Ontario Minamata disease

Ontario Minamata disease is a neurological syndrome caused by severe mercury poisoning. It occurred in the Canadian province of Ontario, in 1970, and severely affected two First Nation communities in Northwestern Ontario following consumption of local fish contaminated with mercury, and one First Nation in Southern Ontario due to illegal disposal of industrial chemical waste. The disease was named after the infamous case of severe mercury poisoning in the fishing community of Minamata, Japan, which became known as Minamata disease because it devastated only the residents of the community.

In 1962, Dryden Chemical Company began operating a chloralkali process plant in Dryden, Ontario using mercury cells. It produced sodium hydroxide and chlorine that were used in large amounts for bleaching paper during production by the nearby Dryden Pulp and Paper Company. Both companies were subsidiaries of the British multinational, Reed International.

Dryden Chemical Company discharged their effluent directly into the Wabigoon-English River system. In 1970, extensive mercury contamination was discovered in this river system, leading to closure of the commercial fishery and some tourism related businesses. On March 26, 1970, the Ontario provincial government ordered Dryden Chemical Company to cease dumping mercury into the river system, although the order did not place any restrictions on airborne emissions of mercury by the company. It was estimated that over 9,000 kg of mercury had been dumped by the company into the Wabigoon-English river system between 1962 and 1970. The airborne emissions of mercury continued unabated until the company stopped using mercury cells in its chloralkali process in October 1975; the company closed down in 1976.

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