These changes can affect their ability to learn. In adults, mercury can lead to problems of the central nervous system and possible adverse effects on the cardiovascular system. While we don't want to scare people away from eating all fish, women who are, or who might one day become pregnant, should choose fish that are low in mercury. Methylmercury is the kind of mercury that contaminates fish. This contamination is bound to the fish muscle, so cutting off the skin and fat, filleting or preparing fish in a special way does not reduce mercury levels in the flesh of fish.
Mercury contamination is a worldwide problem that comes from many sources.
It occurs naturally in rocks, soils, water and air. Volcanoes may also be a source of mercury in the environment. Industrial pollution is also a source of mercury in the environment. Burning fossil fuels like coal and burning industrial or household wastes releases mercury into the air. This settles onto oceans, lakes and rivers where fish absorb it.