Minamata Disease

     Minamata Bay, Kumamoto Prefecture, Japan is rich in marine fish and is a fishing ground. In 1956, a strange disease was discovered near Minamata Bay. This disease first appeared in cats. After the cat became ill, the gait was unstable and the cat convulsed, so the disease was called "Feline Chorea" at first. Soon after, the disease was discovered in people. The patient developed symptoms similar to sick cats due to damage of the central and peripheral nerves of the brain. This is the "Minamata Disease" that later caused a sensation in the world.

 

    Minamata disease is a disease caused by methylmercury pollution. Its symptoms include slurred speech, staggering steps, facial dementia, numbness of hands and feet, sensory disturbance, loss of vision, tremor, and deformity of hands and feet. More severe symptoms include neurological disorders, bending body, and screams until death.

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     In 1925, Chisso Corporation of Japan established a factory there and then opened a synthetic acetic acid factory. The company used inorganic mercury as a catalyst when producing acetaldehyde. From 1932 to 1966, the company discharged untreated mercury-containing waste into the sea. When mercury enters the ocean, it chemically reacts with marine microorganisms and becomes toxic methylmercury. Fish, shrimps, and shellfish living there were contaminated by methylmercury. Residents who ate such seafood containing methylmercury then became victims of methylmercury.