Minamata Disease | Causes | Symptoms | Treatment | Aftereffects

Minamata disease describes methylmercury poisoning that can lead to irreversible damage to the nerves. The disease first occurred when toxic pollutants from the industries affected the fish. These fishes comprised the food supply of the coastal community in Minamata, Japan.

Minamata disease is a large-scale mercury poisoning resulting from methylmercury contamination in seafood. (⁽¹)

The first case gained recognition when a factory in Minamata City released discharge including methylmercury, a byproduct of acetaldehyde production into Minamata Bay. ⁽²⁾ The factory was responsible for the outbreak in 1962 and the correlation was acknowledged in 1968 as by that time the mercury poisoning had spread to the entire coastline of the inland sea.

There have been several outbreaks of Minamata disease and pollution has been the main cause of it. The cases resulted from consuming contaminated fish.

Once there was the largest methylmercury poisoning in Iraq. In the 1971-1972 winter, the bread had become contaminated as the seed wheat contained methylmercury fungicide.

Minamata disease leads to neurological signs and symptoms, which include:

• Tunnel vision
• Sensory disturbance
• Ataxia or a lack of muscle coordination that may affect a person’s voluntary movements
• Dysarthria, a speech disorder that may occur due to muscle weakness

The onset of Minamata disease was seen to be sudden. People were found to develop difficulty hearing, seeing, and swallowing deteriorating quickly. They were found to experience convulsions and then coma and death.

The degree of symptoms varies depending on how much a person is exposed to mercury. In severe cases, the symptoms are irreversible, and lower exposure to methylmercury causes milder symptoms.

The research highlighted the importance of rapid recognition and showed that the outbreak would have been much smaller if measures would have been taken to reduce the contamination from the start.⁽²⁾

The treatment measures for Minamata disease include:

• Supportive therapy
• Removal of the source
• Decontamination

The neurological effects of Minamata disease are irreversible and therefore, impossible to cure.

Despite decades of restoration effects of the United Environmental Program, it is found that methylmercury poisoning continues to affect people in Minamata Bay.

Minamata disease was found to affect people who ate fish directly. Findings suggested that fetuses started developing conditions while still in the uterus. ⁽²⁾ It was believed that the placenta would protect them.

The babies were born with cerebral poisoning. Therefore, it was firmly established that methylmercury poisoning could transmit through the fetus.

Minamata disease refers to the tragic event when the people in the coastal community of Minamata Bay developed severe neurological disorders. The condition resulted due to the industrial release of mercury compounds into local water. These compounds were consumed by fish and shellfish thereby affecting the local food supply. Since the outbreak, the community has experienced forms of Minamata disease resulting in neurological signs and in severe cases death.