PPT Slide
In 1968, the government sorted out all information related to Minamata Disease that had been gathered until then and announced its viewpoint. It concluded that Minamata Disease was resulted from the poisoning of the central nervous system caused by methylmercury compound, which was generated as a by-product in the process of manufacturing acetaldehyde at Chisso Co., Ltd. in Minamata City and Showa Denko Co., Ltd., at
the upstream of Agano River. The compound, discharged along with industrial wastewater, polluted the environment and became accumulated in fish and other marine creatures through the food chain. Residents contracted Minamata Disease when they consumed large quantity of contaminated seafood.
http://www.env.go.jp/en/topic/minamata/ch2.html