Agano River
In 1965, a number of patients in Niigata Prefecture exhibited signs of Minamata disease. Niigata Minamata was caused by methylmercury poisoning in the Agano River basin. However, this second outbreak of Minamata disease was discovered early on. The degree of this outbreak was minimal compared to that of the first Minamata disease that took place in Kumamoto prefecture. Investigation of the cause of the disease was given to the Niigata University medical department. There were a number of factors that could be the cause of this outbreak. Along the Agano River basin there were several plants that used mercury in production, agricultural chemicals were widely used in the area, and the last possible cause of the outbreak was said to be the cause of an earthquake that took place a year before the disease was discovered in Niigata.