It has also been suggested that some of the mercury sulfate in the wastewater was also metabolized to methylmercury by bacteria in the sediment. It was caused by the release of methylmercury in the industrial wastewater from a chemical factory owned by the Chisso Corporation, which continued from 1932 to 1968. Minamata disease was first discovered in the city of Minamata, Kumamoto Prefecture, Japan, in 1956, hence its name. A congenital form of the disease can also affect fetuses in the womb. In extreme cases, insanity, paralysis, coma, and death follow within weeks of the onset of symptoms. Signs and symptoms include ataxia, numbness in the hands and feet, general muscle weakness, loss of peripheral vision, and damage to hearing and speech. Minamata disease, sometimes referred to as Chisso-Minamata disease, is a neurological disease caused by severe mercury poisoning. The hand of Tomoko Uemura, Minamata disease victim
