Minamata Disease, How it is caused, precaution and cure

Minamata Disease, cause, precaution and cure

People worldwide are not familiar with Minamata Disease, but this severe condition was first identified in Minamata, Japan. It is not a disease but a neurological syndrome that is the outcome of marine pollution and environmental contamination. The first case of this disorder came to light in 1956 in Japan that affected several people, local animals, especially cats, and it continued to trouble people in the country through the following ten years as nothing was done to control the contamination. Even the city lends its name to this disorder that was first noticed there.  The specific pollutant that is responsible for this condition is methyl mercury which affects the central nervous system.

Minamata disease

Causes of Minamata Disease

The consumption of large amounts of shellfish and fish that were highly polluted with toxic chemicals- methyl mercury – generated in industries or chemical factories and then discharged into the sea is the primary cause of this condition. 

Hair samples have been taken to check the level of mercury in the body. And it is accepted that if the mercury level in hair samples is higher than 50 parts per million, it may result in nerve damage. Unfortunately, the people living in Minamata had mercury levels as high as 700 ppm. 

How Methyl Alcohol Reached the Sea?

Chisso- one of the biggest Japanese chemical companies, discharged its waste into Minamata Bay. The toxic chemicals that were dumped into the sea also included methyl mercury, which was absorbed and consumed by plankton- the primary food source for fish and shellfish. It contaminated the small fish that were eaten by the larger fish that also absorbed mercury. At this point, the poisoning continued to spread further on the birds feeding these fishes. Birds that ate the fish were also contaminated and spread the pollutant to the other predators that prayed on these birds. 

People dwelling in Minamata areas used to get their protein intake from seafood, and sadly, the pollutants released in the Minamata Bay were not scattered over a wide area but remained accumulated within the bay, which increased the risks of the people living nearby. 

Mercury poisoning cases were also found in the United States of America, New Mexico and Iraq. In Iraq, almost 6,000 people get affected by this because they consumed flour that was processed from mercury-treated grains. 


Everyone who eats contaminated food can get Minamata disease. Pregnant women and their unborn children are at higher risk for mercury poisoning. Methyl-mercury can reach the fetus through the placenta and can affect the brain development of the child. 

The chemical deposits get concentrated in neural tissues and adversely affect them. The effect of toxin in infants cannot be prevented.

Symptoms of Minamata Disease

  • Strong uncontrollable tremors
  • Loss of motor control during voluntary movements, called Ataxia
  •  Speech and hearing Loss of auditory and visual sense impairment
  • Partial paralysis 
  • Numbness in the hands and feet

These are general symptoms of mercury poisoning; the signs and the combinations of symptoms may vary in severity. 

Signs in the Children and Infants Inherited the Condition

  • Impaired neurological development
  • Seizures
  • Mental Retardation
  • Blindness and deafness in children 


The disease most often is curable with a simple procedure of collecting and testing hair samples in a laboratory to measure mercury levels. Doctors suggest optokinetic nystagmus pattern (OKP) and electro-ophthalmopathy (EOG) get referential data if there are mild symptoms or in new cases.


The source of exposure should be isolated to prevent any further exposure, which is the first and foremost way to avoid the disease.


The Treatment for Minamata disease may vary as per the severity level. Here are some standard approaches: 

1.         Removal of toxic chemicals from the body using chelating agents. These agents stop heavy metals like mercury from combining with body tissue. There is one risk associated with chelating agents that mercury reallocates and can sometimes reach the brain. 

2.         Physical Rehabilitation for patients to get back some control over movement.

3.         Doctors prescribe anticonvulsant drugs to patients who suffer from convulsions.

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Author: Ahaana Sahay