Minamata incident

Another major incident concerning methyl mercury was the severe pollution of Minamata bay in Japan (see Box 8.1). Here fish, fish-eating and scavenging birds, and humans feeding upon fish all died from organomercury poisoning. There may have been localized declines of marine species in this area due to methyl mercury, but there is no clear evidence of this. 

An epidemic of intoxication from ingestion of fish contaminated with methyl mercury occurred in the Minamata district in Japan, and, as a result, methyl mercury intoxication is often referred to as Minamata disease." Infants born to mothers with exposure to large amounts of methyl mercury had microen-cephaly, mental retardation, and cerebral palsy with convulsions. In an incidence in Iraq, ingestion of wheat products contaminated with methyl mercury fungicide by pregnant women caused similar symptoms of neurological damage and mental retardation. The fetus is... 

In one tragic incident, an entire community on Minamata Bay in Japan was poisoned, with extremely serious birth defects, very painful reactions, mental disorders, and many deaths. Only after lengthy research was the cause determined to be mercury compounds discarded into a river by a plastics factory. Whether it was inorganic salts or methylmercury compounds seems uncertain, but the contamination was immense and methylmercury compounds were found in the silt and in animals and humans. The methylmercury was readily taken up by the organisms living in the bay and, because the people of the community depended on fish and other seafood from the bay for much of their diet, the entire community was poisoned. 

Minamata bay had been contaminated by effluent from a factory that used mercury as a catalyst in the production of acetaldehyde. Many inhabitants died. Even more suffered permanent neurological damage. In addition, a much higher incidence of retarded brain development was observed in Minamata than elsewhere in Japan but the population was too small to yield a cogent answer. 

Four epidemiological studies examined the effect of Hg exposure on cancer incidence or cancer death rate. Those studies are summarized in Table 5-1. Tamashiro et al. (1984) carried out a cohort study that evaluated the causes of death of 334 individuals who had survived Minamata disease (MD) and died between 1970 and 1980. Control cases were selected from deaths that occurred in the same city or town as the MD cases and were matched for sex, age and year of death. No significant difference in cancer death rates was observed between the subjects and the controls, suggesting that the risk of dying from cancer was not correlated with patient history of MeHg poisoning. Specific types of cancer, however, were not evaluated. 

Alkyl compounds of mercury (RHgX) and other organomercury compounds (i.e., methyl mercury) are strong irritants (eye, mucous membranes and skin), the latter with a direct effect on chromosomes. In fact, Minamata disease is termed after the methyl mercury intoxication incidence observed in the fish meat in Minamata, Japan, which produced neurological damage and mental retardation in newborn babies [42]. 

Other incidents— the oily, black, carcinogen-laden liquids that heavy rains brought to the ground surface of Love Canal, a community built on a toxic chemical dump mercury dumped from a chemical plant into the estuary at Minamata, Japan, which caused paralysis and mental disorders in thousands of people and death for several hundred and in 1984 the methyl isocyanate leak in Bhopal, India, that killed some 2000 people and injured tens of thousands more— have not helped the negative image of chemistry. 

Mercury is easily converted to methylmercury by bacteria. Methylmercury is more readily absorbed by cells than mercury itself. As a result, methylmercury accumulates in the food chain as shown in the diagram below. A serious incident of methylmercury poisoning occurred in Japan in the 1950s. People living in Minamata, Japan, were exposed to high levels of methylmercury from eating shellfish. 

One of the worst incidents of mercury poisoning occurred in Minamata and Niigata, Japan, in 1950. At that time, the ocean was polluted with high levels of mercury from industrial wastes. Because fish were a major food in the diet, more than 2000 people were affected with mercury poisoning and many died or developed neural damage. In the United States, between 1988 and 1997, the use... 

The first incident in the modern era to bring mercury and its hazards to the public eye occurred at Minamata Bay, Japan, in 1953. Here many fishermen and their families were stricken with mercury poisoning when they ate fish and shellfish that contained high amounts of mercury, ultimately traced to the effluent of a nearby poly(vinylchloride) factory. Mercury in fish, particularly those such as tuna, marlin, and swordfish at the top of aquatic food chains, soon became a newsworthy... 

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