Closing down of the pollutant sources
With regard to the Minamata plant of Chisso Co., Ltd., through the completion of the perfect circulation system in 1966, water effluent containing methylmercury compound had not been discharged outside of the plant in principle, and the pollutant source was eliminated through cessation of the production of acetaldehyde in 1968. In the Agano River basin the process of producing acetaldehyde had already closed before Minamata Disease was discovered.