"Minamata disease" is the term used to describe the poisoning that occurred among residents of Minamata, Japan due to the ingestion of methyl-mercury-containing seafood. From the 1920s through the 1960s, the Chisso Company used mercury as a catalyst in the production of acetaldehyde, a chemical intermediate with numerous uses including plastics and perfume production. The Chisso Company dumped waste methylmercury from the acetaldehyde production into Minamata Bay. The methylmercury bioaccumulated within the food chain, from plankton and other microorganisms up to fish and shellfish. This posed a significant health hazard to residents of the area who obtained much of their protein from Minamata Bay seafood.
In the early 1950s, Minamata Bay residents began to exhibit symptoms of neurological illness, such as uncontrollable trembling, loss of motor control, and partial paralysis. Children also began to be born with Minamata disease, exhibiting symptoms similar to cerebral palsy (impaired neurological development and seizures). By the late 1950s, scientists from Japan's Kumamoto University strongly suspected that methylmercury was the cause of Minamata disease.
Methylmercury concentrates in neural tissues, which explains why neurotoxicity was the major adverse effect observed in Minamata Bay. Offspring of Minamata Bay residents afflicted with Minamata disease also exhibited neurotoxicity because methylmercury can be transferred across the placenta. Between 1953 and 1960, 628 cases of illness were documented, including 78 deaths. Total cases of morbidity and mortality caused by Minamata disease from the 1950s to the year 2000 are thought to range in the thousands but the exact number is not known.
MARGARET H. WHITAKER
BRUCE A. FOWLER
Tsubaki, T., and Irukayama, K. (1977). Minimata Disease. Methylmercury Poisoning in Minamata and Niigata, Japan. Amsterdam: Elsevier Scientific Publishers.
Ui, J. (1992). Industrial Pollution in Japan. Tokyo: United Nations University Press. Available at http://www.unu.edu/unupress/unupbooks.
World Health Organization (1990). Methyl Mercury. Environmental Health Criteria 101. Geneva: Author.