Long term exposure to mercury can result in symptoms that get progressively worse and lead to personality changes, stupor and coma. Children are more sensitive to mercury poisoning than adults, and are more likely to have serious effects from exposure to mercury vapor. Wildlife populations, especially loons, are already exhibiting effects of mercury poisoning. There is so much mercury pollution that 39 states, including Wisconsin, are currently warning residents not to eat certain species of fish caught in all or some of the state's lakes, rivers and streams. In pregnant women, mercury can pass through the placenta, where it affects fetal development, by preventing the brain and nervous system from developing normally.
Affected children show lowered intelligence, impaired hearing and poor coordination.
Their verbal and motor skills may be delayed. Because of these threats to the developing fetus, the federal government recommends that women who are pregnant or who may become pregnant not eat mercury-contaminated fish.