6 : WHAT HAS HAPPENED TO MINAMATA BAY?

The sludge in Minamata Bay with a mercury content above 25 parts per million (ppm), was dealt with by Kumamoto prefecture by dredging and reclamation, at the huge cost of 48.5 billion yen over 14 years. As a result, 58 hectares of reclaimed land was created in Minamata Bay. The water in Minamata Bay is said to be among the most clear and clean in Kumamoto Prefecture, and it is quite safe to swim and play in. In order to prevent the spread of polluted fish and reassure the residents of the prefecture, the prefecture placed nets around Minamata Bay in 1974, and enlisted the cooperation of the fishing cooperative to catch fish in the bay. These fish were then bought and disposed of by Chisso.

Mercury levels in fish and shellfish in Minamata Bay have continued to decrease since Chisso stopped its production of acetaldehyde in 1968, and a June 1994 survey by the prefecture confirmed that there are now no species of fish that average above the provisional national standards (0.4 ppm total mercury, 0.3 ppm methyl mercury). Therefore, the governor of Kumamoto declared Minamata Bay safe in July 1997, and the nets around the bay were removed in October. Now it can be said that the fish and shellfish in Minamata Bay are as safe as those in other regions.

After the removal of the nets, mercury levels in fish and shellfish continued to be tested twice a year for the next three years. Comprehensive data on the seas of Minamata, which experienced such large-scale environmental destruction, and on the health of the local residents, will be passed on to the rest of the world so the most can be made of the lessons of Minamata disease. For this purpose, long-term monitoring is desirable.

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