the assumption that this will encourage best-possible accuracy. Here, we examined the temporal characteristics of this task by limiting display times and tracking observers' eye movements. Observers were required to make match/mismatch decisions to pairs of faces shown for 200, 500, 1000, or 2000ms, or for an unlimited duration. Peak accuracy was reached within 2000ms and two fixations to each face. However, intermixing exposure conditions produced a context effect that generally reduced accuracy on identity mismatch trials, even when unlimited viewing of faces was possible. These findings indicate that less than 2s are required for face matching when exposure times are variable, but temporal constraints should be avoided altogether if accuracy is truly paramount. The implications of these findings are discussed. Copyright © 2011 Elsevier Ltd. All rights reserved.

Space Exploration: Where We Have Been, Where We Are and Where We Are Going: A Human Perspective

NASA Technical Reports Server (NTRS)

Tripathi, R. K.

2005-01-01

NASA is moving forward towards the agency's new vision for space exploration in the 21st Century encompassing a broad range of human and robotic missions including missions to Moon, Mars and beyond. Exposure from the hazards of severe space radiation in deep space long duration missions is the show stopper. Langley has developed state-of-the-art radiation protection and shielding technology for space missions. The payload penalty demands a very stringent requirement on the design of the spacecrafts for human deep space missions. The exploration beyond low Earth orbit (LEO) to enable routine access to more interesting regions of space will require protection from the hazards of the accumulated exposures of space radiation, Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE), and minimizing the production of secondary radiation is a great advantage. The better understanding of radiation environment (GCR & SPE) and their interaction is a key to the success of the program due to the vital role and importance of cosmic rays for space missions.

Dose-response relationship between light exposure and cycling performance.

PubMed

Knaier, R; Meister, S; Aeschbacher, T; Gemperle, D; Rossmeissl, A; Cajochen, C; Schmidt-Trucksäss, A

2016-07-01

Light has a stimulating effect on physical performance if scheduled according to the chronotype, but dose-dependent effects on performance have not yet been examined. Three groups of healthy men (25.1 ± 3.1 years) were exposed to light for different durations in a parallel group design before a 40-min time-trial. In each group, subjects were exposed to either bright light (BL, 4420 lx) or moderate light (ML, 230 lx) in a randomized order in a crossover design. The durations of light exposure were 120 min prior to and during exercise (2HEX; n = 16), 60 min prior to and during exercise (1HEX; n = 10), or only for 60 min prior to exercise (1H; n = 15). Total work performed during the time-trial in kJ in the 2HEX group was significantly higher in the BL setting (527 kJ) than in ML (512 kJ) (P = 0.002), but not in 1HEX (BL: 485 kJ; ML: 498 kJ) or 1H (BL: 519 kJ; ML: 514 kJ) (P = 0.770; P = 0.485). There was a significant (P = 0.006) positive dose-response relationship between the duration of light exposure and the work performed over the three doses of light exposure. A long duration light exposure is an effective tool to increase total work in a medium length time-trial in subjects normalized for their individual chronotype. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Efficacy of Pseudomonas fluorescens (Pf-CL145A) spray dried powder for controlling zebra mussels adhering to test substrates

USGS Publications Warehouse

Luoma, James A.; Severson, Todd J.; Weber, Kerry L.; Mayer, Denise A.

2015-01-01

Approximately 30 days after exposure, zebra mussels were sorted into live and dead, and enumerated. Mean survival of zebra mussels in control treatments exceeded 95 percent. Mean survival of zebra mussels in the Lake Carlos WWC SDP-treated groups ranged from 0.5 to 2.1 percent and when compared at the same exposure duration, no difference was detected in survival between the 50 and 100 milligrams per liter (mg/L) treatment groups. Similarly, mean survival of zebra mussels in the Shawano Lake WWC SDP-treated groups ranged from 2.0 to 12.6 percent and when compared at the same exposure duration, no difference was detected in survival between the 50- and 100-mg/L treatment groups. Mean survival of zebra mussels in the Lake Carlos BI trial SDP-treated groups did not differ (p = 0.93) and was 18.1 and 18.0 percent in the 50- and 100-mg/L treatment groups, respectively. Mean survival of zebra mussels in the Shawano Lake BI trial SDP-treated groups differed (p < 0.01) and was 2.9 and 0.9 percent in the 50- and 100-mg/L treatment groups, respectively. Survival of zebra mussels assigned to the SDP-treated groups in the Lake Carlos WWC trial (12-hour exposure duration) differed from the survival of zebra mussels assigned to the SDP-treated groups in the Lake Carlos BI trial; however, after modification of the BI application technique, no difference (p = 0.22) was detected between the survival of zebra mussel in the Shawano Lake WWC (12-hour exposure duration) and BI trials.

Human exposure limits to hypergolic fuels

NASA Technical Reports Server (NTRS)

Garcia, H. D.; James, J. T.; Limero, T. F.

1992-01-01

Over the past four decades, many studies have been conducted on the toxicities of the rocket propellants hydrazine (HZ) and monomethylhydrazine (MH). Numerous technical challenges have made it difficult to unambiguously interpret the results of these studies, and there is considerable divergence between results obtained by different investigators on the inhalation concentrations (MAC's) for each toxic effect inducible by exposure to hypergolic fuels in spacecraft atmospheres, NASA undertook a critical review of published and unpublished investigations on the toxicities of these compounds. The current state of the art practices for similar studies. While many questions remain unanswered, MAC's were determined using the best available data for a variety of toxic endpoints for potential continuous exposure durations ranging from 1 hour to 180 days. Spacecraft MAC's (SMAC's) were set for each compound based on the most sensitive toxic endpoint at each exposure duration.

High altitude memory impairment is due to neuronal apoptosis in hippocampus, cortex and striatum.

PubMed

Maiti, Panchanan; Singh, Shashi B; Mallick, Birendranath; Muthuraju, Sangu; Ilavazhagan, Govindasami

2008-12-01

Cognitive and neuropsychological functions have been impaired at high altitude and the effects depend on altitude and duration of stay. However, the neurobiological mechanism of this impairment is poorly understood especially exposure to different duration. Aim of the present study was to investigate the changes of behavior, biochemistry and morphology after exposure to different duration of hypobaric hypoxia. The rats were exposed continuously to a simulated high altitude of 6100m for 3, 7, 14 and 21 days in an animal decompression chamber. Spatial reference memory was tested by Morris water maze. The oxidative stress markers like free radicals, NO, lipid peroxidation, LDH activity and antioxidant systems like GSH, GSSG, GPx, GR, SOD were estimated from cortex, hippocampus and striatum. The morphological changes, neurodegeneration, DNA fragmentation and mode of cell death have also been studied. It was observed that the spatial reference memory was significantly affected after exposure to hypobaric hypoxia. Increased oxidative stress markers along with decreased effectiveness of antioxidant system were also observed in hypoxia-exposed animals. Further pyknotic, shrunken, tangle-like neurons were observed in all these regions after hypoxia and neurodegeneration, DNA fragmentation and apoptosis were also observed in all the three regions. But after 21 days of exposure, the spatial memory was improved along with improvement of antioxidant activities. Our result suggests that the apoptotic death may be involved in HA-induced memory impairment and after 7 days of exposure the effect was more pronounced but after 21 days of exposure recovery was observed.

Salinity as a constraint on growth of oligohaline marsh macrophytes. II. Salt pulses and recovery potential

USGS Publications Warehouse

Howard, R.J.; Mendelssohn, I.A.

1999-01-01

The ability of common oligohaline marsh macrophytes of the northern Gulf of Mexico coast to recover from pulses of increased salinity was investigated in a greenhouse experiment with Eleocharis palustris, Panicum hemitomon, Sagittaria lancifolia, and Scirpus americanus monocultures. Components of salinity pulses applied were final salinity reached (6 or 12 g/L), salinity influx rate (3 d or 3 wk), and duration of exposure (1, 2, or 3 mo). After each exposure period, we placed plants into freshwater until the end of the 120-d experiment to determine recovery potential. The four species varied in their ability to recover from the salinity pulses. Within a species, recovery varied with final salinity level and duration of exposure, and to a lesser extent with salinity influx rate. Scirpus americanus, growth of which was stimulated by <3 mo of exposure to 6 g/L, was able to recover even under the most extreme conditions of exposure to 12 g/L salinity for 3 mo. Ability to recover decreased with increased salinity and increased duration of exposure for the remaining three species. Recovery of specific aspects of growth was also suppressed in these species by a rapid salinity influx rate compared to a slow influx rate. The complex variations in recovery patterns displayed by the different species may lead to changes in species dominance following the short-term salinity pulses that can occur during storm events, which in turn may affect marsh plant community composition and structure.

OZONE-INDUCED RESPIRATORY SYMPTOMS: EXPOSURE-RESPONSE MODELS AND ASSOCIATION WITH LUNG FUNCTION

EPA Science Inventory

Ozone-induced respiratory symptoms are known to be functions of concentration, minute ventilation, and duration of exposure. The purposes of this study were to identify an exposure-response model for symptoms, to determine whether response was related to age, and to assess the re...

CONCENTRATION - DURATION RELATIONSHIPS FOR NON-CANCER HEALTH EFFECTS OF EXPOSURE TO HAZARDOUS AIR POLLUTANTS.

EPA Science Inventory

EPA is charged with assessing the risks of both acute and chronic exposures to hazardous air pollutants
(HAPs). The emissions from sources of HAPs are often characterized as temporally-averaged values,
however, patterns of exposure not captured in such measures may infl...

PATTERN OF CHOLINESTERASE INHIBITION IN ADULT, MALE RATS CHRONICALLY EXPOSED TO DIETARY CHLORPYRIFOS.

EPA Science Inventory

Very little is known about the effects of chronic exposure to relatively low levels of anticholinesterase insecticides or how the effects of chronic exposure compare to higher, intermittent exposure of the same compound for the same duration. To that end, we exposed adult male ra...

Sensitivity of the vitellogenin assay: ability to discriminate among exposure concentrations in adult fathead minnow

EPA Science Inventory

Vitellogenin is often used to infer exposure of an organism to estrogenic substances. Vitellogenin gene induction and protein levels increase, up to a point, with concentration of estrogen and duration of exposure. A biomarker such as vitellogenin should exhibit sufficient sens...

Cumulative Estrogen Exposure and Prospective Memory in Older Women

ERIC Educational Resources Information Center

Hesson, Jacqueline

2012-01-01

This study looked at cumulative lifetime estrogen exposure, as estimated with a mathematical index (Index of Cumulative Estrogen Exposure (ICEE)) that included variables (length of time on estrogen therapy, age at menarche and menopause, postmenopausal body mass index, time since menopause, nulliparity and duration of breastfeeding) known to…

Effects of Exposure to Welding Fume on Lung Function: Results from the German WELDOX Study.

PubMed

Lehnert, M; Hoffmeyer, F; Gawrych, K; Lotz, A; Heinze, E; Berresheim, H; Merget, R; Harth, V; Van Gelder, R; Hahn, J-U; Hartwig, A; Weiß, T; Pesch, B; Brüning, T

2015-01-01

The association between exposure to welding fume and chronic obstructive pulmonary disease (COPD) has been insufficiently clarified. In this study we assessed the influence of exposure to welding fume on lung function parameters. We investigated forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC, and expiratory flow rates in 219 welders. We measured current exposure to respirable particles and estimated a worker's lifetime exposure considering welding techniques, working conditions and protective measures at current and former workplaces. Multiple regression models were applied to estimate the influence of exposure to welding fume, age, and smoking on lung function. We additionally investigated the duration of working as a welder and the predominant welding technique. The findings were that age- and smoking-adjusted lung function parameters showed no decline with increasing duration, current exposure level, and lifetime exposure to welding fume. However, 15% of the welders had FEV1/FVC below the lower limit of normal, but we could not substantiate the presence of an association with the measures of exposure. Adverse effects of cigarette smoking were confirmed. In conclusion, the study did not support the notion of a possible detrimental effect of exposure to welding fume on lung function in welders.

Sleep/wake patterns and circadian typology in preschool children based on standardized parental self-reports.

PubMed

Doi, Yuriko; Ishihara, Kaneyoshi; Uchiyama, Makoto

2014-04-01

We studied the sleep/wake patterns and circadian typology of Japanese preschool children living in the Tokyo metropolitan area (193 boys and 190 girls, 4-6 years of age) from June to July 2012 based on a standardized parental self-reporting questionnaire. Our major findings are as follows: (1) sleep/wake timing was delayed, and the duration of nocturnal sleep (sleep period as well as time in bed) increased from that on scheduled days (weekdays) to that on free days (weekends) for all ages. (2) The duration of daily sleep (24 h), including daytime nap, was longer for 4-year-old children compared with that in 5- to 6-year-old children, but not significantly different between scheduled and free days within each age group. (3) The distribution of chronotypes was 36.3% for morning (M)-type, 48.8% for neither (N)-type and 11.2% for evening (E)-type, and this distribution was independent of sex or age. (4) Sleep/wake timing delays were observed from M-type and N-type to E-type during scheduled and free days. (5) The duration of nocturnal sleep decreased but increased for 24-h sleep time from M-type and N-type to E-type on scheduled days. (6) Sleep durations did not differ among chronotypes on free days. (7) Chronotypes were associated with parents' diurnal preferences, mealtimes and attendance at kindergartens or childcare centers but not with sex, age, season of birth, exposure to multimedia or exposure to morning sunlight in their bedrooms. When these results were compared with those for older children and adolescents, similar sleep/wake patterns and circadian typology were observed, although to a lesser degree, in children as young as 4-6 years of age. Napping may compensate, in part, for an accumulated weekday sleep deficit. The distribution of chronotypes was associated with differences in sleep/wake timing and duration and was influenced by the parents' diurnal preferences and lifestyles. Further research on preschool children is required to investigate whether circadian typology affects their behavioral, emotional and cognitive development.

Critical disease windows shaped by stress exposure alter allocation trade-offs between development and immunity.

PubMed

Kirschman, Lucas J; Crespi, Erica J; Warne, Robin W

2018-01-01

Ubiquitous environmental stressors are often thought to alter animal susceptibility to pathogens and contribute to disease emergence. However, duration of exposure to a stressor is likely critical, because while chronic stress is often immunosuppressive, acute stress can temporarily enhance immune function. Furthermore, host susceptibility to stress and disease often varies with ontogeny; increasing during critical developmental windows. How the duration and timing of exposure to stressors interact to shape critical windows and influence disease processes is not well tested. We used ranavirus and larval amphibians as a model system to investigate how physiological stress and pathogenic infection shape development and disease dynamics in vertebrates. Based on a resource allocation model, we designed experiments to test how exposure to stressors may induce resource trade-offs that shape critical windows and disease processes because the neuroendocrine stress axis coordinates developmental remodelling, immune function and energy allocation in larval amphibians. We used wood frog larvae (Lithobates sylvaticus) to investigate how chronic and acute exposure to corticosterone, the dominant amphibian glucocorticoid hormone, mediates development and immune function via splenocyte immunohistochemistry analysis in association with ranavirus infection. Corticosterone treatments affected immune function, as both chronic and acute exposure suppressed splenocyte proliferation, although viral replication rate increased only in the chronic corticosterone treatment. Time to metamorphosis and survival depended on both corticosterone treatment and infection status. In the control and chronic corticosterone treatments, ranavirus infection decreased survival and delayed metamorphosis, although chronic corticosterone exposure accelerated rate of metamorphosis in uninfected larvae. Acute corticosterone exposure accelerated metamorphosis increased survival in infected larvae. Interactions between stress exposure (via glucocorticoid actions) and infection impose resource trade-offs that shape optimal allocation between development and somatic function. As a result, critical disease windows are likely shaped by stress exposure because any conditions that induce changes in differentiation rates will alter the duration and susceptibility of organisms to stressors or disease. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

Quality Matters: Systematic Analysis of Endpoints Related to “Cellular Life” in Vitro Data of Radiofrequency Electromagnetic Field Exposure

PubMed Central

Simkó, Myrtill; Remondini, Daniel; Zeni, Olga; Scarfi, Maria Rosaria

2016-01-01

Possible hazardous effects of radiofrequency electromagnetic fields (RF-EMF) at low exposure levels are controversially discussed due to inconsistent study findings. Therefore, the main focus of the present study is to detect if any statistical association exists between RF-EMF and cellular responses, considering cell proliferation and apoptosis endpoints separately and with both combined as a group of “cellular life” to increase the statistical power of the analysis. We searched for publications regarding RF-EMF in vitro studies in the PubMed database for the period 1995–2014 and extracted the data to the relevant parameters, such as cell culture type, frequency, exposure duration, SAR, and five exposure-related quality criteria. These parameters were used for an association study with the experimental outcome in terms of the defined endpoints. We identified 104 published articles, from which 483 different experiments were extracted and analyzed. Cellular responses after exposure to RF-EMF were significantly associated to cell lines rather than to primary cells. No other experimental parameter was significantly associated with cellular responses. A highly significant negative association with exposure condition-quality and cellular responses was detected, showing that the more the quality criteria requirements were satisfied, the smaller the number of detected cellular responses. According to our knowledge, this is the first systematic analysis of specific RF-EMF bio-effects in association to exposure quality, highlighting the need for more stringent quality procedures for the exposure conditions. PMID:27420084

Environmental and biological monitoring of benzene during self-service automobile refueling.

PubMed Central

Egeghy, P P; Tornero-Velez, R; Rappaport, S M

2000-01-01

Although automobile refueling represents the major source of benzene exposure among the nonsmoking public, few data are available regarding such exposures and the associated uptake of benzene. We repeatedly measured benzene exposure and uptake (via benzene in exhaled breath) among 39 self-service customers using self-administered monitoring, a technique rarely used to obtain measurements from the general public (130 sets of measurements were obtained). Benzene exposures averaged 2.9 mg/m(3) (SD = 5.8 mg/m(3); median duration = 3 min) with a range of < 0.076-36 mg/m(3), and postexposure breath levels averaged 160 microg/m(3) (SD = 260 microg/m(3)) with a range of < 3.2-1,400 microg/m(3). Log-transformed exposures and breath levels were significantly correlated (r = 0.77, p < 0.0001). We used mixed-effects statistical models to gauge the relative influences of environmental and subject-specific factors on benzene exposure and breath levels and to investigate the importance of various covariates obtained by questionnaire. Model fitting yielded three significant predictors of benzene exposure, namely, fuel octane grade (p = 0.0011), duration of exposure (p = 0.0054), and season of the year (p = 0.032). Likewise, another model yielded three significant predictors of benzene concentration in breath, specifically, benzene exposure (p = 0.0001), preexposure breath concentration (p = 0.0008), and duration of exposure (p = 0.038). Variability in benzene concentrations was remarkable, with 95% of the estimated values falling within a 274-fold range, and was comprised entirely of the within-person component of variance (representing exposures of the same subject at different times of refueling). The corresponding range for benzene concentrations in breath was 41-fold and was comprised primarily of the within-person variance component (74% of the total variance). Our results indicate that environmental rather than interindividual differences are primarily responsible for benzene exposure and uptake during automobile refueling. The study also demonstrates that self-administered monitoring can be efficiently used to measure environmental exposures and biomarkers among the general public. PMID:11133401

Antipsychotic Response Worsens With Postmenopausal Duration in Women With Schizophrenia.

PubMed

González-Rodríguez, Alexandre; Catalán, Rosa; Penadés, Rafael; Ruiz Cortés, Victoria; Torra, Mercè; Seeman, Mary V; Bernardo, Miquel

2016-12-01

The loss of estrogens in the menopause may lead to increased vulnerability for psychotic relapse, poor clinical outcome, and a need for increased antipsychotic dose. However, confounders such as cumulative estrogen exposure and time since menopause have been inadequately studied. Our aim was to investigate potential variables capable of influencing antipsychotic response in a sample of postmenopausal women with schizophrenia. Sixty-four postmenopausal schizophrenic women were followed in a 12-week prospective treatment-by-clinical requirement study. Duration of reproductive years was considered an indirect measure of lifetime cumulative estrogens exposure. Psychopathological assessment included the following: Positive and Negative Syndrome Scale, Personal and Social Performance, and Clinical Global Impression-Schizophrenia Scale. Response was defined as a reduction of 30% or more of Positive and Negative Syndrome Scale total scores. Antipsychotic adherence was assessed by plasma level monitoring at 4 weeks. Regression analyses were performed to investigate the association between potential confounding factors and antipsychotic response. Forty-two participants (66%) were found to be antipsychotic responders. Time since menopause was significantly and negatively associated with overall antipsychotic response, explaining almost 42% of the variance of the model used. Smoking and cumulative estrogen exposures were associated with improvement in negative symptoms. Smoking and time since menopause were associated with improvement in excitement symptoms, and smoking was positively associated with improvement in depressive and cognitive symptoms. Time since menopause was significantly negatively associated with antipsychotic response in postmenopausal schizophrenic women, suggesting a decline in antipsychotic response after menopause. The neurobiological basis for antipsychotic response may include a role for estrogen and nicotine receptors.

Gastrografin in Prolonged Postoperative Ileus: A Double-blinded Randomized Controlled Trial.

PubMed

Vather, Ryash; Josephson, Rachel; Jaung, Rebekah; Kahokehr, Arman; Sammour, Tarik; Bissett, Ian

2015-07-01

To investigate the therapeutic value of Gastrografin in shortening duration of prolonged postoperative ileus (PPOI) after elective colorectal surgery. Gut wall edema is central to the pathogenesis of PPOI. Hyperosmotic, orally administered, water-soluble contrast media such as Gastrografin are theoretically capable of mitigating this edema. A double-blinded, placebo-controlled, randomized trial was conducted. Participants were allocated to receive 100 mL of Gastrografin (Exposure Group) or flavored distilled water (Control Group) administered enterally. Other aspects of management were standardized. Resolution of PPOI was assessed 12-hourly. Eighty patients were randomized equally, with 5 in the Exposure Group and 4 in the Control Group excluded from analysis. Participants were evenly matched at baseline. Mean duration of PPOI did not differ between Exposure and Control Groups (83.7 vs 101.3 hours; P = 0.191). When considering individual markers of PPOI resolution, Gastrografin did not affect time to resolution of nausea and vomiting (64.5 vs 74.3 hours; P = 0.404) or consumption of oral diet (75.8 vs 90.0 hours; P = 0.297). However, it accelerated time to flatus or stool (18.9 vs 32.7 hours; P = 0.047) and time to resolution of abdominal distension (52.8 vs 77.7 hours; P = 0.013). There were no significant differences between groups in nasogastric output; analgesia, antiemetic, or fluid requirement; complications; or length of stay. Gastrografin is not clinically useful in shortening an episode of PPOI characterized by upper and lower gastrointestinal symptoms. It may however be of therapeutic benefit in the subset of PPOI patients who display lower gastrointestinal symptoms exclusively after surgery.

You have to be there to enjoy it? Neighbourhood social capital and health.

PubMed

Mohnen, Sigrid M; Völker, Beate; Flap, Henk; Subramanian, S V; Groenewegen, Peter P

2013-02-01

Several studies have shown the positive effect of neighbourhood social capital on health. Existing research, however, has hitherto not studied whether the duration and intensity of exposure to neighbourhood social capital conditions and its effect on health. The aim of this study was to examine whether neighbourhood social capital affects individual's health immediately and equally. We used two waves of the Dutch cross-sectional 'Housing and Living Survey'. One (from 2009) as individual data (n = 65,990), and the other (from 2006) to estimate with ecometric measurements a social capital measure for 3001 Dutch neighbourhoods. We assessed by means of multilevel regression models the combined effect of exposure and amount of neighbourhood social capital on self-rated health. Duration of exposure, measured by the length of stay in the same neighbourhood is not linearly associated with individual health. Health of people who live up to 6 years or >22 years in the same neighbourhood is not affected by neighbourhood social capital. People with young children in the household or elderly were assumed to be more intensively exposed. However, exposure intensity was only found to have an effect for households with young children. Duration and intensity of exposure to neighbourhood social capital, a social aspect of the environment, matters for people's health. Interventions focusing on the health of people with young children may want to stimulate the creation of neighbourhood social capital.

[Electromagnetic hazards from electrosurgery--assessment of occupational exposure to electromagnetic field and currents induceed in the body].

PubMed

Gryz, Krzysztof; Karpowicz, Jolanta

2006-01-01

The investigation of the occupational exposure to electromagnetic fields from electrosurgery devices were done (according to the requirements of Polish Standard PN-T-06580:2002). The exposure was evaluated following the criteria established by occupational safety and health regulations. The measurements and evaluation of the currents flowing through the exposed workers body were also conducted following the method and criteria published by IEEE standard and European Directive 2004/40/EC. It was found that in the vicinity of electrosurgical devices, the area of electromagnetic fields to which only workers operating the source of field should be exposed can exist up to the distance of 70 cm from the active electrode and supplying cables. In the case when the cables are placed directly on the surgeon body or long duration of the daily exposure the overexposure of workers can appear (referring to Polish regulations). The current flowing through the arm of surgeon keeping the electrode with electric field of the maximum strength (app. 1000 V/m or higher) can exceed permissible value of 40 mA established by the Directive 2004/40/EC for contact current. The reduction of the surgeon exposure can be reached by the proper positioning of the cables supplying monopolar electrode or by the use of bipolar electrode.

Vernalizing cold is registered digitally at FLC.

PubMed

Angel, Andrew; Song, Jie; Yang, Hongchun; Questa, Julia I; Dean, Caroline; Howard, Martin

2015-03-31

A fundamental property of many organisms is an ability to sense, evaluate, and respond to environmental signals. In some situations, generation of an appropriate response requires long-term information storage. A classic example is vernalization, where plants quantitatively sense long-term cold and epigenetically store this cold-exposure information to regulate flowering time. In Arabidopsis thaliana, stable epigenetic memory of cold is digital: following long-term cold exposure, cells respond autonomously in an all-or-nothing fashion, with the fraction of cells that stably silence the floral repressor flowering locus C (FLC) increasing with the cold exposure duration. However, during cold exposure itself it is unknown whether vernalizing cold is registered at FLC in individual cells in an all-or-nothing (digital) manner or is continuously varying (analog). Using mathematical modeling, we found that analog registration of cold temperature is problematic due to impaired analog-to-digital conversion into stable memory. This disadvantage is particularly acute when responding to short cold periods, but is absent when cold temperatures are registered digitally at FLC. We tested this prediction experimentally, exposing plants to short periods of cold interrupted with even shorter warm breaks. For FLC expression, we found that the system responds similarly to both interrupted and uninterrupted cold, arguing for a digital mechanism integrating long-term temperature exposure.

Vernalizing cold is registered digitally at FLC

PubMed Central

Angel, Andrew; Song, Jie; Yang, Hongchun; Questa, Julia I.; Dean, Caroline; Howard, Martin

2015-01-01

A fundamental property of many organisms is an ability to sense, evaluate, and respond to environmental signals. In some situations, generation of an appropriate response requires long-term information storage. A classic example is vernalization, where plants quantitatively sense long-term cold and epigenetically store this cold-exposure information to regulate flowering time. In Arabidopsis thaliana, stable epigenetic memory of cold is digital: following long-term cold exposure, cells respond autonomously in an all-or-nothing fashion, with the fraction of cells that stably silence the floral repressor FLOWERING LOCUS C (FLC) increasing with the cold exposure duration. However, during cold exposure itself it is unknown whether vernalizing cold is registered at FLC in individual cells in an all-or-nothing (digital) manner or is continuously varying (analog). Using mathematical modeling, we found that analog registration of cold temperature is problematic due to impaired analog-to-digital conversion into stable memory. This disadvantage is particularly acute when responding to short cold periods, but is absent when cold temperatures are registered digitally at FLC. We tested this prediction experimentally, exposing plants to short periods of cold interrupted with even shorter warm breaks. For FLC expression, we found that the system responds similarly to both interrupted and uninterrupted cold, arguing for a digital mechanism integrating long-term temperature exposure. PMID:25775579

Application of in Vitro Biotransformation Data and ...

EPA Pesticide Factsheets

The adverse biological effects of toxic substances are dependent upon the exposure concentration and the duration of exposure. Pharmacokinetic models can quantitatively relate the external concentration of a toxicant in the environment to the internal dose of the toxicant in the target tissues of an exposed organism. The exposure concentration of a toxic substance is usually not the same as the concentration of the active form of the toxicant that reaches the target tissues following absorption, distribution, and biotransformation of the parent toxicant. Biotransformation modulates the biological activity of chemicals through bioactivation and detoxication pathways. Many toxicants require biotransformation to exert their adverse biological effects. Considerable species differences in biotransformation and other pharmacokinetic processes can make extrapolation of toxicity data from laboratory animals to humans problematic. Additionally, interindividual differences in biotransformation among human populations with diverse genetics and lifestyles can lead to considerable variability in the bioactivation of toxic chemicals. Compartmental pharmacokinetic models of animals and humans are needed to understand the quantitative relationships between chemical exposure and target tissue dose as well as animal to human differences and interindividual differences in human populations. The data-based compartmental pharmacokinetic models widely used in clinical pharmacology ha

Maternal serum perfluoroalkyl substances during pregnancy and duration of breastfeeding

PubMed Central

Romano, Megan E.; Xu, Yingying; Calafat, Antonia M.; Yolton, Kimberly; Chen, Aimin; Webster, Glenys M.; Eliot, Melissa N.; Howard, Cynthia R.; Lanphear, Bruce P.; Braun, Joseph M.

2016-01-01

Background Perfluoroalkyl substances (PFAS) may affect breast development and decrease duration of breastfeeding, thus interfering with the health benefits of breastfeeding. We investigated the association between maternal PFAS exposure and breastfeeding duration. Methods We measured PFAS concentrations in maternal serum collected during pregnancy in 2003–2006. After delivery, women (n=336) completed standardized breastfeeding surveys every 3 months until ending breastfeeding or 36 months postpartum. We estimated relative risks (RRs) for ending any breastfeeding within 3 or 6 months postpartum by Poisson regression, adjusted for relevant confounding factors. Results Women in the 4th quartile of perfluorooctanoic acid (PFOA) serum concentration had 1.77 times the risk of ending any breastfeeding by 3 months (95% confidence interval (CI): 1.23, 2.54; p-trend=0.003) and 1.41 times the risk of ending any breastfeeding by 6 months (95%CI: 1.06, 1.87; p-trend=0.038), compared with women in the first quartile. Women in the 4th quartile of perfluorooctane sulfonic acid serum concentration had a marginally increased risk of discontinuing any breastfeeding by 3 months (RR=1.32; 95%CI: 0.97, 1.79; p-trend=0.065). Conclusions Maternal serum PFOA concentrations were inversely related to duration of any breastfeeding in this cohort, even after controlling for prior breastfeeding. These findings suggest that PFOA exposure may adversely affect breastfeeding duration and highlight the need to consider the potential adverse effects of maternal environmental chemical exposure on breastfeeding. PMID:27179585

Summary of ionizing radiation analysis on the Long Duration Exposure Facility

NASA Technical Reports Server (NTRS)

Parnell, T. A.

1991-01-01

The Ionizing Radiation Special Investigation Group (IRSIG) for the Long Duration Exposure Facility (LDEF) was established to perform radiation measurements and analysis not planned in the original experiments, and to assure availability of LDEF analysis results in a form useful to future missions. The IRSIG has organized extensive induced radioactivity measurements throughout LDEF, and a comprehensive program to compare the LDEF radiation measurements to values calculated using environment models. The activities and present status of the Group is described. The ionizing radiation results presented is summarized.

Analysis of systems hardware flown on LDEF. Results of the systems special investigation group

NASA Technical Reports Server (NTRS)

Dursch, Harry W.; Spear, W. Steve; Miller, Emmett A.; Bohnhoff-Hlavacek, Gail L.; Edelman, Joel

1992-01-01

The Long Duration Exposure Facility (LDEF) was retrieved after spending 69 months in low Earth orbit (LEO). LDEF carried a remarkable variety of mechanical, electrical, thermal, and optical systems, subsystems, and components. The Systems Special Investigation Group (Systems SIG) was formed to investigate the effects of the long duration exposure to LEO on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. Discussed here is the status of the LDEF Systems SIG investigation through the end of 1991.

Analysis of systems hardware flown on LDEF. Results of the systems special investigation group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dursch, H.W.; Spear, W.S.; Miller, E.A.

1992-04-01

The Long Duration Exposure Facility (LDEF) was retrieved after spending 69 months in low Earth orbit (LEO). LDEF carried a remarkable variety of mechanical, electrical, thermal, and optical systems, subsystems, and components. The Systems Special Investigation Group (Systems SIG) was formed to investigate the effects of the long duration exposure to LEO on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. Discussed here is the status of the LDEF Systems SIG investigation through the end of 1991.

The role of the Long Duration Exposure Facility in the development of space systems

NASA Technical Reports Server (NTRS)

Little, Sally A.

1992-01-01

The Long Duration Exposure Facility (LDEF) presents the international, aerospace community with an unprecedented opportunity to examine the synergistic, long term, space environmental effects on systems and materials. The analysis of the data within appropriate environmental contexts is essential to the overall process of advancing the understanding of space environmental effects needed for the continuing development of strategies to improve the reliability and durability of space systems and to effectively deal with the future challenges that new space initiatives will likely present.

Long duration exposure facility post-flight thermal analysis: Orbital/thermal environment data package

NASA Technical Reports Server (NTRS)

Berrios, William M.

1990-01-01

A post flight mission thermal environment for the Long Duration Exposure Facility was created as part of the thermal analysis data reduction effort. The data included herein is the thermal parameter data used in the calculation of boundary temperatures. This boundary temperature data is to be released in the near future for use by the LDEF principal investigators in the final analysis of their particular experiment temperatures. Also included is the flight temperature data as recorded by the LDEF Thermal Measurements System (THERM) for the first 90 days of flight.

Modelling of occupational respirable crystalline silica exposure for quantitative exposure assessment in community-based case-control studies.

PubMed

Peters, Susan; Vermeulen, Roel; Portengen, Lützen; Olsson, Ann; Kendzia, Benjamin; Vincent, Raymond; Savary, Barbara; Lavoué, Jérôme; Cavallo, Domenico; Cattaneo, Andrea; Mirabelli, Dario; Plato, Nils; Fevotte, Joelle; Pesch, Beate; Brüning, Thomas; Straif, Kurt; Kromhout, Hans

2011-11-01

We describe an empirical model for exposure to respirable crystalline silica (RCS) to create a quantitative job-exposure matrix (JEM) for community-based studies. Personal measurements of exposure to RCS from Europe and Canada were obtained for exposure modelling. A mixed-effects model was elaborated, with region/country and job titles as random effect terms. The fixed effect terms included year of measurement, measurement strategy (representative or worst-case), sampling duration (minutes) and a priori exposure intensity rating for each job from an independently developed JEM (none, low, high). 23,640 personal RCS exposure measurements, covering a time period from 1976 to 2009, were available for modelling. The model indicated an overall downward time trend in RCS exposure levels of -6% per year. Exposure levels were higher in the UK and Canada, and lower in Northern Europe and Germany. Worst-case sampling was associated with higher reported exposure levels and an increase in sampling duration was associated with lower reported exposure levels. Highest predicted RCS exposure levels in the reference year (1998) were for chimney bricklayers (geometric mean 0.11 mg m(-3)), monument carvers and other stone cutters and carvers (0.10 mg m(-3)). The resulting model enables us to predict time-, job-, and region/country-specific exposure levels of RCS. These predictions will be used in the SYNERGY study, an ongoing pooled multinational community-based case-control study on lung cancer.

NASA Astronaut Occupational Surveillance Program and Lifetime Surveillance of Astronaut Health, LSAH, Astronaut Exposures and Risk in the Terrestrial and Spaceflight Environment

NASA Technical Reports Server (NTRS)

Keprta, Sean R.; Tarver, William; Van Baalen, Mary; McCoy, Torin

2015-01-01

United States Astronauts have a very unique occupational exposure profile. In order to understand these risks and properly address them, the National Aeronautics and Atmospheric Administration, NASA, originally created the Longitudinal Study of Astronaut Health, LSAH. The first LSAH was designed to address a variety of needs regarding astronaut health and included a 3 to 1 terrestrial control population in order to compare United States "earth normal" disease and aging to that of a microgravity exposed astronaut. Over the years that program has been modified, now termed Lifetime Surveillance of Astronaut Health, still LSAH. Astronaut spaceflight exposures have also changed, with the move from short duration shuttle flights to long duration stays on international space station and considerable terrestrial training activities. This new LSAH incorporates more of an occupational health and medicine model to the study of occupationally exposed astronauts. The presentation outlines the baseline exposures and monitoring of the astronaut population to exposures, both terrestrial, and in space.

Model of spacecraft atomic oxygen and solar exposure microenvironments

NASA Technical Reports Server (NTRS)

Bourassa, R. J.; Pippin, H. G.

1993-01-01

Computer models of environmental conditions in Earth orbit are needed for the following reasons: (1) derivation of material performance parameters from orbital test data, (2) evaluation of spacecraft hardware designs, (3) prediction of material service life, and (4) scheduling spacecraft maintenance. To meet these needs, Boeing has developed programs for modeling atomic oxygen (AO) and solar radiation exposures. The model allows determination of AO and solar ultraviolet (UV) radiation exposures for spacecraft surfaces (1) in arbitrary orientations with respect to the direction of spacecraft motion, (2) overall ranges of solar conditions, and (3) for any mission duration. The models have been successfully applied to prediction of experiment environments on the Long Duration Exposure Facility (LDEF) and for analysis of selected hardware designs for deployment on other spacecraft. The work on these models has been reported at previous LDEF conferences. Since publication of these reports, a revision has been made to the AO calculation for LDEF, and further work has been done on the microenvironments model for solar exposure.

Human epidemiology: A review of fiber type and characteristics in the development of malignant and nonmalignant disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merchant, J.A.

1990-08-01

Consideration of the human epidemiology of diseases arising from exposure to naturally occurring and man-made mineral fibers encompasses the several forms of asbestos, other naturally occurring silicates, and man-made mineral fibers. The diseases arising from exposures to some of these fibers include pleural thickening, pulmonary fibrosis, lung cancers, mesothelioma of the pleura and peritoneum, and other cancers. Risk factors important in assessing these diseases include assessment of latency, duration of exposure, cumulative exposure, fiber origin and characteristics, other possible confounding occupational or environmental exposures, and smoking. Methodological issues commonly presenting problems in evaluation of these data include assessment of themore » adequacy of environmental exposures, particularly in regard to fiber identification, distribution, and concentration over the duration of exposure, and the adequacy of study design to detect health effects. Research priorities include further assessment and standardization of pleural thickening relative to fiber exposure, uniform mesothelioma surveillance, further epidemiological assessment of certain silicate and man-made mineral fiber cohorts with emphasis given to assessment of tremolite and small diameter glass and ceramic fibers. Further assessment of possible health risks of the general public should await improved definition of relevant fiber exposure in ambient air.« less

Development of acute exposure guideline levels for airborne exposures to hazardous substances.

PubMed

Krewski, Daniel; Bakshi, Kulbir; Garrett, Roger; Falke, Ernest; Rusch, George; Gaylor, David

2004-04-01

Hazardous substances can be released into the atmosphere due to industrial and transportation accidents, fires, tornadoes, earthquakes, and terrorists, thereby exposing workers and the nearby public to potential adverse health effects. Various enforceable guidelines have been set by regulatory agencies for worker and ambient air quality. However, these exposure levels generally are not applicable to rare lifetime acute exposures, which possibly could occur at high concentrations. Acute exposure guideline levels (AEGLs) provide estimates of concentrations for airborne exposures for an array of short durations that possibly could cause mild (AEGL-1), severe, irreversible, potentially disabling adverse health effects (AEGL-2), or life threatening effects (AEGL-3). These levels can be useful for emergency responders and planners in reducing or eliminating potential risks to the public. Procedures and methodologies for deriving AEGLs are reviewed in this paper that have been developed in the United States, with direct input from international representatives of OECD member-countries, by the National Advisory Committee for Acute Exposure Guidelines for Hazardous Substances and reviewed by the National Research Council. Techniques are discussed for the extrapolation of effects across different exposure durations. AEGLs provide a viable approach for assisting in the prevention, planning, and response to acute airborne exposures to toxic agents.

A Method for Semi-quantitative Assessment of Exposure to Pesticides of Applicators and Re-entry Workers: An Application in Three Farming Systems in Ethiopia.

PubMed

Negatu, Beyene; Vermeulen, Roel; Mekonnen, Yalemtshay; Kromhout, Hans

2016-07-01

To develop an inexpensive and easily adaptable semi-quantitative exposure assessment method to characterize exposure to pesticide in applicators and re-entry farmers and farm workers in Ethiopia. Two specific semi-quantitative exposure algorithms for pesticides applicators and re-entry workers were developed and applied to 601 farm workers employed in 3 distinctly different farming systems [small-scale irrigated, large-scale greenhouses (LSGH), and large-scale open (LSO)] in Ethiopia. The algorithm for applicators was based on exposure-modifying factors including application methods, farm layout (open or closed), pesticide mixing conditions, cleaning of spraying equipment, intensity of pesticide application per day, utilization of personal protective equipment (PPE), personal hygienic behavior, annual frequency of application, and duration of employment at the farm. The algorithm for re-entry work was based on an expert-based re-entry exposure intensity score, utilization of PPE, personal hygienic behavior, annual frequency of re-entry work, and duration of employment at the farm. The algorithms allowed estimation of daily, annual and cumulative lifetime exposure for applicators, and re-entry workers by farming system, by gender, and by age group. For all metrics, highest exposures occurred in LSGH for both applicators and female re-entry workers. For male re-entry workers, highest cumulative exposure occurred in LSO farms. Female re-entry workers appeared to be higher exposed on a daily or annual basis than male re-entry workers, but their cumulative exposures were similar due to the fact that on average males had longer tenure. Factors related to intensity of exposure (like application method and farm layout) were indicated as the main driving factors for estimated potential exposure. Use of personal protection, hygienic behavior, and duration of employment in surveyed farm workers contributed less to the contrast in exposure estimates. This study indicated that farmers' and farm workers' exposure to pesticides can be inexpensively characterized, ranked, and classified. Our method could be extended to assess exposure to specific active ingredients provided that detailed information on pesticides used is available. The resulting exposure estimates will consequently be used in occupational epidemiology studies in Ethiopia and other similar countries with few resources. © The Author 2016. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Association between multi-level inorganic arsenic exposure from drinking water and skin lesions in China.

PubMed

Guo, Xiaojuan; Fujino, Yoshihisa; Ye, Xiaolei; Liu, Jun; Yoshimura, Takesumi

2006-09-01

Arsenic is one of the most important toxicants in the environment. In Inner Mongolia of China, 300,000 residents are believed to be drinking water containing >50 microg/liter. Skin lesions have been known as the most common consequences resulting from chronic exposure to arsenic. To clarify the prevalence of arsenic-induced skin lesions, it is important to assess the impact of this problem among the target population, and to make future planning. We evaluated the association between multi-levels inorganic arsenic exposure from drinking water and skin lesions in an arsenic-affected area in Inner Mongolia, China. One hundred nine and 32 subjects in high (>50 microg/liter) and low (<50 microg/liter) arsenic-affected villages were recruited and had the detailed physical examination with special emphasis on arsenic-related skin lesions. Arsenic exposure was measured for each participant with respect to iAs concentration of primary well and the duration using the well. Arsenic-induced skin lesions including keratosis, pigmentation, and/or depigmentation were diagnosed in 56 and 3 subjects in the two villages, respectively. Logistic regression was conducted to calculate odd ratios of skin lesions associated with arsenic exposure with adjustments for sex, age group, smoking and duration of exposure. A consistent dose-response relationship between arsenic exposure level and skin lesion risk was observed. Compared to those with iAs concentration <50 microg/liter, the adjusted odds ratios of skin lesions for the subjects with 51-99, 100-149 and >150 microg/liter were 33.3% (OR =15.50, 95% CI: 1.53-248.70), 46.7% (OR =16.10, 95% CI: 3.73-69.63) and 55.7% (OR= 25.70, 95% CI: 6.43-102.87), respectively. Duration of using well was not associated with increased risk of skin lesions in this population; (OR =1.68, 95% CI: 0.40-6.91 for 6-15 years, OR = 2.30, 95% CI: 0.58-9.14 for over 15 years) compared with the duration of less than 5 years.

The Effects of "Mere Exposure" on Learning and Affect.

ERIC Educational Resources Information Center

Stang, David J.

The mediating role of learning in the relationship between repeated exposure and affect was explored and supported in three experiments involving a total of 229 undergraduate participants. It was found that both learning and affect measures behaved in essentially the same way as a function of exposure duration (experiments I and III), serial…

MOVING FROM EXTERNAL EXPOSURE CONCENTRATION TO INTERNAL DOSE: DURATION EXTRAPOLATION BASED ON PHYSIOLOGICALLY-BASED PHARMACOKINETIC-MODEL DERIVED ESTIMATES OF INTERNAL DOSE

EPA Science Inventory

The potential human health risk(s) from exposure to chemicals under conditions for which adequate human or animal data are not available must frequently be assessed. Exposure scenario is particularly important for the acute neurotoxic effects of volatile organic compounds (VOCs)...

The Fort Collins Commuter Study: Impact of route type and transport mode on personal exposure to multiple air pollutants.

PubMed

Good, Nicholas; Mölter, Anna; Ackerson, Charis; Bachand, Annette; Carpenter, Taylor; Clark, Maggie L; Fedak, Kristen M; Kayne, Ashleigh; Koehler, Kirsten; Moore, Brianna; L'Orange, Christian; Quinn, Casey; Ugave, Viney; Stuart, Amy L; Peel, Jennifer L; Volckens, John

2016-06-01

Traffic-related air pollution is associated with increased mortality and morbidity, yet few studies have examined strategies to reduce individual exposure while commuting. The present study aimed to quantify how choice of mode and route type affects personal exposure to air pollutants during commuting. We analyzed within-person difference in exposures to multiple air pollutants (black carbon (BC), carbon monoxide (CO), ultrafine particle number concentration (PNC), and fine particulate matter (PM2.5)) during commutes between the home and workplace for 45 participants. Participants completed 8 days of commuting by car and bicycle on direct and alternative (reduced traffic) routes. Mean within-person exposures to BC, PM2.5, and PNC were higher when commuting by cycling than when driving, but mean CO exposure was lower when cycling. Exposures to CO and BC were reduced when commuting along alternative routes. When cumulative exposure was considered, the benefits from cycling were attenuated, in the case of CO, or exacerbated, in the case of particulate exposures, owing to the increased duration of the commute. Although choice of route can reduce mean exposure, the effect of route length and duration often offsets these reductions when cumulative exposure is considered. Furthermore, increased ventilation rate when cycling may result in a more harmful dose than inhalation at a lower ventilation rate.

The Fort Collins Commuter Study: Impact of route type and transport mode on personal exposure to multiple air pollutants

PubMed Central

Good, Nicholas; Mölter, Anna; Ackerson, Charis; Bachand, Annette; Carpenter, Taylor; Clark, Maggie L; Fedak, Kristen M; Kayne, Ashleigh; Koehler, Kirsten; Moore, Brianna; L'Orange, Christian; Quinn, Casey; Ugave, Viney; Stuart, Amy L; Peel, Jennifer L; Volckens, John

2016-01-01

Traffic-related air pollution is associated with increased mortality and morbidity, yet few studies have examined strategies to reduce individual exposure while commuting. The present study aimed to quantify how choice of mode and route type affects personal exposure to air pollutants during commuting. We analyzed within-person difference in exposures to multiple air pollutants (black carbon (BC), carbon monoxide (CO), ultrafine particle number concentration (PNC), and fine particulate matter (PM2.5)) during commutes between the home and workplace for 45 participants. Participants completed 8 days of commuting by car and bicycle on direct and alternative (reduced traffic) routes. Mean within-person exposures to BC, PM2.5, and PNC were higher when commuting by cycling than when driving, but mean CO exposure was lower when cycling. Exposures to CO and BC were reduced when commuting along alternative routes. When cumulative exposure was considered, the benefits from cycling were attenuated, in the case of CO, or exacerbated, in the case of particulate exposures, owing to the increased duration of the commute. Although choice of route can reduce mean exposure, the effect of route length and duration often offsets these reductions when cumulative exposure is considered. Furthermore, increased ventilation rate when cycling may result in a more harmful dose than inhalation at a lower ventilation rate. PMID:26507004

Seeds in space experiment. [long duration exposure facility

NASA Technical Reports Server (NTRS)

Alston, Jim A.

1992-01-01

Two million seeds of 120 different varieties representing 106 species, 97 genera, and 55 plant families were flown aboard the Long Duration Exposure Facility (LDEF). The seeds were housed in one sealed canister and in two small vented canisters. After being returned to earth, the seeds were germinated and the germination rates and development of the resulting plants were compared to the performance of the control seeds that stayed in the Park Seed's seed storage facility. There was a better survival rate in the sealed canister in space than at the storage facility at Park Seed. At least some of the seeds in each of the vented canisters survived the exposure to vacuum for almost six years. The number of observed apparent mutations was very low.

Risk of brain tumors from wireless phone use.

PubMed

Dubey, Rash Bihari; Hanmandlu, Madasu; Gupta, Suresh Kumar

2010-01-01

The debate regarding the health effects of low-intensity electromagnetic radiation from sources such as power lines, base stations, and cell phones has recently been reignited. Wireless communication has dramatically influenced our lifestyle; its impact on human health has not been completely assessed. Widespread concern continues in the community about the deleterious effects of radiofrequency radiations on human tissues and the subsequent potential threat of carcinogenesis. Exposure to low-frequency electromagnetic field has been linked to a variety of adverse health outcomes. This article surveys the results of early cell phone studies, where exposure duration was too short to expect tumor genesis, and 2 sets of more recent studies with longer exposure duration: the Interphone studies and the Swedish studies led by Hardell.

Asbestos Exposure Assessment Database

NASA Technical Reports Server (NTRS)

Arcot, Divya K.

2010-01-01

Exposure to particular hazardous materials in a work environment is dangerous to the employees who work directly with or around the materials as well as those who come in contact with them indirectly. In order to maintain a national standard for safe working environments and protect worker health, the Occupational Safety and Health Administration (OSHA) has set forth numerous precautionary regulations. NASA has been proactive in adhering to these regulations by implementing standards which are often stricter than regulation limits and administering frequent health risk assessments. The primary objective of this project is to create the infrastructure for an Asbestos Exposure Assessment Database specific to NASA Johnson Space Center (JSC) which will compile all of the exposure assessment data into a well-organized, navigable format. The data includes Sample Types, Samples Durations, Crafts of those from whom samples were collected, Job Performance Requirements (JPR) numbers, Phased Contrast Microscopy (PCM) and Transmission Electron Microscopy (TEM) results and qualifiers, Personal Protective Equipment (PPE), and names of industrial hygienists who performed the monitoring. This database will allow NASA to provide OSHA with specific information demonstrating that JSC s work procedures are protective enough to minimize the risk of future disease from the exposures. The data has been collected by the NASA contractors Computer Sciences Corporation (CSC) and Wyle Laboratories. The personal exposure samples were collected from devices worn by laborers working at JSC and by building occupants located in asbestos-containing buildings.

Prolonged exposure to acetaminophen reduces testosterone production by the human fetal testis in a xenograft model

PubMed Central

Anderson, Richard A.; Johnston, Zoe C.; Chetty, Tarini; Smith, Lee B.; Mckinnell, Chris; Dean, Afshan; Homer, Natalie Z.; Jorgensen, Anne; Camacho-Moll, Maria-Elena; Sharpe, Richard M.; Mitchell, Rod T.

2016-01-01

Most common male reproductive disorders are linked to lower testosterone exposure in fetal life, although the factors responsible for suppressing fetal testosterone remain largely unknown. Protracted use of acetaminophen during pregnancy is associated with increased risk of cryptorchidism in sons, but effects on fetal testosterone production have not been demonstrated. We used a validated xenograft model to expose human fetal testes to clinically relevant doses and regimens of acetaminophen. Exposure to a therapeutic dose of acetaminophen for 7 days significantly reduced plasma testosterone (45% reduction; p=0.025) and seminal vesicle weight (a biomarker of androgen exposure; 18% reduction; p=0.005) in castrate host mice bearing human fetal testis xenografts, whereas acetaminophen exposure for just 1 day did not alter either parameter. Plasma acetaminophen concentrations (at 1 hour after the final dose) in exposed host mice were substantially below those reported in humans after a therapeutic oral dose. Subsequent in utero exposure studies in rats indicated that the acetaminophen-induced reduction in testosterone likely results from reduced expression of key steroidogenic enzymes (Cyp11a1, Cyp17a1). Our results suggest that protracted use of acetaminophen (1 week) may suppress fetal testosterone production, which could have adverse consequences. Further studies are required to establish the dose-response and treatment-duration relationships to delineate the maximum dose and treatment period without this adverse effect. PMID:25995226

Vessel Noise Affects Beaked Whale Behavior: Results of a Dedicated Acoustic Response Study

DTIC Science & Technology

2012-08-01

the analysis. Gaussian Models Shapiro-Wilk test (Normality) Breusch - Pagan test (Heteroscedasticity) Durbin-Watson test (Independence) Foraging duration...noise) may disrupt behavior. An experiment involving the exposure of target whale groups to intense vessel-generated noise tested how these exposures...exposure of target whale groups to intense vessel-generated noise tested how these exposures influenced the foraging behavior of Blainville?s beaked

Retrospective exposure assessment to airborne asbestos among power industry workers

PubMed Central

2010-01-01

Background A method of individually assessing former exposure to asbestos fibres is a precondition of risk-differentiated health surveillance. The main aims of our study were to assess former levels of airborne asbestos exposure in the power industry in Germany and to propose a basic strategy for health surveillance and the early detection of asbestos related diseases. Methods Between March 2002 and the end of 2006, we conducted a retrospective questionnaire based survey of occupational tasks and exposures with airborne asbestos fibres in a cohort of 8632 formerly asbestos exposed power industry workers. The data on exposure and occupation were entered into a specially designed computer programme, based on ambient monitoring of airborne asbestos fibre concentrations. The cumulative asbestos exposure was expressed as the product of the eight-hour time weighted average and the total duration of exposure in fibre years (fibres/cubic centimetre-years). Results Data of 7775 (90% of the total) participants working in installations for power generation, power distribution or gas supply could be evaluated. The power generation group (n = 5284) had a mean age of 56 years, were exposed for 20 years and had an average cumulative asbestos exposure of 42 fibre years. The occupational group of "metalworkers" (n = 1600) had the highest mean value of 79 fibre years. The corresponding results for the power distribution group (n = 2491) were a mean age of 45 years, a mean exposure duration of 12 years and an average cumulative asbestos exposure of only 2.5 fibre years. The gas supply workers (n = 512) had a mean age of 54 years and a mean duration of exposure of 15 years. Conclusions While the surveyed cohort as a whole was heavily exposed to asbestos dust, the power distribution group had a mean cumulative exposure of only 6% of that found in the power generation group. Based on the presented data, risk-differentiated disease surveillance focusing on metalworkers and electricians from the power generating industry seems justified. That combined with a sensitive examination technique would allow detecting asbestos related diseases early and efficiently. PMID:20579364

Predictors of post-partum damage accrual in systemic lupus erythematosus: data from LUMINA, a multiethnic US cohort (XXXVIII).

PubMed

Andrade, R M; McGwin, G; Alarcón, G S; Sanchez, M L; Bertoli, A M; Fernández, M; Fessler, B J; Apte, M; Arango, A M; Bastian, H M; Vilá, L M; Reveille, J D

2006-11-01

To determine the impact of pregnancy on systemic lupus erythematosus (SLE) outcome. SLE patients, age >or=16 yrs, disease duration

Active magnetic radiation shielding system analysis and key technologies.

PubMed

Washburn, S A; Blattnig, S R; Singleterry, R C; Westover, S C

2015-01-01

Many active magnetic shielding designs have been proposed in order to reduce the radiation exposure received by astronauts on long duration, deep space missions. While these designs are promising, they pose significant engineering challenges. This work presents a survey of the major systems required for such unconfined magnetic field design, allowing the identification of key technologies for future development. Basic mass calculations are developed for each system and are used to determine the resulting galactic cosmic radiation exposure for a generic solenoid design, using a range of magnetic field strength and thickness values, allowing some of the basic characteristics of such a design to be observed. This study focuses on a solenoid shaped, active magnetic shield design; however, many of the principles discussed are applicable regardless of the exact design configuration, particularly the key technologies cited. Copyright © 2015 The Committee on Space Research (COSPAR). All rights reserved.

LDEF materials special investigation group's data bases

NASA Technical Reports Server (NTRS)

Strickland, John W.; Funk, Joan G.; Davis, John M.

1993-01-01

The Long Duration Exposure Facility (LDEF) was composed of and contained a wide array of materials, representing the largest collection of materials flown for space exposure and returned for ground-based analyses to date. The results and implications of the data from these materials are the foundation on which future space missions will be built. The LDEF Materials Special Investigation Group (MSIG) has been tasked with establishing and developing data bases to document these materials and their performance to assure not only that the data are archived for future generations but also that the data are available to the space user community in an easily accessed, user-friendly form. The format and content of the data bases developed or being developed to accomplish this task are discussed. The hardware and software requirements for each of the three data bases are discussed along with current availability of the data bases.

Characteristics of injury and recovery of net NO3- transport of barley seedlings from treatments of NaCl

NASA Technical Reports Server (NTRS)

Klobus, G.; Ward, M. R.; Huffaker, R. C.

1988-01-01

The nature of the injury and recovery of nitrate uptake (net uptake) from NaCl stress in young barley (Hordeum vulgare L, var CM 72) seedlings was investigated. Nitrate uptake was inhibited rapidly by NaCl, within 1 minute after exposure to 200 millimolar NaCl. The duration of exposure to saline conditions determined the time of recovery of NO3- uptake from NaCl stress. Recovery was dependent on the presence of NO3- and was inhibited by cycloheximide, 6-methylpurine, and cerulenin, respective inhibitors of protein, RNA, and sterol/fatty acid synthesis. These inhibitors also prevented the induction of the NO3- uptake system in uninduced seedlings. Uninduced seedlings exhibited endogenous NO3- transport activity that appeared to be constitutive. This constitutive activity was also inhibited by NaCl. Recovery of constitutive NO3- uptake did not require the presence of NO3-.

Effect of eight outer continental shelf drilling muds on the calcification rate and free amino acid pool of the coral Acropora cervicornis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, E.N.; Kendall, J.J. Jr.; Connor, S.J.

1984-09-01

During most offshore drilling operations, drilling muds are routinely discharged into surrounding waters. Because corals are relatively sensitive to many environmental perturbations and can be adversely affected by offshore drilling operations, the effects of drilling muds on corals have received considerable attention. Because drilling muds are discharged intermittently, only periodic exposures of short duration should impact nearby coral reefs. To fully assess the impact of a drilling mud discharge on corals requires an assessment of the capacity for corals to recover from short-term exposure. The purpose of this study was to assess the relative toxicity of a number of mudsmore » that were slated for marine disposal for the coral Acropora cervicornis after a 48-hr recovery period. Calcification rate and free amino acid pool were investigated.« less

Oxidation-resistant reflective surfaces for solar dynamic power generation in near Earth orbit

NASA Technical Reports Server (NTRS)

Gulino, D. A.; Mgf2, Sio2, Al2o3, and si3n4, we

1986-01-01

Reflective surfaces for space station power generation systems are required to withstand the atomic oxygen-dominated environment of near Earth orbit. Thin films of platinum and rhodium, which are corrosion resistant reflective metals, have been deposited by ion beam sputter deposition onto various substrate materials. Solar reflectances were then measured as a function of time of exposure to a RF-generated air plasma. Similarly, various protective coating materials, including MgF2, SiO2, Al2O3, and Si3N4, were deposited onto silver-coated substrates and then exposed to the plasma. Analysis of the films both before and after exposure by both ESCA and Auger spectroscopy was also performed. The results indicate that Pt and Rh do not suffer any loss in reflectance over the duration of the tests. Also, each of the coating materials survived the plasma environment. The ESCA and Auger analyses are discussed as well.

Mobile phone radiation alters proliferation of hepatocarcinoma cells.

PubMed

Ozgur, Elcin; Guler, Goknur; Kismali, Gorkem; Seyhan, Nesrin

2014-11-01

This study investigated the effects of intermittent exposure (15 min on, 15 min off for 1, 2, 3, or 4 h, at a specific absorption rate of 2 W/kg) to enhanced data rates for global system for mobile communication evolution-modulated radiofrequency radiation (RFR) at 900- and 1,800-MHz frequencies on the viability of the Hepatocarcinoma cells (Hep G2). Hep G2 cell proliferation was measured by a colorimetric assay based on the cleavage of the tetrazolium salt WST-1 by mitochondrial dehydrogenases in viable cells. Cell injury was evaluated by analyzing the levels of lactate dehydrogenase (LDH) and glucose released from lysed cells into the culture medium. Morphological observation of the nuclei was carried out by 4',6-diamidino-2-phenylindole (DAPI) staining using fluorescence microscopy. In addition, TUNEL assay was performed to confirm apoptotic cell death. It was observed that cell viability, correlated with the LDH and glucose levels, changed according to the frequency and duration of RFR exposure. Four-hour exposure produced more pronounced effects than the other exposure durations. 1,800-MHz RFR had a larger impact on cell viability and Hep G2 injury than the RFR at 900 MHz. Morphological observations also supported the biochemical results indicating that most of the cells showed irregular nuclei pattern determined by using the DAPI staining, as well as TUNEL assay which shows DNA damage especially in the cells after 4 h of exposure to 1,800-MHz RFR. Our results indicate that the applications of 900- and 1,800-MHz (2 W/kg) RFR cause to decrease in the proliferation of the Hep G2 cells after 4 h of exposure. Further studies will be conducted on other frequency bands of RFR and longer duration of exposure.

Randomized controlled trial testing the impact of high-protection sunscreens on sun-exposure behavior.

PubMed

Dupuy, Alain; Dunant, Ariane; Grob, Jean-Jacques

2005-08-01

High-protection sunscreens have been suspected to prompt people to increase sun exposure, and thus to increase skin cancer risk. We tested the influence of both the actual protection (sun protection factor [SPF]) and the information about protection (label) on sun-exposure behavior. Randomized controlled trial. Four French seaside resorts during summer 2001. A total of 367 healthy subjects during their 1-week holiday. Outcome was assessable in 98% of them. Subjects were offered free sunscreens, with randomization into the following study arms: (1) SPF 40 labeled as "high protection"; (2) SPF 40 labeled as "basic protection"; and (3) SPF 12 labeled as "basic protection." Arm 4, ie, SPF 12 labeled as "high protection," was not implemented for ethical reasons. Subjects were not aware of the real target of the study and were blinded to the SPF value. Duration of sunbathing exposure during 1 week. Secondary outcomes were occurrence of sunburns and amount of sunscreen used. Influences of SPF and label were assessed separately. Compared with the low-SPF group, the high-SPF group did not have longer sunbathing exposure (12.9 +/- 7.2 h/wk for high SPF vs 14.6 +/- 6.7 h/wk for low SPF; P = .06), experienced fewer sunburns (14% vs 24%; P = .049), and used less sunscreen (median, 30 g vs 109 g; P<.001). The label "high protection" or "basic protection" had no influence on these end points. In this adult population, higher SPF had no influence on duration of sun exposure and offered better protection against sunburns. Although higher SPF may increase sun exposure duration in specific populations, this effect cannot be viewed as a universal side effect of high-SPF sunscreens.

Estimating Retrospective Exposure of Household Humidifier Disinfectants

PubMed Central

Park, Dong-Uk; Friesen, Melissa C; Roh, Hyun-Suk; Choi, Ye-Yong; Ahn, Jong-Ju; Lim, Heung-Kyu; Kim, Sun-Kyung; Koh, Dong-Hee; Jung, Hye-Jung; Lee, Jong-Hyeon; Cheong, Hae-Kwan; Lim, Sin-Ye; Leem, Jong-Han; Kim, Yong-Hwa; Paek, Do-Myung

2014-01-01

We conducted a comprehensive humidifier disinfectant exposure characterization for 374 subjects with lung disease who presumed their disease was related to humidifier disinfectant use (patient group) and for 303 of their family members (family group) for an ongoing epidemiological study. We visited the homes of the registered patients to investigate disinfectant use characteristics. Probability of exposure to disinfectants was determined from the questionnaire and supporting evidence from photographs demonstrating the use of humidifier disinfectant, disinfectant purchase receipts, any residual disinfectant and the consistency of their statements. Exposure duration was estimated as cumulative disinfectant use hours from the questionnaire. Airborne disinfectant exposure intensity (μg/m3) was estimated based on the disinfectant volume (mL) and frequency added to the humidifier per day, disinfectant bulk level (μg/mL), the volume of the room (m3) with humidifier disinfectant, and the degree of ventilation. Overall, the distribution patterns of the intensity, duration and cumulative exposure to humidifier disinfectants for the patient group were higher than those of the family group, especially for pregnant women and patients ≤ 6 years old. Further study is underway to evaluate the association between the disinfectant exposure estimated here with clinically diagnosed lung disease. PMID:25557769

Towards the methodological optimization of the moss bag technique in terms of contaminants concentrations and replicability values

NASA Astrophysics Data System (ADS)

Ares, A.; Fernández, J. A.; Carballeira, A.; Aboal, J. R.

2014-09-01

The moss bag technique is a simple and economical environmental monitoring tool used to monitor air quality. However, routine use of the method is not possible because the protocols involved have not yet been standardized. Some of the most variable methodological aspects include (i) selection of moss species, (ii) ratio of moss weight to surface area of the bag, (iii) duration of exposure, and (iv) height of exposure. In the present study, the best option for each of these aspects was selected on the basis of the mean concentrations and data replicability of Cd, Cu, Hg, Pb and Zn measured during at least two exposure periods in environments affected by different degrees of contamination. The optimal choices for the studied aspects were the following: (i) Sphagnum denticulatum, (ii) 5.68 mg of moss tissue for each cm-2 of bag surface, (iii) 8 weeks of exposure, and (iv) 4 m height of exposure. Duration of exposure and height of exposure accounted for most of the variability in the data. The aim of this methodological study was to provide data to help establish a standardized protocol that will enable use of the moss bag technique by public authorities.

Interactive vs passive screen time and nighttime sleep duration among school-aged children.

PubMed

Yland, Jennifer; Guan, Stanford; Emanuele, Erin; Hale, Lauren

2015-09-01

Insufficient sleep among school-aged children is a growing concern, as numerous studies have shown that chronic short sleep duration increases the risk of poor academic performance and specific adverse health outcomes. We examined the association between weekday nighttime sleep duration and 3 types of screen exposure: television, computer use, and video gaming. We used age 9 data from an ethnically diverse national birth cohort study, the Fragile Families and Child Wellbeing Study, to assess the association between screen time and sleep duration among 9-year-olds, using screen time data reported by both the child (n = 3269) and by the child's primary caregiver (n= 2770). Within the child-reported models, children who watched more than 2 hours of television per day had shorter sleep duration by approximately 11 minutes per night compared to those who watched less than 2 hours of television (β = -0.18; P < .001). Using the caregiver-reported models, both television and computer use were associated with reduced sleep duration. For both child- and parent-reported screen time measures, we did not find statistically significant differences in effect size across various types of screen time. Screen time from televisions and computers is associated with reduced sleep duration among 9-year-olds, using 2 sources of estimates of screen time exposure (child and parent reports). No specific type or use of screen time resulted in significantly shorter sleep duration than another, suggesting that caution should be advised against excessive use of all screens.

Sound Exposure of Healthcare Professionals Working with a University Marching Band.

PubMed

Russell, Jeffrey A; Yamaguchi, Moegi

2018-01-01

Music-induced hearing disorders are known to result from exposure to excessive levels of music of different genres. Marching band music, with its heavy emphasis on brass and percussion, is one type that is a likely contributor to music-induced hearing disorders, although specific data on sound pressure levels of marching bands have not been widely studied. Furthermore, if marching band music does lead to music-induced hearing disorders, the musicians may not be the only individuals at risk. Support personnel such as directors, equipment managers, and performing arts healthcare providers may also be exposed to potentially damaging sound pressures. Thus, we sought to explore to what degree healthcare providers receive sound dosages above recommended limits during their work with a marching band. The purpose of this study was to determine the sound exposure of healthcare professionals (specifically, athletic trainers [ATs]) who provide on-site care to a large, well-known university marching band. We hypothesized that sound pressure levels to which these individuals were exposed would exceed the National Institute for Occupational Safety and Health (NIOSH) daily percentage allowance. Descriptive observational study. Eight ATs working with a well-known American university marching band volunteered to wear noise dosimeters. During the marching band season, ATs wore an Etymotic ER-200D dosimeter whenever working with the band at outdoor rehearsals, indoor field house rehearsals, and outdoor performances. The dosimeters recorded dose percent exposure, equivalent continuous sound levels in A-weighted decibels, and duration of exposure. For comparison, a dosimeter also was worn by an AT working in the university's performing arts medicine clinic. Participants did not alter their typical duties during any data collection sessions. Sound data were collected with the dosimeters set at the NIOSH standards of 85 dBA threshold and 3 dBA exchange rate; the NIOSH 100% daily dose is an exposure to 85 dBA over 8 h. Dose data for each session were converted to a standardized dose intensity by dividing the dose percentage by the duration of the exposure and setting the NIOSH standard as a factor of 1.0. This allowed convenient relative comparisons of dose percentages of vastly different exposure durations. Analysis of variance examined relationships of noise exposures among the venues; post hoc testing was used to assess pairwise differences. As hypothesized, ATs were exposed to high sound pressure levels and dose percentages greatly exceeding those recommended by NIOSH. Higher sound levels were recorded in performance venues compared with rehearsal venues. In addition to the band music, crowd noise and public address systems contribute to high sound levels at performances. Our results suggest that healthcare providers working with marching bands are exposed to dangerous levels of sound during performances. This is especially true at venues such as football stadiums, where crowd noise and public address systems add to sound pressure. A hearing conservation program, including protection, should be required for all healthcare staff who work with marching bands. Moreover, our results should inform hearing conservation practices for marching musicians, directors, and support personnel. American Academy of Audiology

Development of a 0.1 μm linewidth fabrication process for x-ray lithography with a laser plasma source

NASA Astrophysics Data System (ADS)

Bobkowski, Romuald; Fedosejevs, Robert; Broughton, James N.

1999-06-01

A process has been developed for the purpose of fabricating 0.1 micron linewidth interdigital electrode patterns based on proximity x-ray lithography using a laser-plasma source. Such patterns are required in the manufacture of surface acoustic wave devices. The x-ray lithography was carried out using emission form a Cu plasma produced by a 15Hz, 248nm KrF excimer laser. A temporally multiplexed 50ps duration seed pulse was used to extract the KrF laser energy producing a train of several 50ps pulses spaced approximately 2ns apart within each output pulse. Each short pulse within the train gave the high focal spot intensity required to achieve high efficiency emission of keV x-rays. The first stage of the overall process involves the fabrication of x-ray mask patterns on 1 micron thick Si3N4 membranes using 3-beam lithography followed by gold electroplating. The second stage involves x-ray exposure of a chemically amplified resist through the mask patterns to produce interdigital electrode patterns with 0.1 micron linewidth. Helium background gas and thin polycarbonate/aluminum filters are employed to prevent debris particles from the laser-plasma source form reaching the exposed sample. A computer control system fires the laser and monitors the x-ray flux from the laser-plasma source to insure the desired x-ray exposure is achieved at the resist. In order to reduce diffusion effects in the chemically amplified resist during the post exposure bake the temperature had to be reduced from that normally used. Good reproduction of 0.1 micron linewidth patterns into the x-ray resist was obtained once the exposure parameters and post exposure bake were optimized. A compact exposure station using flowing helium at atmospheric pressure has also been developed for the process, alleviating the need for a vacuum chamber. The details of the overall process and the compact exposure station will be presented.

Adjustable long duration high-intensity point light source

NASA Astrophysics Data System (ADS)

Krehl, P.; Hagelweide, J. B.

1981-06-01

A new long duration high-intensity point light source with adjustable light duration and a small light spot locally stable in time has been developed. The principle involved is a stationary high-temperature plasma flow inside a partly constrained capillary of a coaxial spark gap which is viewed end on through a terminating Plexiglas window. The point light spark gap is operated via a resistor by an artificial transmission line. Using two exchangeable inductance sets in the line, two ranges of photoduration 10-130 μs and 100-600 μs can be covered. For a light spot size of 1.5 mm diameter the corresponding peak light output amounts to 5×106 and 1.6×106 candelas, respectively. Within these ranges the duration is controlled by an ignitron crowbar to extinguish the plasma. The adjustable photoduration is very useful for the application of continuous writing rotating mirror cameras, thus preventing multiple exposures. The essentially uniform exposure within the visible spectral range makes the new light source suitable for color cinematography.

The Upper Midwest Health Study: industry and occupation of glioma cases and controls.

PubMed

Ruder, Avima M; Waters, Martha A; Carreón, Tania; Butler, Mary A; Calvert, Geoffrey M; Davis-King, Karen E; Waters, Kathleen M; Schulte, Paul A; Mandel, Jack S; Morton, Roscoe F; Reding, Douglas J; Rosenman, Kenneth D

2012-09-01

Understanding glioma etiology requires determining which environmental factors are associated with glioma. Upper Midwest Health Study case-control participant work histories collected 1995-1998 were evaluated for occupational associations with glioma. "Exposures of interest" from our study protocol comprise our a priori hypotheses. Year-long or longer jobs for 1,973 participants were assigned Standard Occupational Classifications (SOC) and Standard Industrial Classifications (SIC). The analysis file includes 8,078 SIC- and SOC-coded jobs. For each individual, SAS 9.2 programs collated employment with identical SIC-SOC coding. Distributions of longest "total employment duration" (total years worked in jobs with identical industry and occupation codes, including multiple jobs, and non-consecutive jobs) were compared between cases and controls, using an industrial hygiene algorithm to group occupations. Longest employment duration was calculated for 780 cases and 1,156 controls. More case than control longest total employment duration was in the "engineer, architect" occupational group [16 cases, 10 controls, odds ratio (OR) 2.50, adjusted for age group, sex, age and education, 95% confidence interval (CI) 1.12-5.60]. Employment as a food processing worker [mostly butchers and meat cutters] was of borderline significance (27 cases, 21 controls, adjusted OR: 1.78, CI: 0.99-3.18). Among our exposures of interest work as engineers or as butchers and meat cutters was associated with increased glioma risk. Significant associations could be due to chance, because of multiple comparisons, but similar findings have been reported for other glioma studies. Our results suggest some possible associations but by themselves could not provide conclusive evidence. Copyright © 2012 Wiley Periodicals, Inc.

Space life sciences perspectives for Space Station Freedom

NASA Technical Reports Server (NTRS)

Young, Laurence R.

1992-01-01

It is now generally acknowledged that the life science discipline will be the primary beneficiary of Space Station Freedom. The unique facility will permit advances in understanding the consequences of long duration exposure to weightlessness and evaluation of the effectiveness of countermeasures. It will also provide an unprecedented opportunity for basic gravitational biology, on plants and animals as well as human subjects. The major advantages of SSF are the long duration exposure and the availability of sufficient crew to serve as subjects and operators. In order to fully benefit from the SSF, life sciences will need both sufficient crew time and communication abilities. Unlike many physical science experiments, the life science investigations are largely exploratory, and frequently bring unexpected results and opportunities for study of newly discovered phenomena. They are typically crew-time intensive, and require a high degree of specialized training to be able to react in real time to various unexpected problems or potentially exciting findings. Because of the long duration tours and the large number of experiments, it will be more difficult than with Spacelab to maintain astronaut proficiency on all experiments. This places more of a burden on adequate communication and data links to the ground, and suggests the use of AI expert system technology to assist in astronaut management of the experiment. Typical life science experiments, including those flown on Spacelab Life Sciences 1, will be described from the point of view of the demands on the astronaut. A new expert system, 'PI in a Box,' will be introduced for SLS-2, and its applicability to other SSF experiments discussed. (This paper consists on an abstract and ten viewgraphs.)

Space life sciences perspectives for Space Station Freedom

NASA Astrophysics Data System (ADS)

Young, Laurence R.

It is now generally acknowledged that the life science discipline will be the primary beneficiary of Space Station Freedom. The unique facility will permit advances in understanding the consequences of long duration exposure to weightlessness and evaluation of the effectiveness of countermeasures. It will also provide an unprecedented opportunity for basic gravitational biology, on plants and animals as well as human subjects. The major advantages of SSF are the long duration exposure and the availability of sufficient crew to serve as subjects and operators. In order to fully benefit from the SSF, life sciences will need both sufficient crew time and communication abilities. Unlike many physical science experiments, the life science investigations are largely exploratory, and frequently bring unexpected results and opportunities for study of newly discovered phenomena. They are typically crew-time intensive, and require a high degree of specialized training to be able to react in real time to various unexpected problems or potentially exciting findings. Because of the long duration tours and the large number of experiments, it will be more difficult than with Spacelab to maintain astronaut proficiency on all experiments. This places more of a burden on adequate communication and data links to the ground, and suggests the use of AI expert system technology to assist in astronaut management of the experiment. Typical life science experiments, including those flown on Spacelab Life Sciences 1, will be described from the point of view of the demands on the astronaut. A new expert system, 'PI in a Box,' will be introduced for SLS-2, and its applicability to other SSF experiments discussed. (This paper consists on an abstract and ten viewgraphs.)

Advancing the 3Rs in regulatory toxicology - Carcinogenicity testing: Scope for harmonisation and advancing the 3Rs in regulated sectors of the European Union.

PubMed

Annys, Erwin; Billington, Richard; Clayton, Rick; Bremm, Klaus-Dieter; Graziano, Michael; McKelvie, Jo; Ragan, Ian; Schwarz, Michael; van der Laan, Jan Willem; Wood, Charles; Öberg, Mattias; Wester, Piet; Woodward, Kevin N

2014-07-01

Different government agencies operating in the European Union regulate different types of chemical products but all require testing for carcinogenicity to support applications for product marketing and commercialisation. A conference was held in Brussels in 2013 where representatives of the pharmaceutical, animal health, chemical and plant protection industries, together with representatives of regulatory agencies, universities and other stakeholders, met under the auspices of The European Partnership for Alternative Approaches to Animal Testing (EPAA) to discuss the varying requirements for carcinogenicity testing, and how these studies might be refined to improve hazard evaluation and risk assessment while implementing principles of the 3Rs (replacement, refinement and reduction in animal studies). While there are some similarities, the regulatory approaches in pharmaceutical, animal health, chemical and plant protection sectors have varying degrees of flexibility in requirements for carcinogenicity testing, to an extent reflecting concerns over the magnitude and duration of human exposure, either directly as in therapeutic exposure to pharmaceuticals, or indirectly through the ingestion of residues of veterinary drugs or plant protection chemicals. The article discusses these differences and other considerations for modified carcinogenicity testing paradigms on the basis of scientific and 3Rs approaches. Copyright © 2014 Elsevier Inc. All rights reserved.

Bubble CPAP for respiratory distress syndrome in preterm infants.

PubMed

Koti, Jagdish; Murki, Srinivas; Gaddam, Pramod; Reddy, Anupama; Reddy, M Dasaradha Rami

2010-02-01

To ascertain the immediate outcome of preterm infants with respiratory distress syndrome (RDS) on Bubble CPAP and identify risk factors associated with its failure. Prospective analytical study. Inborn preterm infants (gestation 28 to 34 weeks) admitted to the NICU with respiratory distress and chest X ray suggestive of RDS. Bubble CPAP with bi-nasal prongs. CPAP failures infants requiring ventilation in the first one week. 56 neonates were enrolled in the study. 14 (25%) babies failed CPAP. The predictors of failure were; no or only partial exposure to antenatal steroids, white-out on the chest X-ray, patent ductus arteriosus, sepsis/pneumonia and Downes score > 7 or FiO2 > or = 50% after 15-20 minutes of CPAP. Other maternal and neonatal variables did not influence the need for ventilation. Rates of mortality and duration of oxygen requirement was significantly higher in babies who failed CPAP. Only two infants developed pneumothorax. No baby had chronic lung disease. Infants with no or partial exposure to antenatal steroids, white-out chest X-ray, patent ductus arteriosus, sepsis/pneumonia and those with higher FiO2 requirement after initial stabilization on CPAP are at high risk of CPAP failure (needing mechanical ventilation). Bubble CPAP is safe for preterm infants with RDS.

Duration and timing of daily light exposure influence the rapid shifting of BALB/cJ mouse circadian locomotor rhythms.

PubMed

Vajtay, Thomas J; St Thomas, Jeremy J; Takacs, Tyrus E; McGann, Eric G; Weber, E Todd

2017-10-01

Photic entrainment of the murine circadian system can typically be explained with a discrete model in which light exposures near dusk and dawn can either advance or delay free-running rhythms to match the external light cycle period. In most mouse strains, the magnitude of those phase shifts is limited to several hours per day; however, the BALB/cJ mouse can re-entrain to large (6-8hour) phase advances of the light/dark cycle. In this study, we demonstrate that the circadian responses of BALB/cJ mice are dependent on duration as well as timing of light exposure, with significantly larger phase shifts resulting from >6-hour light exposures, yet loss of entrainment to photoperiods of <2-3hours per day or to skeleton photoperiods. Intermittent light exposures of the same total duration but distributed differentially over the same period of time as that of a 6-hour phase advance of the light cycle yielded phase shifts of different magnitudes depending on the pattern of exposure. Both negative and positive masking responses to light and darkness, respectively, were exaggerated in BALB/cJ mice under a T7 light cycle, but were not responsible for their rapid re-entrainment to chronic phase shifting of the light dark cycle. These results collectively suggest that the innately jetlag-resistant BALB/cJ mouse circadian system provides an alternative murine model in which to elucidate the limitations of photic entrainment observed in other commonly used strains of mice. Copyright © 2017 Elsevier Inc. All rights reserved.

Combined endosulfan and cypermethrin-induced toxicity to embryo-larval development of Rhinella arenarum.

PubMed

Svartz, Gabriela V; Aronzon, Carolina M; Pérez Coll, Cristina S

2016-01-01

The combined effects of two widely used pesticides, endosulfan and cypermethrin, on survival of embryo-larval development of the South American toad (Rhinella arenarum) were examined. The toxicity bioassays were performed according to the AMPHITOX test. Embryos and larvae were exposed to mixtures of these pesticides at equitoxic ratios from acute or chronic exposure to evaluate interaction effects. The results were analyzed using both Marking's additive index and combination index (CI)-isobologram methods. Acute (96-h) and intermediate (168-h) toxicity of endosulfan-cypermethrin mixtures remained almost constant for larvae and embryos, but when exposure duration was increased, there was a significant elevation in toxicity, obtaining chronic (240-h) no-observed-effect concentrations (NOEC) values of 0.045 and 0.16 mg/L for embryos and larvae, respectively. These are environmentally relevant concentrations that reflect a realistic risk of this pesticide mixture to this native amphibian species. The toxicity increment with the exposure duration was coincident with the central nervous system development on embryos reaching the larval period, the main target organ of these pesticides. The interactions of the pesticide mixtures at acute and chronic exposure were antagonistic for embryo development (CI > 1), and additive (CI = 1) for larvae, while chronic exposure interactions were synergistic (CI < 1) for both developmental periods. Data indicated that endosulfan-cypermethrin mixtures resulted in different interaction types depending on duration and developmental stage exposed. As a general pattern and considering conditions of overall developmental period and chronic exposure, this pesticide mixture usually applied in Argentine crop fields is synergistic with respect to toxicity for this native amphibian species.

Novel Exercise Hardware Requirements, Development, and Selection Process for Long-Duration Space Flight

NASA Technical Reports Server (NTRS)

Weaver, Aaron S.; Funk, Justin H.; Funk, Nathan W.; Dewitt, John K.; Fincke, Renita S.; Newby, Nathaniel; Caldwell, Erin; Sheehan, Christopher C.; Moore, E. Cherice; Ploutz-Snyder, Lori;

Impact of Early Versus Late Diuretic Exposure on Metabolic Bone Disease and Growth in Premature Neonates.

PubMed

Orth, Lucas E; O'Mara, Keliana L

2018-01-01

This study aimed to determine whether there are differences in the incidence of metabolic bone disease (MBD) between preterm neonates first exposed to diuretics prior to 2 weeks of life versus those exposed after 2 weeks. This study was a retrospective analysis of premature neonates born at a tertiary care center between 2011 and 2015 who received either furosemide or chlorothiazide. The primary outcome was incidence of MBD. Secondary outcomes included growth, electrolyte disturbances, oxygen requirement, and length of stay. A total of 147 patients were included. Early initiation (n = 90) and late initiation (n = 57) arms were balanced with respect to birth weight and gestational age. There was no difference in incidence of MBD in the early group (76%) versus the late group (65%; p = 0.164). Stratification by cumulative dose showed incidence of 85% in patients receiving ≥8 mg/kg of furosemide, compared with 68% and 64% of those in the <4 mg/kg and 4 to 7.9 mg/kg strata, respectively (p = 0.06). The early group experienced greater reductions in length-for-age growth during diuretic therapy (-70% versus -40%; p = 0.009). Electrolyte abnormalities were more prevalent in the early group. Although there was no difference in duration of mechanical ventilation, duration of supplemental oxygen requirement was reduced in the late group (75 versus 89 days; p = 0.003). Timing of diuretic initiation did not affect incidence of MBD. Increased cumulative furosemide exposure may be associated with higher incidence. Patients first exposed to diuretics within 2 weeks of life are at higher risk for electrolyte abnormalities and reduced growth velocity.

Human Health and Performance Considerations for Exploration of Near-Earth Asteroids

NASA Technical Reports Server (NTRS)

Kundrot, Craig; Steinberg, Susan; Charles, John

2010-01-01

This presentation will describe the human health and performance issues that are anticipated for the human exploration of near-Earth asteroids (NEA). Humans are considered a system in the design of any such deep-space exploration mission, and exploration of NEA presents unique challenges for the human system. Key factors that define the mission are those that are strongly affected by distance and duration. The most critical of these is deep-space radiation exposure without even the temporary shielding of a nearby large planetary body. The current space radiation permissible exposure limits (PEL) restrict mission duration to 3-10 months depending on age and gender of crewmembers and stage of the solar cycle. Factors that affect mission architecture include medical capability; countermeasures for bone, muscle, and cardiovascular atrophy during continuous weightlessness; restricted food supplies; and limited habitable volume. The design of a habitat that can maintain the physical and psychological health of the crew and support mission operations with limited intervention from Earth will require an integrated research and development effort by NASA s Human Research Program, engineering, and human factors groups. Limited abort and return options for an NEA mission are anticipated to have important effects on crew psychology as well as influence medical supplies and training requirements of the crew. Other important factors are those related to isolation, confinement, communication delays, autonomous operations, task design, small crew size, and even the unchanging view outside the windows for most of the mission. Geological properties of the NEA will influence design of sample handling and containment, and extravehicular activity capabilities including suit ports and tools. A robotic precursor mission that collects basic information on NEA surface properties would reduce uncertainty about these aspects of the mission as well as aid in design of mission architecture and exploration tasks.

Lung cancer among newspaper printers exposed to ink mist: a study of trade union members in Manchester, England.

PubMed Central

Leon, D A; Thomas, P; Hutchings, S

1994-01-01

A nested case-control study of lung cancer among men exposed to ink mist in newspaper production with rotary letterpress technology is presented. It is based within a historical cohort of 9232 printing workers in Manchester (1949-63). Men who operated newspaper rotary letterpress machines had a lung cancer standardised mortality ratio (SMR) of 179 (95% confidence interval (95% CI) 144-218) when compared with rates for England and Wales for the follow up period 1950-83. When adjustment was made for the higher rates in the local area, the SMR was reduced to 122 (95% CI 98-148). The nested case control study was based on 110 lung cancer cases (1949-86) and 316 matched controls. Duration of work in a rotary letterpress machine room was positively associated with risk of lung cancer (chi 2 linear trend = 3.30, p = 0.07); mean with 30 or more years duration of exposure had a risk of 1.73 (95% CI 0.94-3.17), relative to those with less than 20 years of exposure. Adjustment for period of first exposure in a machine room reduced the strength of the positive duration effect. The magnitude of the SMRs found in the cohort study could be explained by confounding with smoking. The duration effect seen in the case-control study, however, suggests that there may be a real effect of exposure to letterpress ink mists. This is biologically plausible, as benzo[a]pyrene, a known human carcinogen, has been found in appreciable concentrations in the atmosphere of rotary letterpress machine rooms. PMID:8111469

The dynamics of categorization: Unraveling rapid categorization.

PubMed

Mack, Michael L; Palmeri, Thomas J

2015-06-01

We explore a puzzle of visual object categorization: Under normal viewing conditions, you spot something as a dog fastest, but at a glance, you spot it faster as an animal. During speeded category verification, a classic basic-level advantage is commonly observed (Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976), with categorization as a dog faster than as an animal (superordinate) or Golden Retriever (subordinate). A different story emerges during ultra-rapid categorization with limited exposure duration (<30 ms), with superordinate categorization faster than basic or subordinate categorization (Thorpe, Fize, & Marlot, 1996). These two widely cited findings paint contrary theoretical pictures about the time course of categorization, yet no previous study has investigated them together. We systematically examined two experimental factors that could explain the qualitative difference in categorization across the two paradigms: exposure duration and category trial context. Mapping out the time course of object categorization by manipulating exposure duration and the timing of a post-stimulus mask revealed that brief exposure durations favor superordinate-level categorization, but with more time a basic-level advantage emerges. However, these advantages were modulated by category trial context. With randomized target categories, the superordinate advantage was eliminated; and with only four repetitions of superordinate categorization within an otherwise randomized context, the basic-level advantage was eliminated. Contrary to theoretical accounts that dictate a fixed priority for certain levels of abstraction in visual processing and access to semantic knowledge, the dynamics of object categorization are flexible, depending jointly on the level of abstraction, time for perceptual encoding, and category context. (c) 2015 APA, all rights reserved).

THE DYNAMICS OF CATEGORIZATION: UNRAVELING RAPID CATEGORIZATION

PubMed Central

Mack, Michael L.; Palmeri, Thomas J.

2015-01-01

We explore a puzzle of visual object categorization: Under normal viewing conditions, you spot something as a dog fastest, but at a glance, you spot it faster as an animal. During speeded category verification, a classic basic-level advantage is commonly observed (Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976), with categorization as a dog faster than as an animal (superordinate) or Golden Retriever (subordinate). A different story emerges during ultra-rapid categorization with limited exposure duration (<30ms), with superordinate categorization faster than basic or subordinate categorization (Thorpe, Fize, & Marlot, 1996). These two widely cited findings paint contrary theoretical pictures about the time course of object categorization, yet no study has previously investigated them together. Over five experiments, we systematically examined two experimental factors that could explain the qualitative difference in categorization across the two paradigms: exposure duration and category trial context. Mapping out the time course of object categorization by manipulating exposure duration and the timing of a post-stimulus mask revealed that brief exposure durations favor superordinate-level categorization, but with more time a basic-level advantage emerges. But this superordinate advantage was modulated significantly by target category trial context. With randomized target categories, the superordinate advantage was eliminated; and with “blocks” of only four repetitions of superordinate categorization within an otherwise randomized context, the advantage for the basic-level was eliminated. Contrary to some theoretical accounts that dictate a fixed priority for certain levels of abstraction in visual processing and access to semantic knowledge, the dynamics of object categorization are flexible, depending jointly on the level of abstraction, time for perceptual encoding, and category context. PMID:25938178

Socioeconomic status, occupational characteristics, and sleep duration in African/Caribbean immigrants and US White health care workers.

PubMed

Ertel, Karen A; Berkman, Lisa F; Buxton, Orfeu M

2011-04-01

o advance our understanding of the interplay of socioeconomic factors, occupational exposures, and race/ethnicity as they relate to sleep duration. We hypothesize that non Hispanic African/Caribbean immigrant employees in long term health care have shorter sleep duration than non Hispanic white employees, and that low education, low income, and occupational exposures including night work and job strain account for some of the African/Caribbean immigrant-white difference in sleep duration. Cross sectional Four extended care facilities in Massachusetts, United States 340 employees in extended care facilities Sleep duration was assessed with wrist actigraphy for a mean of 6.3 days. In multivariable regression modeling controlling for gender and age, African/Caribbean immigrants slept 64.4 fewer minutes (95% CI: -81.0, -47.9) per night than white participants; additional control for education and income reduced the racial gap to 50.9 minutes (-69.2, -32.5); additional control for the occupational factors of hours worked per week and working the night shift reduced the racial gap to 37.7 minutes (-57.8, -17.6). his study provides support for the hypothesis that socioeconomic and occupational characteristics explain some of the African/ Caribbean immigrant-white difference in sleep duration in the United States, especially among health care workers.

Rescaling of temporal expectations during extinction

PubMed Central

Drew, Michael R.; Walsh, Carolyn; Balsam, Peter D

2016-01-01

Previous research suggests that extinction learning is temporally specific. Changing the CS duration between training and extinction can facilitate the loss of the CR within the extinction session but impairs long-term retention of extinction. In two experiments using conditioned magazine approach with rats, we examined the relation between temporal specificity of extinction and CR timing. In Experiment 1 rats were trained on a 12-s, fixed CS-US interval and then extinguished with CS presentations that were 6, 12, or 24 s in duration. The design of Experiment 2 was the same except rats were trained using partial rather than continuous reinforcement. In both experiments, extending the CS duration in extinction facilitated the diminution of CRs during the extinction session, but shortening the CS duration failed to slow extinction. In addition, extending (but not shortening) the CS duration caused temporal rescaling of the CR, in that the peak CR rate migrated later into the trial over the course of extinction training. This migration partially accounted for the faster loss of the CR when the CS duration was extended. Results are incompatible with the hypothesis that extinction is driven by cumulative CS exposure and suggest that temporally extended nonreinforced CS exposure reduces conditioned responding via temporal displacement rather than through extinction per se. PMID:28045291

Historical estimation of diesel exhaust exposure in a cohort study of U.S. railroad workers and lung cancer.

PubMed

Laden, Francine; Hart, Jaime E; Eschenroeder, Alan; Smith, Thomas J; Garshick, Eric

2006-09-01

We have previously shown an elevated risk of lung cancer mortality in diesel exhaust exposed railroad workers. To reduce exposure misclassification, we obtained extensive historical information on diesel locomotives used by each railroad. Starting in 1945, we calculated the rate each railroad converted from steam to diesel, creating annual railroad-specific weighting factors for the probability of diesel exposure. We also estimated the average annual exposure intensity based on emission factors. The U.S. Railroad Retirement Board provided railroad assignment and work histories for 52,812 workers hired between 1939-1949, for whom we ascertained mortality from 1959-1996. Among workers hired after 1945, as diesel locomotives were introduced, the relative risk of lung cancer for any exposure was 1.77 (95% CI = 1.50-2.09), and there was evidence of an exposure-response relationship with exposure duration. Exposed workers hired before 1945 had a relative risk of 1.30 (95% CI = 1.19-1.43) for any exposure and there was no evidence of a dose response with duration. There was no evidence of increasing risk using estimated measures of intensity although the overall lung cancer risk remained elevated. In conclusion, although precise historical estimates of exposure are not available, weighting factors helped better define the exposure-response relationship of diesel exhaust with lung cancer mortality.

Asbestotic radiological abnormalities among United States merchant marine seamen.

PubMed

Selikoff, I J; Lilis, R; Levin, G

1990-05-01

There has been limited information concerning the prevalence of radiologically evident parenchymal and pleural fibrosis consistent with prior exposure to asbestos among merchant marine seamen, despite the wide use of asbestos in ship construction until the late 1970s and subsequent exposure of seamen to the asbestos that had been installed. A total of 3324 chest radiographs (1985-7) of long term United States seamen were reviewed. One third (34.8%) had parenchymal or pleural abnormalities, or both (ILO classification); pleural changes were predominant. Abnormalities increased with longer duration from onset of shipboard exposure (as defined by first year at sea). The prevalence of asbestotic changes was greater among seamen who had served in the engine department (391/420; 42.5%) compared with seamen in other departments, including deck (301/820; 36.6%), steward (278/981; 28.4%), or with service in multiple departments (167/541; 30.9%). Since many vessels, particularly those built before 1978, contain asbestos materials, appropriate engineering controls (including complete removal, if possible) are required as well as appropriate medical surveillance for those who served aboard such ships.

Asbestotic radiological abnormalities among United States merchant marine seamen.

PubMed Central

Selikoff, I J; Lilis, R; Levin, G

1990-01-01

There has been limited information concerning the prevalence of radiologically evident parenchymal and pleural fibrosis consistent with prior exposure to asbestos among merchant marine seamen, despite the wide use of asbestos in ship construction until the late 1970s and subsequent exposure of seamen to the asbestos that had been installed. A total of 3324 chest radiographs (1985-7) of long term United States seamen were reviewed. One third (34.8%) had parenchymal or pleural abnormalities, or both (ILO classification); pleural changes were predominant. Abnormalities increased with longer duration from onset of shipboard exposure (as defined by first year at sea). The prevalence of asbestotic changes was greater among seamen who had served in the engine department (391/420; 42.5%) compared with seamen in other departments, including deck (301/820; 36.6%), steward (278/981; 28.4%), or with service in multiple departments (167/541; 30.9%). Since many vessels, particularly those built before 1978, contain asbestos materials, appropriate engineering controls (including complete removal, if possible) are required as well as appropriate medical surveillance for those who served aboard such ships. PMID:2357448

Persistent erectile dysfunction in men exposed to the 5α-reductase inhibitors, finasteride, or dutasteride

PubMed Central

Yarnold, Paul R.; Cashy, John; Brannigan, Robert E.; Nardone, Beatrice; Micali, Giuseppe; West, Dennis Paul

2017-01-01

Importance Case reports describe persistent erectile dysfunction (PED) associated with exposure to 5α-reductase inhibitors (5α-RIs). Clinical trial reports and the manufacturers’ full prescribing information (FPI) for finasteride and dutasteride state that risk of sexual adverse effects is not increased by longer duration of 5α-RI exposure and that sexual adverse effects of 5α-RIs resolve in men who discontinue exposure. Objective Our chief objective was to assess whether longer duration of 5α-RI exposure increases risk of PED, independent of age and other known risk factors. Men with shorter 5α-RI exposure served as a comparison control group for those with longer exposure. Design We used a single-group study design and classification tree analysis (CTA) to model PED (lasting ≥90 days after stopping 5α-RI). Covariates included subject attributes, diseases, and drug exposures associated with sexual dysfunction. Setting Our data source was the electronic medical record data repository for Northwestern Medicine. Subjects The analysis cohorts comprised all men exposed to finasteride or dutasteride or combination products containing one of these drugs, and the subgroup of men 16–42 years old and exposed to finasteride ≤1.25 mg/day. Main outcome and measures Our main outcome measure was diagnosis of PED beginning after first 5α-RI exposure, continuing for at least 90 days after stopping 5α-RI, and with contemporaneous treatment with a phosphodiesterase-5 inhibitor (PDE5I). Other outcome measures were erectile dysfunction (ED) and low libido. PED was determined by manual review of medical narratives for all subjects with ED. Risk of an adverse effect was expressed as number needed to harm (NNH). Results Among men with 5α-RI exposure, 167 of 11,909 (1.4%) developed PED (persistence median 1,348 days after stopping 5α-RI, interquartile range (IQR) 631.5–2320.5 days); the multivariable model predicting PED had four variables: prostate disease, duration of 5α-RI exposure, age, and nonsteroidal anti-inflammatory drug (NSAID) use. Of 530 men with new ED, 167 (31.5%) had new PED. Men without prostate disease who combined NSAID use with >208.5 days of 5α-RI exposure had 4.8-fold higher risk of PED than men with shorter exposure (NNH 59.8, all p < 0.002). Among men 16–42 years old and exposed to finasteride ≤1.25 mg/day, 34 of 4,284 (0.8%) developed PED (persistence median 1,534 days, IQR 651–2,351 days); the multivariable model predicting PED had one variable: duration of 5α-RI exposure. Of 103 young men with new ED, 34 (33%) had new PED. Young men with >205 days of finasteride exposure had 4.9-fold higher risk of PED (NNH 108.2, p < 0.004) than men with shorter exposure. Conclusion and relevance Risk of PED was higher in men with longer exposure to 5α-RIs. Among young men, longer exposure to finasteride posed a greater risk of PED than all other assessed risk factors. PMID:28289563

Influence of salinity and prey presence on the survival of aquatic macroinvertebrates of a freshwater marsh

USGS Publications Warehouse

Kang, Sung-Ryong; King, Sammy L.

2012-01-01

Salinization of coastal freshwater environments is a global issue. Increased salinity from sea level rise, storm surges, or other mechanisms is common in coastal freshwater marshes of Louisiana, USA. The effects of salinity increases on aquatic macroinvertebrates in these systems have received little attention, despite the importance of aquatic macroinvertebrates for nutrient cycling, biodiversity, and as a food source for vertebrate species. We used microcosm experiments to evaluate the effects of salinity, duration of exposure, and prey availability on the relative survival of dominant aquatic macroinvertebrates (i.e., Procambarus clarkii Girard, Cambarellus puer Hobbs, Libellulidae, Dytiscidae cybister) in a freshwater marsh of southwestern Louisiana. We hypothesized that increased salinity, absence of prey, and increased duration of exposure would decrease survival of aquatic macroinvertebrates and that crustaceans would have higher survival than aquatic insect taxon. Our first hypothesis was only partially supported as only salinity increases combined with prolonged exposure duration affected aquatic macroinvertebrate survival. Furthermore, crustaceans had higher survival than aquatic insects. Salinity stress may cause mortality when acting together with other stressful conditions.

Street-level noise in an urban setting: assessment and contribution to personal exposure.

PubMed

McAlexander, Tara P; Gershon, Robyn R M; Neitzel, Richard L

2015-02-28

The urban soundscape, which represents the totality of noise in the urban setting, is formed from a wide range of sources. One of the most ubiquitous and least studied of these is street-level (i.e., sidewalk) noise. Mainly associated with vehicular traffic, street level noise is hard to ignore and hard to escape. It is also potentially dangerous, as excessive noise from any source is an important risk factor for adverse health effects. This study was conducted to better characterize the urban soundscape and the role of street level noise on overall personal noise exposure in an urban setting. Street-level noise measures were obtained at 99 street sites located throughout New York City (NYC), along with data on time, location, and sources of environmental noise. The relationship between street-level noise measures and potential predictors of noise was analyzed using linear and logistic regression models, and geospatial modeling was used to evaluate spatial trends in noise. Daily durations of street-level activities (time spent standing, sitting, walking and running on streets) were estimated via survey from a sample of NYC community members recruited at NYC street fairs. Street-level noise measurements were then combined with daily exposure durations for each member of the sample to estimate exposure to street noise, as well as exposure to other sources of noise. The mean street noise level was 73.4 dBA, with substantial spatial variation (range 55.8-95.0 dBA). Density of vehicular (road) traffic was significantly associated with excessive street level noise levels. Exposure duration data for street-level noise and other common sources of noise were collected from 1894 NYC community members. Based on individual street-level exposure estimates, and in consideration of all other sources of noise exposure in an urban population, we estimated that street noise exposure contributes approximately 4% to an average individual's annual noise dose. Street-level noise exposure is a potentially important source of overall noise exposure, and the reduction of environmental sources of excessive street- level noise should be a priority for public health and urban planning.

Association of Parkinson's Disease and Its Subtypes with Agricultural Pesticide Exposures in Men: A Case-Control Study in France.

PubMed

Moisan, Frédéric; Spinosi, Johan; Delabre, Laurène; Gourlet, Véronique; Mazurie, Jean-Louis; Bénatru, Isabelle; Goldberg, Marcel; Weisskopf, Marc G; Imbernon, Ellen; Tzourio, Christophe; Elbaz, Alexis

2015-11-01

Pesticides have been associated with Parkinson's disease (PD), but there are few data on important exposure characteristics such as dose-effect relations. It is unknown whether associations depend on clinical PD subtypes. We examined quantitative aspects of occupational pesticide exposure associated with PD and investigated whether associations were similar across PD subtypes. As part of a French population-based case-control study including men enrolled in the health insurance plan for farmers and agricultural workers, cases with clinically confirmed PD were identified through antiparkinsonian drug claims. Two controls were matched to each case. Using a comprehensive occupational questionnaire, we computed indicators for different dimensions of exposure (duration, cumulative exposure, intensity). We used conditional logistic regression to compute odds ratios (ORs) and 95% confidence intervals (CIs) among exposed male farmers (133 cases, 298 controls). We examined the relation between pesticides and PD subtypes (tremor dominant/non-tremor dominant) using polytomous logistic regression. There appeared to be a stronger association with intensity than duration of pesticide exposure based on separate models, as well as a synergistic interaction between duration and intensity (p-interaction = 0.04). High-intensity exposure to insecticides was positively associated with PD among those with low-intensity exposure to fungicides and vice versa, suggesting independent effects. Pesticide exposure in farms that specialized in vineyards was associated with PD (OR = 2.56; 95% CI: 1.31, 4.98). The association with intensity of pesticide use was stronger, although not significantly (p-heterogeneity = 0.60), for tremor-dominant (p-trend < 0.01) than for non-tremor-dominant PD (p-trend = 0.24). This study helps to better characterize different aspects of pesticide exposure associated with PD, and shows a significant association of pesticides with tremor-dominant PD in men, the most typical PD presentation. Moisan F, Spinosi J, Delabre L, Gourlet V, Mazurie JL, Bénatru I, Goldberg M, Weisskopf MG, Imbernon E, Tzourio C, Elbaz A. 2015. Association of Parkinson's disease and its subtypes with agricultural pesticide exposures in men: a case-control study in France. Environ Health Perspect 123:1123-1129; http://dx.doi.org/10.1289/ehp.1307970.

Airborne manganese as dust vs. fume determining blood levels in workers at a manganese alloy production plant

PubMed Central

Park, Robert M.; Baldwin, Mary; Bouchard, Maryse F.; Mergler, Donna

2015-01-01

The appropriate exposure metrics for characterizing manganese (Mn) exposure associated with neurobehavioral effects have not been established. Blood levels of Mn (B-Mn) provide a potentially important intermediate marker of Mn airborne exposures. Using data from a study of a population of silicon- and ferro-manganese alloy production workers employed between 1973 and 1991, B-Mn levels were modeled in relation to prior Mn exposure using detailed work histories and estimated respirable Mn concentrations from air-sampling records. Despite wide variation in exposure levels estimated for individual jobs, duration of employment (exposure) was itself a strong predictor of B-Mn levels and strongest when an 80-day half-life was applied to contributions over time (t = 6.95, 7.44, respectively; p < 10 −5). Partitioning exposure concentrations based on process origin into two categories: (1) “large” respirable particulate (Mn-LRP) derived mainly from mechanically generated dust, and (2) “small” respirable particulate (Mn-SRP) primarily electric furnace condensation fume, revealed that B-Mn levels largely track the small, fume exposures. With a half-life of 65 days applied in a model with cumulative exposure terms for both Mn-LRP (t = −0.16, p = 0.87) and Mn-SRP (t = 6.45, p < 10 −5), the contribution of the large-size fraction contribution was negligible. Constructing metrics based on the square root of SRP exposure concentrations produced a better model fit (t = 7.87 vs. 7.44, R2 = 0.2333 vs. 0.2157). In a model containing both duration (t = 0.79, p = 0.43) and (square root) fume (t = 2.47, p = 0.01) metrics, the duration term was a weak contributor. Furnace-derived, small respirable Mn particulate appears to be the primary contributor to B-Mn levels, with a dose-rate dependence in a population chronically exposed to Mn, with air-concentrations declining in recent years. These observations may reflect the presence of homeostatic control of Mn levels in the blood and other body tissues and be useful in assessing Mn exposures for evaluating neurotoxic effects. PMID:24726792

Rapidly Fatal Silicosis Among Jewellery Workers Attending a District Medical College of West Bengal, India.

PubMed

Panchadhyayee, Prabodh; Saha, Kaushik; Saha, Indranil; Ta, Rupam Kumar; Ghosh, Santanu; Saha, Arnab; Barma, Pratik; Mitra, Mrinmoy

2015-01-01

Silicosis is a slowly progressive chronic occupational lung disease, developed after a prolong period of exposure to high concentration of silica dust. In this longitudinal study, we enrolled old and new silicosis patients (n=19; 8 jewellery polishers, 11 from other occupations) seen at our Pulmonary Medicine Department from June 2009 to December 2012 to document the course of illness as per their occupational exposure. Six of the eight jewellery polishing workers had developed silicosis within five years of exposure, while six of the 11 other workers with other occupational exposure had developed silicosis after exposure of 10 years or more. Mean duration of exposure was significantly less among jewellery polishing workers compared to other workers (3.4 +/- 1.7 versus 9.3 +/- 4.1; p=0.001). Mean duration of illness (months) (14.9 +/- 5.8 versus 28.5 +/- 16.5; p=0.040) were significantly less among the jewellery polishing workers compared to other workers. At the end of the study period, all eight jewellery polishing workers with silicosis had died while four of the 11 patients with other occupational exposure had died. Silicosis among jewellery polishing workers was found to be more severe and progressive compared to silicosis due to other occupational exposures, in our study.

Regionally Applied Research Efforts (RARE) Report titled "The Penobscot River and Environmental Contaminants: Assessment of Tribal Exposure Through Sustenance Lifeways

EPA Science Inventory

The traditional methodology for health risk assessment used by the U. S. Environmental Protection Agency (EPA) is based on the use of exposure assumptions (e.g. exposure duration, food ingestion rate, body weight, etc.) that represent the entire American population, either as a c...

Effect of early tracheostomy on resource utilization and clinical outcomes in critically ill patients: meta-analysis of randomized controlled trials.

PubMed

Szakmany, T; Russell, P; Wilkes, A R; Hall, J E

2015-03-01

Early tracheostomy may decrease the duration of mechanical ventilation, sedation exposure, and intensive care stay, possibly resulting in improved clinical outcomes, but the evidence is conflicting. Systematic review and meta-analysis of randomized trials in patients allocated to tracheostomy within 10 days of start of mechanical ventilation was compared with placement of tracheostomy after 10 days if still required. Medline, EMBASE, the Cochrane Controlled Clinical Trials Register, and Google Scholar were searched for eligible trials. The co-primary outcomes were mortality within 60 days, and duration of mechanical ventilation, sedation, and intensive care unit stay. Secondary outcomes were the number of tracheostomy procedures performed, and incidence of ventilator-associated pneumonia (VAP). Outcomes are described as relative risk or weighted mean difference with 95% confidence intervals. Of note, 4482 publications were identified and 14 trials enrolling 2406 patients were included. Tracheostomy within 10 days was not associated with any difference in mortality [risk ratio (RR): 0.93 (0.83-1.05)]. There were no differences in duration of mechanical ventilation [-0.19 days (-1.13-0.75)], intensive care stay [-0.83 days (-2.05-0.40)], or incidence of VAP. However, duration of sedation was reduced in the early tracheostomy groups [-2.78 days (-3.68 to -1.88)]. More tracheostomies were performed in patients randomly assigned to receive early tracheostomy [RR: 2.53 (1.18-5.40)]. We found no evidence that early (within 10 days) tracheostomy reduced mortality, duration of mechanical ventilation, intensive care stay, or VAP. Early tracheostomy leads to more procedures and a shorter duration of sedation. © The Author 2014. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Passive exposures of children to volatile trihalomethanes during domestic cleaning activities of their parents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andra, Syam S.; Harvard-Cyprus Program, Department of Environmental Health, Harvard School of Public Health, Boston, MA; Charisiadis, Pantelis

Domestic cleaning has been proposed as a determinant of trihalomethanes (THMs) exposure in adult females. We hypothesized that parental housekeeping activities could influence children's passive exposures to THMs from their mere physical presence during domestic cleaning. In a recent cross-sectional study (n=382) in Cyprus [41 children (<18y) and 341 adults (≥18y)], we identified 29 children who met the study's inclusion criteria. Linear regression models were applied to understand the association between children sociodemographic variables, their individual practices influencing ingestion and noningestion exposures to ΣTHMs, and their urinary THMs levels. Among the children-specific variables, age alone showed a statistically significant inversemore » association with their creatinine-adjusted urinary ΣTHMs (r{sub S}=−0.59, p<0.001). A positive correlation was observed between urinary ΣTHMs (ng g{sup −1}) of children and matched-mothers (r{sub S}=0.52, p=0.014), but this was not the case for their matched-fathers (r{sub S}=0.39, p=0.112). Time spent daily by the matched-mothers for domestic mopping, toilet and other cleaning activities using chlorine-based cleaning products was associated with their children's urinary THMs levels (r{sub S}=0.56, p=0.007). This trend was not observed between children and their matched-fathers urinary ΣTHMs levels, because of minimum amount of time spent by the latter in performing domestic cleaning. The proportion of variance of creatinine-unadjusted and adjusted urinary ΣTHMs levels in children that was explained by the matched-mothers covariates was 76% and 74% (p<0.001), respectively. A physiologically-based pharmacokinetic model adequately predicted urinary chloroform excretion estimates, being consistent with the corresponding measured levels. Our findings highlighted the influence of mothers' domestic cleaning activities towards enhancing passive THMs exposures of their children. The duration of such activities could be further tested as a valid indicator of children's THMs body burden. - Highlights: • First report on THMs exposure assessment in matched parents and children. • Duration of domestic cleaning by mothers influenced passive exposure to THMs in children. • Matched-fathers did little cleaning and thereby no contribution to passive exposure to THMs in children. • Reverse dosimetry showed a good agreement between predicted and observed urinary chloroform. • Passive exposures to THMs require new attention in survey questionnaires and epidemiology.« less

A retrospective cohort study of shift work and risk of cancer-specific mortality in German male chemical workers.

PubMed

Yong, Mei; Nasterlack, Michael; Messerer, Peter; Oberlinner, Christoph; Lang, Stefan

2014-02-01

Human evidence of carcinogenicity concerning shift work is inconsistent. In a previous study, we observed no elevated risk of total mortality in shift workers followed up until the end of 2006. The present study aimed to investigate cancer-specific mortality, relative to shift work. The cohort consisted of male production workers (14,038 shift work and 17,105 day work), employed at BASF Ludwigshafen for at least 1 year between 1995 and 2005. Vital status was followed from 2000 to 2009. Cause-specific mortality was obtained from death certificates. Exposure to shift work was measured both as a dichotomous and continuous variable. While lifetime job history was not available, job duration in the company was derived from personal data, which was then categorized at the quartiles. Cox proportional hazard model was used to adjust for potential confounders, in which job duration was treated as a time-dependent covariate. Between 2000 and 2009, there were 513 and 549 deaths among rotating shift and day work employees, respectively. Risks of total and cancer-specific mortalities were marginally lower among shift workers when taking age at entry and job level into consideration and were statistically significantly lower when cigarette smoking, alcohol intake, job duration, and chronic disease prevalence at entry to follow-up were included as explanatory factors. With respect to mortality risks in relation to exposure duration, no increased risks were found in any of the exposure groups after full adjustment and there was no apparent trend suggesting an exposure-response relation with duration of shift work. The present analysis extends and confirms our previous finding of no excess risk of mortality associated with work in the shift system employed at BASF Ludwigshafen. More specifically, there is also no indication of an increased risk of mortality due to cancer.

Occupational exposure to perfluoroalkyl substances and serum levels of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in an aging population from upstate New York: a retrospective cohort study.

PubMed

Tanner, Eva M; Bloom, Michael S; Wu, Qian; Kannan, Kurunthachalam; Yucel, Recai M; Shrestha, Srishti; Fitzgerald, Edward F

2018-02-01

Perfluoroalkyl substances (PFASs) are environmentally persistent amphiphilic compounds. Exposure to two PFASs, perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) is linked to specific occupations and industries. This study examines the contribution of past occupational PFAS exposure to serum PFOS and PFOA levels among 154 older adults in New York State. Serum PFOS and PFOA levels were compared to data from the National Health and Nutrition Examination Survey (NHANES). Potential occupational exposure to any PFAS was determined from work histories, reviewed by an industrial hygienist, and assessed in relation to current serum PFOS and PFOA levels using exposure probability, duration and cumulative exposure. We observed 25% higher serum PFOS and 80% higher PFOA levels in study participants compared to NHANES. No participants reported PFAS chemical manufacturing work, but n = 68 reported work in occupations and industries known to use PFASs. We found that participants with high cumulative workplace exposure had 34% higher serum PFOS levels compared to participants without occupational exposure, adjusted for age, sex and income. Serum PFOS levels were 26% higher for participants with longer occupational exposure durations. The probability of occupational PFAS exposure metric was not associated with serum PFOS. Serum PFOA was not associated with any measure of occupational exposure. Occupational exposure may contribute to total PFOS body burden in this study population, even among workers not directly involved in manufacturing PFASs. PFAS exposure assessments should evaluate the workplace as a potential source, even when workplace exposures are assumed to be low or moderate.

Retrievable payload carrier, next generation Long Duration Exposure Facility: Update 1992

NASA Technical Reports Server (NTRS)

Perry, A. T.; Cagle, J. A.; Newman, S. C.

1993-01-01

Access to space and cost have been two major inhibitors of low Earth orbit research. The Retrievable Payload Carrier (RPC) Program is a commercial space program which strives to overcome these two barriers to space experimentation. The RPC Program's fleet of spacecraft, ground communications station, payload processing facility, and experienced integration and operations team will provide a convenient 'one-stop shop' for investigators seeking to use the unique vantage point and environment of low Earth orbit for research. The RPC is a regularly launched and retrieved, free-flying spacecraft providing resources adequate to meet modest payload/experiment requirements, and presenting ample surface area, volume, mass, and growth capacity for investigator usage. Enhanced capabilities of ground communications, solar-array-supplied electrical power, central computing, and on-board data storage pick up on the path where NASA's Long Duration Exposure Facility (LDEF) blazed the original technology trail. Mission lengths of 6-18 months, or longer, are envisioned. The year 1992 was designated as the 'International Space Year' and coincides with the 500th anniversary of Christopher Columbus's voyage to the New World. This is a fitting year in which to launch the full scale development of our unique shop of discovery whose intent is to facilitate retrieving technological rewards from another new world: space. Presented is an update on progress made on the RPC Program's development since the November 1991 LDEF Materials Workshop.

Space Radiation Protection, Space Weather, and Exploration

NASA Technical Reports Server (NTRS)

Zapp, Neal; Rutledge, R.; Semones, E. J.; Johnson, A. S.; Guetersloh, S.; Fry, D.; Stoffle, N.; Lee, K.

2008-01-01

Management of crew exposure to radiation is a major concern for manned spaceflight -- and will be even more important for the modern concept of longer-duration exploration. The inherent protection afforded to astronauts by the magnetic field of the Earth in Low Earth Orbit (LEO) makes operations on the space shuttle or space station very different from operations during an exploration mission. In order to experience significant radiation-derived Loss of Mission (LOM) or Loss of Crew (LOC) risk for LEO operations, one is almost driven to dictate extreme duration or to dictate an extreme sequence of solar activity. Outside of the geo-magnetosphere, however, this scenario changes dramatically. Exposures to the same event on the ISS and on the surface of the Moon may differ by multiple orders of magnitude. This change in magnitude, coupled with the logistical constraints present in implementing any practical operational mitigation make situational awareness with regard to space weather a limiting factor for our ability to conduct exploration operations. With these differences in risk to crew, vehicle and mission in mind, we present the status of the efforts currently underway as the required development to enable exploration operations. The changes in the operating environment as crewed operations begin to stretch away from the Earth are changing the way we think about the lines between "research" and "operations". The real, practical work to enable a permanent human presence away from Earth has already begun.

An overview of the on-orbit contamination of the Long Duration Exposure Facility (LDEF)

NASA Technical Reports Server (NTRS)

Stuckey, W. K.

1993-01-01

Contamination that leads to degradation of critical surfaces becomes a vital design issue for many spacecraft programs. One of the processes that must be considered is the on-orbit accumulation of contaminants. The Long Duration Exposure Facility (LDEF) has presented an opportunity to examine the deposits on surfaces returned from orbit in order to help in understanding the deposition processes and the current models used to predict spacecraft contamination levels. The results from various investigators on the contamination of LDEF have implications for material selection, contamination models, and contamination control plans for the design of future spacecraft.

Long-duration orbital effects on optical coating materials

NASA Technical Reports Server (NTRS)

Herzig, Howard; Toft, Albert R.; Fleetwood, Charles M., Jr.

1993-01-01

We flew specimens of eight different optical coating materials in low earth orbit as part of the Long Duration Exposure Facility manifest to determine their ability to withstand exposure to the residual atomic 0 and other environmental effects at those altitudes. We included samples of Al, Au, Ir, Os, Pt, Al + MgF2, Al + SiO(x), and chemical-vapor-deposited SiC, representing reflective optical applications from the vacuum ultraviolet through the visible portions of the spectrum. We found that the majority of the materials suffered sufficient reflectance degradation to warrant careful consideration in the design of future space-flight instrumentation.

WHO European Childhood Obesity Surveillance Initiative: associations between sleep duration, screen time and food consumption frequencies.

PubMed

Börnhorst, Claudia; Wijnhoven, Trudy M A; Kunešová, Marie; Yngve, Agneta; Rito, Ana I; Lissner, Lauren; Duleva, Vesselka; Petrauskiene, Ausra; Breda, João

2015-04-30

Both sleep duration and screen time have been suggested to affect children's diet, although in different directions and presumably through different pathways. The present cross-sectional study aimed to simultaneously investigate the associations between sleep duration, screen time and food consumption frequencies in children. The analysis was based on 10 453 children aged 6-9 years from five European countries that participated in the World Health Organization European Childhood Obesity Surveillance Initiative. Logistic multilevel models were used to assess associations of parent-reported screen time as well as sleep duration (exposure variables) with consumption frequencies of 16 food items (outcome variables). All models were adjusted for age, sex, outdoor play time, maximum educational level of parents and sleep duration or screen time, depending on the exposure under investigation. One additional hour of screen time was associated with increased consumption frequencies of 'soft drinks containing sugar' (1.28 [1.19;1.39]; odds ratio and 99% confidence interval), 'diet/light soft drinks' (1.21 [1.14;1.29]), 'flavoured milk' (1.18 [1.08;1.28]), 'candy bars or chocolate' (1.31 [1.22;1.40]), 'biscuits, cakes, doughnuts or pies' (1.22 [1.14;1.30]), 'potato chips (crisps), corn chips, popcorn or peanuts' (1.32 [1.20;1.45]), 'pizza, French fries (chips), hamburgers'(1.30 [1.18;1.43]) and with a reduced consumption frequency of 'vegetables (excluding potatoes)' (0.89 [0.83;0.95]) and 'fresh fruits' (0.91 [0.86;0.97]). Conversely, one additional hour of sleep duration was found to be associated with increased consumption frequencies of 'fresh fruits' (1.11 [1.04;1.18]) and 'vegetables (excluding potatoes)' (1.14 [1.07;1.23]). The results suggest a potential relation between high screen time exposure and increased consumption frequencies of foods high in fat, free sugar or salt whereas long sleep duration may favourably be related to children's food choices. Both screen time and sleep duration are modifiable behaviours that may be tackled in childhood obesity prevention efforts.

Models for mesothelioma incidence following exposure to fibers in terms of timing and duration of exposure and the biopersistence of the fibers.

PubMed

Berry, G

1999-02-01

The health effects of inhaled fibers are related to the intensity and duration of exposure and occur many years after the exposure. In particular, the incidence of mesothelioma after exposure to asbestos is proportional to the intensity of exposure (fibers per milliliter of air) and the duration of exposure, and to the time that has elapsed since the exposure. The incidence increases with time since exposure to a power of between 3 and 4. The disease process resulting from exposure to fibers in the air is presumably related to the dose of fibers in the lungs, which depends on the exposure level and duration, and also on the size characteristics of the fibers influencing their inhalation and retention in the lungs. Models incorporating these characteristics have been found to be satisfactory in explaining the incidence of mesothelioma over time after exposure to asbestos. Most of the epidemiological modeling has been for occupational exposure to one of the amphibole asbestos types (crocidolite or amosite), for which heavy exposure produces a high incidence of mesothelioma. Occupational exposure to chrysotile asbestos has resulted in a much lower incidence of mesothelioma. Crocidolite asbestos is much more biopersistent than chrysotile asbestos in the sense that after retention in the lungs it is eliminated only slowly (half-time of several years). If fibers are eliminated then the dose in the lungs declines following exposure, and this may influence the disease process. This concept is more important for synthetic mineral fibers, such as glass wool, which are used as a substitute for asbestos. These fibers are much less biopersistent than asbestos, with half-times of weeks or even days. Biopersistence is related to the dissolution of fibers. This is a physical-chemical process that may be expected to proceed at about the same rate in rats and humans. The predicted effect of biopersistence of fibers has been explored using the basic mesothelioma incidence model generalized to include a term representing exponential elimination over time. The influence of solubility of fibers on the mesothelioma rate is 17 times higher in humans than in rats. This is because rats are aging and developing cancer at a much quicker rate than humans, and hence the influence of dissolution is less. Thus, the predicted mesothelioma incidence in humans is highly dependent on the rate of elimination across the range covering asbestos and the more durable synthetic fibers, but in rats a similar dependence occurs at a 17 times higher rate of elimination corresponding to the less durable synthetic fibers. The possible carcinogenic effects of fibers are often determined from animal experiments, but these results suggest that the extrapolation from rats to humans is highly dependent on the biopersistence of fibers, in the situation where the elimination is through dissolution of fibers at a rate independent of species and the speed of the cancer process is species dependent. This implies that relatively soluble fibers that do not produce disease in rat experiments are even less likely to produce disease in humans.

A PDF/NPF neuropeptide signaling circuitry of male Drosophila melanogaster controls rival-induced prolonged mating.

PubMed

Kim, Woo Jae; Jan, Lily Yeh; Jan, Yuh Nung

2013-12-04

A primary function of males for many species involves mating with females for reproduction. Drosophila melanogaster males respond to the presence of other males by prolonging mating duration to increase the chance of passing on their genes. To understand the basis of such complex behaviors, we examine the genetic network and neural circuits that regulate rival-induced Longer-Mating-Duration (LMD). Here, we identify a small subset of clock neurons in the male brain that regulate LMD via neuropeptide signaling. LMD requires the function of pigment-dispersing factor (PDF) in four s-LNv neurons and its receptor PDFR in two LNd neurons per hemisphere, as well as the function of neuropeptide F (NPF) in two neurons within the sexually dimorphic LNd region and its receptor NPFR1 in four s-LNv neurons per hemisphere. Moreover, rival exposure modifies the neuronal activities of a subset of clock neurons involved in neuropeptide signaling for LMD. Copyright © 2013 Elsevier Inc. All rights reserved.

A PDF/NPF neuropeptide signaling circuitry of male Drosophila melanogaster controls rival-induced prolonged mating

PubMed Central

Kim, Woo Jae; Jan, Lily Yeh; Jan, Yuh Nung

2013-01-01

SUMMARY A primary function of males for many species involves mating with females for reproduction. Drosophila melanogaster males respond to the presence of other males by prolonging mating duration to increase the chance of passing on their genes. To understand the basis of such complex behaviors, we examine the genetic network and neural circuits that regulate rival-induced longer mating duration (LMD). Here we identify a small subset of clock neurons in the male brain that regulate LMD via neuropeptide signaling. LMD requires the function of pigment-dispersing factor (PDF) in four s-LNv neurons and its receptor PDFR in two LNd neurons per hemisphere, as well as the function of neuropeptide F (NPF) in two neurons within the sexually dimorphic LNd region and its receptor NPFR1 in four s-LNv neurons per hemisphere. Moreover, rival exposure modifies the neuronal activities of a subset of clock neurons involved in neuropeptide signaling for LMD. PMID:24314729

U.S. view of human problems to be addressed for long duration space flights. [physiological and psychological effects

NASA Technical Reports Server (NTRS)

Berry, C. A.

1973-01-01

The Russian and American space programs have consisted of several thousands of hours of exposure of man to the space environment. In spite of numerous biological phenomena of adaptation observed, the space travellers have displayed, after their return, no enduring pathological effect. Although the usable data remain too limited to reflect fully the effects of space flight, it is possible to sketch the biological responses in the absence of gravity and to define the work bases for the future. Beyond its basic physiological effects, weightlessness has operational consequences in the daily life of the astronauts. These consequences will be still more evident during missions of long duration. The conclusions drawn in flight as well as on the ground are reviewed, and future requirements concerning prolonged flights are outlined. The gaps in actual knowledge are discussed and solutions are suggested. The problems of habitability are considered, particularly those which remain at present without satisfactory solutions: psychological responses to a confined life, cleaning, hygiene, and used material.

Human Research Program Human Health Countermeasures Element: Evidence Report - Artificial Gravity

NASA Technical Reports Server (NTRS)

Clement, Gilles

2015-01-01

The most serious risks of long-duration flight involve radiation, behavioral stresses, and physiological deconditioning. Artificial gravity (AG), by substituting for the missing gravitational cues and loading in space, has the potential to mitigate the last of these risks by preventing the adaptive responses from occurring. The rotation of a Mars-bound spacecraft or an embarked human centrifuge offers significant promise as an effective, efficient multi-system countermeasure against the physiological deconditioning associated with prolonged weightlessness. Virtually all of the identified risks associated with bone loss, muscle weakening, cardiovascular deconditioning, and sensorimotor disturbances might be alleviated by the appropriate application of AG. However, experience with AG in space has been limited and a human-rated centrifuge is currently not available on board the ISS. A complete R&D program aimed at determining the requirements for gravity level, gravity gradient, rotation rate, frequency, and duration of AG exposure is warranted before making a decision for implementing AG in a human spacecraft.

Hazards To The Eye From UV

NASA Astrophysics Data System (ADS)

Zuclich, Joseph A.

1980-10-01

Ocular effects of ultraviolet radiation, 200-400 nm, are reviewed. Depending upon the exposure parameter involved, UV radiation may be harmful to the cornea, lens and/or retina. Ranges of exposure parameters (wavelength, exposure duration, etc.) for which each of the tissues is susceptible are specified and the nature of the tissue is described. Present understanding of the thermal and photochemical damage mechanism operative for various conditions of exposure are discussed Ocular damage thresholds for wide ranges of exposure parameters are summarized and compared to existing safety standards.

Predicting the acute behavioral effects in rats inhaling toluene (or up to 24 hrs: Inhaled vs. internal dose metrics.

EPA Science Inventory

The acute toxicity oftoluene, a model volatile organic compound (VOC), depends on the concentration (C) and duration (t) ofexposure, and guidelines for acute exposures have traditionally used ext relationships to extrapolate protective and/or effective concentrations across durat...

Meta-analysis on occupational exposure to pesticides--neurobehavioral impact and dose-response relationships.

PubMed

Meyer-Baron, Monika; Knapp, Guido; Schäper, Michael; van Thriel, Christoph

2015-01-01

While the health impact of high exposures to pesticides is acknowledged, the impact of chronic exposures in the absence of acute poisonings is controversial. A systematic analysis of dose-response relationships is still missing. Its absence may provoke alternative explanations for altered performances. Consequently, opportunities for health prevention in the occupational and environmental field may be missed. Objectives were (1) quantification of the neurotoxic impact of pesticides by an analysis of functional alterations in workers measured by neuropsychological performance tests, (2) estimates of dose-response relationships on the basis of exposure duration, and (3) exploration of susceptible subgroups. The meta-analysis employed a random effects model to obtain overall effects for individual performance tests. Twenty-two studies with a total of 1758 exposed and 1260 reference individuals met the inclusion criteria. At least three independent outcomes were available for twenty-six performance variables. Significant performance effects were shown in adults and referred to both cognitive and motor performances. Effect sizes ranging from dRE=-0.14 to dRE=-0.67 showed consistent outcomes for memory and attention. Relationships between effect sizes and exposure duration were indicated for individual performance variables and the total of measured performances. Studies on adolescents had to be analyzed separately due to numerous outliers. The large variation among outcomes hampered the analysis of the susceptibility in this group, while data on female workers was too scant for the analysis. Relationships exist between the impact of pesticides on performances and exposure duration. A change in test paradigms would help to decipher the impact more specifically. The use of biomarkers appropriate for lower exposures would allow a better prevention of neurotoxic effects due to occupational and environmental exposure. Intervention studies in adolescents seem warranted to specify their risk. Copyright © 2014 Elsevier Inc. All rights reserved.

Recreational use assessment of water-based activities, using time-lapse construction cameras.

PubMed

Sunger, Neha; Teske, Sondra S; Nappier, Sharon; Haas, Charles N

2012-01-01

Recreational exposure to surface waters during periods of increased pathogen concentration may lead to a significantly higher risk of illness. However, estimates of elementary exposure factors necessary to evaluate health risk (i.e., usage distributions and exposure durations) are not available for many non-swimming water-related activities. No prior studies have assessed non-swimming water exposure with respect to factors leading to impaired water quality from increased pathogen concentration, such as weather condition (rain events produce increased runoff and sewer overflows) and type of day (heavy recreational periods). We measured usage patterns and evaluated the effect of weather and type of day at eight water sites located within Philadelphia, by using a novel "time lapse photography" technology during three peak recreational seasons (May-September) 2008-2010. Camera observations validated with simultaneous in-person surveys exhibited a strong correlation (R(2)=0.81 to 0.96) between the two survey techniques, indicating that the application of remote photography in collecting human exposure data was appropriate. Recreational activities usage varied more on a temporal basis than due to inclement weather. Only 14% (6 out of 44) of the site-specific activity combinations showed dry weather preference, whereas 41.5% (17 out of 41) of the combinations indicated greater usage on weekends as compared with weekday. In general, the log normal distribution described the playing and wading duration distribution, while the gamma distribution was the best fit for fishing durations. Remote photography provided unbiased, real-time human exposure data and was less personnel intensive compared with traditional survey methods. However, there are potential limitations associated with remote surveillance data related to its limited view. This is the first study to report that time lapse cameras can be successfully applied to assess water-based human recreational patterns and can provide precise exposure statistics for non-swimming recreational exposures.

Risk of subacromial shoulder disorder in airport baggage handlers: combining duration and intensity of musculoskeletal shoulder loads.

PubMed

Møller, Sanne Pagh; Brauer, Charlotte; Mikkelsen, Sigurd; Alkjær, Tine; Koblauch, Henrik; Pedersen, Ellen Bøtker; Simonsen, Erik B; Thygesen, Lau Caspar

2018-04-01

Musculoskeletal shoulder load among baggage handlers measured by combining duration and intensity based on biomechanical and epidemiological information may be a stronger predictor of subacromial shoulder disorders than baggage handler seniority. In 2012, a cohort of baggage handlers employed at Copenhagen Airport in 1990-2012, and a cohort of unskilled otherwise employed men answered a survey. Self-reported information on work tasks during employment in the airport in combination with work task specific biomechanically modelled forces in the shoulder joint was used to estimate shoulder load. Exposure measures were accumulated shoulder abduction moment, accumulated shoulder compression force, accumulated supraspinatus force and baggage handler seniority. The outcome was subacromial shoulder disorder registered in the Danish National Patient Register. When analyses were adjusted by all confounders except age, exposure variables showed close to significant associations with subacromial shoulder disorder. Results could not confirm our hypothesis that combined information on work task duration and shoulder load intensity was stronger associated with subacromial shoulder disorder than seniority. Practitioner Summary: In this study we sought to identify if the exposure to work-related musculoskeletal shoulder loading including duration and intensity among baggage handlers was associated with subacromial shoulder disorder. We found that there was an association but this was not stronger than that between baggage handler seniority and subacromial shoulder disorder.

19 CFR 360.105 - Duration of the steel import licensing requirement.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 19 Customs Duties 3 2010-04-01 2010-04-01 false Duration of the steel import licensing requirement. 360.105 Section 360.105 Customs Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE STEEL IMPORT MONITORING AND ANALYSIS SYSTEM § 360.105 Duration of the steel import licensing requirement...

19 CFR 360.105 - Duration of the steel import licensing requirement.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 19 Customs Duties 3 2011-04-01 2011-04-01 false Duration of the steel import licensing requirement. 360.105 Section 360.105 Customs Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE STEEL IMPORT MONITORING AND ANALYSIS SYSTEM § 360.105 Duration of the steel import licensing requirement...

19 CFR 360.105 - Duration of the steel import licensing requirement.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 19 Customs Duties 3 2013-04-01 2013-04-01 false Duration of the steel import licensing requirement. 360.105 Section 360.105 Customs Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE STEEL IMPORT MONITORING AND ANALYSIS SYSTEM § 360.105 Duration of the steel import licensing requirement...

19 CFR 360.105 - Duration of the steel import licensing requirement.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 19 Customs Duties 3 2012-04-01 2012-04-01 false Duration of the steel import licensing requirement. 360.105 Section 360.105 Customs Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE STEEL IMPORT MONITORING AND ANALYSIS SYSTEM § 360.105 Duration of the steel import licensing requirement...

19 CFR 360.105 - Duration of the steel import licensing requirement.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 19 Customs Duties 3 2014-04-01 2014-04-01 false Duration of the steel import licensing requirement. 360.105 Section 360.105 Customs Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE STEEL IMPORT MONITORING AND ANALYSIS SYSTEM § 360.105 Duration of the steel import licensing requirement...

Hearing risk associated with the usage of personal listening devices among urban high school students in Malaysia.

PubMed

Sulaiman, A H; Seluakumaran, K; Husain, R

2013-08-01

To investigate listening habits and hearing risks associated with the use of personal listening devices among urban high school students in Malaysia. Cross-sectional, descriptive study. In total, 177 personal listening device users (13-16 years old) were interviewed to elicit their listening habits (e.g. listening duration, volume setting) and symptoms of hearing loss. Their listening levels were also determined by asking them to set their usual listening volume on an Apple iPod TM playing a pre-selected song. The iPod's sound output was measured with an artificial ear connected to a sound level meter. Subjects also underwent pure tone audiometry to ascertain their hearing thresholds at standard frequencies (0.5-8 kHz) and extended high frequencies (9-16 kHz). The mean measured listening level and listening duration for all subjects were 72.2 dBA and 1.2 h/day, respectively. Their self-reported listening levels were highly correlated with the measured levels (P < 0.001). Subjects who listened at higher volumes also tend to listen for longer durations (P = 0.012). Male subjects listened at a significantly higher volume than female subjects (P = 0.008). When sound exposure levels were compared with the recommended occupational noise exposure limit, 4.5% of subjects were found to be listening at levels which require mandatory hearing protection in the occupational setting. Hearing loss (≥25 dB hearing level at one or more standard test frequencies) was detected in 7.3% of subjects. Subjects' sound exposure levels from the devices were positively correlated with their hearing thresholds at two of the extended high frequencies (11.2 and 14 kHz), which could indicate an early stage of noise-induced hearing loss. Although the average high school student listened at safe levels, a small percentage of listeners were exposed to harmful sound levels. Preventive measures are needed to avoid permanent hearing damage in high-risk listeners. Copyright © 2013 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.

Crew health

NASA Technical Reports Server (NTRS)

Billica, Roger D.

1992-01-01

Crew health concerns for Space Station Freedom are numerous due to medical hazards from isolation and confinement, internal and external environments, zero gravity effects, occupational exposures, and possible endogenous medical events. The operational crew health program will evolve from existing programs and from life sciences investigations aboard Space Station Freedom to include medical monitoring and certification, medical intervention, health maintenance and countermeasures, psychosocial support, and environmental health monitoring. The knowledge and experience gained regarding crew health issues and needs aboard Space Station Freedom will be used not only to verify requirements and programs for long duration space flight, but also in planning and preparation for Lunar and Mars exploration and colonization.

Evaluation of inertial cavitation activity in tissue through measurement of oxidative stress.

PubMed

Prieur, Fabrice; Pialoux, Vincent; Mestas, Jean-Louis; Mury, Pauline; Skinner, Sarah; Lafon, Cyril

2015-09-01

Ultrasound cavitation is an essential mechanism involved in the therapeutic local enhancement of drug delivery by ultrasound for cancer treatment. Inertial cavitation also triggers chemical reactions that generate free radicals and subsequent oxidative stress in the tissue. The aim of this study was to measure the oxidative stress induced by inertial cavitation in ex vivo tissue and to test the association between the exposure conditions and the oxidative stress. A confocal ultrasound setup was used to sonicate and create inertial cavitation in freshly excised adipose pig tissue. The ex vivo tissue samples were then processed to measure the quantity of malondialdehyde (MDA), an end-product of polyunsaturated free fatty acid oxidation. The creation of hydroxyterephthalic acid (HTA) from the reaction of terephthalic acid (TA) with free radicals in water was also quantified in vitro. Samples were sonicated for different durations using various amplitudes for the applied pressure. The results showed a minimum 2-fold increase in the amount of detected MDA in the sonicated tissue samples compared to baseline clearly suggesting the generation of free radicals by inertial cavitation. The method exhibited a moderate dependence of MDA generated upon the duration of exposure (R(2)=057,p<0.0001). The average increase in MDA concentration was approximately 2-fold, 5-fold, 6-fold, and 9-fold for exposure durations per unit of volume of 0.13, 0.17, 0.25, and 0.50s/mm(3), respectively. The results showed no statistically significant dependence on the amplitude of the pressure within the used range. Both pressure amplitude and exposure duration, however, influenced the HTA concentration (R(2)>0.95,p<0.0001). This biochemical method can be used on ex vivo tissue to detect the generation of free radicals induced by inertial cavitation. In large enough sample populations, the cavitation activity is linked to the exposure conditions of the sonication. Copyright © 2015 Elsevier B.V. All rights reserved.

DESIGN STREAM FLOWS BASED ON HARMONIC MEANS.

EPA Science Inventory

Design streamflows are frequently used in water quality studies to provide adequate protection against pollutant exposure periods of a given duration. By analyzing the effect that simple streamflow dilution has on x-day average exposure levels of a pollutant, it appears that the ...

Space Radiation Risks for Astronauts on Multiple International Space Station Missions

PubMed Central

Cucinotta, Francis A.

2014-01-01

Mortality and morbidity risks from space radiation exposure are an important concern for astronauts participating in International Space Station (ISS) missions. NASA’s radiation limits set a 3% cancer fatality probability as the upper bound of acceptable risk and considers uncertainties in risk predictions using the upper 95% confidence level (CL) of the assessment. In addition to risk limitation, an important question arises as to the likelihood of a causal association between a crew-members’ radiation exposure in the past and a diagnosis of cancer. For the first time, we report on predictions of age and sex specific cancer risks, expected years of life-loss for specific diseases, and probability of causation (PC) at different post-mission times for participants in 1-year or multiple ISS missions. Risk projections with uncertainty estimates are within NASA acceptable radiation standards for mission lengths of 1-year or less for likely crew demographics. However, for solar minimum conditions upper 95% CL exceed 3% risk of exposure induced death (REID) by 18 months or 24 months for females and males, respectively. Median PC and upper 95%-confidence intervals are found to exceed 50% for several cancers for participation in two or more ISS missions of 18 months or longer total duration near solar minimum, or for longer ISS missions at other phases of the solar cycle. However, current risk models only consider estimates of quantitative differences between high and low linear energy transfer (LET) radiation. We also make predictions of risk and uncertainties that would result from an increase in tumor lethality for highly ionizing radiation reported in animal studies, and the additional risks from circulatory diseases. These additional concerns could further reduce the maximum duration of ISS missions within acceptable risk levels, and will require new knowledge to properly evaluate. PMID:24759903

Space radiation risks for astronauts on multiple International Space Station missions.

PubMed

Cucinotta, Francis A

2014-01-01

Mortality and morbidity risks from space radiation exposure are an important concern for astronauts participating in International Space Station (ISS) missions. NASA's radiation limits set a 3% cancer fatality probability as the upper bound of acceptable risk and considers uncertainties in risk predictions using the upper 95% confidence level (CL) of the assessment. In addition to risk limitation, an important question arises as to the likelihood of a causal association between a crew-members' radiation exposure in the past and a diagnosis of cancer. For the first time, we report on predictions of age and sex specific cancer risks, expected years of life-loss for specific diseases, and probability of causation (PC) at different post-mission times for participants in 1-year or multiple ISS missions. Risk projections with uncertainty estimates are within NASA acceptable radiation standards for mission lengths of 1-year or less for likely crew demographics. However, for solar minimum conditions upper 95% CL exceed 3% risk of exposure induced death (REID) by 18 months or 24 months for females and males, respectively. Median PC and upper 95%-confidence intervals are found to exceed 50% for several cancers for participation in two or more ISS missions of 18 months or longer total duration near solar minimum, or for longer ISS missions at other phases of the solar cycle. However, current risk models only consider estimates of quantitative differences between high and low linear energy transfer (LET) radiation. We also make predictions of risk and uncertainties that would result from an increase in tumor lethality for highly ionizing radiation reported in animal studies, and the additional risks from circulatory diseases. These additional concerns could further reduce the maximum duration of ISS missions within acceptable risk levels, and will require new knowledge to properly evaluate.

Factors associated with reduced radiation exposure, cost, and technical difficulty of inferior vena cava filter placement and retrieval.

PubMed

Neill, Matthew; Charles, Hearns W; Pflager, Daniel; Deipolyi, Amy R

2017-01-01

We sought to delineate factors of inferior vena cava filter placement associated with increased radiation and cost and difficult subsequent retrieval. In total, 299 procedures from August 2013 to December 2014, 252 in a fluoroscopy suite (FS) and 47 in the operating room (OR), were reviewed for radiation exposure, fluoroscopy time, filter type, and angulation. The number of retrieval devices and fluoroscopy time needed for retrieval were assessed. Multiple linear regression assessed the impact of filter type, procedure location, and patient and procedural variables on radiation dose, fluoroscopy time, and filter angulation. Logistic regression assessed the impact of filter angulation, type, and filtration duration on retrieval difficulty. Access site and filter type had no impact on radiation exposure. However, placement in the OR, compared to the FS, entailed more radiation (156.3 vs 71.4 mGy; P = 0.001), fluoroscopy time (6.1 vs 2.8 min; P < 0.001), and filter angulation (4.8° vs 2.6°; P < 0.001). Angulation was primarily dependent on filter type ( P = 0.02), with VenaTech and Denali filters associated with decreased angulation (2.2°, 2.4°) and Option filters associated with greater angulation (4.2°). Filter angulation, but not filter type or filtration duration, predicted cases requiring >1 retrieval device ( P < 0.001) and >30 min fluoroscopy time ( P = 0.02). Cost savings for placement in the FS vs OR were estimated at $444.50 per case. In conclusion, increased radiation and cost were associated with placement in the OR. Filter angulation independently predicted difficult filter retrieval; angulation was determined by filter type. Performing filter placement in the FS using specific filters may reduce radiation and cost while enabling future retrieval.

Temporal Progression of Visual Injury from Blast Exposure

DTIC Science & Technology

2017-09-01

seen throughout the duration of the study. To correlate experimental blast exposures in rodents to human blast exposures, a computational parametric...software (JMP 10.0, Cary,NC). Descriptive and univariate analyses will first be performed to identify the occurrence of delayed visual system...later). The biostatistician evaluating the retrospective data has completed the descriptive analysis and is working on the multiple regression. Table

Interactive vs passive screen time and nighttime sleep duration among school-aged children

PubMed Central

Yland, Jennifer; Guan, Stanford; Emanuele, Erin; Hale, Lauren

2016-01-01

Background Insufficient sleep among school-aged children is a growing concern, as numerous studies have shown that chronic short sleep duration increases the risk of poor academic performance and specific adverse health outcomes. We examined the association between weekday nighttime sleep duration and 3 types of screen exposure: television, computer use, and video gaming. Methods We used age 9 data from an ethnically diverse national birth cohort study, the Fragile Families and Child Wellbeing Study, to assess the association between screen time and sleep duration among 9-year-olds, using screen time data reported by both the child (n = 3269) and by the child's primary caregiver (n= 2770). Results Within the child-reported models, children who watched more than 2 hours of television per day had shorter sleep duration by approximately 11 minutes per night compared to those who watched less than 2 hours of television (β = −0.18; P < .001). Using the caregiver-reported models, both television and computer use were associated with reduced sleep duration. For both child- and parent-reported screen time measures, we did not find statistically significant differences in effect size across various types of screen time. Conclusions Screen time from televisions and computers is associated with reduced sleep duration among 9-year-olds, using 2 sources of estimates of screen time exposure (child and parent reports). No specific type or use of screen time resulted in significantly shorter sleep duration than another, suggesting that caution should be advised against excessive use of all screens. PMID:27540566

[Eye lens radiation exposure during ureteroscopy with and without a face protection shield: Investigations on a phantom model].

PubMed

Zöller, G; Figel, M; Denk, J; Schulz, K; Sabo, A

2016-03-01

Eye lens radiation exposure during radiologically-guided endoscopic procedures may result in radiation-induced cataracts; therefore, we investigated the ocular radiation exposure during ureteroscopy on a phantom model. Using an Alderson phantom model and eye lens dosimeters, we measured the ocular radiation exposure depending on the number of X-ray images and on the duration of fluoroscopic imaging. The measurements were done with and without using a face protection shield. We could demonstrate that a significant ocular radiation exposure can occur, depending on the number of X-ray images and on the duration time of fluoroscopy. Eye lens doses up to 0.025 mSv were recorded even using modern digital X-ray systems. Using face protection shields this ocular radiation exposure can be reduced to a minimum. The International Commission on Radiological Protection (ICRP) recommendations of a mean eye lens dosage of 20 mSv/year may be exceeded during repeated ureteroscopy by a high volume surgeon. Using a face protection shield, the eye lens dose during ureteroscopy could be reduced to a minimum in a phantom model. Further investigations will show whether these results can be transferred to real life ureteroscopic procedures.

Assessment of radiation exposure from cesium-137 contaminated roads for epidemiological studies in Seoul, Korea.

PubMed

Lee, Yun-Keun; Ju, Young-Su; Lee, Won Jin; Hwang, Seung Sik; Yim, Sang-Hyuk; Yoo, Sang-Chul; Lee, Jieon; Choi, Kyung-Hwa; Burm, Eunae; Ha, Mina

2015-01-01

We aimed to assess the radiation exposure for epidemiologic investigation in residents exposed to radiation from roads that were accidentally found to be contaminated with radioactive cesium-137 ((137)Cs) in Seoul. Using information regarding the frequency and duration of passing via the (137)Cs contaminated roads or residing/working near the roads from the questionnaires that were obtained from 8875 residents and the measured radiation doses reported by the Nuclear Safety and Security Commission, we calculated the total cumulative dose of radiation exposure for each person. Sixty-three percent of the residents who responded to the questionnaire were considered as ever-exposed and 1% of them had a total cumulative dose of more than 10 mSv. The mean (minimum, maximum) duration of radiation exposure was 4.75 years (0.08, 11.98) and the geometric mean (minimum, maximum) of the total cumulative dose was 0.049 mSv (<0.001, 35.35) in the exposed. An individual exposure assessment was performed for an epidemiological study to estimate the health risk among residents living in the vicinity of (137)Cs contaminated roads. The average exposure dose in the exposed people was less than 5% of the current guideline.

Intensity of exposure to a patient activation intervention and patient engagement in medical visit communication.

PubMed

Ibe, Chidinma; Bowie, Janice; Roter, Debra; Carson, Kathryn A; Lee, Bone; Monroe, Dwyan; Cooper, Lisa A

2017-07-01

We examined associations between intensity of exposure to a community health worker (CHW) delivered communication activation intervention targeting low-income patients with hypertension. We analyzed question-asking behaviors of patients assigned to the intervention arms (n=140) in a randomized controlled trial. Intensity of exposure to the intervention was operationalized as the duration of face-to-face coaching and number of protocol-specified topics discussed. Mixed effects models characterized the relationship between intensity of exposure and patients' communication in a subsequent medical visit. The number of topics discussed during the coaching session was positively associated with patients' asking psychosocial-related questions during their visit. The duration of the coaching session was positively associated with patients' use of communication engagement strategies to facilitate their participation in the visit dialogue. Exposure to a physician trained in patient-centered communication did not influence these relationships. A dose-response relationship was observed between exposure to a CHW- delivered communication activation intervention and patient-provider communication. This study supports the use of CHWs in activating patients toward greater communication in the therapeutic exchange. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparison of the behavior of stainless and mild steel manual metal arc welding fumes in rat lung.

PubMed

Kalliomäki, P L; Junttila, M L; Kalliomäki, K K; Lakomaa, E L; Kivelä, R

1983-04-01

The lung retention and clearance of manual metal arc (MMA) stainless steel and mild steel welding fumes were determined in the rat. The exposure simulated the actual welding situation. The duration of exposure in the "nose-only" exposure chamber was 1 h/workday for one, two, three, or four weeks in the retention study and for four weeks in the clearance study. The concentration of exogenous iron was determined by the magnetic measuring method. Instrumental neutron activation analysis was applied to determine the concentration of total iron, chromium, and nickel in the lungs. The results indicated that the lung retention and clearance patterns for the two types of welding fumes were different. A linear relationship was observed between the amount of stainless steel MMA welding fume retained in the lungs and the duration of exposure, whereas the retention of mild steel MMA welding fume in the lung was saturated as a function of the cumulative exposure time rates. The maximum amount of lung-retained contaminants was 880 micrograms for stainless steel MMA welding fume and 220 micrograms for mild steel MMA fume.

Effects of long-term non-traumatic noise exposure on the adult central auditory system. Hearing problems without hearing loss.

PubMed

Eggermont, Jos J

2017-09-01

It is known that hearing loss induces plastic changes in the brain, causing loudness recruitment and hyperacusis, increased spontaneous firing rates and neural synchrony, reorganizations of the cortical tonotopic maps, and tinnitus. Much less in known about the central effects of exposure to sounds that cause a temporary hearing loss, affect the ribbon synapses in the inner hair cells, and cause a loss of high-threshold auditory nerve fibers. In contrast there is a wealth of information about central effects of long-duration sound exposures at levels ≤80 dB SPL that do not even cause a temporary hearing loss. The central effects for these moderate level exposures described in this review include changes in central gain, increased spontaneous firing rates and neural synchrony, and reorganization of the cortical tonotopic map. A putative mechanism is outlined, and the effect of the acoustic environment during the recovery process is illustrated. Parallels are drawn with hearing problems in humans with long-duration exposures to occupational noise but with clinical normal hearing. Copyright © 2016 Elsevier B.V. All rights reserved.

Changes in compensatory eye movements associated with simulated stimulus conditions of spaceflight

NASA Technical Reports Server (NTRS)

Harm, Deborah L.; Zografos, Linda M.; Skinner, Noel C.; Parker, Donald E.

1993-01-01

Compensatory vertical eye movement gain (CVEMG) was recorded during pitch oscillation in darkness before, during, and immediately after exposures to the stimulus rearrangement produced by the Preflight Adaptation Trainer (PAT) Tilt-Translation Device (TTD). The TTD is designed to elicit adaptive responses that are similar to those observed in microgravity-adapted astronauts. The data from Experiment 1 yielded a statistically significant CVEMG decrease following 15 min of exposure to a stimulus rearrangement condition where the phase angle between subject pitch tilt and visual scene translation was 270 deg; statistically significant gain decreases were not observed following exposures either to a condition where the phase angle between subject pitch and scene translation was 90 deg or to a no-stimulus-rearrangement condition. Experiment 2 replicated the 270-deg-phase condition from Experiment 1 and extended the exposure duration from 30 to 45 min. Statistically significant additional changes in CVEMG associated with the increased exposure duration were not observed. The adaptation time constant estimated fram the combined data from Experiments 1 and 2 was 29 min.

Changes in Compensatory Eye Movements Associated with Simulated Stimulus Conditions of Spaceflight

NASA Technical Reports Server (NTRS)

Harm, Deborah L.; Zografos, Linda M.; Skinner, Noel C.; Parker, Donald E.

1993-01-01

Compensatory vertical eye movement gain (CVEMG) was recorded during pitch oscillation in darkness before, during and immediately after exposures to the stimulus rearrangement produced by the Preflight Adaptation Trainer (PAT) Tilt-Translation Device (TTD). The TTD is designed to elicit adaptive responses that are similar to those observed in microgravity-adapted astronauts. The data from Experiment 1 yielded a statistically significant CVEMG decrease following 15 minutes of exposure to a stimulus rearrangement condition where the phase angle between subject pitch tilt and visual scene translation was 270 degrees; statistically significant gain decreases were not observed following exposures either to a condition where the phase angle between subject pitch and scene translation was 90 degrees or to a no-stimulus-rearrangement condition. Experiment 2 replicated the 270 degree phase condition from Experiment 1 and extended the exposure duration from 30 to 45 minutes. Statistically significant additional changes in CVEMG associated with the increased exposure duration were not observed. The adaptation time constant estimated from the combined data from Experiments 1 and 2 was 29 minutes.

Effect of exposure to solid wastes in relation to employment duration on some important markers of health and disease in waste management workers of Ogun State in southwest Nigeria.

PubMed

Odewabi, Adesina O; Ogundahunsi, Omobola A; Ekor, Martins

2013-12-01

Waste management workers (WMWs) around the world are at risk of work-related health disorders. The influence of employment duration on individuals occupationally exposed to solid waste was investigated in this study. The study comprised (n = 280) 180 WMWs and 100 controls. Employment duration was obtained from questionnaire survey and categorized into three groups: group I (0.5-2 years), group II (>2-4 years) and group III (>4-6 years). Blood sample (10 ml) was collected from the antecubital vein of subjects for analysis. WMWs exhibited significantly (p < 0.001) elevated inflammatory markers (erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and ceruloplasmin (Cp)) relative to control. While Cp increased, ESR and CRP decreased with increasing WMWs' employment duration. Alteration in oxidant/antioxidant markers was characterized by significant (p < 0.001) decrease in ferric-reducing ability of plasma (FRAP) and catalase activity together with marked (p < 0.01) elevation of thiobarbituric acid reactive substances (TBARS) and uric acid (UA). TBARS, UA and FRAP increased while catalase decreased with WMWs' employment duration. In addition, WMWs exhibited significantly (p < 0.01) elevated immunoglobulin A (IgA) and IgG, which also increased and decreased, respectively, with job duration. The significantly (p < 0.01) decreased haemoglobin and haematocrit levels as well as the significantly (p < 0.001) elevated total leukocytes in WMWs increased with employment duration. Alanine aminotransferase increased and albumin decreased significantly (p < 0.05) in WMWs, and these changes also increased and decreased, respectively, with job duration. Data suggest that levels of alteration of important systemic markers of health/disease are related to WMWs' employment or exposure duration.

The anticholinergic and antiglutamatergic drug caramiphen reduces seizure duration in soman-exposed rats: Synergism with the benzodiazepine diazepam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schultz, M.K.; Wright, L.K.M.; Stone, M.F.

2012-03-15

Therapy of seizure activity following exposure to the nerve agent soman (GD) includes treatment with the anticonvulsant diazepam (DZP), an allosteric modulator of γ-aminobutyric acid A (GABA{sub A}) receptors. However, seizure activity itself causes the endocytosis of GABA{sub A} receptors and diminishes the inhibitory effects of GABA, thereby reducing the efficacy of DZP. Treatment with an N-methyl-D-aspartic acid (NMDA) receptor antagonist prevents this reduction in GABAergic inhibition. We examined the efficacy of the NMDA receptor antagonist caramiphen edisylate (CED; 20 mg/kg, im) and DZP (10 mg/kg, sc), administered both separately and in combination, at 10, 20 or 30 min followingmore » seizure onset for attenuation of the deleterious effects associated with GD exposure (1.2 LD{sub 50}; 132 μg/kg, sc) in rats. Outcomes evaluated were seizure duration, neuropathology, acetylcholinesterase (AChE) activity, body weight, and temperature. We also examined the use of the reversible AChE inhibitor physostigmine (PHY; 0.2 mg/kg, im) as a therapy for GD exposure. We found that the combination of CED and DZP yielded a synergistic effect, shortening seizure durations and reducing neuropathology compared to DZP alone, when treatment was delayed 20–30 min after seizure onset. PHY reduced the number of animals that developed seizures, protected a fraction of AChE from GD inhibition, and attenuated post-exposure body weight and temperature loss independent of CED and/or DZP treatment. We conclude that: 1) CED and DZP treatment offers considerable protection against the effects of GD and 2) PHY is a potential therapeutic option following GD exposure, albeit with a limited window of opportunity. -- Highlights: ► Soman (GD) produced seizure activity resulting in neuropathology in rats. ► Tx: caramiphen (CED) and/or diazepam (DZP) @ 10, 20 or 30 min after seizure onset. ► CED/DZP showed superior anticonvulsant and neuroprotective capacity. ► Physostigmine (PHY) was examined as an adjunct post-exposure therapy. ► PHY attenuated GD-induced seizure development, but not seizure duration.« less

Effect of centrifuge test on blood serum lipids index of cadet pilots.

PubMed

Wochyński, Zbigniew; Kowalczuk, Krzysztof; Kłossowski, Marek; Sobiech, Krzysztof A

2016-01-01

This study aimed at investigating the relationship between the lipid index (WS) in the examined cadets and duration of exposure to +Gz in the human centrifuge. The study involved 19 first-year cadets of the Polish Air Force Academy in Dęblin. Tests in the human centrifuge were repeated twice, i.e. prior to (test I) and 45 days after (test II). After exposure to +Gz, the examined cadets were divided into 2 groups. Group I (N=11) included cadets subjected to a shorter total duration of exposure to +Gz, while group II (N=8) included cadets with a longer total duration of exposure to +Gz. Total cholesterol (TC), high density lipoprotein (HDL), triglycerides (TG), and apolipoproteins A1 and B were assayed in blood serum prior to (assay A) and after (assay B) both exposures to +Gz. Low density lipoprotein (LDL) level was estimated from the Friedewald formula. WS is an own mathematical algorithm. WS was higher in group II, assay A - 10.0 and B - 10.08 of test I in the human centrifuge than in group I where the WS values were 6.91 and 6.96, respectively. WS was also higher in group II in assay A - 10.0 and B -10.1 of test II in the human centrifuge than in group I - 6.96 and 6.80, respectively. The higher value of WS in group II, both after the first and second exposure to +Gz in human centrifuge, in comparison with group I, indicated its usefulness for determination of the maximum capability of applying acceleration of the interval type during training in the human centrifuge.

Impact of exposure time, particle size and uptake pathway on silver nanoparticle effects on circulating immune cells in mytilus galloprovincialis.

PubMed

Bouallegui, Younes; Ben Younes, Ridha; Turki, Faten; Oueslati, Ridha

2017-12-01

Nanomaterials have increasingly emerged as potential pollutants to aquatic organisms. Nanomaterials are known to be taken up by hemocytes of marine invertebrates including Mytilus galloprovincialis. Indeed, assessments of hemocyte-related parameters are a valuable tool in the determination of potentials for nanoparticle (NP) toxicity. The present study assessed the effects from two size types of silver nanoparticles (AgNP: <50 nm and <100 nm) on the frequency of hemocytes subpopulations as immunomodulation biomarkers exposed in a mollusk host. Studies were performed using exposures prior to and after inhibition of potential NP uptake pathways (i.e. clathrin- and caveolae-mediated endocytosis) and over different durations of exposure (3, 6 and 12 h). Differential hemocyte counts (DHC) revealed significant variations in frequency of different immune cells in mussels exposed for 3 hr to either AgNP size. However, as exposure duration progressed cell levels were subsequently differentially altered depending on particle size (i.e. no significant effects after 3 h with larger AgNP). AgNP effects were also delayed/varied after blockade of either clathrin- or caveolae-mediated endocytosis. The results also noted significant negative correlations between changes in levels hyalinocytes and acidophils or in levels basophils and acidophils as a result of AgNP exposure. From these results, we concluded AgNP effects on mussels were size and duration of exposure dependent. This study highlighted how not only was NP size important, but that differing internalization mechanisms could be key factors impacting on the potential for NP in the environment to induce immunomodulation in a model/test sentinel host like M. galloprovincialis.

A Comparison of Robotically Assisted Microsurgery versus Manual Microsurgery in Challenging Situations.

PubMed

Willems, Joost I P; Shin, Alexandra M; Shin, Delaney M; Bishop, Allen T; Shin, Alexander Y

2016-04-01

Microsurgery can be challenging secondary to orientation of the vessels, accessibility, or depth of the wound. Robotically assisted microsurgery reduces tremors and improves visualization and may improve the quality of anastomosis compared with traditional microsurgery. The purpose of this study was to compare robotically assisted microsurgery to traditional microsurgery in technically challenging situations with respect to time of anastomosis, quality of anastomosis, and Objective Structured Assessment of Technical Skills. Two investigators with no prior surgery or microsurgery experience performed 160 anastomoses on artificial microvessels after undergoing standardized traditional and robotically assisted microsurgery courses. Five different exposure groups were created with depths of 0, 10, and 20 cm and sidewall angles of 20 and 30 degrees. A comparison of 80 manual with 80 robotically assisted microsurgery anastomoses in different exposure groups was undertaken. The modified Objective Structured Assessment of Technical Skills scoring system, duration per anastomosis, and a subjective comfort scale were evaluated. In the most difficult exposure, Objective Structured Assessment of Technical Skills scores were similar in both groups (p = 0.98), the duration was higher in the manual group (p = 0.004), and the subjective comfort rating was higher in the robotically assisted microsurgery group (p < 0.001). In the easiest (0-cm depth, flat) exposure, Objective Structured Assessment of Technical Skills scores were higher in the manual group (p = 0.018) and the duration was longer in the robotically assisted microsurgery group (p = 0.008). Manual surgery was superior to robotically assisted microsurgery in technically easy exposures. In difficult exposures (greater depth and lower sidewall angles), however, robotically assisted microsurgery had a shorter surgery time and a higher comfort rating, with Objective Structured Assessment of Technical Skills scores similar to those assessing traditional microsurgery. Therapeutic, V.

The effect of duration of exposure on sulfuric acid-induced pulmonary function changes in asthmatic adolescent subjects: A dose-response study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koenig, J.Q.; Covert, D.S.; Larson, T.V.

To evaluate the pulmonary effects of varying doses of sulfuric acid, adolescent subjects with asthma were exposed to 35 or 70 micrograms/m3 sulfuric acid for 45 or 90 min. Exposure was carried out during intermittent moderate exercise. The pulmonary functions measured before and after exposure were FEV1, FVC, and total respiratory resistance. The 45 min exposures were associated with larger decreases in FEV1 (-6% or -3%) than the 90 min exposures (-1% or +2%). Analysis of variance of the change in FEV1 among the exposures revealed that the 45 min exposure to 35 micrograms/m3 was significant (p = 0.03). Themore » p value for 45 min exposure to 70 micrograms/m3 was not significant (p = 0.08). Using analysis of variance, neither of the 90 min exposures was associated with a significant decrease in FEV1 compared to air exposure. Also, none of the changes in FVC or RT was significant. When baseline to post-exposure changes were compared for each of the five test atmospheres using paired t tests, both of the 45 min exposures were associated with statistical significance (p < 0.001 for 35 micrograms/m3 and p < 0.005 for 70 micrograms/m3). This baseline to post exposure change was not statistically significant for the 90 min exposures. The reason for the lesser effect on pulmonary function at increased exposure duration is not known; it may be due to changes in either varying deposition patterns or changes in buffering capacity of the cells lining the airways. With respect to individual sensitivities to H2SO4, the data showed a significant consistency across test atmospheres.« less

Fault tree analysis for exposure to refrigerants used for automotive air conditioning in the United States.

PubMed

Jetter, J J; Forte, R; Rubenstein, R

2001-02-01

A fault tree analysis was used to estimate the number of refrigerant exposures of automotive service technicians and vehicle occupants in the United States. Exposures of service technicians can occur when service equipment or automotive air-conditioning systems leak during servicing. The number of refrigerant exposures of service technicians was estimated to be 135,000 per year. Exposures of vehicle occupants can occur when refrigerant enters passenger compartments due to sudden leaks in air-conditioning systems, leaks following servicing, or leaks caused by collisions. The total number of exposures of vehicle occupants was estimated to be 3,600 per year. The largest number of exposures of vehicle occupants was estimated for leaks caused by collisions, and the second largest number of exposures was estimated for leaks following servicing. Estimates used in the fault tree analysis were based on a survey of automotive air-conditioning service shops, the best available data from the literature, and the engineering judgement of the authors and expert reviewers from the Society of Automotive Engineers Interior Climate Control Standards Committee. Exposure concentrations and durations were estimated and compared with toxicity data for refrigerants currently used in automotive air conditioners. Uncertainty was high for the estimated numbers of exposures, exposure concentrations, and exposure durations. Uncertainty could be reduced in the future by conducting more extensive surveys, measurements of refrigerant concentrations, and exposure monitoring. Nevertheless, the analysis indicated that the risk of exposure of service technicians and vehicle occupants is significant, and it is recommended that no refrigerant that is substantially more toxic than currently available substitutes be accepted for use in vehicle air-conditioning systems, absent a means of mitigating exposure.

[Opiate addiction in gravidity - consequences for the newborn. Results of an interdisciplinary treatment concept].

PubMed

Rohrmeister, K; Bernert, G; Langer, M; Fischer, G; Weninger, M; Pollak, A

2001-01-01

To evaluate the outcome of infants of drug dependent mothers (IDM) after establishing an interdisciplinary attention concept at the University Hospital in Vienna. To compare the influence of different maintenance agents on neonatal morbidity. All newborns of opiate dependent mothers were prospectively included from III 1995 to IX 1999. The following data were collected: maintenance agent (methadone, slow release morphine, buprenorphine), infectious status, demographic data, congenital malformations, perinatal complications, as well as incidence and duration of the neonatal abstinence syndrome (NAS). Medical treatment with phenobarbital (1995 - 96) or morphine hydrochloride (MoHCl) (1997 - 99), respectively, was indicated when Finnegan score exceeded 10. 88 neonates (38 females/50 males) with a median gestational age of 39 weeks were included, 18 (20.5 %) were born prematurely. The median birthweight was 2905 g, 24 (27.3 %) infants were small for date (< 10th percentile), 15 (17 %) microcephalic. The malformation incidence was 7.4 %. 63 (72 %) of all newborns had to be treated due to abstinence syndrome: in the methadone group 76 %, in the morphine group 93 %, but in the buprenorphine group 19 % only (p < 0.01). Median duration of withdrawal was 15.1 days (d) with significant difference after antenatal buprenorphine exposure compared to methadone and morphine exposure (8.3 d versus 15 d and 16.5 d respectively). In neonates treated with phenobarbital duration of NAS was 17.6 d, whereas NAS in infants with MoHCl therapy lasted 12.8 d (p < 0.05). Incidence and duration of NAS after buprenorphine exposure was significantly lower than after methadone and morphine exposure. Withdrawal time under morphin-hydrochloride therapy was reduced by one third compared to treatment with phenobarbital.

Do sanitary ceramic workers have a worse presentation of chest radiographs or pulmonary function tests than other ceramic workers?

PubMed

Tsao, Yu-Chung; Liu, Su-Hsun; Tzeng, I-Shiang; Hsieh, Tsung-Han; Chen, Jau-Yuan; Luo, Jiin-Chyuan John

2017-03-01

Silicosis remains the most prevalent occupational disease worldwide. There have been no specific studies focusing on the association between exposure settings at work and the clinical severity in silicosis patients. In this study, we describe and compare the clinical characteristics and silicosis-associated exposure history at work among workers from several types of ceramic production facilities in Taiwan. We reviewed the medical records of 221 patients who were first diagnosed with silicosis at the Occupational Medicine Clinic of Northern Taiwan in 2012. For each patient, we collected data on demographic characteristics, smoking habits, working history, duration of exposure, and years on the first relevant job. We also retrieved clinical reports of the pulmonary function test and the baseline chest radiography used for silicosis staging. As compared to other ceramic workers, sanitary ceramic workers had a worse X-ray type (p=0.044), more advanced age (p<0.001), longer working duration (p=0.029), and a higher proportion of starting the first relevant job prior to the year 1975 (p=0.003). However, after adjusting for age, work duration, and an initial occupational exposure prior to 1975, sanitary ceramic workers showed a comparable risk for worse X-ray findings to other ceramic workers (adjusted odds ratio=1.18, p=0.704). Results of multivariable regression models on individual lung function parameter also suggested comparably impaired lung function tests between sanitary and other ceramic workers (p>0.05). In this study, we found that sanitary ceramic workers were at a similar risk to other ceramic workers for moderate to severe silicosis when older age and longer working duration were accounted for. Copyright © 2016. Published by Elsevier B.V.

Exposure history determines pteropod vulnerability to ocean acidification along the US West Coast.

PubMed

Bednaršek, N; Feely, R A; Tolimieri, N; Hermann, A J; Siedlecki, S A; Waldbusser, G G; McElhany, P; Alin, S R; Klinger, T; Moore-Maley, B; Pörtner, H O

2017-07-03

The pteropod Limacina helicina frequently experiences seasonal exposure to corrosive conditions (Ω ar   < 1) along the US West Coast and is recognized as one of the species most susceptible to ocean acidification (OA). Yet, little is known about their capacity to acclimatize to such conditions. We collected pteropods in the California Current Ecosystem (CCE) that differed in the severity of exposure to Ω ar conditions in the natural environment. Combining field observations, high-CO 2 perturbation experiment results, and retrospective ocean transport simulations, we investigated biological responses based on histories of magnitude and duration of exposure to Ω ar  < 1. Our results suggest that both exposure magnitude and duration affect pteropod responses in the natural environment. However, observed declines in calcification performance and survival probability under high CO 2 experimental conditions do not show acclimatization capacity or physiological tolerance related to history of exposure to corrosive conditions. Pteropods from the coastal CCE appear to be at or near the limit of their physiological capacity, and consequently, are already at extinction risk under projected acceleration of OA over the next 30 years. Our results demonstrate that Ω ar exposure history largely determines pteropod response to experimental conditions and is essential to the interpretation of biological observations and experimental results.

Windows of sensitivity to toxic chemicals in the motor effects development.

PubMed

Ingber, Susan Z; Pohl, Hana R

2016-02-01

Many chemicals currently used are known to elicit nervous system effects. In addition, approximately 2000 new chemicals introduced annually have not yet undergone neurotoxicity testing. This review concentrated on motor development effects associated with exposure to environmental neurotoxicants to help identify critical windows of exposure and begin to assess data needs based on a subset of chemicals thoroughly reviewed by the Agency for Toxic Substances and Disease Registry (ATSDR) in Toxicological Profiles and Addenda. Multiple windows of sensitivity were identified that differed based on the maturity level of the neurological system at the time of exposure, as well as dose and exposure duration. Similar but distinct windows were found for both motor activity (GD 8-17 [rats], GD 12-14 and PND 3-10 [mice]) and motor function performance (insufficient data for rats, GD 12-17 [mice]). Identifying specific windows of sensitivity in animal studies was hampered by study designs oriented towards detection of neurotoxicity that occurred at any time throughout the developmental process. In conclusion, while this investigation identified some critical exposure windows for motor development effects, it demonstrates a need for more acute duration exposure studies based on neurodevelopmental windows, particularly during the exposure periods identified in this review. Published by Elsevier Inc.

Diesel exhaust, solvents, and other occupational exposures as risk factors for wheeze among farmers.

PubMed

Hoppin, Jane A; Umbach, David M; London, Stephanie J; Alavanja, Michael C R; Sandler, Dale P

2004-06-15

Farmers engage in activities that result in exposure to diesel exhaust, solvents, welding fumes, and other respiratory irritants. Using the Agricultural Health Study, a cohort of pesticide applicators in Iowa and North Carolina, we evaluated the odds of wheeze associated with nonpesticide occupational exposures. We used logistic regression models controlling for age, state, smoking, and history of asthma or atopy to evaluate odds of wheeze in the past year among the 20898 farmers who provided complete information on all covariates. Driving diesel tractors was associated with elevated odds of wheeze (odds ratio = 1.31; 95% confidence interval = 1.13, 1.52); the odds ratio for driving gasoline tractors was 1.11 (95% confidence interval = 1.02, 1.21). A duration-response relationship was observed for driving diesel tractors but not for driving gasoline tractors. Activities involving solvent exposure, including painting and use of solvents for cleaning, were associated with an increased odds of wheeze in a duration-dependent fashion. The highest odds of wheeze for farm activities were for daily painting (odds ratio = 1.82; 95% confidence interval = 0.89, 3.73), an indication of daily solvent exposure. These results add to the growing body of evidence of adverse respiratory effects of diesel exposure on the lung and suggest exposure to solvents may contribute as well.

Windows of sensitivity to toxic chemicals in the motor effects development✩

PubMed Central

Ingber, Susan Z.; Pohl, Hana R.

2017-01-01

Many chemicals currently used are known to elicit nervous system effects. In addition, approximately 2000 new chemicals introduced annually have not yet undergone neurotoxicity testing. This review concentrated on motor development effects associated with exposure to environmental neurotoxicants to help identify critical windows of exposure and begin to assess data needs based on a subset of chemicals thoroughly reviewed by the Agency for Toxic Substances and Disease Registry (ATSDR) in Toxicological Profiles and Addenda. Multiple windows of sensitivity were identified that differed based on the maturity level of the neurological system at the time of exposure, as well as dose and exposure duration. Similar but distinct windows were found for both motor activity (GD 8–17 [rats], GD 12–14 and PND 3–10 [mice]) and motor function performance (insufficient data for rats, GD 12–17 [mice]). Identifying specific windows of sensitivity in animal studies was hampered by study designs oriented towards detection of neurotoxicity that occurred at any time throughout the developmental process. In conclusion, while this investigation identified some critical exposure windows for motor development effects, it demonstrates a need for more acute duration exposure studies based on neurodevelopmental windows, particularly during the exposure periods identified in this review. PMID:26686904

Developmental Exposure to an Environmental PCB Mixture ...

EPA Pesticide Factsheets

Developmental PCB exposure impairs hearing and induces brainstem audiogenic seizures in adult offspring. The degree to which this enhanced susceptibility to seizure is manifest in other brain regions has not been examined. Thus, electrical kindling of the amygdala was used to evaluate the effect of developmental exposure to an environmentally relevant PCB mixture on seizure susceptibility in the rat. Female Long-Evans rats were dosed orally with 0 or 6 mg/kg/day of the PCB mixture dissolved in corn oil vehicle during the perinatal period. On postnatal day (PND) 21, pups were weaned, and two males from each litter were randomly selected for the kindling study. As adults, the male rats were implanted bilaterally with electrodes in the basolateral amygdala. For each animal, afterdischarge (AD) thresholds in the amygdala were determined on the first day of testing followed by once daily stimulation at a standard 200 µA stimulus intensity until three stage 5 generalized seizures (GS) ensued. Developmental PCB exposure did not affect the AD threshold or total cumulative AD duration, but PCB exposure did increase the latency to behavioral manifestations of seizure propagation. PCB exposed animals required significantly more stimulations to reach stage 2 seizures compared to control animals, indicating an attenuated focal (amygdala) excitability. A delay in kindling progression from a focally stimulated limbic site stands in contrast to our previous finding of increase

Silica exposure during construction activities: statistical modeling of task-based measurements from the literature.

PubMed

Sauvé, Jean-François; Beaudry, Charles; Bégin, Denis; Dion, Chantal; Gérin, Michel; Lavoué, Jérôme

2013-05-01

Many construction activities can put workers at risk of breathing silica containing dusts, and there is an important body of literature documenting exposure levels using a task-based strategy. In this study, statistical modeling was used to analyze a data set containing 1466 task-based, personal respirable crystalline silica (RCS) measurements gathered from 46 sources to estimate exposure levels during construction tasks and the effects of determinants of exposure. Monte-Carlo simulation was used to recreate individual exposures from summary parameters, and the statistical modeling involved multimodel inference with Tobit models containing combinations of the following exposure variables: sampling year, sampling duration, construction sector, project type, workspace, ventilation, and controls. Exposure levels by task were predicted based on the median reported duration by activity, the year 1998, absence of source control methods, and an equal distribution of the other determinants of exposure. The model containing all the variables explained 60% of the variability and was identified as the best approximating model. Of the 27 tasks contained in the data set, abrasive blasting, masonry chipping, scabbling concrete, tuck pointing, and tunnel boring had estimated geometric means above 0.1mg m(-3) based on the exposure scenario developed. Water-fed tools and local exhaust ventilation were associated with a reduction of 71 and 69% in exposure levels compared with no controls, respectively. The predictive model developed can be used to estimate RCS concentrations for many construction activities in a wide range of circumstances.

Timing and Duration of Traffic-related Air Pollution Exposure and the Risk for Childhood Wheeze and Asthma.

PubMed

Brunst, Kelly J; Ryan, Patrick H; Brokamp, Cole; Bernstein, David; Reponen, Tiina; Lockey, James; Khurana Hershey, Gurjit K; Levin, Linda; Grinshpun, Sergey A; LeMasters, Grace

2015-08-15

The timing and duration of traffic-related air pollution (TRAP) exposure may be important for childhood wheezing and asthma development. We examined the relationship between TRAP exposure and longitudinal wheezing phenotypes and asthma at age 7 years. Children completed clinical examinations annually from age 1 year through age 4 years and age 7 years. Parental-reported wheezing was assessed at each age, and longitudinal wheezing phenotypes (early-transient, late-onset, persistent) and asthma were defined at age 7 years. Participants' time-weighted exposure to TRAP, from birth through age 7 years, was estimated using a land-use regression model. The relationship between TRAP exposure and wheezing phenotypes and asthma was examined. High TRAP exposure at birth was significantly associated with both transient and persistent wheezing phenotypes (adjusted odds ratio [aOR] = 1.64; 95% confidence interval [CI], 1.04-2.57 and aOR = 2.31; 95% CI, 1.28-4.15, respectively); exposure from birth to age 1 year and age 1 to 2 years was also associated with persistent wheeze. Only children with high average TRAP exposure from birth through age 7 years were at significantly increased risk for asthma (aOR = 1.71; 95% CI, 1.01-2.88). Early-life exposure to TRAP is associated with increased risk for persistent wheezing, but only long-term exposure to high levels of TRAP throughout childhood was associated with asthma development.

Exposure assessment for trihalomethanes in municipal drinking water and risk reduction strategy.

PubMed

Chowdhury, Shakhawat

2013-10-01

Lifetime exposure to disinfection byproducts (DBPs) in municipal water may pose risks to human health. Current approaches of exposure assessments use DBPs in cold water during showering, while warming of chlorinated water during showering may increase trihalomethane (THM) formation in the presence of free residual chlorine. Further, DBP exposure through dermal contact during showering is estimated using steady-state condition between the DBPs in shower water impacting on human skin and skin exposed to shower water. The lag times to achieve steady-state condition between DBPs in shower water and human skin can vary in the range of 9.8-391.2 min, while shower duration is often less than the lag times. Assessment of exposure without incorporating these factors might have misinterpreted DBP exposure in some previous studies. In this study, exposure to THMs through ingestion was estimated using cold water THMs, while THM exposure through inhalation and dermal contact during showering was estimated using THMs in warm water. Inhalation of THMs was estimated using THM partition into the shower air, while dermal uptake was estimated by incorporating lag times (e.g., unsteady and steady-state phases of exposure) during showering. Probabilistic approach was followed to incorporate uncertainty in the assessment. Inhalation and dermal contact during showering contributed 25-60% of total exposure. Exposure to THMs during showering can be controlled by varying shower stall volume, shower duration and air exchange rate following power law equations. The findings might be useful in understanding exposure to THMs, which can be extended to other volatile compounds in municipal water. © 2013 Elsevier B.V. All rights reserved.

Occupational exposure to dioxins by thermal oxygen cutting, welding, and soldering of metals.

PubMed

Menzel, H M; Bolm-Audorff, U; Turcer, E; Bienfait, H G; Albracht, G; Walter, D; Emmel, C; Knecht, U; Päpke, O

1998-04-01

This paper focuses on one aspect of occupational dioxin exposure that is novel and unexpected. Exposures in excess of the German threshold limit value of 50 pg international toxicity equivalent (I-TEQ)/m3 are very frequent, unpredictable, and sometimes very high--up to 6612 pg I-TEQ/m3--during thermal oxygen cutting at scrap metal and demolition sites. The same procedure involving virgin steel in steel trade and mass production of steel objects gave no such evidence, even though no final conclusions can be drawn because of the low number of samples analyzed. Low dioxin exposures during inert gas electric arc welding confirm previous literature findings, whereas soldering and thermal oxygen cutting in the presence of polyvinyl chloride give rise to concern. The consequences of occupational dioxin exposure were studied by analysis of the dioxin-blood concentration, the body burden, of men performing thermal oxygen cutting at scrap metal reclamation and demolition sites, in steel trade and producing plants as well as for industrial welders and white-collar workers. The results concerning body burdens are in excellent agreement with the dioxin exposure as characterized by dioxin air concentration in the workplace. The significant positive correlation between duration and frequency of performing thermal oxygen cutting at metal reclamation and demolition sites expressed in job-years and dioxin body burden speaks for the occupational origin of the observed overload after long times. The results reported here lead to consequences for occupational health, which are discussed and require immediate attention.

Status: Crewmember Noise Exposures on the International Space Station

NASA Technical Reports Server (NTRS)

Limardo-Rodriguez, Jose G.; Allen, Christopher S.; Danielson, Richard W.

2015-01-01

The International Space Station (ISS) provides a unique environment where crewmembers from the US and our international partners work and live for as long as 6 to 12 consecutive months. During these long-durations ISS missions, noise exposures from onboard equipment are posing concerns for human factors and crewmember health risks, such as possible reductions in hearing sensitivity, disruptions of crew sleep, interference with speech intelligibility and voice communications, interference with crew task performance, and reduced alarm audibility. It is crucial to control acoustical noise aboard ISS to acceptable noise exposure levels during the work-time period, and to also provide a restful sleep environment during the sleep-time period. Acoustic dosimeter measurements, obtained when the crewmember wears the dosimeter for 24-hour periods, are conducted onboard ISS every 60 days and compared to ISS flight rules. NASA personnel then assess the acoustic environment to which the crewmembers are exposed, and provide recommendations for hearing protection device usage. The purpose of this paper is to provide an update on the status of ISS noise exposure monitoring and hearing conservation strategies, as well as to summarize assessments of acoustic dosimeter data collected since the Increment 36 mission (April 2013). A description of the updated noise level constraints flight rule, as well as the Noise Exposure Estimation Tool and the Noise Hazard Inventory implementation for predicting crew noise exposures and recommending to ISS crewmembers when hearing protection devices are required, will be described.

Incidence of laryngeal cancer and exposure to acid mists.

PubMed Central

Steenland, K; Schnorr, T; Beaumont, J; Halperin, W; Bloom, T

1988-01-01

To determine the relation between exposure to acid mist and laryngeal cancer, the smoking habits, drinking habits, and incidence of laryngeal cancer of 879 male steelworkers exposed to acid mists during pickling operations was ascertained. Sulphuric acid mist was the primary exposure for most men in this cohort. These men had all worked in a pickling operation for a minimum of six months before 1965, with an average duration of exposure of 9.5 years. Exposures to sulphuric acid in the 1970s averaged about 0.2 mg/m3, and earlier exposures were probably similar. Interviews were conducted with all cohort members or their next of kin in 1986 and medical records of decedents were reviewed. Nine workers were identified who had been diagnosed as having laryngeal cancer, using a conservative case definition that required medical record confirmation for any case among decedents and confirmation by a physician for any case among live individuals. Using data from national surveys of cancer incidence as referent rates, 3.44 laryngeal cancers would have been expected. Excess smoking by the exposed cohort compared with the United States population resulted in an upward adjustment of the expected number of cases of laryngeal cancer to 3.92. The standardised incidence rate ratio for laryngeal cancer was 2.30 (9/3.92), with a one sided p value of 0.01 (assuming a Poisson distribution). The finding of excess laryngeal cancer in this cohort is consistent with four other studies published since 1981. PMID:3203082

Method for flow cytometric monitoring of Renibacterium salmoninarum inactivation

USGS Publications Warehouse

Pascho, R.J.; Ongerth, J.E.

2000-01-01

The slow growth of Renibacterium salmoninarum limits the usefulness of culture as a research tool. Development of a 2-color flow cytometric assay to quantify the proportions of live and dead R. salmoninarum in a test population is described. Bacteria were simultaneously stained with fluorescein isothiocyanate-conjugated immunoglobulin and exposed to the exclusion dye propidium iodide. Propidium iodide red fluorescence profiles of control groups of untreated and killed R. salmoninarum were compared with those for bacteria exposed to chlorine. Bacterial inactivation was based on mean red fluorescence intensity, and analyzed by high-red fluorescence intensity (HRFI) and curve subtraction (CS) analyses. When the concentration of R. salmoninarum was 8.65 x 106 bacteria ml-1 and the bacteria exposed to chlorine at 1 mg l-1 for periods from 1 to 20 min (high-Rs assessment), the mean red fluorescence intensity of the profile for each chlorine-exposure group was higher than that for the untreated control (p < 0.0001). When the concentration of R. salmoninarum was reduced to 1.76 x 106 bacteria ml-1 and exposed to 0.8 mg l-1 free chlorine level for periods from 20 s to 5 min (reduced-Rs assessment), the mean red fluorescence intensities of the exposure groups were higher than that for the untreated control only when the R. salmoninarum was exposed to chlorine for at least 1 min (p ??? 0.01). On the basis of red fluorescence intensity, the proportion of dead cells generally increased with the duration of chlorine exposure. Whereas the rates of inactivation derived from the HRFI and CS analyses did not correlate with the duration of exposure in the high-Rs assessment (r2 ??? 0.27), there was a correlation between these estimates and the duration of exposure in the reduced-Rs assessment (r2 ??? 0.92). Because of the rapid loss of culturable R. salmoninarum in both assessments following chlorine exposure, neither the duration of exposure nor the inactivation estimates correlated with bacteriological culture (r2 ??? 0.22). In both assessments, there was a correlation between the estimates of inactivation based upon HRFI and CS analyses (r2 > 0.99). These results suggest that flow cytometry can be used as a supplementary or alternative method to bacteriological culture for monitoring the inactivation of R. salmoninarum.

AN OBSERVATIONAL STUDY: DETERMINATION OF THE VOLUME OF WATER INGESTED DURING RECREATIONAL SWIMMING ACTIVITIES

EPA Science Inventory

EPA's Action Plan for Beaches and Recreational Waters describes research needs for exposure assessment related to swimming activities such as characterizing swimming populations with regard to routes and magnitudes of exposure. This includes characteristics such as the duration ...

Application of in Vitro Biotransformation Data and Pharmacokinetic Modeling to Risk Assessment

EPA Science Inventory

The adverse biological effects of toxic substances are dependent upon the exposure concentration and the duration of exposure. Pharmacokinetic models can quantitatively relate the external concentration of a toxicant in the environment to the internal dose of the toxicant in the ...

Mere Exposure, Psychological Reactance and Attitude Change

ERIC Educational Resources Information Center

Miller, Richard

1976-01-01

Concludes that exposure of a persuasive message should ideally be of sufficient duration to familiarize the target population, but not too great to cause a "boomerang" effect; when overexposure and/or boomerang effect occurs, a period of nonexposure can sufficiently reduce any overexposure effects. (RL)

Hair cell counts in a rat model of sound damage: Effects of tissue preparation & identification of regions of hair cell loss.

PubMed

Neal, Christopher; Kennon-McGill, Stefanie; Freemyer, Andrea; Shum, Axel; Staecker, Hinrich; Durham, Dianne

2015-10-01

Exposure to intense sound can damage or kill cochlear hair cells (HC). This loss of input typically manifests as noise induced hearing loss, but it can also be involved in the initiation of other auditory disorders such as tinnitus or hyperacusis. In this study we quantify changes in HC number following exposure to one of four sound damage paradigms. We exposed adult, anesthetized Long-Evans rats to a unilateral 16 kHz pure tone that varied in intensity (114 dB or 118 dB) and duration (1, 2, or 4 h) and sacrificed animals 2-4 weeks later. We compared two different methods of tissue preparation, plastic embedding/sectioning and whole mount dissection, for quantifying hair cell loss as a function of frequency. We found that the two methods of tissue preparation produced largely comparable cochleograms, with whole mount dissections allowing a more rapid evaluation of hair cell number. Both inner and outer hair cell loss was observed throughout the length of the cochlea irrespective of sound damage paradigm. Inner HC loss was either equal to or greater than outer HC loss. Increasing the duration of sound exposures resulted in more severe HC loss, which included all HC lesions observed in an analogous shorter duration exposure. Copyright © 2015 Elsevier B.V. All rights reserved.

Some Behavioral Effects of Exposure to Low Doses of Fe-56 Particles

NASA Technical Reports Server (NTRS)

Rabin, Bernard M.; Joseph, James A.; Shukitt-Hale, Barbara

1999-01-01

Future missions in space (such as a mission to Mars) will involve long-term travel beyond the magnetic field of the Earth. As a result, astronauts will be exposed to radiation qualities and doses that differ from those experienced in low earth orbit, including exposure to heavy particles, such as Fe-56, which are a component of cosmic rays. Although the hazards of exposure to heavy particles are often minimized, they can affect neural functioning, and as a consequence, behavior. Unless the effects of exposure to cosmic rays can somehow be reduced, their effects on the brain throughout long duration flights could be disastrous. In the extreme case, it is possible that the effects of cosmic rays on space travelers could result in symptomatology resembling that of Alzheimer's or Parkinson's diseases or of advancing age, including significant cognitive and/or motor impairments. Because successful operations in space depend in part on the performance capabilities of astronauts, such impairments could jeopardize their ability to satisfy mission requirements, as well as have long-term consequences on the health of astronauts. As such, understanding the nature and extent of this risk may be vital to the effective performance and possibly the survival of astronauts during future missions in space.

A historical overview of the development of manganese (Mn) ...

EPA Pesticide Factsheets

Abstract for Manganese 2016A historical overview of the development of manganese (Mn) pharmacokinetic data under Section 211(b) of the Clean Air Act (CAA)William K BoyesBackground. In the 1990’s, the use of methylcyclopentadienyl manganese tricarbonyl (MMT) as an octane-enhancing gasoline fuel additive led to concerns for potential public health consequences from exposure to Mn combustion products in automotive exhaust. Methods: After a series of regulatory / legal actions and negotiations, the EPA issued under CAA 211(b) an Alternative Tier 2 Test Rule that required development of scientific information intended to help resolve uncertainties in exposure or health risk estimates associated with MMT use. Among the uncertainties identified were: the chemical forms of Mn emitted in automotive exhaust; the relative toxicity of different Mn species; the potential for sensitive subpopulations including females, the young and elderly; differences in sensitivity between test species and humans; differences between inhalation and oral exposures; and the influence of dose rate and exposure duration on tissue accumulation of Mn. It was determined that development of specific sets of pharmacokinetic information and models regarding Mn could help resolve much of the uncertainties identified. Results. The results of the test program included development of several unique Mn PK datasets, and a series of increasingly sophisticated Mn physiologically-based pharmacokinetic

Total Dose Effects (TDE) of heavy ionizing radiation in fungus spores and plant seeds: Preliminary investigations

NASA Technical Reports Server (NTRS)

Kranz, A. R.; Zimmermann, M. W.; Stadler, R.; Gartenbach, K. E.; Pickert, M.

1992-01-01

The opportunity to compare cosmic radiation effects caused during long and short duration exposure flights in biological objects are limited until now, and data obtained so far are very rare and insufficient. Because of the very long exposure of the experiment during the Long Duration Exposure Facility (LDEF) mission (approximately 2000 days) structural changes of the hardware material can be expected which will influence its biocompatibility and, thus, will interact with the radiobiological effects. The aim of the experiment flown on LDEF was a detailed investigation of biological effects caused by cosmic radiation especially of particles of high atomic number Z and high energy. The flight hardware consisted of standard BIOSTACK containers; in these containers a special sandwich construction consisted of visual plastic detectors with seed rsp. spore layers interlocked.

Analysis of systems hardware flown on LDEF: New findings and comparison to other retrieved spacecraft hardware

NASA Technical Reports Server (NTRS)

Dursch, Harry; Bohnhoff-Hlavacek, Gail; Blue, Donald; Hansen, Patricia

1995-01-01

The Long Duration Exposure Facility (LDEF) was retrieved in 1990 after spending 69 months in low-earth-orbit (LEO). A wide variety of mechanical, electrical, thermal, and optical systems, subsystems, and components were flown on LDEF. The Systems Special Investigation Group (Systems SIG) was formed by NASA to investigate the effects of the 69 month exposure on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. This report is the Systems SIG final report which updates earlier findings and compares LDEF systems findings to results from other retrieved spacecraft hardware such as Hubble Space Telescope. Also included are sections titled (1) Effects of Long Duration Space Exposure on Optical Scatter, (2) Contamination Survey of LDEF, and (3) Degradation of Optical Materials in Space.

Analysis of systems hardware flown on LDEF: New findings and comparison to other retrieved spacecraft hardware

NASA Astrophysics Data System (ADS)

Dursch, Harry; Bohnhoff-Hlavacek, Gail; Blue, Donald; Hansen, Patricia

1995-09-01

The Long Duration Exposure Facility (LDEF) was retrieved in 1990 after spending 69 months in low-earth-orbit (LEO). A wide variety of mechanical, electrical, thermal, and optical systems, subsystems, and components were flown on LDEF. The Systems Special Investigation Group (Systems SIG) was formed by NASA to investigate the effects of the 69 month exposure on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. This report is the Systems SIG final report which updates earlier findings and compares LDEF systems findings to results from other retrieved spacecraft hardware such as Hubble Space Telescope. Also included are sections titled (1) Effects of Long Duration Space Exposure on Optical Scatter, (2) Contamination Survey of LDEF, and (3) Degradation of Optical Materials in Space.

The performance of thermal control coatings on LDEF and implications to future spacecraft

NASA Technical Reports Server (NTRS)

Wilkes, Donald R.; Miller, Edgar R.; Mell, Richard J.; Lemaster, Paul S.; Zwiener, James M.

1993-01-01

The stability of thermal control coatings over the lifetime of a satellite or space platform is crucial to the success of the mission. With the increasing size, complexity, and duration of future missions, the stability of these materials becomes even more important. The Long Duration Exposure Facility (LDEF) offered an excellent testbed to study the stability and interaction of thermal control coatings in the low-Earth orbit (LEO) space environment. Several experiments on LDEF exposed thermal control coatings to the space environment. This paper provides an overview of the different materials flown and their stability during the extended LDEF mission. The exposure conditions, exposure environment, and measurements of materials properties (both in-space and postflight) are described. The relevance of the results and the implications to the design and operation of future space vehicles are also discussed.

Utility of controlled human exposure studies for assessing the health effects of complex mixtures and indoor air pollutants.

PubMed Central

McDonnell, W F

1993-01-01

The study of health effects induced by exposure to mixtures of pollutants is a complex task. The purpose of this paper is to identify areas of research in which the conduct of human controlled exposure (clinical) studies may contribute to better understanding health effects of exposure to indoor air and other mixtures. The strengths and weaknesses of clinical studies in general are reviewed, as well as examples from the literature of approaches that have been used. Human chamber studies play an important role alongside epidemiologic and animal toxicologic studies in such research. Human chamber studies are limited with regard to assessing chronic effects, rare effects, or effects from long-duration exposures but are powerful in assessing acute, reversible effects from short-duration exposures in humans. The areas in which human chamber studies are most likely to contribute include identification of effects or markers of effects for exposure to a given pollutant or mix of pollutants; direct dose-response assessment of effects for individual compounds and mixtures of set composition; identification of individual compounds responsible for the effects of a mixture; study of the joint effects of a binary mixture; development of markers of acute exposure for particular compounds; development of outcome measurements to be used in the field; and identification, characterization, and testing of sensitive subpopulations. PMID:8206031

Declining Pulmonary Function in Populations with Long-term Exposure to Polycyclic Aromatic Hydrocarbons-Enriched PM2.5.

PubMed

Shen, Meili; Xing, Jie; Ji, Qianpeng; Li, Zhihui; Wang, Yanhua; Zhao, Hongwei; Wang, Qingrong; Wang, Ting; Yu, Liwei; Zhang, Xiuchuan; Sun, Yaxin; Zhang, Zhihu; Niu, Yong; Wang, Huanqiang; Chen, Wen; Dai, Yufei; Su, Wenge; Duan, Huawei

2018-06-05

This study assesses the effects of long-term exposure to ambient air pollutants on inflammatory response and lung function. We selected 390 male coke oven workers with exposure to polycyclic aromatic hydrocarbons (PAHs) and fine particulate matter (PM 2.5 ) and 115 control workers. The average duration in the exposed group was 9.10 years. The total amount of PAHs was more enriched in PM 2.5 which collected from the coke oven workshops compared with the control areas. Correspondingly, the internal PAHs exposure indicated by urinary 1-hydroxypyrene (1-OHP) in the exposure group increased 25.7-fold compared to that of the control group. Moreover, the increasing level of urinary 1-OHP was associated with the decrease of forced expiratory volume in 1 s to forced vital capacity ratio (FEV 1 /FVC). In non-current smokers of exposure group, inverse correlation of 1-OHP with FEV 1 /FVC was also found. Particularly, an exposure duration-dependent decline in FEV 1 /FVC and mean forced expiratory flow between 25% and 75% of forced vital capacity (FEF 25-75% ) indicated that small airways were functionally obstructed. Furthermore, the increasing serum high-sensitivity C-reactive protein (hs-CRP) was correlated with the decline in pulmonary function in all subjects. These findings provide a clue that long-term exposure to PAHs-enriched PM 2.5 impairs pulmonary function in occupational population.

Reestablishment of ion homeostasis during chill-coma recovery in the cricket Gryllus pennsylvanicus

PubMed Central

MacMillan, Heath A.; Williams, Caroline M.; Staples, James F.; Sinclair, Brent J.

2012-01-01

The time required to recover from cold-induced paralysis (chill-coma) is a common measure of insect cold tolerance used to test central questions in thermal biology and predict the effects of climate change on insect populations. The onset of chill-coma in the fall field cricket (Gryllus pennsylvanicus, Orthoptera: Gryllidae) is accompanied by a progressive drift of Na+ and water from the hemolymph to the gut, but the physiological mechanisms underlying recovery from chill-coma are not understood for any insect. Using a combination of gravimetric methods and atomic absorption spectroscopy, we demonstrate that recovery from chill-coma involves a reestablishment of hemolymph ion content and volume driven by removal of Na+ and water from the gut. Recovery is associated with a transient elevation of metabolic rate, the time span of which increases with increasing cold exposure duration and closely matches the duration of complete osmotic recovery. Thus, complete recovery from chill-coma is metabolically costly and encompasses a longer period than is required for the recovery of muscle potentials and movement. These findings provide evidence that physiological mechanisms of hemolymph ion content and volume regulation, such as ion-motive ATPase activity, are instrumental in chill-coma recovery and may underlie natural variation in insect cold tolerance. PMID:23184963

The Critical Path Roadmap Project: Biomedical Risk Reduction for Extended Spaceflight

NASA Technical Reports Server (NTRS)

Charles, John B.; Leveton, Lauren B.

2000-01-01

Human exploration of space requires an understanding of the risks to which crews will be exposed during such missions, and the mitigation of those risks to the fullest extent practical. This becomes a greater imperative as we prepare for interplanetary expeditions involving long periods in weightlessness in transit to and then from the destination (a planet, such as Mars, or perhaps a point in space, such as the Lagrangian point L2), and exposure to the unique environment of the destination itself. We need to know, more definitively, what the risks are to human health, safety, and performance, and how to prevent or counteract them throughout all phases of a long duration mission. The Johnson Space Center's Space and Life Sciences Directorate and the National Space Biomedical Research Institute (NSBRI) have implemented an effort to identify the most critical risks confronting humans on such mission and the types of research and technology efforts required to mitigate and otherwise reduce the probability and severity of those risks. This paper describes the "Critical Path Roadmap Project" to define, assess and prioritize the risks and present the results of the assessment with an emphasis on the research and technology priorities to meet the challenge of long duration human spaceflight mission.

Characterization of Plasma-Induced Damage of Selectively Recessed GaN/InAlN/AlN/GaN Heterostructures Using SiCl4 and SF6

NASA Astrophysics Data System (ADS)

Ostermaier, Clemens; Pozzovivo, Gianmauro; Basnar, Bernhard; Schrenk, Werner; Carlin, Jean-François; Gonschorek, Marcus; Grandjean, Nicolas; Vincze, Andrej; Tóth, Lajos; Pécz, Bela; Strasser, Gottfried; Pogany, Dionyz; Kuzmik, Jan

2010-11-01

We have investigated an inductively coupled plasma etching recipe using SiCl4 and SF6 with a resulting selectivity >10 for GaN in respect to InAlN. The formation of an etch-resistant layer of AlF3 on InAlN required about 1 min and was noticed by a 4-times-higher initial etch rate on bare InAlN barrier high electron mobility transistors (HEMTs). Comparing devices with and without plasma-treatment below the gate showed no degradation in drain current and gate leakage current for plasma exposure durations shorter than 30 s, indicating no plasma-induced damage of the InAlN barrier. Devices etched longer than the required time for the formation of the etch-resistant barrier exhibited a slight decrease in drain current and an increase in gate leakage current which saturated for longer etching-time durations. Finally, we could prove the quality of the recipe by recessing the highly doped 6 nm GaN cap layer of a GaN/InAlN/AlN/GaN heterostructure down to the 2 nm thin InAlN/AlN barrier layer.

Results of the TTF-TCNQ and the calcium carbonate crystallization on the Long Duration Exposure Facility

NASA Technical Reports Server (NTRS)

Nielsen, Kjeld Flemming; Lind, M. David

1992-01-01

Experiment A0139A on the Long Duration Exposure Facility (LDEF) carried four large containers into orbit five years with crystal growth solutions for lead sulfide, calcium carbonate, and TTF-TCNQ. Although temperature data was lost, the experimental program had been working since the valves in all containers had been opened. All four experiments produced crystals of varying quality. The calcium carbonate crystals had the best appearance. The TTF-TCNQ crystals were packed together near the valve openings of the container. When taken apart, the single crystals showed some unusual morphological properties. X ray investigations as well as conductivity measurements on long duration space grown TTF-TCNQ crystals will be presented. Comparisons will be made with our previous space solution growth experiments. The TTF-TCNQ crystals are no longer of the highest interest, so this activity has been terminated in favor of calcium carbonate and calcium phosphate crystallizations.

Permeabilization of the nuclear envelope following nanosecond pulsed electric field exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, Gary L., E-mail: gary.l.thompson.3@gmail.com; Roth, Caleb C.; Kuipers, Marjorie A.

2016-01-29

Permeabilization of cell membranes occurs upon exposure to a threshold absorbed dose (AD) of nanosecond pulsed electric fields (nsPEF). The ultimate, physiological bioeffect of this exposure depends on the type of cultured cell and environment, indicating that cell-specific pathways and structures are stimulated. Here we investigate 10 and 600 ns duration PEF effects on Chinese hamster ovary (CHO) cell nuclei, where our hypothesis is that pulse disruption of the nuclear envelope membrane leads to observed cell death and decreased viability 24 h post-exposure. To observe short-term responses to nsPEF exposure, CHO cells have been stably transfected with two fluorescently-labeled proteins known tomore » be sequestered for cellular chromosomal function within the nucleus – histone-2b (H2B) and proliferating cell nuclear antigen (PCNA). H2B remains associated with chromatin after nsPEF exposure, whereas PCNA leaks out of nuclei permeabilized by a threshold AD of 10 and 600 ns PEF. A downturn in 24 h viability, measured by MTT assay, is observed at the number of pulses required to induce permeabilization of the nucleus. - Highlights: • The ability of nsPEF to damage nuclear structures within cells is investigated. • Leakage of proliferating nuclear antigen from nuclei is induced by nsPEF. • High doses of nsPEF disrupt cortical lamin and cause chromatin decompaction. • Histone H2B remains attached to chromatin following nsPEF exposure. • DNA does not leak out of nsPEF-permeabilized nuclei.« less

Dietary exposure to chemicals within the process of risk assessment: possible applications to substances that may cause allergic reactions.

PubMed

Arcella, D; Le Donne, C; Leclercq, C

2005-11-01

Exposure assessment is one of the key parts of the risk assessment process. This task is crucial when evaluating substances for which only intake of toxicologically-important amounts can lead to adverse health effects. Ideally, dietary exposure to hazardous substances can be assessed by combining data on concentration in all food products with data on their consumption. However, it is considered to be neither cost-effective nor necessary to collect detailed data for every substance, and a stepwise procedure is commonly used to focus resources on the most important issues. Screening methods, designed to look for 'worst case' situations, are first used to target chemicals that might be of health concern for the general population or for certain at-risk groups. The quality of the dietary exposure assessments not only depends on the quality of the data collected, but also on the integration tools used for initial screening or for the eventual more precise estimations. A particular challenge is the evaluation of food allergens and components causing other forms of intolerances, since no reliable data seem to be currently available on the type of exposure (amounts and duration) required to induce a food allergy. A different approach from that used for dietary exposure to other hazardous substances has to be adopted. However, the methodologies (such as those used to collect food consumption data) and databases (in particular, information about food labels) developed in such a context could be useful to investigate the exposure conditions leading to the development of food allergies.

Long Duration Exposure Facility (LDEF) attitude measurements of the Interplanetary Dust Experiment

NASA Technical Reports Server (NTRS)

Kassel, Philip C., Jr.; Motley, William R., III; Singer, S. Fred; Mulholland, J. Derral; Oliver, John P.; Weinberg, Jerry L.; Cooke, William J.; Wortman, Jim J.

1993-01-01

Analysis of the data from the Long Duration Exposure Facility (LDEF) Interplanetary Dust Experiment (IDE) sun sensors has allowed a confirmation of the attitude of LDEF during its first year in orbit. Eight observations of the yaw angle at specific times were made and are tabulated in this paper. These values range from 4.3 to 12.4 deg with maximum uncertainty of plus or minus 2.0 deg and an average of 7.9 deg. No specific measurements of pitch or roll were made but the data indicates that LDEF had an average pitch down attitude of less than 0.7 deg.

Disinfection effect of non-thermal atmospheric pressure plasma for foodborne bacteria

NASA Astrophysics Data System (ADS)

Pervez, Mohammad Rasel; Inomata, Takanori; Ishijima, Tatsuo; Kakikawa, Makiko; Uesugi, Yoshihiko; Tanaka, Yasunori; Yano, Toshihiro; Miwa, Shoji; Noguchi, Akinori

2015-09-01

Non-thermal atmospheric pressure plasma (NAPP) exposure can be a suitable alternative for bacteria inactivation in food processing industry. Specimen placed in the enclosure are exposed to various reactive radicals produced within the discharge chamber. It is also exposed to the periodic variation of the electric field strength in the chamber. Dielectric barrier discharge is produced by high voltage pulse (Vpp = 18 kV, pulse width 20 μs, repetition frequency 10 kHz) in a polypropylene box (volume = 350 cm3) using helium as main feed gas. Inactivation efficiency of NAPP depends on the duration of NAPP exposure, applied voltage pulse strength and type, pulse duration, electrode separation and feed gas composition. In this study we have investigated inactivation of Bacillus lichenformis spore as an example of food borne bacteria. Keeping applied voltage, electrode configuration and total gas flow rate constant, spores are exposed to direct NAPP for different time duration while O2 concentration in the feed gas composition is varied. 10 minutes NAPP exposure resulted in ~ 3 log reduction of Bacillus lichenformis spores for 1% O2concentration (initial concentration ~ 106 / specimen). This work is supported by research and development promotion grant provided by the Hokuriku Industrial Advancement Center.

Colour changes in Labeo rohita (Ham.) due to pigment translocation in melanophores, on exposure to municipal wastewater of Tung Dhab drain, Amritsar, India.

PubMed

Kaur, Rajbir; Dua, Anish

2015-03-01

The present study was aimed to evaluate the effect of municipal wastewater of Tung Dhab drain on morphology of scale melanophores in freshwater fish Labeo rohita (Ham.). Chronic, non-renewal toxicity tests were performed with sub lethal concentrations (17.7, 26.6 and 35.4%) of wastewater for exposure durations of 15, 30 and 60 days. Recovery experiments were also performed for duration of 60 days. The scales were removed, processed and diameters of melanophores were measured using an ocular micrometer. The results showed concentration and duration dependent changes in melanophore morphology (size and dendricity) in experimental fish as compared to control fish. The values of mean melanophore size index (MMSI) varied from 5.37 ± 0.49 (17.7%) to 12.12 ± 0.81 (35.5%) in comparison to control values of 4.32 ± 0.32 and 4.55 ± 0.29 for 15 and 60 days respectively. The recovery experiments suggested that observed dark colouration due to pigment translocation is reversible, even after chronic exposure for 60 days. Copyright © 2015 Elsevier B.V. All rights reserved.

Plasma Membrane Permeabilization by 60- and 600-ns Electric Pulses Is Determined by the Absorbed Dose

PubMed Central

Ibey, Bennett L.; Xiao, Shu; Schoenbach, Karl H.; Murphy, Michael R.; Pakhomov, Andrei G.

2008-01-01

We explored how the effect of plasma membrane permeabilization by nanosecond-duration electric pulses (nsEP) depends on the physical characteristics of exposure. The resting membrane resistance (Rm) and membrane potential (MP) were measured in cultured GH3 and CHO cells by conventional whole-cell patch-clamp technique. Intact cells were exposed to a single nsEP (60 or 600 ns duration, 0-22 kV/cm), followed by patch-clamp measurements after a 2-3 min delay. Consistent with earlier findings, nsEP caused long-lasting Rm decrease, accompanied by the loss of MP. The threshold for these effects was about 6 kV/cm for 60 ns pulses, and about 1 kV/cm for 600 ns pulses. Further analysis established that it was neither pulse duration nor the E-field amplitude per se, but the absorbed dose that determined the magnitude of the biological effect. In other words, exposure to nsEP at either pulse duration caused equal effects if the absorbed doses were equal. The threshold absorbed dose to produce plasma membrane effects in either GH3 or CHO cells at either pulse duration was found to be at or below 10 mJ/g. Despite being determined by the dose, the nsEP effect clearly is not thermal, as the maximum heating at the threshold dose is less than 0.01 °C. The use of the absorbed dose as a universal exposure metric may help to compare and quantify nsEP sensitivity of different cell types and of cells in different physiological conditions. The absorbed dose may also prove to be a more useful metric than the incident E-field in determining safety limits for high peak, lowaverage power EMF emissions. PMID:18839412

Light-Induced Changes of the Circadian Clock of Humans: Increasing Duration is More Effective than Increasing Light Intensity

PubMed Central

Dewan, Karuna; Benloucif, Susan; Reid, Kathryn; Wolfe, Lisa F.; Zee, Phyllis C.

2011-01-01

Study Objectives: To evaluate the effect of increasing the intensity and/or duration of exposure on light-induced changes in the timing of the circadian clock of humans. Design: Multifactorial randomized controlled trial, between and within subject design Setting: General Clinical Research Center (GCRC) of an academic medical center Participants: 56 healthy young subjects (20-40 years of age) Interventions: Research subjects were admitted for 2 independent stays of 4 nights/3 days for treatment with bright or dim-light (randomized order) at a time known to induce phase delays in circadian timing. The intensity and duration of the bright light were determined by random assignment to one of 9 treatment conditions (duration of 1, 2, or 3 hours at 2000, 4000, or 8000 lux). Measurements and Results: Treatment-induced changes in the dim light melatonin onset (DLMO) and dim light melatonin offset (DLMOff) were measured from blood samples collected every 20-30 min throughout baseline and post-treatment nights. Comparison by multi-factor analysis of variance (ANOVA) of light-induced changes in the time of the circadian melatonin rhythm for the 9 conditions revealed that changing the duration of the light exposure from 1 to 3 h increased the magnitude of light-induced delays. In contrast, increasing from moderate (2,000 lux) to high (8,000 lux) intensity light did not alter the magnitude of phase delays of the circadian melatonin rhythm. Conclusions: Results from the present study suggest that for phototherapy of circadian rhythm sleep disorders in humans, a longer period of moderate intensity light may be more effective than a shorter exposure period of high intensity light. Citation: Dewan K; Benloucif S; Reid K; Wolfe LF; Zee PC. Light-induced changes of the circadian clock of humans: increasing duration is more effective than increasing light intensity. SLEEP 2011;34(5):593-599. PMID:21532952

Exponential increase in postprandial blood-glucose exposure with increasing carbohydrate loads using a linear carbohydrate-to-insulin ratio.

PubMed

Marran, K J; Davey, B; Lang, A; Segal, D G

2013-04-10

Postprandial glucose excursions contribute significantly to average blood glucose, glycaemic variability and cardiovascular risk. Carbohydrate counting is a method of insulin dosing that balances carbohydrate load to insulin dose using a fixed ratio. Many patients and current insulin pumps calculate insulin delivery for meals based on a linear carbohydrate-to-insulin relationship. It is our hypothesis that a non-linear relationship exists between the amounts of carbohydrate consumed and the insulin required to cover it. To document blood glucose exposure in response to increasing carbohydrate loads on fixed carbohydrate-to-insulin ratios. Five type 1 diabetic subjects receiving insulin pump therapy with good control were recruited. Morning basal rates and carbohydrate- to-insulin ratios were optimised. A Medtronic glucose sensor was used for 5 days to collect data for area-under-the-curve (AUC) analysis, during which standardised meals of increasing carbohydrate loads were consumed. Increasing carbohydrate loads using a fixed carbohydrate-to-insulin ratio resulted in increasing glucose AUC. The relationship was found to be exponential rather than linear. Late postprandial hypoglycaemia followed carbohydrate loads of >60 g and this was often followed by rebound hyperglycaemia that lasted >6 hours. A non-linear relationship exists between carbohydrates consumed and the insulin required to cover them. This has implications for control of postprandial blood sugars, especially when consuming large carbohydrate loads. Further studies are required to look at the optimal ratios, duration and type of insulin boluses required to cover increasing carbohydrate loads.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lea, C.S.; Selvin, S.; Buffler, P.A.

This pilot study uses a unique method to calculate cumulative lifetime exposure to, ultraviolet radiation-b to determine if this refined method would indicate differences in lifetime cumulative UVB exposure between age and sex matched controls. Forty-four age and sex matched cases and controls demonstrated no significant difference in mean cumulative lifetime UVB exposure based on the duration and location of residence. This pilot study suggests that further analysis of the dataset should be conducted to determine if the cumulative lifetime exposure hypothesis is of primary importance regarding the association between UVB exposure and development of cutaneous malignant melanoma.

Piezosurgery for Sagittal Split Osteotomy: Procedure Duration and Postoperative Sensory Perturbation.

PubMed

Köhnke, Robert; Kolk, Andreas; Kluwe, Lan; Ploder, Oliver

2017-09-01

To evaluate piezosurgery for bilateral sagittal split osteotomy (BSSO) for its duration and inferior alveolar nerve (IAN) perturbation. In this prospective randomized study, the authors evaluated 100 BSSO procedures in 50 patients. Piezoelectric (group I) and conventional (group II) osteotomies were carried out on each side of the mandible of a patient by 2 specialists. The surgeons had at least 1 year of experience using piezosurgery. The period from incision to complete splitting of the mandibular bone was recorded (ie, procedure duration). The intraoperative status (visibility and relocation) of the IAN also was recorded. The neurosensory function of the IAN was measured by the 2-point discrimination threshold and static light touch methods before surgery and postoperatively (1, 3, and 6 weeks and 6 and 12 months). Parameters were compared between the test groups by the paired t, nonparametric Wilcoxon, or χ 2 test. Intergroup comparison showed the mean duration of osteotomy was significantly shorter for group I (17 ± 6 vs 25 ± 9 minutes; P < .001). The rate of intraoperative exposures of the IAN was slightly lower for group I (68%) compared with group II (81%). However, the difference was not relevant. Neurosensory disturbance and recovery of the IAN did not differ between groups. Piezoelectric osteotomy requires considerably less time than conventional mechanical approaches, but shows no advantage in preventing neurosensory perturbation. Copyright © 2017 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

Development of hypertension after long-term exposure to static magnetic fields among workers from a magnetic resonance imaging device manufacturing facility.

PubMed

Bongers, Suzan; Slottje, Pauline; Kromhout, Hans

2018-07-01

To assess the association between long-term exposure to static magnetic fields (SMF) in a magnetic resonance imaging (MRI)-manufacturing environment and hypertension. In an occupational cohort of male workers (n = 538) of an MRI-manufacturing facility, the first and last available blood pressure measurements from the facility's medical surveillance scheme were associated with modeled cumulative exposure to SMF. Exposure modeling was based on linkage of individual job histories from the facility's personnel records with a facility specific historical job exposure matrix. Hypertension was defined as a systolic pressure of above 140 mm Hg and/or a diastolic blood pressure above 90 mm Hg. Logistic regression models were used to associate cumulative SMF exposure to hypertension while adjusting for age, body mass index and blood pressure at time of first blood pressure measurement. Stratified analysis by exposure duration was performed similarly. High cumulative exposure to SMF (≥ 7.4 K Tesla minutes) was positively associated with development of hypertension (Odds Ratio [OR] 2.32, 95% confidence interval [CI] 1.27 - 4.25, P = 0.006). Stratified analysis showed a stronger association for those with high cumulative SMF exposure within a period up to 10 years (OR 3.96, 95% CI 1.62 - 9.69, P = 0.003), but no significant association was found for (high) cumulative exposure accumulated in a period of 10 or more years. Our findings suggest SMF exposure intensity to be more important than exposure duration for the risk of developing hypertension. Our data revealed that exposure to high levels of MRI-related SMF during MRI-manufacturing might be associated with developing hypertension. Copyright © 2018 Elsevier Inc. All rights reserved.