In light of concerns about mercury-tainted fish that have been in the news lately

In light of concerns about mercury-tainted fish that have been in the news lately, which fish are safer to eat than others?

—Renee Scott, via e-mail

As mercury pollution from industrial facilities becomes more pervasive in both ocean and freshwater environments, consumers need to limit their intake of both freshwater fish and seafood, whether they catch it themselves or buy it in a supermarket or restaurant.

More than 3,000 water bodies nationwide were under fish consumption advisories in 2003, an increase of almost 10 percent over the previous year, according to the U.S. Environmental Protection Agency (EPA). Aquatic predators toward the top of the food chain—such as swordfish, shark, king mackerel, tilefish, pike, walleye, largemouth bass, white sucker, yellow perch and albacore tuna—are most likely to carry large amounts of mercury. Environmentalists recommend avoiding eating such fish altogether.

Meanwhile, shrimp, salmon, pollock, catfish, and canned light tuna do not accumulate as much mercury in their systems, and as a result may be safer to eat in moderation. Nevertheless, the EPA recommends that consumers limit their intake to 12 ounces (2 average meals) per week of any fish.

Each year, U.S. power plants and other industrial facilities spew as much as 150 tons of mercury or more into the air as a by-product of production processes. Eventually the mercury makes its way into nearby waterways and accumulates in the tissue of fish.

Exposure to mercury can be particularly hazardous for pregnant women and small children, according to the Natural Resources Defense Council. During the first several years of life, a child’s brain is still developing and rapidly absorbing nutrients. Prenatal and infant mercury exposure can cause mental retardation, cerebral palsy, deafness and blindness. Even in low doses, mercury may affect a child’s development, delay walking and talking, shorten attention span and cause learning disabilities.

In adults, mercury poisoning can adversely affect fertility and blood pressure regulation and can cause memory loss, tremors, vision loss and numbness of the fingers and toes. A growing body of evidence suggests that exposure to mercury may also lead to heart disease.

A January 2003 report from the federal Centers for Disease Control and Prevention concluded that one in six women of childbearing age have mercury in their blood above the level that would pose a risk to a developing fetus. The good news for consumers who have eaten large amounts of fish in the past is that they can significantly lower the mercury content in their bloodstreams by cutting consumption now.

CONTACTS: Environmental Protection Agency Fish Advisories Page, http://www.epa.gov/waterscience/fish/; Natural Resources Defense Council’s Mercury Contamination in Fish: A Guide to Staying Healthy and Fighting Back, http://www.nrdc.org/health/effects/mercury/index.asp.