Niigata Minamata disease

Niigata Minamata disease 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. A total of 690 people from the Agano River 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 Agano River Basin, it is sometimes called Second Minamata disease or Agano River Organic Mercury Poisoning. It is one of the Four Big Pollution Diseases of Japan. 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 Agano River 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 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.