Reappraisal of the historic 1959 cat experiment in Minamata by the Chisso Factory.

PubMed

Eto, K; Yasutake, A; Nakano, A; Akagi, H; Tokunaga, H; Kojima, T

2001-08-01

Autopsy specimens from the historic cat experiment were recently discovered in a storage area at the Kumamoto University School of Medicine. The specimens were from an experiment prompted by physicians in the Chisso Minamata Plant following the announcement made by the Study Group for Minamata disease. On July 14, 1959 the Group announced that the disease was most likely caused by a kind of organic mercury. In order to prove or disprove that industrial waste from the Chisso Factory was the culprit in Minamata disease, a total of ten cats were fed food mixed with industrial waste produced in the acetaldehyde-producing plant. One of the ten cats, No. 717, was subsequently autopsied but the autopsy findings have never been published or recorded in the literature despite their historic significance. The rediscovered specimens were studied pathologically and biochemically, and were analyzed chemically with currently available techniques. Characteristic lesions of methylmercury poisoning were observed in the central nervous system, and the mercury levels in the cerebrum, cerebellum, liver and kidney were found to be markedly elevated in this animal.

[Bibliographical study of the toxicity of organic mercury compounds].

PubMed

Ishihara, Nobuo

2011-09-01

The aim of this study is to correct the misunderstanding that the toxicity of organic mercury compounds is unknown at the time of the outbreak of Minamata disease (May 1, 1956). Two case reports of organic mercury (methylmercury) intoxication were published already in 1865 and 1866. The conversion of inorganic mercury added in acetoaldehyde synthesis was already pointed out in 1921. In 1930 several cases of organic mercury poisoning among workers engaged in acetoaldehyde production were reported. Many reports on not only in occupational exposure but a oral exposure via the ingestion of flour made from grains treated with organic mercurials were available at the time of the outbreak of Minamata disease (May 1, 1956). These reports pointed out the toxic effects of organic mercury on the central nervous system, and indicated cleary that the causal substance of Minamata disease must be the organic mercury compounds (methylmercury) from the Chisso plant. The identification of methylmercury as the causal substance by the authority was presented in 1968 when acetoaldehyde production in the Chisso plant was closed. Most of these reports except that of (Hunter et al.) were not referred to in the study of Minamata disease . Inadequate referencing should be pointed out. Several reports indicated that the causal substance of Minamata disease must be methylmercury from the Chisso Plant. However, most of these reports were not referred to during the study of Minamata disease. Inadequate referencing of literatures should be pointed out.

[Food Sanitation Act and Minamata Disease].

PubMed

Ishihara, Nobuo

2016-01-01

Immediately after the official recognition of Minamata disease (1956.5.l) a study group at Kumamoto University suggested that Minamata disease was caused by food poisoning. The next year, this suggestion was accepted by the Ministry of Health and Welfare (MHW). Prior to the decision to apply the Food Sanitation Act (FSA), the local government asked MHW for the application of FSA. Soon after, the chief of the Public Health Bureau replied to the local government that the application of FSA to the Minamata area was impossible. Epidemiological investigations of residents and polluted areas, therefore, were not carried out. Data essential for the screening for exposed residents were unavailable. The criteria for the screening were presented. The Environmental Agency (EA) presented the criteria in the form of notice in 1971, which were revised in 1977. Notwithstanding the clear difference between the original and revised criteria, EA insisted that these two sets of criteria were quite similar. This insistence by EA and the absence of epidemiological data on residents and polluted area resulted in the present confusion about Minamata disease. The application of FSA was stopped by bureaucrats who had no interest in the environmental problems and by several scientists patronized by stakeholders (Chisso, Japanese Association of Chemical Industries, MHW and EA). Stakeholders suppressed science.

Minamata disease: methylmercury poisoning in Japan caused by environmental pollution.

PubMed

Harada, M

1995-01-01

Minamata disease (M. d.) is methylmercury (MeHg) poisoning that occurred in humans who ingested fish and shellfish contaminated by MeHg discharged in waste water from a chemical plant (Chisso Co. Ltd.). It was in May 1956, that M. d. was first officially "discovered" in Minamata City, south-west region of Japan's Kyushu Island. The marine products in Minamata Bay displayed high levels of Hg contamination (5.61 to 35.7 ppm). The Hg content in hair of patients, their family and inhabitants of the Shiranui Sea coastline were also detected at high levels of Hg (max. 705 ppm). Typical symptoms of M. d. are as follows: sensory disturbances (glove and stocking type), ataxia, dysarthria, constriction of the visual field, auditory disturbances and tremor were also seen. Further, the fetus was poisoned by MeHg when their mothers ingested contaminated marine life (named congenital M. d.). The symptom of patients were serious, and extensive lesions of the brain were observed. While the number of grave cases with acute M. d. in the initial stage was decreasing, the numbers of chronic M. d. patients who manifested symptoms gradually over an extended period of time was on the increase. For the past 36 years, of the 2252 patients who have been officially recognized as having M. d., 1043 have died. This paper also discusses the recent remaining problems.

Methylmercury level in umbilical cords from patients with congenital Minamata disease.

PubMed

Harada, M; Akagi, H; Tsuda, T; Kizaki, T; Ohno, H

1999-08-30

A total of 151 umbilical cords during the period from 1950 to 1969 were collected from the residents of the Minamata area (including 25 patients with congenital Minamata disease) for methylmercury (MeHg) analysis. When the MeHg discharge from the Chisso Company's Minamata factory into the Minamata Bay is compared with the incidence of congenital Minamata disease, the abrupt increase of the former in 1952 [Nishimura H. Chem. Today 1998;323:60-66] was found to precede that of the latter by approximately 2 years, thereby indicating that MeHg is the cause of the disaster. This was confirmed by the elevated levels of MeHg in the umbilical cords from residents of the Minamata area [from 0.35 +/- 0.30 (S.D.) ppm in 1952 to 0.96 +/- 0.75 ppm in 1955], the MeHg levels (1.60 +/- 1.00 ppm) in the cords from patients with congenital Minamata disease showing the highest values [P < 0.01 vs. acquired Minamata disease (0.72 +/- 0.65 ppm), mental retardation (0.74 +/- 0.64 ppm), other diseases (0.22 +/- 0.15 ppm), and no symptoms (0.28 +/- 0.20 ppm), respectively]. Thus, in order to fill a gap, which extends over a long period of time, in studies on environmental Hg pollution, umbilical cord samples were considered to be a useful tool.

[Minamata disease: a neuropathological viewpoint].

PubMed

Eto, Komyo

2006-01-01

Minamata disease (methylmercury poisoning) was first officially discovered around Minamata Bay in the Kumamoto Prefecture on May 1st, 1956. This year, a commemoration marking fifty years since this discovery of Minamata disease will be held in Minamata City. Over the years, new facts have gradually surfaced, especially after 1995, with the resolution of the political problems surrounding Minamata disease. For example, it was recently reported that large amounts of methylmercury were generated by the chemical processes of the Chisso acetaldehyde plant and later dumped directly into Minamata Bay. This report revealed the August 1951 switch from using manganese dioxide to ferric sulfide as a reaction promoter to maintain the activity of the Hg catalyst. As a result of this switch, the amount of methylmercury generated in the process rapidly increased. Thus, the true cause of the acute onset of Minamata disease in patients with a high-dose contamination of methylmercury was made clear. The severe contamination by methylmercury continued until 1968, when the plant finally stopped discharging its waste water into Minamata Bay. In 1996, the National Institute for Minamata Disease started an experimental study of methylmercury poisoning using the common marmoset. Results from this study showed that the lesions characteristic of the central nervous system in cases of acute methylmercury poisoning were promoted by brain edema, while those of the peripheral nerves were caused by axonal degeneration. Peripheral nerves were regenerated in two animals after two and a half years. Lesions characteristic of Minamata disease are systematically found throughout the nervous system. These lesions are found in the calcarine areas of occipital lobes, the pre- and post-central lobes, and the temporal transverse gyri. Milder and more diffuse lesions are also found in the cerebrum, where secondary degeneration of the central parts of white matter and internal sagittal stratum are due to