Niigata Minamata disease.

About Niigata Minamata disease

From 1964 at the earliest to the 1970s at the latest, an outbreak of Minamata disease — a neurological syndrome caused by severe mercury poisoning — occurred in Niigata Prefecture, Japan. This would be the second outbreak of Minamata disease, the first occurring in its namesake: Minamata — a fishing village in Kumamoto Prefecture. The outbreak was caused by the release of methylmercury into the environment through the wastewater of a chemical plant owned by the Showa Electrical Company (Showa Denko), which had been producing mercury sulfate-catalysed acetaldehyde in nearby Kanose village. This highly toxic compound was released untreated into the Agano River where it bioaccumulated up the food chain, contaminating fish which, when eaten by local people, caused symptoms including ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision, damage to hearing and speech, among others. This would often be followed by death.