What is Minamata Disease?

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  • Written By: Donn Saylor
  • Edited By: John Allen
  • Last Modified Date: 06 October 2019
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Minamata disease is a neurological syndrome triggered by acute mercury poisoning. Also known as Chisso-Minamata disease, it was first discovered in the Japanese city of Minamata in 1956. Nearly 1,800 people have died from the disease, and it has had a major impact on the studies of pollution and toxicology.

Common symptoms of Minamata disease included lack of muscle coordination; muscle fatigue; loss of sensation in the extremities; and problems with vision, hearing, and speech. More serious symptoms — mental instability, muscle paralysis, convulsions, coma — were also been reported and, in many cases, led to death. Minamata disease could also be congenital and infect babies in the womb.

Minamata disease was not infectious. It was treated with various medications and therapies. Severe cases experienced significant nerve cell damage, which oftentimes became fatal. Children born to mothers with the disease were found to have physical deformities and mental retardation.

Around 1950, cats in the seaside town of Minamata, Japan, began behaving strangely. They appeared to have seizures, lose their minds, and then throw themselves into the sea. Soon more of the town's animal population began experiencing the same symptoms. In 1956, two young sisters went to their family doctor suffering seizure-like symptoms, numbness in their hands and feet, and hysterical outbursts. This was the first official diagnosis of Minamata disease, though subsequent research found that more than 50 townspeople had the illness by the time the girls were diagnosed, and 17 of them were already dead.


It was soon discovered that the town's chemical plant, the Chisso Corporation, was dumping methylmercury into the sea. The toxic substance had infiltrated the marine life of the area, and the people of Minamata had been unknowingly consuming the tainted fish for decades. Once the cause of the heavy metal poisoning had been identified, the Chisso Corporation continued to dump methylmercury into the waters around Minamata until 1968. Though the process took years, victims and their families eventually received financial remuneration from Chisso. Minamata disease has had devastating effects on the region, and as of 2001, there were still 3000 people living with the disease; no new cases of Minamata disease have been reported.

Minamata disease played an important role in environmental awareness — namely the effects of pollution — and element toxicology. The disease was the single worst case of industrial pollution in Japanese history. It brought to the forefront issues relating to public health, corporate responsibility, citizens' rights, and the impact of heavy metal poisoning.


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