In 1956, many people who had eaten fish from the Minamata Bay region of Japan developed symptoms of severe mercury poisoning. Factory waste water from a factory owned by Chisso Co. Ltd. had contaminated the water with mercury compunds, which were taken into the food chain. This was only formally admitted in 1968.

The main symptoms of this disease are neurological. They include, headaches, numbness, memory loss, insanity, balance problems and tinittus. In several cases the nerve damage was so severe that death occured. While many thousands of cases were given compensation, only a little over 2000 were certified by the government as severe, and of these about 1000 died. Babies born to affected mothers suffered from congenital disorders.

Chissco Co. Ltd. Still exists, and is given financial aid to help in its compensation payments.