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Niigata Minamata disease

Niigata Minamata disease
Classification and external resources
ICD-10 T56.1
ICD-9-CM 985.0
MedlinePlus 001651

Niigata Minamata disease (新潟水俣病 Niigata Minamata-byō) is a neurological syndrome caused by severe mercury poisoning. Identical in symptoms to the original outbreak of Minamata disease in Kumamoto Prefecture, the second outbreak in Niigata Prefecture was confirmed with the same name in 1965. The disease was caused by severe mercury poisoning, the source of which was methylmercury released in the wastewater from mercury sulfate-catalysed acetaldehyde production at the Showa Electrical Company's chemical plant in Kanose village. This highly toxic compound was released untreated into the Agano River where it bioaccumulated up the food chain, contaminating fish which when eaten by local people caused symptoms including ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision and damage to hearing and speech.

690 people from the Agano River basin have been certified as patients of Niigata Minamata disease.[1]

Since the Niigata outbreak was the second recorded in

  • "Minamata Disease: The History and Measures", The Ministry of the Environment, (2002), retrieved 17 January 2007
  • Harada, Masazumi. (1972). Minamata Disease. Kumamoto Nichinichi Shinbun Centre & Information Center/Iwanami Shoten Publishers. ISBN 978-4-87755-171-1 C3036
  • George, Timothy S. (2001). Minamata: Pollution and the Struggle for Democracy in Postwar Japan. Harvard University Asia Center. ISBN 978-0-674-00785-7
  • Saito, Hisashi. (2009). Niigata Minamata Disease: Methyl Mercury Poisoning in Niigata, Japan. Niigata Nippo.


  1. ^ Official government figure as of March 2001. See "Minamata Disease: The History and Measures, ch2"
  2. ^ a b Harada, pp86-91
  3. ^ George, p187
  4. ^ George, pp246-247
  5. ^ Harada, p90


See also

The events in Niigata catalysed a change in response to the original Minamata incident. The scientific research carried out in Niigata forced a re-examination of that done in Minamata and the decision of Niigata patients to sue the polluting company allowed the same response to be considered in Minamata. Masazumi Harada has said, "It may sound strange, but if this second Minamata disease had not broken out, the medical and social progress achieved by now in Kumamoto... would have been impossible."[5]

A family member of the deceased patient testified in court, "My father was crazed like a wild beast and then died—agonized, in pain... like a dog."

The Niigata lawsuit was ultimately successful, and on 29 September 1971, the court found Showa Denko guilty of negligence. Families of deceased and congenital patients received JPY10 million, surviving patients were awarded between JPY1 million and 10 million depending on symptoms, JPY400,000 to those contaminated by mercury, and JPY300,000 were awarded to pregnant women who had been told to have abortions due to the danger posed to their unborn children.[4]

On 26 September 1968, the government announced its official conclusion as to the cause of Niigata Minamata disease. The report said, although "the circumstances of the poisoning are extremely complex, and they are difficult to reproduce", the mercury had probably been discharged from the Kanose plant over a long period of time. However, the report did not rule out other causes and Showa Denko's president, Masao Yasunishi, insisted the company was not the cause of the outbreak.[3]

Unlike their counterparts in Minamata, the victims of Showa Denko's pollution lived a considerable distance from the factory and had no particular link to the company. As a result, the local community was much more supportive of patients' groups and a lawsuit was filed against the company in March 1968. The Niigata lawsuit was filed only three years after the outbreak had been made public in 1965. In contrast, the first lawsuit filed in Minamata happened in 1969, 13 years after the original outbreak was discovered.

Patients' lawsuit

Showa Denko responded to the outbreak of Niigata Minamata disease in a similar way that Chisso had responded in Minamata: by attempting to discredit the researchers while proposing their own theory. The company issued information leaflets that rejected their wastewater as the cause of the disease and suggested the cause might have been an "agricultural chemical run-off" that entered the river after the 1964 Niigata earthquake.

Response of Showa Denko

Throughout 1965 and 1966, researchers from the wastewater was reported to be suspected as the source of pollution, and in September, the Ministry of Health and Welfare announced it had discovered methylmercury in moss at the outlet of the Showa Denko factory in Kanose village.[2]


The second outbreak of Minamata disease in Niigata Prefecture was discovered in a very similar way to the original outbreak in mercury poisoning in the Agano River basin to the prefectural government and made his findings public on 12 June.[2]




  • History 1
    • Discovery 1.1
    • Investigation 1.2
    • Response of Showa Denko 1.3
    • Patients' lawsuit 1.4
  • See also 2
  • Notes 3
  • References 4

. Four Big Pollution Diseases of Japan. It is one of the )Agano-gawa Yūki-suigin Chūdoku 阿賀野川有機水銀中毒(

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