Niigata Minamata: mercury poisoning by Showa Denko, Japan

Mercury poisoning was discovered in Niigata some years after the Minamata disease in Kumamoto. The source was methylmercury from the Showa Denko factory, located upstream of the Agano River. One of the Four Big Pollution Disease cases in Japan.


Mercury poisoning was discovered in Niigata some years after the Minamata Bay disease in Kumamoto was recognised. The source was the petrochemical company Showa Denko, located about 50 km upstream of the Agano River. Niigata Minamata Disease is an organic mercury intoxication prevailed in the Agano River area in central part of Niigata Prefecture in 1950s and 1960s. Many patients have suffered from the disease until today, and some of them died of it in  agony.

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Basic Data
NameNiigata Minamata: mercury poisoning by Showa Denko, Japan
Accuracy of LocationMEDIUM regional level
Source of Conflict
Type of Conflict (1st level)Industrial and Utilities conflicts
Type of Conflict (2nd level)Chemical industries
Specific CommoditiesChemical products
Project Details and Actors
Project DetailsMethyl mercury was produced as by-product of acetaldehyde by the Showa Denko company over many years, and it was discharged into the Agano River without any processing to exclude its hazardous nature. It was absorbed by moss and waterweed, and eaten by aquatic insects and fish as their food. Methyl mercury was accumulated biologically in the food-chain in the Agano River. People living around the Agano River, fish eaters, were the last in the food-chain. Niigata Prefecture published the fact of Niigata Minamata Disease as the occurrence of organic mercury intoxication around the Agano River on June 12, 1965, the 40th year after the Showa Denko factory started operations. In 1967, the plaintiffs, three families and 13 people, presented a case to the Niigata District Court. They got favourable decision on September 29, 1971. There were further court cases. As researched by Kazumasa Takemori (2012), total compensation for nearly one thousand cases ammounted to some 10 billion yen, i.e. 200 million USD.
Type of PopulationUrban
Potential Affected Population1000
Start Date1965
Company Names or State EnterprisesShowa Denko from Japan
Relevant government actorsMinistry of Health and Welfare

Minister of International Trade and Industry (MITI)
Environmental justice organisations and other supporters- Minsuitai (formed by labour unions and the JCP: Minamata Disease Coutermeasures Council of Democratic Groups)
The Conflict and the Mobilization
Intensity of Conflict (at highest level)HIGH (widespread, mass mobilization, violence, arrests, etc...)
When did the mobilization beginMobilization for reparations once impacts have been felt
Groups MobilizingLocal ejos
Local government/political parties
Trade unions
Local scientists/professionals

Fisher people
Forms of MobilizationCommunity-based participative research (popular epidemiology studies, etc..)
Creation of alternative reports/knowledge
Development of a network/collective action
Development of alternative proposals
Lawsuits, court cases, judicial activism
Media based activism/alternative media
Official complaint letters and petitions
Public campaigns
Environmental ImpactsVisible: Biodiversity loss (wildlife, agro-diversity), Food insecurity (crop damage), Soil contamination, Waste overflow
Potential: Genetic contamination, Air pollution
OtherImpacts of the domestic animals: cat, dog, pigs, and many deaths and illness continued for many years
Health ImpactsVisible: Other Health impacts, Exposure to unknown or uncertain complex risks (radiation, etc…), Other environmental related diseases, Deaths, Mental problems including stress, depression and suicide
OtherSymptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision and damage to hearing and speech. In extreme cases, insanity, paralysis, coma and death follow within weeks of the onset of symptoms. A congenital form of the disease can also affect fetuses.

-Specific impact to children
Socio-economic ImpactsVisible: Loss of livelihood, Loss of traditional knowledge/practices/cultures, Violations of human rights
Potential: Displacement
Project StatusStopped
Pathways for conflict outcome / responseCompensation
Court decision (victory for environmental justice)
Withdrawal of company/investment
Do you consider this as a success?Not Sure
Why? Explain briefly.Compensation came late, and in small amounts.
Sources and Materials

Bitter Sea: The Human Cost of Minamata Disease. Akio Mishima and Lester R. Brown (authors)
[click to view]

Toxic Archipelago: A History of Industrial Disease in Japan , Brett Walker (author)
[click to view]

Margaret Mckean, Environmental Protest and Citizens Politics in Japan, Univ of California Press, Berkeley, 1981

Hishashi Saito, Nigata Minamata Disease, 2009 (firsthand account of methyl-mercury poisoning in Japan is not only the heartrending story of a physician's passionate relationship to his patients, people whose symptoms become chillingly familiar, but also of his tireless pursuit of medical integrity and social justice).


Minamata Disease
[click to view]

Mercury rising: Niigata struggles to bury its Minamata ghosts. Prefecture on Japan Sea coast marks 50th anniversary of the official recognition of a disease caused by toxic materials with more questions than answers, by Rob Gilhooly
[click to view]

Still in 2016: In landmark ruling, court orders city of Niigata to recognize seven as Minamata disease victims, May 31, 2016. NIIGATA – A district court has ordered the Niigata Municipal Government to officially recognize seven people as sufferers of the Minamata mercury-poisoning disease.
[click to view]

Kazumasa Takemori, Niigata Minamata Disease and Showa Denko, 2012
[click to view]

Other Documents

Minamata Disease
[click to view]

Meta Information
ContributorGrettel Navas & JMA, EnvJustice Project
Last update01/12/2016
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