Avoiding Mercury in Fish

Topic Overview

What is mercury?

Mercury is a metal found naturally in the environment. Human activities, such as farming, burning coal, and using mercury in manufacturing, increase the mercury cycling through the air, water, and soil. In water, mercury changes its form and becomes methylmercury. Fish absorb this mercury. When you eat fish containing mercury, you absorb the mercury, and at high levels it can be harmful. Mercury will leave the body over time in the urine, feces, and breast milk.

Do you need to avoid the mercury found in fish?

For most people, the level of mercury absorbed by eating fish and shellfish is not a health concern. Overall, fish and shellfish are healthy foods. They contain high-quality protein and other essential nutrients, are low in saturated fat, and contain omega-3 fatty acids, a type of essential fatty acid. A balanced diet that includes fish and shellfish can contribute to heart health and children's growth and development.

Nearly all fish and shellfish contain traces of mercury. However, some contain high levels. Eating large amounts of these fish and shellfish can result in high levels of mercury in the human body. In a fetus or young child, this can damage the brain and nerves (nervous system).

Because of the mercury found in fish, the U.S. Food and Drug Administration (FDA) and U.S. Environmental Protection Agency (EPA) advise the following people to avoid eating fish high in mercury and to eat limited amounts of fish and shellfish that are lower in mercury:

• Women who may become pregnant
• Pregnant women
• Nursing mothers
• Young children

If you are concerned about your or your child's mercury level, talk to your health professional or local health department about testing.

How should you change your eating habits to reduce your exposure to mercury in fish?

The FDA and EPA recommend that women who may become pregnant, pregnant women, nursing mothers, and young children:^{1, 2}

• Do not eat shark, swordfish, king mackerel, or tilefish because they contain high levels of mercury. Large, long-lived, predatory ocean fish have the highest mercury levels.
• Eat no more than 6 oz (170 g) per week of canned albacore ("white") tuna, tuna steaks, lobster, halibut, and orange roughy. These types of fish contain more mercury than other types of fish. A 6-ounce serving is about the size of two decks of cards or two checkbooks.
• Eat no more than 12 oz (340 g) per week of fish and shellfish lower in mercury. This is two average 6 oz (170 g) meals. Fish lower in mercury include shrimp, canned light tuna (not albacore tuna), salmon, pollock, and catfish.

If no advice is available about the fish or shellfish you eat, eat no more than 6 oz (170 g) per week, and don't eat any other fish or shellfish during that week.

The fish used in fish sticks and the fish sandwiches sold at fast-food restaurants are generally lower in mercury.

Should a woman who is not planning a pregnancy be concerned?

Mercury accumulates in your bloodstream over time and slowly leaves the body through urine, feces, and breast milk. If you eat a lot of fish high in mercury, it may take up to a year for your mercury levels to drop after you stop eating the fish. If you decide to become pregnant or have an unplanned pregnancy, you may have high levels of mercury. While elevated levels of mercury usually do not cause significant health problems, they may affect a developing fetus. If you are of childbearing age, try to follow the guidelines above when eating fish.

Where can you get more information?

For specific information on:

• The amount of mercury in commercial fish, see www.cfsan.fda.gov/~frf/sea-mehg.html.
• The fish or shellfish caught by family and friends in your local lakes, rivers, and coastal areas, see www.epa.gov/waterscience/fish/states.htm.

For general information on mercury in fish, see:

• Your local health department or environmental agency.
• The EPA fish Web site at www.epa.gov/ost/fish.
• The EPA mercury Web site at www.epa.gov/mercury.
• The FDA seafood Web site at www.cfsan.fda.gov/seafood1.html.

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Author:	Shannon Erstad, MBA/MPH	Last Updated November 30, 2006
Medical Review:	Renée M. Crichlow, MD - Family Medicine Kirtly Jones, MD - Obstetrics and Gynecology
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