Minamata disease is one of the few diseases named after a location. In fact, it is not really a disease, but a poisoning land it has occurred at other places besides Minamata. The disease was methyl mercury poisoning and the events at Minamata became widely known during the late 1950's and early 1960's.

Minamata is a fishing and industrial town in southern Japan. Its largest industry is the Chisso corporation, which manufactures petrochemicals. In 1932 the factory began to manufacture acetaldehyde, which is used for drugs, plastics and perfumes. The people of Minamata had urged the factory to expand production to employ more people, and by the 1950's the town’s population was 50,000, many of whom relied on the factory for their income.


The production of acetaldehyde expanded too. But during the early 1950's the fishermen, who produced most of the town's food reported strange changes in the life of Minamata bay. Fish were dying in large numbers for no apparent reason, and some birds were so weak that they could not fly.


In the town itself, something was happening to the cats. A "dancing" disease would suddenly affect a cat, and it would stagger about, before convulsing or spinning in circles. The disease killed so many cats that by 1958, there were few left in town. Dogs and pigs were sometimes affected too.


In 1956, a five year old girl was admitted to hospital with symptoms similar to brain disease. Five weeks later her sister and four neighbors were admitted with the same symptoms, which affected their speech, their balance and the control of their mind.


People in town thought that it was an outbreak of an infectious disease, and there was a scare that it would spread further. This fear was increased further when investigations found another thirty people suffering from the same symptoms. No one knew the cause and many different reasons were given for the cause of the epidemic.


Eventually a closer examination of the disease revealed that it was poisoning, and that it was related to the eating of fish. Tests in Minamata bay showed that there were more than seven poisons, which came from the heavy metals, present in the water.


No action was taken at this time to stop fishing in the bay, or to stop the factory from getting rid of its wastes into the sea. Instead, the fishermen of the town continued to catch fish which had been affected by the poisons, and the people of the town continued to eat the fish. The number of patients increased. At the end of 1956 there were 52 known cases.


The search for the particular heavy metal pollution responsible for the outbreaks continued, while the number of people affected increased. In 1958 the Chisso corporation changed the location of their dumping area to the other side of town. Soon afterwards, people began to fall ill in this area.


Eventually, in 1959 the cause of the disease was pin pointed as mercury. Chisso was Using mercury as a catalyst in the production of acetaldehyde. Experiments showed that exposure to the factory wastes was fatal to cats. The Chisso corp. reacted by installing a cyclator purification system which was supposed to treat the waste products. This was later shown to be useless in preventing mercury escaping into the sea, but for a while the local population were content. They accepted the company's assurances, and the token payments they made to victims


Then, in 1965, there was an outbreak of similar poisoning at Niigata, north of Tokyo. The extra evidence of the effects of industrial pollution encouraged a group of victims to sue the Chisso corp. in 1969. The court case took four years to complete, but in 1973, the verdict was given. The court's decision was that the Chisso corp. had been negligent. “No factory can infringe on and run at the sacrifice of the lives and health of residents of the region." said the judge.


The plaintiffs were awarded almost three million dollars which the immediately received from the company. It had already paid about on million dollars and later that year the Central Pollution Contra Board compelled it to pay fifty thousand dollars to each confirmed case of Minamata disease. This has now amounted to a payment of more than sixty million dollars, which includes all the medical bills to patients as well as a monthly allowance.


The disease still affects thousands of the people of Minamata different degrees. Some it has killed, others have become insane or mentally unstable; many are affected in their limbs or their brains; they would move with difficulty, have speech handicaps, and experience all kinds of problems associated with schoolwork. Many of the victims are children who have never eaten the poisoned fish, but have inherited the dimethyl mercury from their mothers as babies.


dimethyl mercury

The government of Japan has now decided that the parts of Minamata bay affected most by the methyl mercury pollution will be filled it The Chisso corp. has long since stopped dumping wastes into the bay but the mercury still remains, able to affect fish and, in turn more people. Discoveries of people affected by Minamata disease continue.


There was so much public outrage in Japan that the nation industries began to look for other ways of waste disposal. One of the favoured methods for a few large industries was to locate a new plant overseas in a country which wanted industry. The waste products would then not be added to the air and waters of Japan.


On a world scale .people in many countries were shocked as the sequence of events at Minamata was exposed. It prompted more public pressure for the safe disposal of industrial waste.



1. What was the type of pollutant involved?

2. Who was producing the pollutant?

3. What types of illness did the poisoning cause?

4. How much money has so far been paid to the victims of "Minamata" disease?

5. If you were investigating the effects of this pollutant on living thins, which types of living things would you experiment on? How would you set up your experiment to test the effects of the poison?

6. Is the pollutant involved a type of cumulative poison?

7. Why did it take so ling for the danger of the poisoning to become so obvious?

8. Do you agree with the idea of locating those industries that create dangerous pollutants, in other overseas countries (and not in your own country)?

9. What symptoms showed up in cats as a result of the poisonous pollutant?

10. Is filling, in the affected parts of Minamata bay a good solution to the pollution problem? Can you suggest other things that might be done in order to reduce or eliminate the danger?


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