Environment: Endangered Great Lakes

For 20 years, U.S. and Canadian industries have dumped millions of pounds of toxic mercury into the Great Lakes watershed. Now the result has caused alarm in both countries. On the heavily fished Lake Saint Clair, recent tests of pike and pickerel showed mercury levels as high as seven parts per million—14 times the maximum level deemed safe in fish for human consumption.

Last month local officials in the U.S. and Canada totally banned fishing on Lake Saint Clair and partly banned it on Lake Erie. Last week Interior Secretary Walter J. Hickel ordered a federal investigation of all lethal substances discharged...