Infants exposed before birth showed severe brain damage whereas their mothers had mild or no symptoms. The fetus is thought to be particularly sensitive during the first months of pregnancy when cell migration and cell division are occurring at a fast pace. Dr. Thomas Clarkson at University of Rochester points out that Iraqi infants exposed before birth showed symptoms when their pregnant mothers had daily intakes of 600 to 1100 nanograms per kilogram. Humans who eat a lot of freshwater fish seem to be, and so do fish-eating birds and mammals. Ocean fish seem not so susceptible to mercury buildup in their tissues, perhaps because the oceans are not acidic.
Freshwater fish are the problem.
Bass and other fish in the Everglades are definitely toxic enough to pose a real threat to predators such as ospreys, eagles and humans. Mercury has been confirmed as the cause of death in loons and panthers in the Everglades. Furthermore, mercury is suspected as an important cause of the reproductive failure being witnessed now among eagles, mink, otter and other wildlife in the Great Lakes. The mercury problem is heavily damaging the sport fishing industry in at least 22 states and at least two Canadian provinces, where warnings have been issued against eating certain species of fish from certain waters. And, as we have seen, the problem shows every sign of growing worse.