Science.gov

Sample records for exempt chemical mixtures

  1. Exemption of chemical mixtures. Final rule.

    PubMed

    2007-03-12

    On December 15, 2004, the Drug Enforcement Administration (DEA) published a Final Rule corrected January 4, 2005) that implemented new regulations concerning chemical mixtures that contain any of the 27 listed chemicals. The Final Rule added a new provision not previously raised by DEA in any proposed rulemaking. This newly introduced provision exempted domestic and import transactions in chemical mixtures that are regulated solely due to the presence of the List II solvent chemicals acetone, ethyl ether, 2-butanone, or toluene from the Controlled Substances Act (CSA) recordkeeping and reporting requirements. Because this exemption was not previously proposed in any rulemaking, DEA implemented this exemption on an interim basis and requested public comment on this exemption provision. Based upon a review of all comments, DEA is finalizing this exemption. As such, domestic and import transactions in chemical mixtures containing the List II chemicals acetone, ethyl ether, 2-butanone, and toluene shall be exempt from CSA chemical recordkeeping and reporting requirements.

  2. 21 CFR 1310.13 - Exemption of chemical mixtures; application.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 9 2011-04-01 2011-04-01 false Exemption of chemical mixtures; application. 1310... REPORTS OF LISTED CHEMICALS AND CERTAIN MACHINES § 1310.13 Exemption of chemical mixtures; application. (a... application of all or any part of the Act a chemical mixture consisting of two or more chemical components,...

  3. 21 CFR 1310.12 - Exempt chemical mixtures.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Exempt chemical mixtures. 1310.12 Section 1310.12 Food and Drugs DRUG ENFORCEMENT ADMINISTRATION, DEPARTMENT OF JUSTICE RECORDS AND REPORTS OF LISTED CHEMICALS AND CERTAIN MACHINES § 1310.12 Exempt chemical mixtures. (a) The chemical mixtures meeting the...

  4. 21 CFR 1310.13 - Exemption of chemical mixtures; application.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 9 2014-04-01 2014-04-01 false Exemption of chemical mixtures; application. 1310.13 Section 1310.13 Food and Drugs DRUG ENFORCEMENT ADMINISTRATION, DEPARTMENT OF JUSTICE RECORDS AND REPORTS OF LISTED CHEMICALS AND CERTAIN MACHINES § 1310.13 Exemption of chemical mixtures; application....

  5. 21 CFR 1310.13 - Exemption of chemical mixtures; application.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 9 2012-04-01 2012-04-01 false Exemption of chemical mixtures; application. 1310.13 Section 1310.13 Food and Drugs DRUG ENFORCEMENT ADMINISTRATION, DEPARTMENT OF JUSTICE RECORDS AND REPORTS OF LISTED CHEMICALS AND CERTAIN MACHINES § 1310.13 Exemption of chemical mixtures; application....

  6. 21 CFR 1310.13 - Exemption of chemical mixtures; application.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Exemption of chemical mixtures; application. 1310.13 Section 1310.13 Food and Drugs DRUG ENFORCEMENT ADMINISTRATION, DEPARTMENT OF JUSTICE RECORDS AND REPORTS OF LISTED CHEMICALS AND CERTAIN MACHINES § 1310.13 Exemption of chemical mixtures; application....

  7. Exempt chemical mixtures containing gamma-butyrolactone. Final rule.

    PubMed

    2010-06-29

    This rulemaking finalizes a November 12, 2008, Notice of Proposed Rulemaking in which DEA proposed that chemical mixtures that are 70 percent or less gamma-butyrolactone (GBL), by weight or volume, be automatically exempt from regulatory controls under the Controlled Substances Act (CSA). DEA is seeking through this rulemaking to exempt only those chemical mixtures that do not represent a significant risk of diversion. This regulation makes GBL chemical mixtures, in concentrations greater than 70 percent, subject to List I chemical regulatory requirements of the CSA, except if exempted through an existing categorical exemption. DEA is taking this action because there is a serious threat to the public safety associated with the ease by which GBL is chemically converted to the schedule I controlled substance gamma-hydroxybutyric acid (GHB). DEA recognizes that concentration criteria alone cannot identify all mixtures that warrant exemption. As a result, DEA regulations provide for an application process by which manufacturers may obtain exemptions from CSA regulatory controls for those GBL chemical mixtures that are not automatically exempt under the concentration criteria.

  8. 75 FR 37301 - Exempt Chemical Mixtures Containing Gamma-Butyrolactone

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-29

    ... regulation makes GBL chemical mixtures, in concentrations greater than 70 percent, subject to List I chemical...). DEA recognizes that concentration criteria alone cannot identify all mixtures that warrant exemption... under the concentration criteria. DATES: This rulemaking becomes effective July 29, 2010. Persons...

  9. 21 CFR 1310.12 - Exempt chemical mixtures.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Weight or Volume Benzyl cyanide 8570 20% by Weight or Volume Ephedrine, its salts, optical isomers, and salts of optical isomers 8113 Not exempt at any concentration Chemical mixtures containing any amount of ephedrine and/or pseudoephedrine, and their salts, optical isomers and salts of optical isomers are...

  10. 21 CFR 1310.12 - Exempt chemical mixtures.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... Weight or Volume Benzyl cyanide 8570 20% by Weight or Volume Ephedrine, its salts, optical isomers, and salts of optical isomers 8113 Not exempt at any concentration Chemical mixtures containing any amount of ephedrine and/or pseudoephedrine, and their salts, optical isomers and salts of optical isomers are...

  11. 21 CFR 1310.12 - Exempt chemical mixtures.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Weight or Volume Benzyl cyanide 8570 20% by Weight or Volume Ephedrine, its salts, optical isomers, and salts of optical isomers 8113 Not exempt at any concentration Chemical mixtures containing any amount of ephedrine and/or pseudoephedrine, and their salts, optical isomers and salts of optical isomers are...

  12. 21 CFR 1310.12 - Exempt chemical mixtures.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Weight or Volume Benzyl cyanide 8570 20% by Weight or Volume Ephedrine, its salts, optical isomers, and salts of optical isomers 8113 Not exempt at any concentration Chemical mixtures containing any amount of ephedrine and/or pseudoephedrine, and their salts, optical isomers and salts of optical isomers are...

  13. Elimination of exemptions for chemical mixtures containing the list I chemicals ephedrine and/or pseudoephedrine. Final rule.

    PubMed

    2008-07-10

    The Drug Enforcement Administration (DEA) is finalizing, without change, the Interim Rule with Request for Comment published in the Federal Register on July 25, 2007 (72 FR 40738). The Interim Rule removed the Controlled Substances Act (CSA) exemptions for chemical mixtures containing ephedrine and/or pseudoephedrine with concentration limits at or below five percent. Upon the effective date of the Interim Rule, all ephedrine and pseudoephedrine chemical mixtures, regardless of concentration and form, became subject to the regulatory provisions of the CSA. DEA regulated the importation, exportation, manufacture, and distribution of these chemical mixtures by requiring persons who handle these chemical mixtures to register with DEA, maintain certain records common to business practice, and file certain reports, regarding these chemical mixtures. No comments to the Interim Rule were received. This Final Rule finalizes the Interim Rule without change.

  14. 21 CFR 1308.24 - Exempt chemical preparations.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 9 2014-04-01 2014-04-01 false Exempt chemical preparations. 1308.24 Section 1308... SUBSTANCES Exempt Chemical Preparations § 1308.24 Exempt chemical preparations. (a) The chemical preparations... security: Any person who manufactures an exempt chemical preparation or mixture must be registered under...

  15. 21 CFR 1308.24 - Exempt chemical preparations.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 9 2012-04-01 2012-04-01 false Exempt chemical preparations. 1308.24 Section 1308... SUBSTANCES Exempt Chemical Preparations § 1308.24 Exempt chemical preparations. (a) The chemical preparations... security: Any person who manufactures an exempt chemical preparation or mixture must be registered...

  16. 21 CFR 1308.24 - Exempt chemical preparations.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 9 2013-04-01 2013-04-01 false Exempt chemical preparations. 1308.24 Section 1308... SUBSTANCES Exempt Chemical Preparations § 1308.24 Exempt chemical preparations. (a) The chemical preparations... security: Any person who manufactures an exempt chemical preparation or mixture must be registered...

  17. 21 CFR 1308.24 - Exempt chemical preparations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Exempt chemical preparations. 1308.24 Section 1308... SUBSTANCES Exempt Chemical Preparations § 1308.24 Exempt chemical preparations. (a) The chemical preparations... security: Any person who manufactures an exempt chemical preparation or mixture must be registered...

  18. 21 CFR 1308.24 - Exempt chemical preparations.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 9 2011-04-01 2011-04-01 false Exempt chemical preparations. 1308.24 Section 1308... SUBSTANCES Exempt Chemical Preparations § 1308.24 Exempt chemical preparations. (a) The chemical preparations... security: Any person who manufactures an exempt chemical preparation or mixture must be registered...

  19. 76 FR 31824 - Chemical Mixtures Containing Listed Forms of Phosphorus and Change in Application Process

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-02

    ... mixtures containing red phosphorus in a concentration of 80 percent or less and mixtures containing hypophosphorous acid and its salts (hypophosphite salts) in a concentration of 30 percent and less, shall qualify for automatic exemption. DEA is not implementing automatic exemption for any concentration of chemical...

  20. 76 FR 41371 - Impact of Reducing the Mixture Concentration Threshold for Commercial Schedule 3 Chemical...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-13

    ... Reducing the Mixture Concentration Threshold for Commercial Schedule 3 Chemical Activities Under the... CFR Part 714 Impact of Reducing the Mixture Concentration Threshold for Commercial Schedule 3 Chemical... concentration level at which the CWCR exempt certain mixtures containing Schedule 3 chemicals from the...

  1. 76 FR 41365 - Impact of Reducing the Mixture Concentration Threshold for Commercial Schedule 2A Chemical...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-13

    ... Impact of Reducing the Mixture Concentration Threshold for Commercial Schedule 2A Chemical Activities... Security 15 CFR Parts 713 and 716 RIN 0694-XA27 Impact of Reducing the Mixture Concentration Threshold for... Regulations (CWCR) to reduce the concentration level below which the CWCR exempt certain mixtures containing a...

  2. Research and Development Exemption for New Chemical Review under TSCA

    EPA Pesticide Factsheets

    Section 5(h)(3) of TSCA allows EPA to exempt manufacturers of chemical substances from the notice requirements if they manufacture it in small quantities for the purposed of research and development. This page gives an overview of this exemption.

  3. Test Marketing Exemption (TME) for New Chemical Review under TSCA

    EPA Pesticide Factsheets

    Under section 5 of TSCA, EPA established an exemption for certain chemicals that are manufactured (including imported) for test marketing. You can learn more here about the requirements of this exemption, along with the review and submission process.

  4. 21 CFR 73.1001 - Diluents in color additive mixtures for drug use exempt from certification.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Diluents in color additive mixtures for drug use... § 73.1001 Diluents in color additive mixtures for drug use exempt from certification. The following diluents may be safely used in color additive mixtures that are exempt from certification and which are...

  5. 21 CFR 73.1001 - Diluents in color additive mixtures for drug use exempt from certification.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Diluents in color additive mixtures for drug use... § 73.1001 Diluents in color additive mixtures for drug use exempt from certification. The following diluents may be safely used in color additive mixtures that are exempt from certification and which are...

  6. 21 CFR 73.1001 - Diluents in color additive mixtures for drug use exempt from certification.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Diluents in color additive mixtures for drug use... § 73.1001 Diluents in color additive mixtures for drug use exempt from certification. The following diluents may be safely used in color additive mixtures that are exempt from certification and which are...

  7. 21 CFR 73.1001 - Diluents in color additive mixtures for drug use exempt from certification.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Diluents in color additive mixtures for drug use... § 73.1001 Diluents in color additive mixtures for drug use exempt from certification. The following diluents may be safely used in color additive mixtures that are exempt from certification and which are...

  8. 21 CFR 73.1001 - Diluents in color additive mixtures for drug use exempt from certification.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Diluents in color additive mixtures for drug use... § 73.1001 Diluents in color additive mixtures for drug use exempt from certification. The following diluents may be safely used in color additive mixtures that are exempt from certification and which are...

  9. 21 CFR 80.35 - Color additive mixtures; certification and exemption from certification.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Color additive mixtures; certification and... additive mixtures; certification and exemption from certification. (a) Color additive mixtures to be certified. Any color additive mixture that contains one or more straight colors listed in part 74 of...

  10. 21 CFR 80.35 - Color additive mixtures; certification and exemption from certification.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Color additive mixtures; certification and... additive mixtures; certification and exemption from certification. (a) Color additive mixtures to be certified. Any color additive mixture that contains one or more straight colors listed in part 74 of...

  11. 21 CFR 80.35 - Color additive mixtures; certification and exemption from certification.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Color additive mixtures; certification and... additive mixtures; certification and exemption from certification. (a) Color additive mixtures to be certified. Any color additive mixture that contains one or more straight colors listed in part 74 of...

  12. 21 CFR 80.35 - Color additive mixtures; certification and exemption from certification.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Color additive mixtures; certification and... additive mixtures; certification and exemption from certification. (a) Color additive mixtures to be certified. Any color additive mixture that contains one or more straight colors listed in part 74 of...

  13. 21 CFR 80.35 - Color additive mixtures; certification and exemption from certification.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Color additive mixtures; certification and... additive mixtures; certification and exemption from certification. (a) Color additive mixtures to be certified. Any color additive mixture that contains one or more straight colors listed in part 74 of...

  14. 10 CFR 503.9 - Use of mixtures-general requirement for certain permanent exemptions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Use of mixtures-general requirement for certain permanent... General Requirements for Exemptions § 503.9 Use of mixtures—general requirement for certain permanent... mixtures, section 213(a)(1) of the Act requires a demonstration that the use of a mixture of natural...

  15. 10 CFR 503.9 - Use of mixtures-general requirement for certain permanent exemptions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 4 2011-01-01 2011-01-01 false Use of mixtures-general requirement for certain permanent... General Requirements for Exemptions § 503.9 Use of mixtures—general requirement for certain permanent... mixtures, section 213(a)(1) of the Act requires a demonstration that the use of a mixture of natural...

  16. 10 CFR 503.9 - Use of mixtures-general requirement for certain permanent exemptions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Use of mixtures-general requirement for certain permanent... General Requirements for Exemptions § 503.9 Use of mixtures—general requirement for certain permanent... mixtures, section 213(a)(1) of the Act requires a demonstration that the use of a mixture of natural...

  17. 10 CFR 503.9 - Use of mixtures-general requirement for certain permanent exemptions.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 4 2013-01-01 2013-01-01 false Use of mixtures-general requirement for certain permanent... General Requirements for Exemptions § 503.9 Use of mixtures—general requirement for certain permanent... mixtures, section 213(a)(1) of the Act requires a demonstration that the use of a mixture of natural...

  18. 10 CFR 503.9 - Use of mixtures-general requirement for certain permanent exemptions.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 4 2014-01-01 2014-01-01 false Use of mixtures-general requirement for certain permanent... General Requirements for Exemptions § 503.9 Use of mixtures—general requirement for certain permanent... mixtures, section 213(a)(1) of the Act requires a demonstration that the use of a mixture of natural...

  19. CHEMICAL MIXTURES: CONSEQUENCES FOR WATER QUALITY

    EPA Science Inventory

    Chemicals have the potential to occur as mixtures in sediment, as well as bioaccumulate in aquatic organisms, sometimes resulting in adverse toxicological effects. Presently, assessments of contaminated sediment are based upon single chemical toxicological studies with the assump...

  20. 40 CFR 180.1317 - Pesticide chemicals; exemption from the requirements of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Pesticide chemicals; exemption from... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1317 Pesticide chemicals; exemption from the requirements of a...

  1. 40 CFR 180.905 - Pesticide chemicals; exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Pesticide chemicals; exemptions from... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.905 Pesticide chemicals; exemptions from the requirement of a...

  2. 40 CFR 180.905 - Pesticide chemicals; exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Pesticide chemicals; exemptions from... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.905 Pesticide chemicals; exemptions from the requirement of a...

  3. 40 CFR 180.905 - Pesticide chemicals; exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Pesticide chemicals; exemptions from... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.905 Pesticide chemicals; exemptions from the requirement of a...

  4. 40 CFR 180.905 - Pesticide chemicals; exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Pesticide chemicals; exemptions from... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.905 Pesticide chemicals; exemptions from the requirement of a...

  5. 40 CFR 180.1317 - Pesticide chemicals; exemption from the requirements of a tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Pesticide chemicals; exemption from... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1317 Pesticide chemicals; exemption from the requirements of a...

  6. 40 CFR 180.905 - Pesticide chemicals; exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Pesticide chemicals; exemptions from... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.905 Pesticide chemicals; exemptions from the requirement of a...

  7. Health Risk Assessment of Chemical Mixtures | Science ...

    EPA Pesticide Factsheets

    The implementation of Superfund requires a methodology for estimating health risk from multi-chemical contamination at ambient levels. Most often, the chemical composition of these mixtures is poorly characterized, exposure data are uncertain and toxicologic data on the known components of the mixture are limited. However, a potential human health hazard may exist and the U.S.EPA, state and local governments need to be able to assess the total hazard in order to make decisions on appropriate action. This report describes a procedure for assessing the risks from chemical mixtures that includes options when different kinds of data are available. Good-quality information on the mixture of concern or a similar mixture should always be used. Less desirable, but still useful approach, is to utilize data on components and their interactions. The quality of exposure and toxicity data must be determined and the uncertainties involved in each risk assessment must be thoroughly discussed. ater contamination is briefly discussed since it is of vital concern as the primary exposure medium for chemical mixtures. The methodology for estimating the human health risk from single chemicals, both carcinogens and systemic toxicants, is reviewed as it forms the basis for the assessment of mixtures. The Implementation of Superfund requires a methodology for estimating health risk from multi-chemical contamination at ambient levels. Most often, the chemical composition of these mix

  8. 10 CFR 503.38 - Permanent exemption for certain fuel mixtures containing natural gas or petroleum.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... mixture of solar energy (including wind, tide, and other intermittent sources) and petroleum or natural gas, where: (1) Solar energy will account for at least 20 percent of the total annual Btu heat input... 10 Energy 4 2014-01-01 2014-01-01 false Permanent exemption for certain fuel mixtures containing...

  9. 10 CFR 503.38 - Permanent exemption for certain fuel mixtures containing natural gas or petroleum.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... mixture of solar energy (including wind, tide, and other intermittent sources) and petroleum or natural gas, where: (1) Solar energy will account for at least 20 percent of the total annual Btu heat input... 10 Energy 4 2013-01-01 2013-01-01 false Permanent exemption for certain fuel mixtures containing...

  10. 10 CFR 503.38 - Permanent exemption for certain fuel mixtures containing natural gas or petroleum.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... mixture of solar energy (including wind, tide, and other intermittent sources) and petroleum or natural gas, where: (1) Solar energy will account for at least 20 percent of the total annual Btu heat input... 10 Energy 4 2012-01-01 2012-01-01 false Permanent exemption for certain fuel mixtures containing...

  11. 10 CFR 503.38 - Permanent exemption for certain fuel mixtures containing natural gas or petroleum.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... mixture of solar energy (including wind, tide, and other intermittent sources) and petroleum or natural gas, where: (1) Solar energy will account for at least 20 percent of the total annual Btu heat input... 10 Energy 4 2011-01-01 2011-01-01 false Permanent exemption for certain fuel mixtures containing...

  12. 10 CFR 503.38 - Permanent exemption for certain fuel mixtures containing natural gas or petroleum.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... mixture of solar energy (including wind, tide, and other intermittent sources) and petroleum or natural gas, where: (1) Solar energy will account for at least 20 percent of the total annual Btu heat input... 10 Energy 4 2010-01-01 2010-01-01 false Permanent exemption for certain fuel mixtures containing...

  13. Toxicology of chemical mixtures: international perspective.

    PubMed Central

    Feron, V J; Cassee, F R; Groten, J P

    1998-01-01

    This paper reviews major activities outside the United States on human health issues related to chemical mixtures. In Europe an international study group on combination effects has been formed and has started by defining synergism and antagonism. Successful research programs in Europe include the development and application of statistically designed experiments combined with multivariate data analysis and modeling in vitro and in vivo studies on a wide variety of chemicals such as petroleum hydrocarbons, aldehydes, food contaminants, industrial solvents, and mycotoxins. Other major activities focus on the development of safety evaluation strategies for mixtures such as the use of toxic equivalence factors or alternatives such as the question-and-answer approach, fractionation followed by recombination of the mixture in combination with a mixture design, and quantitative structure-activity relationship analysis combined with lumping analysis and physiologically based pharmacokinetic/pharmacodynamic modeling for studying complex mixtures. A scheme for hazard identification and risk assessment of complex mixtures and a consistent way to generate total volatile organic compound values for indoor air have also been developed. Examples of other activities are carcinogenicity studies on complex mixtures (petroleum middle distillates, foundry fumes, pesticides, heterocyclic amines, diesel exhaust, solid particles), neurotoxicity studies of mixtures of solvents alone or in combination with exposure to physical factors, and toxicity studies of outdoor air pollutants, focusing on particulates. Outside the United States, toxicologists and regulators clearly have a growing interest in the toxicology and risk assessment of chemical mixtures. PMID:9860882

  14. Partial Exemption of Certain Chemical Substances from Reporting Additional Chemical Data

    EPA Pesticide Factsheets

    This Federal Register notice amends the list of chemical substances that are partially exempt from reporting additional information by adding six chemicals in response to a petition the Agency received.

  15. Low Volume Exemption for New Chemical Review under TSCA

    EPA Pesticide Factsheets

    Certain categories of new low-volume chemical substances are exempt from full premanufacture notice (PMN) review, i.e., chemicals manufactured at 10,000 kg/year or less. LVE substances undergo a 30-day review and are not subject to a user fee.

  16. Chemical Mixtures: Considering the Evolution of Toxicology and Chemical Assessment

    PubMed Central

    Monosson, Emily

    2005-01-01

    The assessment of chemical mixtures is a complex topic for toxicologists, regulators, and the public. In this article the linkage between the science of toxicology and the needs of governmental regulatory agencies in the United States is explored through an overview of environmental regulations enacted over the past century and a brief history of modern toxicology. One of the goals of this overview is to encourage both regulators and scientists to consider the benefits and limitations of this science–regulatory relationship as they tackle existing issues such as chemical mixtures. It is clear that a) over the past 100 years chemical regulation and toxicologic research, have in large part, shared a common emphasis on characterization and regulation of individual chemicals. But chemical mixtures have been, and continue to be, evaluated at hazardous waste sites around the United States. For this reason the current U.S. Environmental Protection Agency guidelines for chemical mixtures assessment are also reviewed. These guidelines highlight the current practice of mixtures assessment, which relies primarily on the existing single-chemical database. It is also clear that b) the science and assessment of chemical mixtures are moving forward through the combined efforts of regulatory agencies and scientists from a broad range of disciplines, including toxicology. Because toxicology is at this exciting crossroads, particular attention should be paid to the forces (e.g., public demands, regulatory needs, funding, academic interests) that both promote and limit the growth of this expanding discipline. PMID:15811826

  17. Computing Properties Of Chemical Mixtures At Equilibrium

    NASA Technical Reports Server (NTRS)

    Mcbride, B. J.; Gordon, S.

    1995-01-01

    Scientists and engineers need data on chemical equilibrium compositions to calculate theoretical thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93 is general program that calculates chemical equilibrium compositions and properties of mixtures for any chemical system for which thermodynamic data are available. Includes thermodynamic data for more than 1,300 gaseous and condensed species and thermal-transport data for 151 gases. Written in FORTRAN 77.

  18. Computing Properties Of Chemical Mixtures At Equilibrium

    NASA Technical Reports Server (NTRS)

    Mcbride, B. J.; Gordon, S.

    1995-01-01

    Scientists and engineers need data on chemical equilibrium compositions to calculate theoretical thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93 is general program that calculates chemical equilibrium compositions and properties of mixtures for any chemical system for which thermodynamic data are available. Includes thermodynamic data for more than 1,300 gaseous and condensed species and thermal-transport data for 151 gases. Written in FORTRAN 77.

  19. Predicting skin permeability from complex chemical mixtures

    SciTech Connect

    Riviere, Jim E. . E-mail: Jim_Riviere@ncsu.edu; Brooks, James D.

    2005-10-15

    Occupational and environmental exposure to topical chemicals is usually in the form of complex chemical mixtures, yet risk assessment is based on experimentally derived data from individual chemical exposures from a single, usually aqueous vehicle, or from computed physiochemical properties. We present an approach using hybrid quantitative structure permeation relationships (QSPeR) models where absorption through porcine skin flow-through diffusion cells is well predicted using a QSPeR model describing the individual penetrants, coupled with a mixture factor (MF) that accounts for physicochemical properties of the vehicle/mixture components. The baseline equation is log k {sub p} = c + mMF + a{sigma}{alpha} {sub 2} {sup H} + b{sigma}{beta} {sub 2} {sup H} + s{pi} {sub 2} {sup H} + rR {sub 2} + vV {sub x} where {sigma}{alpha} {sub 2} {sup H} is the hydrogen-bond donor acidity, {sigma}{beta} {sub 2} {sup H} is the hydrogen-bond acceptor basicity, {pi} {sub 2} {sup H} is the dipolarity/polarizability, R {sub 2} represents the excess molar refractivity, and V {sub x} is the McGowan volume of the penetrants of interest; c, m, a, b, s, r, and v are strength coefficients coupling these descriptors to skin permeability (k {sub p}) of 12 penetrants (atrazine, chlorpyrifos, ethylparathion, fenthion, methylparathion, nonylphenol, {rho}-nitrophenol, pentachlorophenol, phenol, propazine, simazine, and triazine) in 24 mixtures. Mixtures consisted of full factorial combinations of vehicles (water, ethanol, propylene glycol) and additives (sodium lauryl sulfate, methyl nicotinate). An additional set of 4 penetrants (DEET, SDS, permethrin, ricinoleic acid) in different mixtures were included to assess applicability of this approach. This resulted in a dataset of 16 compounds administered in 344 treatment combinations. Across all exposures with no MF, R{sup 2} for absorption was 0.62. With the MF, correlations increased up to 0.78. Parameters correlated to the MF include refractive

  20. 21 CFR 1310.09 - Temporary exemption from registration.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... manufacture, distribute, import, or export regulated iodine, including regulated iodine chemical mixtures... a chemical mixture containing iodine on or before August 31, 2007. The exemption will remain in... distributes, imports, or exports a chemical mixture containing iodine whose application for exemption...

  1. 21 CFR 1310.09 - Temporary exemption from registration.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... manufacture, distribute, import, or export regulated iodine, including regulated iodine chemical mixtures... a chemical mixture containing iodine on or before August 31, 2007. The exemption will remain in... distributes, imports, or exports a chemical mixture containing iodine whose application for exemption...

  2. Low Releases and Low Exposures (LoREX) Exemption for New Chemicals Review under TSCA

    EPA Pesticide Factsheets

    EPA established an exemption category for certain new chemical substances with low environmental releases and human exposures. To ensure that they will not present an unreasonable risk, EPA has included a 30-day review and other conditions in the exemption

  3. Spinodal decomposition of chemically reactive binary mixtures

    NASA Astrophysics Data System (ADS)

    Lamorgese, A.; Mauri, R.

    2016-08-01

    We simulate the influence of a reversible isomerization reaction on the phase segregation process occurring after spinodal decomposition of a deeply quenched regular binary mixture, restricting attention to systems wherein material transport occurs solely by diffusion. Our theoretical approach follows a diffuse-interface model of partially miscible binary mixtures wherein the coupling between reaction and diffusion is addressed within the frame of nonequilibrium thermodynamics, leading to a linear dependence of the reaction rate on the chemical affinity. Ultimately, the rate for an elementary reaction depends on the local part of the chemical potential difference since reaction is an inherently local phenomenon. Based on two-dimensional simulation results, we express the competition between segregation and reaction as a function of the Damköhler number. For a phase-separating mixture with components having different physical properties, a skewed phase diagram leads, at large times, to a system converging to a single-phase equilibrium state, corresponding to the absolute minimum of the Gibbs free energy. This conclusion continues to hold for the critical phase separation of an ideally perfectly symmetric binary mixture, where the choice of final equilibrium state at large times depends on the initial mean concentration being slightly larger or less than the critical concentration.

  4. 21 CFR 1310.16 - Exemptions for certain scheduled listed chemical products.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 9 2011-04-01 2011-04-01 false Exemptions for certain scheduled listed chemical... RECORDS AND REPORTS OF LISTED CHEMICALS AND CERTAIN MACHINES § 1310.16 Exemptions for certain scheduled listed chemical products. (a) Upon the application of a manufacturer of a scheduled listed...

  5. Public health challenges posed by chemical mixtures.

    PubMed Central

    Hansen, H; De Rosa, C T; Pohl, H; Fay, M; Mumtaz, M M

    1998-01-01

    Approximately 40 million people live within a 4-mile radius of waste sites that the Agency for Toxic Substances and Disease Registry (ATSDR) has assessed to date. Human populations living in the vicinity of such sites are often subjected to complex chemical exposures that may contribute to the total body burden of oxogenous chemicals. Apart from the contaminants found at waste sites, exposure may also include environmental, occupational, and personal agents. Concurrent exposure to chemicals such as welding fumes, indoor air pollutants, tobacco smoke, alcohol, and prescription and nonprescription drugs makes the health assessment of exposure to waste site chemicals a more complex task. Voluntary exposures such as these frequently entail exposures to relatively high chemical concentrations and can usually be well defined and quantified. Conversely, involuntary exposures from waste sites may be at low concentrations and hence difficult to characterize and quantify. Of the approximately 1450 waste sites evaluated by the ATSDR, 530 (37%) had either completed or potentially completed exposure pathways. Results of public health assessments conducted at 167 sites during 1993 to 1995 show that about 1.5 million people have been exposed to site-specific contaminants. At 10% or more of the sites that had either completed or potentially completed exposure pathways, 56 substances were identified. Of these, 19 are either known or anticipated human carcinogens, and 9 are associated with reproductive or endocrine-disrupting effects. In this paper we present important concerns regarding hazardous waste sites including the impact on human health, ecology, and quality of life. To address such human-health related issues, the ATSDR has established a mixtures program that consists of three components: trend analysis to identify combinations of chemicals of concern, experimental studies to identify data that would be useful in the development and implementation of predictive decision

  6. Chemical Mixture Risk Assessment Additivity-Based Approaches

    EPA Science Inventory

    Powerpoint presentation includes additivity-based chemical mixture risk assessment methods. Basic concepts, theory and example calculations are included. Several slides discuss the use of "common adverse outcomes" in analyzing phthalate mixtures.

  7. Chemical Mixture Risk Assessment Additivity-Based Approaches

    EPA Science Inventory

    Powerpoint presentation includes additivity-based chemical mixture risk assessment methods. Basic concepts, theory and example calculations are included. Several slides discuss the use of "common adverse outcomes" in analyzing phthalate mixtures.

  8. 21 CFR 1310.16 - Exemptions for certain scheduled listed chemical products.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Exemptions for certain scheduled listed chemical products. 1310.16 Section 1310.16 Food and Drugs DRUG ENFORCEMENT ADMINISTRATION, DEPARTMENT OF JUSTICE RECORDS AND REPORTS OF LISTED CHEMICALS AND CERTAIN MACHINES § 1310.16 Exemptions for certain...

  9. 40 CFR 372.38 - Exemptions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... COMMUNITY RIGHT-TO-KNOW PROGRAMS TOXIC CHEMICAL RELEASE REPORTING: COMMUNITY RIGHT-TO-KNOW Reporting Requirements § 372.38 Exemptions. (a) De minimis concentrations of a toxic chemical in a mixture. If a toxic chemical is present in a mixture of chemicals at a covered facility and the toxic chemical is in a...

  10. New Chemical Information Bulletin: Exemptions for Research and Development and Test Marketing

    EPA Pesticide Factsheets

    EPA has received numerous questions about the scope of the exemption for R&D, under TSCA section 5(h)(3). This New Chemical Information Bulletin provides more specific guidance to manufacturers and processors of new chemical substances.

  11. Health and environmental effects of complex chemical mixtures: proceedings

    SciTech Connect

    Not Available

    1985-01-01

    The Office of Health and Environmental Research (OHER) of the Department of Energy supports a broad long-term research program on human health and environmental effects from potential exposure to energy-related complex chemical mixtures. The program seeks basic mechanistic data on the effects of complex mixtures at the cellular, molecular, and whole animal levels to aid in predicting human health effects and seeks ecological data on biological and physical transformations in the mixtures, concentrations of the mixtures in various compartments of the environment, and potential routes for human exposure to these mixtures (e.g., food chain). On June 17-18, 1985, OHER held its First Annual Technical Meeting on the Complex Chemical Mixtures Program in Chicago, IL. The primary purpose of the meeting was to enable principal investigators to report the research status and accomplishments of ongoing complex chemical mixture studies supported by OHER. To help focus future research directions round table discussions were conducted.

  12. Thermodynamic Calculations for Complex Chemical Mixtures

    NASA Technical Reports Server (NTRS)

    Mcbride, B. J.

    1986-01-01

    General computer program, CECTRP, developed for calculation of thermodynamic properties of complex mixtures with option to calculate transport properties of these mixtures. Free-energy minimization technique used in equilibrium calculation. Rigorous equations used in transport calculations. Program calculates equilibrium compositions and corresponding thermodynamic and transport properties of mixtures. CECTRP accommodates up to 24 reactants, 20 elements, and 600 products, 400 of which are condensed. Written in FORTRAN IV for any large computer system.

  13. 40 CFR 372.38 - Exemptions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... person produced the mixture, either by mixing the chemicals involved or by causing a chemical reaction... COMMUNITY RIGHT-TO-KNOW PROGRAMS TOXIC CHEMICAL RELEASE REPORTING: COMMUNITY RIGHT-TO-KNOW Reporting Requirements § 372.38 Exemptions. (a) De minimis concentrations of a toxic chemical in a mixture. If a toxic...

  14. 40 CFR 372.38 - Exemptions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... person produced the mixture, either by mixing the chemicals involved or by causing a chemical reaction... COMMUNITY RIGHT-TO-KNOW PROGRAMS TOXIC CHEMICAL RELEASE REPORTING: COMMUNITY RIGHT-TO-KNOW Reporting Requirements § 372.38 Exemptions. (a) De minimis concentrations of a toxic chemical in a mixture. If a toxic...

  15. 40 CFR 372.38 - Exemptions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... person produced the mixture, either by mixing the chemicals involved or by causing a chemical reaction... COMMUNITY RIGHT-TO-KNOW PROGRAMS TOXIC CHEMICAL RELEASE REPORTING: COMMUNITY RIGHT-TO-KNOW Reporting Requirements § 372.38 Exemptions. (a) De minimis concentrations of a toxic chemical in a mixture. If a toxic...

  16. 40 CFR 372.38 - Exemptions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... person produced the mixture, either by mixing the chemicals involved or by causing a chemical reaction... COMMUNITY RIGHT-TO-KNOW PROGRAMS TOXIC CHEMICAL RELEASE REPORTING: COMMUNITY RIGHT-TO-KNOW Reporting Requirements § 372.38 Exemptions. (a) De minimis concentrations of a toxic chemical in a mixture. If a toxic...

  17. Cumulative effects of anti-androgenic chemical mixtures and ...

    EPA Pesticide Factsheets

    Kembra L. Howdeshell and L. Earl Gray, Jr.Toxicological studies of defined chemical mixtures assist human health risk assessment by characterizing the joint action of chemicals. This presentation will review the effects of anti-androgenic chemical mixtures on reproductive tract development in rats with a special focus on the reproductive toxicant phthalates. Observed mixture data are compared to mathematical mixture model predictions to determine how the individual chemicals in a mixture interact (e.g., response addition – probabilities of response for each individual chemical are added; dose-addition – the doses of each individual chemical at a given mixture dose are combined together based on the relative potency of the individual chemicals). Phthalate mixtures are observed to act in a dose-additive manner based on the relative potency of the individual phthalates to suppress fetal testosterone production. Similar dose-additive effects have been reported for mixtures of phthalates with anti-androgenic pesticides of differing mechanisms. Data from these phthalate experiments in rats can be used in conjunction with human biomonitoring data to determine individual hazard ratios. Furthermore, data from the toxicological studies can inform the analysis of human biomonitoring data on the association of detected chemicals and their metabolites with measured health outcomes. Data from phthalate experiments in rats can be used in conjunction with human biomonit

  18. Cumulative effects of anti-androgenic chemical mixtures and ...

    EPA Pesticide Factsheets

    Kembra L. Howdeshell and L. Earl Gray, Jr.Toxicological studies of defined chemical mixtures assist human health risk assessment by characterizing the joint action of chemicals. This presentation will review the effects of anti-androgenic chemical mixtures on reproductive tract development in rats with a special focus on the reproductive toxicant phthalates. Observed mixture data are compared to mathematical mixture model predictions to determine how the individual chemicals in a mixture interact (e.g., response addition – probabilities of response for each individual chemical are added; dose-addition – the doses of each individual chemical at a given mixture dose are combined together based on the relative potency of the individual chemicals). Phthalate mixtures are observed to act in a dose-additive manner based on the relative potency of the individual phthalates to suppress fetal testosterone production. Similar dose-additive effects have been reported for mixtures of phthalates with anti-androgenic pesticides of differing mechanisms. Data from these phthalate experiments in rats can be used in conjunction with human biomonitoring data to determine individual hazard ratios. Furthermore, data from the toxicological studies can inform the analysis of human biomonitoring data on the association of detected chemicals and their metabolites with measured health outcomes. Data from phthalate experiments in rats can be used in conjunction with human biomonit

  19. 77 FR 32633 - Approval of Test Marketing Exemptions for Certain New Chemicals

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-01

    ... AGENCY Approval of Test Marketing Exemptions for Certain New Chemicals AGENCY: Environmental Protection... marketing exemptions (TMEs) under section 5(h)(1) of the Toxic Substances Control Act (TSCA). EPA has...-7. The test marketing conditions are described in the TME applications and in this notice. DATES...

  20. 75 FR 77634 - Approval of Test Marketing Exemptions for Certain New Chemicals

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-13

    ... AGENCY Approval of Test Marketing Exemptions for Certain New Chemicals AGENCY: Environmental Protection... marketing exemptions (TMEs) under section 5(h)(1) of the Toxic Substances Control Act (TSCA) and 40 CFR 720...; TME-10-06; TME-10-08; TME-10-09. The test marketing conditions are described in the TME applications...

  1. 21 CFR 1309.25 - Temporary exemption from registration for chemical registration applicants.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 9 2012-04-01 2012-04-01 false Temporary exemption from registration for chemical registration applicants. 1309.25 Section 1309.25 Food and Drugs DRUG ENFORCEMENT ADMINISTRATION, DEPARTMENT OF.... The exemption will remain in effect for each person who has made such application until...

  2. 21 CFR 1309.25 - Temporary exemption from registration for chemical registration applicants.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Temporary exemption from registration for chemical registration applicants. 1309.25 Section 1309.25 Food and Drugs DRUG ENFORCEMENT ADMINISTRATION, DEPARTMENT OF.... The exemption will remain in effect for each person who has made such application until...

  3. 21 CFR 1310.16 - Exemptions for certain scheduled listed chemical products.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... RECORDS AND REPORTS OF LISTED CHEMICALS AND CERTAIN MACHINES § 1310.16 Exemptions for certain scheduled... if the application should be granted. (d) Within a reasonable period of time after the receipt of...

  4. 75 FR 53867 - Additions to Listing of Exempt Chemical Mixtures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-02

    ... reviewed applications and relevant information, DEA finds that these 21 preparations meet the applicable...% acetonitrile), dimethylformamide, ethylene glycol, isopropanol, methanol, methanol/water (50:50), methanol..., acetonitrile, acetonitrile: water (>= 50% acetonitrile), dimethylformamide, ethylene glycol,...

  5. 21 CFR 1310.13 - Exemption of chemical mixtures; application.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...-dimethoxyethane, acetonitrile, acetonitrile: water (≥ 50% acetonitrile), dimethylformamide, ethylene glycol...), dimethylformamide, ethylene glycol, isopropanol, methanol, methanol/water (50:50), methanol/dimethyl sulfoxide (80...: water (≥ 50% acetonitrile), dimethylformamide, ethylene glycol, isopropanol, methanol,...

  6. Identification and Prioritization of Chemical Mixtures from Environmental Residue Data

    EPA Science Inventory

    High throughput toxicity testing has greatly improved the speed at which single chemicals can be screened using in vitro methods. However, people are not exposed to a single chemical at a time, rather to a mixture of chemicals. Even with the increased speed of these methods, te...

  7. Identification and Prioritization of Chemical Mixtures from Environmental Residue Data

    EPA Science Inventory

    High throughput toxicity testing has greatly improved the speed at which single chemicals can be screened using in vitro methods. However, people are not exposed to a single chemical at a time, rather to a mixture of chemicals. Even with the increased speed of these methods, te...

  8. GENE INDUCTION STUDIES AND TOXICITY OF CHEMICAL MIXTURES

    EPA Science Inventory

    As part of its mixtures program the Agency for Toxic Substances and Disease Registry (ATSDR) supports in vitro and limited in vivo toxicity testing to further our understanding of the toxicity and health effects of chemical mixtures. There are increasing concerns that environment...

  9. GENE INDUCTION STUDIES AND TOXICITY OF CHEMICAL MIXTURES

    EPA Science Inventory

    As part of its mixtures program the Agency for Toxic Substances and Disease Registry (ATSDR) supports in vitro and limited in vivo toxicity testing to further our understanding of the toxicity and health effects of chemical mixtures. There are increasing concerns that environment...

  10. PREDICTING EVAPORATION RATES AND TIMES FOR SPILLS OF CHEMICAL MIXTURES

    EPA Science Inventory


    Spreadsheet and short-cut methods have been developed for predicting evaporation rates and evaporation times for spills (and constrained baths) of chemical mixtures. Steady-state and time-varying predictions of evaporation rates can be made for six-component mixtures, includ...

  11. PREDICTING EVAPORATION RATES AND TIMES FOR SPILLS OF CHEMICAL MIXTURES

    EPA Science Inventory


    Spreadsheet and short-cut methods have been developed for predicting evaporation rates and evaporation times for spills (and constrained baths) of chemical mixtures. Steady-state and time-varying predictions of evaporation rates can be made for six-component mixtures, includ...

  12. Understanding the human health effects of chemical mixtures.

    PubMed Central

    Carpenter, David O; Arcaro, Kathleen; Spink, David C

    2002-01-01

    Most research on the effects of chemicals on biologic systems is conducted on one chemical at a time. However, in the real world people are exposed to mixtures, not single chemicals. Although various substances may have totally independent actions, in many cases two substances may act at the same site in ways that can be either additive or nonadditive. Many even more complex interactions may occur if two chemicals act at different but related targets. In the extreme case there may be synergistic effects, in which case the effects of two substances together are greater than the sum of either effect alone. In reality, most persons are exposed to many chemicals, not just one or two, and therefore the effects of a chemical mixture are extremely complex and may differ for each mixture depending on the chemical composition. This complexity is a major reason why mixtures have not been well studied. In this review we attempt to illustrate some of the principles and approaches that can be used to study effects of mixtures. By the nature of the state of the science, this discussion is more a presentation of what we do not know than of what we do know about mixtures. We approach the study of mixtures at three levels, using specific examples. First, we discuss several human diseases in relation to a variety of environmental agents believed to influence the development and progression of the disease. We present results of selected cellular and animal studies in which simple mixtures have been investigated. Finally, we discuss some of the effects of mixtures at a molecular level. PMID:11834461

  13. Thermal Conductivity of Gas Mixtures in Chemical Equilibrium

    NASA Technical Reports Server (NTRS)

    Brokaw, Richard S.

    1960-01-01

    The expression for the thermal conductivity of gas mixtures in chemical equilibrium is presented in a simpler and less restrictive form. This new form is shown to be equivalent to the previous equations.

  14. Helping Students Distinguish between Mixtures and Chemical Compounds.

    ERIC Educational Resources Information Center

    Papageorgiou, George

    2002-01-01

    Describes a model demonstrating the difference between mixtures and chemical compounds in which two different colors of clay are used to represent two different elements. Makes connections to real world situations. (YDS)

  15. 76 FR 16353 - International Traffic in Arms Regulations: Exemption for Temporary Export of Chemical Agent...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-23

    ... Chemical Agent Protective Gear AGENCY: Department of State. ACTION: Proposed rule. SUMMARY: The Department... exemption for the temporary export of chemical agent protective gear for exclusive personal use to... chemical agent protective gear for personal safety. In August 2009, the ITAR was amended to provide...

  16. Thyroid disrupting chemicals: Mechanisms and mixtures

    EPA Science Inventory

    Environmental contaminants are known to act as thyroid disrupting chemicals (TDCs). Broadly defined, TDCs are xenobiotics that alter the structure or function of the thyroid gland, alter regulatory enzymes associated with thyroid hormone (TH) homeostasis, or change circulating o...

  17. Thyroid disrupting chemicals: Mechanisms and mixtures

    EPA Science Inventory

    Environmental contaminants are known to act as thyroid disrupting chemicals (TDCs). Broadly defined, TDCs are xenobiotics that alter the structure or function of the thyroid gland, alter regulatory enzymes associated with thyroid hormone (TH) homeostasis, or change circulating o...

  18. Tools and perspectives for assessing chemical mixtures and multiple stressors.

    PubMed

    Løkke, Hans; Ragas, Ad M J; Holmstrup, Martin

    2013-11-16

    The present paper summarizes the most important insights and findings of the EU NoMiracle project with a focus on (1) risk assessment of chemical mixtures, (2) combinations of chemical and natural stressors, and (3) the receptor-oriented approach in cumulative risk assessment. The project aimed at integration of methods for human and ecological risk assessment. A mechanistically based model, considering uptake and toxicity as a processes in time, has demonstrated considerable potential for predicting mixture effects in ecotoxicology, but requires the measurement of toxicity endpoints at different moments in time. Within a novel framework for risk assessment of chemical mixtures, the importance of environmental factors on toxicokinetic processes is highlighted. A new paradigm for applying personal characteristics that determine individual exposure and sensitivity in human risk assessment is suggested. The results are discussed in the light of recent developments in risk assessment of mixtures and multiple stressors.

  19. 78 FR 4446 - Exempt Chemical Preparations Under the Controlled Substances Act

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-22

    ... (codified at Title 21, Chapter 13 of the U.S.C.), as amended (hereinafter, ``CSA''). DEA drafts and... U.S.C. 811) authorizes the Attorney General, by regulation, to exempt from certain provisions of the... such compounds, mixtures, or preparations meet the requirements detailed in 21 U.S.C....

  20. Chemical mixtures and health effects at Superfund sites.

    PubMed

    Dyer, Robert S

    2002-03-01

    Between 1991 and 1993, EPA's Office of Research and Development conducted a small health effects research program dedicated to the problem of chemical mixtures at Superfund sites. This paper summarizes key findings from the program. The studies covered a wide range of endpoints, several chemical classes, and mixture complexities ranging from two to five chemicals. Additivity and antagonism were far more common than synergy. Departures from additivity seemed to be on the order of a factor of two or less, an observation that may provide some bounds for concern.

  1. Computations of fluid mixtures including solid carbon at chemical equilibrium

    NASA Astrophysics Data System (ADS)

    Bourasseau, Emeric

    2013-06-01

    One of the key points of the understanding of detonation phenomena is the determination of equation of state of the detonation products mixture. Concerning carbon rich explosives, detonation products mixtures are composed of solid carbon nano-clusters immersed in a high density fluid phase. The study of such systems where both chemical and phase equilibriums occur simultaneously represents an important challenge and molecular simulation methods appear to be one of the more promising way to obtain some answers. In this talk, the Reaction Ensemble Monte Carlo (RxMC) method will be presented. This method allows the system to reach the chemical equilibrium of a mixture driven by a set of linearly independent chemical equations. Applied to detonation product mixtures, it allows the calculation of the chemical composition of the mixture and its thermodynamic properties. Moreover, an original model has been proposed to take explicitly into account a solid carbon meso-particle in thermodynamic and chemical equilibrium with the fluid. Finally our simulations show that the intrinsic inhomogeneous nature of the system (i.e. the fact that the solid phase is immersed in the fluid phase) has an important impact on the thermodynamic properties, and as a consequence must be taken into account.

  2. Combustion of novel chemical mixtures for hydrogen generation

    SciTech Connect

    Shafirovich, Evgeny; Diakov, Victor; Varma, Arvind

    2006-01-01

    Novel chemical compositions for combustion-based generation of hydrogen, which can be used to feed fuel cells for emergency power supplies and portable electronics, are reported. Combustion heat release from the proposed gas-generating compositions can be converted to electricity. The proposed sodium borohydride/aluminum/water mixtures are combustible and exhibit high hydrogen yield. Mixtures with 50-70 wt% of Al are promising to obtain simultaneously high H{sub 2} yield and stable self-sustained combustion.

  3. Chemical recognition of gases and gas mixtures with terahertz waves

    NASA Astrophysics Data System (ADS)

    Jacobsen, R. H.; Mittleman, D. M.; Nuss, M. C.

    1996-12-01

    A time-domain chemical-recognition system for classifying gases and analyzing gas mixtures is presented. We analyze the free induction decay exhibited by gases excited by far-infrared (terahertz) pulses in the time domain, using digital signal-processing techniques. A simple geometric picture is used for the classification of the waveforms measured for unknown gas species. We demonstrate how the recognition system can be used to determine the partial pressures of an ammonia-water gas mixture.

  4. Predictive environmental risk assessment of chemical mixtures: a conceptual framework.

    PubMed

    Backhaus, Thomas; Faust, Michael

    2012-03-06

    Environmental risks of chemicals are still often assessed substance-by-substance, neglecting mixture effects. This may result in risk underestimations, as the typical exposure is toward multicomponent chemical "cocktails". We use the two well established mixture toxicity concepts (Concentration Addition (CA) and Independent Action (IA)) for providing a tiered outline for environmental hazard and risk assessments of mixtures, focusing on general industrial chemicals and assuming that the "base set" of data (EC50s for algae, crustaceans, fish) is available. As mixture toxicities higher than predicted by CA are rare findings, we suggest applying CA as a precautious first tier, irrespective of the modes/mechanisms of action of the mixture components. In particular, we prove that summing up PEC/PNEC ratios might serve as a justifiable CA-approximation, in order to estimate in a first tier assessment whether there is a potential risk for an exposed ecosystem if only base-set data are available. This makes optimum use of existing single substance assessments as more demanding mixture investigations are requested only if there are first indications of an environmental risk. Finally we suggest to call for mode-of-action driven analyses only if error estimations indicate the possibility for substantial differences between CA- and IA-based assessments.

  5. Comparing bee species responses to chemical mixtures: Common response patterns?

    PubMed Central

    Lahive, Elma; Horton, Alice A.; Svendsen, Claus; Rortais, Agnes; Dorne, Jean Lou; Baas, Jan; Heard, Matthew S.; Spurgeon, David J.

    2017-01-01

    Pollinators in agricultural landscapes can be exposed to mixtures of pesticides and environmental pollutants. Existing mixture toxicity modelling approaches, such as the models of concentration addition and independent action and the mechanistic DEBtox framework have been previously shown as valuable tools for understanding and ultimately predicting joint toxicity. Here we apply these mixture models to investigate the potential to interpret the effects of semi-chronic binary mixture exposure for three bee species: Apis mellifera, Bombus terrestris and Osmia bicornis within potentiation and mixture toxicity experiments. In the potentiation studies, the effect of the insecticide dimethoate with added propiconazole fungicide and neonicotinoid insecticide clothianidin with added tau-fluvalinate pyrethroid acaricide showed no difference in toxicity compared to the single chemical alone. Clothianidin toxicity showed a small scale, but temporally conserved increase in exposure conducted in the presence of propiconazole, particularly for B. terrestris and O. bicornis, the latter showing a near three-fold increase in clothianidin toxicity in the presence of propiconazole. In the mixture toxicity studies, the dominant response patterns were of additivity, however, binary mixtures of clothianidin and dimethoate in A. mellifera, B. terrestris and male O. bicornis there was evidence of a predominant antagonistic interaction. Given the ubiquitous nature of exposures to multiple chemicals, there is an urgent need to consider mixture effects in pollinator risk assessments. Our analyses suggest that current models, particularly those that utilise time-series data, such as DEBtox, can be used to identify additivity as the dominant response pattern and also those examples of interactions, even when small-scale, that may need to be taken into account during risk assessment. PMID:28640811

  6. Control of Foaming by Adding Known Mixtures of Pure Chemicals

    DTIC Science & Technology

    1949-04-01

    Glycerol apparently does not have this undesired property. The chemical compound erythritol , intermediate between glycerol and xylitol, is now under... erythritol results in a longer period of effectiveness. The best mixture and its optimum concentrations are yet to be definitely established. Meanwhile a... erythritol fulfill these requirements and are more effective. The search for additional compounds has been conducted along the lines thus suggested

  7. Environmental chemical mixtures: Assessing ecological exposure and effects in streams

    EPA Science Inventory

    This product is a USGS fact sheet that describes a collaborative effort between USGS and US EPA to characterize exposures to chemical mixtures and associated biological effects for a diverse range of US streams representing varying watershed size, land-use patterns, and ecotypes.

  8. Environmental chemical mixtures: Assessing ecological exposure and effects in streams

    EPA Science Inventory

    This product is a USGS fact sheet that describes a collaborative effort between USGS and US EPA to characterize exposures to chemical mixtures and associated biological effects for a diverse range of US streams representing varying watershed size, land-use patterns, and ecotypes.

  9. Mixtures of Estrogenic Chemicals Enhance Vitellogenic Response in Sea Bass

    PubMed Central

    Correia, Ana D.; Freitas, Sandro; Scholze, Martin; Goncalves, José F.; Booij, Petra; Lamoree, Marja H.; Mañanós, Evaristo; Reis-Henriques, Maria A.

    2007-01-01

    Background The potential impact of natural and synthetic estrogens on aquatic ecosystems has attracted considerable attention because it is currently accepted that their joint effects are more severe when they are present in mixtures. Although it is well-known that they occur as mixtures in the marine environment, there is little information about the combined effects of estrogenic chemicals on marine biota. Objective In 14-day tests with juvenile sea bass, we analyzed singly and in combination the estrogenic activity of estradiol (E2), ethynylestradiol (EE2), and bisphenol A (BPA) using vitellogenin induction as an end point. Methods Fish were exposed to each compound, and on the basis of these concentration–response data, we predicted mixture effects by applying the model of concentration addition. The mixtures were tested using a fixed-ratio design, and the resulting mixture effects were compared to the predictions. Results EE2 was the most potent steroid, with an EC50 (median effective concentration) of 0.029 μg/L, 3.6 times more potent than E2 (EC50 = 0.104 μg/L); BPA was the least potent chemical, with an EC50 of 77.94 μg/L. The comparative assessment yielded a good agreement between observed and predicted mixture effects. Conclusions This study demonstrates the potential hazard of these compounds to seawater life by their ability to act together in an additive manner. It provides evidence that concentration addition can be used as a predictive tool for assessing the combined effects of estrogenic chemicals in marine ecosystems. PMID:18174959

  10. Differentiation of vapor mixture with chemical sensor arrays

    NASA Astrophysics Data System (ADS)

    Kim, Chulki; Jung, Youngmo; Moon, Hi Gyu; Lee, Ji Eun; Shin, Bum Ju; Lim, Chaehyun; Choi, Jaebin; Seo, Minah; Kim, Jae Hun; Jun, Seong Chan; Kim, Sang Kyung; Kang, Chong Yun; Lee, Taikjin; Lee, Seok

    2015-07-01

    Arrays of partially selective chemical sensors have been the focus of extensive research over the past decades because of their potential for widespread application in ambient air monitoring, health and safety, and biomedical diagnostics. Especially, vapor sensor arrays based on functionalized nanomaterials have shown great promise with their high sensitivity by dimensionality and outstanding electronic properties. Here, we introduce experiments where individual vapors and mixtures of them are examined by different chemical sensor arrays. The collected data from those sensor arrays are further analyzed by a principal component analysis (PCA) and targeted vapors are recognized based on prepared database.

  11. Predicting evaporation rates and times for spills of chemical mixtures.

    PubMed

    Smith, R L

    2001-08-01

    Spreadsheet and short-cut methods have been developed for predicting evaporation rates and evaporation times for spills and constrained baths of chemical mixtures. Steady-state and time-varying predictions of evaporation rates can be made for six-component mixtures, including liquid-phase non-idealities as expressed through the UNIFAC method for activity coefficients. A group-contribution method is also used to estimate vapor-phase diffusion coefficients, which makes the method completely predictive. The predictions are estimates that require professional judgement in their application. One application that the evaporation time calculations suggest is a method for labeling chemical containers that allows one to quickly assess the time for complete evaporation of spills of both pure components and mixtures. The labeling would take the form of an evaporation time that depends on the local environment. For instance, evaporation time depends on indoor or outdoor conditions and the amount of each chemical among other parameters. This labeling would provide rapid information and an opportunity to premeditate a response before a spill occurs.

  12. Comparison of Chemical Composition of Complex Disinfection Byproduct (DBP) Mixtures Produced by Different Treatment Methods

    EPA Science Inventory

    Analyses of the chemical composition of complex DBP mixtures, produced by different drinking water treatment processes, are essential to generate toxicity data required for assessing their risks to humans. For mixture risk assessments, whole mixture toxicology studies generally a...

  13. Comparison of Chemical Composition of Complex Disinfection Byproduct (DBP) Mixtures Produced by Different Treatment Methods - slides

    EPA Science Inventory

    Analyses of the chemical composition of complex DBP mixtures, produced by different drinking water treatment processes, are essential to generate toxicity data required for assessing their risks to humans. For mixture risk assessments, whole mixture toxicology studies generally a...

  14. Comparison of Chemical Composition of Complex Disinfection Byproduct (DBP) Mixtures Produced by Different Treatment Methods

    EPA Science Inventory

    Analyses of the chemical composition of complex DBP mixtures, produced by different drinking water treatment processes, are essential to generate toxicity data required for assessing their risks to humans. For mixture risk assessments, whole mixture toxicology studies generally a...

  15. Comparison of Chemical Composition of Complex Disinfection Byproduct (DBP) Mixtures Produced by Different Treatment Methods - slides

    EPA Science Inventory

    Analyses of the chemical composition of complex DBP mixtures, produced by different drinking water treatment processes, are essential to generate toxicity data required for assessing their risks to humans. For mixture risk assessments, whole mixture toxicology studies generally a...

  16. 21 CFR 73.1 - Diluents in color additive mixtures for food use exempt from certification.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... sequestrant in color additive mixtures intended only for ingested use; the color additive mixture (solution or... additive mixture (solution or dispersion) may contain not more than 1 percent by weight of the diluent... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Diluents in color additive mixtures for food...

  17. A Statistical Approach for Judging Stability of Whole Mixture Chemical Composition over Time for Highly Complex Disinfection By-Product Mixtures from EPA's Four Lab Study

    EPA Science Inventory

    Chemical characterization of complex mixtures and assessment of stability over time of the characterized chemicals is crucial both to characterize exposure and to use data from one mixture as a surrogate for other similar mixtures. The chemical composition of test mixtures can va...

  18. A Statistical Approach for Judging Stability of Whole Mixture Chemical Composition over Time for Highly Complex Disinfection By-Product Mixtures from EPA's Four Lab Study

    EPA Science Inventory

    Chemical characterization of complex mixtures and assessment of stability over time of the characterized chemicals is crucial both to characterize exposure and to use data from one mixture as a surrogate for other similar mixtures. The chemical composition of test mixtures can va...

  19. An approach for assessing human exposures to chemical mixtures in the environment

    SciTech Connect

    Rice, Glenn MacDonell, Margaret; Hertzberg, Richard C.; Teuschler, Linda; Picel, Kurt; Butler, Jim; Chang, Young-Soo; Hartmann, Heidi

    2008-11-15

    Humans are exposed daily to multiple chemicals, including incidental exposures to complex chemical mixtures released into the environment and to combinations of chemicals that already co-exist in the environment because of previous releases from various sources. Exposures to chemical mixtures can occur through multiple pathways and across multiple routes. In this paper, we propose an iterative approach for assessing exposures to environmental chemical mixtures; it is similar to single-chemical approaches. Our approach encompasses two elements of the Risk Assessment Paradigm: Problem Formulation and Exposure Assessment. Multiple phases of the assessment occur in each element of the paradigm. During Problem Formulation, analysts identify and characterize the source(s) of the chemical mixture, ensure that dose-response and exposure assessment measures are concordant, and develop a preliminary evaluation of the mixture's fate. During Exposure Assessment, analysts evaluate the fate of the chemicals comprising the mixture using appropriate models and measurement data, characterize the exposure scenario, and estimate human exposure to the mixture. We also describe the utility of grouping the chemicals to be analyzed based on both physical-chemical properties and an understanding of environmental fate. In the article, we also highlight the need for understanding of changes in the mixture composition in the environment due to differential transport, differential degradation, and differential partitioning to other media. The section describes the application of the method to various chemical mixtures, highlighting issues associated with assessing exposures to chemical mixtures in the environment.

  20. Changes in the regulation of iodine crystals and chemical mixtures containing over 2.2 percent iodine. Final rule.

    PubMed

    2007-07-02

    This rulemaking changes the regulation of the listed chemical iodine under the chemical regulatory provisions of the Controlled Substances Act (CSA). The Drug Enforcement Administration (DEA) believes that this action is necessary to remove deficiencies in the existing regulatory controls, which have been exploited by drug traffickers who divert iodine (in the form of iodine crystals and iodine tincture) for the illicit production of methamphetamine in clandestine drug laboratories. This rulemaking moves iodine from List II to List I; reduces the iodine threshold from 0.4 kilograms to zero kilograms; adds import and export regulatory controls; and controls chemical mixtures containing greater than 2.2 percent iodine. This rulemaking establishes regulatory controls that will apply to iodine crystals and iodine chemical mixtures that contain greater than 2.2 percent iodine. This regulation therefore controls iodine crystals and strong iodine tinctures/solutions (e.g., 7 percent iodine) that do not have common household uses and instead have limited application in livestock, horses, and for disinfection of equipment. Household products such as 2 percent iodine tincture/solution and household disinfectants containing iodine complexes will not be adversely impacted by this regulation. Additionally, the final rule exempts transactions of up to one-fluid-ounce (30 ml) of Lugol's Solution. Persons handling regulated iodine materials are required to register with DEA, are subject to the import/export notification requirements of the CSA, and are required to maintain records of all regulated transactions involving iodine regardless of size.

  1. A FLEXIBLE APPROACH FOR EVALUATING FIXED RATIO MIXTURES OF FULL AND PARTIAL AGONISTS FOR MIXTURES OF MANY CHEMICALS.

    EPA Science Inventory

    Detecting interaction in chemical mixtures can be complicated by differences in the shapes of the dose-response curves of the individual components (e.g. mixtures of full and partial agonists with differing response maxima). We present an analysis scheme where flexible single che...

  2. 40 CFR 370.14 - How do I report mixtures containing hazardous chemicals?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 27 2010-07-01 2010-07-01 false How do I report mixtures containing...: COMMUNITY RIGHT-TO-KNOW Who Must Comply § 370.14 How do I report mixtures containing hazardous chemicals? (a) For a mixture containing a hazardous chemical, use the following table to determine if a...

  3. 40 CFR 370.14 - How do I report mixtures containing hazardous chemicals?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 28 2011-07-01 2011-07-01 false How do I report mixtures containing...: COMMUNITY RIGHT-TO-KNOW Who Must Comply § 370.14 How do I report mixtures containing hazardous chemicals? (a) For a mixture containing a hazardous chemical, use the following table to determine if a...

  4. 40 CFR 370.14 - How do I report mixtures containing hazardous chemicals?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 29 2013-07-01 2013-07-01 false How do I report mixtures containing...: COMMUNITY RIGHT-TO-KNOW Who Must Comply § 370.14 How do I report mixtures containing hazardous chemicals? (a) For a mixture containing a hazardous chemical, use the following table to determine if a...

  5. 40 CFR 370.14 - How do I report mixtures containing hazardous chemicals?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 29 2012-07-01 2012-07-01 false How do I report mixtures containing...: COMMUNITY RIGHT-TO-KNOW Who Must Comply § 370.14 How do I report mixtures containing hazardous chemicals? (a) For a mixture containing a hazardous chemical, use the following table to determine if a...

  6. 40 CFR 370.14 - How do I report mixtures containing hazardous chemicals?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 28 2014-07-01 2014-07-01 false How do I report mixtures containing...: COMMUNITY RIGHT-TO-KNOW Who Must Comply § 370.14 How do I report mixtures containing hazardous chemicals? (a) For a mixture containing a hazardous chemical, use the following table to determine if a...

  7. Polymer Exemption for New Chemicals under the Toxic Substances Control Act (TSCA)

    EPA Pesticide Factsheets

    EPA has established an exemption for certain polymers to encourage manufacturers to make safer polymers. To learn more about this exemption, eligibility, and it's requirements, read this overview of the exemption.

  8. Thermodynamic Analysis of Chemically Reacting Mixtures and Their Kinetics: Example of a Mixture of Three Isomers.

    PubMed

    Pekař, Miloslav

    2016-10-18

    Thermodynamics provides consequences of and restrictions on chemically reacting mixtures, particularly their kinetics, which have not been fully explored. Herein, a comprehensive thermodynamic analysis is illustrated for a reacting mixture of three isomers. The rate equation is first derived on the basis of the results of nonequilibrium continuum thermodynamics of linear fluids, and is then subjected to the requirement of consistency with entropic inequality (the second law). This consistency test involves the correct representation of the reaction rate as a function of affinities. It is shown that entropic inequality restricts the signs or values of coefficients in the constitutive equations for reaction rates/rate constants. The use of reverse rate constants and the identification of thermodynamic and kinetic equilibrium constants are not necessary in this approach. Although the presented thermodynamic analysis works only for independent reactions, the rates of dependent reactions are not excluded from having effects on kinetics. It is shown that the rates of dependent reactions are combined from the rates of independent reactions differently than dependent reactions are combined from independent reactions. The results are compared to the classical mass-action rate equations, and new restrictions on the values of the classical rate constants are derived.

  9. Bacterial mixture analysis with Raman chemical imaging microspectroscopy

    NASA Astrophysics Data System (ADS)

    Tripathi, Ashish; Jabbour, Rabih E.; Guicheteau, Jason A.; Christesen, Steven D.; Emge, Darren K.; Jensen, Janet L.; Snyder, A. Peter

    2009-05-01

    Raman chemical imaging microspectroscopy (RCIM) is being evaluated as a technology for waterborne pathogen detection. Binary and ternary mixtures including combinations of polystyrene beads, Grampositive Bacillus anthracis and B. atrophaeus spores, B. cereus vegetative cells, and Gram-negative E. coli cells were investigated by RCIM for differentiation and characterization purposes. We have demonstrated the ability of RCIM, in combination with Pearson's cross correlation and multivariate principal components analysis data reduction techniques, to differentiate these components in the same field of view (FOV). Conventional applications of RCIM consist of differentiating relatively broad areas in a FOV. Here, RCIM is expanded in its capabilities to differentiate and distinguish between different micron size species in single particles and clusters of mixed species.

  10. COMPLEX MIXTURES OF CHEMICAL CARCINOGENS: PRINCIPLES OF ACTION AND HUMAN CANCER

    EPA Science Inventory

    There is strong epidemiological evidence supported by experimental animal data that complex environmental mixtures pose a risk to human health producing increases in cancer incidence. Understanding the chemical and biological properties of these mixtures leads to a clearer unde...

  11. Sensing a Changing Chemical Mixture Using an Electronic Nose

    NASA Technical Reports Server (NTRS)

    Duong, Tuan; Ryan, Margaret

    2008-01-01

    A method of using an electronic nose to detect an airborne mixture of known chemical compounds and measure the temporally varying concentrations of the individual compounds is undergoing development. In a typical intended application, the method would be used to monitor the air in an inhabited space (e.g., the interior of a building) for the release of solvents, toxic fumes, and other compounds that are regarded as contaminants. At the present state of development, the method affords a capability for identifying and quantitating one or two compounds that are members of a set of some number (typically of the order of a dozen) known compounds. In principle, the method could be extended to enable monitoring of more than two compounds. An electronic nose consists of an array of sensors, typically made from polymer carbon composites, the electrical resistances of which change upon exposure to a variety of chemicals. By design, each sensor is unique in its responses to these chemicals: some or all of the sensitivities of a given sensor to the various vapors differ from the corresponding sensitivities of other sensors. In general, the responses of the sensors are nonlinear functions of the concentrations of the chemicals. Hence, mathematically, the monitoring problem is to solve the set of time-dependent nonlinear equations for the sensor responses to obtain the time dependent concentrations of individual compounds. In the present developmental method, successive approximations of the solution are generated by a learning algorithm based on independent-component analysis (ICA) an established information theoretic approach for transforming a vector of observed interdependent signals into a set of signals that are as nearly statistically independent as possible.

  12. Cumulative effects of anti-androgenic chemical mixtures and their relevance to human health risk assessment

    EPA Science Inventory

    Kembra L. Howdeshell and L. Earl Gray, Jr.Toxicological studies of defined chemical mixtures assist human health risk assessment by characterizing the joint action of chemicals. This presentation will review the effects of anti-androgenic chemical mixtures on reproductive tract d...

  13. Cumulative effects of anti-androgenic chemical mixtures and their relevance to human health risk assessment

    EPA Science Inventory

    Kembra L. Howdeshell and L. Earl Gray, Jr.Toxicological studies of defined chemical mixtures assist human health risk assessment by characterizing the joint action of chemicals. This presentation will review the effects of anti-androgenic chemical mixtures on reproductive tract d...

  14. A role of low dose chemical mixtures in adipose tissue in carcinogenesis.

    PubMed

    Lee, Duk-Hee; Jacobs, David R; Park, Ho Yong; Carpenter, David O

    2017-08-29

    The Halifax project recently hypothesized a composite carcinogenic potential of the mixture of low dose chemicals which are commonly encountered environmentally, yet which are not classified as human carcinogens. A long neglected but important fact is that adipose tissue is an important exposure source for chemical mixtures. In fact, findings from human studies based on several persistent organic pollutants in general populations with only background exposure should be interpreted from the viewpoint of chemical mixtures because serum concentrations of these chemicals can be seen as surrogates for chemical mixtures in adipose tissue. Furthermore, in conditions such as obesity with dysfunctional adipocytes or weight loss in which lipolysis is increased, the amount of the chemical mixture released from adipose tissue to circulation is increased. Thus, both obesity and weight loss can enhance the chance of chemical mixtures reaching critical organs, however paradoxical this idea may be when fat mass is the only factor considered. The complicated, interrelated dynamics of adipocytes and chemical mixtures can explain puzzling findings related to body weight among cancer patients, including the obesity paradox. The contamination of fat in human diet with chemical mixtures, occurring for reasons similar to contamination of human adipose tissue, may be a missing factor which affects the association between dietary fat intake and cancer. The presence of chemical mixtures in adipose tissue should be considered in future cancer research, including clinical trials on weight management among cancer survivors. Copyright © 2017. Published by Elsevier Ltd.

  15. Chemical Waste Management for the Conditionally Exempt Small Quantity Generator

    NASA Astrophysics Data System (ADS)

    Zimmer, Steven W.

    1999-06-01

    Management of hazardous chemical wastes generated as a part of the curriculum poses a significant task for the individual responsible for maintaining compliance with all rules and regulations from the Environmental Protection Agency and the Department of Transportation while maintaining the principles of OSHA's Lab Standard and the Hazard Communication Standard. For schools that generate relatively small quantities of waste, an individual can effectively manage the waste program without becoming overly burdened by the EPA regulations required for those generating large quantities of waste, if given the necessary support from the institution.

  16. International issues on human health effects of exposure to chemical mixtures.

    PubMed

    Feron, Victor J; Cassee, Flemming R; Groten, John P; van Vliet, Petronella W; van Zorge, Job A

    2002-12-01

    In this article, we highlight new developments and recent studies concerning adverse human health effects related to chemical mixtures. One group of activities comprises the development of a new computer program for analyzing mixture studies and a mathematical model as a basis for combination rules that predict the toxicity of mixtures. Other new activities in the area of experimental studies are the application of gene expression technologies in mixture research, and pattern recognition as a tool in safety evaluation of complex mixtures. A "bottom-up" approach for chemosensory detection of mixtures has recently been presented. Other topics include a method for the safety evaluation of natural flavoring complexes, and an evaluation of the possible health effects of the simultaneous intake of food additives. Examples of issues related to mixtures of airborne chemicals are potential interaction of fine particles and gaseous pollutants in ambient air, nasal cancer associated with inhaled chemical mixtures, and the recommendation of a limit value for volatile organic compounds. Topics of a more strategic nature include studies concerning the public health effects of large airports, and the development of criteria for a harmonized classification of chemical mixtures. This overview illustrates that strategies to tackle the safety evaluation of combined exposures and complex mixtures as well as models facilitating the interpretation of findings in the context of risk assessment of mixtures have become increasingly important. It is true that exposure of humans to chemical mixtures is the rule rather than the exception, and therefore health risk assessments should focus on mixtures and not on single chemicals. It is also true, however, that humans have learned to cope with exposure to huge numbers of chemicals simultaneously (food, water, air, soil, and consumer products). Therefore, in view of limited resources for toxicological research, the focus in toxicology should be

  17. International issues on human health effects of exposure to chemical mixtures.

    PubMed Central

    Feron, Victor J; Cassee, Flemming R; Groten, John P; van Vliet, Petronella W; van Zorge, Job A

    2002-01-01

    In this article, we highlight new developments and recent studies concerning adverse human health effects related to chemical mixtures. One group of activities comprises the development of a new computer program for analyzing mixture studies and a mathematical model as a basis for combination rules that predict the toxicity of mixtures. Other new activities in the area of experimental studies are the application of gene expression technologies in mixture research, and pattern recognition as a tool in safety evaluation of complex mixtures. A "bottom-up" approach for chemosensory detection of mixtures has recently been presented. Other topics include a method for the safety evaluation of natural flavoring complexes, and an evaluation of the possible health effects of the simultaneous intake of food additives. Examples of issues related to mixtures of airborne chemicals are potential interaction of fine particles and gaseous pollutants in ambient air, nasal cancer associated with inhaled chemical mixtures, and the recommendation of a limit value for volatile organic compounds. Topics of a more strategic nature include studies concerning the public health effects of large airports, and the development of criteria for a harmonized classification of chemical mixtures. This overview illustrates that strategies to tackle the safety evaluation of combined exposures and complex mixtures as well as models facilitating the interpretation of findings in the context of risk assessment of mixtures have become increasingly important. It is true that exposure of humans to chemical mixtures is the rule rather than the exception, and therefore health risk assessments should focus on mixtures and not on single chemicals. It is also true, however, that humans have learned to cope with exposure to huge numbers of chemicals simultaneously (food, water, air, soil, and consumer products). Therefore, in view of limited resources for toxicological research, the focus in toxicology should be

  18. Accurate prediction of the response of freshwater fish to a mixture of estrogenic chemicals.

    PubMed

    Brian, Jayne V; Harris, Catherine A; Scholze, Martin; Backhaus, Thomas; Booy, Petra; Lamoree, Marja; Pojana, Giulio; Jonkers, Niels; Runnalls, Tamsin; Bonfà, Angela; Marcomini, Antonio; Sumpter, John P

    2005-06-01

    Existing environmental risk assessment procedures are limited in their ability to evaluate the combined effects of chemical mixtures. We investigated the implications of this by analyzing the combined effects of a multicomponent mixture of five estrogenic chemicals using vitellogenin induction in male fathead minnows as an end point. The mixture consisted of estradiol, ethynylestradiol, nonylphenol, octylphenol, and bisphenol A. We determined concentration-response curves for each of the chemicals individually. The chemicals were then combined at equipotent concentrations and the mixture tested using fixed-ratio design. The effects of the mixture were compared with those predicted by the model of concentration addition using biomathematical methods, which revealed that there was no deviation between the observed and predicted effects of the mixture. These findings demonstrate that estrogenic chemicals have the capacity to act together in an additive manner and that their combined effects can be accurately predicted by concentration addition. We also explored the potential for mixture effects at low concentrations by exposing the fish to each chemical at one-fifth of its median effective concentration (EC50). Individually, the chemicals did not induce a significant response, although their combined effects were consistent with the predictions of concentration addition. This demonstrates the potential for estrogenic chemicals to act additively at environmentally relevant concentrations. These findings highlight the potential for existing environmental risk assessment procedures to underestimate the hazard posed by mixtures of chemicals that act via a similar mode of action, thereby leading to erroneous conclusions of absence of risk.

  19. Accurate Prediction of the Response of Freshwater Fish to a Mixture of Estrogenic Chemicals

    PubMed Central

    Brian, Jayne V.; Harris, Catherine A.; Scholze, Martin; Backhaus, Thomas; Booy, Petra; Lamoree, Marja; Pojana, Giulio; Jonkers, Niels; Runnalls, Tamsin; Bonfà, Angela; Marcomini, Antonio; Sumpter, John P.

    2005-01-01

    Existing environmental risk assessment procedures are limited in their ability to evaluate the combined effects of chemical mixtures. We investigated the implications of this by analyzing the combined effects of a multicomponent mixture of five estrogenic chemicals using vitellogenin induction in male fathead minnows as an end point. The mixture consisted of estradiol, ethynylestradiol, nonylphenol, octylphenol, and bisphenol A. We determined concentration–response curves for each of the chemicals individually. The chemicals were then combined at equipotent concentrations and the mixture tested using fixed-ratio design. The effects of the mixture were compared with those predicted by the model of concentration addition using biomathematical methods, which revealed that there was no deviation between the observed and predicted effects of the mixture. These findings demonstrate that estrogenic chemicals have the capacity to act together in an additive manner and that their combined effects can be accurately predicted by concentration addition. We also explored the potential for mixture effects at low concentrations by exposing the fish to each chemical at one-fifth of its median effective concentration (EC50). Individually, the chemicals did not induce a significant response, although their combined effects were consistent with the predictions of concentration addition. This demonstrates the potential for estrogenic chemicals to act additively at environmentally relevant concentrations. These findings highlight the potential for existing environmental risk assessment procedures to underestimate the hazard posed by mixtures of chemicals that act via a similar mode of action, thereby leading to erroneous conclusions of absence of risk. PMID:15929895

  20. Influence factors of multicomponent mixtures containing reactive chemicals and their joint effects.

    PubMed

    Tian, Dayong; Lin, Zhifen; Yu, Jianqiao; Yin, Daqiang

    2012-08-01

    Organic chemicals usually coexist as a mixture in the environment, and the mixture toxicity of organic chemicals has received increased attention. However, research regarding the joint effects of reactive chemicals is lacking. In this study, we examined two kinds of reactive chemicals, cyanogenic toxicants and aldehydes and determined their joint effects on Photobacterium phosphoreum. Three factors were found to influence the joint effects of multicomponent mixtures containing reactive chemicals, including the number of components, the dominating components and the toxic ratios. With an increased number of components, the synergistic or antagonistic effects (interactions) will weaken to the additive effects (non-interactions) if the added component cannot yield a much stronger joint effect with an existing component. Contrarily, the joint effect of the mixture may become stronger instead of weaker if the added components can yield a much stronger joint effect than the existing joint effect of the multicomponent mixture. The components that yield the strongest interactions in their binary mixture can be considered the dominating components. These components contribute more to the interactions of multicomponent mixtures than other components. Moreover, the toxic ratios also influence the joint effects of the mixtures. This study provides an insight into what are the main factors and how they influence the joint effects of multicomponent mixtures containing reactive chemicals, and thus, the findings are beneficial to the study of mixture toxicology. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Some critical issues and concerns related to research advances on toxicology of chemical mixtures.

    PubMed Central

    Yang, R S

    1998-01-01

    This paper addresses some of the issues and concerns on research advances on the toxicology of chemical mixtures. Emphases will be selectively given to the following questions and answers: Can mechanistic studies be conducted on chemical mixtures? The fact that any studies, including mechanistic studies, of single chemicals are really the study of the parent chemical plus its metabolites underscores the relevance of mechanistic studies on chemical mixtures. Can predictions be made on the health effects of chemical mixtures? Some successes are already evident in the literature on simpler chemical mixtures. For more complex mixtures, it is possible and we propose an approach here. What can we learn from other disciplines (the importance of interdisciplinary collaboration)? Two aspects, the knowledge and methodologies available in clinical pharmacology and the latest advances in structure-oriented lumping in chemical engineering, are discussed in detail. Unrepeatable results: The possibility of magnification of biologic variability because of low-level exposures to chemical mixtures is suggested with special reference to some known examples, including the controversial study on synergistic interactions of endocrine disruptors. Is the driving force for scientific investigations on chemical mixtures the legislative and regulatory atmosphere? Two laws with chemical mixtures specifically in the language are quoted and discussed. Their implications regarding research funding and activities are described. What are the pitfalls of applying for research funding on investigating chemical mixtures? The dilemma at least one investigator faces in pursuing research funding is elaborated. The questions and issues listed above are not all inclusive, but they represent some of the aspects that need to be brought into the open in the scientific community for discussion and/or debate. Thus, the primary objective of this paper is to provide some momentum for the beginning of a fruitful

  2. To which chemical mixtures is the French population exposed? Mixture identification from the second French Total Diet Study.

    PubMed

    Traoré, T; Béchaux, C; Sirot, V; Crépet, A

    2016-12-01

    Through their diet, humans are exposed to a wide range of substances with possible adverse effects. Total diet studies (TDS) assess exposure and risk for many single substances or mixtures from the same chemical family. This research aims to identify from 440 substances in the second French TDS, the major mixtures to which the French population is exposed and their associated diet. Firstly, substances with a contamination value over the detection limit were selected. Secondly, consumption systems comprising major consumed foods were identified using non-negative matrix factorisation and combined with concentration levels to form the main mixture. Thirdly, individuals were clustered to identify "diet clusters" with similar consumption patterns and co-exposure profiles. Six main consumption systems and their associated mixtures were identified. For example, a mixture of ten pesticides, six trace elements and bisphenol A was identified. Exposure to this mixture is related to fruit and vegetables consumed by a diet cluster comprising 62% of women with a mean age of 51 years. Six other clusters are described with their associated diets and mixtures. Cluster co-exposures were compared to the whole population. This work helps prioritise mixtures for which it is crucial to investigate possible toxicological effects.

  3. 75 FR 36306 - Chemical Mixtures Containing Listed Forms of Phosphorus and Change in Application Process

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-25

    ... chemical mixtures containing red phosphorus in a concentration of 80 percent or less and mixtures containing hypophosphorous acid and its salts (hypophosphite salts) in a concentration of 30 percent and less... subject to CSA chemical regulatory controls regardless of concentration. DEA recognizes that concentration...

  4. 30 CFR 47.92 - Exemptions from labeling.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... COMMUNICATION (HazCom) Exemptions § 47.92 Exemptions from labeling. A hazardous chemical is exempt from subpart... Chemicals Exempt from Labeling Exemption Conditions for exemption Chemical substance, consumer product... accordance with EPA regulations. Hazardous waste When regulated by EPA under the Solid Waste Disposal Act...

  5. 30 CFR 47.92 - Exemptions from labeling.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... COMMUNICATION (HazCom) Exemptions § 47.92 Exemptions from labeling. A hazardous chemical is exempt from subpart... Chemicals Exempt from Labeling Exemption Conditions for exemption Chemical substance, consumer product... accordance with EPA regulations. Hazardous waste When regulated by EPA under the Solid Waste Disposal Act...

  6. 30 CFR 47.92 - Exemptions from labeling.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... COMMUNICATION (HazCom) Exemptions § 47.92 Exemptions from labeling. A hazardous chemical is exempt from subpart... Chemicals Exempt from Labeling Exemption Conditions for exemption Chemical substance, consumer product... accordance with EPA regulations. Hazardous waste When regulated by EPA under the Solid Waste Disposal Act...

  7. Cumulative effects of antiandrogenic chemical mixtures and their relevance to human health risk assessment.

    PubMed

    Howdeshell, Kembra L; Hotchkiss, Andrew K; Gray, L Earl

    2016-11-19

    Toxicological studies of defined chemical mixtures assist human health risk assessment by establishing how chemicals interact with one another to induce an effect. This paper reviews how antiandrogenic chemical mixtures can alter reproductive tract development in rats with a focus on the reproductive toxicant phthalates. The reviewed studies compare observed mixture data to mathematical mixture model predictions based on dose addition or response addition to determine how the individual chemicals in a mixture interact (e.g., additive, greater, or less than additive). Phthalate mixtures were observed to act in a dose additive manner based on the relative potency of the individual phthalates to suppress fetal testosterone production. Similar dose additive effects have been reported for mixtures of phthalates with antiandrogenic pesticides of differing mechanisms of action. Overall, data from these phthalate experiments in rats can be used in conjunction with human biomonitoring data to determine individual hazard indices, and recent cumulative risk assessments in humans indicate an excess risk to antiandrogenic chemical mixtures that include phthalates only or phthalates in combination with other antiandrogenic chemicals.

  8. Software for analysis of chemical mixtures--composition, occurrence, distribution, and possible toxicity

    USGS Publications Warehouse

    Scott, Jonathon C.; Skach, Kenneth A.; Toccalino, Patricia L.

    2013-01-01

    The composition, occurrence, distribution, and possible toxicity of chemical mixtures in the environment are research concerns of the U.S. Geological Survey and others. The presence of specific chemical mixtures may serve as indicators of natural phenomena or human-caused events. Chemical mixtures may also have ecological, industrial, geochemical, or toxicological effects. Chemical-mixture occurrences vary by analyte composition and concentration. Four related computer programs have been developed by the National Water-Quality Assessment Program of the U.S. Geological Survey for research of chemical-mixture compositions, occurrences, distributions, and possible toxicities. The compositions and occurrences are identified for the user-supplied data, and therefore the resultant counts are constrained by the user’s choices for the selection of chemicals, reporting limits for the analytical methods, spatial coverage, and time span for the data supplied. The distribution of chemical mixtures may be spatial, temporal, and (or) related to some other variable, such as chemical usage. Possible toxicities optionally are estimated from user-supplied benchmark data. The software for the analysis of chemical mixtures described in this report is designed to work with chemical-analysis data files retrieved from the U.S. Geological Survey National Water Information System but can also be used with appropriately formatted data from other sources. Installation and usage of the mixture software are documented. This mixture software was designed to function with minimal changes on a variety of computer-operating systems. To obtain the software described herein and other U.S. Geological Survey software, visit http://water.usgs.gov/software/.

  9. Chemical thermodynamics of ultrasound speed in solutions and liquid mixtures.

    PubMed

    Reis, João Carlos R; Santos, Angela F S; Lampreia, Isabel M S

    2010-02-01

    A comprehensive formalism is developed to treat thermodynamically speed of ultrasound data for solutions and liquid mixtures. For solutions, the apparent speed of ultrasound of a solute is introduced and proposed to take the place of empirically defined quantities. The partial speed of ultrasound of a solute is defined and related to the partial molar volume and partial molar isentropic compression. For liquid mixtures, the concept of speed of sound before mixing pure liquids is presented and used to define the change in speed of ultrasound upon ideal mixing, which is predicted to be generally a negative quantity. A new thermodynamic equation is derived linking the values for excess speed of ultrasound, excess molar volume and excess molar isentropic compression of a mixture, and its applications are discussed. Ideal and excess apparent speeds of ultrasound, as well as ideal and excess partial speeds of ultrasound, are defined for substances making up a liquid mixture. Accurate speeds of ultrasound in 31 mixtures of water with the amphiphile 2-(ethylamino)ethanol at 293.15 K are reported. These data are used to demonstrate the ability of the apparent speed of ultrasound to describe the impact of solutes on sonic properties of solutions and the advantages of analysing thermodynamic properties of binary liquid mixtures in terms of the dependence on composition of Balankina's ratios between excess and ideal values. It is concluded that the new thermodynamic functions defined for speeds of ultrasound in solutions and liquid mixtures give, at the least, equivalent information on molecular aspects to the usual functions related to the isentropic compressibility, without needing density data for this purpose.

  10. Chemical kinetic modeling of component mixtures relevant to gasoline

    SciTech Connect

    Mehl, M; Curran, H J; Pitz, W J; Westbrook, C K

    2009-02-13

    Real fuels are complex mixtures of thousands of hydrocarbon compounds including linear and branched paraffins, naphthenes, olefins and aromatics. It is generally agreed that their behavior can be effectively reproduced by simpler fuel surrogates containing a limited number of components. In this work, a recently revised version of the kinetic model by the authors is used to analyze the combustion behavior of several components relevant to gasoline surrogate formulation. Particular attention is devoted to linear and branched saturated hydrocarbons (PRF mixtures), olefins (1-hexene) and aromatics (toluene). Model predictions for pure components, binary mixtures and multi-component gasoline surrogates are compared with recent experimental information collected in rapid compression machine, shock tube and jet stirred reactors covering a wide range of conditions pertinent to internal combustion engines. Simulation results are discussed focusing attention on the mixing effects of the fuel components.

  11. Chemical kinetic modeling of component mixtures relevant to gasoline

    SciTech Connect

    Mehl, M; Curran, H J; Pitz, W J; Dooley, S; Westbrook, C K

    2008-05-29

    Detailed kinetic models of pyrolysis and combustion of hydrocarbon fuels are nowadays widely used in the design of internal combustion engines and these models are effectively applied to help meet the increasingly stringent environmental and energetic standards. In previous studies by the combustion community, such models not only contributed to the understanding of pure component combustion, but also provided a deeper insight into the combustion behavior of complex mixtures. One of the major challenges in this field is now the definition and the development of appropriate surrogate models able to mimic the actual features of real fuels. Real fuels are complex mixtures of thousands of hydrocarbon compounds including linear and branched paraffins, naphthenes, olefins and aromatics. Their behavior can be effectively reproduced by simpler fuel surrogates containing a limited number of components. Aside the most commonly used surrogates containing iso-octane and n-heptane only, the so called Primary Reference Fuels (PRF), new mixtures have recently been suggested to extend the reference components in surrogate mixtures to also include alkenes and aromatics. It is generally agreed that, including representative species for all the main classes of hydrocarbons which can be found in real fuels, it is possible to reproduce very effectively in a wide range of operating conditions not just the auto-ignition propensity of gasoline or Diesel fuels, but also their physical properties and their combustion residuals [1]. In this work, the combustion behavior of several components relevant to gasoline surrogate formulation is computationally examined. The attention is focused on the autoignition of iso-octane, hexene and their mixtures. Some important issues relevant to the experimental and modeling investigation of such fuels are discussed with the help of rapid compression machine data and calculations. Following the model validation, the behavior of mixtures is discussed on the

  12. Systematic Proteomic Approach to Characterize the Impacts of Chemical Interactions on Protein and Cytotoxicity Responses to Metal Mixture Exposures

    EPA Science Inventory

    Chemical interactions have posed a big challenge in toxicity characterization and human health risk assessment of environmental mixtures. To characterize the impacts of chemical interactions on protein and cytotoxicity responses to environmental mixtures, we established a systems...

  13. Systematic Proteomic Approach to Characterize the Impacts of Chemical Interactions on Protein and Cytotoxicity Responses to Metal Mixture Exposures

    EPA Science Inventory

    Chemical interactions have posed a big challenge in toxicity characterization and human health risk assessment of environmental mixtures. To characterize the impacts of chemical interactions on protein and cytotoxicity responses to environmental mixtures, we established a systems...

  14. Biogeographical Analysis of Chemical Co-Occurrence Data to Identify Priorities for Mixtures Research

    EPA Science Inventory

    A challenge with multiple chemical risk assessment is the need to consider the joint behavior of chemicals in mixtures. To address this need, pharmacologists and toxicologists have developed methods over the years to evaluate and test chemical interaction. In practice, however, t...

  15. Biogeographical Analysis of Chemical Co-Occurrence Data to Identify Priorities for Mixtures Research

    EPA Science Inventory

    A challenge with multiple chemical risk assessment is the need to consider the joint behavior of chemicals in mixtures. To address this need, pharmacologists and toxicologists have developed methods over the years to evaluate and test chemical interaction. In practice, however, t...

  16. The underlying toxicological mechanism of chemical mixtures: a case study on mixture toxicity of cyanogenic toxicants and aldehydes to Photobacterium phosphoreum.

    PubMed

    Tian, Dayong; Lin, Zhifen; Zhou, Xianghong; Yin, Daqiang

    2013-10-15

    Intracellular chemical reaction of chemical mixtures is one of the main reasons that cause synergistic or antagonistic effects. However, it still remains unclear what the influencing factors on the intracellular chemical reaction are, and how they influence on the toxicological mechanism of chemical mixtures. To reveal this underlying toxicological mechanism of chemical mixtures, a case study on mixture toxicity of cyanogenic toxicants and aldehydes to Photobacterium phosphoreum was employed, and both their joint effects and mixture toxicity were observed. Then series of two-step linear regressions were performed to describe the relationships between joint effects, the expected additive toxicities and descriptors of individual chemicals (including concentrations, binding affinity to receptors, octanol/water partition coefficients). Based on the quantitative relationships, the underlying joint toxicological mechanisms were revealed. The result shows that, for mixtures with their joint effects resulting from intracellular chemical reaction, their underlying toxicological mechanism depends on not only their interaction with target proteins, but also their transmembrane actions and their concentrations. In addition, two generic points of toxicological mechanism were proposed including the influencing factors on intracellular chemical reaction and the difference of the toxicological mechanism between single reactive chemicals and their mixtures. This study provided an insight into the understanding of the underlying toxicological mechanism for chemical mixtures with intracellular chemical reaction.

  17. Automatic NMR-Based Identification of Chemical Reaction Types in Mixtures of Co-Occurring Reactions

    PubMed Central

    Latino, Diogo A. R. S.; Aires-de-Sousa, João

    2014-01-01

    The combination of chemoinformatics approaches with NMR techniques and the increasing availability of data allow the resolution of problems far beyond the original application of NMR in structure elucidation/verification. The diversity of applications can range from process monitoring, metabolic profiling, authentication of products, to quality control. An application related to the automatic analysis of complex mixtures concerns mixtures of chemical reactions. We encoded mixtures of chemical reactions with the difference between the 1H NMR spectra of the products and the reactants. All the signals arising from all the reactants of the co-occurring reactions were taken together (a simulated spectrum of the mixture of reactants) and the same was done for products. The difference spectrum is taken as the representation of the mixture of chemical reactions. A data set of 181 chemical reactions was used, each reaction manually assigned to one of 6 types. From this dataset, we simulated mixtures where two reactions of different types would occur simultaneously. Automatic learning methods were trained to classify the reactions occurring in a mixture from the 1H NMR-based descriptor of the mixture. Unsupervised learning methods (self-organizing maps) produced a reasonable clustering of the mixtures by reaction type, and allowed the correct classification of 80% and 63% of the mixtures in two independent test sets of different similarity to the training set. With random forests (RF), the percentage of correct classifications was increased to 99% and 80% for the same test sets. The RF probability associated to the predictions yielded a robust indication of their reliability. This study demonstrates the possibility of applying machine learning methods to automatically identify types of co-occurring chemical reactions from NMR data. Using no explicit structural information about the reactions participants, reaction elucidation is performed without structure elucidation of the

  18. Automatic NMR-based identification of chemical reaction types in mixtures of co-occurring reactions.

    PubMed

    Latino, Diogo A R S; Aires-de-Sousa, João

    2014-01-01

    The combination of chemoinformatics approaches with NMR techniques and the increasing availability of data allow the resolution of problems far beyond the original application of NMR in structure elucidation/verification. The diversity of applications can range from process monitoring, metabolic profiling, authentication of products, to quality control. An application related to the automatic analysis of complex mixtures concerns mixtures of chemical reactions. We encoded mixtures of chemical reactions with the difference between the (1)H NMR spectra of the products and the reactants. All the signals arising from all the reactants of the co-occurring reactions were taken together (a simulated spectrum of the mixture of reactants) and the same was done for products. The difference spectrum is taken as the representation of the mixture of chemical reactions. A data set of 181 chemical reactions was used, each reaction manually assigned to one of 6 types. From this dataset, we simulated mixtures where two reactions of different types would occur simultaneously. Automatic learning methods were trained to classify the reactions occurring in a mixture from the (1)H NMR-based descriptor of the mixture. Unsupervised learning methods (self-organizing maps) produced a reasonable clustering of the mixtures by reaction type, and allowed the correct classification of 80% and 63% of the mixtures in two independent test sets of different similarity to the training set. With random forests (RF), the percentage of correct classifications was increased to 99% and 80% for the same test sets. The RF probability associated to the predictions yielded a robust indication of their reliability. This study demonstrates the possibility of applying machine learning methods to automatically identify types of co-occurring chemical reactions from NMR data. Using no explicit structural information about the reactions participants, reaction elucidation is performed without structure elucidation of

  19. Genetic activity profiles in the testing and evaluation of chemical mixtures

    SciTech Connect

    Waters, M.D.; Claxton, L.D.; Stack, H.F.; Brady, A.L.; Graedel, T.E. )

    1990-01-01

    Some knowledge of the potential genetic activity of a complex environmental mixture may be gained from an assessment of the genetic activity of its component chemicals. The expanded Genetic Activity Profile (GAP) data base provides a computer-generated graphic representation of genetic bioassay data as a function of dose of the substance tested. In addition, the Atmospheric Chemical Compound (ACC) data-base contains information on chemical structures, properties, detection methods, and sources of chemicals found in ambient air. Using the combined data bases, the quantity of an individual chemical present within a mixture or fraction of a mixture may be related to the quantity (lowest effective dose, LED) of the chemical, by itself, required to demonstrate a positive response in one or more genetic bioassays. 19 references.

  20. Biologically-Based Lumping Methodology (BBLM) To Investigate Toxicological Interactions of Complex Chemical Mixtures

    EPA Science Inventory

    Many cases of environmental contamination result in concurrent or sequential exposure to more than one chemical. Limitations of available resources prevent experimental toxicology from providing health risk information about all the possible mixtures to which humans or other spec...

  1. MIXTURES OF THYROID DISRUPTING CHEMICALS: TESTING ADDITIVITY OF HEPATIC INDUCERS AND THYROID PEROXIDASE INHIBITORS.

    EPA Science Inventory

    Humans are exposed to chemical mixtures via diet, occupation, and the environment. Previous data demonstrated that low doses of polycyclic halogenated aromatic hydrocarbons (PHAHs) acting through similar mechanisms result in an additive reduction of thyroxine (T4). If xenobioti...

  2. Biologically-Based Lumping Methodology (BBLM) To Investigate Toxicological Interactions of Complex Chemical Mixtures

    EPA Science Inventory

    Many cases of environmental contamination result in concurrent or sequential exposure to more than one chemical. Limitations of available resources prevent experimental toxicology from providing health risk information about all the possible mixtures to which humans or other spec...

  3. MIXTURES OF THYROID DISRUPTING CHEMICALS: TESTING ADDITIVITY OF HEPATIC INDUCERS AND THYROID PEROXIDASE INHIBITORS.

    EPA Science Inventory

    Humans are exposed to chemical mixtures via diet, occupation, and the environment. Previous data demonstrated that low doses of polycyclic halogenated aromatic hydrocarbons (PHAHs) acting through similar mechanisms result in an additive reduction of thyroxine (T4). If xenobioti...

  4. Solutions of the chemical kinetic equations for initially inhomogeneous mixtures.

    NASA Technical Reports Server (NTRS)

    Hilst, G. R.

    1973-01-01

    Following the recent discussions by O'Brien (1971) and Donaldson and Hilst (1972) of the effects of inhomogeneous mixing and turbulent diffusion on simple chemical reaction rates, the present report provides a more extensive analysis of when inhomogeneous mixing has a significant effect on chemical reaction rates. The analysis is then extended to the development of an approximate chemical sub-model which provides much improved predictions of chemical reaction rates over a wide range of inhomogeneities and pathological distributions of the concentrations of the reacting chemical species. In particular, the development of an approximate representation of the third-order correlations of the joint concentration fluctuations permits closure of the chemical sub-model at the level of the second-order moments of these fluctuations and the mean concentrations.

  5. AQUATIC EXPOSURES OF CHEMICAL MIXTURES IN URBAN ENVIRONMENTS: APPROACHES TO IMPACT ASSESSMENT.

    PubMed

    de Zwart, Dick; Adams, William; Burgos, Malyka Galay; Hollender, Juliane; Junghans, Marion; Merrington, Graham; Muir, Derek; Parkerton, Thomas; De Schamphelaere, Karel; Whale, Graham; Williams, Richard

    2017-09-01

    Urban regions of the world are expanding rapidly, placing additional stress on water resources. Urban water bodies serve many purposes from washing and sources of drinking water to transport and conduits for storm drainage and effluent discharge. These water bodies receive chemical emissions arising from either single or multiple point sources, diffuse sources which can be continuous, intermittent or seasonal. Thus, aquatic organisms in these water bodies are exposed to temporally and compositionally variable mixtures. We have delineated source-specific signatures of these mixtures for diffuse urban runoff and urban point source exposure scenarios to support risk assessment and management of these mixtures. The first step in a tiered approach to assessing chemical exposure has been developed based on the Event Mean Concentration concept with chemical concentrations in runoff defined by volumes of water leaving each surface and the chemical exposure mixture profiles for different urban scenarios. Although generalizations can be made about the chemical composition of urban sources and event mean exposure predictions for initial prioritization, such modelling needs to be complemented with biological monitoring data. It is highly unlikely that the current paradigm of routine regulatory chemical monitoring alone will provide a realistic appraisal of urban aquatic chemical mixture exposures. Future consideration is also needed on the role of non-chemical stressors in such highly modified urban water bodies. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  6. 21 CFR 1309.25 - Temporary exemption from registration for chemical registration applicants.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... distribute, import, or export a combination ephedrine product is temporarily exempted from the registration... or import prescription drug products containing ephedrine, pseudoephedrine, or phenylpropanolamine...

  7. 21 CFR 1309.25 - Temporary exemption from registration for chemical registration applicants.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... distribute, import, or export a combination ephedrine product is temporarily exempted from the registration... or import prescription drug products containing ephedrine, pseudoephedrine, or phenylpropanolamine...

  8. 21 CFR 1309.25 - Temporary exemption from registration for chemical registration applicants.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... distribute, import, or export a combination ephedrine product is temporarily exempted from the registration... or import prescription drug products containing ephedrine, pseudoephedrine, or phenylpropanolamine...

  9. Agonistic sensory effects of airborne chemicals in mixtures: odor, nasal pungency, and eye irritation.

    PubMed

    Cometto-Muñiz, J E; Cain, W S; Hudnell, H K

    1997-07-01

    Thresholds responses of odor, nasal pungency (irritation), and eye irritation were measured for single chemicals (1-propanol, 1-hexanol, ethyl acetate, heptyl acetate, 2-pentanone, 2-heptanone, toluene, ethyl benzene, and propyl benzene) and mixtures of them (two three-component mixtures, two six-component mixtures, and one nine-component mixture). Nasal pungency was measured in subjects lacking a functional sense of smell (i.e., anosmics) to avoid interference from olfaction. Various degrees of stimulus agonism (additive effects) were observed for each of the three sensory channels when testing mixtures. As the number of components and the lipophilicity of such components in the mixtures decreased, so did the degree of agonism. Synergistic stimulus agonism characterized the eye-irritation response for the most complex (the nine-component) and the most lipophilic (one of the six-component) mixtures. Physicochemical properties play a large role in the determination of sensitivity to airborne chemicals, particularly to their ability to evoke irritation. While this has revealed itself previously with respect to single chemicals, it seems to have relevance to mixtures as well.

  10. Water quality objectives for mixtures of toxic chemicals: problems and perspectives.

    PubMed

    Vighi, M; Altenburger, R; Arrhenius, A; Backhaus, T; Bödeker, W; Blanck, H; Consolaro, F; Faust, M; Finizio, A; Froehner, K; Gramatica, P; Grimme, L H; Grönvall, F; Hamer, V; Scholze, M; Walter, H

    2003-02-01

    The need to develop water quality objectives not only for single substances but also for mixtures of chemicals seems evident. For that purpose, the conceptual basis could be the use of the two existing biometric models: concentration addition (CA) and independent action (IA), which is also called response addition. Both may allow calculation of the toxicity of mixtures of chemicals with similar modes of action (CA) or dissimilar modes of action (IA), respectively. The joint research project Prediction and Assessment of the Aquatic Toxicity of Mixtures of Chemicals (PREDICT) within the framework of the IVth Environment and Climate Programme of the European Commission, provided the opportunity to address (a) chemometric and QSAR criteria to classify substances as supposedly similarly or dissimilarly acting; (b) the predictive values of both models for the toxicity of mixtures at low, statistically nonsignificant effect concentrations of the individual components; and (c) the predictability of mixture toxicity at higher levels of biological complexity. In this article, the general outline, methodological approach, and some preliminary findings of PREDICT are presented. A procedure for classifying chemicals in relation to their structural and toxicological similarities has been developed. The predictive capabilities of CA and IA models have been demonstrated for single species and, to some extent, for multispecies testing. The role of very low effect concentrations in multiple mixtures has been evaluated. Problems and perspectives concerning the development of water quality objectives for mixtures are discussed.

  11. Chemical measures of similarity among disinfection by-product mixtures.

    PubMed

    Bull, Richard J; Rice, Glenn; Teuschler, Linda; Feder, Paul

    2009-01-01

    There are few measures that can be used to distinguish among mixtures of disinfection by-products (DBPs) produced in the chlorination or chloramination of drinking water. Objective measures of similarities among DBP mixtures would greatly simplify judgments about the risk that may be associated with exposure to DBPs in a given water supply. Major by-products of chlorination/chloramination include the trihalomethanes (THMs) and haloacetic acids (HAAs), which are routinely measured for compliance to regulations. A key question is whether measurement of similar amounts of these DBPs is indicative of the myriad other DBPs that are known to be produced. This article utilized data from a survey of 35 utilities in the United States that included several additional parameters, including members of the haloacetonitrile, trihaloacetaldehyde, and halopropanone classes. Based upon the distribution of bromine in the THM class, the concentrations of unmeasured brominated and bromochlorinated compounds could be determined. This allowed determination of whether measures of the THM and/or HAA classes reflected the amounts of these less abundant classes. Variations in relative yields among DBP classes were observed with water source type and with whether chlorine or chloramine was used as the disinfectant. However, most of the variability was attributable to geographic location. The relative abundance of brominated by-products also varied among water sources. Recent documentation that potent by-products, such as nitrosamines, are selectively produced in particular water systems and preferentially with chloramination indicates that more measures of individual DBP are needed to evaluate similarity among DBPs mixtures.

  12. Chemical equilibrium in high pressure molecular fluid mixtures

    SciTech Connect

    Shaw, M.S.

    1993-09-01

    The N{sub atoms}PT Monte Carlo simulation method has been reformulated to incorporate multiple species and chemical reactions with changes in total number of molecules. While maintaining a constant number of each type of atom, the number of molecules is changed by turning on and off the interactions of any particular position with other molecules. Chemical reactions are allowed as a correlated move of atoms to differnt molecular locations. Equilibrium chemical composition is determined as an average over the simulation along with equation of state quantities. A large set of simulations has been made with the system N{sub 2} + O{sub 2} {rightleftharpoons} NO covering a wide range in P and T. Both Hugoniot states and the CJ point have been determined and are shown to be sensitive to the potentials between unlike species.

  13. Impact of Chemical Proportions on the Acute Neurotoxicity of a Mixture of Seven Carbamates in Rats

    EPA Science Inventory

    Environmental exposures generally involve multiple chemicals and pathways, and statistical methodologies now exist to evaluate interactions among any number of chemicals in defined mixtures. N-methyl carbamate pesticides are presumed to act through a common mode of action, that i...

  14. NEUROBEHAVIORAL EVALUATIONS OF BINARY AND TERTIARY MIXTURES OF CHEMICALS: LESSIONS LEARNING.

    EPA Science Inventory

    The classical approach to the statistical analysis of binary chemical mixtures is to construct full dose-response curves for one compound in the presence of a range of doses of the second compound (isobolographic analyses). For interaction studies using more than two chemicals, ...

  15. Impact of Chemical Proportions on the Acute Neurotoxicity of a Mixture of Seven Carbamates in Rats

    EPA Science Inventory

    Environmental exposures generally involve multiple chemicals and pathways, and statistical methodologies now exist to evaluate interactions among any number of chemicals in defined mixtures. N-methyl carbamate pesticides are presumed to act through a common mode of action, that i...

  16. NEUROBEHAVIORAL EVALUATIONS OF BINARY AND TERTIARY MIXTURES OF CHEMICALS: LESSIONS LEARNING.

    EPA Science Inventory

    The classical approach to the statistical analysis of binary chemical mixtures is to construct full dose-response curves for one compound in the presence of a range of doses of the second compound (isobolographic analyses). For interaction studies using more than two chemicals, ...

  17. Growth of Daphnia magna exposed to mixtures of chemicals with diverse modes of action

    SciTech Connect

    Deneer, J.W.; Seinen, W.; Hermens, J.L.

    1988-02-01

    Concentrations causing inhibition of growth of Daphnia magna after 16 days of exposure were determined for nine chemicals that presumably act through different modes of action. The joint toxic effect of a mixture of these chemicals is found to be nonadditive.

  18. Identifying Prevalent Chemical Mixtures in the US Population

    EPA Science Inventory

    Through the food and water they ingest, the air they breathe, and the consumer products with which they interact at home and at work, humans are exposed to tens of thousands of chemicals, many of which have not been evaluated to determine their potential toxicities. In recent yea...

  19. Evaluating quantitative formulas for dose-response assessment of chemical mixtures.

    PubMed

    Hertzberg, Richard C; Teuschler, Linda K

    2002-12-01

    Risk assessment formulas are often distinguished from dose-response models by being rough but necessary. The evaluation of these rough formulas is described here, using the example of mixture risk assessment. Two conditions make the dose-response part of mixture risk assessment difficult, lack of data on mixture dose-response relationships, and the need to address risk from combinations of chemicals because of public demands and statutory requirements. Consequently, the U.S. Environmental Protection Agency has developed methods for carrying out quantitative dose-response assessment for chemical mixtures that require information only on the toxicity of single chemicals and of chemical pair interactions. These formulas are based on plausible ideas and default parameters but minimal supporting data on whole mixtures. Because of this lack of mixture data, the usual evaluation of accuracy (predicted vs. observed) cannot be performed. Two approaches to the evaluation of such formulas are to consider fundamental biological concepts that support the quantitative formulas (e.g., toxicologic similarity) and to determine how well the proposed method performs under simplifying constraints (e.g., as the toxicologic interactions disappear). These ideas are illustrated using dose addition and two weight-of-evidence formulas for incorporating toxicologic interactions.

  20. A generalized physiologically-based toxicokinetic modeling system for chemical mixtures containing metals

    PubMed Central

    2010-01-01

    Background Humans are routinely and concurrently exposed to multiple toxic chemicals, including various metals and organics, often at levels that can cause adverse and potentially synergistic effects. However, toxicokinetic modeling studies of exposures to these chemicals are typically performed on a single chemical basis. Furthermore, the attributes of available models for individual chemicals are commonly estimated specifically for the compound studied. As a result, the available models usually have parameters and even structures that are not consistent or compatible across the range of chemicals of concern. This fact precludes the systematic consideration of synergistic effects, and may also lead to inconsistencies in calculations of co-occurring exposures and corresponding risks. There is a need, therefore, for a consistent modeling framework that would allow the systematic study of cumulative risks from complex mixtures of contaminants. Methods A Generalized Toxicokinetic Modeling system for Mixtures (GTMM) was developed and evaluated with case studies. The GTMM is physiologically-based and uses a consistent, chemical-independent physiological description for integrating widely varying toxicokinetic models. It is modular and can be directly "mapped" to individual toxicokinetic models, while maintaining physiological consistency across different chemicals. Interaction effects of complex mixtures can be directly incorporated into the GTMM. Conclusions The application of GTMM to different individual metals and metal compounds showed that it explains available observational data as well as replicates the results from models that have been optimized for individual chemicals. The GTMM also made it feasible to model toxicokinetics of complex, interacting mixtures of multiple metals and nonmetals in humans, based on available literature information. The GTMM provides a central component in the development of a "source-to-dose-to-effect" framework for modeling

  1. The underlying toxicological mechanism of chemical mixtures: A case study on mixture toxicity of cyanogenic toxicants and aldehydes to Photobacterium phosphoreum

    SciTech Connect

    Tian, Dayong; Lin, Zhifen; Zhou, Xianghong; Yin, Daqiang

    2013-10-15

    Intracellular chemical reaction of chemical mixtures is one of the main reasons that cause synergistic or antagonistic effects. However, it still remains unclear what the influencing factors on the intracellular chemical reaction are, and how they influence on the toxicological mechanism of chemical mixtures. To reveal this underlying toxicological mechanism of chemical mixtures, a case study on mixture toxicity of cyanogenic toxicants and aldehydes to Photobacterium phosphoreum was employed, and both their joint effects and mixture toxicity were observed. Then series of two-step linear regressions were performed to describe the relationships between joint effects, the expected additive toxicities and descriptors of individual chemicals (including concentrations, binding affinity to receptors, octanol/water partition coefficients). Based on the quantitative relationships, the underlying joint toxicological mechanisms were revealed. The result shows that, for mixtures with their joint effects resulting from intracellular chemical reaction, their underlying toxicological mechanism depends on not only their interaction with target proteins, but also their transmembrane actions and their concentrations. In addition, two generic points of toxicological mechanism were proposed including the influencing factors on intracellular chemical reaction and the difference of the toxicological mechanism between single reactive chemicals and their mixtures. This study provided an insight into the understanding of the underlying toxicological mechanism for chemical mixtures with intracellular chemical reaction. - Highlights: • Joint effects of nitriles and aldehydes at non-equitoxic ratios were determined. • A novel descriptor, ligand–receptor interaction energy (E{sub binding}), was employed. • Quantitative relationships for mixtures were developed based on a novel descriptor. • The underlying toxic mechanism was revealed based on quantitative relationships. • Two

  2. Chemical constituents of marijuana: the complex mixture of natural cannabinoids.

    PubMed

    Elsohly, Mahmoud A; Slade, Desmond

    2005-12-22

    The cannabis plant (Cannabis sativa L.) and products thereof (such as marijuana, hashish and hash oil) have a long history of use both as a medicinal agent and intoxicant. Over the last few years there have been an active debate regarding the medicinal aspects of cannabis. Currently cannabis products are classified as Schedule I drugs under the Drug Enforcement Administration (DEA) Controlled Substances act, which means that the drug is only available for human use as an investigational drug. In addition to the social aspects of the use of the drug and its abuse potential, the issue of approving it as a medicine is further complicated by the complexity of the chemical make up of the plant. This manuscript discusses the chemical constituents of the plant with particular emphasis on the cannabinoids as the class of compounds responsible for the drug's psychological properties.

  3. Acute mixture toxicity of halogenated chemicals and their next generation counterparts on zebrafish embryos.

    PubMed

    Godfrey, Amy; Abdel-Moneim, Ahmed; Sepúlveda, Maria S

    2017-08-01

    Perfluorinated chemicals and flame retardants are halogenated compounds commonly used in food packaging and in clothing and electronics, respectively. Due to the hazardous effects of many of these chemicals, manufacturers are developing next generation potential less toxic alternatives. The objective of this study was to assess the toxicity of potentially "safer" alternatives, singly and in mixtures, in relation to their first generation counterparts. We used zebrafish embryos as our model organism due to its high structural and functional homology to other vertebrates and its suitability for early developmental studies. We tested three well studied halogens, perfluorooctanoic acid (PFOA), tris (1,3-dichloro-2-propyl) phosphate (TDCPP) and tetrabromobisphenal A (TBBPA), and two less-studied next generation chemicals, 9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and perfluorobutyric acid (PFBA). First, we identified their lethal concentration (LC50) under 96 h exposures using zebrafish embryos; chemical LC50 values ranged from 1.3 to 13,795 ppm. Next, we tested the toxicity of tertiary mixtures containing the estimated LC50 values for each chemical which ranged from 126 to 5,094 ppm. We found that chemicals within these mixtures displayed concentration addition suggesting a similar mode of toxic action. Importantly, next generation chemicals were less acutely toxic singly and in mixtures than their first generation counterpart. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... with U.S. Department of Transportation Special Permit No. 6029 as a calibration test kit for methane monitoring systems, shall be exempt from the requirements of §§ 75.1106-2(c) and 75.1106-4(d), (f) and...

  5. Chemical mixtures: Evaluation of risk for child-specific exposures in a multi-stressor environment

    SciTech Connect

    Pohl, H.R. Abadin, H.G.

    2008-11-15

    Evaluating the health impact from exposure to chemical mixtures is multifaceted. One component is exposure. Exposure, and consequently risk assessment for mixtures and chemicals in general, are often viewed in terms of a given exposure to a given population at a given location over a given time period. However, environmental exposures are present throughout human lifetime. As a result, an evaluation of risk must include the distinctive characteristics related to chemical exposures which will impact risk depending upon the particular life stage where exposure occurs. Risks to offspring may be associated with unique exposures in utero, during infancy, childhood, or adolescent periods. For example, exposure of infants to anthropogenic chemicals via breast milk may be of concern. The Agency for Toxic Substances and Disease Registry's (ATSDR's) approach to evaluating risks associated with exposure to mixtures of chemicals is presented. In addition to the breast milk issues, indoor exposure to combined air pollutants, drinking water contaminants, and soil and dust contaminants are discussed. The difference between a mixture's risk evaluation for children and adults is in the distinct exposure scenarios resulting from variations in behavior, physiology, and/or pharmacokinetics between adults and children rather than in the method for the specific mixtures evaluation per se.

  6. Overview of human health and chemical mixtures: problems facing developing countries.

    PubMed Central

    Yáñ ez, Leticia; Ortiz, Deogracias; Calderón, Jaqueline; Batres, Lilia; Carrizales, Leticia; Mejía, Jesús; Martínez, Lourdes; García-Nieto, Edelmira; Díaz-Barriga, Fernando

    2002-01-01

    In developing countries, chemical mixtures within the vicinity of small-scale enterprises, smelters, mines, agricultural areas, toxic waste disposal sites, etc., often present a health hazard to the populations within those vicinities. Therefore, in these countries, there is a need to study the toxicological effects of mixtures of metals, pesticides, and organic compounds. However, the study of mixtures containing substances such as DDT (dichlorodiphenyltrichloroethane, an insecticide banned in developed nations), and mixtures containing contaminants such as fluoride (of concern only in developing countries) merit special attention. Although the studies may have to take into account simultaneous exposures to metals and organic compounds, there is also a need to consider the interaction between chemicals and other specific factors such as nutritional conditions, alcoholism, smoking, infectious diseases, and ethnicity. PMID:12634117

  7. Study of sensory diversity and redundancy to encode for chemical mixtures

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Gálvez, Agustín; Fernandez, Luis; Marco, Santiago

    2011-09-01

    Inspired by sensory diversity and redundancy at the olfactory epithelium, we have built a large chemical sensor array based on commercial MOX sensors. Different sensor families along with temperature modulation accounts for sensory diversity, whereas sensors of the same family combined with different load resistors provide redundancy to the system. To study the encoding of odor mixtures, a data collection consisting on the response of the array to 3 binary mixtures of ethanol, acetone, and butanone with 18 different concentration ratios is obtained.

  8. TNT Equivalency Testing of Chemical Mixtures in Continuous TNT Manufacturing

    DTIC Science & Technology

    1980-08-01

    hemisphere 122 Figure Page 63 CAL-7 C-4 verification test, 18.75 kg (41.3 lb) hemisphere 124 64 CAL-8 Solid TNT cylinder calibration test, L/D...chemicals from an active TNT line, such as at Joliet AAP or Volunteer AAP. 2. Use cold nitrating acid and solid TNT flakes dispersed in the acid. 3... solid TNT flakes in the acid. The flakes would get caught in the mock cooling coils and block flow. The flakes would disperse differently than

  9. 40 CFR 790.87 - Approval of exemption applications.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 33 2013-07-01 2013-07-01 false Approval of exemption applications. 790.87 Section 790.87 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC... chemical substance or mixture with respect to which the application was submitted is equivalent to a...

  10. CHANGES IN HIPPOCAMPAL SPINE DENSITY AND PROTEIN KINASE C ISOFORMS FOLLOWING DEVELOPMENTAL EXPOSURE TO A MIXTURE OF PERSISTENT CHEMICALS.

    EPA Science Inventory

    Polychlorinated biphenyls (PCBs) offer a unique model to understand the major issues related to complex environmental mixtures of persistent chemicals. These pollutants are ubiquitous, persistent, bioaccumulate in human body through the food chain, and exist as mixtures of severa...

  11. CHANGES IN HIPPOCAMPAL SPINE DENSITY AND PROTEIN KINASE C ISOFORMS FOLLOWING DEVELOPMENTAL EXPOSURE TO A MIXTURE OF PERSISTENT CHEMICALS.

    EPA Science Inventory

    Polychlorinated biphenyls (PCBs) offer a unique model to understand the major issues related to complex environmental mixtures of persistent chemicals. These pollutants are ubiquitous, persistent, bioaccumulate in human body through the food chain, and exist as mixtures of severa...

  12. Chemical contaminants on DOE lands and selection of contaminant mixtures for subsurface science research

    SciTech Connect

    Riley, R.G.; Zachara, J.M.

    1992-04-01

    This report identifies individual contaminants and contaminant mixtures that have been measured in the ground at 91 waste sites at 18 US Department of Energy (DOE) facilities within the weapons complex. The inventory of chemicals and mixtures was used to identify generic chemical mixtures to be used by DOE`s Subsurface Science Program in basic research on the subsurface geochemical and microbiological behavior of mixed contaminants (DOE 1990a and b). The generic mixtures contain specific radionuclides, metals, organic ligands, organic solvents, fuel hydrocarbons, and polychlorinated biphenyls (PCBs) in various binary and ternary combinations. The mixtures are representative of in-ground contaminant associations at DOE facilities that are likely to exhibit complex geochemical behavior as a result of intercontaminant reactions and/or microbiologic activity stimulated by organic substances. Use of the generic mixtures will focus research on important mixed contaminants that are likely to be long-term problems at DOE sites and that will require cleanup or remediation. The report provides information on the frequency of associations among different chemicals and compound classes at DOE waste sites that require remediation.

  13. Chemical contaminants on DOE lands and selection of contaminant mixtures for subsurface science research

    SciTech Connect

    Riley, R.G.; Zachara, J.M. )

    1992-04-01

    This report identifies individual contaminants and contaminant mixtures that have been measured in the ground at 91 waste sites at 18 US Department of Energy (DOE) facilities within the weapons complex. The inventory of chemicals and mixtures was used to identify generic chemical mixtures to be used by DOE's Subsurface Science Program in basic research on the subsurface geochemical and microbiological behavior of mixed contaminants (DOE 1990a and b). The generic mixtures contain specific radionuclides, metals, organic ligands, organic solvents, fuel hydrocarbons, and polychlorinated biphenyls (PCBs) in various binary and ternary combinations. The mixtures are representative of in-ground contaminant associations at DOE facilities that are likely to exhibit complex geochemical behavior as a result of intercontaminant reactions and/or microbiologic activity stimulated by organic substances. Use of the generic mixtures will focus research on important mixed contaminants that are likely to be long-term problems at DOE sites and that will require cleanup or remediation. The report provides information on the frequency of associations among different chemicals and compound classes at DOE waste sites that require remediation.

  14. Mixtures of environmentally relevant endocrine disrupting chemicals affect mammary gland development in female and male rats.

    PubMed

    Mandrup, Karen Riiber; Johansson, Hanna Katarina Lilith; Boberg, Julie; Pedersen, Anne Stilling; Mortensen, Mette Sidsel; Jørgensen, Jennifer Solgaard; Vinggaard, Anne Marie; Hass, Ulla

    2015-07-01

    Estrogenic chemicals are able to alter mammary gland development in female rodents, but little is known on the effects of anti-androgens and mixtures of endocrine disrupting chemicals (EDCs) with dissimilar modes of action. Pregnant rat dams were exposed during gestation and lactation to mixtures of environmentally relevant EDCs with estrogenic, anti-androgenic or dissimilar modes of action (TotalMix) of 100-, 200- or 450-fold high end human intake estimates. Mammary glands of prepubertal and adult female and male offspring were examined. Oestrogens increased mammary outgrowth in prepubertal females and the mRNA level of matrix metalloproteinase-3, which may be a potential biomarker for increased outgrowth. Mixtures of EDCs gave rise to ductal hyperplasia in adult males. Adult female mammary glands of the TotalMix group showed morphological changes possibly reflecting increased prolactin levels. In conclusion both estrogenic and anti-androgenic chemicals given during foetal life and lactation affected mammary glands in the offspring.

  15. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... containing nonflammable or nonexplosive gas mixtures. 75.1106-6 Section 75.1106-6 Mineral Resources MINE... containing nonflammable or nonexplosive gas mixtures. Small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures, which provide for the emission of such gas under a pressure...

  16. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... containing nonflammable or nonexplosive gas mixtures. 75.1106-6 Section 75.1106-6 Mineral Resources MINE... containing nonflammable or nonexplosive gas mixtures. Small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures, which provide for the emission of such gas under a pressure...

  17. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... containing nonflammable or nonexplosive gas mixtures. 75.1106-6 Section 75.1106-6 Mineral Resources MINE... containing nonflammable or nonexplosive gas mixtures. Small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures, which provide for the emission of such gas under a pressure...

  18. 30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... containing nonflammable or nonexplosive gas mixtures. 75.1106-6 Section 75.1106-6 Mineral Resources MINE... containing nonflammable or nonexplosive gas mixtures. Small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures, which provide for the emission of such gas under a pressure...

  19. Should the scope of human mixture risk assessment span legislative/regulatory silos for chemicals?

    PubMed

    Evans, Richard M; Martin, Olwenn V; Faust, Michael; Kortenkamp, Andreas

    2016-02-01

    Current chemicals regulation operates almost exclusively on a chemical-by-chemical basis, however there is concern that this approach may not be sufficiently protective if two or more chemicals have the same toxic effect. Humans are indisputably exposed to more than one chemical at a time, for example to the multiple chemicals found in food, air and drinking water, and in household and consumer products, and in cosmetics. Assessment of cumulative risk to human health and/or the environment from multiple chemicals and routes can be done in a mixture risk assessment (MRA). Whilst there is a broad consensus on the basic science of mixture toxicology, the path to regulatory implementation of MRA within chemical risk assessment is less clear. In this discussion piece we pose an open question: should the scope of human MRA cross legislative remits or 'silos'? We define silos as, for instance, legislation that defines risk assessment practice for a subset of chemicals, usually on the basis of substance/product, media or process orientation. Currently any form of legal mandate for human MRA in the EU is limited to only a few pieces of legislation. We describe two lines of evidence, illustrated with selected examples, that are particularly pertinent to this question: 1) evidence that mixture effects have been shown for chemicals regulated in different silos and 2) evidence that humans are co-exposed to chemicals from different silos. We substantiate the position that, because there is no reason why chemicals allocated to specific regulatory silos would have non-overlapping risk profiles, then there is also no reason to expect that MRA limited only to chemicals within one silo can fully capture the risk that may be present to human consumers. Finally, we discuss possible options for implementation of MRA and we hope to prompt wider discussion of this issue.

  20. Insights into synergistic interactions in binary mixtures of chemical permeation enhancers for transdermal drug delivery.

    PubMed

    Karande, Pankaj; Jain, Amit; Mitragotri, Samir

    2006-09-28

    Chemical permeation enhancers (CPEs) are known to increase skin permeability to therapeutic drugs. Single chemicals, however, offer limited enhancements of skin permeability. Mixtures of chemicals can overcome this limitation owing to their synergistic interactions. However, identification of potent mixtures of chemicals requires screening of a large number of formulations. Discovery of CPE mixtures can be significantly accelerated by identifying patterns that occur in the existing data on CPEs. In this study, we systematically mine through a huge database on skin permeabilizing effect of over 4000 binary formulations generated by high throughput screening and extract general principles that govern the effect of binary combinations of chemicals on skin's barrier properties. Potencies and synergies of these formulations are analyzed to identify the role played by the formulation composition and chemistry. The analysis reveals several intuitive but some largely non-intuitive trends. For example, formulations made from enhancer mixtures are most potent when participating moieties are present in nearly equal fractions. Methyl pyrrolidone, a small molecule, is particularly effective in forming potent and synergistic enhancer formulations, and zwitterionic surfactants are more likely to feature in potent enhancers. Simple but invaluable rules like these will provide guiding principles for designing libraries to further speed up the formulation discovery process.

  1. Considering the cumulative risk of mixtures of chemicals – A challenge for policy makers

    PubMed Central

    2012-01-01

    Background The current paradigm for the assessment of the health risk of chemical substances focuses primarily on the effects of individual substances for determining the doses of toxicological concern in order to inform appropriately the regulatory process. These policy instruments place varying requirements on health and safety data of chemicals in the environment. REACH focuses on safety of individual substances; yet all the other facets of public health policy that relate to chemical stressors put emphasis on the effects of combined exposure to mixtures of chemical and physical agents. This emphasis brings about methodological problems linked to the complexity of the respective exposure pathways; the effect (more complex than simple additivity) of mixtures (the so-called 'cocktail effect'); dose extrapolation, i.e. the extrapolation of the validity of dose-response data to dose ranges that extend beyond the levels used for the derivation of the original dose-response relationship; the integrated use of toxicity data across species (including human clinical, epidemiological and biomonitoring data); and variation in inter-individual susceptibility associated with both genetic and environmental factors. Methods In this paper we give an overview of the main methodologies available today to estimate the human health risk of environmental chemical mixtures, ranging from dose addition to independent action, and from ignoring interactions among the mixture constituents to modelling their biological fate taking into account the biochemical interactions affecting both internal exposure and the toxic potency of the mixture. Results We discuss their applicability, possible options available to policy makers and the difficulties and potential pitfalls in implementing these methodologies in the frame of the currently existing policy framework in the European Union. Finally, we suggest a pragmatic solution for policy/regulatory action that would facilitate the evaluation of

  2. Initial analyses of the relationship between 'Thresholds' of toxicity for individual chemicals and 'Interaction Thresholds' for chemical mixtures

    SciTech Connect

    Yang, Raymond S.H. Dennison, James E.

    2007-09-01

    The inter-relationship of 'Thresholds' between chemical mixtures and their respective component single chemicals was studied using three sets of data and two types of analyses. Two in vitro data sets involve cytotoxicity in human keratinocytes from treatment of metals and a metal mixture [Bae, D.S., Gennings, C., Carter, Jr., W.H., Yang, R.S.H., Campain, J.A., 2001. Toxicological interactions among arsenic, cadmium, chromium, and lead in human keratinocytes. Toxicol. Sci. 63, 132-142; Gennings, C., Carter, Jr., W.H., Campain, J.A., Bae, D.S., Yang, R.S.H., 2002. Statistical analysis of interactive cytotoxicity in human epidermal keratinocytes following exposure to a mixture of four metals. J. Agric. Biol. Environ. Stat. 7, 58-73], and induction of estrogen receptor alpha (ER-{alpha}) reporter gene in MCF-7 human breast cancer cells by estrogenic xenobiotics [Gennings, C., Carter, Jr., W.H., Carney, E.W., Charles, G.D., Gollapudi, B.B., Carchman, R.A., 2004. A novel flexible approach for evaluating fixed ratio mixtures of full and partial agonists. Toxicol. Sci. 80, 134-150]. The third data set came from PBPK modeling of gasoline and its components in the human. For in vitro cellular responses, we employed Benchmark Dose Software (BMDS) to obtain BMD{sub 01}, BMD{sub 05}, and BMD{sub 10}. We then plotted these BMDs against exposure concentrations for the chemical mixture and its components to assess the ranges and slopes of these BMD-concentration lines. In doing so, we consider certain BMDs to be 'Interaction Thresholds' or 'Thresholds' for mixtures and their component single chemicals and the slope of the line must be a reflection of the potency of the biological effects. For in vivo PBPK modeling, we used 0.1x TLVs, TLVs, and 10x TLVs for gasoline and six component markers as input dosing for PBPK modeling. In this case, the venous blood levels under the hypothetical exposure conditions become our designated 'Interaction Thresholds' or 'Thresholds' for gasoline

  3. Role of deliquescence lowering in enhancing chemical reactivity in physical mixtures.

    PubMed

    Salameh, Adnan K; Taylor, Lynne S

    2006-05-25

    Mixtures of deliquescent solids are susceptible to deliquescence lowering, where water vapor condensation occurs in mixtures at a lower critical relative humidity (RH(0mix)) than individual component critical relative humidities (RH(0)s). The purpose of this study was to evaluate the effect of deliquescence lowering on chemical reactivity. Sucrose, citric acid and their physical mixtures were characterized using vapor sorption analysis to determine RH(0) and RH(0mix). Acid-catalyzed sucrose hydrolysis kinetics was determined using polarimetric analysis. Physical mixtures of sucrose and citric acid crystals were prepared and stored at various relative humidities at 22 degrees C. For these physical mixtures, sucrose hydrolysis was found to occur only when the environmental RH exceeded RH(0mix). Degradation kinetics correlated with the storage RH, being fastest at higher RH. In addition, a lag period was initially observed, which was most prominent for samples stored close to RH(0mix). With exposure to RHs below RH(0mix), no sucrose degradation was detected over the experimental time period. In conclusion, mixtures of deliquescent solids showed increased water sorption at lower RHs, which caused solid dissolution and subsequently led to an increase in the chemical reactivity.

  4. Chemical-specific health consultation for chromated copper arsenate chemical mixture: port of Djibouti.

    PubMed

    Chou, Selene; Colman, Joan; Tylenda, Carolyn; De Rosa, Christopher

    2007-05-01

    The Agency for Toxic Substances and Disease Registry (ATSDR) prepared this health consultation to provide support for assessing the public health implications of hazardous chemical exposure, primarily through drinking water, related to releases of chromated copper arsenate (CCA) in the port of Djibouti. CCA from a shipment, apparently intended for treating electric poles, is leaking into the soil in the port area. CCA is a pesticide used to protect wood against decay-causing organisms. This mixture commonly contains chromium(VI) (hexavalent chromium) as chromic acid, arsenic(V) (pentavalent arsenic) as arsenic pentoxide and copper (II) (divalent copper) as cupric oxide, often in an aqueous solution or concentrate. Experimental studies of the fate of CCA in soil and monitoring studies of wood-preserving sites where CCA was spilled on the soil indicate that the chromium(VI), arsenic and copper components of CCA can leach from soil into groundwater and surface water. In addition, at CCA wood-preserving sites, substantial concentrations of chromium(VI), arsenic and copper remained in the soil and were leachable into water four years after the use of CCA was discontinued, suggesting prolonged persistence in soil, with continued potential for leaching. The degree of leaching depended on soil composition and the extent of soil contamination with CCA. In general, leaching was highest for chromium(VI), intermediate for arsenic and lowest for copper. Thus, the potential for contamination of sources of drinking water exists. Although arsenic that is leached from CCA-contaminated soil into surface water may accumulate in the tissues of fish and shellfish, most of the arsenic in these animals will be in a form (often called fish arsenic) that is less harmful. Copper, which leaches less readily than the other components, can accumulate in tissues of mussels and oysters. Chromium is not likely to accumulate in the tissues of fish and shellfish. Limited studies of air

  5. Reacting gas mixtures in the state-to-state approach: The chemical reaction rates

    SciTech Connect

    Kustova, Elena V.; Kremer, Gilberto M.

    2014-12-09

    In this work chemically reacting mixtures of viscous flows are analyzed within the framework of Boltzmann equation. By applying a modified Chapman-Enskog method to the system of Boltzmann equations general expressions for the rates of chemical reactions and vibrational energy transitions are determined as functions of two thermodynamic forces: the velocity divergence and the affinity. As an application chemically reacting mixtures of N{sub 2} across a shock wave are studied, where the first lowest vibrational states are taken into account. Here we consider only the contributions from the first four single quantum vibrational-translational energy transitions. It is shown that the contribution to the chemical reaction rate related to the affinity is much larger than that of the velocity divergence.

  6. On the formation of new ignition kernels in the chemically active dispersed mixtures

    NASA Astrophysics Data System (ADS)

    Ivanov, M. F.; Kiverin, A. D.

    2015-11-01

    The specific features of the combustion waves propagating through the channels filled with chemically active gaseous mixture and non-uniformly suspended micro particles are studied numerically. It is shown that the heat radiated by the hot products, absorbed by the micro particles and then transferred to the environmental fresh mixture can be the source of new ignition kernels in the regions of particles' clusters. Herewith the spatial distribution of the particles determines the features of combustion regimes arising in these kernels. One can highlight the multi-kernel ignition in the polydisperse mixtures and ignition of the combustion regimes with shocks and detonation formation in the mixtures with pronounced gradients of microparticles concentration.

  7. Sedimentation stacking diagram of binary colloidal mixtures and bulk phases in the plane of chemical potentials.

    PubMed

    de las Heras, Daniel; Schmidt, Matthias

    2015-05-20

    We give a full account of a recently proposed theory that explicitly relates the bulk phase diagram of a binary colloidal mixture to its phase stacking phenomenology under gravity (de las Heras and Schmidt 2013 Soft Matter 9 8636). As we demonstrate, the full set of possible phase stacking sequences in sedimentation-diffusion equilibrium originates from straight lines (sedimentation paths) in the chemical potential representation of the bulk phase diagram. From the analysis of various standard topologies of bulk phase diagrams, we conclude that the corresponding sedimentation stacking diagrams can be very rich, even more so when finite sample height is taken into account. We apply the theory to obtain the stacking diagram of a mixture of nonadsorbing polymers and colloids. We also present a catalog of generic phase diagrams in the plane of chemical potentials in order to facilitate the practical application of our concept, which also generalizes to multi-component mixtures.

  8. AGONISTIC SENSORY EFFECTS OF AIRBORNE CHEMICALS IN MIXTURES: ODOR, NASAL PUNGENCY, AND EYE IRRITATION

    EPA Science Inventory

    Threshold responses of odor, nasal pungency (irritation), and eye irritation were measured for single chemicals (1-propanol, 1-hexanol, ethyl acetate, heptyl acetate, 2-pentanone, 2-heptanone, toluene, ethyl benzene, and propyl benzene) and mixtures of them (two three-component m...

  9. Bacterial Mixture Identification Using Raman and Surface-Enhanced Raman Chemical Imaging

    DTIC Science & Technology

    2008-12-01

    Initially, vegetative cells of Bacillus thuringiensis are compared between the two techniques, followed by a mixture comparison of Bacillus ...average particle size of 36 nm. 2.2 Bacteria Aqueous suspensions of Bacillus thuringiensis vegetative cells and spores, Bacillus anthracis sterne...Chemical Imaging of Bacillus thuringiensis vegetative cells BTVG cells coated with silver nanoparticles were analyzed with RCIM. To obtain the

  10. AGONISTIC SENSORY EFFECTS OF AIRBORNE CHEMICALS IN MIXTURES: ODOR, NASAL PUNGENCY, AND EYE IRRITATION

    EPA Science Inventory

    Threshold responses of odor, nasal pungency (irritation), and eye irritation were measured for single chemicals (1-propanol, 1-hexanol, ethyl acetate, heptyl acetate, 2-pentanone, 2-heptanone, toluene, ethyl benzene, and propyl benzene) and mixtures of them (two three-component m...

  11. Using the Science Writing Heuristic Approach to Enhance Student Understanding in Chemical Change and Mixture

    ERIC Educational Resources Information Center

    Kingir, Sevgi; Geban, Omer; Gunel, Murat

    2013-01-01

    This study investigated the effect of the Science Writing Heuristic (SWH) approach on grade 9 students' understanding of chemical change and mixture concepts. Four intact classes taught by two chemistry teachers from a Turkish public high school were selected for the study; one class was assigned as the treatment group, and the other class was…

  12. Using the Science Writing Heuristic Approach to Enhance Student Understanding in Chemical Change and Mixture

    ERIC Educational Resources Information Center

    Kingir, Sevgi; Geban, Omer; Gunel, Murat

    2013-01-01

    This study investigated the effect of the Science Writing Heuristic (SWH) approach on grade 9 students' understanding of chemical change and mixture concepts. Four intact classes taught by two chemistry teachers from a Turkish public high school were selected for the study; one class was assigned as the treatment group, and the other class was…

  13. Using the Science Writing Heuristic Approach to Enhance Student Understanding in Chemical Change and Mixture

    NASA Astrophysics Data System (ADS)

    Kingir, Sevgi; Geban, Omer; Gunel, Murat

    2013-08-01

    This study investigated the effect of the Science Writing Heuristic (SWH) approach on grade 9 students' understanding of chemical change and mixture concepts. Four intact classes taught by two chemistry teachers from a Turkish public high school were selected for the study; one class was assigned as the treatment group, and the other class was assigned as the comparison group. Students in the treatment group were instructed by the SWH approach, while those in the comparison group were instructed with traditionally designed chemistry instruction. Tests measuring students' conceptual understanding in the units of chemical change and mixture were administered as pre- and posttest for both groups. At the end of the instruction, semistructured interviews were conducted with 13 students from the treatment group and eight students from the comparison group. ANCOVA results revealed that the SWH approach was superior to the traditional approach on students' understanding of chemical change and mixture concepts. Interview results indicated that students in the treatment group demonstrated better scientific understanding of chemical change and mixture concepts compared to those in the comparison group.

  14. Enhancing the Chemical Mixture Methodology in Emergency Preparedness and Consequence Assessment

    SciTech Connect

    Yu, Xiao-Ying; Glantz, Clifford S.; Yao, Juan; He, Hua; Petrocchi, Achille J.; Craig, Doug K.; Ciolek, John T.; Booth, Alexander E.

    2013-11-01

    Emergency preparedness personnel at US Department of Energy (DOE) facilities use the chemical mixture methodology (CMM) to estimate the potential health impacts to workers and the public from the unintended airborne release of chemical mixtures. The CMM uses a Hazard Index (HI) to compare a chemical’s concentration at a receptor location to an appropriate concentration limit for that chemical. This limit is typically based on Protection Action Criteria (PAC) values developed and published by the DOE. As a first cut, the CMM sums the HIs for all the chemicals in a mixture to conservatively estimate their combined health impact. A cumulative HI ≥ 1.0 represents a concentration at or exceeding the concentration limit and indicates the potential for adverse health effects. Next, health code numbers (HCNs) are used to identify the target organ sets that may be impacted by exposure to each chemical in a mixture. The sum of the HIs for the maximally impacted target organ set is used to provide a refined, though still conservative estimate, of the potential for adverse health effects from exposure to the chemical mixture. This paper explores approaches to further enhance the effectiveness of the CMM by using HCN weighting factors to reduce over-conservatism. A series of 24 case studies have been defined to evaluate both the existing CMM and three new approaches for improving the CMM. The first approach uses a set of HCN weighting factors that are applied based on the priority ranking of the HCNs for each chemical. The second approach uses weighting factors based on the priority rankings of the HCNs established for a given type of concentration limit. The third approach uses information on the exposure route used to derive PAC values and the second approach’s HCN ranking to derive and apply its HCN weighting factors. Initial testing indicates that applying weighting factors reduces the over-conservatism in the CMM for certain types of chemical mixtures, though care

  15. From single chemicals to mixtures--reproductive effects of levonorgestrel and ethinylestradiol on the fathead minnow.

    PubMed

    Runnalls, Tamsin J; Beresford, Nicola; Kugathas, Subramaniam; Margiotta-Casaluci, Luigi; Scholze, Martin; Scott, Alexander P; Sumpter, John P

    2015-12-01

    The aquatic environment is polluted with thousands of chemicals. It is currently unclear which of these pose a significant threat to aquatic biota. The typical exposure scenario is now represented by a widespread blanket of contamination composed of myriads of individual pollutants-each typically present at a low concentration. The synthetic steroids, 17α-ethinylestradiol and levonorgestrel, have been widely reported to be present in the aquatic environment in the low ng to sub-ng/l range. They are widely used in contraceptive formulations, both individually and in combination. Our research employed the fathead minnow (Pimephales promelas) 21 day 'pair-breeding' assay to assess reproductive output when pairs of fish were exposed to the single chemicals at low environmentally relevant concentrations, and then to a binary mixture of them. A variety of endpoints were assessed, including egg production, which was inhibited in a concentration-dependent manner by both the individual chemicals and the mixture. Significant, sex specific effects were also seen with both chemicals, at differing levels of biological organisation. Plasma concentrations of EE2 and levonorgestrel were predicted and in the case of levonorgestrel measured, and compared with the human therapeutic plasma concentrations (Read-Across approach) to support the interpretation of the results. A novel quantitative method was developed for the data analysis, which ensured a suitable endpoint for the comparative mixture assessment. This approach compares the reproductive performance from individual pairs of fish during chemical exposure to its pre-treatment performance. The responses from the empirical mixture study were compared to predictions derived from the single substance data. We hypothesised combined responses which were best described by the concept of concentration addition, and found no clear indications against this additivity expectation. However, the effect profiles support the current

  16. Toxicogenomic responses in rainbow trout (Oncorhynchus mykiss) hepatocytes exposed to model chemicals and a synthetic mixture.

    PubMed

    Finne, E F; Cooper, G A; Koop, B F; Hylland, K; Tollefsen, K E

    2007-03-10

    As more salmon gene expression data has become available, the cDNA microarray platform has emerged as an appealing alternative in ecotoxicological screening of single chemicals and environmental samples relevant to the aquatic environment. This study was performed to validate biomarker gene responses of in vitro cultured rainbow trout (Oncorhynchus mykiss) hepatocytes exposed to model chemicals, and to investigate effects of mixture toxicity in a synthetic mixture. Chemicals used for 24h single chemical- and mixture exposures were 10 nM 17alpha-ethinylestradiol (EE2), 0.75 nM 2,3,7,8-tetrachloro-di-benzodioxin (TCDD), 100 microM paraquat (PQ) and 0.75 microM 4-nitroquinoline-1-oxide (NQO). RNA was isolated from exposed cells, DNAse treated and quality controlled before cDNA synthesis, fluorescent labelling and hybridisation to a 16k salmonid microarray. The salmonid 16k cDNA array identified differential gene expression predictive of exposure, which could be verified by quantitative real time PCR. More precisely, the responses of biomarker genes such as cytochrome p4501A and UDP-glucuronosyl transferase to TCDD exposure, glutathione reductase and gammaglutamyl cysteine synthetase to paraquat exposure, as well as vitellogenin and vitelline envelope protein to EE2 exposure validated the use of microarray applied to RNA extracted from in vitro exposed hepatocytes. The mutagenic compound NQO did not result in any change in gene expression. Results from exposure to a synthetic mixture of the same four chemicals, using identical concentrations as for single chemical exposures, revealed combined effects that were not predicted by results for individual chemicals alone. In general, the response of exposure to this mixture led to an average loss of approximately 60% of the transcriptomic signature found for single chemical exposure. The present findings show that microarray analyses may contribute to our mechanistic understanding of single contaminant mode of action as well

  17. Mixtures of Chemical Pollutants at European Legislation Safety Concentrations: How Safe Are They?

    PubMed Central

    Carvalho, Raquel N.; Arukwe, Augustine; Ait-Aissa, Selim; Bado-Nilles, Anne; Balzamo, Stefania; Baun, Anders; Belkin, Shimshon; Blaha, Ludek; Brion, François; Conti, Daniela; Creusot, Nicolas; Essig, Yona; Ferrero, Valentina E. V.; Flander-Putrle, Vesna; Fürhacker, Maria; Grillari-Voglauer, Regina; Hogstrand, Christer; Jonáš, Adam; Kharlyngdoh, Joubert B.; Loos, Robert; Lundebye, Anne-Katrine; Modig, Carina; Olsson, Per-Erik; Pillai, Smitha; Polak, Natasa; Potalivo, Monica; Sanchez, Wilfried; Schifferli, Andrea; Schirmer, Kristin; Sforzini, Susanna; Stürzenbaum, Stephen R.; Søfteland, Liv; Turk, Valentina; Viarengo, Aldo; Werner, Inge; Yagur-Kroll, Sharon; Zounková, Radka; Lettieri, Teresa

    2014-01-01

    The risk posed by complex chemical mixtures in the environment to wildlife and humans is increasingly debated, but has been rarely tested under environmentally relevant scenarios. To address this issue, two mixtures of 14 or 19 substances of concern (pesticides, pharmaceuticals, heavy metals, polyaromatic hydrocarbons, a surfactant, and a plasticizer), each present at its safety limit concentration imposed by the European legislation, were prepared and tested for their toxic effects. The effects of the mixtures were assessed in 35 bioassays, based on 11 organisms representing different trophic levels. A consortium of 16 laboratories was involved in performing the bioassays. The mixtures elicited quantifiable toxic effects on some of the test systems employed, including i) changes in marine microbial composition, ii) microalgae toxicity, iii) immobilization in the crustacean Daphnia magna, iv) fish embryo toxicity, v) impaired frog embryo development, and vi) increased expression on oxidative stress-linked reporter genes. Estrogenic activity close to regulatory safety limit concentrations was uncovered by receptor-binding assays. The results highlight the need of precautionary actions on the assessment of chemical mixtures even in cases where individual toxicants are present at seemingly harmless concentrations. PMID:24958932

  18. Toxicological evaluation of complex mixtures by pattern recognition: correlating chemical fingerprints to mutagenicity.

    PubMed Central

    Eide, Ingvar; Neverdal, Gunhild; Thorvaldsen, Bodil; Grung, Bjørn; Kvalheim, Olav M

    2002-01-01

    We describe the use of pattern recognition and multivariate regression in the assessment of complex mixtures by correlating chemical fingerprints to the mutagenicity of the mixtures. Mixtures were 20 organic extracts of exhaust particles, each containing 102-170 individual compounds such as polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs, oxy-PAHs, and saturated hydrocarbons. Mixtures were characterized by full-scan GC-MS (gas chromatography-mass spectrometry). Data were resolved into peaks and spectra for individual compounds by an automated curve resolution procedure. Resolved chromatograms were integrated, resulting in a predictor matrix that was used as input to a principal component analysis to evaluate similarities between mixtures (i.e., classification). Furthermore, partial least-squares projections to latent structures were used to correlate the GC-MS data to mutagenicity, as measured in the Ames Salmonella assay (i.e., calibration). The best model (high r2 and Q2) identifies the variables that co-vary with the observed mutagenicity. These variables may subsequently be identified in more detail. Furthermore, the regression model can be used to predict mutagenicity from GC-MS chromatograms of other organic extracts. We emphasize that both chemical fingerprints as well as detailed data on composition can be used in pattern recognition. PMID:12634129

  19. Characterization of the pharmacokinetics of gasoline using PBPK modeling with a complex mixtures chemical lumping approach.

    PubMed

    Dennison, James E; Andersen, Melvin E; Yang, Raymond S H

    2003-09-01

    Gasoline consists of a few toxicologically significant components and a large number of other hydrocarbons in a complex mixture. By using an integrated, physiologically based pharmacokinetic (PBPK) modeling and lumping approach, we have developed a method for characterizing the pharmacokinetics (PKs) of gasoline in rats. The PBPK model tracks selected target components (benzene, toluene, ethylbenzene, o-xylene [BTEX], and n-hexane) and a lumped chemical group representing all nontarget components, with competitive metabolic inhibition between all target compounds and the lumped chemical. PK data was acquired by performing gas uptake PK studies with male F344 rats in a closed chamber. Chamber air samples were analyzed every 10-20 min by gas chromatography/flame ionization detection and all nontarget chemicals were co-integrated. A four-compartment PBPK model with metabolic interactions was constructed using the BTEX, n-hexane, and lumped chemical data. Target chemical kinetic parameters were refined by studies with either the single chemical alone or with all five chemicals together. o-Xylene, at high concentrations, decreased alveolar ventilation, consistent with respiratory irritation. A six-chemical interaction model with the lumped chemical group was used to estimate lumped chemical partitioning and metabolic parameters for a winter blend of gasoline with methyl t-butyl ether and a summer blend without any oxygenate. Computer simulation results from this model matched well with experimental data from single chemical, five-chemical mixture, and the two blends of gasoline. The PBPK model analysis indicated that metabolism of individual components was inhibited up to 27% during the 6-h gas uptake experiments of gasoline exposures.

  20. Predictive performance of the Short Time Exposure test for identifying eye irritation potential of chemical mixtures.

    PubMed

    Saito, Kazutoshi; Miyazawa, Masaaki; Nukada, Yuko; Ei, Kyo; Abo, Takayuki; Sakaguchi, Hitoshi

    2015-04-01

    The Short Time Exposure (STE) test is an in vitro eye irritation test based on the cytotoxicity in SIRC cells (rabbit corneal cell line) following a 5 min treatment of chemicals. This study evaluated the predictive performance of the STE test to identify the globally harmonized system (GHS) Not Classified category and other irritant categories (i.e., GHS Category 1 or 2) when used to test 40 chemical mixtures that included irritants. The STE test correctly identified 30 tested mixtures classified as GHS irritant categories and 5 out of 10 tested mixtures classified as GHS Not Classified. The sensitivity, specificity, positive predictivity, negative predictivity, and overall accuracy of the STE test were 100% (30/30), 50% (5/10), 86% (25/30), 100% (5/5), and 88% (35/40), respectively. These predictive performances were comparative to or greater than those in other in vitro eye irritation tests that have been accepted as test guideline by the Organisation for Economic Co-operation and Development. This suggests that the STE test has sufficient predictivity for identifying the eye irritation potential of chemical mixtures. Since no false negatives in this study were found, this indicates that the STE test is applicable as a part of the bottom-up approach. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. EPA project-level research strategies for chemical mixtures: targeted research for meaningful results.

    PubMed

    Teuschler, Linda K; Hertzberg, Richard C; Rice, Glenn E; Simmons, Jane Ellen

    2004-12-01

    Project-level research strategies at the U.S. Environmental Protection Agency regarding chemical mixtures are impacted by administrative priorities, public interests, expert opinions, scientific advances, regulatory needs, and legislative actions, influencing the setting of priorities and goals. Perhaps, the most significant influence on conducting chemical mixtures research is the passage of laws requiring the EPA to investigate the potential toxicity of various mixtures, specifically the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, the Food Quality Protection Act of 1996, and the Safe Drinking Water Act Amendments of 1996. Scarce resources are allocated to broadly defined issues for consideration by teams of scientists, who design and implement specific projects. Because resources are limited, projects may have several goals, e.g., filling specific data gaps to support a regulation and, simultaneously, producing data to evaluate a risk assessment method. Research areas of emphasis are shaped by risk assessment needs, data gap uncertainties, and experimental design considerations. This paper discusses factors shaping EPA research strategies for chemical mixtures and presents an example of efficient research planning to investigate potential toxicity from exposure to drinking water disinfection by-products.

  2. Data set from chemical sensor array exposed to turbulent gas mixtures

    PubMed Central

    Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Huerta, Ramón

    2015-01-01

    A chemical detection platform composed of 8 chemo-resistive gas sensors was exposed to turbulent gas mixtures generated naturally in a wind tunnel. The acquired time series of the sensors are provided. The experimental setup was designed to test gas sensors in realistic environments. Traditionally, chemical detection systems based on chemo-resistive sensors include a gas chamber to control the sample air flow and minimize turbulence. Instead, we utilized a wind tunnel with two independent gas sources that generate two gas plumes. The plumes get naturally mixed along a turbulent flow and reproduce the gas concentration fluctuations observed in natural environments. Hence, the gas sensors can capture the spatio-temporal information contained in the gas plumes. The sensor array was exposed to binary mixtures of ethylene with either methane or carbon monoxide. Volatiles were released at four different rates to induce different concentration levels in the vicinity of the sensor array. Each configuration was repeated 6 times, for a total of 180 measurements. The data is related to “Chemical Discrimination in Turbulent Gas Mixtures with MOX Sensors Validated by Gas Chromatography-Mass Spectrometry”, by Fonollosa et al. [1]. The dataset can be accessed publicly at the UCI repository upon citation of [1]: http://archive.ics.uci.edu/ml/datasets/Gas+senso+rarray+exposed+to+turbulent+gas+mixtures. PMID:26217747

  3. Comprehensive default methodology for the analysis of exposures to mixtures of chemicals accidentally released to the atmosphere

    SciTech Connect

    Craig, D.K.; Baskett, R.L.; Powell, T.J.; Davis, J.S.; Dukes, L.L.; Hansen, D.J.; Petrocchi, A.J.; Sutherland, P.J.

    1997-07-01

    Safety analysis of Department of Energy (DOE) facilities requires consideration of potential exposures to mixtures of chemicals released to the atmosphere. Exposure to chemical mixtures may lead to additive, synergistic, or antagonistic health effects. In the past, the consequences of each chemical have been analyzed separately. This approach may not adequately protect the health of persons exposed to mixtures. However, considerable time would be required to evaluate all possible mixtures. The objective of this paper is to present reasonable default methodology developed by the EFCOG Safety Analysis Working Group Nonradiological Hazardous Material Subgroup (NHMS) for use in safety analysis within the DOE Complex.

  4. A Chemical Kinetic Mechanism for the Ignition of Silane/Hydrogen Mixtures

    NASA Technical Reports Server (NTRS)

    Jachimowski, C. J.; Mclain, A. G.

    1983-01-01

    A chemical kinetic reaction mechanism for the oxidation of silane/hydrogen mixtures is presented and discussed. Shock-tube ignition delay time data were used to evaluate and refine the mechanism. Good agreement between experimental results and the results predicted by the mechanism was obtained by adjusting the rate coefficient for the reaction SiH3 + O2 yields SiH2O + OH. The reaction mechanism was used to theoretically investigate the ignition characteristics of silane/hydrogen mixtures. The results revealed that over the entire range of temperature examined (800 K to 1200 K), substantial reduction in ignition delay times is obtained when silane is added to hydrogen.

  5. Enhancing the Benefit of the Chemical Mixture Methodology: A Report on Methodology Testing and Potential Approaches for Improving Performance

    SciTech Connect

    Yu, Xiao-Ying; Yao, Juan; He, Hua; Glantz, Clifford S.; Booth, Alexander E.

    2012-01-01

    Extensive testing shows that the current version of the Chemical Mixture Methodology (CMM) is meeting its intended mission to provide conservative estimates of the health effects from exposure to airborne chemical mixtures. However, the current version of the CMM could benefit from several enhancements that are designed to improve its application of Health Code Numbers (HCNs) and employ weighting factors to reduce over conservatism.

  6. Effective Strategies for Monitoring and Regulating Chemical Mixtures and Contaminants Sharing Pathways of Toxicity

    PubMed Central

    Venkatesan, Arjun K.; Halden, Rolf U.

    2015-01-01

    Traditionally, hazardous chemicals have been regulated in the U.S. on a one-by-one basis, an approach that is slow, expensive and can be inefficient, as illustrated by a decades-long succession of replacing one type of organohalogen flame retardants (OHFRs) with another one, without addressing the root cause of toxicity and associated public health threats posed. The present article expounds on the need for efficient monitoring strategies and pragmatic steps in reducing environmental pollution and adverse human health impacts. A promising approach is to combine specific bioassays with state-of-the-art chemical screening to identify chemicals and chemical mixtures sharing specific modes of action (MOAs) and pathways of toxicity (PoTs). This approach could be used to identify and regulate hazardous chemicals as classes or compound families, featuring similar biological end-points, such as endocrine disruption and mutagenicity. Opportunities and potential obstacles of implementing this approach are discussed. PMID:26343697

  7. Regulatory assessment of chemical mixtures: Requirements, current approaches and future perspectives.

    PubMed

    Kienzler, Aude; Bopp, Stephanie K; van der Linden, Sander; Berggren, Elisabet; Worth, Andrew

    2016-10-01

    This paper reviews regulatory requirements and recent case studies to illustrate how the risk assessment (RA) of chemical mixtures is conducted, considering both the effects on human health and on the environment. A broad range of chemicals, regulations and RA methodologies are covered, in order to identify mixtures of concern, gaps in the regulatory framework, data needs, and further work to be carried out. Also the current and potential future use of novel tools (Adverse Outcome Pathways, in silico tools, toxicokinetic modelling, etc.) in the RA of combined effects were reviewed. The assumptions made in the RA, predictive model specifications and the choice of toxic reference values can greatly influence the assessment outcome, and should therefore be specifically justified. Novel tools could support mixture RA mainly by providing a better understanding of the underlying mechanisms of combined effects. Nevertheless, their use is currently limited because of a lack of guidance, data, and expertise. More guidance is needed to facilitate their application. As far as the authors are aware, no prospective RA concerning chemicals related to various regulatory sectors has been performed to date, even though numerous chemicals are registered under several regulatory frameworks.

  8. Chemical mixtures and environmental effects: a pilot study to assess ecological exposure and effects in streams

    USGS Publications Warehouse

    Buxton, Herbert T.; Reilly, Timothy J.; Kuivila, Kathryn; Kolpin, Dana W.; Bradley, Paul M.; Villeneuve, Daniel L.; Mills, Marc A.

    2015-01-01

    Assessment and management of the risks of exposure to complex chemical mixtures in streams are priorities for human and environmental health organizations around the world. The current lack of information on the composition and variability of environmental mixtures and a limited understanding of their combined effects are fundamental obstacles to timely identification and prevention of adverse human and ecological effects of exposure. This report describes the design of a field-based study of the composition and biological activity of chemical mixtures in U.S. stream waters affected by a wide range of human activities and contaminant sources. The study is a collaborative effort by the U.S. Geological Survey and the U.S. Environmental Protection Agency. Scientists sampled 38 streams spanning 24 States and Puerto Rico. Thirty-four of the sites were located in watersheds impacted by multiple contaminant sources, including industrial and municipal wastewater discharges, crop and animal agricultural runoff, urban runoff, and other point and nonpoint contaminant sources. The remaining four sites were minimally development reference watersheds. All samples underwent comprehensive chemical and biological characterization, including sensitive and specific direct analysis for over 700 dissolved organic and inorganic chemicals and field parameters, identification of unknown contaminants (environmental diagnostics), and a variety of bioassays to evaluate biological activity and toxicity.

  9. Adaptive stress response pathways induced by environmental mixtures of bioaccumulative chemicals in dugongs.

    PubMed

    Jin, Ling; Gaus, Caroline; Escher, Beate I

    2015-06-02

    To address the poorly understood mixture effects of chemicals in the marine mammal dugong, we coupled equilibrium-based passive sampling in blubber to a range of in vitro bioassays for screening mixtures of bioaccumulative chemicals. The modes of action included early effect indicators along important toxicity pathways, such as induction of xenobiotic metabolism, and some integrative indicators downstream of the molecular initiating event, such as adaptive stress responses. Activation of aryl hydrocarbon receptor (AhR) and Nrf2-mediated oxidative stress response were found to be the most prominent effects, while the p53-mediated DNA damage response and NF-κB-mediated response to inflammation were not significantly affected. Although polychlorinated dibenzo-p-dioxins (PCDDs) quantified in the samples accounted for the majority of AhR-mediated activity, PCDDs explained less than 5% of the total oxidative stress response, despite their known ability to activate this pathway. Altered oxidative stress response was observed with both individual chemicals and blubber extracts subject to metabolic activation by rat liver S9 fraction. Metabolic activation resulted in both enhanced and reduced toxicity, suggesting the relevance and utility of incorporating metabolic enzymes into in vitro bioassays. Our approach provides a first insight into the burden of toxicologically relevant bioaccumulative chemical mixtures in dugongs and can be applied to lipid tissue of other wildlife species.

  10. Global phase behavior of supercritical water - environmentally significant organic chemicals mixtures

    NASA Astrophysics Data System (ADS)

    Artemenko, S. V.; Mazur, V. A.

    Recent developments of the global phase equilibria studies of binary mixtures provide some basic ideas of how the required methods can be developed based on global phase diagrams for visualization of the phase behavior of mixtures. The mapping of the global equilibrium surface in the parameter space of the equation of state (EoS) model provides the most comprehensive system of criteria for predicting binary mixture phase behavior. The main types of phase behavior for environmentally significant organic chemicals in aqueous environments are considered using structure-property correlations for the critical parameters of substances. Analytic expressions for azeotropy prediction for cubic EoS are derived. A local mapping concept is introduced to describe thermodynamically consistently the saturation curve of water.

  11. Chemical composition and binary mixture of human urinary stones using FT-Raman spectroscopy method.

    PubMed

    Selvaraju, R; Raja, A; Thiruppathi, G

    2013-10-01

    In the present study the human urinary stones were observed in their different chemical compositions of calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate, struvite (magnesium ammonium phosphate), uric acid, cystine, oxammite (ammonium oxalate monohydrate), natroxalate (sodium oxalate), glushinkite (magnesium oxalate dihydrate) and moolooite (copper oxalate) were analyzed using Fourier Transform-Raman (FT-Raman) spectroscopy. For the quantitative analysis, various human urinary stone samples are used for ratios calculation of binary mixtures compositions such as COM/COD, HAP/COD, HAP/COD, Uric acid/COM, uric acid/COD and uric acid/HAP. The calibration curve is used for further analysis of binary mixture of human urinary stones. For the binary mixture calculation the various intensities bands at 1462 cm(-1) (I(COM)), 1473 cm(-1) (I(COD)), 961 cm(-1) (I(HAP)) and 1282 cm(-1) (I(UA)) were used.

  12. Chemical composition and binary mixture of human urinary stones using FT-Raman spectroscopy method

    NASA Astrophysics Data System (ADS)

    Selvaraju, R.; Raja, A.; Thiruppathi, G.

    2013-10-01

    In the present study the human urinary stones were observed in their different chemical compositions of calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate, struvite (magnesium ammonium phosphate), uric acid, cystine, oxammite (ammonium oxalate monohydrate), natroxalate (sodium oxalate), glushinkite (magnesium oxalate dihydrate) and moolooite (copper oxalate) were analyzed using Fourier Transform-Raman (FT-Raman) spectroscopy. For the quantitative analysis, various human urinary stone samples are used for ratios calculation of binary mixtures compositions such as COM/COD, HAP/COD, HAP/COD, Uric acid/COM, uric acid/COD and uric acid/HAP. The calibration curve is used for further analysis of binary mixture of human urinary stones. For the binary mixture calculation the various intensities bands at 1462 cm-1 (ICOM), 1473 cm-1 (ICOD), 961 cm-1 (IHAP) and 1282 cm-1 (IUA) were used.

  13. Quantification of chemical mixture interactions modulating dermal absorption using a multiple membrane fiber array.

    PubMed

    Baynes, Ronald E; Xia, Xin Rui; Imran, Mudassar; Riviere, Jim E

    2008-03-01

    Dermal exposures to chemical mixtures can potentially increase or decrease systemic bioavailability of toxicants in the mixture. Changes in dermal permeability can be attributed to changes in physicochemical interactions between the mixture, the skin, and the solute of interest. These physicochemical interactions can be described as changes in system coefficients associated with molecular descriptors described by Abraham's linear solvation energy relationship (LSER). This study evaluated the effects of chemical mixtures containing either a solvent (ethanol) or a surfactant (sodium lauryl sulfate, SLS) on solute permeability and partitioning by quantifying changes in system coefficients in skin and a three-membrane-coated fiber (MCF) system, respectively. Regression analysis demonstrated that changes in system coefficients in skin were strongly correlated ( R2 = 0.89-0.98) to changes in system coefficients in the three-membrane MCF array with mixtures containing either 1% SLS or 50% ethanol. The PDMS fiber appeared to play a significant role (R2 = 0.84-0.85) in the MCF array in predicting changes in solute permeability, while the WAX fiber appeared to contribute less (R2 = 0.59-0.77) to the array than the other two fibers. On the basis of changes in system coefficients that are part of a LSER, these experiments were able to link physicochemical interactions in the MCF with those interactions in skin when either system is exposed to 1% SLS or 50% ethanol. These experiments further demonstrated the utility of a MCF array to adequately predict changes in dermal permeability when skin is exposed to mixtures containing either a surfactant or a solvent and provide some insight into the nature of the physiochemical interactions that modulate dermal absorptions.

  14. Modeling acute and chronic toxicity of nonpolar narcotic chemicals and mixtures to Ceriodaphnia dubia.

    PubMed

    Niederlehner, B R; Cairns, J; Smith, E P

    1998-02-01

    The response of the daphnid Ceriodaphnia dubia to six widely used industrial chemicals acting through nonpolar narcosis and a mixture was determined. Toxicological effect levels were based on reasonably steady-state, measured concentrations. Reproductive IC50S were 149 microM benzene, 82 microM trichloroethylene, 35 microM toluene, 31 microM ethylbenzene, 26 microM m-xylene, and 4 microM tetrachloroethylene. A QSAR describing 2-day LC50S as a function of log Kow accounted for 90.97% of the variation in response across chemical. A similar QSAR for chronic effects on reproduction accounted for 78.92%. Mixtures of benzene, trichloroethylene, and toluene had effects at concentrations below their individual LOELs. Observed effects of 20/24 mixtures tested fell within the 95% prediction interval for a concentration-addition model of joint action derived from tests with individual components. However, the observed response differed significantly from the predictive relationship. In general, the predictive relationship overestimated mixture toxicity. Fitted relationships reduced observed error by as much as 82% compared to the predictive model.

  15. Estrogenic effects of mixtures of phyto- and synthetic chemicals on uterine growth of prepubertal rats.

    PubMed

    van Meeuwen, J A; van den Berg, M; Sanderson, J T; Verhoef, A; Piersma, A H

    2007-04-25

    Through the diet humans are exposed to many weak estrogenic phytochemicals (PCs) and synthetic chemicals (SCs), but most experimental studies used individual compounds rather than mixtures. Estrogenic effects were determined in the rat juvenile uterotrophic assay using a predefined phytochemical mixture (PCmix) containing coumestrol, genistein, naringenin, (+,-)catechin, (-,-)epicatechin and quercetin, and a predefined synthetic chemical mixture (SCmix) containing nonyl-, and octylphenol, beta-hexachlorocyclohexane, methoxychlor, bisphenol A and dibutylphthalate. The mixture composition was based on human dietary uptake and actual ratios in serum. 17beta-Estradiol and genistein were also tested individually. It was found that combinations of phytoestrogens and exogenous 17beta-estradiol act additive. In contrast SCmix, inactive by itself even at high dose levels relative to human exposure, caused no synergistic or antagonistic uterotrophic effect with E(2) and/or the PCmix. Based on ED(05) and ED(01) values of the PCmix the margin of exposure in regular human diet for a uterotrophic effect is estimated many orders of magnitude. However, food supplements with phytochemicals might bring individual exposure around ED(05) and ED(01) values of the PCmix. Based on the results of our study the contribution of SCs to total estrogenicity in human diet can probably be neglected.

  16. Using quantitative structural property relationships, chemical fate models, and the chemical partitioning space to investigate the potential for long range transport and bioaccumulation of complex halogenated chemical mixtures.

    PubMed

    Gawor, Anya; Wania, Frank

    2013-09-01

    Some substances are mixtures of very large number of constituents which vary widely in their properties, and thus also in terms of their environmental fate and the hazard that they may pose to humans and the environment. Examples of such substances include industrial chemicals such as the chlorinated paraffins, technical pesticides such as toxaphene, and unintended combustion side products, such as mixed halogenated dibenzo-p-dioxins and dibenzofurans. Here we describe a simple graphical superposition method that could precede a more detailed hazard assessment for such substances. First, partitioning and degradation properties for each individual constituent of a mixture are estimated with high-throughput quantitative structure-property relationships. Placed in a chemical partitioning space, i.e. a coordinate system defined by two partitioning coefficients, the mixtures appear as 'clouds'. When model-derived hazard assessment metrics, such as the potential for bioaccumulation and long range transport, are superimposed on these clouds, the resulting maps identify the constituents with the highest value for a particular parameter and thus potentially the greatest hazard. The maps also indicate transparently how the potential for long range transport and bioaccumulation is dependent on structural attributes, such as chain length, and the degree and type of halogenation. In contrast to previous approaches, in which the mixture is represented by a single set of properties or those of a few selected constituents, the whole range of environmental fate behaviors displayed by the constituents of a mixture are being considered. The approach is illustrated with three sets of chemical substances.

  17. Gene expression profiles in rainbow trout, Onchorynchus mykiss, exposed to a simple chemical mixture.

    SciTech Connect

    Hook, Sharon E.; Skillman, Ann D.; Gopalan, Banu; Small, Jack A.; Schultz, Irvin R.

    2008-03-01

    Among proposed uses for microarrays in environmental toxiciology is the identification of key contributors to toxicity within a mixture. However, it remains uncertain whether the transcriptomic profiles resulting from exposure to a mixture have patterns of altered gene expression that contain identifiable contributions from each toxicant component. We exposed isogenic rainbow trout Onchorynchus mykiss, to sublethal levels of ethynylestradiol, 2,2,4,4 tetrabromodiphenyl ether, and chromium VI or to a mixture of all three toxicants Fluorescently labeled cDNA were generated and hybridized against a commercially available Salmonid array spotted with 16,000 cDNAs. Data were analyzed using ANOVA (p < 0.05) with a Benjamani-Hochberg multiple test correction (Genespring (Agilent) software package) to identify up and down regulated genes. Gene clustering patterns that can be used as “expression signatures” were determined using hierarchical cluster analysis. The gene ontology terms associated with significantly altered genes were also used to identify functional groups that were associated with toxicant exposure. Cross-ontological analytics (XOA) approach was used to assign functional annotations to genes with "unknown" function. Our analysis indicates that transcriptomic profiles resulting from the mixture exposure resemble those of the individual contaminant exposures, but are not a simple additive list. However, patterns of altered genes representative of each component of the mixture are clearly discernible, and the functional classes of genes altered represent the individual components of the mixture. These findings indicate that the use of microarrays to identify transcriptomic profiles may aid in the identification of key stressors within a chemical mixture, ultimately improving environmental assessment.

  18. Gene expression profiles in rainbow trout, Onchorynchus mykiss, exposed to a simple chemical mixture.

    PubMed

    Hook, Sharon E; Skillman, Ann D; Gopalan, Banu; Small, Jack A; Schultz, Irvin R

    2008-03-01

    Among proposed uses for microarrays in environmental toxiciology is the identification of key contributors to toxicity within a mixture. However, it remains uncertain whether the transcriptomic profiles resulting from exposure to a mixture have patterns of altered gene expression that contain identifiable contributions from each toxicant component. We exposed isogenic rainbow trout Onchorynchus mykiss, to sublethal levels of ethynylestradiol, 2,2,4,4-tetrabromodiphenyl ether, and chromium VI or to a mixture of all three toxicants Fluorescently labeled complementary DNA (cDNA) were generated and hybridized against a commercially available Salmonid array spotted with 16,000 cDNAs. Data were analyzed using analysis of variance (p<0.05) with a Benjamani-Hochberg multiple test correction (Genespring [Agilent] software package) to identify up and downregulated genes. Gene clustering patterns that can be used as "expression signatures" were determined using hierarchical cluster analysis. The gene ontology terms associated with significantly altered genes were also used to identify functional groups that were associated with toxicant exposure. Cross-ontological analytics approach was used to assign functional annotations to genes with "unknown" function. Our analysis indicates that transcriptomic profiles resulting from the mixture exposure resemble those of the individual contaminant exposures, but are not a simple additive list. However, patterns of altered genes representative of each component of the mixture are clearly discernible, and the functional classes of genes altered represent the individual components of the mixture. These findings indicate that the use of microarrays to identify transcriptomic profiles may aid in the identification of key stressors within a chemical mixture, ultimately improving environmental assessment.

  19. The fetal ovary exhibits temporal sensitivity to a ‘real-life’ mixture of environmental chemicals

    PubMed Central

    Lea, Richard G.; Amezaga, Maria R.; Loup, Benoit; Mandon-Pépin, Béatrice; Stefansdottir, Agnes; Filis, Panagiotis; Kyle, Carol; Zhang, Zulin; Allen, Ceri; Purdie, Laura; Jouneau, Luc; Cotinot, Corinne; Rhind, Stewart M.; Sinclair, Kevin D.; Fowler, Paul A.

    2016-01-01

    The development of fetal ovarian follicles is a critical determinant of adult female reproductive competence. Prolonged exposure to environmental chemicals (ECs) can perturb this process with detrimental consequences for offspring. Here we report on the exposure of pregnant ewes to an environmental mixture of ECs derived from pastures fertilized with sewage sludge (biosolids): a common global agricultural practice. Exposure of pregnant ewes to ECs over 80 day periods during early, mid or late gestation reduced the proportion of healthy early stage fetal follicles comprising the ovarian reserve. Mid and late gestation EC exposures had the most marked effects, disturbing maternal and fetal liver chemical profiles, masculinising fetal anogenital distance and greatly increasing the number of altered fetal ovarian genes and proteins. In conclusion, differential temporal sensitivity of the fetus and its ovaries to EC mixtures has implications for adult ovarian function following adverse exposures during pregnancy. PMID:26931299

  20. Differentiation of complex vapor mixtures using versatile DNA-carbon nanotube chemical sensor arrays.

    PubMed

    Kybert, Nicholas J; Lerner, Mitchell B; Yodh, Jeremy S; Preti, George; Johnson, A T Charlie

    2013-03-26

    Vapor sensors based on functionalized carbon nanotubes (NTs) have shown great promise, with high sensitivity conferred by the reduced dimensionality and exceptional electronic properties of the NT. Critical challenges in the development of NT-based sensor arrays for chemical detection include the demonstration of reproducible fabrication methods and functionalization schemes that provide high chemical diversity to the resulting sensors. Here, we outline a scalable approach to fabricating arrays of vapor sensors consisting of NT field effect transistors functionalized with single-stranded DNA (DNA-NT). DNA-NT sensors were highly reproducible, with responses that could be described through equilibrium thermodynamics. Target analytes were detected even in large backgrounds of volatile interferents. DNA-NT sensors were able to discriminate between highly similar molecules, including structural isomers and enantiomers. The sensors were also able to detect subtle variations in complex vapors, including mixtures of structural isomers and mixtures of many volatile organic compounds characteristic of humans.

  1. The Effect of Perfluorooctane Sulfonate, Exposure Time, and Chemical Mixtures on Methanogenic Community Structure and Function

    PubMed Central

    McNamara, Patrick J; LaPara, Timothy M; Novak, Paige J

    2015-01-01

    A plethora of organic micropollutant mixtures are found in untreated municipal wastewater. Anaerobic digesters receive large loadings of hydrophobic micropollutants that sorb to wastewater biosolids. Despite micropollutants being pervasive as mixtures, little research is available to explain the impact that mixtures of compounds, as well as exposure time, have on microbial communities in anaerobic digesters. Perfluorooctane sulfonate (PFOS) was added to anaerobic enrichment cultures in both short-term (14 days) and long-term (140 days) studies to determine the impact of exposure time. Additionally, triclosan was added during the experiments to investigate the impact of mixtures on community structure and function. PFOS did not alter methane production in short-term studies, but in long-term studies, methane production increased, consistent with our hypothesis that PFOS may act as a metabolic uncoupler. The impact of triclosan on methane production was exacerbated when PFOS was already present in the anaerobic enrichment cultures. Triclosan also had greater impacts on microbial community structures in the bottles that had been exposed to PFOS long-term. These results demonstrate that both chemical mixtures and exposure time are important parameters to address when trying to define the impacts of micropollutants on anaerobic microbial communities. PMID:26462249

  2. Toxicity of a hazardous chemical mixture in the planarian, Dugesia dorotocephala

    SciTech Connect

    Ramsdell, H.S.; Matthews, C.M.

    1995-12-31

    The responses of the planarian, Dugesia dorotocephala to toxic chemical mixtures representative of water contaminants associated with hazardous waste sites have been studied in laboratory experiments. These free-living flatworms are readily maintained under laboratory conditions and are a useful invertebrate model for toxicology studies. Their widespread occurrence also makes them potentially useful for environmental studies. Mature asexual Dugesia dorotocephala were exposed for 14 days to mixtures of seven contaminants frequently detected in water at hazardous waste sites. The complete 1X mixture contained both metals (As, 3.1 ppm; Cr, 0.7 ppm; Pb, 3.7 ppm) and organics (chloroform, 1.5 ppm; benzene, 5.0 ppm; phenol, 3.4 ppm; trichloroethylene, 3.8 ppm). Groups of planaria were treated with the complete mixture at 0.1X, 1X and 10X concentrations. Additional groups were exposed to the metals-only or organics-only submixtures, also at 0.1X, 1X and 10X concentrations. Treatment solutions were renewed daily. Suppression of fissioning was observed in all of the 1X and 10X treatment groups. Significant mortality occurred only in the 10X complete and 1 0X metals-only treatments. It appears that the toxic effects of the complete mixture are primarily associated with the metal components.

  3. Chemical Equilibrium Mixture Computations for Energetic Material Combustion in Closed Vessels

    DTIC Science & Technology

    2004-12-01

    are used with well-known equations of state stemming from Redlich , Kwong and Soave (RKS); Benedict, Webb, Rubin, Starling and Han (BWRSH); Becker...chemical activ- ity, type of mixture (ideal or nonideal) and pressure- volume-temperature properties ( equation of state ) of the gaseous, liquid and...accurate equations of state and ad- ditional thermochemical data for imperfect gas be- haviour and for the compressibility of liquids and solids. This

  4. Viscous shock layer solutions for turbulent flow of radiating gas mixtures in chemical equilibrium

    NASA Technical Reports Server (NTRS)

    Anderson, E. C.; Moss, J. N.

    1975-01-01

    The viscous shock layer equations for hypersonic laminar and turbulent flows of radiating or nonradiating gas mixtures in chemical equilibrium are presented for two-dimensional and axially symmetric flow fields. Solutions are obtained using an implicit finite difference scheme and results are presented for hypersonic flow over spherically blunted cone configurations at free stream conditions representative of entry into the atmosphere of Venus. These data are compared with solutions obtained using other methods of analysis.

  5. Viscous-shock-layer solutions for turbulent flow of radiating gas mixtures in chemical equilibrium

    NASA Technical Reports Server (NTRS)

    Anderson, E. C.; Moss, J. N.

    1975-01-01

    The viscous-shock-layer equations for hypersonic laminar and turbulent flows of radiating or nonradiating gas mixtures in chemical equilibrium are presented for two-dimensional and axially-symmetric flow fields. Solutions were obtained using an implicit finite-difference scheme and results are presented for hypersonic flow over spherically-blunted cone configurations at freestream conditions representative of entry into the atmosphere of Venus. These data are compared with solutions obtained using other methods of analysis.

  6. Modeling Joint Effects of Mixtures of Chemicals on Microorganisms Using Quantitative Structure Activity Relationships

    DTIC Science & Technology

    1993-08-22

    toxicity results from the 40 chemicals placed in the testing set were used to develop QSAR models. Molecular connectivity indexes were calculated for...Toxic Unit, Additivity Index , and Mixture Toxicity Index . The validity of these concepts was further verified using the results of the 8-component testing...standard deviation of 22.6. These variations are comparable to those reported by Blum (1989) for activated sludge cultures and Microtox , and may be

  7. p53 induction and cell viability modulation by genotoxic individual chemicals and mixtures.

    PubMed

    Di Paolo, Carolina; Müller, Yvonne; Thalmann, Beat; Hollert, Henner; Seiler, Thomas-Benjamin

    2017-03-16

    The binding of the p53 tumor suppression protein to DNA response elements after genotoxic stress can be quantified by cell-based reporter gene assays as a DNA damage endpoint. Currently, bioassay evaluation of environmental samples requires further knowledge on p53 induction by chemical mixtures and on cytotoxicity interference with p53 induction analysis for proper interpretation of results. We investigated the effects of genotoxic pharmaceuticals (actinomycin D, cyclophosphamide) and nitroaromatic compounds (4-nitroquinoline 1-oxide, 3-nitrobenzanthrone) on p53 induction and cell viability using a reporter gene and a colorimetric assay, respectively. Individual exposures were conducted in the absence or presence of metabolic activation system, while binary and tertiary mixtures were tested in its absence only. Cell viability reduction tended to present direct correlation with p53 induction, and induction peaks occurred mainly at chemical concentrations causing cell viability below 80%. Mixtures presented in general good agreement between predicted and measured p53 induction factors at lower concentrations, while higher chemical concentrations gave lower values than expected. Cytotoxicity evaluation supported the selection of concentration ranges for the p53 assay and the interpretation of its results. The often used 80% viability threshold as a basis to select the maximum test concentration for cell-based assays was not adequate for p53 induction assessment. Instead, concentrations causing up to 50% cell viability reduction should be evaluated in order to identify the lowest observed effect concentration and peak values following meaningful p53 induction.

  8. Polymer Exemption Guidance Manual for premanufacture notices for new chemicals under the Toxic Substances Control Act (TSCA)

    EPA Pesticide Factsheets

    A technical manual to accompany, but not supersede the Premanufacture Notification Exemptions; Revisions of Exemptions for Polymers; Final Rule found at 40 CFR Part 723, (60) FR 16316-16336, published Wednesday, March 29, 1995.

  9. 40 CFR 750.11 - Filing of petitions for exemption.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... of time requested for exemption (maximum length of exemption is 1 year). (5) Amount of PCB chemical... without changing its terms, must submit a letter by certified mail to EPA requesting that the exemption be... aspect of the exemption have not changed from the original exemption petition request. (ii) This...

  10. 76 FR 17778 - Control of Ergocristine, a Chemical Precursor Used in the Illicit Manufacture of Lysergic Acid...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-31

    ... containing ergocristine will not be exempt from regulatory requirements at any concentration. Therefore, all... regulatory requirements at any concentration, unless an application for exemption of a chemical mixture is... process discussed below. The Table of Concentration Limits in 21 CFR 1310.12(c) is hereby modified to...

  11. CWIS Experiment On Board REXUS-16 Sounding Rocket: Investigation of the Chemical Wave in Binary Mixture

    NASA Astrophysics Data System (ADS)

    Tzevelecos, W.; Pugliese, A.; de Filippis, L.; Manzone, S.; Alfano, B.; Mancino, F.; Runge, W.; Desenfans, O.; Galand, Q.; Van Vaerenbergh, S.

    2015-09-01

    Chemical Wave in Soret Effect (CWIS) is an experiment launched in May 2014 on-board a REXUS sounding rocket from Esrange Space Center. The experiment was completely designed and assembled by students from different countries under an international collaboration between the Université libre de Bruxelles (ULB) and the University of Naples Federico II. This student program called REXUS/BEXUS allows students to perform experiments in space science applications under the supervision of the European Space Agency (ESA). The objective of the CWIS Team was to visualize the Chemical Wave (CW) during the transient of the Soret effect. The CW is a concentration front that rapidly propagates under thermal gradient in a liquid mixture, and which marks the beginning of the chemical separation phenomenon by thermodiffusion (the separation process is itself named Soret effect, but is usually analyzed statically). The selected mixture was a solution of Ethylene Glycol in Water and concentration variation due to thermal gradients was recorded using a modified Fizeau interferometer, with modifications designed to enlarge a very small region of the test cell using cylindrical squeezing. We recorded more than 100 images with the chemical information and in this paper work we will show the final results of the sounding rocket experiment.

  12. Assessment of weighted quantile sum regression for modeling chemical mixtures and cancer risk.

    PubMed

    Czarnota, Jenna; Gennings, Chris; Wheeler, David C

    2015-01-01

    In evaluation of cancer risk related to environmental chemical exposures, the effect of many chemicals on disease is ultimately of interest. However, because of potentially strong correlations among chemicals that occur together, traditional regression methods suffer from collinearity effects, including regression coefficient sign reversal and variance inflation. In addition, penalized regression methods designed to remediate collinearity may have limitations in selecting the truly bad actors among many correlated components. The recently proposed method of weighted quantile sum (WQS) regression attempts to overcome these problems by estimating a body burden index, which identifies important chemicals in a mixture of correlated environmental chemicals. Our focus was on assessing through simulation studies the accuracy of WQS regression in detecting subsets of chemicals associated with health outcomes (binary and continuous) in site-specific analyses and in non-site-specific analyses. We also evaluated the performance of the penalized regression methods of lasso, adaptive lasso, and elastic net in correctly classifying chemicals as bad actors or unrelated to the outcome. We based the simulation study on data from the National Cancer Institute Surveillance Epidemiology and End Results Program (NCI-SEER) case-control study of non-Hodgkin lymphoma (NHL) to achieve realistic exposure situations. Our results showed that WQS regression had good sensitivity and specificity across a variety of conditions considered in this study. The shrinkage methods had a tendency to incorrectly identify a large number of components, especially in the case of strong association with the outcome.

  13. Evaluating exposures to complex mixtures of chemicals during a new production process in the plastics industry.

    PubMed

    Meijster, Tim; Burstyn, Igor; Van Wendel De Joode, Berna; Posthumus, Maarten A; Kromhout, Hans

    2004-08-01

    The goal of this study was to monitor emission of chemicals at a factory where plastics products were fabricated by a new robotic (impregnated tape winding) production process. Stationary and personal air measurements were taken to determine which chemicals were released and at what concentrations. Principal component analyses (PCA) and linear regression were used to determine the emission sources of different chemicals found in the air samples. We showed that complex mixtures of chemicals were released, but most concentrations were below Dutch exposure limits. Based on the results of the principal component analyses, the chemicals found were divided into three groups. The first group consisted of short chain aliphatic hydrocarbons (C2-C6). The second group included larger hydrocarbons (C9-C11) and some cyclic hydrocarbons. The third group contained all aromatic and two aliphatic hydrocarbons. Regression analyses showed that emission of the first group of chemicals was associated with cleaning activities and the use of epoxy resins. The second and third group showed strong association with the type of tape used in the new tape winding process. High levels of CO and HCN (above exposure limits) were measured on one occasion when a different brand of impregnated polypropylene sulphide tape was used in the tape winding process. Plans exist to drastically increase production with the new tape winding process. This will cause exposure levels to rise and therefore further control measures should be installed to reduce release of these chemicals.

  14. Assessment of Weighted Quantile Sum Regression for Modeling Chemical Mixtures and Cancer Risk

    PubMed Central

    Czarnota, Jenna; Gennings, Chris; Wheeler, David C

    2015-01-01

    In evaluation of cancer risk related to environmental chemical exposures, the effect of many chemicals on disease is ultimately of interest. However, because of potentially strong correlations among chemicals that occur together, traditional regression methods suffer from collinearity effects, including regression coefficient sign reversal and variance inflation. In addition, penalized regression methods designed to remediate collinearity may have limitations in selecting the truly bad actors among many correlated components. The recently proposed method of weighted quantile sum (WQS) regression attempts to overcome these problems by estimating a body burden index, which identifies important chemicals in a mixture of correlated environmental chemicals. Our focus was on assessing through simulation studies the accuracy of WQS regression in detecting subsets of chemicals associated with health outcomes (binary and continuous) in site-specific analyses and in non-site-specific analyses. We also evaluated the performance of the penalized regression methods of lasso, adaptive lasso, and elastic net in correctly classifying chemicals as bad actors or unrelated to the outcome. We based the simulation study on data from the National Cancer Institute Surveillance Epidemiology and End Results Program (NCI-SEER) case–control study of non-Hodgkin lymphoma (NHL) to achieve realistic exposure situations. Our results showed that WQS regression had good sensitivity and specificity across a variety of conditions considered in this study. The shrinkage methods had a tendency to incorrectly identify a large number of components, especially in the case of strong association with the outcome. PMID:26005323

  15. The synergistic toxicity of the multiple chemical mixtures: implications for risk assessment in the terrestrial environment.

    PubMed

    Chen, Chen; Wang, Yanhua; Qian, Yongzhong; Zhao, Xueping; Wang, Qiang

    2015-04-01

    The combined toxicity of five insecticides (chlorpyrifos, avermectin, imidacloprid, λ-cyhalothrin, and phoxim), two herbicides (atrazine and butachlor) and a heavy metal (cadmium) has been examined with the earthworm acute toxicity test. Toxicological interactions of these chemicals in four, five, six, seven, and eight-component mixtures were studied using the combination-index (CI) equation method. In four-component and five-component mixtures, the synergistic effects predominated at lower effect levels, while the patterns of interactions found in six, seven, and eight-component mixtures displayed synergism. The λ-CY+IMI+BUT+ATR+CPF+PHO combination displayed the most strongly synergistic interaction, with CI values ranging from 0.09 to 0.15. The nature of the interaction changes with the effect level and the relevance of synergistic effects increase with the complexity of the mixture. The CI method was compared with the classical models of concentration addition (CA) and independent action (IA) and we found that the CI method could accurately predict the combined toxicity. The predicted synergism resulted from co-existence of the pesticides and the heavy metal especially at low effect levels may have important implications in risk assessment for the real terrestrial environment.

  16. 21 CFR 1308.34 - Exempt anabolic steroid products.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Exempt anabolic steroid products. 1308.34 Section... SUBSTANCES Exempt Anabolic Steroid Products § 1308.34 Exempt anabolic steroid products. The list of compounds, mixtures, or preparations that contain an anabolic steroid that have been exempted by the Administrator...

  17. 21 CFR 1308.34 - Exempt anabolic steroid products.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 9 2014-04-01 2014-04-01 false Exempt anabolic steroid products. 1308.34 Section... SUBSTANCES Exempt Anabolic Steroid Products § 1308.34 Exempt anabolic steroid products. The list of compounds, mixtures, or preparations that contain an anabolic steroid that have been exempted by the...

  18. 21 CFR 1308.34 - Exempt anabolic steroid products.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 9 2011-04-01 2011-04-01 false Exempt anabolic steroid products. 1308.34 Section... SUBSTANCES Exempt Anabolic Steroid Products § 1308.34 Exempt anabolic steroid products. The list of compounds, mixtures, or preparations that contain an anabolic steroid that have been exempted by the...

  19. 21 CFR 1308.34 - Exempt anabolic steroid products.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 9 2012-04-01 2012-04-01 false Exempt anabolic steroid products. 1308.34 Section... SUBSTANCES Exempt Anabolic Steroid Products § 1308.34 Exempt anabolic steroid products. The list of compounds, mixtures, or preparations that contain an anabolic steroid that have been exempted by the...

  20. 21 CFR 1308.34 - Exempt anabolic steroid products.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 9 2013-04-01 2013-04-01 false Exempt anabolic steroid products. 1308.34 Section... SUBSTANCES Exempt Anabolic Steroid Products § 1308.34 Exempt anabolic steroid products. The list of compounds, mixtures, or preparations that contain an anabolic steroid that have been exempted by the...

  1. Cellular RNA is chemically modified by exposure to air pollution mixtures.

    PubMed

    Baldridge, Kevin C; Zavala, Jose; Surratt, Jason; Sexton, Kenneth G; Contreras, Lydia M

    2015-01-01

    RNAs are more susceptible to modifications than DNA, and chemical modifications in RNA have an effect on their structure and function. This study aimed to characterize chemical effects on total RNA in human A549 lung cells after exposure to elevated levels of major secondary air pollutants commonly found in urban locations, including ozone (O3), acrolein (ACR) and methacrolein (MACR). Enzyme-linked immunosorbent assays (ELISA) were used to measure levels of interleukin (IL)-8 in the growth media and 8-oxoguanine (8OG) levels in total cellular RNA, and lactate dehydrogenase (LDH) in the growth media was measured by a coupled enzymatic assay. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure levels of microRNA 10b (miR-10b). The study found that 1-h exposure to all tested pollutant mixtures consistently caused significant increases in the levels of 8OG in total RNA. In the case of 4 ppm O3 exposures, measured levels of IL-8, LDH and miR-10b each showed consistent trends between two independent trials, but varied among these three targets. After 1-h exposures to an ACR+MACR mixture, measured levels of IL-8, LDH and miR-10b showed variable results. For mixtures of O3+ACR+MACR, IL-8 measurements showed no change; miR-10b and LDH showed variable results. The results indicate that short-term high-concentration exposures to air pollution can cause RNA chemical modifications. Chemical modifications in RNAs could represent more consistent markers of cellular stress relative to other inflammation markers, such as IL-8 and LDH, and provide a new biomarker endpoint for mechanistic studies in toxicity of air pollution exposure.

  2. Determination of the Quantitative Composition of Mixtures of Substances and Chemical Reaction Products by Multidimensional Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gribov, L. A.; Baranov, V. I.; Mikhailov, I. V.

    2017-01-01

    We consider general questions arising in formulation of the problem of determining the quantitative composition of mixtures of substances and chemical reaction products as a function of time, using multidimensional spectroscopy data. We have analyzed the basic variants of the problem of quantitative standardless spectral analysis that are of practical importance, and propose algorithms for their solution. We show that the solution of the problem over the entire time interval is robust with respect to possible uncertainties in specifying the initial spectral data. The result obtained is quite satisfactory even when quantum beats are not only present but can even be observed. This allows us, based on the spectral data, to obtain a complete picture of the course of the chemical reaction and to determine the probability of chemical interconversions. The proposed algorithm allows us to construct time-dependent multidimensional surfaces of histograms showing the distribution of the concentrations found. The performance of the algorithms has been studied using computer experiments.

  3. Passive dosing of polycyclic aromatic hydrocarbon (PAH) mixtures to terrestrial springtails: linking mixture toxicity to chemical activities, equilibrium lipid concentrations, and toxic units.

    PubMed

    Schmidt, Stine N; Holmstrup, Martin; Smith, Kilian E C; Mayer, Philipp

    2013-07-02

    A 7-day mixture toxicity experiment with the terrestrial springtail Folsomia candida was conducted, and the effects were linked to three different mixture exposure parameters. Passive dosing from silicone was applied to tightly control exposure levels and compositions of 12 mixture treatments, containing the polycyclic aromatic hydrocarbons (PAHs) naphthalene, phenanthrene, and pyrene. Springtail lethality was then linked to sum chemical activities (∑a), sum equilibrium lipid concentrations (∑C(lipid eq.)), and sum toxic units (∑TU). In each case, the effects of all 12 mixture treatments could be fitted to one sigmoidal exposure-response relationship. The effective lethal chemical activity (La50) of 0.027 was well within the expected range for baseline toxicity of 0.01-0.1. Linking the effects to the lipid-based exposure parameter yielded an effective lethal concentration (LC(lipid eq 50)) of 133 mmol kg(-1) lipid in good correspondence with the lethal membrane burden for baseline toxicity (40-160 mmol kg(-1) lipid). Finally, the effective lethal toxic unit (LTU50) of 1.20 was rather close to the expected value of 1. Altogether, passive dosing provided tightly controlled mixture exposure in terms of both level and composition, while ∑a, ∑C(lipid eq.), and ∑TU allowed baseline toxicity to be linked to mixture exposure.

  4. Chemical Characterization and Toxicologic Evaluation of Airborne Mixtures: Chemical Characterization of Colored Signal Smokes

    DTIC Science & Technology

    1988-12-01

    undergo more chemical transformation than the green and yellow smoke mixes. 2-Methoxyaniline, naphtho-(l,2-d)- oxazole , 2-naphthol, andmethoxyphenyl... oxazole . Similarly, three similar compounds were tentatively assigned as C1 , C2, and C3 homologues of naphtha-(l,2-d)- oxazole . These assignments were...are observed, including 2 -methoxyaniline, naphtho - (1I, 2 -d) - oxazole , and methoxyphenylnaphthol (or a similar compound). 89 aO _’V 0. .. 0. a) 1.0

  5. Impact of Chemical Proportions on the Acute Neurotoxicity of a Mixture of Seven Carbamates in Preweanling and Adult Rats

    EPA Science Inventory

    Statistical design and environmental relevance are important aspects of studies of chemical mixtures, such as pesticides. We used a dose-additivity model to test experimentally the default assumptions of dose-additivity for two mixtures of seven N-methylcarbamates (carbaryl, carb...

  6. Aquatic toxicity of PAHs and PAH mixtures at saturation to benthic amphipods: linking toxic effects to chemical activity.

    PubMed

    Engraff, Maria; Solere, Clémentine; Smith, Kilian E C; Mayer, Philipp; Dahllöf, Ingela

    2011-04-01

    Organisms in marine sediments are usually exposed to mixtures of polycyclic aromatic hydrocarbons (PAHs), whereas risk assessment and management typically focus on the effects of single PAHs. This can lead to an underestimation of risk if the effects of single compounds are additive or synergistic. Because of the virtually infinite number of mixture-combinations, and the many different targeted organisms, it would be advantageous to have a model for the assessment of mixture effects. In this study we tested whether chemical activity, which drives the partitioning of PAHs into organisms, can be used to model the baseline toxicity of mixtures. Experiments were performed with two benthic amphipod species (Orchomonella pinguis and Corophium volutator), using passive dosing to control the external exposure of single PAHs and mixtures of three and four PAHs. The baseline toxicity of individual PAHs at water saturation generally increased with increasing chemical activity of the PAHs. For O. pinguis, the baseline toxicity of PAH mixtures was successfully described by the sum of chemical activities. Some compounds and mixtures showed a delayed expression of toxicity, highlighting the need to adjust the length of the experiment depending on the organism. On the other hand, some of the single compounds had a higher toxicity than expected, possibly due to the toxicity of PAH metabolites. We suggest that chemical activity of mixtures can, and should, be used in addition to toxicity data for single compounds in environmental risk assessment.

  7. A Four-Step and Four-Criteria Approach for Evaluating Evidence of Dose Addition in Chemical Mixture Toxicity

    EPA Science Inventory

    Dose addition is the most frequently-used component-based approach for predicting dose response for a mixture of toxicologically-similar chemicals and for statistical evaluation of whether the mixture response is consistent with dose additivity and therefore predictable from the ...

  8. Impact of Chemical Proportions on the Acute Neurotoxicity of a Mixture of Seven Carbamates in Preweanling and Adult Rats

    EPA Science Inventory

    Statistical design and environmental relevance are important aspects of studies of chemical mixtures, such as pesticides. We used a dose-additivity model to test experimentally the default assumptions of dose-additivity for two mixtures of seven N-methylcarbamates (carbaryl, carb...

  9. A Four-Step and Four-Criteria Approach for Evaluating Evidence of Dose Addition in Chemical Mixture Toxicity

    EPA Science Inventory

    Dose addition is the most frequently-used component-based approach for predicting dose response for a mixture of toxicologically-similar chemicals and for statistical evaluation of whether the mixture response is consistent with dose additivity and therefore predictable from the ...

  10. Emergence of life from multicomponent mixtures of chemicals: the case for experiments with cycling physicochemical gradients.

    PubMed

    Spitzer, Jan

    2013-04-01

    The emergence of life from planetary multicomponent mixtures of chemicals is arguably the most complicated and least understood natural phenomenon. The fact that living cells are non-equilibrium systems suggests that life can emerge only from non-equilibrium chemical systems. From an astrobiological standpoint, non-equilibrium chemical systems arise naturally when solar irradiation strikes rotating surfaces of habitable planets: the resulting cycling physicochemical gradients persistently drive planetary chemistries toward "embryonic" living systems and an eventual emergence of life. To better understand the factors that lead to the emergence of life, I argue for cycling non-equilibrium experiments with multicomponent chemical systems designed to represent the evolving chemistry of Hadean Earth ("prebiotic soups"). Specifically, I suggest experimentation with chemical engineering simulators of Hadean Earth to observe and analyze (i) the appearances and phase separations of surface active and polymeric materials as precursors of the first "cell envelopes" (membranes) and (ii) the accumulations, commingling, and co-reactivity of chemicals from atmospheric, oceanic, and terrestrial locations.

  11. Computational estimation of errors generated by lumping of physiologically-based pharmacokinetic (PBPK) interaction models of inhaled complex chemical mixtures

    EPA Science Inventory

    Many cases of environmental contamination result in concurrent or sequential exposure to more than one chemical. However, limitations of available resources make it unlikely that experimental toxicology will provide health risk information about all the possible mixtures to which...

  12. Computational estimation of errors generated by lumping of physiologically-based pharmacokinetic (PBPK) interaction models of inhaled complex chemical mixtures

    EPA Science Inventory

    Many cases of environmental contamination result in concurrent or sequential exposure to more than one chemical. However, limitations of available resources make it unlikely that experimental toxicology will provide health risk information about all the possible mixtures to which...

  13. Summer 2012 Testing and Analysis of the Chemical Mixture Methodology -- Part I

    SciTech Connect

    Glantz, Clifford S.; Yu, Xiao-Ying; Coggin, Rebekah L.; Ponder, Lashaundra A.; Booth, Alexander E.; Petrocchi, Achille J.; Horn, Sarah M.; Yao, Juan

    2012-07-01

    This report presents the key findings made by the Chemical Mixture Methodology (CMM) project team during the first stage of their summer 2012 testing and analysis of the CMM. The study focused on answering the following questions: o What is the percentage of the chemicals in the CMM Rev 27 database associated with each Health Code Number (HCN)? How does this result influence the relative importance of acute HCNs and chronic HCNs in the CMM data set? o What is the benefit of using the HCN-based approach? Which Modes of Action and Target Organ Effects tend to be important in determining the HCN-based Hazard Index (HI) for a chemical mixture? o What are some of the potential issues associated with the current HCN-based approach? What are the opportunities for improving the performance and/or technical defensibility of the HCN-based approach? How would those improvements increase the benefit of using the HCN-based approach? o What is the Target Organ System Effect approach and how can it be used to improve upon the current HCN-based approach? How does the benefits users would derive from using the Target Organ System Approach compare to the benefits available from the current HCN-based approach?

  14. Modeling and analysis of time-dependent processes in a chemically reactive mixture

    NASA Astrophysics Data System (ADS)

    Ramos, M. P.; Ribeiro, C.; Soares, A. J.

    2017-08-01

    In this paper, we study the propagation of sound waves and the dynamics of local wave disturbances induced by spontaneous internal fluctuations in a reactive mixture. We consider a non-diffusive, non-heat conducting and non-viscous mixture described by an Eulerian set of evolution equations. The model is derived from the kinetic theory in a hydrodynamic regime of a fast chemical reaction. The reactive source terms are explicitly computed from the kinetic theory and are built in the model in a proper way. For both time-dependent problems, we first derive the appropriate dispersion relation, which retains the main effects of the chemical process, and then investigate the influence of the chemical reaction on the properties of interest in the problems studied here. We complete our study by developing a rather detailed analysis using the Hydrogen-Chlorine system as reference. Several numerical computations are included illustrating the behavior of the phase velocity and attenuation coefficient in a low-frequency regime and describing the spectrum of the eigenmodes in the small wavenumber limit.

  15. 10 CFR 32.18 - Manufacture, distribution and transfer of exempt quantities of byproduct material: Requirements...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Manufacture, distribution and transfer of exempt quantities of byproduct material: Requirements for license. 32.18 Section 32.18 Energy NUCLEAR REGULATORY... chemical elements, compounds, or mixtures, tissue samples, bioassay samples, counting standards, plated or...

  16. Chemical Oxidation of Complex PAH Mixtures by Base-activated Sodium Persulfate

    NASA Astrophysics Data System (ADS)

    Hauswirth, S.; Miller, C. T.

    2013-12-01

    In situ chemical oxidation (ISCO) is an attractive approach for the remediation of recalcitrant soil and groundwater contaminants. One oxidant that has received significant recent attention is sodium persulfate, which has several advantages, including a relatively long lifetime in porous media, the ability to destroy a wide-range of chemical contaminants, and a high oxidation potential. In this study, we investigated the chemical mechanisms associated with base-activated persulfate oxidation of polycyclic aromatic hydrocarbons (PAHs) and assessed the applicability of persulfate to the remediation of porous media contaminated with non-aqueous phase liquid (NAPL) PAH mixtures. Batch experiments were conducted to determine the oxidation kinetics for individual PAH compounds, synthetic PAH mixtures, and manufactured gas plant (MGP) tars. Additional experiments were conducted with added surfactants (Triton X-100, Triton X-45, and Tween 80) to increase PAH mass transfer from the NAPL to the aqueous phase, and with radical scavengers (ethanol and tert-butyl alcohol) to identify the reactive species responsible for degradation. Degradation of total PAHs in the NAPL experiments was as high as 70%. The addition of surfactant increased initial PAH degradation rates, but also greatly increased the rate of base consumption, thereby reducing the overall fraction degraded. The degradation of individual PAHs within the NAPLs varied significantly, with the masses of some compounds remaining largely unchanged. The results of the radical scavenger and single PAH experiments suggest that the observed pattern of degradation in PAH mixtures is the result of a combination of mass transfer considerations and competition for radical species.

  17. Characterization of dimethylsulfoxide/glycerol mixtures: a binary solvent system for the study of "friction-dependent" chemical reactivity.

    PubMed

    Angulo, Gonzalo; Brucka, Marta; Gerecke, Mario; Grampp, Günter; Jeannerat, Damien; Milkiewicz, Jadwiga; Mitrev, Yavor; Radzewicz, Czesław; Rosspeintner, Arnulf; Vauthey, Eric; Wnuk, Paweł

    2016-07-21

    The properties of binary mixtures of dimethylsulfoxide and glycerol, measured using several techniques, are reported. Special attention is given to those properties contributing or affecting chemical reactions. In this respect the investigated mixture behaves as a relatively simple solvent and it is especially well suited for studies on the influence of viscosity on chemical reactivity. This is due to the relative invariance of the dielectric properties of the mixture. However, special caution must be taken with specific solvation, as the hydrogen-bonding properties of the solvent change with the molar fraction of glycerol.

  18. Systematic proteomic approach to characterize the impacts of chemical interactions on protein and cytotoxicity responses to metal mixture exposures.

    PubMed

    Ge, Yue; Bruno, Maribel; Wallace, Kathleen; Leavitt, Sharon; Andrews, Debora; Spassova, Maria A; Xi, Mingyu; Roy, Anindya; Haykal-Coates, Najwa; Lefew, William; Swank, Adam; Winnik, Witold M; Chen, Chao; Woodard, Jonne; Farraj, Aimen; Teichman, Kevin Y; Ross, Jeffrey A

    2015-01-02

    Chemical interactions have posed a big challenge in toxicity characterization and human health risk assessment of environmental mixtures. To characterize the impacts of chemical interactions on protein and cytotoxicity responses to environmental mixtures, we established a systems biology approach integrating proteomics, bioinformatics, statistics, and computational toxicology to measure expression or phosphorylation levels of 21 critical toxicity pathway regulators and 445 downstream proteins in human BEAS-2B cells treated with 4 concentrations of nickel, 2 concentrations each of cadmium and chromium, as well as 12 defined binary and 8 defined ternary mixtures of these metals in vitro. Multivariate statistical analysis and mathematical modeling of the metal-mediated proteomic response patterns showed a high correlation between changes in protein expression or phosphorylation and cellular toxic responses to both individual metals and metal mixtures. Of the identified correlated proteins, only a small set of proteins including HIF-1α is likely to be responsible for selective cytotoxic responses to different metals and metals mixtures. Furthermore, support vector machine learning was utilized to computationally predict protein responses to uncharacterized metal mixtures using experimentally generated protein response profiles corresponding to known metal mixtures. This study provides a novel proteomic approach for characterization and prediction of toxicities of metal and other chemical mixtures.

  19. Toxicology of chemical mixtures: experimental approaches, underlying concepts, and some results.

    PubMed

    Yang, R S; Hong, H L; Boorman, G A

    1989-12-01

    The toxicology of chemical mixtures will be the toxicology of the 1990s and beyond. While this branch of toxicology most closely reflects the actual human exposure situation, there is yet no standard protocol or consensus methodology for investigating the toxicology of mixtures. Thus, in this emerging science, experimentation is required just to develop a broadly applicable evaluation system. Several examples are discussed to illustrate the different experimental designs and the concepts behind each. These include the health effects studies of Love Canal soil samples, the Lake Ontario Coho salmon, the water samples repurified from secondary sewage in the city of Denver Potable Water Reuse Demonstration Plant, and the National Toxicology Program (NTP) effort on a mixture of 25 frequently detected groundwater contaminants derived from hazardous waste disposal sites. In the last instance, an extensive research program has been ongoing for the last 2 years at the NTP, encompassing general toxicology, immunotoxicology, developmental and reproductive toxicology, biochemical toxicology, myelotoxicology, genetic toxicology, neurobehavioral toxicology, and hepato- and renal toxicology.

  20. Toxicology of chemical mixtures: Experimental approaches, underlying concepts, and some results

    SciTech Connect

    Yang, R.S.; Long, H.L.; Boorman, G.A.

    1990-07-01

    The toxicology of chemical mixtures will be the toxicology of the 1990s and beyond. While this branch of toxicology most closely reflects the actual human exposure situation, as yet there is no standard protocol or consensus methodology for investigating the toxicology of mixtures. Thus, in this emerging science, experimentation is required just to develop a broadly applicable evaluation system. Several examples are discussed to illustrate the different experimental designs and the concepts behind each. These include the health effects studies of Love Canal soil samples, the Lake Ontario Coho salmon, the water samples repurified from secondary sewage in the city of Denver Potable Water Reuse Demonstration Plant, and the National Toxicology Program (NTP) effort on a mixture of 25 frequently detected groundwater contaminants derived from hazardous waste disposal sites. In the last instance, an extensive research program has been ongoing for the last two years at the NTP, encompassing general toxicology, immunotoxicology, developmental and reproductive toxicology, biochemical toxicology, myelotoxicology, genetic toxicology, neurobehavioral toxicology, and hepato- and renal toxicology.

  1. Hazard and risk assessment of chemical mixtures using the toxic equivalency factor approach.

    PubMed Central

    Safe, S H

    1998-01-01

    There is considerable public, regulatory, and scientific concern regarding human exposure to endocrine-disrupting chemicals, which include compounds that directly modulate steroid hormone receptor pathways (estrogens, antiestrogens, androgens, antiandrogens) and aryl hydrocarbon receptor (AhR) agonists, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. Based on quantitative structure-activity relationships for both AhR and estrogen receptor (ER) agonists, the relative potency (RP) of individual compounds relative to a standard (e.g. TCDD and 17-beta-estradiol) have been determined for several receptor-mediated responses. Therefore, the TCDD or estrogenic equivalent (TEQ or EQ, respectively) of a mixture is defined as TEQ = sigma[T(i)]xRP(i)or EQ=sigma[E(i)]xRP(i), where T(i) and E(i) are concentrations of individual AhR or ER agonists in any mixture. This approach for risk assessment of endocrine-disrupting mixtures assumes that for each endocrine response pathway, the effects of individual compounds are essentially additive. This paper will critically examine the utility of the TEQ/EQ approach for risk assessment, the validity of the assumptions used for this approach, and the problems associated with comparing low dose exposures to xeno and natural (dietary) endocrine disruptors. PMID:9703492

  2. Phase transition and chemical decomposition of liquid carbon dioxide and nitrogen mixture under extreme conditions

    NASA Astrophysics Data System (ADS)

    Xiao-Xu, Jiang; Guan-Yu, Chen; Yu-Tong, Li; Xin-Lu, Cheng; Cui-Ming, Tang

    2016-02-01

    Thermodynamic and chemical properties of liquid carbon dioxide and nitrogen (CO2-N2) mixture under the conditions of extremely high densities and temperatures are studied by using quantum molecular dynamic (QMD) simulations based on density functional theory including dispersion corrections (DFT-D). We present equilibrium properties of liquid mixture for 112 separate density and temperature points, by selecting densities ranging from ρ = 1.80 g/cm3 to 3.40 g/cm3 and temperatures from T = 500 K to 8000 K. In the range of our study, the liquid CO2-N2 mixture undergoes a continuous transition from molecular to atomic fluid state and liquid polymerization inferred from pair correlation functions (PCFs) and the distribution of various molecular components. The insulator-metal transition is demonstrated by means of the electronic density of states (DOS). Project supported by the National Natural Science Foundation of China (Grant Nos. 11374217, 11135012, and 11375262) and the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics (Grant No. 11176020).

  3. Review of the toxicity of chemical mixtures: Theory, policy, and regulatory practice.

    PubMed

    McCarty, L S; Borgert, C J

    2006-07-01

    An analysis of current mixture theory, policy, and practice was conducted by examining standard reference texts, regulatory guidance documents, and journal articles. Although this literature contains useful theoretical concepts, clear definitions of most terminology, and well developed protocols for study design and statistical analysis, no general theoretical basis for the mechanisms and interactions of mixture toxicity could be discerned. There is also a poor understanding of the relationship between exposure-based and internal received dose metrics. This confounds data interpretation and limits reliable determinations of the nature and extent of additivity. The absence of any generally accepted classification scheme for either modes/mechanisms of toxic action or of mechanisms of toxicity interactions is problematic as it produces a cycle in which research and policy are interdependent and mutually limiting. Current regulatory guidance depends heavily on determination of toxicological similarity concluded from the presence of a few prominent constituents, assumed from a common toxicological effect, or presumed from an alleged similar toxic mode/mechanism. Additivity, or the lack of it, is largely based on extrapolation of existing knowledge for single chemicals in this context. Thus, regulatory risk assessment protocols lack authoritative theoretical underpinnings, creating substantial uncertainty. Development of comprehensive classification schemes for modes/mechanisms of toxic action and mechanisms of interaction is needed to ensure a sound theoretical foundation for mixture-related regulatory activity and provide a firm basis for iterative hypothesis development and experimental testing.

  4. Evaluating the aquatic toxicity of complex organic chemical mixtures: lessons learned from polycyclic aromatic hydrocarbon and petroleum hydrocarbon case studies.

    PubMed

    Landrum, Peter F; Chapman, Peter M; Neff, Jerry; Page, David S

    2012-04-01

    Experimental designs for evaluating complex mixture toxicity in aquatic environments can be highly variable and, if not appropriate, can produce and have produced data that are difficult or impossible to interpret accurately. We build on and synthesize recent critical reviews of mixture toxicity using lessons learned from 4 case studies, ranging from binary to more complex mixtures of primarily polycyclic aromatic hydrocarbons and petroleum hydrocarbons, to provide guidance for evaluating the aquatic toxicity of complex mixtures of organic chemicals. Two fundamental requirements include establishing a dose-response relationship and determining the causative agent (or agents) of any observed toxicity. Meeting these 2 requirements involves ensuring appropriate exposure conditions and measurement endpoints, considering modifying factors (e.g., test conditions, test organism life stages and feeding behavior, chemical transformations, mixture dilutions, sorbing phases), and correctly interpreting dose-response relationships. Specific recommendations are provided. Copyright © 2011 SETAC.

  5. Effect of chemical interactions in pentachlorophenol mixtures on skin and membrane transport.

    PubMed

    Baynes, Ronald E; Brooks, James D; Mumtaz, Moiz; Riviere, Jim E

    2002-10-01

    Pentachlorophenol (PCP) has been widely used as a pesticide, and topical exposure to a chemical mixture can alter its dermal absorption. The purpose of this study was to evaluate the influence of single and binary solvent systems (ethanol, EtOH, and water), a surfactant (6% sodium lauryl sulfate, SLS), and a rubifacient/vasodilator (1.28% methyl nicotinate, MNA) on PCP membrane transport, and to correlate these effects with physiochemical characteristics of the PCP mixtures. Partitioning, diffusion, and absorption parameters of (14)C-PCP at low (4 microg/cm(2)) and high (40 microg/cm(2)) doses were assessed in porcine skin and silastic membranes in vitro. In these 8-h, flow-through diffusion studies, PCP was dosed with the following vehicles: 100% EtOH, 100% water, 40% EtOH + 60% water, 40% EtOH + 60% water + SLS, 40% EtOH + 60% water + MNA, and 40% EtOH + 60% water + SLS + MNA. PCP absorption ranged from 1.55-15.62% for the high dose and 0.43-7.20% for the low dose. PCP absorption, flux, and apparent permeability were influenced by PCP solubility, and PCP apparent permeability was correlated with log PC (r2 = 0.66). Although PCP was very soluble in pure ethanol (100%), this vehicle evaporated very rapidly, and PCP absorption in ethanol was the lowest with this vehicle when compared to pure water (100%) or aqueous ethanol mixtures in general. MNA had no significant effect on membrane absorption or relative permeability R(P) in aqueous ethanol solutions, but the presence of the surfactant, SLS, significantly reduced PCP absorption and R(P) in both membrane systems. In conclusion, these studies demonstrated that modification in mixture composition with either a solvent and/or a surfactant can influence PCP diffusion in skin. Physicochemical interactions between these mixture components on the skin surface and stratum corneum contributed significantly to PCP transport, and these interactions were identified by simultaneously assessing chemical diffusion in biological

  6. Chemical structure influence on NAPL mixture nonideality evolution, rate-limited dissolution, and contaminant mass flux.

    PubMed

    Padgett, Mark C; Tick, Geoffrey R; Carroll, Kenneth C; Burke, William R

    2017-03-01

    The influence of chemical structure on NAPL mixture nonideality evolution, rate-limited dissolution, and contaminant mass flux was examined. The variability of measured and UNIFAC modeled NAPL activity coefficients as a function of mole fraction was compared for two NAPL mixtures containing structurally-different contaminants of concern including toluene (TOL) or trichloroethene (TCE) within a hexadecane (HEXDEC) matrix. The results showed that dissolution from the NAPL mixtures transitioned from ideality for mole fractions >0.05 to nonideality as mole fractions decreased. In particular, the TCE generally exhibited more ideal dissolution behavior except at lower mole fractions, and may indicate greater structural/polarity similarity between the two compounds. Raoult's Law and UNIFAC generally under-predicted the batch experiment results for TOL:HEXDEC mixtures especially for mole fractions ≤0.05. The dissolution rate coefficients were similar for both TOL and TCE over all mole fractions tested. Mass flux reduction (MFR) analysis showed that more efficient removal behavior occurred for TOL and TCE with larger mole fractions compared to the lower initial mole fraction mixtures (i.e. <0.2). However, compared to TOL, TCE generally exhibited more efficient removal behavior over all mole fractions tested and may have been the result of structural and molecular property differences between the compounds. Activity coefficient variability as a function of mole fraction was quantified through regression analysis and incorporated into dissolution modeling analyses for the dynamic flushing experiments. TOL elution concentrations were modeled (predicted) reasonable well using ideal and equilibrium assumptions, but the TCE elution concentrations could not be predicted using the ideal model. Rather, the dissolution modeling demonstrated that TCE elution was better described by the nonideal model whereby NAPL-phase activity coefficient varied as a function of COC mole fraction

  7. 21 CFR 1308.23 - Exemption of certain chemical preparations; application.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... special research purposes and not for general administration to a human being or other animal, if the... designation of the preparation or mixture; (4) The complete qualitative and quantitative composition of...

  8. 21 CFR 1308.23 - Exemption of certain chemical preparations; application.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... special research purposes and not for general administration to a human being or other animal, if the... designation of the preparation or mixture; (4) The complete qualitative and quantitative composition of...

  9. 21 CFR 1308.23 - Exemption of certain chemical preparations; application.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... special research purposes and not for general administration to a human being or other animal, if the... designation of the preparation or mixture; (4) The complete qualitative and quantitative composition of...

  10. 21 CFR 1308.23 - Exemption of certain chemical preparations; application.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... special research purposes and not for general administration to a human being or other animal, if the... designation of the preparation or mixture; (4) The complete qualitative and quantitative composition of...

  11. 21 CFR 1308.23 - Exemption of certain chemical preparations; application.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... special research purposes and not for general administration to a human being or other animal, if the... designation of the preparation or mixture; (4) The complete qualitative and quantitative composition of the...

  12. Endocrine disrupting chemicals in mixture and obesity, diabetes and related metabolic disorders

    PubMed Central

    Le Magueresse-Battistoni, Brigitte; Labaronne, Emmanuel; Vidal, Hubert; Naville, Danielle

    2017-01-01

    Obesity and associated metabolic disorders represent a major societal challenge in health and quality of life with large psychological consequences in addition to physical disabilities. They are also one of the leading causes of morbidity and mortality. Although, different etiologic factors including excessive food intake and reduced physical activity have been well identified, they cannot explain the kinetics of epidemic evolution of obesity and diabetes with prevalence rates reaching pandemic proportions. Interestingly, convincing data have shown that environmental pollutants, specifically those endowed with endocrine disrupting activities, could contribute to the etiology of these multifactorial metabolic disorders. Within this review, we will recapitulate characteristics of endocrine disruption. We will demonstrate that metabolic disorders could originate from endocrine disruption with a particular focus on convincing data from the literature. Eventually, we will present how handling an original mouse model of chronic exposition to a mixture of pollutants allowed demonstrating that a mixture of pollutants each at doses beyond their active dose could induce substantial deleterious effects on several metabolic end-points. This proof-of-concept study, as well as other studies on mixtures of pollutants, stresses the needs for revisiting the current threshold model used in risk assessment which does not take into account potential effects of mixtures containing pollutants at environmental doses, e.g., the real life exposure. Certainly, more studies are necessary to better determine the nature of the chemicals to which humans are exposed and at which level, and their health impact. As well, research studies on substitute products are essential to identify harmless molecules. PMID:28588754

  13. Comparative Study of Risk Assessment Approaches Based on Different Methods for Deriving DNEL and PNEC of Chemical Mixtures

    NASA Astrophysics Data System (ADS)

    Kim, Jongwoon; Kim, Sanghun; Schaumann, Gabriele E.

    Most living organisms are actually exposed to chemical mixtures rather than individual substances. But current chemical risk assessment frequently focuses on the single chemical substances. The European Union presented some methods in the draft technical guidance notes for deriving DNEL (Derived No Effect Level) and PNEC (Predicted No Effect Concentration) for risk assessment of mixtures. This case study shows that the differences of DNELs and PNECs of mixtures (2 coating materials) based on two methods (KCC and CR methods) and explains why such differences are generated. The differences of DNELs and PNECs of the mixtures based on the two methods were estimated by 1.21 and 2.31 times respectively. Through the theoretical analysis on influence factors affecting DNEL and PNEC, it could be recognized that the difference between two methods can significantly increase in proportion to the number of substances having similar hazard and weight fraction.

  14. Chemical Discrimination in Turbulent Gas Mixtures with MOX Sensors Validated by Gas Chromatography-Mass Spectrometry

    PubMed Central

    Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

    2014-01-01

    Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance. PMID:25325339

  15. Qualitative Analysis of Fourteen White Solids and Two Mixtures Using Household Chemicals

    NASA Astrophysics Data System (ADS)

    Oliver-Hoyo, Maria; Allen, Deedee; Solomon, Sally; Brook, Bryan; Ciraolo, Justine; Daly, Shawn; Jackson, Leia

    2001-11-01

    This is a revised and expanded version of a previously published qualitative analysis scheme for the identification of 11 white solids using materials readily available in drugstores, supermarkets, or variety stores. Phenolphthalein has been eliminated because the FDA banned its use in over-the-counter laxatives; instead, tests for pH are conducted using red cabbage indicator. Once commonly used by diabetics to test urine, copper reduction tablets are no longer widely available and are replaced by a mixture of ingredients. Three white solids and two types of mixtures, commercial antacid tablets and baking powder, have been added to the scheme. All procedures can be done with the simplest of equipment. Amounts of solids are measured volumetrically and heat is supplied by contact with hot tap water. The use of household chemicals reduces waste disposal problems while making the experiment suitable for a laboratory exercise in a distance-learning course. This experiment can be adapted for many levels of instruction. In middle school only the safer tests should be included; honors general chemistry students can be asked to design an analysis scheme for the 14 household chemicals.

  16. Chemical discrimination in turbulent gas mixtures with MOX sensors validated by gas chromatography-mass spectrometry.

    PubMed

    Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

    2014-10-16

    Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance.

  17. Allium-test as a tool for toxicity testing of environmental radioactive-chemical mixtures

    NASA Astrophysics Data System (ADS)

    Oudalova, A. A.; Geras’kin, S. A.; Dikareva, N. S.; Pyatkova, S. V.

    2017-01-01

    Bioassay-based approaches have been propagated to assess toxicity of unknown mixtures of environmental contaminants, but it was rarely applied in cases of chemicals with radionuclides combinations. Two Allium-test studies were performed to assess environmental impact from potential sources of combined radioactive-chemical pollution. Study sites were located at nuclear waste storage facilities in European and in Far-Eastern parts of Russia. As environmental media under impact, waters from monitor wells and nearby water bodies were tested. Concentrations of some chemicals and radionuclides in the samples collected enhanced the permitted limits. Cytogenetic and cytotoxic effects were used as biological endpoints, namely, frequency and spectrum of chromosome aberrations and mitotic abnormalities in anatelophase cells as well as mitotic activity in Allium root tips. Sample points were revealed where waters have an enhanced mutagenic potential. The findings obtained could be used to optimize monitoring system and advance decision making on management and rehabilitation of industrial sites. The Allium-test could be recommended and applied as an effective tool for toxicity testing in case of combined contamination of environmental compartments with radionuclides and chemical compounds.

  18. Designation of Alpha-Phenylacetoacetonitrile (APAAN), a Precursor Chemical Used in the Illicit Manufacture of Phenylacetone, Methamphetamine, and Amphetamine, as a List I Chemical. Final rule.

    PubMed

    2017-07-14

    The Drug Enforcement Administration (DEA) is finalizing the designation of the chemical alpha-phenylacetoacetonitrile (APAAN) and its salts, optical isomers, and salts of optical isomers, as a list I chemical under the Controlled Substances Act (CSA). The DEA proposed control of APAAN, due to its use in clandestine laboratories to illicitly manufacture the schedule II controlled substances phenylacetone (also known as phenyl-2-propanone or P2P), methamphetamine, and amphetamine. This rulemaking finalizes, without change, the control of APAAN as a list I chemical. This action does not establish a threshold for domestic and international transactions of APAAN. As such, all transactions involving APAAN, regardless of size, shall be regulated. In addition, chemical mixtures containing APAAN are not exempt from regulatory requirements at any concentration. Therefore, all transactions of chemical mixtures containing any quantity of APAAN shall be regulated pursuant to the CSA. However, manufacturers may submit an application for exemption for those mixtures that do not qualify for automatic exemption.

  19. Testing for Additivity in Chemical Mixtures Using a Fixed-Ratio Ray Design and Statistical Equivalence Testing Methods

    EPA Science Inventory

    Fixed-ratio ray designs have been used for detecting and characterizing interactions of large numbers of chemicals in combination. Single chemical dose-response data are used to predict an “additivity curve” along an environmentally relevant ray. A “mixture curve” is estimated fr...

  20. Testing for Additivity in Chemical Mixtures Using a Fixed-Ratio Ray Design and Statistical Equivalence Testing Methods

    EPA Science Inventory

    Fixed-ratio ray designs have been used for detecting and characterizing interactions of large numbers of chemicals in combination. Single chemical dose-response data are used to predict an “additivity curve” along an environmentally relevant ray. A “mixture curve” is estimated fr...

  1. Effects of biologically-active chemical mixtures on fish in a wastewater-impacted urban stream

    USGS Publications Warehouse

    Barber, L.B.; Brown, G.K.; Nettesheim, T.G.; Murphy, E.W.; Bartell, S.E.; Schoenfuss, H.L.

    2011-01-01

    Stream flow in urban aquatic ecosystems often is maintained by water-reclamation plant (WRP) effluents that contain mixtures of natural and anthropogenic chemicals that persist through the treatment processes. In effluent-impacted streams, aquatic organisms such as fish are continuously exposed to biologically-active chemicals throughout their life cycles. The North Shore Channel of the Chicago River (Chicago, Illinois) is part of an urban ecosystem in which > 80% of the annual flow consists of effluent from the North Side WRP. In this study, multiple samplings of the effluent and stream water were conducted and fish (largemouth bass and carp) were collected on 2 occasions from the North Shore Channel. Fish also were collected once from the Outer Chicago Harbor in Lake Michigan, a reference site not impacted by WRP discharges. Over 100 organic chemicals with differing behaviors and biological effects were measured, and 23 compounds were detected in all of the water samples analyzed. The most frequently detected and highest concentration (> 100 ??g/L) compounds were ethylenediaminetetraacetic acid and 4-nonylphenolmono-to-tetraethoxycarboxylic acids. Other biologically-active chemicals including bisphenol A, 4-nonylphenol, 4-nonylphenolmono-to-tetraethoxylates, 4- tert-octylphenol, and 4- tert-octylphenolmono-to-tetraethoxylates were detected at lower concentrations (< 5 ??g/L). The biogenic steroidal hormones 17??-estradiol, estrone, testosterone, 4-androstene-3,17-dione, and cis-androsterone were detected at even lower concentrations (< 0.005 ??g/L). There were slight differences in concentrations between the North Side WRP effluent and the North Shore Channel, indicating minimal in-stream attenuation. Fish populations are continuously exposed to mixtures of biologically-active chemicals because of the relative persistency of the chemicals with respect to stream hydraulic residence time, and the lack of a fresh water source for dilution. The majority of male fish

  2. Effects of biologically-active chemical mixtures on fish in a wastewater-impacted urban stream.

    PubMed

    Barber, Larry B; Brown, Gregory K; Nettesheim, Todd G; Murphy, Elizabeth W; Bartell, Stephen E; Schoenfuss, Heiko L

    2011-10-15

    Stream flow in urban aquatic ecosystems often is maintained by water-reclamation plant (WRP) effluents that contain mixtures of natural and anthropogenic chemicals that persist through the treatment processes. In effluent-impacted streams, aquatic organisms such as fish are continuously exposed to biologically-active chemicals throughout their life cycles. The North Shore Channel of the Chicago River (Chicago, Illinois) is part of an urban ecosystem in which >80% of the annual flow consists of effluent from the North Side WRP. In this study, multiple samplings of the effluent and stream water were conducted and fish (largemouth bass and carp) were collected on 2 occasions from the North Shore Channel. Fish also were collected once from the Outer Chicago Harbor in Lake Michigan, a reference site not impacted by WRP discharges. Over 100 organic chemicals with differing behaviors and biological effects were measured, and 23 compounds were detected in all of the water samples analyzed. The most frequently detected and highest concentration (>100μg/L) compounds were ethylenediaminetetraacetic acid and 4-nonylphenolmono-to-tetraethoxycarboxylic acids. Other biologically-active chemicals including bisphenol A, 4-nonylphenol, 4-nonylphenolmono-to-tetraethoxylates, 4-tert-octylphenol, and 4-tert-octylphenolmono-to-tetraethoxylates were detected at lower concentrations (<5μg/L). The biogenic steroidal hormones 17β-estradiol, estrone, testosterone, 4-androstene-3,17-dione, and cis-androsterone were detected at even lower concentrations (<0.005μg/L). There were slight differences in concentrations between the North Side WRP effluent and the North Shore Channel, indicating minimal in-stream attenuation. Fish populations are continuously exposed to mixtures of biologically-active chemicals because of the relative persistency of the chemicals with respect to stream hydraulic residence time, and the lack of a fresh water source for dilution. The majority of male fish exhibited

  3. Effects of biologically-active chemical mixtures on fish in a wastewater-impacted urban stream

    USGS Publications Warehouse

    Barber, Larry B.; Brown, Gregory K.; Nettesheim, Todd G.; Murphy, Elizabeth W.; Bartell, Stephen E.; Schoenfuss, Heiko L.

    2011-01-01

    Stream flow in urban aquatic ecosystems often is maintained by water-reclamation plant (WRP) effluents that contain mixtures of natural and anthropogenic chemicals that persist through the treatment processes. In effluent-impactedstreams, aquatic organisms such as fish are continuously exposed to biologically-activechemicals throughout their life cycles. The North Shore Channel of the Chicago River (Chicago, Illinois) is part of an urban ecosystem in which > 80% of the annual flow consists of effluent from the North Side WRP. In this study, multiple samplings of the effluent and stream water were conducted and fish (largemouth bass and carp) were collected on 2 occasions from the North Shore Channel. Fish also were collected once from the Outer Chicago Harbor in Lake Michigan, a reference site not impacted by WRP discharges. Over 100 organic chemicals with differing behaviors and biological effects were measured, and 23 compounds were detected in all of the water samples analyzed. The most frequently detected and highest concentration (> 100 μg/L) compounds were ethylenediaminetetraacetic acid and 4-nonylphenolmono-to-tetraethoxycarboxylic acids. Other biologically-activechemicals including bisphenol A, 4-nonylphenol, 4-nonylphenolmono-to-tetraethoxylates, 4-tert-octylphenol, and 4-tert-octylphenolmono-to-tetraethoxylates were detected at lower concentrations (cis-androsterone were detected at even lower concentrations (< 0.005 μg/L). There were slight differences in concentrations between the North Side WRP effluent and the North Shore Channel, indicating minimal in-stream attenuation. Fish populations are continuously exposed to mixtures of biologically-activechemicals because of the relative persistency of the chemicals with respect to stream hydraulic residence time, and the lack of a fresh water source for dilution. The majority of male fish exhibited vitellogenin induction, a physiological response consistent with exposure to estrogenic compounds. Tissue

  4. Chemical TOPAZ: Modifications to the heat transfer code TOPAZ: The addition of chemical reaction kinetics and chemical mixtures

    SciTech Connect

    Nichols, A.L. III.

    1990-06-07

    This is a report describing the modifications which have been made to the heat flow code TOPAZ to allow the inclusion of thermally controlled chemical kinetics. This report is broken into parts. The first part is an introduction to the general assumptions and theoretical underpinning that were used to develop the model. The second section describes the changes that have been implemented into the code. The third section is the users manual for the input for the code. The fourth section is a compilation of hints, common errors, and things to be aware of while you are getting started. The fifth section gives a sample problem using the new code. This manual addenda is written with the presumption that most readers are not fluent with chemical concepts. Therefore, we shall in this section endeavor to describe the requirements that must be met before chemistry can occur and how we have modeled the chemistry in the code.

  5. Probabilistic Human Health Risk Assessment of Chemical Mixtures: Hydro-Toxicological Interactions and Controlling Factors

    NASA Astrophysics Data System (ADS)

    Henri, C.; Fernandez-Garcia, D.; de Barros, F.

    2014-12-01

    Improper disposals of hazardous wastes in most industrial countries give rise to severe groundwater contamination problems that can lead to adverse health effects in humans. Therefore risk assessment methods play an important role in population protection by (1) quantifying the impact on human health of an aquifer contamination and (2) aiding the decision making process of to better manage our groundwater resources. Many reactive components such as chlorinated solvent or nitrate potentially experience attenuation processes under common geochemical conditions. Based on this, monitored natural attenuation has become nowadays an attractive remediation solution. However, in some cases, intermediate degradation products can constitute noxious chemical compounds before reaching a harmless chemical form. In these cases, the joint effect of advection-dispersion transport and the species-dependent kinetic reactions and toxicity will dictate the relative importance of the degradation byproducts to the total risk. This renders the interpretation of risk a non-trivial task. In this presentation, we quantify, through a probabilistic framework, the human health risk posed by a chemical mixture in a heterogeneous aquifer. This work focuses on a Perchloroethylene contamination problem followed by the first-order production/biodegradation of its daughter species Trichloroethylene, Dichloroethylene and Vinyl Chlorine that is known to be highly toxic. Uncertainty on the hydraulic conductivity field is considered through a Monte Carlo scheme. A comparative description of human health risk metrics as a function of aquifer heterogeneity and contaminant injection mode is provided by means of a spatial characterization of the lower-order statistical moments and empirical probability density functions of both individual and total risks. Interestingly, we show that the human health risk of a chemical mixture is mainly controlled by a modified Damköhler number that express the joint effect

  6. Experimental EOS and Chemical Studies of High-Pressure Detonation Products and Product Mixtures

    SciTech Connect

    Zaug, J M; Fried, L E; Crowhurst, J C; Hansen, D W; Howard, W M; Lee, G S; Pagoria, P F; Abramson, E H

    2002-07-01

    We present equation of state results from impulsively stimulated light scattering (ISLS) experiments conducted in diamond anvil cells on pure supercritical fluids, and supercritical fluid mixtures. We have made measurements on fluid H2O (water), CH2O (formaldehyde), and CH3OH (methanol). Sound speeds measured through ISLS have allowed us to refine existing potential models used in the EXP6 detonation product library [Fried, L. E., and Howard, W. M., J. Chem. Phys. 109 (17): 7338-7348 (1998).]. The refined models allow us to more accurately assess the chemical composition at the Chapman-Jouget (C-J) state of common explosives. We predict that water and formaldehyde are present in appreciable quantities at the C-J state of HMX, RDX, and NM. Methanol is predicted to be present only in trace quantities at the C-J state. In the case of methanol, chemical decomposition and phase separation was observed at high temperatures. We are developing micro-FTIR and Raman techniques to determine the chemical composition of the phase separated detonation products.

  7. Experimental EOS and Chemical Studies of High-Pressure Detonation Products and Product Mixtures

    SciTech Connect

    Zaug, J M; Fried, L E; Crowhurst, J C; Hansen, D W; Howard, W M; Lee, G S; Pagoria, P F; Abramson, E H

    2002-08-06

    We present equation of state results from impulsively stimulated light scattering (ISLS) experiments conducted in diamond anvil cells on pure supercritical fluids, and supercritical fluid mixtures. We have made measurements on fluid H2O (water), CH2O (formaldehyde), and CH3OH (methanol). Sound speeds measured through ISLS have allowed us to refine existing potential models used in the Em6 detonation product library [Fried, L. E., and Howard, W. M., J. Chem. Phys. 109 (17): 7338-7348 (1998).]. The refined models allow us to more accurately assess the chemical composition at the Chapman-Jouget (C-J) state of common explosives. We predict that water and formaldehyde are present in appreciable quantities at the C-J state of HMX, RDX, and NM. Methanol is predicted to be present only in trace quantities at the C-J state. In the case of methanol, chemical decomposition and phase separation was observed at high temperatures. We are developing micro-FTIR and Raman techniques to determine the chemical composition of the phase separated detonation products.

  8. 2D NMR Barcoding and Differential Analysis of Complex Mixtures for Chemical Identification: The Actaea Triterpenes

    PubMed Central

    2015-01-01

    The interpretation of NMR spectroscopic information for structure elucidation involves decoding of complex resonance patterns that contain valuable molecular information (δ and J), which is not readily accessible otherwise. We introduce a new concept of 2D-NMR barcoding that uses clusters of fingerprint signals and their spatial relationships in the δ−δ coordinate space to facilitate the chemical identification of complex mixtures. Similar to widely used general barcoding technology, the structural information of individual compounds is encoded as a specifics pattern of their C,H correlation signals. Software-based recognition of these patterns enables the structural identification of the compounds and their discrimination in mixtures. Using the triterpenes from various Actaea (syn. Cimicifuga) species as a test case, heteronuclear multiple-bond correlation (HMBC) barcodes were generated on the basis of their structural subtypes from a statistical investigation of their δH and δC data in the literature. These reference barcodes allowed in silico identification of known triterpenes in enriched fractions obtained from an extract of A. racemosa (black cohosh). After dereplication, a differential analysis of heteronuclear single-quantum correlation (HSQC) spectra even allowed for the discovery of a new triterpene. The 2D barcoding concept has potential application in a natural product discovery project, allowing for the rapid dereplication of known compounds and as a tool in the search for structural novelty within compound classes with established barcodes. PMID:24673652

  9. Chemical kinetic analysis of detonability-enhancing strategies for ethylene-oxidizer mixtures

    NASA Astrophysics Data System (ADS)

    St. George, Andrew; Driscoll, R.; Anand, V.; Gutmark, E.

    2016-11-01

    Four detailed chemical kinetic mechanisms are used in conjunction with an empirical detonation cell width model to numerically assess strategies to increase the detonation sensitivity of ethylene-oxidizer mixtures. Using this method, reasonable agreement is achieved with computed cell width and the available experimental data. Elevated initial pressures significantly reduce cell width for a wide range of equivalence ratios, yielding 80% reduction at stoichiometric conditions for a tenfold increase in pressure. Elevated initial temperatures have almost no effect on the cell width at stoichiometric conditions, but yield 80% reduction at lean conditions when the initial temperature is doubled. Reduced nitrogen dilution within the oxidizer dramatically reduces the cell width for the entire computed range of equivalence ratios. Introducing hydrogen as a fuel additive yields mild improvement to detonation sensitivity at stoichiometric conditions, but requires relatively high H2 concentrations and is ineffective when coupled with elevated initial pressures. Introduction of supplemental oxygen and increasing the initial reactant pressure appears to be the most effective approach to enhance detonability for ethylene-oxidizer mixtures.

  10. Quasi-chemical approach for adsorption of mixtures with non-additive lateral interactions

    NASA Astrophysics Data System (ADS)

    Pinto, O. A.; Pasinetti, P. M.; Ramirez-Pastor, A. J.

    2017-01-01

    The statistical thermodynamics of binary mixtures with non-additive lateral interactions was developed on a generalization in the spirit of the lattice-gas model and the classical quasi-chemical approximation (QCA). The traditional assumption of a strictly pairwise additive nearest-neighbors interaction is replaced by a more general one, namely that the bond linking a certain atom with any of its neighbors depends considerably on how many of them are actually present (or absent) on the sites in the first coordination shell of the atom. The total and partial adsorption isotherms are given for both attractive and repulsive lateral interactions between the adsorbed species. Interesting behaviors are observed and discussed in terms of the low-temperature phases formed in the system. Comparisons with Monte Carlo simulations are performed in order to test the validity of the theoretical model.

  11. Quantum degenerate Bose-Fermi mixture of chemically different atomic species with widely tunable interactions

    NASA Astrophysics Data System (ADS)

    Park, Jee Woo; Wu, Cheng-Hsun; Santiago, Ibon; Tiecke, Tobias; Will, Sebastian; Ahmadi, Peyman; Zwierlein, Martin

    2012-06-01

    We have created a quantum degenerate Bose-Fermi mixture of ^23Na and ^40K with widely tunable interactions via broad interspecies Feshbach resonances. Over thirty Feshbach resonances between ^23Na and ^40K were identified, including p-wave multiplet resonances. The large and negative triplet background scattering length between ^23Na and ^40K causes a sharp enhancement of the fermion density in the presence of a Bose condensate. As explained via the asymptotic bound-state model (ABM), this strong background scattering leads to wide Feshbach resonances observed at low magnetic fields. Our work opens up the prospect to create chemically stable, fermionic ground state molecules of ^23Na--^40K where strong, long-range dipolar interactions would set the dominant energy scale.

  12. Quantum degenerate Bose-Fermi mixture of chemically different atomic species with widely tunable interactions

    NASA Astrophysics Data System (ADS)

    Park, Jee Woo; Wu, Cheng-Hsun; Santiago, Ibon; Tiecke, Tobias; Ahmadi, Peyman; Zwierlein, Martin

    2012-02-01

    We have created a quantum degenerate Bose-Fermi mixture of 23Na and 40K with widely tunable interactions via broad interspecies Feshbach resonances. Twenty Feshbach resonances between 23Na and 40K were identified. The large and negative triplet background scattering length between 23Na and 40K causes a sharp enhancement of the fermion density in the presence of a Bose condensate. As explained via the asymptotic bound-state model (ABM), this strong background scattering leads to a series of wide Feshbach resonances observed at low magnetic fields. Our work opens up the prospect to create chemically stable, fermionic ground state molecules of 23Na-40K where strong, long-range dipolar interactions will set the dominant energy scale.

  13. Are Fish Consumption Advisories for the Great Lakes Adequately Protective against Chemical Mixtures?

    PubMed Central

    Gandhi, Nilima; Drouillard, Ken G.; Arhonditsis, George B.; Gewurtz, Sarah B.; Bhavsar, Satyendra P.

    2016-01-01

    Background: The North American Great Lakes are home to > 140 types of fish and are famous for recreational and commercial fishing. However, the presence of toxic substances has resulted in the issuance of fish consumption advisories that are typically based on the most restrictive contaminant. Objectives: We investigated whether these advisories, which typically neglect the existence of a mixture of chemicals and their possible additive adverse effects, are adequately protective of the health of humans consuming fish from the Canadian waters of the Great Lakes. Methods: Using recent fish contaminant monitoring data collected by the government of Ontario, Canada, we simulated advisories using most-restrictive-contaminant (one-chem) and multi-contaminant additive effect (multi-chem) approaches. The advisories from the two simulations were compared to determine if there is any deficiency in the currently issued advisories. Results: Approximately half of the advisories currently issued are potentially not adequately protective. Of the four Great Lakes studied, the highest percentage of advisories affected are in Lake Ontario if an additive effect is considered. Many fish that are popular for consumption, such as walleye, salmon, bass and trout, would have noticeably more stringent advisories. Conclusions: Improvements in the advisories may be needed to ensure that the health of humans consuming fish from the Great Lakes is protected. In this region, total polychlorinated biphenyls (PCBs) and mercury are the major contaminants causing restrictions on consuming fish, whereas dioxins/furans, toxaphene, and mirex/photomirex are of minor concern. Regular monitoring of most organochlorine pesticides and metals in fish can be discontinued. Citation: Gandhi N, Drouillard KG, Arhonditsis GB, Gewurtz SB, Bhavsar SP. 2017. Are fish consumption advisories for the Great Lakes adequately protective against chemical mixtures? Environ Health Perspect 125:586–593;

  14. Using Mode of Action to Assess Health Risks from Mixtures of Chemical/Physical Agents

    SciTech Connect

    Bull, Richard J.; Lei, Xingye C.; Sasser, Lyle B.

    2003-01-20

    Interactions between tumor promoters with differing mechanisms of action were examined in male B6C3F1 mice treated with mixtures of dichloroacetate (DCA), trichloroacetate (TCA), and tetrachloride (CT), each of which acts by a different mode of action. Mice were initiated by vinyl carbamate (VC), and then promoted by DCA, TCA, CT, or the pair-wised combinations of the three compounds. The effect of each treatment or treatment combination on tumor number/animal and tumor size was individually assessed at 18, 24, 30 or 36 weeks of treatment. Dose-related increases in tumor size were observed with 20 & 50 mg/kg CT, but each produced equal number of tumors at 36 weeks with the main distinction being a decrease in tumor latency at the higher dose. Overall TCA treatment produced dose-related increases in tumor number at 36 weeks of treatment. Thus, the lower doses of CT and TCA treatments apparently affected tumor size rather than number. Results with DCA were not as clear as a true maximum tumor number was not clearly observed within the experimental period. Treatment of mice receiving a high dose of TCA (2 g/L of drinking water) combined with varying doses of DCA (0.1, 0.5 and 2 g/L) produced increased numbers of tumors at 24 weeks and 36 weeks. However, at 36 weeks of treatment DCA produced a dose-related decrease in the size of tumors promoted by TCA. The low dose of TCA (0.1 g/L) decreased the number of tumors produced by a high dose of DCA, however, higher doses of TCA produced the same number as observed with DCA alone. Since these two chemicals produce lesions with differing phenotypes, the combination would have been expected to be additive with respect to number, but this was obviously not the case. These data suggest that the induction of liver cancer from mixtures of solvents may have predictable outcomes. The major conclusion is that these interactions are generally no more than additive. It was most interesting to note that additivity was only observed when

  15. General multi-group macroscopic modeling for thermo-chemical non-equilibrium gas mixtures

    SciTech Connect

    Liu, Yen Vinokur, Marcel; Panesi, Marco; Sahai, Amal

    2015-04-07

    This paper opens a new door to macroscopic modeling for thermal and chemical non-equilibrium. In a game-changing approach, we discard conventional theories and practices stemming from the separation of internal energy modes and the Landau-Teller relaxation equation. Instead, we solve the fundamental microscopic equations in their moment forms but seek only optimum representations for the microscopic state distribution function that provides converged and time accurate solutions for certain macroscopic quantities at all times. The modeling makes no ad hoc assumptions or simplifications at the microscopic level and includes all possible collisional and radiative processes; it therefore retains all non-equilibrium fluid physics. We formulate the thermal and chemical non-equilibrium macroscopic equations and rate coefficients in a coupled and unified fashion for gases undergoing completely general transitions. All collisional partners can have internal structures and can change their internal energy states after transitions. The model is based on the reconstruction of the state distribution function. The internal energy space is subdivided into multiple groups in order to better describe non-equilibrium state distributions. The logarithm of the distribution function in each group is expressed as a power series in internal energy based on the maximum entropy principle. The method of weighted residuals is applied to the microscopic equations to obtain macroscopic moment equations and rate coefficients succinctly to any order. The model’s accuracy depends only on the assumed expression of the state distribution function and the number of groups used and can be self-checked for accuracy and convergence. We show that the macroscopic internal energy transfer, similar to mass and momentum transfers, occurs through nonlinear collisional processes and is not a simple relaxation process described by, e.g., the Landau-Teller equation. Unlike the classical vibrational energy

  16. General multi-group macroscopic modeling for thermo-chemical non-equilibrium gas mixtures

    NASA Astrophysics Data System (ADS)

    Liu, Yen; Panesi, Marco; Sahai, Amal; Vinokur, Marcel

    2015-04-01

    This paper opens a new door to macroscopic modeling for thermal and chemical non-equilibrium. In a game-changing approach, we discard conventional theories and practices stemming from the separation of internal energy modes and the Landau-Teller relaxation equation. Instead, we solve the fundamental microscopic equations in their moment forms but seek only optimum representations for the microscopic state distribution function that provides converged and time accurate solutions for certain macroscopic quantities at all times. The modeling makes no ad hoc assumptions or simplifications at the microscopic level and includes all possible collisional and radiative processes; it therefore retains all non-equilibrium fluid physics. We formulate the thermal and chemical non-equilibrium macroscopic equations and rate coefficients in a coupled and unified fashion for gases undergoing completely general transitions. All collisional partners can have internal structures and can change their internal energy states after transitions. The model is based on the reconstruction of the state distribution function. The internal energy space is subdivided into multiple groups in order to better describe non-equilibrium state distributions. The logarithm of the distribution function in each group is expressed as a power series in internal energy based on the maximum entropy principle. The method of weighted residuals is applied to the microscopic equations to obtain macroscopic moment equations and rate coefficients succinctly to any order. The model's accuracy depends only on the assumed expression of the state distribution function and the number of groups used and can be self-checked for accuracy and convergence. We show that the macroscopic internal energy transfer, similar to mass and momentum transfers, occurs through nonlinear collisional processes and is not a simple relaxation process described by, e.g., the Landau-Teller equation. Unlike the classical vibrational energy

  17. General multi-group macroscopic modeling for thermo-chemical non-equilibrium gas mixtures.

    PubMed

    Liu, Yen; Panesi, Marco; Sahai, Amal; Vinokur, Marcel

    2015-04-07

    This paper opens a new door to macroscopic modeling for thermal and chemical non-equilibrium. In a game-changing approach, we discard conventional theories and practices stemming from the separation of internal energy modes and the Landau-Teller relaxation equation. Instead, we solve the fundamental microscopic equations in their moment forms but seek only optimum representations for the microscopic state distribution function that provides converged and time accurate solutions for certain macroscopic quantities at all times. The modeling makes no ad hoc assumptions or simplifications at the microscopic level and includes all possible collisional and radiative processes; it therefore retains all non-equilibrium fluid physics. We formulate the thermal and chemical non-equilibrium macroscopic equations and rate coefficients in a coupled and unified fashion for gases undergoing completely general transitions. All collisional partners can have internal structures and can change their internal energy states after transitions. The model is based on the reconstruction of the state distribution function. The internal energy space is subdivided into multiple groups in order to better describe non-equilibrium state distributions. The logarithm of the distribution function in each group is expressed as a power series in internal energy based on the maximum entropy principle. The method of weighted residuals is applied to the microscopic equations to obtain macroscopic moment equations and rate coefficients succinctly to any order. The model's accuracy depends only on the assumed expression of the state distribution function and the number of groups used and can be self-checked for accuracy and convergence. We show that the macroscopic internal energy transfer, similar to mass and momentum transfers, occurs through nonlinear collisional processes and is not a simple relaxation process described by, e.g., the Landau-Teller equation. Unlike the classical vibrational energy

  18. Concepts of risk assesment of complex chemical mixtures in laser pyrolysis fumes

    NASA Astrophysics Data System (ADS)

    Weber, Lothar W.; Meier, Thomas H.

    1996-01-01

    Laser-tissue interaction may generate by energy absorption a complex mixture of gaseous, volatile, semi-volatile and particular substances. At the time about 150 different components are known from IR-laser interaction with different organ tissues like liver, fat, muscle and skin. The laser-tissue interaction process thereby is dominated by heating processes, which is confirmed by the similarity of formed chemical products in comparison with conventional cooking processes for food preparation. With the identified chemical substances and relative amounts in backmind a walk along the think path of risk assessment with special reference to pyrolysis products is given. The main way of intake of pyrolysis products is the inhalative one, which results from the fine aerosols formed and the high spreading energy out of the irradiated source. The liberated amounts of irritative chemicals as (unsaturated) aldehydes, heterocycles of bad odor and possibly cancerogenic acting substances relates to some (mu) g/g of laser vaporized tissue. With regard to this exposure level in a hypothetic one cubic meter volume the occupational limit settings are far away. Even indoor air exposure levels are in nearly all cases underwent, for the content of bad smelling substances forces an effective ventilation. Up to now no laser typical chemical substance could be identified, which was not elsewhere known by frying or baking processes of meat, food or familiar. Starting with the GRAS concept of 1957 the process of risk assessment by modified food products and new ingredients is still improofing. The same process of risk assessment is governing the laser pyrolysis products of mammalian tissues. By use of sufficient suction around the laser tissue source the odor problems as well as the toxicological problems could be solved.

  19. Atomic charges of individual reactive chemicals in binary mixtures determine their joint effects: an example of cyanogenic toxicants and aldehydes.

    PubMed

    Tian, Dayong; Lin, Zhifen; Yin, Daqiang; Zhang, Yalei; Kong, Deyang

    2012-02-01

    Environmental contaminants are usually encountered as mixtures, and many of these mixtures yield synergistic or antagonistic effects attributable to an intracellular chemical reaction that pose a potential threat on ecological systems. However, how atomic charges of individual chemicals determine their intracellular chemical reactions, and then determine the joint effects for mixtures containing reactive toxicants, is not well understood. To address this issue, the joint effects between cyanogenic toxicants and aldehydes on Photobacterium phosphoreum were observed in the present study. Their toxicological joint effects differed from one another. This difference is inherently related to the two atomic charges of the individual chemicals: the oxygen charge of -CHO (O(aldehyde toxicant)) in aldehyde toxicants and the carbon-atom charge of a carbon chain in the cyanogenic toxicant (C(cyanogenic toxicant)). Based on these two atomic charges, the following QSAR (quantitative structure-activity relationship) model was proposed: When (O(aldehyde toxicant) -C(cyanogenic toxicant) )> -0.125, the joint effect of equitoxic binary mixtures at median inhibition (TU, the sum of toxic units) can be calculated as TU = 1.00 ± 0.20; when (O(aldehyde toxicant) -C(cyanogenic toxicant) ) ≤ -0.125, the joint effect can be calculated using TU = - 27.6 x O (aldehyde toxicant) - 5.22 x C (cyanogenic toxicant) - 6.97 (n = 40, r = 0.887, SE = 0.195, F = 140, p < 0.001, q(2) (Loo) = 0.748; SE is the standard error of the regression, F is the F test statistic). The result provides insight into the relationship between the atomic charges and the joint effects for mixtures containing cyanogenic toxicants and aldehydes. This demonstrates that the essence of the joint effects resulting from intracellular chemical reactions depends on the atomic charges of individual chemicals. The present study provides a possible approach for the development of a QSAR model for mixtures containing reactive

  20. 75 FR 767 - Extension of Tolerances for Emergency Exemptions (Multiple Chemicals)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-06

    ..., and Rodenticide Act (FIFRA) authorizing use of these pesticides. Section 408(l)(6) of the Federal Food... requirement for a tolerance for pesticide chemical residues in food that will result from the use of a... tolerance for pesticide chemical residues in food that will result from the use of a pesticide under an...

  1. Statistical issues in risk assessment of reproductive outcomes with chemical mixtures

    SciTech Connect

    Hertzber, V.S.; Lemasters, G.K.; Hansen, K. ); Zenick, H.M. )

    1991-01-01

    Establishing the relationship between a given chemical exposure and human reproductive health risk is complicated by exposures or other concomitant factors that may vary from pregnancy to pregnancy. Moreover, when exposures are to complex mixtures of chemicals, varying with time in number of components, doses of individual components, and constancy of exposure, the picture becomes even more complicated. A pilot study of risk of adverse reproductive outcomes among male wastewater treatment workers and their wives is described here. The wives of 231 workers were interviewed to evaluate retrospectively the outcomes of spontaneous early fetal loss and infertility. In addition, 87 workers participated in a cross-sectional evaluation of sperm/semen parameters. Due to the ever-changing nature of the exposure and the lack of quantification of specific exposures, six dichotomous variables were used for each specific job description to give a surrogate measure of exposure. Hence, no quantitative exposure-response relationships could be modeled. These six variables were independently assigned by two environmental hygienists, and their interrater reliability was assessed. Results are presented and further innovations in statistical methodology are proposed for further applications.

  2. 30 CFR 47.92 - Exemptions from labeling.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Exemptions from labeling. 47.92 Section 47.92 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR EDUCATION AND TRAINING HAZARD COMMUNICATION (HazCom) Exemptions § 47.92 Exemptions from labeling. A hazardous chemical is exempt from subpart...

  3. A simple procedure for estimating pseudo risk ratios from exposure to non-carcinogenic chemical mixtures.

    PubMed

    Scinicariello, Franco; Portier, Christopher

    2016-03-01

    Non-cancer risk assessment traditionally assumes a threshold of effect, below which there is a negligible risk of an adverse effect. The Agency for Toxic Substances and Disease Registry derives health-based guidance values known as Minimal Risk Levels (MRLs) as estimates of the toxicity threshold for non-carcinogens. Although the definition of an MRL, as well as EPA reference dose values (RfD and RfC), is a level that corresponds to "negligible risk," they represent daily exposure doses or concentrations, not risks. We present a new approach to calculate the risk at exposure to specific doses for chemical mixtures, the assumption in this approach is to assign de minimis risk at the MRL. The assigned risk enables the estimation of parameters in an exponential model, providing a complete dose-response curve for each compound from the chosen point of departure to zero. We estimated parameters for 27 chemicals. The value of k, which determines the shape of the dose-response curve, was moderately insensitive to the choice of the risk at the MRL. The approach presented here allows for the calculation of a risk from a single substance or the combined risk from multiple chemical exposures in a community. The methodology is applicable from point of departure data derived from quantal data, such as data from benchmark dose analyses or from data that can be transformed into probabilities, such as lowest-observed-adverse-effect level. The individual risks are used to calculate risk ratios that can facilitate comparison and cost-benefit analyses of environmental contamination control strategies.

  4. Biological and chemical reactivity and phosphorus forms of buffalo manure compost, vermicompost and their mixture with biochar.

    PubMed

    Ngo, Phuong-Thi; Rumpel, Cornelia; Ngo, Quoc-Anh; Alexis, Marie; Velásquez Vargas, Gabriela; Mora Gil, Maria de la Luz; Dang, Dinh-Kim; Jouquet, Pascal

    2013-11-01

    This study characterized the carbon and phosphorus composition of buffalo manure, its compost and vermicompost and investigated if presence of bamboo biochar has an effect on their chemical and biological reactivity. The four substrates were characterized for chemical and biochemical composition and P forms. The biological stability of the four substrates and their mixtures were determined during an incubation experiment. Their chemical reactivity was analyzed after acid dichromate oxidation. Biological reactivity of these substrates was related to their soluble organic matter content, which decreased in the order buffalo manure>compost>vermicompost. Phosphorus was labile in all organic substrates and composting transformed organic P into plant available P. The presence of biochar led to a protection of organic matter against chemical oxidation and changed their susceptibility to biological degradation, suggesting that biochar could increase the carbon sequestration potential of compost, vermicompost and manure, when applied in mixture.

  5. Analysis of Environmental Chemical Mixtures and Non-Hodgkin Lymphoma Risk in the NCI-SEER NHL Study

    PubMed Central

    Czarnota, Jenna; Gennings, Chris; Colt, Joanne S.; De Roos, Anneclaire J.; Cerhan, James R.; Severson, Richard K.; Hartge, Patricia; Ward, Mary H.

    2015-01-01

    Background There are several suspected environmental risk factors for non-Hodgkin lymphoma (NHL). The associations between NHL and environmental chemical exposures have typically been evaluated for individual chemicals (i.e., one-by-one). Objectives We determined the association between a mixture of 27 correlated chemicals measured in house dust and NHL risk. Methods We conducted a population-based case–control study of NHL in four National Cancer Institute–Surveillance, Epidemiology, and End Results centers—Detroit, Michigan; Iowa; Los Angeles County, California; and Seattle, Washington—from 1998 to 2000. We used weighted quantile sum (WQS) regression to model the association of a mixture of chemicals and risk of NHL. The WQS index was a sum of weighted quartiles for 5 polychlorinated biphenyls (PCBs), 7 polycyclic aromatic hydrocarbons (PAHs), and 15 pesticides. We estimated chemical mixture weights and effects for study sites combined and for each site individually, and also for histologic subtypes of NHL. Results The WQS index was statistically significantly associated with NHL overall [odds ratio (OR) = 1.30; 95% CI: 1.08, 1.56; p = 0.006; for one quartile increase] and in the study sites of Detroit (OR = 1.71; 95% CI: 1.02, 2.92; p = 0.045), Los Angeles (OR = 1.44; 95% CI: 1.00, 2.08; p = 0.049), and Iowa (OR = 1.76; 95% CI: 1.23, 2.53; p = 0.002). The index was marginally statistically significant in Seattle (OR = 1.39; 95% CI: 0.97, 1.99; p = 0.071). The most highly weighted chemicals for predicting risk overall were PCB congener 180 and propoxur. Highly weighted chemicals varied by study site; PCBs were more highly weighted in Detroit, and pesticides were more highly weighted in Iowa. Conclusions An index of chemical mixtures was significantly associated with NHL. Our results show the importance of evaluating chemical mixtures when studying cancer risk. Citation Czarnota J, Gennings C, Colt JS, De Roos AJ, Cerhan JR, Severson RK, Hartge P, Ward MH

  6. 40 CFR 180.1057 - Phytophthora palmivora; exemption from requirement of tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions.... Phytophthora palmivora is exempted from the requirement of a tolerance in or on the raw agricultural...

  7. 40 CFR 180.1057 - Phytophthora palmivora; exemption from requirement of tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions.... Phytophthora palmivora is exempted from the requirement of a tolerance in or on the raw agricultural...

  8. 40 CFR 180.1057 - Phytophthora palmivora; exemption from requirement of tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions.... Phytophthora palmivora is exempted from the requirement of a tolerance in or on the raw agricultural...

  9. 40 CFR 180.1057 - Phytophthora palmivora; exemption from requirement of tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions.... Phytophthora palmivora is exempted from the requirement of a tolerance in or on the raw agricultural...

  10. A COMPARISON OF THE LETHAL AND SUBLETHAL TOXICITY OF ORGANIC CHEMICAL MIXTURES TO THE FATHEAD MINNOW (PIMEPHALES PROMELAS)

    EPA Science Inventory

    The joint toxic effects of known binary and multiple organic chemical mixtures to the fathead minnow (Pimephales promelas) were defined at both the 96-h 50% lethal effect concentration (LC50) and sublethal (32-d growth) response levels for toxicants with a narcosis I, narcosis II...

  11. COMPARISON OF SORPTION ENERGTICS FOR HYDROPHOBIC ORGANIC CHEMICALS BY SYNTHETIC AND NATURAL SORBENTS FROM METHANOL/WATER SOLVENT MIXTURES

    EPA Science Inventory

    Reversed-phase liquid chromatography (RPLC) was used to investigate the thermodynamics and mechanisms of hydrophobic organic chemical (HOC) retention from methanol/water solvent mixtures. The enthalpy-entropy compensation model was used to infer that the hydro- phobic sorptive me...

  12. A COMPARISON OF THE LETHAL AND SUBLETHAL TOXICITY OF ORGANIC CHEMICAL MIXTURES TO THE FATHEAD MINNOW (PIMEPHALES PROMELAS)

    EPA Science Inventory

    The joint toxic effects of known binary and multiple organic chemical mixtures to the fathead minnow (Pimephales promelas) were defined at both the 96-h 50% lethal effect concentration (LC50) and sublethal (32-d growth) response levels for toxicants with a narcosis I, narcosis II...

  13. COMPARISON OF SORPTION ENERGTICS FOR HYDROPHOBIC ORGANIC CHEMICALS BY SYNTHETIC AND NATURAL SORBENTS FROM METHANOL/WATER SOLVENT MIXTURES

    EPA Science Inventory

    Reversed-phase liquid chromatography (RPLC) was used to investigate the thermodynamics and mechanisms of hydrophobic organic chemical (HOC) retention from methanol/water solvent mixtures. The enthalpy-entropy compensation model was used to infer that the hydro- phobic sorptive me...

  14. Modeling of chemical reactions in the mixture of Al-Ni powders under shock-wave compression

    SciTech Connect

    Horie, Y.; Kipp, M.E.

    1987-07-01

    Based upon microstructural observations of post-shock samples, a mathematical model was developed for chemical changes in the mixture of elemental Al and Ni powders from the passage of high-pressure shock-wave. The model was solved and illustrated using the one-dimensional Sandia code WONDY-IV.

  15. Subtleties of human exposure and response to chemical mixtures from spills.

    PubMed

    Phetxumphou, Katherine; Dietrich, Andrea M; Shanaiah, Narasimhamurthy; Smiley, Elizabeth; Gallagher, Daniel L

    2016-07-01

    Worldwide, chemical spills degrade drinking water quality and threaten human health through ingestion and inhalation. Spills are often mixtures of chemicals; thus, understanding the interaction of chemical and biological properties of the major and minor components is critical to assessing human exposure. The crude (4-methylcyclohexyl)methanol (MCHM) spill provides an opportunity to assess such subtleties. This research determined the relative amounts, volatilization, and biological odor properties of minor components cis- and trans-methyl-4-methylcyclohexanecarboxylate (MMCHC) isomers and major components cis- and trans-4-MCHM, then compared properties and human exposure differences among them. (1)H nuclear magnetic resonance and chromatography revealed that the minor MMCHC isomers were about 1% of the major MCHM isomers. At typical showering temperature of 40 °C, Henry's law constants were 1.50 × 10(-2) and 2.23 × 10(-2) for cis- and trans-MMCHC, respectively, which is 20-50 fold higher than for 4-MCHM isomers. The odor thresholds were 1.83 and 0.02 ppb-v air for cis- and trans-MMCHC, which were both described as predominantly sweet. These data are compared to the higher 120 ppb-v air and 0.06 ppb-v odor thresholds for cis- and trans-4-MCHM, for which the trans-isomer had a dominant licorice descriptor. Application of a shower model demonstrated that while MMCHC isomers are only about 1% of the MCHM isomers, during showering, the MMCHC isomers are 13.8% by volume (16.3% by mass) because of their higher volatility. Trans-4-MCHM contributed about 82% of the odor because of higher volatility and lower odor threshold, trans-MMCHC, which represents 0.3% of the mass, contributed 18% of the odor. This study, with its unique human sensory component to assess exposure, reaffirmed that hazard assessment must not be based solely on relative concentration, but also consider the chemical fate, transport, and biological properties to determine the actual levels of

  16. 40 CFR 176.5 - Establishment of a time-limited tolerance or exemption.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... residues in or on raw or processed food or feed resulting from the use of a pesticide chemical, if EPA authorizes an emergency exemption or a crisis exemption. EPA will consider establishing such a tolerance only... exemption, has stated its intention to issue a crisis exemption, or has issued a crisis exemption for a use...

  17. 40 CFR 176.5 - Establishment of a time-limited tolerance or exemption.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... residues in or on raw or processed food or feed resulting from the use of a pesticide chemical, if EPA authorizes an emergency exemption or a crisis exemption. EPA will consider establishing such a tolerance only... exemption, has stated its intention to issue a crisis exemption, or has issued a crisis exemption for a use...

  18. 40 CFR 176.5 - Establishment of a time-limited tolerance or exemption.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... residues in or on raw or processed food or feed resulting from the use of a pesticide chemical, if EPA authorizes an emergency exemption or a crisis exemption. EPA will consider establishing such a tolerance only... exemption, has stated its intention to issue a crisis exemption, or has issued a crisis exemption for a use...

  19. 40 CFR 176.5 - Establishment of a time-limited tolerance or exemption.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... residues in or on raw or processed food or feed resulting from the use of a pesticide chemical, if EPA authorizes an emergency exemption or a crisis exemption. EPA will consider establishing such a tolerance only... exemption, has stated its intention to issue a crisis exemption, or has issued a crisis exemption for a use...

  20. Quantum chemical study of ternary mixtures of: HNO3:H2SO4:H2O

    NASA Astrophysics Data System (ADS)

    Verdes, M. A.; Gómez, P. C.; Gálvez, O.

    2009-04-01

    Water, nitric acid and sulfuric acid are important atmospheric species as individual species and as hydrogen-bonded aggregates involved in many physical-chemical processes both superficial and bulk. The importance of heterogeneous chemical reactions taking place on ice surfaces, either solid water or solid water plus nitric or sulfuric acid, is well established now in relation to the ozone-depleting mechanisms. Also the importance of liquid droplets formed by HNO3.H2SO4.H2O as components of PSC was soon recognized [1-3]. Finally the physical properties of finely divided aqueous systems is an interesting and active field of research in which theoretical information on the microphysical domain systems may help to understand and rationalize the wealth of experimental information. This can also be the initial step in the study of more complex mixtures with higher amounts of water or variable proportions of their constituents. This kind of calculations have been successfully performed in the past[4]. We present here our results on the structure and spectroscopic and thermodynamic properties of the energy-lowest lying structures among those thermodynamically stable formed by linking the acids plus water. The calculations have been carried out by means of DFT methods (in particular the successful B3LYP) using different basis sets that contain appropriate sets of polarization and diffuse functions up to quadruple-Z quality (Dunninǵs aug-cc-pVQZ). Careful assessment of the dependability of the methodology used has been carried out. This work has been supported by the Spanish Ministry of Education, Projects FIS2007-61686 and CTQ2008-02578/BQU References: [1] Carslaw, K. S. et al.: Geophys. Res. Lett. 21, 2479-2482, 1994 [2] Drdla, K. Et al. :Geophys. Res. Lett. 21, 2473-2478, 1994 [3] Tabazadeh, A. et al.: Geophys. Res. Lett 21, 1619-1622, 1994 [4] Escribano, R et al.: J. J. Chem. Phys A 2003, 107, 652.

  1. Probabilistic Health Risk Assessment of Chemical Mixtures: Importance of Travel Times and Connectivity

    NASA Astrophysics Data System (ADS)

    Henri, Christopher V.; Fernàndez-Garcia, Daniel; de Barros, Felipe P. J.

    2014-05-01

    Subsurface contamination cases giving rise to groundwater pollutions are extensively found in all industrialized countries. Under this pressure, risk assessment methods play an important role in population protection by (1) quantifying the potential impact on human health of an aquifer contamination and (2) helping and driving decisions of groundwater-resource managers. Many reactive components such as chlorinated solvents or nitrates potentially experience attenuation processes under common geochemical conditions. This represents an attractive and extensively used remediation solution but leads often to the production of by-products before to reach a harmless chemical form. This renders mixtures of contaminants a common issue for groundwater resources managers. In this case, the threat posed by these contaminants to human health at a given sensitive location greatly depends on the competition between reactive and advective-dispersive characteristic times. However, hydraulic properties of the aquifer are known to be spatially variable, which can lead to the formation of preferential flow channels and fast contamination pathways. Therefore, the uncertainty on the spatial distribution of the aquifer properties controlling the plume travel time may then play a particular role in the human health risk assessment of chemical mixtures. We investigate here the risk related to a multispecies system in response to different degrees of heterogeneity of the hydraulic conductivity (K or Y =ln(K)). This work focuses on a Perchloroethylene (PCE) contamination problem followed by the sequential first-order production/biodegradation of its daughter species Trichloroethylene (TCE), Dichloroethylene (DCE) and Vinyl Chlorine (VC). For this specific case, VC is known to be a highly toxic contaminant. By performing numerical experiments, we evaluate transport through three-dimensional mildly (σY 2=1.0) and highly (σY 2=4.0) heterogeneous aquifers. Uncertainty on the hydraulic

  2. Physico-chemical properties of chars obtained in the co-pyrolysis of waste mixtures.

    PubMed

    Bernardo, M; Lapa, N; Gonçalves, M; Mendes, B; Pinto, F; Fonseca, I; Lopes, H

    2012-06-15

    The present work aims to perform a multistep upgrading of chars obtained in the co-pyrolysis of PE, PP and PS plastic wastes, pine biomass and used tires. The quality of the upgraded chars was evaluated by measuring some of their physico-chemical properties in order to assess their valorisation as adsorbents' precursors. The crude chars were submitted to a sequential solvent extraction with organic solvents of increasing polarity (hexane, mixture 1:1 v/v hexane:acetone and acetone) followed by an acidic demineralization procedure with 1M HCl solution. The results obtained showed that the upgrading treatment allow the recovery of 63-81% of the pyrolysis oils trapped in the crude chars and a reduction in the char's ash content in the range of 64-86%. The textural and adsorption properties of the upgraded chars were evaluated and the results indicate that the chars are mainly mesoporous and macroporous materials, with adsorption capacities in the range of 3.59-22.2 mg/g for the methylene blue dye. The upgrading treatment allowed to obtain carbonaceous materials with quality to be reused as adsorbents or as precursors for activated carbon.

  3. Chemopreventive effect of a mixture of Chinese Herbs (antitumor B) on chemically induced oral carcinogenesis.

    PubMed

    Wang, Yian; Yao, Ruisheng; Gao, Song; Wen, Weidong; Du, Yinqiu; Szabo, Eva; Hu, Ming; Lubet, Ronald A; You, Ming

    2013-01-01

    In this study, we evaluated chemopreventive efficacy of Antitumor B, a Chinese herbal mixture of six plants (Sophora tonkinensis, Polygonum bistorta, Prunella vulgaris, Sonchus arvensis L., Dictamnus dasycarpus, and Dioscorea bulbifera) on the development of 4-nitroquinoline-1-oxide (4NQO) induced oral squamous cell carcinomas in A/J mice. Antitumor B, delivered through diet, inhibited 4NQO-induced oral cancer development by 59.19%. The reduction of cell proliferation appears to be associated with efficacy of Antitumor B against 4NQO-induced oral cancer in A/J mice. The expression of epidermal growth factor receptor (EGFR) and phosphorylated EGFR (Tyr1173) were down-regulated by Antitumor B. Tissue distribution of Antitumor B was determined using obacunone, matrine, and maackiain as marker chemicals. We found significant amounts of obacunone, matrine, and maackiain in the blood after 1-wk treatment. The concentrations of these three compounds did not increase further at 18  wk, suggesting that plasma concentrations had reached a steady-state level at 1  wk. There was no significant body weight loss and there was no other obvious sign of toxicity in Antitumor B-treated mice. These results suggest that Antitumor B is a promising agent for human oral cancer chemoprevention.

  4. Investigation of Shock-Induced Chemical Reactions in Mo-Si Powder Mixtures Using Instrumented Experiments with PVDF Stress Gauges

    SciTech Connect

    Vandersall, K S; Thadhani, N N

    2001-05-29

    Shock-induced chemical reactions in {approx}58% dense Mo+2Si powder mixtures were investigated using time-resolved instrumented experiments, employing PVDF-piezoelectric stress gauges placed at the front and rear surfaces of the powders to measure the input and propagated stresses, and wave speed through the powder mixture. Experiments performed on the powders at input stresses less than 4 GPa, showed characteristics of powder densification and dispersed propagated wave stress profiles with rise time > {approx}40 nanoseconds. At input stress between 4-6 GPa, the powder mixtures showed a sharp rise time (<{approx}10 ns) of propagated wave profile and an expanded state of products revealing evidence of shock-induced chemical reaction. At input stresses greater than 6 GPa, the powder mixtures showed a slower propagated-stress-wave rise time and transition to a low-compressibility (melt) state indicating lack of shock-induced reaction. The results illustrate that premature melting of Si, at input stresses less than the crush-strength of the powder mixtures, restricts mixing between reactants and inhibits ''shock-induced'' reaction initiation.

  5. Influence of chemically produced singlet delta oxygen molecules on thermal ignition of O2-H2 mixtures

    NASA Astrophysics Data System (ADS)

    Vagin, N. P.; Kochetov, I. V.; Napartovich, A. P.; Yuryshev, N. N.

    2016-02-01

    Thermal ignition of the H2-O2 mixture with O2(a 1Δ g ) addition is studied experimentally and theoretically. The singlet delta oxygen was produced in a chemical generator. In this way, the competing chemical processes involving plasma produced chemically active O atoms and ozone (O3) were excluded. A satisfactory agreement is achieved between experimentally observed and numerically predicted values of the ignition time at the initial gas temperature (900-950) K and gas pressure (9-10) Torr. The percentage of the reactive channel in the binary collisions O2(a 1Δg) H is evaluated on the level (10-20)% for the H2-O2 mixture.

  6. Genotoxic and hematological effects in children exposed to a chemical mixture in a petrochemical area in Mexico.

    PubMed

    Pelallo-Martínez, Nadia Azenet; Batres-Esquivel, Lilia; Carrizales-Yáñez, Leticia; Díaz-Barriga, Fernando Martínez

    2014-07-01

    Children living in Coatzacoalcos, Veracruz, and in nearby surrounding areas are exposed to a mixture of pollutants from different sources. Previous studies in the area have reported genotoxic and haematotoxic compounds, such as lead (Pb), benzene, toluene, and polycyclic aromatic hydrocarbons (PAHs), in environmental and biological samples. The final toxic effects of these compounds are unknown because the toxic behaviour of each compound is modified when in a complex mixture. This is the first study on the exposure and effect of chemical mixtures on children who live near a petrochemical area. The aim of this study was to evaluate genotoxicity and haematological effects in children environmentally exposed to such mixtures and to determine whether the final effect was modified by the composition of the mixture composition. Biomarkers of exposure to Pb, benzene, toluene, and PAHs were quantified in urine and blood samples of 102 children. DNA damage was evaluated using comet assay, and haematological parameters were determined. Our results show that Pb and toluene did not surpass the exposure guidelines; the exposure was similar in all three localities (Allenede, Mundo Nuevo, and López Mateos). In contrast, exposure to PAHs was observed at three levels of exposure: low, medium, and high. The most severe effects of these mixtures were strictly related to coexposure to high levels of PAHs.

  7. Statistical Approaches for Assessing Health Effects of Environmental Chemical Mixtures in Epidemiology: Lessons from an Innovative Workshop

    PubMed Central

    Taylor, Kyla W.; Joubert, Bonnie R.; Braun, Joe M.; Dilworth, Caroline; Gennings, Chris; Hauser, Russ; Heindel, Jerry J.; Rider, Cynthia V.; Webster, Thomas F.; Carlin, Danielle J.

    2016-01-01

    Summary: Quantifying the impact of exposure to environmental chemical mixtures is important for identifying risk factors for diseases and developing more targeted public health interventions. The National Institute of Environmental Health Sciences (NIEHS) held a workshop in July 2015 to address the need to develop novel statistical approaches for multi-pollutant epidemiology studies. The primary objective of the workshop was to identify and compare different statistical approaches and methods for analyzing complex chemical mixtures data in both simulated and real-world data sets. At the workshop, participants compared approaches and results and speculated as to why they may have differed. Several themes emerged: a) no one statistical approach appeared to outperform the others, b) many methods included some form of variable reduction or summation of the data before statistical analysis, c) the statistical approach should be selected based upon a specific hypothesis or scientific question, and d) related mixtures data should be shared among researchers to more comprehensively and accurately address methodological questions and statistical approaches. Future efforts should continue to design and optimize statistical approaches to address questions about chemical mixtures in epidemiological studies. PMID:27905274

  8. Prediction of acute toxicity of chemicals in mixtures: worms Tubifex tubifex and gas/liquid distribution.

    PubMed

    Tichý, M; Borek-Dohalský, V; Matousová, D; Rucki, M; Feltl, L; Roth, Z

    2002-03-01

    The aim of this contribution is to support our proposal of the procedure for predicting acute toxicity of binary mixtures by QSAR analysis techniques. The changes of a mixture composition are described by molar ratio R and visualized in the R-plot (QCAR--quantitative composition-activity relationships). The approach was inspired by Rault and Dalton's laws, their positive and negative deviations in the behavior of a mixture of real gases, by Loewe and Muischnek isoboles and by the Finney test of additivity. Acute toxicity was determined by the laboratory test with woms Tubifex tubifex. The additivity of the acute toxicity in the binary mixture benzene + nitrobenzene was confirmed and a new interaction is described: "mixed interaction" with the binary mixture aniline + ethanol. The "mixed interaction" means that depending on mixture composition, both potentiation and inhibition can occur. As the first physicochemical descriptor of the changes caused by the changing composition of binary mixtures, the gas/liquid equilibrium was studied and a composition of the gaseous phase was determined by a gas chromatographic method. The method for determination of concentrations in the gaseous phase was described. The gaseous phase composition of benzene + nitrobenzene. benzene + ethanol, benzene + aniline and ethanol + aniline mixtures was analyzed. It was found that if the concentrations of the mixture's components in the gaseous phase behave nonideally (they are not additive), the acute toxicity of the same mixture is not additive as well. Another descriptor to distinguish between potentiation and inhibition will be, however, necessary. The properties, both gaseous phase composition and the acute toxicity, of the benzene + nitrobenzene mixture are additive. In mixtures with the mixed interaction, the R-plot of the composition of the gaseous phase is complex with a large variation of results.

  9. Supersonic Flow of Chemically Reacting Gas-Particle Mixtures. Volume 2: RAMP - A Computer Code for Analysis of Chemically Reacting Gas-Particle Flows

    NASA Technical Reports Server (NTRS)

    Penny, M. M.; Smith, S. D.; Anderson, P. G.; Sulyma, P. R.; Pearson, M. L.

    1976-01-01

    A computer program written in conjunction with the numerical solution of the flow of chemically reacting gas-particle mixtures was documented. The solution to the set of governing equations was obtained by utilizing the method of characteristics. The equations cast in characteristic form were shown to be formally the same for ideal, frozen, chemical equilibrium and chemical non-equilibrium reacting gas mixtures. The characteristic directions for the gas-particle system are found to be the conventional gas Mach lines, the gas streamlines and the particle streamlines. The basic mesh construction for the flow solution is along streamlines and normals to the streamlines for axisymmetric or two-dimensional flow. The analysis gives detailed information of the supersonic flow and provides for a continuous solution of the nozzle and exhaust plume flow fields. Boundary conditions for the flow solution are either the nozzle wall or the exhaust plume boundary.

  10. Supersonic flow of chemically reacting gas-particle mixtures. Volume 1: A theoretical analysis and development of the numerical solution

    NASA Technical Reports Server (NTRS)

    Penny, M. M.; Smith, S. D.; Anderson, P. G.; Sulyma, P. R.; Pearson, M. L.

    1976-01-01

    A numerical solution for chemically reacting supersonic gas-particle flows in rocket nozzles and exhaust plumes was described. The gas-particle flow solution is fully coupled in that the effects of particle drag and heat transfer between the gas and particle phases are treated. Gas and particles exchange momentum via the drag exerted on the gas by the particles. Energy is exchanged between the phases via heat transfer (convection and/or radiation). Thermochemistry calculations (chemical equilibrium, frozen or chemical kinetics) were shown to be uncoupled from the flow solution and, as such, can be solved separately. The solution to the set of governing equations is obtained by utilizing the method of characteristics. The equations cast in characteristic form are shown to be formally the same for ideal, frozen, chemical equilibrium and chemical non-equilibrium reacting gas mixtures. The particle distribution is represented in the numerical solution by a finite distribution of particle sizes.

  11. EVALUATING QUANTITATIVE FORMULAS FOR DOSE-RESPONSE ASSESSMENT OF CHEMICAL MIXTURES

    EPA Science Inventory

    Risk assessment formulas are often distinguished from dose-response models by being rough but necessary. The evaluation of these rough formulas is described here, using the example of mixture risk assessment. Two conditions make the dose-response part of mixture risk assessment d...

  12. EVALUATING QUANTITATIVE FORMULAS FOR DOSE-RESPONSE ASSESSMENT OF CHEMICAL MIXTURES

    EPA Science Inventory

    Risk assessment formulas are often distinguished from dose-response models by being rough but necessary. The evaluation of these rough formulas is described here, using the example of mixture risk assessment. Two conditions make the dose-response part of mixture risk assessment d...

  13. Are Fish Consumption Advisories for the Great Lakes Adequately Protective against Chemical Mixtures?

    PubMed

    Gandhi, Nilima; Drouillard, Ken G; Arhonditsis, George B; Gewurtz, Sarah B; Bhavsar, Satyendra P

    2017-04-01

    The North American Great Lakes are home to > 140 types of fish and are famous for recreational and commercial fishing. However, the presence of toxic substances has resulted in the issuance of fish consumption advisories that are typically based on the most restrictive contaminant. We investigated whether these advisories, which typically neglect the existence of a mixture of chemicals and their possible additive adverse effects, are adequately protective of the health of humans consuming fish from the Canadian waters of the Great Lakes. Using recent fish contaminant monitoring data collected by the government of Ontario, Canada, we simulated advisories using most-restrictive-contaminant (one-chem) and multi-contaminant additive effect (multi-chem) approaches. The advisories from the two simulations were compared to determine if there is any deficiency in the currently issued advisories. Approximately half of the advisories currently issued are potentially not adequately protective. Of the four Great Lakes studied, the highest percentage of advisories affected are in Lake Ontario if an additive effect is considered. Many fish that are popular for consumption, such as walleye, salmon, bass and trout, would have noticeably more stringent advisories. Improvements in the advisories may be needed to ensure that the health of humans consuming fish from the Great Lakes is protected. In this region, total polychlorinated biphenyls (PCBs) and mercury are the major contaminants causing restrictions on consuming fish, whereas dioxins/furans, toxaphene, and mirex/photomirex are of minor concern. Regular monitoring of most organochlorine pesticides and metals in fish can be discontinued.

  14. Polymer surface chemistry: Surface mixtures, supported polyelectrolyte multilayers and heterogeneous chemical modification

    NASA Astrophysics Data System (ADS)

    Phuvanartnuruks, Vipavee

    This dissertation is divided into three parts that summarize three discrete projects that are related only in their overall objective of using chemistry to rationally control polymer surface structure and properties. Each part involves polymer surface modification, but the three employ very different techniques to effect surface-chemical changes. The first part (Chapter 1) involves the preparation of surfaces containing controllable mixtures of two functionalities (alcohol/ester or hydrocarbon ester/fluorocarbon ester) from alcohol-functionalized poly(chlorotrifluoroethylene) (PCTFE-OH) and the studies of their wetting behavior as a function of composition and structure. Contact angle analyses indicate that sequential and competitive esterifications yield mixed surfaces consisting of the two functional groups distributed randomly, while compositionally similar, patchy mixed surfaces can be prepared by partial hydrolysis/re-esterification under some specific conditions. Greater contact angle hysteresis was observed on the patchy surfaces. The second part (Chapter 2) describes the layer-by-layer deposition of cationic (polyallylamine hydrochloride (PAH)) and anionic (polysodium styrenesulfonate (PSS)) polyelectrolytes onto the PCTFE-OH substrate. XPS and contact angle data indicate that the assembled layers are stratified even though the individual layers are extremely thin (0.3-4.1 A). This thickness depends both on the charge density of the first layer of PAH (controlled using pH) and the ionic strength of the PSS adsorption solution. The stoichiometry of the assembly process also varies with the ionic strength of the PSS adsorption solution. The third part (Chapter 3) involves the heterogeneous (gas-solid) chemical modification of poly(trifluoroethylene) (PFsb3E). Chlorination of PFsb3E is a surface-selective reaction and the extent of chlorination can be controlled by time and light intensity. The fluorination of PFsb3E carried out using 5% Fsb2/Nsb2 yields

  15. Determinants of exposure to fragranced product chemical mixtures in a sample of twins.

    PubMed

    Gribble, Matthew O; Bandeen-Roche, Karen; Fox, Mary A

    2015-01-27

    Fragranced product chemical mixtures may be relevant for environmental health, but little is known about exposure. We analyzed results from an olfactory challenge with the synthetic musk fragrance 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopento-γ-2-benzopyran (HHCB), and a questionnaire about attitudes toward chemical safety and use of fragranced products, in a sample of 140 white and 17 black twin pairs attending a festival in Ohio. Data for each product were analyzed using robust ordered logistic regressions with random intercepts for "twin pair" and "sharing address with twin", and fixed effects for sex, age, education, and "ever being bothered by fragrances". Due to the small number of black participants, models were restricted to white participants except when examining racial differences. Overall patterns of association were summarized across product-types through random-effects meta-analysis. Principal components analysis was used to summarize clustering of product use. The dominant axis of variability in fragranced product use was "more vs. less", followed by a distinction between household cleaning products and personal care products. Overall, males used fragranced products less frequently than females (adjusted proportionate odds ratio 0.55, 95% confidence interval 0.33, 0.93). This disparity was driven by personal care products (0.42, 95% CI: 0.19, 0.96), rather than household cleaning products (0.79, 95% CI: 0.49, 1.25) and was particularly evident for body lotion (0.12, 95% CI: 0.05, 0.27). Overall usage differed by age (0.64, 95% CI: 0.43, 0.95) but only hand soap and shampoo products differed significantly. "Ever being bothered by fragrance" had no overall association (0.92, 95% CI: 0.65, 1.30) but was associated with laundry detergent use (0.46, 95% CI: 0.23, 0.93). Similarly, black vs. white differences on average were not significant (1.34, 95% CI: 0.55, 3.28) but there were apparent differences in use of shampoo (0.01, 95% CI: 0.00, 0

  16. Method and compositions for the degradation of tributyl phosphate in chemical waste mixtures

    DOEpatents

    Stoner, D.L.; Tien, A.J.

    1995-09-26

    A method and process are disclosed for the degradation of tributyl phosphate in an organic waste mixture and a biologically pure, novel bacteria culture for accomplishing the same. A newly-discovered bacteria (a strain of Acinetobacter sp. ATCC 55587) is provided which is combined in a reactor vessel with a liquid waste mixture containing tributyl phosphate and one or more organic waste compounds capable of functioning as growth substrates for the bacteria. The bacteria is thereafter allowed to incubate within the waste mixture. As a result, the tributyl phosphate and organic compounds within the waste mixture are metabolized (degraded) by the bacteria, thereby eliminating such materials which are environmentally hazardous. In addition, the bacteria is capable of degrading waste mixtures containing high quantities of tributyl phosphate (e.g. up to about 1.0% by weight tributyl phosphate). 6 figs.

  17. Method and compositions for the degradation of tributyl phosphate in chemical waste mixtures

    DOEpatents

    Stoner, Daphne L.; Tien, Albert J.

    1995-01-01

    A method and process for the degradation of tributyl phosphate in an organic waste mixture and a biologically pure, novel bacteria culture for accomplishing the same. A newly-discovered bacteria (a strain of Acinetobacter sp. ATCC 55587) is provided which is combined in a reactor vessel with a liquid waste mixture containing tributyl phosphate and one or more organic waste compounds capable of functioning as growth substrates for the bacteria. The bacteria is thereafter allowed to incubate within the waste mixture. As a result, the tributyl phosphate and organic compounds within the waste mixture are metabolized (degraded) by the bacteria, thereby eliminating such materials which are environmentally hazardous. In addition, the bacteria is capable of degrading waste mixtures containing high quantities of tributyl phosphate (e.g. up to about 1.0% by weight tributyl phosphate).

  18. Perinatal exposure to mixtures of endocrine disrupting chemicals reduces female rat follicle reserves and accelerates reproductive aging.

    PubMed

    Johansson, Hanna Katarina Lilith; Jacobsen, Pernille Rosenskjold; Hass, Ulla; Svingen, Terje; Vinggaard, Anne Marie; Isling, Louise Krag; Axelstad, Marta; Christiansen, Sofie; Boberg, Julie

    2016-06-01

    Exposure to endocrine disrupting chemicals (EDCs) during development can have negative consequences later in life. In this study we investigated the effect of perinatal exposure to mixtures of human relevant EDCs on the female reproductive system. Rat dams were exposed to a mixture of phthalates, pesticides, UV-filters, bisphenol A, butylparaben, as well as paracetamol. The compounds were tested together (Totalmix) or in subgroups with anti-androgenic (AAmix) or estrogenic (Emix) potentials. Paracetamol was tested separately. In pre-pubertal rats, a significant reduction in primordial follicle numbers was seen in AAmix and PM groups, and reduced plasma levels of prolactin was seen in AAmix. In one-year-old animals, the incidence of irregular estrous cycles was higher after Totalmix-exposure and reduced ovary weights were seen in Totalmix, AAmix, and PM groups. These findings resemble premature ovarian insufficiency in humans, and raises concern regarding potential effects of mixtures of EDCs on female reproductive function.

  19. Human exposure to chemical mixtures: Challenges for the integration of toxicology with epidemiology data in risk assessment.

    PubMed

    Hernández, Antonio F; Tsatsakis, Aristidis M

    2017-05-01

    Little is known about the potential adverse effects from longterm exposure to complex mixtures at low doses, close to health-based reference values. Traditional chemical-specific risk assessment based on animal testing may be insufficient and the lack of toxicological studies on chemical mixtures remains a major regulatory challenge. Hence, new methodologies on cumulative risk assessment are being developed but still present major limitations. Evaluation of chemical mixture effects requires an integrated and systematic approach and close collaboration across different scientific fields, particularly toxicology, epidemiology, exposure science, risk assessment and statistics for a proper integration of data from all these disciplines. Well designed and conducted epidemiological studies can take advantage of this new paradigm and can provide insight to support the correlation between humans low-dose exposures and diseases, thus avoiding the uncertainty associated with extrapolation across species. In this regard, human epidemiology studies may play a significant role in the new vision of toxicity testing. However, this type of information has not been fully considered in risk assessment, mainly due to the inherent limitations of epidemiologic studies. An integrated approach of in vivo, in vitro and in silico data, together with systematic reviews or meta-analysis of high quality epidemiological studies will improve the robustness of risk assessment of chemical mixtures and will provide a stronger basis for regulatory decisions. The ultimate goal is that experimental and mechanistic data can lend support and biological plausibility to the human epidemiological observations. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Evaluation of the COSHH Essentials model with a mixture of organic chemicals at a medium-sized paint producer.

    PubMed

    Lee, Eun Gyung; Slaven, James; Bowen, Russell B; Harper, Martin

    2011-01-01

    The Control of Substances Hazardous to Health (COSHH) Essentials model was evaluated using full-shift exposure measurements of five chemical components in a mixture [acetone, ethylbenzene, methyl ethyl ketone, toluene, and xylenes] at a medium-sized plant producing paint materials. Two tasks, batch-making and bucket-washing, were examined. Varying levels of control were already established in both tasks and the average exposures of individual chemicals were considerably lower than the regulatory and advisory 8-h standards. The average exposure fractions using the additive mixture formula were also less than unity (batch-making: 0.25, bucket-washing: 0.56) indicating the mixture of chemicals did not exceed the combined occupational exposure limit (OEL). The paper version of the COSHH Essentials model was used to calculate a predicted exposure range (PER) for each chemical according to different levels of control. The estimated PERs of the tested chemicals for both tasks did not show consistent agreement with exposure measurements when the comparison was made for each control method and this is believed to be because of the considerably different volatilities of the chemicals. Given the combination of health hazard and exposure potential components, the COSHH Essentials model recommended a control approach 'special advice' for both tasks, based on the potential reproductive hazard ascribed to toluene. This would not have been the same conclusion if some other chemical had been substituted (for example styrene, which has the same threshold limit value as toluene). Nevertheless, it was special advice, which had led to the combination of hygienic procedures in place at this plant. The probability of the combined exposure fractions exceeding unity was 0.0002 for the batch-making task indicating that the employees performing this task were most likely well protected below the OELs. Although the employees involved in the bucket-washing task had greater potential to exceed

  1. Transport of a liquid water and methanol mixture through carbon nanotubes under a chemical potential gradient

    NASA Astrophysics Data System (ADS)

    Zheng, Jie; Lennon, Erin M.; Tsao, Heng-Kwong; Sheng, Yu-Jane; Jiang, Shaoyi

    2005-06-01

    In this work, we report a dual-control-volume grand canonical molecular dynamics simulation study of the transport of a water and methanol mixture under a fixed concentration gradient through nanotubes of various diameters and surface chemistries. Methanol and water are selected as fluid molecules since water represents a strongly polar molecule while methanol is intermediate between nonpolar and strongly polar molecules. Carboxyl acid (-COOH) groups are anchored onto the inner wall of a carbon nanotube to alter the hydrophobic surface into a hydrophilic one. Results show that the transport of the mixture through hydrophilic tubes is faster than through hydrophobic nanotubes although the diffusion of the mixture is slower inside hydrophilic than hydrophobic pores due to a hydrogen network. Thus, the transport of the liquid mixture through the nanotubes is controlled by the pore entrance effect for which hydrogen bonding plays an important role.

  2. Ecological risk assessment of mixtures of radiological and chemical stressors: Methodology to implement an msPAF approach.

    PubMed

    Beaumelle, Léa; Della Vedova, Claire; Beaugelin-Seiller, Karine; Garnier-Laplace, Jacqueline; Gilbin, Rodolphe

    2017-09-22

    A main challenge in ecological risk assessment is to account for the impact of multiple stressors. Nuclear facilities can release both radiological and chemical stressors in the environment. This study is the first to apply species sensitivity distribution (SSD) combined with mixture models (concentration addition (CA) and independent action (IA)) to derive an integrated proxy of the ecological impact of combined radiological and chemical stressors: msPAF (multisubstance potentially affected fraction of species). The approach was tested on the routine liquid effluents from nuclear power plants that contain both radioactive and stable chemicals. The SSD of ionising radiation was significantly flatter than the SSD of 8 stable chemicals (namely Cr, Cu, Ni, Pb, Zn, B, chlorides and sulphates). This difference in shape had strong implications for the selection of the appropriate mixture model: contrarily to the general expectations the IA model gave more conservative (higher msPAF) results than the CA model. The msPAF approach was further used to rank the relative potential impact of radiological versus chemical stressors. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Structure-reactivity modeling using mixture-based representation of chemical reactions

    NASA Astrophysics Data System (ADS)

    Polishchuk, Pavel; Madzhidov, Timur; Gimadiev, Timur; Bodrov, Andrey; Nugmanov, Ramil; Varnek, Alexandre

    2017-07-01

    We describe a novel approach of reaction representation as a combination of two mixtures: a mixture of reactants and a mixture of products. In turn, each mixture can be encoded using an earlier reported approach involving simplex descriptors (SiRMS). The feature vector representing these two mixtures results from either concatenated product and reactant descriptors or the difference between descriptors of products and reactants. This reaction representation doesn't need an explicit labeling of a reaction center. The rigorous "product-out" cross-validation (CV) strategy has been suggested. Unlike the naïve "reaction-out" CV approach based on a random selection of items, the proposed one provides with more realistic estimation of prediction accuracy for reactions resulting in novel products. The new methodology has been applied to model rate constants of E2 reactions. It has been demonstrated that the use of the fragment control domain applicability approach significantly increases prediction accuracy of the models. The models obtained with new "mixture" approach performed better than those required either explicit (Condensed Graph of Reaction) or implicit (reaction fingerprints) reaction center labeling.

  4. Structure-reactivity modeling using mixture-based representation of chemical reactions.

    PubMed

    Polishchuk, Pavel; Madzhidov, Timur; Gimadiev, Timur; Bodrov, Andrey; Nugmanov, Ramil; Varnek, Alexandre

    2017-07-27

    We describe a novel approach of reaction representation as a combination of two mixtures: a mixture of reactants and a mixture of products. In turn, each mixture can be encoded using an earlier reported approach involving simplex descriptors (SiRMS). The feature vector representing these two mixtures results from either concatenated product and reactant descriptors or the difference between descriptors of products and reactants. This reaction representation doesn't need an explicit labeling of a reaction center. The rigorous "product-out" cross-validation (CV) strategy has been suggested. Unlike the naïve "reaction-out" CV approach based on a random selection of items, the proposed one provides with more realistic estimation of prediction accuracy for reactions resulting in novel products. The new methodology has been applied to model rate constants of E2 reactions. It has been demonstrated that the use of the fragment control domain applicability approach significantly increases prediction accuracy of the models. The models obtained with new "mixture" approach performed better than those required either explicit (Condensed Graph of Reaction) or implicit (reaction fingerprints) reaction center labeling.

  5. Evaluation of an extraction method for a mixture of endocrine disrupters in sediment using chemical and in vitro biological analyses.

    PubMed

    Creusot, Nicolas; Dévier, Marie-Hélène; Budzinski, Hélène; Aït-Aïssa, Selim

    2016-06-01

    Aquatic sediments are contaminated by a wide diversity of organic pollutants such as endocrine-disrupting chemicals (EDCs) which encompass a broad range of chemical classes having natural and anthropogenic origins. The use of in vitro bioassays is now widely accepted as an alternative method for their detection in complex samples. However, based on the diversity of EDC chemical properties, their common extraction is difficult and comprehensive validation of extraction methods for a bioanalysis purpose is still weakly documented. In this study, we compared the performance of several organic solvents, i.e., acetone, methanol, dichloromethane, heptane, dichloromethane/acetone (50:50, v/v), dichloromethane/methanol (50:50, v/v), heptane/acetone (50:50, v/v), and heptane/methanol (50:50, v/v), to extract a diversity of active chemicals from a spiked sediment matrix using pressurized liquid extraction. For this purpose, we defined a mixture of 12 EDCs with a wide range of polarity (2 < log Kow < 8) (i.e., estrone, 17β-estradiol, bisphenol A, o,p'DDT, 4-tert-octylphenol, fenofibrate, triphenyl phosphate, clotrimazole, PCB-126, 2,3,7,8 TCDD, benzo[k]fluoranthene, and dibenzo[a,h]anthracene). Working concentrations of each individual compound in the mixture were determined as equipotent concentrations on the basis of the concentration-addition (CA) model applied to in vitro estrogenic, dioxin-like, and pregnane X receptor (PXR)-like activities. Extraction efficiencies based on both chemical and biological analyses were assessed in triplicate in artificial blank sediment spiked with this mixture and in natural sediment contaminated by native EDCs. In both spiked and natural sediment, MeOH/DCM yields the best recovery while heptane was the least efficient solvent. Our study provided the validation of a sediment extraction methodology for EDC bioanalysis purposes, which can be used for comprehensive environmental contamination characterization.

  6. Determinants of Exposure to Fragranced Product Chemical Mixtures in a Sample of Twins

    PubMed Central

    Gribble, Matthew O.; Bandeen-Roche, Karen; Fox, Mary A.

    2015-01-01

    Fragranced product chemical mixtures may be relevant for environmental health, but little is known about exposure. We analyzed results from an olfactory challenge with the synthetic musk fragrance 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopento-γ-2-benzopyran (HHCB), and a questionnaire about attitudes toward chemical safety and use of fragranced products, in a sample of 140 white and 17 black twin pairs attending a festival in Ohio. Data for each product were analyzed using robust ordered logistic regressions with random intercepts for “twin pair” and “sharing address with twin”, and fixed effects for sex, age, education, and “ever being bothered by fragrances”. Due to the small number of black participants, models were restricted to white participants except when examining racial differences. Overall patterns of association were summarized across product-types through random-effects meta-analysis. Principal components analysis was used to summarize clustering of product use. The dominant axis of variability in fragranced product use was “more vs. less”, followed by a distinction between household cleaning products and personal care products. Overall, males used fragranced products less frequently than females (adjusted proportionate odds ratio 0.55, 95% confidence interval 0.33, 0.93). This disparity was driven by personal care products (0.42, 95% CI: 0.19, 0.96), rather than household cleaning products (0.79, 95% CI: 0.49, 1.25) and was particularly evident for body lotion (0.12, 95% CI: 0.05, 0.27). Overall usage differed by age (0.64, 95% CI: 0.43, 0.95) but only hand soap and shampoo products differed significantly. “Ever being bothered by fragrance” had no overall association (0.92, 95% CI: 0.65, 1.30) but was associated with laundry detergent use (0.46, 95% CI: 0.23, 0.93). Similarly, black vs. white differences on average were not significant (1.34, 95% CI: 0.55, 3.28) but there were apparent differences in use of shampoo (0

  7. Immunological, chemical and clinical aspects of exposure to mixtures of contact allergens.

    PubMed

    Bonefeld, Charlotte M; Geisler, Carsten; Gimenéz-Arnau, Elena; Lepoittevin, Jean-Pierre; Uter, Wolfgang; Johansen, Jeanne D

    2017-09-01

    Allergic contact dermatitis is one of the most frequent forms of skin inflammation. Very often, we are exposed to mixtures of allergens with varying potencies, doses/areas, and exposure times. Therefore, improved knowledge about immune responses to combinations of contact allergens is highly relevant. In this article, we provide a general introduction to immune responses to contact allergens, and discuss the literature concerning immune responses to mixtures of allergens. According to the existing evidence, increased responses are induced following sensitization with combinations of allergens as compared with single allergens. The response to a mixture of allergens can be both additive and synergistic, depending on the dose and combination of allergens. Importantly, sensitization with combinations of either fragrance allergens or metal salts can result in increased challenge responses to specific allergens within the mixture. Taken together, the immune responses to mixtures of allergens are complex, and further studies are required to obtain the necessary knowledge to improve consumer safety. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Influence of Wetting and Mass Transfer Properties of Organic Chemical Mixtures in Vadose Zone Materials on Groundwater Contamination by Nonaqueous Phase Liquids

    SciTech Connect

    Charles J Werth; Albert J Valocchi, Hongkyu Yoon

    2011-05-21

    Previous studies have found that organic acids, organic bases, and detergent-like chemicals change surface wettability. The wastewater and NAPL mixtures discharged at the Hanford site contain such chemicals, and their proportions likely change over time due to reaction-facilitated aging. The specific objectives of this work were to (1) determine the effect of organic chemical mixtures on surface wettability, (2) determine the effect of organic chemical mixtures on CCl4 volatilization rates from NAPL, and (3) accurately determine the migration, entrapment, and volatilization of organic chemical mixtures. Five tasks were proposed to achieve the project objectives. These are to (1) prepare representative batches of fresh and aged NAPL-wastewater mixtures, (2) to measure interfacial tension, contact angle, and capillary pressure-saturation profiles for the same mixtures, (3) to measure interphase mass transfer rates for the same mixtures using micromodels, (4) to measure multiphase flow and interphase mass transfer in large flow cell experiments, all using the same mixtures, and (5) to modify the multiphase flow simulator STOMP in order to account for updated P-S and interphase mass transfer relationships, and to simulate the impact of CCl4 in the vadose zone on groundwater contamination. Results and findings from these tasks and summarized in the attached final report.

  9. Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead

    PubMed Central

    Goodson, William H.; Lowe, Leroy; Carpenter, David O.; Gilbertson, Michael; Manaf Ali, Abdul; Lopez de Cerain Salsamendi, Adela; Lasfar, Ahmed; Carnero, Amancio; Azqueta, Amaya; Amedei, Amedeo; Charles, Amelia K.; Collins, Andrew R.; Ward, Andrew; Salzberg, Anna C.; Colacci, Anna Maria; Olsen, Ann-Karin; Berg, Arthur; Barclay, Barry J.; Zhou, Binhua P.; Blanco-Aparicio, Carmen; Baglole, Carolyn J.; Dong, Chenfang; Mondello, Chiara; Hsu, Chia-Wen; Naus, Christian C.; Yedjou, Clement; Curran, Colleen S.; Laird, Dale W.; Koch, Daniel C.; Carlin, Danielle J.; Felsher, Dean W.; Roy, Debasish; Brown, Dustin G.; Ratovitski, Edward; Ryan, Elizabeth P.; Corsini, Emanuela; Rojas, Emilio; Moon, Eun-Yi; Laconi, Ezio; Marongiu, Fabio; Al-Mulla, Fahd; Chiaradonna, Ferdinando; Darroudi, Firouz; Martin, Francis L.; Van Schooten, Frederik J.; Goldberg, Gary S.; Wagemaker, Gerard; Nangami, Gladys N.; Calaf, Gloria M.; Williams, Graeme P.; Wolf, Gregory T.; Koppen, Gudrun; Brunborg, Gunnar; Lyerly, H. Kim; Krishnan, Harini; Ab Hamid, Hasiah; Yasaei, Hemad; Sone, Hideko; Kondoh, Hiroshi; Salem, Hosni K.; Hsu, Hsue-Yin; Park, Hyun Ho; Koturbash, Igor; Miousse, Isabelle R.; Scovassi, A.Ivana; Klaunig, James E.; Vondráček, Jan; Raju, Jayadev; Roman, Jesse; Wise, John Pierce; Whitfield, Jonathan R.; Woodrick, Jordan; Christopher, Joseph A.; Ochieng, Josiah; Martinez-Leal, Juan Fernando; Weisz, Judith; Kravchenko, Julia; Sun, Jun; Prudhomme, Kalan R.; Narayanan, Kannan Badri; Cohen-Solal, Karine A.; Moorwood, Kim; Gonzalez, Laetitia; Soucek, Laura; Jian, Le; D’Abronzo, Leandro S.; Lin, Liang-Tzung; Li, Lin; Gulliver, Linda; McCawley, Lisa J.; Memeo, Lorenzo; Vermeulen, Louis; Leyns, Luc; Zhang, Luoping; Valverde, Mahara; Khatami, Mahin; Romano, Maria Fiammetta; Chapellier, Marion; Williams, Marc A.; Wade, Mark; Manjili, Masoud H.; Lleonart, Matilde E.; Xia, Menghang; Gonzalez Guzman, Michael J.; Karamouzis, Michalis V.; Kirsch-Volders, Micheline; Vaccari, Monica; Kuemmerle, Nancy B.; Singh, Neetu; Cruickshanks, Nichola; Kleinstreuer, Nicole; van Larebeke, Nik; Ahmed, Nuzhat; Ogunkua, Olugbemiga; Krishnakumar, P.K.; Vadgama, Pankaj; Marignani, Paola A.; Ghosh, Paramita M.; Ostrosky-Wegman, Patricia; Thompson, Patricia A.; Dent, Paul; Heneberg, Petr; Darbre, Philippa; Leung, Po Sing; Nangia-Makker, Pratima; Cheng, Qiang (Shawn); Robey, R.Brooks; Al-Temaimi, Rabeah; Roy, Rabindra; Andrade-Vieira, Rafaela; Sinha, Ranjeet K.; Mehta, Rekha; Vento, Renza; Di Fiore, Riccardo; Ponce-Cusi, Richard; Dornetshuber-Fleiss, Rita; Nahta, Rita; Castellino, Robert C.; Palorini, Roberta; Hamid, Roslida A.; Langie, Sabine A.S.; Eltom, Sakina E.; Brooks, Samira A.; Ryeom, Sandra; Wise, Sandra S.; Bay, Sarah N.; Harris, Shelley A.; Papagerakis, Silvana; Romano, Simona; Pavanello, Sofia; Eriksson, Staffan; Forte, Stefano; Casey, Stephanie C.; Luanpitpong, Sudjit; Lee, Tae-Jin; Otsuki, Takemi; Chen, Tao; Massfelder, Thierry; Sanderson, Thomas; Guarnieri, Tiziana; Hultman, Tove; Dormoy, Valérian; Odero-Marah, Valerie; Sabbisetti, Venkata; Maguer-Satta, Veronique; Rathmell, W.Kimryn; Engström, Wilhelm; Decker, William K.; Bisson, William H.; Rojanasakul, Yon; Luqmani, Yunus; Chen, Zhenbang; Hu, Zhiwei

    2015-01-01

    Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety ‘Mode of Action’ framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology. PMID:26106142

  10. Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead.

    PubMed

    Goodson, William H; Lowe, Leroy; Carpenter, David O; Gilbertson, Michael; Manaf Ali, Abdul; Lopez de Cerain Salsamendi, Adela; Lasfar, Ahmed; Carnero, Amancio; Azqueta, Amaya; Amedei, Amedeo; Charles, Amelia K; Collins, Andrew R; Ward, Andrew; Salzberg, Anna C; Colacci, Annamaria; Olsen, Ann-Karin; Berg, Arthur; Barclay, Barry J; Zhou, Binhua P; Blanco-Aparicio, Carmen; Baglole, Carolyn J; Dong, Chenfang; Mondello, Chiara; Hsu, Chia-Wen; Naus, Christian C; Yedjou, Clement; Curran, Colleen S; Laird, Dale W; Koch, Daniel C; Carlin, Danielle J; Felsher, Dean W; Roy, Debasish; Brown, Dustin G; Ratovitski, Edward; Ryan, Elizabeth P; Corsini, Emanuela; Rojas, Emilio; Moon, Eun-Yi; Laconi, Ezio; Marongiu, Fabio; Al-Mulla, Fahd; Chiaradonna, Ferdinando; Darroudi, Firouz; Martin, Francis L; Van Schooten, Frederik J; Goldberg, Gary S; Wagemaker, Gerard; Nangami, Gladys N; Calaf, Gloria M; Williams, Graeme; Wolf, Gregory T; Koppen, Gudrun; Brunborg, Gunnar; Lyerly, H Kim; Krishnan, Harini; Ab Hamid, Hasiah; Yasaei, Hemad; Sone, Hideko; Kondoh, Hiroshi; Salem, Hosni K; Hsu, Hsue-Yin; Park, Hyun Ho; Koturbash, Igor; Miousse, Isabelle R; Scovassi, A Ivana; Klaunig, James E; Vondráček, Jan; Raju, Jayadev; Roman, Jesse; Wise, John Pierce; Whitfield, Jonathan R; Woodrick, Jordan; Christopher, Joseph A; Ochieng, Josiah; Martinez-Leal, Juan Fernando; Weisz, Judith; Kravchenko, Julia; Sun, Jun; Prudhomme, Kalan R; Narayanan, Kannan Badri; Cohen-Solal, Karine A; Moorwood, Kim; Gonzalez, Laetitia; Soucek, Laura; Jian, Le; D'Abronzo, Leandro S; Lin, Liang-Tzung; Li, Lin; Gulliver, Linda; McCawley, Lisa J; Memeo, Lorenzo; Vermeulen, Louis; Leyns, Luc; Zhang, Luoping; Valverde, Mahara; Khatami, Mahin; Romano, Maria Fiammetta; Chapellier, Marion; Williams, Marc A; Wade, Mark; Manjili, Masoud H; Lleonart, Matilde E; Xia, Menghang; Gonzalez, Michael J; Karamouzis, Michalis V; Kirsch-Volders, Micheline; Vaccari, Monica; Kuemmerle, Nancy B; Singh, Neetu; Cruickshanks, Nichola; Kleinstreuer, Nicole; van Larebeke, Nik; Ahmed, Nuzhat; Ogunkua, Olugbemiga; Krishnakumar, P K; Vadgama, Pankaj; Marignani, Paola A; Ghosh, Paramita M; Ostrosky-Wegman, Patricia; Thompson, Patricia A; Dent, Paul; Heneberg, Petr; Darbre, Philippa; Sing Leung, Po; Nangia-Makker, Pratima; Cheng, Qiang Shawn; Robey, R Brooks; Al-Temaimi, Rabeah; Roy, Rabindra; Andrade-Vieira, Rafaela; Sinha, Ranjeet K; Mehta, Rekha; Vento, Renza; Di Fiore, Riccardo; Ponce-Cusi, Richard; Dornetshuber-Fleiss, Rita; Nahta, Rita; Castellino, Robert C; Palorini, Roberta; Abd Hamid, Roslida; Langie, Sabine A S; Eltom, Sakina E; Brooks, Samira A; Ryeom, Sandra; Wise, Sandra S; Bay, Sarah N; Harris, Shelley A; Papagerakis, Silvana; Romano, Simona; Pavanello, Sofia; Eriksson, Staffan; Forte, Stefano; Casey, Stephanie C; Luanpitpong, Sudjit; Lee, Tae-Jin; Otsuki, Takemi; Chen, Tao; Massfelder, Thierry; Sanderson, Thomas; Guarnieri, Tiziana; Hultman, Tove; Dormoy, Valérian; Odero-Marah, Valerie; Sabbisetti, Venkata; Maguer-Satta, Veronique; Rathmell, W Kimryn; Engström, Wilhelm; Decker, William K; Bisson, William H; Rojanasakul, Yon; Luqmani, Yunus; Chen, Zhenbang; Hu, Zhiwei

    2015-06-01

    Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety 'Mode of Action' framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology. © The Author 2015. Published by Oxford University Press.

  11. Juvenile Male Rats Exposed to a Low-Dose Mixture of Twenty-Seven Environmental Chemicals Display Adverse Health Effects.

    PubMed

    Hadrup, Niels; Svingen, Terje; Mandrup, Karen; Skov, Kasper; Pedersen, Mikael; Frederiksen, Hanne; Frandsen, Henrik Lauritz; Vinggaard, Anne Marie

    2016-01-01

    Humans are exposed to a large number of environmental chemicals in their daily life, many of which are readily detectable in blood or urine. It remains uncertain if these chemicals can cause adverse health effects when present together at low doses. In this study we have tested whether a mixture of 27 chemicals administered orally to juvenile male rats for three months could leave a pathophysiological footprint. The mixture contained metals, perfluorinated compounds, PCB, dioxins, pesticides, heterocyclic amines, phthalate, PAHs and others, with a combined dose of 0.16 (Low dose), 0.47 (Mid dose) or 1.6 (High dose) mg/kg bw/day. The lowest dose was designed with the aim of obtaining plasma or urine concentrations in rats at levels approaching those observed in humans. Some single congeners were administered at doses representative of combined doses for chemical groups. With this baseline, we found effects on weight, histology and gene expression in the liver, as well as changes to the blood plasma metabolome in all exposure groups, including low-dose. Additional adverse effects were observed in the higher dosed groups, including enlarged kidneys and alterations to the metabolome. No significant effects on reproductive parameters were observed.

  12. Toward a conceptual approach for assessing risks from chemical mixtures and other stressors to coastal ecosystem services.

    PubMed

    Syberg, Kristian; Backhaus, Thomas; Banta, Gary; Bruce, Peter; Gustavsson, Mikael; Munns, Wayne R; Rämö, Robert; Selck, Henriette; Gunnarsson, Jonas S

    2017-03-01

    Growth of human populations and increased human activity, particularly in coastal areas, increase pressure on coastal ecosystems and the ecosystem services (ES) they provide. As a means toward being able to assess the impact of multiple stressors on ES, in the present study we propose an 8-step conceptual approach for assessing effects of chemical mixtures and other stressors on ES in coastal areas: step A, identify the relevant problems and policy aims; step B, identify temporal and spatial boundaries; step C, identify relevant ES; step D, identify relevant stressors (e.g., chemicals); step E, translate impacts into ES units; step F, assess cumulative risk in ES units; step G, rank stressors based on their contribution to adverse effects on ES; and step H, implement regulation and management as appropriate and necessary. Two illustrative case studies (Swedish coastal waters and a coastal lagoon in Costa Rica) are provided; one focuses on chemicals that affect human food supply and the other addresses pesticide runoff and trade-offs among ES. The 2 cases are used to highlight challenges of such risk assessments, including use of standardized versus ES-relevant test species, data completeness, and trade-offs among ES. Lessons learned from the 2 case studies are discussed in relation to environmental risk assessment and management of chemical mixtures. Integr Environ Assess Manag 2017;13:376-386. © 2016 SETAC. © 2016 SETAC.

  13. Juvenile Male Rats Exposed to a Low-Dose Mixture of Twenty-Seven Environmental Chemicals Display Adverse Health Effects

    PubMed Central

    Svingen, Terje; Mandrup, Karen; Skov, Kasper; Pedersen, Mikael; Frederiksen, Hanne; Frandsen, Henrik Lauritz; Vinggaard, Anne Marie

    2016-01-01

    Humans are exposed to a large number of environmental chemicals in their daily life, many of which are readily detectable in blood or urine. It remains uncertain if these chemicals can cause adverse health effects when present together at low doses. In this study we have tested whether a mixture of 27 chemicals administered orally to juvenile male rats for three months could leave a pathophysiological footprint. The mixture contained metals, perfluorinated compounds, PCB, dioxins, pesticides, heterocyclic amines, phthalate, PAHs and others, with a combined dose of 0.16 (Low dose), 0.47 (Mid dose) or 1.6 (High dose) mg/kg bw/day. The lowest dose was designed with the aim of obtaining plasma or urine concentrations in rats at levels approaching those observed in humans. Some single congeners were administered at doses representative of combined doses for chemical groups. With this baseline, we found effects on weight, histology and gene expression in the liver, as well as changes to the blood plasma metabolome in all exposure groups, including low-dose. Additional adverse effects were observed in the higher dosed groups, including enlarged kidneys and alterations to the metabolome. No significant effects on reproductive parameters were observed. PMID:27598887

  14. An experimental and detailed chemical kinetic modeling study of hydrogen and syngas mixture oxidation at elevated pressures

    DOE PAGES

    Keromnes, Alan; Metcalfe, Wayne K.; Heufer, Karl A.; ...

    2013-03-12

    The oxidation of syngas mixtures was investigated experimentally and simulated with an updated chemical kinetic model. Ignition delay times for H2/CO/O2/N2/Ar mixtures have been measured using two rapid compression machines and shock tubes at pressures from 1 to 70 bar, over a temperature range of 914–2220 K and at equivalence ratios from 0.1 to 4.0. Results show a strong dependence of ignition times on temperature and pressure at the end of the compression; ignition delays decrease with increasing temperature, pressure, and equivalence ratio. The reactivity of the syngas mixtures was found to be governed by hydrogen chemistry for CO concentrationsmore » lower than 50% in the fuel mixture. For higher CO concentrations, an inhibiting effect of CO was observed. Flame speeds were measured in helium for syngas mixtures with a high CO content and at elevated pressures of 5 and 10 atm using the spherically expanding flame method. A detailed chemical kinetic mechanism for hydrogen and H2/CO (syngas) mixtures has been updated, rate constants have been adjusted to reflect new experimental information obtained at high pressures and new rate constant values recently published in the literature. Experimental results for ignition delay times and flame speeds have been compared with predictions using our newly revised chemical kinetic mechanism, and good agreement was observed. In the mechanism validation, particular emphasis is placed on predicting experimental data at high pressures (up to 70 bar) and intermediate- to high-temperature conditions, particularly important for applications in internal combustion engines and gas turbines. The reaction sequence H2 + HO˙2 ↔ H˙+H2O2 followed by H2O2(+M) ↔ O˙H+O˙H(+M) was found to play a key role in hydrogen ignition under high-pressure and intermediate-temperature conditions. The rate constant for H2+HO˙2 showed strong sensitivity to high-pressure ignition times and has considerable uncertainty, based on literature values

  15. An experimental and detailed chemical kinetic modeling study of hydrogen and syngas mixture oxidation at elevated pressures

    SciTech Connect

    Keromnes, Alan; Metcalfe, Wayne K.; Heufer, Karl A.; Donohoe, Nicola; Das, Apurba K.; Sung, Chih -Jen; Herzler, Jurgen; Naumann, Clemens; Griebel, Peter; Mathieu, Olivier; Krejci, Michael C.; Petersen, Eric L.; Pitz, William J.; Curran, Henry J.

    2013-03-12

    The oxidation of syngas mixtures was investigated experimentally and simulated with an updated chemical kinetic model. Ignition delay times for H2/CO/O2/N2/Ar mixtures have been measured using two rapid compression machines and shock tubes at pressures from 1 to 70 bar, over a temperature range of 914–2220 K and at equivalence ratios from 0.1 to 4.0. Results show a strong dependence of ignition times on temperature and pressure at the end of the compression; ignition delays decrease with increasing temperature, pressure, and equivalence ratio. The reactivity of the syngas mixtures was found to be governed by hydrogen chemistry for CO concentrations lower than 50% in the fuel mixture. For higher CO concentrations, an inhibiting effect of CO was observed. Flame speeds were measured in helium for syngas mixtures with a high CO content and at elevated pressures of 5 and 10 atm using the spherically expanding flame method. A detailed chemical kinetic mechanism for hydrogen and H2/CO (syngas) mixtures has been updated, rate constants have been adjusted to reflect new experimental information obtained at high pressures and new rate constant values recently published in the literature. Experimental results for ignition delay times and flame speeds have been compared with predictions using our newly revised chemical kinetic mechanism, and good agreement was observed. In the mechanism validation, particular emphasis is placed on predicting experimental data at high pressures (up to 70 bar) and intermediate- to high-temperature conditions, particularly important for applications in internal combustion engines and gas turbines. The reaction sequence H2 + HO˙2 ↔ H˙+H2O2 followed by H2O2(+M) ↔ O˙H+O˙H(+M) was found to play a key role in hydrogen ignition under high-pressure and intermediate-temperature conditions. The rate constant for H2+HO˙2

  16. Effect-based approach for screening of chemical mixtures in whole blood of green turtles from the Great Barrier Reef.

    PubMed

    Dogruer, Gülsah; Weijs, Liesbeth; Tang, Janet Yat-Man; Hollert, Henner; Kock, Marjolijn; Bell, Ian; Madden Hof, Christine A; Gaus, Caroline

    2017-08-27

    Organisms are exposed to mixtures of both known and unknown chemicals which are diverse and variable, and thus difficult and costly to characterise and monitor using traditional target analyses. The objective of this study was to validate and apply in vitro effect-based methods by which whole blood can be used to screen internal exposure to such complex chemical mixtures. For this study, we used whole blood of green sea turtles (Chelonia mydas). To ensure the chemical mixture in blood is transferred with minimal losses or bias, we tested a modified QuEChERS extraction method specifically developed for multi- and non-target instrument analysis. The extracts were dosed to a battery of in vitro bioassays (AhR-CAFLUX, AREc32, NFκB-bla, VM7Luc4E2, Microtox), each with a different mode of action (e.g., AhR receptor mediated xenobiotics, NrF2-mediated oxidative stress, NFκB mediated response to inflammation, estrogen activity and baseline toxicity oxidative stress, respectively) in order to cover a wide spectrum of chemicals. Results confirmed the absence of interferences of the blood extract with the responses of the different assays, thus indicating the methods' compatibility with effect-based screening approaches. To apply this approach, whole blood samples were collected from green turtles foraging in agricultural, urban and remote areas of the Australian Great Barrier Reef. The effect-based screening revealed significant differences in exposure, with higher induction of AhR-CAFLUX, AREc32 and Microtox assays in turtles from the agricultural foraging ground. Overall, these results corroborated with concurrent health, target and non-target analyses in the same animals performed as part of a larger program. This study provides evidence that the proposed effect-based approach is suitable for screening and evaluating internal exposure of organisms to chemical mixtures. The approach could be valuable for advancing understanding on multiple levels ranging from

  17. Low dose mixture effects of endocrine disrupters and their implications for regulatory thresholds in chemical risk assessment.

    PubMed

    Kortenkamp, Andreas

    2014-12-01

    Today's chemical exposures are characterised by a widely spread blanket of contamination composed of myriads of chemicals, many of them endocrine disrupters, all at rather low levels. With their focus on considering single chemicals one by one, the approaches used by regulatory bodies worldwide for safety assessments of chemicals cannot keep up with these pollution patterns. A substantial challenge lies in the assessment of combination effects from large numbers of endocrine disrupters and other chemicals, all at low doses. We retrace the development of experimental and conceptual approaches required for assessing low dose mixtures, with an emphasis on work with endocrine disrupting chemicals. We find that nearly 20 years of research has produced good evidence for combination effects at levels around experimental thresholds. One obstacle in deciding on the relevance of this evidence is incomplete information about the range of endocrine-disrupting chemicals that make up combined exposures. These knowledge gaps need to be closed urgently, as is currently discussed under the heading of exposome research.

  18. Manipulating Simple Reactive Chemical Units: Fishing for Alkaloids from Complex Mixtures.

    PubMed

    Poupon, Erwan; Gravel, Edmond

    2015-07-20

    This Concept article describes how key C10 molecular scaffolds, too reactive to be obtained through classical multistep synthesis, were targeted in the most simple reaction conditions, reproducing those that may be encountered in living cells. The rationale was that small amounts of these reactive intermediates might be formed in situ from cheap and abundant reactants (i.e., glutaraldehyde and tetrahydropyridine) resulting, upon further rearrangement in "complex mixtures" from which natural substances would arise. From five types of mixtures, at least six full carbon skeletons of known natural substances were formed spontaneously. This work also led to the discovery of new plausible biosynthetic achiral precursors in the Nitraria metabolism.

  19. A preliminary investigation into the physical and chemical properties of biomass ashes used as aggregate fillers for bituminous mixtures.

    PubMed

    Melotti, Roberto; Santagata, Ezio; Bassani, Marco; Salvo, Milena; Rizzo, Stefano

    2013-09-01

    Fly and bottom ashes are the main by-products arising from the combustion of solid biomass. Since the production of energy from this source is increasing, the processing and disposal of the resulting ashes has become an environmental and economic issue. Such ashes are of interest as a construction material because they are composed of very fine particles similar to fillers normally employed in bituminous and cementitious mixtures. This research investigates the potential use of ash from biomass as filler in bituminous mixtures. The morphological, physical and chemical characteristics of 21 different ashes and two traditional fillers (calcium carbonate and "recovered" plant filler) were evaluated and discussed. Leaching tests, performed in order to quantify the release of pollutants, revealed that five ashes do not comply with the Italian environmental re-use limits. Experimental results show a wide range of values for almost all the investigated properties and a low correlation with biomass type in terms of origin and chemical composition. Furthermore, sieving and milling processes were found to improve the properties of the raw material in terms of grading and sample porosity. The effectiveness of these treatments and the low content of organic matter and harmful fines suggest that most of the biomass ashes investigated may be regarded as potential replacements for natural filler in bituminous mixtures.

  20. Chemical induction of tumors in oysters by a mixture of aromatic and chlorinated hydrocarbons, amines and metals

    SciTech Connect

    Gardner, G.R.; Pruell, R.J.; Malcolm, A.R.

    1992-01-01

    Tumors were induced in eastern oysters (Crassostrea virginica) by a mixture of aromatic hydrocarbons, an aromatic amine, polychlorinated biphenyls, chlorinated hydrocarbons, a nitrosoamine and heavy metals. Kidney and enteric tumors developed in oysters following exposure to a mixture containing 3,4-benzopyrene, 1,2-benzanthracene, 2-aminofluorene, N-nitrosodiethylamine, technical chlordane, Aroclors 1242 and 1254, p,p'-DDE, cadmium (CdCl2), chromium (K2CrO4) and lead (Pb(NO3)2). 2-Aminofluorene and N-nitrosodiethylamine, not measured in Black Rock Harbor sediment, were both added at 0.6 and 6.0 micrograms/g dry sediment. A 3% prevalence of low-grade renal and gastrointestinal tumors developed after 30 days in oysters fed water-column suspended sediment particulate spiked with the mixture of chemicals. Disease progression was most advanced in enteric adenomas. Both types are comparable to those produced after 30 days in the same organs by chemically contaminated Black Rock Harbor sediment.

  1. Demonstration of a rapidly-swept external cavity quantum cascade laser for rapid and sensitive quantification of chemical mixtures

    SciTech Connect

    Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.

    2016-02-13

    A rapidly-swept external cavity quantum cascade laser (ECQCL) system for fast open-path quantification of multiple chemicals and mixtures is presented. The ECQCL system is swept over its entire tuning range (>100 cm-1) at frequencies up to 200 Hz. At 200 Hz the wavelength tuning rate and spectral resolution are 2x104 cm-1/sec and < 0.2 cm-1, respectively. The capability of the current system to quantify changes in chemical concentrations on millesecond timescales is demonstrated at atmospheric pressure using an open-path multi-pass cell. The detection limits for chemicals ranged from ppb to ppm levels depending on the absorption cross-section.

  2. Demonstration of a rapidly-swept external cavity quantum cascade laser for rapid and sensitive quantification of chemical mixtures

    SciTech Connect

    Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.

    2016-02-13

    A rapidly-swept external cavity quantum cascade laser (ECQCL) system for fast open-path quantification of multiple chemicals and mixtures is presented. The ECQCL system is swept over its entire tuning range (>100 cm-1) at frequencies up to 200 Hz. At 200 Hz the wavelength tuning rate and spectral resolution are 2x104 cm-1/sec and < 0.2 cm-1, respectively. The capability of the current system to quantify changes in chemical concentrations on millesecond timescales is demonstrated at atmospheric pressure using an open-path multi-pass cell. The detection limits for chemicals ranged from ppb to ppm levels depending on the absorption cross-section.

  3. Combining Toxicological and Chemical Characterization of Complex Mixtures to Understand the Impact of the Unknown Fraction

    EPA Science Inventory

    Toxicological assessment of adverse health outcomes associated with exposure to complex mixtures provides an integrated response of the organism (or in vitro test system) that accounts for additivity among the components (both dose and response) as well as any greater than or les...

  4. SOLUBILITY, SORPTION AND TRANSPORT OF HYDROPHOBIC ORGANIC CHEMICALS IN COMPLEX MIXTURES

    EPA Science Inventory

    The research summarized in this report focuses on the effects which organic cosolvents have on the sorption and mobility of organic contaminants. This work was initiated In an effort to improve our understanding of the environmental consequences associated with complex mixtur...

  5. SOLUBILITY, SORPTION AND TRANSPORT OF HYDROPHOBIC ORGANIC CHEMICALS IN COMPLEX MIXTURES

    EPA Science Inventory

    The research summarized in this report focuses on the effects which organic cosolvents have on the sorption and mobility of organic contaminants. This work was initiated In an effort to improve our understanding of the environmental consequences associated with complex mixtur...

  6. Combining Toxicological and Chemical Characterization of Complex Mixtures to Understand the Impact of the Unknown Fraction

    EPA Science Inventory

    Toxicological assessment of adverse health outcomes associated with exposure to complex mixtures provides an integrated response of the organism (or in vitro test system) that accounts for additivity among the components (both dose and response) as well as any greater than or les...

  7. Modification of wheat starch with succinic acid/acetanhydride and azelaic acid/acetanhydride mixtures. II. Chemical and physical properties.

    PubMed

    Ačkar, Durđica; Subarić, Drago; Babić, Jurislav; Miličević, Borislav; Jozinović, Antun

    2014-08-01

    The aim of this research was to investigate the influence of modification with succinic acid/acetanhydride and azelaic acid/acetanhydride mixtures on chemical and physical properties of wheat starch. Starch was isolated from two wheat varieties and modified with mixtures of succinic acid and acetanhydride and azelaic acid and acetanhydride in 4, 6 and 8% (w/w). Total starch content, resistant starch content, degree of modification, changes in FT-IR spectra, colour, gel texture and freeze-thaw stability were determined. Results showed that resistant starch content increased by both investigated modifications, and degree of modification increased proportionally to amount of reagents used. FT-IR analysis of modified starches showed peak around 1,740 cm(-1), characteristic for carbonyl group of ester. Total colour difference caused by modifications was detectable by trained people. Adhesiveness significantly increased, while freeze-thaw stability decreased by both investigated modifications.

  8. In vitro test systems supporting the development of improved pest control methods: a case study with chemical mixtures and bivalve biofoulers.

    PubMed

    Silva, Carlos; Nunes, Bruno; Nogueira, António Ja; Gonçalves, Fernando; Pereira, Joana L

    2016-11-01

    Using the bivalve macrofouler Corbicula fluminea, the suitability of in vitro testing as a stepping stone towards the improvement of control methods based on chemical mixtures was addressed in this study. In vitro cholinesterase (ChE) activity inhibition following single exposure of C. fluminea tissue to four model chemicals (the organophosphates dimethoate and dichlorvos, copper and sodium dodecyl phosphate [SDS]) was first assessed. Consequently, mixtures of dimethoate with copper and dichlorvos with SDS were tested and modelled; mixtures with ChE revealed synergistic interactions for both chemical pairs. These synergic combinations were subsequently validated in vivo and the increased control potential of these selected combinations was verified, with gains of up to 50% in C. fluminea mortality relative to corresponding single chemical treatments. Such consistency supports the suitability of using time- and cost-effective surrogate testing platforms to assist the development of biofouling control strategies incorporating mixtures.

  9. Demonstration of a rapidly-swept external cavity quantum cascade laser for rapid and sensitive quantification of chemical mixtures

    NASA Astrophysics Data System (ADS)

    Brumfield, B. E.; Taubman, M. S.; Phillips, M. C.

    2016-02-01

    A rapidly-swept external-cavity quantum cascade laser with an open-path Herriott cell is used to quantify gas-phase chemical mixtures of D2O and HDO at an update rate of 40 Hz (25 ms measurement time). The chemical mixtures were generated by evaporating D2O liquid near the open-path Herriott cell, allowing the H/D exchange reaction with ambient H2O to produce HDO. Fluctuations in the ratio of D2O and HDO on timescales of < 1 s due to the combined effects of plume transport and the H/D exchange chemical reaction are observed. Based on a noise equivalent concentration analysis of the current system, detection limits of 147.0 ppbv and 151.6 ppbv in a 25 ms measurement time are estimated for D2O and HDO respectively with a 127 m optical path. These detection limits are reduced to 23.0 and 24.0 ppbv with a 1 s averaging time for D2O and HDO respectively. Detection limits < 200 ppbv are also estimated for N2O, F134A, CH4, Acetone, and SO2 for a 25 ms measurement time.

  10. Sex-specific enhanced behavioral toxicity induced by maternal exposure to a mixture of low dose endocrine-disrupting chemicals.

    PubMed

    Sobolewski, Marissa; Conrad, Katherine; Allen, Joshua L; Weston, Hiromi; Martin, Kyle; Lawrence, B Paige; Cory-Slechta, Deborah A

    2014-12-01

    Humans are increasingly and consistently exposed to a variety of endocrine disrupting chemicals (EDCs), chemicals that have been linked to neurobehavioral disorders such as ADHD and autism. Many of such EDCs have been shown to adversely influence brain mesocorticolimbic systems raising the potential for cumulative toxicity. As such, understanding the effects of developmental exposure to mixtures of EDCs is critical to public health protection. Consequently, this study compared the effects of a mixture of four EDCs to their effects alone to examine potential for enhanced toxicity, using behavioral domains and paradigms known to be mediated by mesocorticolimbic circuits (fixed interval (FI) schedule controlled behavior, novel object recognition memory and locomotor activity) in offspring of pregnant mice that had been exposed to vehicle or relatively low doses of four EDCs, atrazine (ATR - 10mg/kg), perfluorooctanoic acid (PFOA - 0.1mg/kg), bisphenol-A (BPA - 50 μg/kg), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD - 0.25 μg/kg) alone or combined in a mixture (MIX), from gestational day 7 until weaning. EDC-treated males maintained significantly higher horizontal activity levels across three testing sessions, indicative of delayed habituation, whereas no effects were found in females. Statistically significant effects of MIX were seen in males, but not females, in the form of increased FI response rates, in contrast to reductions in response rate with ATR, BPA and TCDD, and reduced short term memory in the novel object recognition paradigm. MIX also reversed the typically lower neophobia levels of males compared to females. With respect to individual EDCs, TCDD produced notable increases in FI response rates in females, and PFOA significantly increased ambulatory locomotor activity in males. Collectively, these findings show the potential for enhanced behavioral effects of EDC mixtures in males and underscore the need for animal studies to fully investigate mixtures

  11. Endocrine-Disrupting Chemicals and Oil and Natural Gas Operations: Potential Environmental Contamination and Recommendations to Assess Complex Environmental Mixtures

    PubMed Central

    Kassotis, Christopher D.; Tillitt, Donald E.; Lin, Chung-Ho; McElroy, Jane A.; Nagel, Susan C.

    2015-01-01

    Background Hydraulic fracturing technologies, developed over the last 65 years, have only recently been combined with horizontal drilling to unlock oil and gas reserves previously deemed inaccessible. Although these technologies have dramatically increased domestic oil and natural gas production, they have also raised concerns for the potential contamination of local water supplies with the approximately 1,000 chemicals that are used throughout the process, including many known or suspected endocrine-disrupting chemicals. Objectives We discuss the need for an endocrine component to health assessments for drilling-dense regions in the context of hormonal and antihormonal activities for chemicals used. Methods We discuss the literature on a) surface and groundwater contamination by oil and gas extraction operations, and b) potential human exposure, particularly in the context of the total hormonal and antihormonal activities present in surface and groundwater from natural and anthropogenic sources; we also discuss initial analytical results and critical knowledge gaps. Discussion In light of the potential for environmental release of oil and gas chemicals that can disrupt hormone receptor systems, we recommend methods for assessing complex hormonally active environmental mixtures. Conclusions We describe a need for an endocrine-centric component for overall health assessments and provide information supporting the idea that using such a component will help explain reported adverse health trends as well as help develop recommendations for environmental impact assessments and monitoring programs. Citation Kassotis CD, Tillitt DE, Lin CH, McElroy JA, Nagel SC. 2016. Endocrine-disrupting chemicals and oil and natural gas operations: potential environmental contamination and recommendations to assess complex environmental mixtures. Environ Health Perspect 124:256–264; http://dx.doi.org/10.1289/ehp.1409535 PMID:26311476

  12. Chemical potentials and phase equilibria of Lennard-Jones mixtures: a self-consistent integral equation approach.

    PubMed

    Wilson, D Scott; Lee, Lloyd L

    2005-07-22

    We explore the vapor-liquid phase behavior of binary mixtures of Lennard-Jones-type molecules where one component is supercritical, given the system temperature. We apply the self-consistency approach to the Ornstein-Zernike integral equations to obtain the correlation functions. The consistency checks include not only thermodynamic consistencies (pressure consistency and Gibbs-Duhem consistency), but also pointwise consistencies, such as the zero-separation theorems on the cavity functions. The consistencies are enforced via the bridge functions in the closure which contain adjustable parameters. The full solution requires the values of not only the monomer chemical potentials, but also the dimer chemical potentials present in the zero-separation theorems. These are evaluated by the direct chemical-potential formula [L. L. Lee, J. Chem. Phys. 97, 8606 (1992)] that does not require temperature nor density integration. In order to assess the integral equation accuracy, molecular-dynamics simulations are carried out alongside the states studied. The integral equation results compare well with simulation data. In phase calculations, it is important to have pressure consistency and valid chemical potentials, since the matching of phase boundaries requires the equality of the pressures and chemical potentials of both the liquid and vapor phases. The mixtures studied are methane-type and pentane-type molecules, both characterized by effective Lennard-Jones potentials. Calculations on one isotherm show that the integral equation approach yields valid answers as compared with the experimental data of Sage and Lacey. To study vapor-liquid phase behavior, it is necessary to use consistent theories; any inconsistencies, especially in pressure, will vitiate the phase boundary calculations.

  13. Component Identification in Multi-Chemical Mixtures With Swept-Wavelength Resonant-Raman Spectroscopy

    DTIC Science & Technology

    2011-03-18

    efficiency of the OPO, but ranges from up to 15 mW on target in the UV to 50 mW in the visible. This ability to illuminate a target with a broad...been back illuminated and coated for enhanced UV response. The run file which automates the collection process uses several input parameters to...analyzed by a Agilent spectrophotometer to determine absorbance characteristics of the liquid. The remaining mixture was then placed into a standard UV

  14. Reaction Ensemble Molecular Dynamics: Direct Simulation of the Dynamic Equilibrium Properties of Chemically Reacting Mixtures

    DTIC Science & Technology

    2006-09-01

    Therefore, dynamic quantities of reaction mixtures such as the velocity autocorrelation functions and the diffusion coefficients can be accurately...using the virial expression [25]. A standard NVT molecular dynamics method was em- ployed with the equations of motion solved using the Verlet leapfrog...configurational energy, pressure, and species concen- trations) are compared to quantities calculated by the RxMC approach. Second , the dynamic quantities

  15. Shock-induced chemical reactions in a Ni/Al powder mixture

    SciTech Connect

    Yang, Y.; Gould, R.D.; Horie, Y.; Iyer, K.R.

    1997-06-01

    A new 50 mm powder gun was used to reproduce and to extend the real-time observations of ultra-fast exothermic reactions in a Ni/Al powder mixture at the shock front. Shock profiles measured by a manganin gauge show that (1) the threshold pressure for reaction is about 14 GPa; (2) the initiation criteria based either on shock energy or melting are in contradiction with experimental evidence. {copyright} {ital 1997 American Institute of Physics.}

  16. Computational Approaches for Predicting Nonlinear Interactions of Chemical Mixtures in Biological Systems

    DTIC Science & Technology

    2009-12-01

    Wright Patterson Air Force Base (WPAFB), Dayton, OH. Contributions 2008 - Active discussion and debate on the progress and status of fuel...Transition of tissue pharmacokinetic datasets for n-alkane/ PAH (naphthalene) mixture exposure in the rat to The Hamner Institutes for Health Sciences...utilized commercially available absorbent tubes (Carbotrap 300 thermal desorption (TDS) charcoal tubes (Supelco, St. Louis, MO)) to measure hydrocarbon

  17. Combining polar organic chemical integrative samplers (POCIS) with toxicity testing to evaluate pesticide mixture effects on natural phototrophic biofilms.

    PubMed

    Pesce, Stéphane; Morin, Soizic; Lissalde, Sophie; Montuelle, Bernard; Mazzella, Nicolas

    2011-03-01

    Polar organic chemical integrative samplers (POCIS) are valuable tools in passive sampling methods for monitoring polar organic pesticides in freshwaters. Pesticides extracted from the environment using such methods can be used to toxicity tests. This study evaluated the acute effects of POCIS extracts on natural phototrophic biofilm communities. Our results demonstrate an effect of POCIS pesticide mixtures on chlorophyll a fluorescence, photosynthetic efficiency and community structure. Nevertheless, the range of biofilm responses differs according to origin of the biofilms tested, revealing spatial variations in the sensitivity of natural communities in the studied stream. Combining passive sampler extracts with community-level toxicity tests offers promising perspectives for ecological risk assessment.

  18. Explanation of non-additive effects in mixtures of similar mode of action chemicals.

    PubMed

    Kamo, Masashi; Yokomizo, Hiroyuki

    2015-09-01

    Many models have been developed to predict the combined effect of drugs and chemicals. Most models are classified into two additive models: independent action (IA) and concentration addition (CA). It is generally considered if the modes of action of chemicals are similar then the combined effect obeys CA; however, many empirical studies report nonlinear effects deviating from the predictions by CA. Such deviations are termed synergism and antagonism. Synergism, which leads to a stronger toxicity, requires more careful management, and hence it is important to understand how and which combinations of chemicals lead to synergism. In this paper, three types of chemical reactions are mathematically modeled and the cause of the nonlinear effects among chemicals with similar modes of action was investigated. Our results show that combined effects obey CA only when the modes of action are exactly the same. Contrary to existing knowledge, combined effects are generally nonlinear even if the modes of action of the chemicals are similar. Our results further show that the nonlinear effects vanish out when the chemical concentrations are low, suggesting that the current management procedure of assuming CA is rarely inappropriate because environmental concentrations of chemicals are generally low. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  19. Current approaches toward chemical mixture studies at the National Institute of Environmental Health Sciences and the U.S. National Toxicology Program.

    PubMed

    Bucher, J R; Lucier, G

    1998-12-01

    The National Institute of Environmental Health Sciences (NIEHS) has several new initiatives involving chemical mixtures and has recognized the need to develop new experimental approaches to enhance our efforts in this area. Responding to recent increases in nominations of complex occupational exposures for toxicologic assessment by the U.S. National Toxicology Program, the NIEHS and the National Institute for Occupational Safety and Health have begun a program to characterize exposures through field studies, identify biomarkers of exposure in workers, and recreate relevant mixed exposures in a laboratory setting. A second initiative with the National Center for Environmental Health/Centers for Disease Control and Prevention will examine blood samples from the U.S. National Health and Nutrition Examination Survey population surveys for selected endocrine-disrupting agents and for common patterns of persistent xenobiotics, providing critical information for the design of animal studies to assess risks of relevant chemical mixtures to humans. New toxicology testing methods (lower cost, faster) will enhance our ability to study chemical mixtures (e.g., dioxin and dioxinlike chemicals, combination AIDS therapies). Ongoing method development efforts involve in vitro functional toxicology assays, screens for estrogenic activity, and carcinogenesis studies in transgenic mice. A major scientific initiative with mixtures involves studies of individual and mixtures of dioxin and dioxinlike chemicals to determine if toxic equivalence factors predict carcinogenic potency in traditional and transgenic bioassays. Complementing these studies is an increased emphasis on physiologically based pharmacokinetic modeling, an activity central to the proper interpretation of chemical mixture studies.

  20. Chemical-agnostic hazard prediction: statistical inference of in vitro toxicity pathways from proteomics responses to chemical mixtures

    EPA Science Inventory

    Toxicity pathways have been defined as normal cellular pathways that, when sufficiently perturbed as a consequence of chemical exposure, lead to an adverse outcome. If an exposure alters one or more normal biological pathways to an extent that leads to an adverse toxicity outcome...

  1. 40 CFR 180.900 - Exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From... granted when it appears that the total quantity of the pesticide chemical in or on all raw...

  2. 40 CFR 180.900 - Exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From... granted when it appears that the total quantity of the pesticide chemical in or on all raw...

  3. Immunomodulation of Mytilus hemocytes by individual estrogenic chemicals and environmentally relevant mixtures of estrogens: in vitro and in vivo studies.

    PubMed

    Canesi, Laura; Lorusso, Lucia Cecilia; Ciacci, Caterina; Betti, Michele; Rocchi, Marco; Pojana, Giulio; Marcomini, Antonio

    2007-02-15

    Endocrine disrupting compounds (EDCs) are almost ubiquitous in the aquatic environment. In the marine bivalve Mytilus the natural estrogen 17beta-estradiol (E2) and different EDCs have been recently demonstrated to affect the function of the immune cells, the hemocytes. The effects were Tamoxifen-sensitive and were mediated by rapid modulation of kinase-mediated transduction pathways. In this work we compared the in vitro effects of individual estrogenic chemicals (E2, EE: 17alpha-ethynyl estradiol; MES: mestranol; NP: nonylphenol; NP1EC: nonylphenol monoethoxylate carboxylate; BPA: bisphenol A; BP: benzophenone) on hemocyte parameters: lysosomal membrane stability (LMS), phagocytosis, lysozyme release. LMS was the most sensitive effect parameter, showing a decreasing trend at increasing concentrations of estrogens. EC50 values obtained from LMS data were utilized to calculate the estradiol equivalency factor (EEF) for each compound; these EEFs allowed for an estimation of the estrogenic potential of a synthetic mixture with a composition very similar to that previously found in waters of the Venice lagoon. Concentrated mixtures significantly affected hemocyte parameters in vitro and the effects were prevented by Tamoxifen. Significant effects of the mixture were also observed in vivo, at longer exposure times and at concentrations comparable with environmental exposure levels. The results indicate that Mytilus immune parameters can be suitably utilized to evaluate the estrogenic potential of environmental samples.

  4. Enhancement of nucleate pool boiling heat transfer to dilute binary mixtures using endothermic chemical reactions around the smoothed horizontal cylinder

    NASA Astrophysics Data System (ADS)

    Sarafraz, M. M.; Peyghambarzadeh, S. M.; Alavifazel, S. A.

    2012-10-01

    Experimental studies on enhancing the pool boiling heat transfer coefficient of binary dilute mixtures of water/glycerol, water/MEG (Mono-ethylene glycol) and water/DEG (di-ethylene glycol) have been carried out. Some particular endothermic chemical reactions related to ammonium salts were used to enhance the pool boiling heat transfer coefficient, simultaneously with occurrence of pool boiling heat transfer. Accordingly, 100 g of Ammonium nitrate, ammonium perborate and Ammonium sulfate were selected to dissolve into mixtures. High and extreme solution enthalpies of each of these ammonium salt powders are employed to reduce the surface temperature around the horizontal cylinder locally. Results demonstrated that presence of ammonium salts into the mixtures deteriorates the surface temperature of cylinder and as the result, higher pool boiling heat transfer coefficient is reported for tested solutions. Results are also reported and compared for different ammonium salts to find the influence of inducing different enthalpies of solution on pool boiling heat transfer coefficient. Obtained results also indicated that presence of endothermic reaction besides the pool boiling heat transfer enhances the heat transfer coefficients in comparison with nucleate pool boiling phenomenon solely.

  5. 40 CFR 720.38 - Exemptions for test marketing.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Exemptions for test marketing. 720.38... CONTROL ACT PREMANUFACTURE NOTIFICATION Applicability § 720.38 Exemptions for test marketing. (a) Any person may apply for an exemption to manufacture or import a new chemical substance for test marketing...

  6. 40 CFR 720.38 - Exemptions for test marketing.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Exemptions for test marketing. 720.38... CONTROL ACT PREMANUFACTURE NOTIFICATION Applicability § 720.38 Exemptions for test marketing. (a) Any person may apply for an exemption to manufacture or import a new chemical substance for test marketing...

  7. 40 CFR 720.38 - Exemptions for test marketing.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Exemptions for test marketing. 720.38... CONTROL ACT PREMANUFACTURE NOTIFICATION Applicability § 720.38 Exemptions for test marketing. (a) Any person may apply for an exemption to manufacture or import a new chemical substance for test...

  8. 40 CFR 720.38 - Exemptions for test marketing.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Exemptions for test marketing. 720.38... CONTROL ACT PREMANUFACTURE NOTIFICATION Applicability § 720.38 Exemptions for test marketing. (a) Any person may apply for an exemption to manufacture or import a new chemical substance for test...

  9. 40 CFR 720.38 - Exemptions for test marketing.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Exemptions for test marketing. 720.38... CONTROL ACT PREMANUFACTURE NOTIFICATION Applicability § 720.38 Exemptions for test marketing. (a) Any person may apply for an exemption to manufacture or import a new chemical substance for test...

  10. Evaluation of the COSHH Essentials Model with a Mixture of Organic Chemicals at a Medium-Sized Paint Producer

    PubMed Central

    Lee, Eun Gyung; Slaven, James; Bowen, Russell B.; Harper, Martin

    2011-01-01

    The Control of Substances Hazardous to Health (COSHH) Essentials model was evaluated using full-shift exposure measurements of five chemical components in a mixture [acetone, ethylbenzene, methyl ethyl ketone, toluene, and xylenes] at a medium-sized plant producing paint materials. Two tasks, batch-making and bucket-washing, were examined. Varying levels of control were already established in both tasks and the average exposures of individual chemicals were considerably lower than the regulatory and advisory 8-h standards. The average exposure fractions using the additive mixture formula were also less than unity (batch-making: 0.25, bucket-washing: 0.56) indicating the mixture of chemicals did not exceed the combined occupational exposure limit (OEL). The paper version of the COSHH Essentials model was used to calculate a predicted exposure range (PER) for each chemical according to different levels of control. The estimated PERs of the tested chemicals for both tasks did not show consistent agreement with exposure measurements when the comparison was made for each control method and this is believed to be because of the considerably different volatilities of the chemicals. Given the combination of health hazard and exposure potential components, the COSHH Essentials model recommended a control approach ‘special advice’ for both tasks, based on the potential reproductive hazard ascribed to toluene. This would not have been the same conclusion if some other chemical had been substituted (for example styrene, which has the same threshold limit value as toluene). Nevertheless, it was special advice, which had led to the combination of hygienic procedures in place at this plant. The probability of the combined exposure fractions exceeding unity was 0.0002 for the batch-making task indicating that the employees performing this task were most likely well protected below the OELs. Although the employees involved in the bucket-washing task had greater potential to

  11. The potential for chemical mixtures from the environment to enable the cancer hallmark of sustained proliferative signalling

    PubMed Central

    Engström, Wilhelm; Darbre, Philippa; Eriksson, Staffan; Gulliver, Linda; Hultman, Tove; Karamouzis, Michalis V.; Klaunig, James E.; Mehta, Rekha; Moorwood, Kim; Sanderson, Thomas; Sone, Hideko; Vadgama, Pankaj; Wagemaker, Gerard; Ward, Andrew; Singh, Neetu; Al-Mulla, Fahd; Al-Temaimi, Rabeah; Amedei, Amedeo; Colacci, Anna Maria; Vaccari, Monica; Mondello, Chiara; Scovassi, A. Ivana; Raju, Jayadev; Hamid, Roslida A.; Memeo, Lorenzo; Forte, Stefano; Roy, Rabindra; Woodrick, Jordan; Salem, Hosni K.; Ryan, Elizabeth; Brown, Dustin G.; Bisson, William H.

    2015-01-01

    The aim of this work is to review current knowledge relating the established cancer hallmark, sustained cell proliferation to the existence of chemicals present as low dose mixtures in the environment. Normal cell proliferation is under tight control, i.e. cells respond to a signal to proliferate, and although most cells continue to proliferate into adult life, the multiplication ceases once the stimulatory signal disappears or if the cells are exposed to growth inhibitory signals. Under such circumstances, normal cells remain quiescent until they are stimulated to resume further proliferation. In contrast, tumour cells are unable to halt proliferation, either when subjected to growth inhibitory signals or in the absence of growth stimulatory signals. Environmental chemicals with carcinogenic potential may cause sustained cell proliferation by interfering with some cell proliferation control mechanisms committing cells to an indefinite proliferative span. PMID:26106143

  12. Development of a priority list of chemical mixtures occurring at 1188 hazardous waste sites, using the HazDat database.

    PubMed

    Fay, R M; Mumtaz, M M

    1996-01-01

    Under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA or Superfund) section 104 mandate, as amended by the Superfund Amendments and Reauthorization Act (SARA) of 1986 USC 9604 (i)(2), the Agency for Toxic Substances and Disease Registry (ATSDR) is to identify individual substances and combinations of substances that pose the greatest public health hazard at hazardous waste sites. This has led to certain mandated activities of the Agency, including development of toxicological profiles, identification of data gaps, and, ultimately, establishment of a research agenda. The Agency has also developed HazDat, a database that captures pertinent information from public health assessments conducted at hazardous waste sites. As a preliminary step, data from sites have been analysed to identify the combinations of chemicals found in various environmental media. The most frequently found combinations were perchloroethylene (PERC) and trichloroethylene (TCE) in water (23.5% of sites); chromium (Cr) and lead (Pb) in soil (20.5%); benzene and toluene in air (3.5%); PERC, 1,1,1-trichloroethane (1,1,1-TCA) and TCE in water (11.6%); Cr, cadmium (Cd) and Pb in soil (12.0%); and benzene, PERC and TCE in air (2.2%). The findings of this analysis can be enhanced by factoring into the algorithm paramenters such as toxicity, source contribution, and likelihood of human exposure similar to that used for the Agency's priority list of 275 single substances. Assessment of the impact of chemical mixtures on human health is a formidable task, and estimating the toxicity of such mixtures, including the role of chemical interactions, is an equally demanding challenge. Because limited experimental data exist for chemical interactions, alternative methods such as predictive approaches and in vitro techniques are needed to address the many substances and their potential combinations.

  13. THYROID DISRUPTING CHEMICALS: CHALLENGES IN ASSESSING NEUROTOXIC RISK FROM ENVIRONMENTAL MIXTURES.

    EPA Science Inventory

    Environmental contaminants are known to act as thyroid disrupting chemicals (TDCs). Broadly defined, TDCs are xenobiotics that alter the structure or function of the thyroid gland, alter regulatory enzymes associated with thyroid hormone (TH) homeostasis, or change circulating o...

  14. THYROID DISRUPTING CHEMICALS: CHALLENGES IN ASSESSING NEUROTOXIC RISK FROM ENVIRONMENTAL MIXTURES.

    EPA Science Inventory

    Environmental contaminants are known to act as thyroid disrupting chemicals (TDCs). Broadly defined, TDCs are xenobiotics that alter the structure or function of the thyroid gland, alter regulatory enzymes associated with thyroid hormone (TH) homeostasis, or change circulating o...

  15. Chemical evaluation of nutrient supply from fly ash-biosolids mixtures

    SciTech Connect

    Schumann, A.W.; Sumner, M.E.

    2000-02-01

    Prediction of plant nutrient supply from fly ash and biosolids (sewage sludge and poultry manure) may enhance their agricultural use as crop fertilizer. Two mild extraction methods (42-d equilibration with ion-exchange resins; 2-d equilibration with pH 4.8 buffered nutrient solution) and analysis of nutrient data by the Diagnosis and Recommendation Integrated System (DRIS) were tested with 29 fly ash samples, four biosolids samples, and their mixtures. The resin method was useful for major nutrient (N, P, K, Ca, Mg, S) extraction from fly ashes and organic materials, particularly where mineralizable fractions of N and P under aerobic conditions are required. However, resins were inefficient in extracting P from high-Fe sewage sludges because organic waste samples caused premature failure of semipermeable membranes and fouling of resins. Extraction of fly ash with dilute buffered nutrient solution was more successful because micronutrient recovery was improved, major nutrients were correlated to the resin method, both addition and removal of nutrients were recorded. DRIS analysis was possible, and equilibration was rapid (2 d). The overall nutrient supply from these extremely variable fly ashes was: Cu = Fe {approx} B {approx} Mo > Ca > S > Zn >> Mn > N > Mg > P > K (high micronutrient, low major nutrient supply). For biosolids, the major nutrients ranked: P > N {approx} Ca > S > Mg > K (sewage sludges), and N > Ca {approx} K > P > Mg > S (poultry manures). In mixtures of fly ash with 26% sewage sludge the order was: Ca > S > N > Mg > P > K, while in mixtures of fly ash and 13% poultry manure, the nutrients ranked: Ca > K {approx} N {approx} S > Mg > P. Optimal plant nutrition (especially N-P-K balancing) should be possible by mixing these three waste materials.

  16. 40 CFR 180.1240 - Thymol; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions... exemptions from the requirement of a tolerance are established for residues of thymol on honey and honeycomb in connection with use of the pesticide under section 18 emergency exemptions granted by the...

  17. 40 CFR 180.1240 - Thymol; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions... exemptions from the requirement of a tolerance are established for residues of thymol on honey and honeycomb in connection with use of the pesticide under section 18 emergency exemptions granted by the...

  18. Dispelling urban myths about default uncertainty factors in chemical risk assessment – sufficient protection against mixture effects?

    PubMed Central

    2013-01-01

    Assessing the detrimental health effects of chemicals requires the extrapolation of experimental data in animals to human populations. This is achieved by applying a default uncertainty factor of 100 to doses not found to be associated with observable effects in laboratory animals. It is commonly assumed that the toxicokinetic and toxicodynamic sub-components of this default uncertainty factor represent worst-case scenarios and that the multiplication of those components yields conservative estimates of safe levels for humans. It is sometimes claimed that this conservatism also offers adequate protection from mixture effects. By analysing the evolution of uncertainty factors from a historical perspective, we expose that the default factor and its sub-components are intended to represent adequate rather than worst-case scenarios. The intention of using assessment factors for mixture effects was abandoned thirty years ago. It is also often ignored that the conservatism (or otherwise) of uncertainty factors can only be considered in relation to a defined level of protection. A protection equivalent to an effect magnitude of 0.001-0.0001% over background incidence is generally considered acceptable. However, it is impossible to say whether this level of protection is in fact realised with the tolerable doses that are derived by employing uncertainty factors. Accordingly, it is difficult to assess whether uncertainty factors overestimate or underestimate the sensitivity differences in human populations. It is also often not appreciated that the outcome of probabilistic approaches to the multiplication of sub-factors is dependent on the choice of probability distributions. Therefore, the idea that default uncertainty factors are overly conservative worst-case scenarios which can account both for the lack of statistical power in animal experiments and protect against potential mixture effects is ill-founded. We contend that precautionary regulation should provide an

  19. Chemical and physical effects induced by heavy cosmic ray analogues on frozen methanol and water ice mixtures

    NASA Astrophysics Data System (ADS)

    de Barros, A. L. F.; da Silveira, E. F.; Rothard, H.; Langlinay, T.; Boduch, P.

    2014-09-01

    The chemical and physical effects induced by fast heavy-ion irradiation on a frozen mixture of methanol (CH3OH) and water (H2O) at 15 K are analysed. The laboratory experiment described here simulates the energy transfer processes that occur when cosmic rays bombard this particular ice mixture and helps to elucidate the understanding of the radiolysis of ices occurring in interstellar medium grains, at the surfaces of comets, and on icy Solar system bodies. Infrared spectroscopy (FTIR) was used before and during irradiation with a 40 MeV 58Ni11+ ion beam to determine the variation of the main absorption bands of methanol, water and products. In particular, the radiolysis of CH3OH:H2O (1:1) mixture leads to the formation of H2CO, CH4, CO, CO2, HCO and HCOOCH3. Their formation and dissociation cross-sections are determined. H2CO, CH4 and HCOOCH3 molecules have relatively high destruction cross-sections of around 9 × 10-13 cm2. Furthermore, atomic carbon, oxygen and hydrogen budgets are determined and used to verify the stoichiometry of the most abundant molecular species formed. Temperature effects are compared with irradiation effects, and the spectra of samples warmed-up to different temperatures are compared with those of the irradiated CH3OH:H2O mixtures. As an astrophysical application, the CH3OH:H2O dissociation cross-sections due to other ion beam projectiles and energies are predicted assuming validity of the Se3/2 power law; calculation of the integrated dissociation rates confirms the importance of nickel and some other heavy-ion constituents of cosmic rays in astrochemistry.

  20. Endocrine-disrupting chemicals and oil and natural gas operations: Potential environmental contamination and recommendations to assess complex environmental mixtures

    USGS Publications Warehouse

    Kassotis, Christopher D.; Tillitt, Donald E.; Lin, Chung-Ho; McElroy, Jane A.; Nagel, Susan C.

    2016-01-01

    Background: Hydraulic fracturing technologies, developed over the last 65 years, have only recently been combined with horizontal drilling to unlock oil and gas reserves previously deemed inaccessible. While these technologies have dramatically increased domestic oil and natural gas production, they have also raised concerns for the potential contamination of local water supplies with the approximately 1,000 chemicals used throughout the process, including many known or suspected endocrine-disrupting chemicals.Objectives: We discuss the need for an endocrine component to health assessments for drilling-dense regions in the context of hormonal and anti-hormonal activities for chemicals used.Methods: We discuss the literature on 1) surface and ground water contamination by oil and gas extraction operations, and 2) potential human exposure, particularly in context of the total hormonal and anti-hormonal activities present in surface and ground water from natural and anthropogenic sources, with initial analytical results and critical knowledge gaps discussed.Discussion: In light of the potential for environmental release of oil and gas chemicals that can disrupt hormone receptor systems, we recommend methods for assessing complex hormonally active environmental mixtures.Conclusions: We describe a need for an endocrine-centric component for overall health assessments and provide supporting information that using this may help explain reported adverse health trends as well as help develop recommendations for environmental impact assessments and monitoring programs.

  1. Endocrine-Disrupting Chemicals and Oil and Natural Gas Operations: Potential Environmental Contamination and Recommendations to Assess Complex Environmental Mixtures.

    PubMed

    Kassotis, Christopher D; Tillitt, Donald E; Lin, Chung-Ho; McElroy, Jane A; Nagel, Susan C

    2016-03-01

    Hydraulic fracturing technologies, developed over the last 65 years, have only recently been combined with horizontal drilling to unlock oil and gas reserves previously deemed inaccessible. Although these technologies have dramatically increased domestic oil and natural gas production, they have also raised concerns for the potential contamination of local water supplies with the approximately 1,000 chemicals that are used throughout the process, including many known or suspected endocrine-disrupting chemicals. We discuss the need for an endocrine component to health assessments for drilling-dense regions in the context of hormonal and antihormonal activities for chemicals used. We discuss the literature on a) surface and groundwater contamination by oil and gas extraction operations, and b) potential human exposure, particularly in the context of the total hormonal and antihormonal activities present in surface and groundwater from natural and anthropogenic sources; we also discuss initial analytical results and critical knowledge gaps. In light of the potential for environmental release of oil and gas chemicals that can disrupt hormone receptor systems, we recommend methods for assessing complex hormonally active environmental mixtures. We describe a need for an endocrine-centric component for overall health assessments and provide information supporting the idea that using such a component will help explain reported adverse health trends as well as help develop recommendations for environmental impact assessments and monitoring programs.

  2. 40 CFR 68.125 - Exemptions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 16 2013-07-01 2013-07-01 false Exemptions. 68.125 Section 68.125 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CHEMICAL ACCIDENT PREVENTION PROVISIONS Regulated Substances for Accidental Release Prevention § 68.125 Exemptions...

  3. 40 CFR 68.125 - Exemptions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 16 2014-07-01 2014-07-01 false Exemptions. 68.125 Section 68.125 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CHEMICAL ACCIDENT PREVENTION PROVISIONS Regulated Substances for Accidental Release Prevention § 68.125 Exemptions...

  4. 40 CFR 68.125 - Exemptions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 15 2010-07-01 2010-07-01 false Exemptions. 68.125 Section 68.125 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CHEMICAL ACCIDENT PREVENTION PROVISIONS Regulated Substances for Accidental Release Prevention § 68.125 Exemptions...

  5. 40 CFR 68.125 - Exemptions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 15 2011-07-01 2011-07-01 false Exemptions. 68.125 Section 68.125 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CHEMICAL ACCIDENT PREVENTION PROVISIONS Regulated Substances for Accidental Release Prevention § 68.125 Exemptions...

  6. 40 CFR 68.125 - Exemptions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 16 2012-07-01 2012-07-01 false Exemptions. 68.125 Section 68.125 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CHEMICAL ACCIDENT PREVENTION PROVISIONS Regulated Substances for Accidental Release Prevention § 68.125 Exemptions...

  7. Chemical immobilization of raccoons (Procyon lotor) with ketamine-medetomidine mixture and reversal with atipamezole.

    PubMed

    Robert, Karine; Garant, Dany; Pelletier, Fanie

    2012-01-01

    Safe and reliable capture techniques for wild animals are important for ecologic studies and management operations. We assessed the efficiency of ketamine-medetomidine (K:M) injection and reversal with atipamezole. We anesthetized 67 raccoons (Procyon lotor; 34 males, 33 females) 103 times (individuals captured between one and five times) from April 2009-October 2010 in Mont-Orford Provincial Park, Quebec, Canada. We administered a 1:1 mixture by volume of ketamine and medetomidine by intramuscular injection. Mean (±SD) induction times for males and females were 6.1±2.8 and 6.6±3.7 min, respectively. Mean induction time was 2 min longer for juveniles than for adults (7.8±3.9 and 5.8±2.9 min, respectively) and longer in autumn than in spring for adults (7.7±3.8 and 5.4±2.9 min, respectively). Recovery time after administration of atipamezole was 9.6±3.8 and 8.4±4.4 min for males and females, respectively. Recovery time was longer in spring than in autumn (10.2±4 and 7.4±3.8 min, respectively) for adults. Induction time increased by 166% after five captures of the same individual. Immobilization did not affect body mass, adult survival, or female reproductive success. We suggest the K:M mixture used is a safe and reliable method for anesthetizing raccoons in field conditions.

  8. Use of Chemical Mixtures to Differentiate Mechanisms of Endocrine Action in a Small Fish Model

    EPA Science Inventory

    Various assays with adult fish have been developed to identify potential endocrine-disrupting chemicals (EDCs) which may cause toxicity via alterations in the hypothalamic-pituitary-gonadal (HPG) axis via different mechanisms/modes of action (MOA). These assays can be sensitive ...

  9. Bench-Scale Evaluation Of Chemically Bonded Phosphate Ceramic Technology To Stabilize Mercury Waste Mixtures

    EPA Science Inventory

    This bench-scale study was conducted to evaluate the stabilization of mercury (Hg) and mercuric chloride-containing surrogate test materials by the chemically bonded phosphate ceramics technology. This study was performed as part of a U.S. EPA program to evaluate treatment and d...

  10. Use of Chemical Mixtures to Differentiate Mechanisms of Endocrine Action in a Small Fish Model

    EPA Science Inventory

    Antagonism of the androgen receptor (AR) is an environmentally-relevant mechanism through which the hypothalamic-pituitary-gonadal (HPG) axis of fish can be affected. However, there are few in vivo tests specific for the detection of chemicals that act as AR antagonists. In this ...

  11. Use of Chemical Mixtures to Differentiate Mechanisms of Endocrine Action in a Small Fish Model

    EPA Science Inventory

    Various assays with adult fish have been developed to identify potential endocrine-disrupting chemicals (EDCs) which may cause toxicity via alterations in the hypothalamic-pituitary-gonadal (HPG) axis via different mechanisms/modes of action (MOA). These assays can be sensitive ...

  12. Bench-Scale Evaluation Of Chemically Bonded Phosphate Ceramic Technology To Stabilize Mercury Waste Mixtures

    EPA Science Inventory

    This bench-scale study was conducted to evaluate the stabilization of mercury (Hg) and mercuric chloride-containing surrogate test materials by the chemically bonded phosphate ceramics technology. This study was performed as part of a U.S. EPA program to evaluate treatment and d...

  13. 40 CFR 799.5025 - Testing consent orders for mixtures without Chemical Abstracts Service Registry Numbers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (branched and linear isomers), CAS No. 111381-91-0) ......do Do. Fluoropolymer composite substance: (1) For Dry Non-Melt Resin containing the following chemical substances as specified in the ECA: (i) Ethene...- -, polymer with tetrafluoroethene, CAS No. 26655-00-5 ......do Do. (2) For Dry Melt Fluoropolymer Resin...

  14. Investigation of shock-induced and shock-assisted chemical reactions in molybdenum-silicon powder mixtures

    NASA Astrophysics Data System (ADS)

    Vandersall, Kevin Stewart

    1999-10-01

    In this research, chemical reactions occurring in molybdenum and silicon powder mixtures under "shock-induced" (those occurring during the high-pressure shock state) and "shock-assisted" (those occurring subsequent to the shock event, but due to bulk temperature increases) conditions were investigated. Differences in the densities and yield strengths of the two constituents, in addition to the large heat of reaction associated with molybdenum disilicide (MoSi2) formation can lead to shock-induced as well as shock-assisted reactions, which make this an ideal system to delineate the kinetics and mechanisms of reactions occurring in shock-compressed powder mixtures. Shock recovery experiments performed on Mo + 2 Si powder mixtures employing cylindrical implosion geometry showed thermally initiated reactions. A mixed phase eutectic type microstructure of MoSi2 and Mo 5Si3, resulting from reaction occurring due to melting of both reactants, was observed in axial regions of the cylindrical compacts. In regions surrounding the mach stem, melting of only silicon and reaction occurring via dissolution and re-precipitation forming MoSi2 spherules surrounding molybdenum particles in a melted and solidified silicon matrix was observed. The planar pressure shock recovery geometry showed a single phase MoSi2, microstructure formed due to a solid-state pressure-induced reaction process. The time-resolved instrumented experiments were performed using a single stage gas gun in the velocity range of 500 m/s to 1 km/s, and employed poly-vinyl di-flouride (PVDF) stress gauges placed at the front and rear surfaces of the powder to determine the crush strength, densification history, and reaction initiation threshold conditions. Time-resolved experiments performed on ˜58% dense Mo + 2 Si powder mixtures at input stresses less than 4 GPa, showed characteristics of powder densification and dispersed propagated wave stress profiles with rise time >˜40 nanoseconds. At input stress between

  15. Exploring the plasma chemistry in microwave chemical vapor deposition of diamond from C/H/O gas mixtures.

    PubMed

    Kelly, Mark W; Richley, James C; Western, Colin M; Ashfold, Michael N R; Mankelevich, Yuri A

    2012-09-27

    Microwave (MW)-activated CH(4)/CO(2)/H(2) gas mixtures operating under conditions relevant to diamond chemical vapor deposition (i.e., X(C/Σ) = X(elem)(C)/(X(elem)(C) + X(elem)(O)) ≈ 0.5, H(2) mole fraction = 0.3, pressure, p = 150 Torr, and input power, P = 1 kW) have been explored in detail by a combination of spatially resolved absorption measurements (of CH, C(2)(a), and OH radicals and H(n = 2) atoms) within the hot plasma region and companion 2-dimensional modeling of the plasma. CO and H(2) are identified as the dominant species in the plasma core. The lower thermal conductivity of such a mixture (cf. the H(2)-rich plasmas used in most diamond chemical vapor deposition) accounts for the finding that CH(4)/CO(2)/H(2) plasmas can yield similar maximal gas temperatures and diamond growth rates at lower input powers than traditional CH(4)/H(2) plasmas. The plasma chemistry and composition is seen to switch upon changing from oxygen-rich (X(C/Σ) < 0.5) to carbon-rich (X(C/Σ) > 0.5) source gas mixtures and, by comparing CH(4)/CO(2)/H(2) (X(C/Σ) = 0.5) and CO/H(2) plasmas, to be sensitive to the choice of source gas (by virtue of the different prevailing gas activation mechanisms), in contrast to C/H process gas mixtures. CH(3) radicals are identified as the most abundant C(1)H(x) [x = 0-3] species near the growing diamond surface within the process window for successful diamond growth (X(C/Σ) ≈ 0.5-0.54) identified by Bachmann et al. (Diamond Relat. Mater.1991, 1, 1). This, and the findings of similar maximal gas temperatures (T(gas) ~2800-3000 K) and H atom mole fractions (X(H)~5-10%) to those found in MW-activated C/H plasmas, points to the prevalence of similar CH(3) radical based diamond growth mechanisms in both C/H and C/H/O plasmas.

  16. Induction of micronuclei on Greek hairdressers occupationally exposed to chemical mixtures.

    PubMed

    Vlastos, Dimitris; Ntinopoulos, Alexandros

    2011-10-01

    Since the early 20th century, hairdressers (HD) have been exposed to a wide range of harmful chemical products. To determine the possible genetic damage to HD, as a result of their occupational exposure to combinations of different chemical factors, we applied the micronucleus assay on their peripheral blood lymphocytes cultures. The micronucleus assay was performed on blood samples from 20 Greek female HD and 20 control women, having no connection with the occupation, from the same area. In the results analysis, parameters included were age, smoking habits, and duration of occupational exposure. The results of our study showed a significant increase in HD micronuclei (MN) frequency, compared to the controls (13.4 ± 1.00 vs. 8.05 ± 0.65). The frequency of large-size MN was significantly higher in the HD and presented potential correlation with the phenomenon of aneuploidy. A statistically significant difference in the frequency of MN between HD and controls who smoked was observed, while this was not the case with the non smoker groups. However, multiple regression analysis showed no significant correlation between smoking habits and MN frequency. The observed increase of the frequency of MN in HD is attributed to the long-term occupational exposure of HD in combination with different chemical factors. Since in the literature there are very few similar studies, further combined studies are suggested on a larger number of HD from different countries, combining biological and molecular techniques, as well as chemical analytical methods of determining and tracing the chemical factors in both the occupational environment and their organisms.

  17. Characterization of plastic deformation and chemical reaction in titanium-polytetrafluoroethylene mixture

    NASA Astrophysics Data System (ADS)

    Davis, Jeffery Jon

    1998-09-01

    The subject of this dissertation is the deformation process of a single metal - polymer system (titanium - polytetrafluoroethylene) and how this process leads to initiation of chemical reaction. Several different kinds of experiments were performed to characterize the behavior of this material to shock and impact. These mechanical conditions induce a rapid plastic deformation of the sample. All of the samples tested had an initial porosity which increased the plastic flow condition. It is currently believed that during the deformation process two important conditions occur: removal of the oxide layer from the metal and decomposition of the polymer. These conditions allow for rapid chemical reaction. The research from this dissertation has provided insight into the complex behavior of plastic deformation and chemical reactions in titanium - polytetrafluoroethylene (PTFE, Teflon). A hydrodynamic computational code was used to model the plastic flow for correlation with the results from the experiments. The results from this work are being used to develop an ignition and growth model for metal/polymer systems. Three sets of experiments were used to examine deformation of the 80% Ti and 20% Teflon materials: drop- weight, gas gun, and split-Hopkinson pressure bar. Recovery studies included post shot analysis of the samples using x-ray diffraction. Lagrangian hydrocode DYNA2D modeling of the drop-weight tests was performed for comparison with experiments. One of the reactions know to occur is Ti + C → TiC (s) which results in an exothermic release. However, the believed initial reactions occur between Ti and fluorine which produces TixFy gases. The thermochemical code CHEETAH was used to investigate the detonation products and concentrations possible during Ti - Teflon reaction. CHEETAH shows that the Ti - fluorine reactions are thermodynamically favorable. This research represents the most comprehensive to date study of deformation induced chemical reaction in metal/polymers.

  18. Long-term presence of tree species but not chemical diversity affect litter mixture effects on decomposition in a neotropical rainforest.

    PubMed

    Barantal, Sandra; Roy, Jacques; Fromin, Nathalie; Schimann, Heidy; Hättenschwiler, Stephan

    2011-09-01

    Plant litter diversity effects on decomposition rates are frequently reported, but with a strong bias towards temperate ecosystems. Altered decomposition and nutrient recycling with changing litter diversity may be particularly important in tree species-rich tropical rainforests on nutrient-poor soils. Using 28 different mixtures of leaf litter from 16 Amazonian rainforest tree species, we tested the hypothesis that litter mixture effects on decomposition increase with increasing functional litter diversity. Litter mixtures and all single litter species were exposed in the field for 9 months using custom-made microcosms with soil fauna access. In order to test the hypothesis that the long-term presence of tree species contributing to the litter mixtures increases mixture effects on decomposition, microcosms were installed in a plantation at sites including the respective tree species composition and in a nearby natural forest where these tree species are absent. We found that mixture decomposition deviated from predictions based on single species, with predominantly synergistic effects. Functional litter diversity, defined as either richness, evenness, or divergence based on a wide range of chemical traits, did not explain the observed litter mixture effects. However, synergistic effects in litter mixtures increased with the long-term presence of tree species contributing to these mixtures as the home field advantage hypothesis assumes. Our data suggest that complementarity effects on mixed litter decomposition may emerge through long-term interactions between aboveground and belowground biota.

  19. Quantitative structure-activity relationships and mixture toxicity of organic chemicals in Photobacterium phosphoreum: the Microtox test

    SciTech Connect

    Hermens, J.; Busser, F.; Leeuwangh, P.; Musch, A.

    1985-02-01

    Quantitative structure-activity relationships were calculated for the inhibition of bioluminescence of Photobacterium phosphoreum by 22 nonreactive organic chemicals. The inhibition was measured using the Microtox test and correlated with the partition coefficient between n-octanol and water (Poct), molar refractivity (MR), and molar volume (MW/d). At log Poct less than 1 and greater than 3, deviations from linearity were observed. Introduction of MR and MW/d improved the quality of the relationships. The influences of MR or MW/d may be related with an interaction of the tested chemicals to the enzyme system which produces the light emission. The sensitivity of the Microtox test to the 22 tested compounds is comparable to a 14-day acute mortality test with guppies for chemicals with log Poct less than 4. The inhibition of bioluminescence by a mixture of the tested compounds was slightly less than was expected in case of concentration addition. The Microtox test can give a good estimate of the total aspecific minimum toxicity of polluted waters. When rather lipophilic compounds or pollutants with more specific modes of action are present, this test will underestimate the toxicity to other aquatic life.

  20. 40 CFR 180.1023 - Propanoic acid; exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Propanoic acid; exemptions from the... Exemptions From Tolerances § 180.1023 Propanoic acid; exemptions from the requirement of a tolerance. (a) Postharvest application of propanoic acid or a mixture of methylene bispropionate and oxy(bismethylene...

  1. 40 CFR 180.1023 - Propanoic acid; exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Propanoic acid; exemptions from the... Exemptions From Tolerances § 180.1023 Propanoic acid; exemptions from the requirement of a tolerance. (a) Postharvest application of propanoic acid or a mixture of methylene bispropionate and oxy(bismethylene...

  2. 40 CFR 180.1023 - Propanoic acid; exemptions from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Propanoic acid; exemptions from the... Exemptions From Tolerances § 180.1023 Propanoic acid; exemptions from the requirement of a tolerance. (a) Postharvest application of propanoic acid or a mixture of methylene bispropionate and oxy(bismethylene...

  3. 21 CFR 1308.33 - Exemption of certain anabolic steroid products; application.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Exemption of certain anabolic steroid products... SCHEDULES OF CONTROLLED SUBSTANCES Exempt Anabolic Steroid Products § 1308.33 Exemption of certain anabolic... compound, mixture, or preparation containing an anabolic steroid as defined in part 1300 of this chapter...

  4. BEHAVIOR OF SURFACTANT MIXTURES AT SOLID/LIQUID AND OIL/LIQUID INTERFACES IN CHEMICAL FLOODING SYSTEMS

    SciTech Connect

    Prof. P. Somasundaran

    2003-03-31

    The aim of the project is to develop a knowledge base to help with the design of enhanced process for mobilizing and extracting untrapped oil. We emphasize on evaluating novel surfactant mixtures and on obtaining optimum combinations of the surfactants in chemical flooding EOR process. An understanding of the micellar shape and size is crucial since these physical properties directly determine the crude oil removal efficiency. Analytical ultracentrifugation experiments were used to test the multi-micelle model proposed earlier and formulate the relationships between mixed micelle formation and the surfactant structure. Information on partial specific volume of surfactants and their mixtures is required to treat analytical ultracentrifuge data. In the last report, it was noted that the partial specific volumes of the sugar-based surfactants obtained experimentally did not agree with those from theoretical calculations. A scrutiny of partial specific volumes of the four sugar-based surfactants revealed that conformational changes upon micelle formation are responsible for the large deviation. From sedimentation equilibrium experiments, two types of micelles were identified for the nonionic polyethylene surfactant and its mixtures with the sugar-based surfactant, dodecyl maltoside. The average aggregation numbers of n-dodecyl-{beta}-D-maltoside and nonyl phenol ethoxylated decyl ether agreed with those reported in literature using other techniques. Our study displayed, for the first time, that small micelles might coexist with large micelles at high concentrations due to unique structures of the surfactant although classical thermodynamic theory supports only one type of micelle. Initial dynamic light scattering results support the results for the same mixed surfactant system from analytical ultracentrifuge equilibrium technique. The implication of this finding lies in the fact that efficiency of oil recovery will be improved due to the large micellar size, its

  5. Adsorption of polyelectrolytes and polyelectrolytes-surfactant mixtures at surfaces: a physico-chemical approach to a cosmetic challenge.

    PubMed

    Llamas, Sara; Guzmán, Eduardo; Ortega, Francisco; Baghdadli, Nawel; Cazeneuve, Colette; Rubio, Ramón G; Luengo, Gustavo S

    2015-08-01

    The use of polymer and polymer - surfactant mixtures for designing and developing textile and personal care cosmetic formulations is associated with various physico-chemical aspects, e.g. detergency and conditioning in the case of hair or wool, that determine their correct performances in preserving and improving the appearance and properties of the surface where they are applied. In this work, special attention is paid to the systems combining polycations and negatively charged surfactants. The paper introduces the hair surface and presents a comprehensive review of the adsorption properties of these systems at solid-water interfaces mimicking the negative charge and surface energy of hair. These model surfaces include mixtures of thiols that confer various charge densities to the surface. The kinetics and factors that govern the adsorption are discussed from the angle of those used in shampoos and conditioners developed by the cosmetic industry. Finally, systems able to adsorb onto negatively charged surfaces regardless of the anionic character are presented, opening new ways of depositing conditioning polymers onto keratin substrates such as hair. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. A DFT based equilibrium study of a chemical mixture Tachyhydrite and their lower hydrates for long term heat storage

    NASA Astrophysics Data System (ADS)

    Pathak, A. D.; Nedea, S. V.; Zondag, H. A.; Rindt, C. C. M.; Smeulders, D. M. J.

    2016-09-01

    Chloride based salt hydrates are promising materials for seasonal heat storage. However, hydrolysis, a side reaction, deteriorates, their cycle stability. To improve the kinetics and durability, we have investigated the optimum operating conditions of a chemical mixture of CaCl2 and MgCl2 hydrates. In this study, we apply a GGA-DFT to gain insight into the various hydrates of CaMg2Cl6. We have obtained the structural properties, atomic charges and vibrational frequencies of CaMg2Cl6 hydrates. The entropic contribution and the enthalpy change are quantified from ground state energy and harmonic frequencies. Subsequently, the change in the Gibbs free energy of thermolysis was obtained under a wide range of temperature and pressure. The equilibrium product concentration of thermolysis can be used to design the seasonal heat storage system under different operating conditions.

  7. Detection and identification of a water mixture of E. coli cells and B. subtilis spores with Raman chemical imaging microscopy

    NASA Astrophysics Data System (ADS)

    Tripathi, Ashish; Jabbour, Rabih E.; Treado, Patrick J.; Neiss, Jason H.; Nelson, Matthew P.; Jensen, Janet L.; Snyder, A. Peter

    2007-04-01

    Raman spectroscopy is being evaluated as a candidate technology for waterborne pathogen detection and the fidelity of the Raman spectra of microorganisms with respect to their differentiation at the single cell level are investigated. Individual entities are investigated in the microscope field of view (FOV) by Raman chemical imaging microscopy (RCIM). The size of a substance was not found to cause spectral confusion when collating individual entities in the FOV by multivariate principal components (PCA) and RCIM methods. Polystyrene (PS) beads in 1-3 micron sizes were collectively grouped together by PCA. Distilled and recipe tap water matrices produced the proper identification of the PS beads throughout the FOV, and all PS beads in a FOV were grouped together by PCA. A mixture of Gram-positive Bacillus atrophaeus spores and Gram-negative E. coli cells were differentiated and distinguished by RCIM.

  8. Sources of variation in the mutagenic potency of complex chemical mixtures based on the salmonella/microsome assay

    SciTech Connect

    Krewski, D.; Leroux, B.G.; Creason, J.; Claxton, L.

    1992-01-01

    Twenty laboratories worldwide participated in a collaborative trial sponsored by the International Program on Chemical Safety on the mutagenicity of complex mixtures as expressed in the Salmonella/microsome assay. The U.S. National Institute of Standards and Technology provided homogeneous reference samples of urban air and diesel particles and a coal tar solution to each participating laboratory, along with samples of benzo(a)pyrene and 1-nitropyrene which served as positive controls. Mutagenic potency was characterized by the slope of the initial linear component of the dose response curve. Analysis of variance revealed significant interlaboratory variation in mutagenic potency, which accounted for 57-96% of the total variance on a logarithmic scale, depending on the sample, strain and activation conditions. No significant differences were noted in the average potency reported for air and diesel particles between laboratories using soxhlet extracts and those using sonication, although there was larger interlaboratory variation for the soxhlet method.

  9. Novel process and catalytic materials for converting CO2 and H2 containing mixtures to liquid fuels and chemicals.

    PubMed

    Meiri, Nora; Dinburg, Yakov; Amoyal, Meital; Koukouliev, Viatcheslav; Nehemya, Roxana Vidruk; Landau, Miron V; Herskowitz, Moti

    2015-01-01

    Carbon dioxide and water are renewable and the most abundant feedstocks for the production of chemicals and fungible fuels. However, the current technologies for production of hydrogen from water are not competitive. Therefore, reacting carbon dioxide with hydrogen is not economically viable in the near future. Other alternatives include natural gas, biogas or biomass for the production of carbon dioxide, hydrogen and carbon monoxide mixtures that react to yield chemicals and fungible fuels. The latter process requires a high performance catalyst that enhances the reverse water-gas-shift (RWGS) reaction and Fischer-Tropsch synthesis (FTS) to higher hydrocarbons combined with an optimal reactor system. Important aspects of a novel catalyst, based on a Fe spinel and three-reactor system developed for this purpose published in our recent paper and patent, were investigated in this study. Potassium was found to be a key promoter that improves the reaction rates of the RWGS and FTS and increases the selectivity of higher hydrocarbons while producing mostly olefins. It changed the texture of the catalyst, stabilized the Fe-Al-O spinel, thus preventing decomposition into Fe3O4 and Al2O3. Potassium also increased the content of Fe5C2 while shifting Fe in the oxide and carbide phases to a more reduced state. In addition, it increased the relative exposure of carbide iron on the catalysts surface, the CO2 adsorption and the adsorption strength. A detailed kinetic model of the RWGS, FTS and methanation reactions was developed for the Fe spinel catalyst based on extensive experimental data measured over a range of operating conditions. Significant oligomerization activity of the catalyst was found. Testing the pelletized catalyst with CO2, CO and H2 mixtures over a range of operating conditions demonstrated its high productivity to higher hydrocarbons. The composition of the liquid (C5+) was found to be a function of the potassium content and the composition of the feedstock.

  10. Investigation of the shock-induced chemical reaction (SICR) in Ni + Al nanoparticle mixtures.

    PubMed

    Xiong, Yongnan; Xiao, Shifang; Deng, Huiqiu; Zhu, Wenjun; Hu, Wangyu

    2017-07-21

    Molecular dynamics (MD) simulations are used to investigate the shock-compression response of Ni + Al spherical nanoparticles arranged in a NaCl-like structure. The deformation and reaction characteristics are studied from the particle level to the atomic scale at various piston velocities. Shock-induced chemical reactions (SICRs) occur during non-equilibrium processes, accompanied by a sharp rise in temperature and rapid mixing of atoms. The preferentially deformed Al particles form a high-speed mass flow relative to the Ni at the shock front, which impinges on the Ni particles, and mixing of Ni and Al atoms occurs immediately at the interface. The particle velocity dispersion (PVD) that appears at the shock front has important implications for the initiation of shock-induced chemical reactions. We show that dislocations are mainly generated at the beginning of particle deformation or at the shock front, and do not directly affect the occurrence of SICRs. The intimate contact of the molten Al and the amorphous Ni is found to be critical to the subsequent reactions for the extensive mixing of Ni and Al. We conclude that the mechanisms of SICRs involve mechanochemical processes near the shock front and subsequent interdiffusion processes.

  11. A probe on the intermolecular forces in diisopropyl ether-n-butyric acid mixture by dielectric, FTIR studies and quantum chemical calculations.

    PubMed

    Arivazhagan, G; Shanmugam, R; Elangovan, A

    2013-03-15

    The results of FTIR spectral measurement on equimolar diisopropyl ether-butyric acid binary mixture and quantum chemical calculations on the complex molecule have been presented. Dielectric studies have been carried out on the binary mixture over the entire composition range and at four different temperatures 303 K, 308 K, 313 K and 318 K. n-Butyric acid seems to prefer less polar ether to interact with it. It appears that the usual interpretation of variation of static dielectric constant and positive deviation of excess permittivity from ideal mixture behavior needs to be relooked.

  12. General baseline toxicity QSAR for nonpolar, polar and ionisable chemicals and their mixtures in the bioluminescence inhibition assay with Aliivibrio fischeri.

    PubMed

    Escher, Beate I; Baumer, Andreas; Bittermann, Kai; Henneberger, Luise; König, Maria; Kühnert, Christin; Klüver, Nils

    2017-03-22

    The Microtox assay, a bioluminescence inhibition assay with the marine bacterium Aliivibrio fischeri, is one of the most popular bioassays for assessing the cytotoxicity of organic chemicals, mixtures and environmental samples. Most environmental chemicals act as baseline toxicants in this short-term screening assay, which is typically run with only 30 min of exposure duration. Numerous Quantitative Structure-Activity Relationships (QSARs) exist for the Microtox assay for nonpolar and polar narcosis. However, typical water pollutants, which have highly diverse structures covering a wide range of hydrophobicity and speciation from neutral to anionic and cationic, are often outside the applicability domain of these QSARs. To include all types of environmentally relevant organic pollutants we developed a general baseline toxicity QSAR using liposome-water distribution ratios as descriptors. Previous limitations in availability of experimental liposome-water partition constants were overcome by reliable prediction models based on polyparameter linear free energy relationships for neutral chemicals and the COSMOmic model for charged chemicals. With this QSAR and targeted mixture experiments we could demonstrate that ionisable chemicals fall in the applicability domain. Most investigated water pollutants acted as baseline toxicants in this bioassay, with the few outliers identified as uncouplers or reactive toxicants. The main limitation of the Microtox assay is that chemicals with a high melting point and/or high hydrophobicity were outside of the applicability domain because of their low water solubility. We quantitatively derived a solubility cut-off but also demonstrated with mixture experiments that chemicals inactive on their own can contribute to mixture toxicity, which is highly relevant for complex environmental mixtures, where these chemicals may be present at concentrations below the solubility cut-off.

  13. Specific interactions of functionalised gold surfaces with ammonium perchlorate or starch; towards a chemical cartography of their mixture

    NASA Astrophysics Data System (ADS)

    Mercier, D.; Mercader, C.; Quere, S.; Hairault, L.; Méthivier, C.; Pradier, C. M.

    2012-10-01

    By functionalising gold samples, planar wafers or AFM tips, with an acid- or an amino acid-terminated thiols, mercaptoundecanoic acid (MUA) and homocystein (H-Cyst) respectively, we were able to differentiate the interactions with ammonium perchlorate (AP) and starch (S), two components of a nanocomposition mixture. To do so, the interaction between gold functionalized surfaces and the two targeted compounds have been characterized and quantified by several complementary techniques. Polarisation modulation-infrared spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS), providing chemical analyses of gold surfaces after contacting S or AP, proved that both compounds were retained on MUA or H-Cyst-modified surfaces, but to various extents. Quartz crystal microbalance on-line measurements enabled to monitor the kinetics of interaction and showed distinct differences in the behaviour of MUA and H-Cyst-surfaces towards the two compounds. Having observed that only H-Cyst-modified surfaces enables to get a contrast on the chemical force microscopy (CFM) images, this new result could be well explained by examining the data obtained by combining the above-mentioned surface characterisation techniques.

  14. Physico-chemical and sensory properties of marmalades made from mixtures of fruits and under-exploited Andean tubers.

    PubMed

    Lotufo Haddad, Agustina M; Margalef, María Isabel; Armada, Margarita; Goldner, María Cristina

    2017-09-01

    This work studies the added value to the Andean tuber crops through the production of jams. The objective were: (1) to study the sensory and instrumental characteristics of dietetic marmalades made with fruits and Andean tubers; (2) to research consumer's acceptability and emotional responses; (3) to assess the relationship between sensory and instrumental variables and (4) to determine sensory, instrumental and emotional variables that influence the acceptability. Pearson's correlations showed that spreadability was the variable better predicted by sensory and instrumental ones. The analysis of variance showed that sourness increased with the increase of strawberry and the decrease of apple contents (P < 0.05). The acceptability increased when the strawberry proportion was higher. The sweetness-sourness balance drove the hedonic response and some emotions changed from one feeling to its corresponding opposite when the strawberry proportion reached 50 or 60. According to a partial least square 2 and a principal components analysis of sensory/acceptability/emotion data, 'typical', 'autochthonous', 'urban' and 'present' resulted in positive emotions which favored the consumer liking. Formulating marmalades with mixtures of fruits and Andean tubers will allow giving value-added to these crops. The elaboration of products using innovative raw materials will be an incentive for farmers to cultivate them. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  15. Declaration of local chemical eradication of the Argentine ant: Bayesian estimation with a multinomial-mixture model.

    PubMed

    Sakamoto, Yoshiko; Kumagai, Naoki H; Goka, Koichi

    2017-06-13

    Determining the success of eradication of an invasive species requires a way to decide when its risk of reoccurrence has become acceptably low. In Japan, the area populated by the Argentine ant, Linepithema humile (Mayr), is expanding, and eradication via chemical treatment is ongoing at various locations. One such program in Tokyo was apparently successful, because the ant population decreased to undetectable levels within a short time. However, construction of a population model for management purposes was difficult because the probability of detecting ants decreases rapidly as the population collapses. To predict the time when the ant was eradicated, we developed a multinomial-mixture model for chemical eradication based on monthly trapping data and the history of pesticide applications. We decided when to declare that eradication had been successful by considering both 'eradication' times, which we associated with eradication probabilities of 95% and 99%, and an optimal stopping time based on a 'minimum expected economic cost' that considered the possibility that surveys were stopped too soon. By applying these criteria, we retroactively declared that Argentine ants had been eradicated 38-42 months after the start of treatments (16-17 months after the last sighting).

  16. Chemical and toxicological characterization of the bricks produced from clay/sewage sludge mixture.

    PubMed

    Gerić, Marko; Gajski, Goran; Oreščanin, Višnja; Kollar, Robert; Garaj-Vrhovac, Vera

    2012-01-01

    The present study aimed to characterize chemical properties of clay bricks containing 20 % of sewage sludge. After detection of potentially hazardous metals, we simulated precipitation exposure of such material to determine the amount of heavy metals that could leach out of the bricks. Metals, such as copper, zinc, nickel, cobalt, chromium, etc., were detected in leachate in low concentrations. Moreover, human peripheral blood lymphocytes were exposed to brick leachate for 24 h in order to evaluate its possible negative impact on human cells and genome in vitro. Cytotoxicity tests showed no effect on human peripheral blood lymphocytes viability after exposure to brick's leachate. On the contrary, the alkaline comet assay showed slight but significant increase in DNA damage with all three parameters tested. As we might predict, interactions of several heavy metals in low concentrations could be responsible for DNA damaging effect. In that manner, our findings suggest that leachates from sewage sludge-produced bricks may lead to adverse effects on the exposed human population, and that more stabile bricks should be developed to minimize leaching of heavy metals into the environment. Bricks with lower percentage of the sludge may be one of the solutions to reduce the toxic effect of the final product.

  17. BEHAVIOR OF SURFACTANT MIXTURE AT SOLID/LIQUID AND OIL/LIQUID INTERFACE IN CHEMICAL FLOODING SYSTEMS

    SciTech Connect

    Prof. P. Somasundaran

    2002-03-01

    The aim of the project is to develop and evaluate efficient novel surfactant mixtures for enhanced oil recovery. Preliminary ultra-filtration tests suggest that two kinds of micelles may exist in binary surfactant mixtures at different concentrations. Due to the important role played in interfacial processes by micelles as determined by their structures, focus of the current work is on the delineation of the relationship between such aggregate structures and chemical compositions of the surfactants. A novel analytical centrifuge application is explored to generate information on structures of different surfactants aggregates. In this report, optical systems, typical output of the analytical ultracentrifuge results and four basic experiments are discussed. Initial sedimentation velocity investigations were conducted using nonyl phenol ethoxylated decyl ether (NP-10) to choose the best analytical protocol, calculate the partial specific volume and obtain information on sedimentation coefficient, aggregation mass of micelles. The partial specific volume was calculated to be 0.920. Four softwares: Optima{trademark} XL-A/XL-I data analysis software, DCDT+, Svedberg and SEDFIT, were compared for the analysis of sedimentation velocity experimental data. The sedimentation coefficient and aggregation number of NP-10 micelles obtained using the first three softwares at 25 C are 209, 127, and 111, respectively. The last one is closest to the result from Light Scattering. The reason for the differences in numbers obtained using the three softwares is discussed. Based on these tests, Svedberg and SEDFIT analysis are chosen for further studies. This approach using the analytical ultracentrifugation offers an unprecedented opportunity now to obtain important information on mixed micelles and their role in interfacial processes.

  18. BEHAVIOR OF SURFACTANT MIXTURES AT SOLID/LIQUID AND OIL/LIQUID INTERFACES IN CHEMICAL FLOODING SYSTEMS

    SciTech Connect

    P. Somasundaran

    2004-11-20

    The aim of the project is to develop a knowledge base to help the design of enhanced processes for mobilizing and extracting untrapped oil. We emphasize evaluation of novel surfactant mixtures and obtaining optimum combinations of the surfactants for efficient chemical flooding EOR processes. In this regard, an understanding of the aggregate shape, size and structure is crucial since these properties govern the crude oil removal efficiency. During the three-year period, the adsorption and aggregation behavior of sugar-based surfactants and their mixtures with other types of surfactants have been studied. Sugar-based surfactants are made from renewable resources, nontoxic and biodegradable. They are miscible with water and oil. These environmentally benign surfactants feature high surface activity, good salinity, calcium and temperature tolerance, and unique adsorption behavior. They possess the characteristics required for oil flooding surfactants and have the potential for replacing currently used surfactants in oil recovery. A novel analytical ultracentrifugation technique has been successfully employed for the first time, to characterize the aggregate species present in mixed micellar solution due to its powerful ability to separate particles based on their size and shape and monitor them simultaneously. Analytical ultracentrifugation offers an unprecedented opportunity to obtain important information on mixed micelles, structure-performance relationship for different surfactant aggregates in solution and their role in interfacial processes. Initial sedimentation velocity investigations were conducted using nonyl phenol ethoxylated decyl ether (NP-10) to choose the best analytical protocol, calculate the partial specific volume and obtain information on sedimentation coefficient, aggregation mass of micelles. Four softwares: OptimaTM XL-A/XL-I data analysis software, DCDT+, Svedberg and SEDFIT, were compared for the analysis of sedimentation velocity

  19. Design Concepts for Co-Production of Power, Fuels & Chemicals Via Coal/Biomass Mixtures

    SciTech Connect

    Rao, A. D.; Chen, Q.; Samuelsen, G. S.

    2012-09-30

    The overall goal of the program is to develop design concepts, incorporating advanced technologies in areas such as oxygen production, feed systems, gas cleanup, component separations and gas turbines, for integrated and economically viable coal and biomass fed gasification facilities equipped with carbon capture and storage for the following scenarios: (i) coproduction of power along with hydrogen, (ii) coproduction of power along with fuels, (iii) coproduction of power along with petrochemicals, and (iv) coproduction of power along with agricultural chemicals. To achieve this goal, specifically the following objectives are met in this proposed project: (i) identify advanced technology options and innovative preliminary design concepts that synergistically integrate plant subsections, (ii) develop steady state system simulations to predict plant efficiency and environmental signature, (iii) develop plant cost estimates by capacity factoring major subsystems or by major equipment items where required, and then capital, operating and maintenance cost estimates, and (iv) perform techno- economic analyses for the above described coproduction facilities. Thermal efficiencies for the electricity only cases with 90% carbon capture are 38.26% and 36.76% (HHV basis) with the bituminous and the lignite feedstocks respectively. For the coproduction cases (where 50% of the energy exported is in the form of electricity), the electrical efficiency, as expected, is highest for the hydrogen coproduction cases while lowest for the higher alcohols (ethanol) coproduction cases. The electrical efficiencies for Fischer-Tropsch coproduction cases are slightly higher than those for the methanol coproduction cases but it should be noted that the methanol (as well as the higher alcohol) coproduction cases produce the finished coproduct while the Fischer-Tropsch coproduction cases produce a coproduct that requires further processing in a refinery. The cross comparison of the thermal

  20. A unique pattern of hepatocyte proliferation in F344 rats following long-term exposures to low levels of a chemical mixture of groundwater contaminants.

    PubMed

    Constan, A A; Yang, R S; Baker, D C; Benjamin, S A

    1995-02-01

    Most exposures of humans to environmental agents involve mixtures of chemicals, rather than individual chemicals. Some chemicals can cause hepatocellular proliferation and act as neoplastic promoters. Little is known concerning hepatocellular proliferation caused by chemical mixtures such as those found in groundwater at hazardous waste sites. Therefore, a 6 month study was performed to investigate hepatocellular proliferation and histopathological changes in F344 rats after long-term, low-level exposure to a mixture of groundwater contaminants. The seven chemicals used are among the most frequently detected contaminants associated with hazardous waste sites; arsenic, benzene, chloroform, chromium, lead, phenol and trichloroethylene. Male F344 rats were exposed to this mixture, or submixtures of the organic or inorganic chemicals, via drinking water for 6 months. The study design included a time-course experiment (i.e. 3 and 10 days and 1, 3 and 6 months) and a dose-response experiment. Hepatocellular proliferation studies were performed by subcutaneously implanting osmotic mini-pumps to continuously deliver 5-bromo-2'-deoxyuridine for 7 days, which labeled nuclei of proliferating cells. In all groups, there were no differences in weight gain, body weight, liver weight ratios or liver-associated plasma enzymes. Light microscopic evaluation revealed no lesions related to the treatments in any animals. However, significant increases in hepatocellular labeling were observed at the 3 and 10 day and 1 month exposure time points after treatment with the full mixture, as well as the organic or inorganic submixtures. Proliferating hepatocytes expressed a unique labeling pattern surrounding large hepatic veins (0.5-2.0 mm), but not central veins. This did not appear to be a regenerative response due to cytotoxic mechanisms, as assessed by the absence of increased plasma enzyme activity and the absence of hepatocellular lesions.

  1. 40 CFR 180.1165 - Capsaicin; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... exempt from the requirement of a tolerance in or on all food commodities when used in accordance with approved label rates and good agricultural practice....

  2. 40 CFR 180.1165 - Capsaicin; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... exempt from the requirement of a tolerance in or on all food commodities when used in accordance with approved label rates and good agricultural practice....

  3. 40 CFR 180.1165 - Capsaicin; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... exempt from the requirement of a tolerance in or on all food commodities when used in accordance with approved label rates and good agricultural practice....

  4. 40 CFR 180.1033 - Methoprene; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... is exempt from the requirement of a tolerance in or on all food commodities when used to control insect larvae. ...

  5. 40 CFR 180.1090 - Lactic acid; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... (2-hydroxypropanoic acid) is exempted from the requirement of a tolerance when used as a plant...

  6. 40 CFR 180.1090 - Lactic acid; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... (2-hydroxypropanoic acid) is exempted from the requirement of a tolerance when used as a plant...

  7. 40 CFR 180.1090 - Lactic acid; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... (2-hydroxypropanoic acid) is exempted from the requirement of a tolerance when used as a plant...

  8. 40 CFR 180.1090 - Lactic acid; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... (2-hydroxypropanoic acid) is exempted from the requirement of a tolerance when used as a plant...

  9. 40 CFR 180.1073 - Isomate-M; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) is exempt from the requirement of a tolerance in or on all the raw agricultural commodities (food and... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN...

  10. 40 CFR 180.1259 - Reynoutria sachalinensis extract; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL... derived from the whole plant extract, are exempt from the requirement of a tolerance in or on all food...

  11. 40 CFR 180.1259 - Reynoutria sachalinensis extract; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL... derived from the whole plant extract, are exempt from the requirement of a tolerance in or on all food...

  12. 40 CFR 180.1145 - Pseudomonas syringae; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN... tolerance. Pseudomonas syringae is exempted from the requirement of a tolerance on all raw agricultural commodities when applied postharvest according to good agricultural practices....

  13. 40 CFR 180.1041 - Nosema locustae; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... insecticide Nosema locustae is exempted from the requirement of a tolerance for residues in or on all raw agricultural commodities....

  14. 40 CFR 180.1160 - Jojoba oil; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... insecticide and spray tank adjuvant jojoba oil is exempted from the requirement of a tolerance in or on...

  15. 40 CFR 180.1160 - Jojoba oil; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD... insecticide and spray tank adjuvant jojoba oil is exempted from the requirement of a tolerance in or on...

  16. 40 CFR 142.62 - Variances and exemptions from the maximum contaminant levels for organic and inorganic chemicals.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) Dibromochloropropane X X (27) 2,4-D X (28) Ethylene dibromide X X (29) Heptachlor X (30) Heptachlor epoxide X (31... for the inorganic chemicals listed in § 141.62: BAT for Inorganic Compounds Listed in §...

  17. Mixture effects at very low doses with combinations of anti-androgenic pesticides, antioxidants, industrial pollutant and chemicals used in personal care products

    SciTech Connect

    Orton, Frances; Ermler, Sibylle; Kugathas, Subramaniam; Rosivatz, Erika; Scholze, Martin; Kortenkamp, Andreas

    2014-08-01

    Many xenobiotics have been identified as in vitro androgen receptor (AR) antagonists, but information about their ability to produce combined effects at low concentrations is missing. Such data can reveal whether joint effects at the receptor are induced at low levels and may support the prioritisation of in vivo evaluations and provide orientations for the grouping of anti-androgens in cumulative risk assessment. Combinations of 30 AR antagonists from a wide range of sources and exposure routes (pesticides, antioxidants, parabens, UV-filters, synthetic musks, bisphenol-A, benzo(a)pyrene, perfluorooctane sulfonate and pentabromodiphenyl ether) were tested using a reporter gene assay (MDA-kb2). Chemicals were combined at three mixture ratios, equivalent to single components' effect concentrations that inhibit the action of dihydrotesterone by 1%, 10% or 20%. Concentration addition (CA) and independent action were used to calculate additivity expectations. We observed complete suppression of dihydrotestosterone effects when chemicals were combined at individual concentrations eliciting 1%, 10% or 20% AR antagonistic effect. Due to the large number of mixture components, the combined AR antagonistic effects occurred at very low concentrations of individual mixture components. CA slightly underestimated the combined effects at all mixture ratios. In conclusion, large numbers of AR antagonists from a wide variety of sources and exposure routes have the ability of acting together at the receptor to produce joint effects at very low concentrations. Significant mixture effects are observed when chemicals are combined at concentrations that individually do not induce observable AR antagonistic effects. Cumulative risk assessment for AR antagonists should apply grouping criteria based on effects where data are available, rather than on criteria of chemical similarity. - Highlights: • Mixtures of AR antagonists at low individual concentrations cause complete inhibition.

  18. PACKAGE (Plasma Analysis, Chemical Kinetics and Generator Efficiency): a computer program for the calculation of partial chemical equilibrium/partial chemical rate controlled composition of multiphased mixtures under one dimensional steady flow

    SciTech Connect

    Yousefian, V.; Weinberg, M.H.; Haimes, R.

    1980-02-01

    The NASA CEC Code was the starting point for PACKAGE, whose function is to evaluate the composition of a multiphase combustion product mixture under the following chemical conditions: (1) total equilibrium with pure condensed species; (2) total equilibrium with ideal liquid solution; (3) partial equilibrium/partial finite rate chemistry; and (4) fully finite rate chemistry. The last three conditions were developed to treat the evolution of complex mixtures such as coal combustion products. The thermodynamic variable pairs considered are either pressure (P) and enthalpy, P and entropy, at P and temperature. Minimization of Gibbs free energy is used. This report gives detailed discussions of formulation and input/output information used in the code. Sample problems are given. The code development, description, and current programming constraints are discussed. (DLC)

  19. Evidence from pharmacology and pathophysiology suggests that chemicals with dissimilar mechanisms of action could be of bigger concern in the toxicological risk assessment of chemical mixtures than chemicals with a similar mechanism of action.

    PubMed

    Hadrup, Niels

    2014-08-01

    Mathematical models have been developed for the toxicological risk assessment of chemical mixtures. However, exposure data as well as single chemical toxicological data are required for these models. When addressing this data need, it could be attractive to focus on chemicals with similar mechanisms of action, similar modes of action or with common target organs. In the European Union, efforts are currently being made to subgroup chemicals according to this need. However, it remains to be determined whether this is the best strategy to obtain data for risk assessment. In conditions such as cancer or HIV, it is generally recognised that pharmacological combination therapy targeting different mechanisms of action is more effective than a strategy where only one mechanism is targeted. Moreover, in diseases such as acute myocardial infarction and congestive heart failure, several organ systems concomitantly contribute to the pathophysiology, suggesting that a grouping based on common target organs may also be inefficient. A better option may be to prioritise chemicals on the basis of potency and risk of exposure. In conclusion, there are arguments to suggest that we should concomitantly consider all targets that a chemical can affect in the human body and not merely a subset.

  20. The response of the polarized Fermi mixture to an artificial vector potential: The interaction strength and imbalance chemical potential effects

    NASA Astrophysics Data System (ADS)

    Ebrahimian, N.; Safiee, Z.

    2017-03-01

    We consider a polarized Fermi mixture (with normal-superfluid phase separation), subjected to artificial vector potential. We concentrate on the BCS regime with various interaction strengths and numerically obtain the polarisability of the system. We obtain the functional dependence of the polarisability of the system on frequency and the relevant physical parameters, namely the interaction strength, the mass ratio, the average and imbalance chemical potentials. Also, we find the special frequency (ωs), for which the rate of the response of system to the potential is changed and the cut-off frequency (ωcutoff), for which the response starts to become infinity. We investigate the behavior of the curves of polarisability versus proper physical parameters for ω <ωs and ωs < ω <ωcutoff at a nonzero temperature and interpret the existence of special and cut-off frequencies via the propagator concept (of particles or holes). Also, we offer the explanation of the minimum energy required for the occurrence of the pair-breaking process and the existence of the cut-off frequency, which is different with respect to the conventional superfluid Fermi gas, and is related to the relevant physical parameters. Finally, the system's response can be controlled by relevant physical parameters, such as interaction strength.

  1. Chemical and structural analysis of enhanced biochars: thermally treated mixtures of biochar, chicken litter, clay and minerals.

    PubMed

    Lin, Y; Munroe, P; Joseph, S; Ziolkowski, A; van Zwieten, L; Kimber, S; Rust, J

    2013-03-01

    In this study biochar mixtures comprising a Jarrah-based biochar, chicken litter (CL), clay and other minerals were thermally treated, via torrefaction, at moderate temperatures (180 and 220 °C). The objectives of this treatment were to reduce N losses from CL during processing and to determine the effect of both the type of added clay and the torrefaction temperature on the structural and chemical properties of the final product, termed as an enhanced biochar (EB). Detailed characterisation indicated that the EBs contained high concentrations of plant available nutrients. Both the nutrient content and plant availability were affected by torrefaction temperature. The higher temperature (220 °C) promoted the greater decomposition of organic matter in the CL and dissociated labile carbon from the Jarrah-based biochar, which produced a higher concentration of dissolved organic carbon (DOC). This DOC may assist to solubilise mineral P, and may also react with both clay and minerals to block active sites for P adsorption. This subsequently resulted in higher concentrations of plant available P. Nitrogen loss was minimised, with up to 73% of the initial total N contained in the feedstock remaining in the final EB. However, N availability was affected by both torrefaction temperature and the nature of the clay minerals added. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Screening Estrogenic Activities of Chemicals or Mixtures In Vivo Using Transgenic (cyp19a1b-GFP) Zebrafish Embryos

    PubMed Central

    Brion, François; Le Page, Yann; Piccini, Benjamin; Cardoso, Olivier; Tong, Sok-Keng; Chung, Bon-chu; Kah, Olivier

    2012-01-01

    The tg(cyp19a1b-GFP) transgenic zebrafish expresses GFP (green fluorescent protein) under the control of the cyp19a1b gene, encoding brain aromatase. This gene has two major characteristics: (i) it is only expressed in radial glial progenitors in the brain of fish and (ii) it is exquisitely sensitive to estrogens. Based on these properties, we demonstrate that natural or synthetic hormones (alone or in binary mixture), including androgens or progestagens, and industrial chemicals induce a concentration-dependent GFP expression in radial glial progenitors. As GFP expression can be quantified by in vivo imaging, this model presents a very powerful tool to screen and characterize compounds potentially acting as estrogen mimics either directly or after metabolization by the zebrafish embryo. This study also shows that radial glial cells that act as stem cells are direct targets for a large panel of endocrine disruptors, calling for more attention regarding the impact of environmental estrogens and/or certain pharmaceuticals on brain development. Altogether these data identify this in vivo bioassay as an interesting alternative to detect estrogen mimics in hazard and risk assessment perspective. PMID:22586461

  3. Screening estrogenic activities of chemicals or mixtures in vivo using transgenic (cyp19a1b-GFP) zebrafish embryos.

    PubMed

    Brion, François; Le Page, Yann; Piccini, Benjamin; Cardoso, Olivier; Tong, Sok-Keng; Chung, Bon-chu; Kah, Olivier

    2012-01-01

    The tg(cyp19a1b-GFP) transgenic zebrafish expresses GFP (green fluorescent protein) under the control of the cyp19a1b gene, encoding brain aromatase. This gene has two major characteristics: (i) it is only expressed in radial glial progenitors in the brain of fish and (ii) it is exquisitely sensitive to estrogens. Based on these properties, we demonstrate that natural or synthetic hormones (alone or in binary mixture), including androgens or progestagens, and industrial chemicals induce a concentration-dependent GFP expression in radial glial progenitors. As GFP expression can be quantified by in vivo imaging, this model presents a very powerful tool to screen and characterize compounds potentially acting as estrogen mimics either directly or after metabolization by the zebrafish embryo. This study also shows that radial glial cells that act as stem cells are direct targets for a large panel of endocrine disruptors, calling for more attention regarding the impact of environmental estrogens and/or certain pharmaceuticals on brain development. Altogether these data identify this in vivo bioassay as an interesting alternative to detect estrogen mimics in hazard and risk assessment perspective.

  4. Recombination and chemical energy accommodation coefficients from chemical dynamics simulations: O/O2 mixtures reacting over a β-cristobalite (001) surface.

    PubMed

    Morón, Víctor; Gamallo, Pablo; Martin-Gondre, Ludovic; Crespos, Cédric; Larregaray, Pascal; Sayós, Ramón

    2011-10-21

    A microkinetic model is developed to study the reactivity of an O/O(2) gas mixture over a β-cristobalite (001) surface. The thermal rate constants for the relevant elementary processes are either inferred from quasiclassical trajectory calculations or using some statistical approaches, resting on a recently developed interpolated multidimensional potential energy surface based on density functional theory. The kinetic model predicts a large molecular coverage at temperatures lower than 1000 K, in contrary to a large atomic coverage at higher temperatures. The computed atomic oxygen recombination coefficient, mainly involving atomic adsorption and Eley-Rideal recombination, is small and increases with temperature in the 700-1700 K range (0.01 < γ(O) < 0.02) in good agreement with experiments. In the same temperature range, the estimated chemical energy accommodation coefficient, the main contribution to which is the atomic adsorption process is almost constant and differs from unity (0.75 < β(O) < 0.80). This journal is © the Owner Societies 2011

  5. Species diversity and chemical properties of litter influence non-additive effects of litter mixtures on soil carbon and nitrogen cycling.

    PubMed

    Mao, Bing; Mao, Rong; Zeng, De-Hui

    2017-01-01

    Decomposition of litter mixtures generally cannot be predicted from the component species incubated in isolation. Therefore, such non-additive effects of litter mixing on soil C and N dynamics remain poorly understood in terrestrial ecosystems. In this study, litters of Mongolian pine and three dominant understory species and soil were collected from a Mongolian pine plantation in Northeast China. In order to examine the effects of mixed-species litter on soil microbial biomass N, soil net N mineralization and soil respiration, four single litter species and their mixtures consisting of all possible 2-, 3- and 4-species combinations were added to soils, respectively. In most instances, species mixing produced synergistic non-additive effects on soil microbial biomass N and soil respiration, but antagonistic non-additive effects on net N mineralization. Species composition rather than species richness explained the non-additive effects of species mixing on soil microbial biomass N and net N mineralization, due to the interspecific differences in litter chemical composition. Both litter species composition and richness explained non-additive soil respiration responses to mixed-species litter, while litter chemical diversity and chemical composition did not. Our study indicated that litter mixtures promoted soil microbial biomass N and soil respiration, and inhibited net N mineralization. Soil N related processes rather than soil respiration were partly explained by litter chemical composition and chemical diversity, highlighting the importance of functional diversity of litter on soil N cycling.

  6. Species diversity and chemical properties of litter influence non-additive effects of litter mixtures on soil carbon and nitrogen cycling

    PubMed Central

    Mao, Bing; Mao, Rong; Zeng, De-Hui

    2017-01-01

    Decomposition of litter mixtures generally cannot be predicted from the component species incubated in isolation. Therefore, such non-additive effects of litter mixing on soil C and N dynamics remain poorly understood in terrestrial ecosystems. In this study, litters of Mongolian pine and three dominant understory species and soil were collected from a Mongolian pine plantation in Northeast China. In order to examine the effects of mixed-species litter on soil microbial biomass N, soil net N mineralization and soil respiration, four single litter species and their mixtures consisting of all possible 2-, 3- and 4-species combinations were added to soils, respectively. In most instances, species mixing produced synergistic non-additive effects on soil microbial biomass N and soil respiration, but antagonistic non-additive effects on net N mineralization. Species composition rather than species richness explained the non-additive effects of species mixing on soil microbial biomass N and net N mineralization, due to the interspecific differences in litter chemical composition. Both litter species composition and richness explained non-additive soil respiration responses to mixed-species litter, while litter chemical diversity and chemical composition did not. Our study indicated that litter mixtures promoted soil microbial biomass N and soil respiration, and inhibited net N mineralization. Soil N related processes rather than soil respiration were partly explained by litter chemical composition and chemical diversity, highlighting the importance of functional diversity of litter on soil N cycling. PMID:28686660

  7. Using molecular docking between organic chemicals and lipid membrane to revise the well known octanol-water partition coefficient of the mixture.

    PubMed

    Wang, Ting; Zhou, Xianghong; Wang, Dali; Yin, Daqiang; Lin, Zhifen

    2012-07-01

    The octanol-water partition coefficient of a mixture has been widely used to predict the baseline toxicity of non-polar narcotic chemical mixtures, since toxic effects are usually generated by multiple mixtures. However, it remains unclear whether the validity of log Kowmix can be demonstrated, because experimental methods cannot be used to determine this parameter. The invalidity and the further revision of log Kowmix were therefore studied by using molecular docking between non-polar narcotic chemicals and lipid membrane (E(binding)). The results show E(binding) is a feasible substitute parameter for log Kow because their relationship is linear. Based on a molecular docking and QSAR model, a new calculated method of log Kowmix was proposed as follows: log(Kowmix)=∑x(i)log Kowi. Comparison of this new method with the established methods demonstrates the invalidity of the latter, and therefore the former is suggested to be used to calculate the log Kowmix of organic chemical mixtures.

  8. Mixture effects at very low doses with combinations of anti-androgenic pesticides, antioxidants, industrial pollutant and chemicals used in personal care products.

    PubMed

    Orton, Frances; Ermler, Sibylle; Kugathas, Subramaniam; Rosivatz, Erika; Scholze, Martin; Kortenkamp, Andreas

    2014-08-01

    Many xenobiotics have been identified as in vitro androgen receptor (AR) antagonists, but information about their ability to produce combined effects at low concentrations is missing. Such data can reveal whether joint effects at the receptor are induced at low levels and may support the prioritisation of in vivo evaluations and provide orientations for the grouping of anti-androgens in cumulative risk assessment. Combinations of 30 AR antagonists from a wide range of sources and exposure routes (pesticides, antioxidants, parabens, UV-filters, synthetic musks, bisphenol-A, benzo(a)pyrene, perfluorooctane sulfonate and pentabromodiphenyl ether) were tested using a reporter gene assay (MDA-kb2). Chemicals were combined at three mixture ratios, equivalent to single components' effect concentrations that inhibit the action of dihydrotesterone by 1%, 10% or 20%. Concentration addition (CA) and independent action were used to calculate additivity expectations. We observed complete suppression of dihydrotestosterone effects when chemicals were combined at individual concentrations eliciting 1%, 10% or 20% AR antagonistic effect. Due to the large number of mixture components, the combined AR antagonistic effects occurred at very low concentrations of individual mixture components. CA slightly underestimated the combined effects at all mixture ratios. In conclusion, large numbers of AR antagonists from a wide variety of sources and exposure routes have the ability of acting together at the receptor to produce joint effects at very low concentrations. Significant mixture effects are observed when chemicals are combined at concentrations that individually do not induce observable AR antagonistic effects. Cumulative risk assessment for AR antagonists should apply grouping criteria based on effects where data are available, rather than on criteria of chemical similarity.

  9. A framework for the use of single-chemical transcriptomics data in predicting the hazards associated with complex mixtures of polycyclic aromatic hydrocarbons.

    PubMed

    Labib, Sarah; Williams, Andrew; Kuo, Byron; Yauk, Carole L; White, Paul A; Halappanavar, Sabina

    2016-11-17

    The assumption of additivity applied in the risk assessment of environmental mixtures containing carcinogenic polycyclic aromatic hydrocarbons (PAHs) was investigated using transcriptomics. MutaTMMouse were gavaged for 28 days with three doses of eight individual PAHs, two defined mixtures of PAHs, or coal tar, an environmentally ubiquitous complex mixture of PAHs. Microarrays were used to identify differentially expressed genes (DEGs) in lung tissue collected 3 days post-exposure. Cancer-related pathways perturbed by the individual or mixtures of PAHs were identified, and dose-response modeling of the DEGs was conducted to calculate gene/pathway benchmark doses (BMDs). Individual PAH-induced pathway perturbations (the median gene expression changes for all genes in a pathway relative to controls) and pathway BMDs were applied to models of additivity [i.e., concentration addition (CA), generalized concentration addition (GCA), and independent action (IA)] to generate predicted pathway-specific dose-response curves for each PAH mixture. The predicted and observed pathway dose-response curves were compared to assess the sensitivity of different additivity models. Transcriptomics-based additivity calculation showed that IA accurately predicted the pathway perturbations induced by all mixtures of PAHs. CA did not support the additivity assumption for the defined mixtures; however, GCA improved the CA predictions. Moreover, pathway BMDs derived for coal tar were comparable to BMDs derived from previously published coal tar-induced mouse lung tumor incidence data. These results suggest that in the absence of tumor incidence data, individual chemical-induced transcriptomics changes associated with cancer can be used to investigate the assumption of additivity and to predict the carcinogenic potential of a mixture.

  10. The secret of dimethyl sulfoxide-water mixtures. A quantum chemical study of 1DMSO-nwater clusters.

    PubMed

    Kirchner, Barbara; Reiher, Markus

    2002-05-29

    DMSO-water mixtures exhibit a marked freezing point depression, reaching close to 60 K at n(DMSO) = 0.33. The phase diagram indicates that stable DMSO-water clusters may be responsible for this phenomenon. Using time-independent quantum chemical methods, we investigate possible candidates for stable supermolecules at mole fractions n(DMSO) = 0.25 and 0.33. The model clusters are built by adding various numbers of water molecules to a single DMSO molecule. Structures and interaction energetics are discussed in the light of experimental and theoretical results from the literature. A comparison with results from molecular dynamics simulations is of particular interest. Our optimized structures are spatially very different from those previously identified through MD simulations. To identify the structural patterns characterizing the clusters, we classify them on the basis of hydrogen-acceptor interactions. These are well separated on an interaction energy scale. For the hydrophobic interactions of the methyl groups with water, attractive interactions of up to 8 kJ/mol are found. In forming clusters corresponding to a range of different mole fractions, up to four water molecules are added to each DMSO molecule. This corresponds to a rough local model of solvation. Examination of the trends in the interactions indicates that the methyl-water interaction becomes more important upon solvation. Finally, we investigate how the clusters interact and attempt to explain which role is played by the various structures and their intercluster interaction modes in the freezing behavior of DMSO-water.

  11. DETECTING INTERACTIONS(S) AND ASSESSING THE IMPACT OF COMPONENT SUBSETS IN A CHEMICAL MIXTURE USING FIXED-RATIO MIXTURE RAY DESIGNS

    EPA Science Inventory

    An important environmental and regulatory issue is the protection of human health from potential adverse effects of cumulative exposure to multiple chemicals. Gennings et al. (2002) and Meadows et al. (2002) suggest restricting inference to specific fixed-ratio rays of interest....

  12. DETECTING INTERACTIONS(S) AND ASSESSING THE IMPACT OF COMPONENT SUBSETS IN A CHEMICAL MIXTURE USING FIXED-RATIO MIXTURE RAY DESIGNS

    EPA Science Inventory

    An important environmental and regulatory issue is the protection of human health from potential adverse effects of cumulative exposure to multiple chemicals. Gennings et al. (2002) and Meadows et al. (2002) suggest restricting inference to specific fixed-ratio rays of interest....

  13. 40 CFR 180.1306 - Isaria fumosorosea (formerly Paecilomyces fumosoroseus) Apopka strain 97; exemption from the...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Isaria fumosorosea (formerly Paecilomyces fumosoroseus) Apopka strain 97 in or on all food commodities... Paecilomyces fumosoroseus) Apopka strain 97; exemption from the requirement of a tolerance. 180.1306 Section... TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1306...

  14. 40 CFR 180.1306 - Isaria fumosorosea (formerly Paecilomyces fumosoroseus) Apopka strain 97; exemption from the...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Isaria fumosorosea (formerly Paecilomyces fumosoroseus) Apopka strain 97 in or on all food commodities... Paecilomyces fumosoroseus) Apopka strain 97; exemption from the requirement of a tolerance. 180.1306 Section... TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1306...

  15. 40 CFR 180.1306 - Isaria fumosorosea (formerly Paecilomyces fumosoroseus) Apopka strain 97; exemption from the...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Isaria fumosorosea (formerly Paecilomyces fumosoroseus) Apopka strain 97 in or on all food commodities... Paecilomyces fumosoroseus) Apopka strain 97; exemption from the requirement of a tolerance. 180.1306 Section... TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1306...

  16. 40 CFR 180.1159 - Pelargonic acid; exemption from the requirement of tolerances.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions... food commodities when used as a plant regulator on plants, seeds, or cuttings and on all food... herbicide is exempt from the requirement of a tolerance on all plant food commodities provided that:...

  17. 40 CFR 180.1180 - Kaolin; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Kaolin; exemption from the requirement of a tolerance. 180.1180 Section 180.1180 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions...

  18. 40 CFR 180.1307 - Bacteriophage of Clavibacter michiganensis subspecies michiganensis; exemption from the...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Bacteriophage of Clavibacter... EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1307 Bacteriophage of... exemption from the requirement of a tolerance is established for residues of lytic bacteriophage...

  19. 40 CFR 180.1307 - Bacteriophage of Clavibacter michiganensis subspecies michiganensis; exemption from the...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Bacteriophage of Clavibacter... EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1307 Bacteriophage of... exemption from the requirement of a tolerance is established for residues of lytic bacteriophage...

  20. 40 CFR 180.1307 - Bacteriophage of Clavibacter michiganensis subspecies michiganensis; exemption from the...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Bacteriophage of Clavibacter... EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1307 Bacteriophage of... exemption from the requirement of a tolerance is established for residues of lytic bacteriophage...