Map of Minamata Bay and River

During the 1950s, strange events began happening around Minamata Bay, located in the Kumamoto Prefecture of Japan. Fish floated belly-up and birds collapsed while flying. Cats convulsed, salivated excessively, jumped into the sea and drowned, or merely dropped dead. Eventually, a young girl was brought to a physician because she was having difficulty walking and talking, and it was discovered that her sister and other neighborhood children were showing the same symptoms. It wasn’t long until the physician declared that “an unclarified disease of the central nervous system has broken out.”

This mysterious disorder was officially recognized in 1956 and later termed Minamata Disease. In 1958, two doctors from the Kumamoto University published a report in The Lancet that described the disease as widespread degeneration of the nervous system, particularly in the cerebellum. Although they could not pinpoint the underlying cause, they noted that fisherman and their families were those that were primarily affected. This lead them to suggest that a toxic agent from the waste flowing into Minamata Bay from the nearby fertilizer factory was the cause. Many years before, in 1908, the Chisso Corporation opened a chemical factory in Minamata. The factory disposed of its waste into Minamata Bay and later to the mouth of the Minamata River, leading to the contamination of the entire Shiranui Sea. A year after The Lancet article was published, methylmercury, generated by acetaldehyde production at the factory, was identified to be the toxic agent. When the citizens of Minamata consumed fish and shellfish from the sea, they were poisoned by the methylmercury and the epidemic took hold. To date, over two thousand people have been affected by Minamata Disease.

In 1959, Chisso Corporation was ordered to switch the flow of its waste from the river back to the bay. In a display of grandeur, the Chisso Corporation also unveiled a newly installed water purification tank, which lead most people to believe Minamata Disease was resolved. However, the Chisso Corporation misled the public as the purification tank was not removing methylmercury from the waste. As a result, Minamata Disease continued to ravage the community in the years following. It wasn’t until 1968 that the government released an official conclusion that methylmercury, originating from the factory, caused the disease and that Chisso Corporation halted release of methylmercury into the sea. After hundreds lost their lives and years of lengthy legal battles, the Chisso Corporation and the state have paid millions of dollars to the Minamata disease victims. Additionally, in response to the epidemic, numerous environmental policy changes occurred. Japan set safe regulatory standards for mercury and methylmercury levels in fish and shellfish and also instituted clean up efforts in Minamata Bay. In 1997, Minamata Bay was officially declared safe and fishing efforts resumed. However, the outbreak of Minamata Disease remains one of the most influential environmental disasters to occur in Japan to date and is a reminder of the potential devastating effects of pollution.

Peer edited by Kelsey Noll.

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