Minamata Disease: Diseases of the World

A diagram displaying the biomagnification process of mercury.

Minamata disease is a neurological syndrome sometimes known as Chisso-Minamata disease. The disease was first discovered in 1956 in Minamata, in the Kumamoto prefecture of Japan. The disease was caused when methylmercury from the chemical factory of Chisso Corporation was released into the industrial wastewater. The contamination went on from 1932 to 1968. Methylmercury bioaccumulated in fish and shellfish in the Shiranui Sea and the Minamata Bay which, when it was consumed by the locals, caused mercury poisoning resulting in the deaths of human beings, dogs, pigs and cats. It continued for 36 years. As the contamination went on, the company and the Japanese government did not take immediate action to curb the contamination. By March of 2001, there were 2,265 victims of Minamata disease 1,784 of whom died and more than 10,000 who had received compensation from the company. A total of $86 million in compensation was given to the victims of the disease by 2004, and Chisso Corporation was ordered to clean up the contamination. In 1965 there was another outbreak of the Minamata disease in the Niigata Prefecture.

Description Of The Minamata Disease

Minamata disease is caused by extreme mercury poisoning. Some of the symptoms include loss of peripheral vision, speech and hearing damages, numbness in the feet and hands ataxia, and general weakness to the muscles. In several cases patients experienced paralysis, coma, and death within weeks of developing symptoms of poisoning. A form of the disease can also affect fetuses causing abnormality from birth.

Transmission Of The Minamata Disease

After many months of research, the Minamata Food Poisoning Subcommittee from the Ministry of Health and Welfare released a published report on how the disease was transmitted. Minamata disease is transmitted by the consumption of large numbers of shellfish and fish living in the Minamata Bay and its environs which was contaminated by mercury compound.


Symptoms of Minamata disease were first discovered in April 1956 when children started to exhibit symptoms for an unknown disease. When the symptoms started to become more prevalent throughout the community, it prompted the hospital director at Chisso Corporation factory hospital to report to the local public health office of the newly discovered epidemic in the form on an unknown disease. As an extent of the diseases, crows fell from the sky, dead fish floated on the sea surface, seaweed ceased to grow, and cats exhibited an odd behavior of convulsing and going mad before they died. By October 1956 more and more patients suffering from Minamata disease died as a mortality rate rose to 35%.

Prevalence Of The Minamata Disease

There had been an assumption that the wastewater facilities established in December 1959 did not have any effects on the level of organic mercury being discharged into the Shiranui Sea. However, the disease together with the pollution continued to spread. After investigations by the Kagoshima and Kumamoto prefectural governments, it was discovered that organic mercury had continued to spread to the sea and that people consuming fish around the area were still getting contaminated. Hundreds of locals had mercury levels of more than 50ppm in their hair which is the level where infected people are expected to exhibit symptoms of nerve damage.

Treatment Of The Minamata Disease

The treatment for Minamata disease may vary depending on the extent of the condition and the symptoms present. However, there are certain procedures taken when treating the disease. The first step is to identify and isolate the source of contamination. The second step is to eliminate mercury from bodies of the affected by using chelating agents. Chelating agents are known to prevent heavy metals such as mercury from binding with body tissues. Physical rehabilitation of those with paralysis and poor muscle function while anticonvulsant drugs are given to patients suffering from convulsions.


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