Mercury is a naturally occurring metal found throughout the environment. Everyone has at least small amounts of mercury in their body from environmental exposure and dietary consumption, including fish. The limited health risks of mercury in seafood should be balanced with the health benefits of fish in your diet.
Mercury Basics
Mercury occurs naturally in the ground, air, water and all living organisms. Increased mercury is also released into the environment by mining, burning coal, incinerating waste and manufacturing plants. Medical and dental materials, industrial chemicals, and preservatives can also contain mercury. Toxicity is determined in part by the method of exposure and which chemical form of mercury is involved. Bacteria in soil and water convert mercury into an organic form called methylmercury, which then enters the food chain.
Mercury in Fish
Fish absorb the methylmercury produced by bacteria as they feed, building up increasing mercury levels the longer they live and the higher up the food chain they are. This mercury buildup occurs normally at low levels but can be significantly increased in bodies of water with high mercury levels from pollution. Fish and shellfish are the major sources of mercury exposure in the United States, but they do not represent a health problem for most people, according to the U.S. Environmental Protection Agency.
Health Effects of Methylmercury
The health effects of methylmercury in fish depend on the amount consumed, the duration of exposure, and your age and health status. Fetuses, infants and children are most at risk for impaired brain and neurologic development. These long-term toxic effects can result in impairment of cognitive thinking, memory, language and fine motor skills. At higher levels of methylmercury exposure, all age groups can show symptoms such as impaired vision; loss of coordination; muscle weakness; and pain and tingling of the hands, feet and around the mouth. No significant allergic reactions to methylmercury in food are reported.
General Dietary Recommendations
Fish is widely considered a healthy food with recognized benefits. It is a high-quality protein source, low in saturated fat and a source of omega-3 fatty acids. Long-term monitoring of mercury levels in seafood by the U.S. Food and Drug Administration and EPA has led to recommendations for safety, including consuming fish and shellfish in a balanced diet while still reducing exposure to the health risks of methylmercury. Following these recommendations is especially important for young children and women of childbearing age.
Specific Recommendations
The 2004 FDA/EPA Consumer Advisory regarding consumption of fish and shellfish includes a few simple recommendations. Avoid shark, swordfish, king mackerel and tilefish because of their high mercury levels. Eat two meals of fish or shellfish a week for the health benefits, choosing from known low-mercury species such as shrimp, salmon, pollock, catfish and canned light tuna. If eating fish you caught yourself, check local advisories on the body of water the fish came from for guidance concerning possible mercury exposure.
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