Minamata disease, Japan

Minamata disease is caused by methylmercury poisoning. The name comes from Minamata Bay in Kumamoto prefecture where the Chisso factory released industrial waste. During 1932-1968 local residents, especially fisher families, suffered the consequences.

Minamata disease is a neurological syndrome caused by severe mercury poisoning.  The name corresponds to the name of the Minamata Bay in Kumamoto prefecture where the disease was first identified. During 1932-1968 local residents, especially fisher families have been suffering from a variety of symptoms. The cause (recognized in 1958) was the release of methylmercury in the industrial waste by Chisso Corporation Factory over a period of 36 years.  In this sense, the disease was caused by the consumption of heavy metals which the victims ingested through contaminated fish.  Fishermen demanded compensation for fishing families to damage to fishing grounds . Fishermen demanded 100.000.000 Y but they only receive 35.000.000 Y (less than 100.000 $). On 2 November 1959 the fishermen stormed the Chisso factory, destroying machinery. The riot police arrested them. The regional labour union and the citizens of Minamat sided with the Chisso company, at this point. Chisso was ready to pay some compensations but refused legal liability, until a court case was started years later.  Minamata disease symptoms 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 foetuses in the womb. The Minamata disease was first discovered in Minamata city in 1956. It was caused by the release of methylmercury in the industrial wastewater from the Chisso Corporation's petro-chemical and plastics factory, which continued from 1932 to 1968. The company dumped an estimated 27 tons of methylmercury into the Minamata Bay over a period of 37 years. Mercury was used as a catalyst in the production of acetaldehyde, a chemical employed in the production of plastics.This highly toxic chemical bioaccumulated in Minamata Bay and the Shiranui Sea, which was then eaten by the local populace resulting in mercury poisoning. At first doctors were unable to diagnose the cause of the disease, then in 1959, doctors at Kumamoto University determined that organic mercury poisoning was the cause of the symptoms exhibited by so many of the townspeople. Only in 1968 however did the Tokyo government acknowledge that the mercury dumping by Chisso was the ultimate cause. Five years later, Chisso admitted legal responsibility. It was proven that Chisso withheld critical information in 1959 and continued to dump waste. The government also supported the company and they were not held legally liable for their negligence until 1972. Chisso stopped production of acetaledyde in 1968--when an alternative technology for producing plastics was developed. As of March 2001, 2,265 victims had been officially recognised (1,784 of whom had died) and over 10,000 had received financial compensation from Chisso. Over $611 million has been paid to victims in compensation [2]. In 1977, the Japanese government cleaned up the bay by vacuuming up 1.5 million cubic meters of mercury-contaminated sludge. After $359 million dollars and 14 years, the project was completed in 1997. [1] Chisso still operates in Minamata and now produces chemicals, fertilizer. The local population has declined by 70% since its peak.
Basic Data
NameMinamata disease, Japan
ProvinceKumamoto prefecture
SiteMinamata Bay
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
Plastics, Methylmercury
Project Details and Actors
Project Details
The Chisso Minamata factory first started acetaldehyde production in 1932, producing 210 tons that year. By 1951 production had jumped to 6,000 tons per year and reached a peak of 45,245 tons in 1960.
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Type of PopulationSemi-urban
Potential Affected Population 2,265 certified victims
Start Date04/1956
Company Names or State EnterprisesChisso Corporation from Japan
Relevant government actorsKumamoto and Kagoshima prefectural government, Kumamoto University, Ministry of Health and Welfares Minamata Food Poisoning Subcommittee, Minamata Mayor, Todomu Nakamura, Ministry of International Trade and Industry and the Japan Chemical Industry Association
Environmental justice organisations and other supportersDouglas McAlpine., The Chisso factory hospital director, Hajime Hosokawa., The Minamata Fishing Cooperative., Masazumi Harada., Eizo Watanabe., Kumamoto District Court., Minamata Disease Patients Families Mutual Aid Society.
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 MobilizingFishermen
Industrial workers
Local ejos
Local government/political parties
Social movements
Trade unions
Local scientists/professionals
The Minimata Fisherman's Union
Forms of MobilizationCommunity-based participative research (popular epidemiology studies, etc..)
Creation of alternative reports/knowledge
Involvement of national and international NGOs
Lawsuits, court cases, judicial activism
Official complaint letters and petitions
Public campaigns
Street protest/marches
Occupation of buildings/public spaces
establishment of a mutual aid society for victims, sit-ins at Chisso headquarters and a tent settlement in front of the office in Tokyo
Environmental ImpactsVisible: Biodiversity loss (wildlife, agro-diversity), Surface water pollution / Decreasing water (physico-chemical, biological) quality
Potential: Food insecurity (crop damage), Groundwater pollution or depletion
Health ImpactsVisible: Accidents, Exposure to unknown or uncertain complex risks (radiation, etc…), Mental problems including stress, depression and suicide, Deaths, Other environmental related diseases, Other Health impacts
OtherMinamata disease produced by methylmercury
Socio-economic ImpactsVisible: Loss of livelihood, Specific impacts on women
Potential: Loss of traditional knowledge/practices/cultures, Militarization and increased police presence, Violations of human rights
Project StatusStopped
Pathways for conflict outcome / responseCompensation
Environmental improvements, rehabilitation/restoration of area
Institutional changes
Court decision (victory for environmental justice)
New legislation
Strengthening of participation
Project cancelled
Strengthening of democracy
Do you consider this as a success?Yes
Why? Explain briefly.According to Timothy S. George (2002), the environmental protests that surrounded the disease appeared to aid in the democratization of Japan. When the first cases were reported and subsequently suppressed, the rights of the victims were not recognised, and they were given no compensation. Instead, the afflicted were ostracised from their community due to ignorance about the disease, as people were afraid that it was contagious.

The people directly impacted by the pollution of Minamata Bay were not originally allowed to participate in actions that would affect their future. Disease victims, fishing families, and company employees were excluded from the debate. Progress occurred when Minamata victims were finally allowed to come to a meeting to discuss the issue. As a result, postwar Japan took a small step toward democracy.

Through the evolution of public sentiments, the victims and environmental protesters were able to acquire standing and proceed more effectively in their cause. The involvement of the press also aided the process of democratization because it caused more people to become aware of the facts of Minamata disease and the pollution that caused it.

Although the environmental protests did result in Japan becoming more democratized, it did not completely rid Japan of the system that first suppressed the fishermen and victims of Minamata disease.
Sources and Materials

Concerning the Compensation Act and Prevention of Damage to Health As Impact of Pollution (Law No. 111 of 1973)

Temporary Measures Law Relating to Labor Facilitation Certification of Minamata Disease (Law No. 104 of 1978)

Compensation Act (Criterion, 1977)

Extraordinary Measures Law for Victims Relief and Solution of the Problem of Minamata Disease (Act No. 81 of 2009

Law Concerning Payment of Costs of Preventive Work against Pollution by Pollutants (Law No. 133 of 1970

Extraordinary Measures Law Concerning the Relief Health Damage caused by Pollution (Act No. 90 of 1969)


'Minamata Disease: The History and Measures', The Ministry of the Environment, (2002), retrieved 17 January 2007.

[1] McCurry, J. (2006). Japan remembers minamata. Lancet, 367(9505), 99-100.

Ishimure, Michiko. 1990. Paradise in the Sea of Sorrow. English translation by Livet Monnet. Yamaguchi Publishing House (c/o Japan Publications Trading Co., Ltd., Tokyo).

Margaret Mckean, Environmental Protests and Citizen Politics in Japan, University of California Press, Berkeley, 1981


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[2] The Poisoning of Minamata, Douglas Allchin
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Enseñanzas de la Enfermedad de Minamata y el Manejo del Mercurio en Japón
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Timothy George's book , Minamata. Pollution and the Struggle for Democracy in Postwar Japan, 2002.
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ContributorDesireé Torrente
Last update29/11/2016