Signs and symptoms include ataxia, numbness in the hands and feet, general muscle weakness, loss of peripheral vision, and damage to hearing and speech.

[1] This highly toxic chemical bioaccumulated and biomagnified in shellfish and fish in Minamata Bay and the Shiranui Sea, which, when eaten by the local population, resulted in mercury poisoning.

In 1908, the Chisso Corporation first opened a chemical factory in Minamata, Kumamoto Prefecture, located on the west coast of the southern island of Kyūshū.

Initially producing fertilisers, the factory followed the nationwide expansion of Japan's chemical industry, branching out into production of acetylene, acetaldehyde, acetic acid, vinyl chloride, and octanol, among others.

[14] As a result of the catalyst change, this highly toxic compound was released into Minamata Bay regularly between 1951 and 1968, when this production method was finally discontinued.

On 4 November, the research group announced its initial findings: "Minamata disease is rather considered to be poisoning by a heavy metal, presumably it enters the human body mainly through fish and shellfish.

The company's own tests revealed that its wastewater contained many heavy metals in concentrations sufficiently high enough to bring about serious environmental degradation, including lead, mercury, manganese, arsenic, thallium, and copper, plus the chalcogen selenium.

The highest concentrations centred around the Chisso factory wastewater canal in Hyakken Harbour, decreasing as it went out to sea, clearly identifying the plant as the source of contamination.

[23] The Chisso factory's hospital director, Hajime Hosokawa, established a laboratory in the research division of the facility to carry out his own experiments into Minamata disease in July 1959.

Seventy-eight days into the experiment, cat 400 exhibited symptoms of Minamata disease, and pathological examinations confirmed a diagnosis of organic mercury poisoning.

[26] On 29 August, the fishing cooperative agreed to the mediation committee's proposal, stating: "In order to end the anxiety of the citizens, we swallow our tears and accept".

In fact, the wastewater from the factory, which the company knew still contained mercury and led to Minamata disease when fed to cats, was not being treated through the Cyclator at the time.

Testimony at a later Niigata Minamata disease trial proved that Chisso knew the Cyclator to be completely ineffective: "The purification tank was installed as a social solution and did nothing to remove organic mercury.

This was inaccurate - much activity on the part of the patients and fishermen took place during this period, but nothing had a significant impact on the actions of the company or the coverage of Minamata in the Japanese media.

Despite the almost universal assumption to the contrary, the wastewater treatment facilities installed in December 1959 had no effect on the level of organic mercury being released into the Shiranui Sea.

The Kumamoto and Kagoshima prefectural governments conducted a joint survey in late 1960 and early 1961 to measure the level of mercury in the hair of people living around the Shiranui Sea.

In 1961, a number of medical professionals, including Masazumi Harada (later to be honored by the United Nations for his body of work on Minamata disease), set about re-examining children diagnosed with cerebral palsy.

A founding member of the citizens' council was Michiko Ishimure, a local housewife and poet who later that year published Pure Land, Poisoned Sea: Our Minamata disease, a book of poetic essays that received national acclaim.

Many felt vindicated in their long struggle to force Chisso to accept responsibility for causing the disease and expressed thanks that their plight had been recognised by their social superiors.

[33] In light of the government announcement, the patients of the Mutual Aid Society decided to ask for a new compensation agreement with Chisso and submitted the demand on 6 October.

Their report, Corporate Responsibility for Minamata Disease: Chisso's Illegal Acts,[36] published in August 1970, formed the basis of the ultimately successful lawsuit.

Former factory manager Eiichi Nishida admitted that the company put profits ahead of safety, resulting in dangerous working conditions and a lack of care with mercury.

Former Chisso President Kiichi Yoshioka admitted that the company promoted a theory of dumped World War II explosives, though it knew it to be unfounded.

The verdict handed down on 20 March 1973 represented a complete victory for the patients of the litigation group: The defendant's factory was a leading chemical plant with the most advanced technology and ... should have assured the safety of its wastewater.

They required that patients must exhibit all symptoms of Hunter-Russell syndrome – the standard diagnosis of organic mercury poisoning at the time, which originated from an industrial accident in the United Kingdom in 1940.

The issue of quantifying the impact of Minamata disease is complicated, as a full epidemiological study has never been conducted and patients were recognised only if they voluntarily applied to a certification council to seek financial compensation.

[44] The Institute seeks to improve medical treatment of Minamata disease patients and conducts research on mercury compounds and their impact on organisms as well as potential detoxification mechanisms.

The Scottish writer Sean Michael Wilson and Japanese artist Akiko Shimojima collaborated on the book, called The Minamata Story: an ecotragedy, which was published in English by Stonebridge Press, and went on to win two awards.

Smith was himself attacked and seriously injured by Chisso employees in an incident in Goi, Ichihara city, near Tokyo on January 7, 1972, in an attempt to stop the photographer from further revealing the issue to the world.

Hot House members are also involved in raising awareness of Minamata disease, often attending conferences and seminars as well as making regular visits to elementary schools throughout Kumamoto Prefecture.