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 is a prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,227,496 (1 July 2019) and is the fifth-largest prefecture of Japan by geographic area at . Niigata Prefecture borders Toyama Prefecture and ...

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 Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industrial ...

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 The is a river in the Hokuriku region of Honshu, Japan. It is also called the Aga River or the Ōkawa River in Fukushima. The source of the river is Mount Arakai on the border of Fukushima and Tochigi. It flows to the north and meets the Ni ...

where it

bioaccumulate Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated ...

d up the food chain, contaminating fish which when eaten by local people caused symptoms including ataxia,

numbness Hypoesthesia or numbness is a common side effect of various medical conditions that manifests as a reduced sense of touch or sensation, or a partial loss of sensitivity to sensory stimuli. In everyday speech this is generally referred to as num ...

in the hands and feet, general muscle weakness, narrowing of the

field of vision The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments". Or simply, visual field can be defined as the entire area that can be seen when an eye is fixed straight at a point ...

and damage to hearing and speech. A total of 690 people from the

basin have been certified as patients of Niigata Minamata disease. Since the Niigata outbreak was the second recorded in Japan and occurred in the Lower

Basin, it is sometimes called or . It is one of the Four Big Pollution Diseases of Japan.

History

Discovery

The second outbreak of Minamata disease in Niigata Prefecture was discovered in a very similar way to the original outbreak in Kumamoto Prefecture. From the autumn of 1964 to the spring of 1965, cats living along the banks of the

had been seen to go mad and die: "...one cat ran into a small clay cooking stove containing burning charcoal. With the pupils of its eyes dilated, salivating, convulsing and uttering a strange cry, the cat breathed its last breath." These strange symptoms eventually began to appear in people, too. Professor Tadao Tsubaki of

Niigata University is a national university in Niigata, Niigata Prefecture, Japan. It was established in 1949 and has its major origins in Niigata Medical College (established in 1922) and in Niigata Higher School (established in 1919). It is one of the largest Jap ...

examined two patients in April and May 1965 and suspected Minamata disease. One patient's hair was found to have a mercury level of 390 ppm. On 31 May, he reported an outbreak of organic mercury poisoning in the Agano River basin to the prefectural government and made his findings public on 12 June.Harada, pp86-91

Investigation

Throughout 1965 and 1966, researchers from the Kumamoto University Research Group (that had been set up to investigate the original outbreak) and Dr. Hajime Hosokawa (the former

Chisso The , since 2012 reorganized as JNC (Japan New Chisso), is a Japanese chemical company. It is an important supplier of liquid crystal used for LCDs, but is best known for its role in the 34-year-long pollution of the water supply in Minamata, ...

hospital director) brought their significant experience from Minamata and applied it to the Niigata outbreak. Many lessons were learned from Minamata and the investigation into the cause of the outbreak proceeded much more smoothly than it had in Minamata. The prefectural government, Niigata University, citizen's organisations, and local people all worked together to uncover the cause. In March 1966, factory plant

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.

Response of Showa Denko

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.

Patients' lawsuit

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. 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. 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. 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 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 was a Japanese doctor and medical researcher. His most famous work covered the effects of Minamata disease, a type of severe mercury poisoning that occurred in the city of Minamata, Kumamoto Prefecture during the 1950s and 1960s. His publications i ...

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."Harada, p90

Notes

References

External links

{{Toxicology Minamata, Niigata Mercury pollution Niigata Political scandals in Japan Minamata, Niigata Minamata, Niigata Minamata, Niigata 1965 in the environment 1965 in Japan 1965 industrial disasters