Fish is an excellent low-fat food and a great source of protein, vitamins and minerals. In Washington State, fish not only offer a tremendous source of nutrition, but catching, cooking and eating fish are important cultural and family practices. However, some fish contain high levels of a form of mercury, called methyl mercury that can be harmful to pregnant women, women of childbearing age and children under six.
Mercury occurs naturally in the environment. It can be released into the air as a result of volcanic activity. Mercury also comes from industrial pollution, especially burning of coal and other fossil fuels and from burning household or industrial wastes. Mercury compounds settle into sediments of lakes, rivers and oceans, where bacteria convert the inorganic mercury compound to methyl mercury. Fish absorb methyl mercury from water as it passes over their gills. Fish primarily absorb methyl mercury from the prey they eat.
Health problems caused by mercury are most severe for the developing fetus and for young children. Pregnant women who eat fish contaminated with large amounts of methyl mercury run the risk that their babies will have unhealthful changes in their central nervous system and possible in their heart or blood vessels. Nervous system changes can affect the baby’s ability to learn. In adults, methyl mercury can lead to problems of the central nervous system and possible adverse effects on the cardiovascular system.
The Food and Drug Administration has issued a “consumer advisory” to women of childbearing age, to avoid certain kinds of fish. The Centers of Disease Control and Prevention (CDC) and the Washington State Department of Health also support this advisory.