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How much mercury is in the fish you eat?

Recent analyses show that consuming fish tainted with mercury remains a concern for women and children. As such, health advocates say the government should do more to inform the public about risk.
Women of childbearing years should be careful about the kind of fish they eat because certain fish contain high levels of mercury, a chemical dangerous to a developing fetus.
Women of childbearing years should be careful about the kind of fish they eat because certain fish contain high levels of mercury, a chemical dangerous to a developing fetus.
/ Source: contributor

Eat plenty of fish, the American Heart Association and the American Dietetic Association advise. Two seafood servings per week, they say, provide a low-fat source of protein that could prevent heart disease, cancer, and many other illnesses. But an April 1 report in the Journal of the American Medical Association says consuming fish tainted with mercury may be dangerous for women and children, a finding that adds strength to past warnings.

Most American women and children do not carry dangerous levels of toxic mercury in their blood, the researchers say. Yet JAMA’s report reveals that 1 in 12 American women (8 percent) of reproductive age have levels above what the Environmental Protection Agency deems safe. They also found that women who ate three or more servings of fish within a 30-day period had four times the level of mercury as women who ate no fish during that period.

“This [finding] certainly warrants women pay attention to federal and state fish advisories and the varying mercury content in different fish,” says Susan Schober, an epidemiologist at the Centers for Disease Control and Prevention and a lead author of the JAMA study.

Mercury enters fish via pollution
Mercury enters the environment naturally and through industrial pollution, according to the JAMA study. Power plants that burn fossil fuels, such as coal, and waste incineration, pulp, paper manufacturing and other processes, generate the most mercury emissions.

Once mercury falls into lakes, rivers and oceans, fish and other creatures convert it to methylmercury, a potent neurotoxin.

By eating fish and shellfish, people are exposed to methylmercury, which is dangerous for women of childbearing age because the chemical can damage the brain and kidney of developing fetuses, research has shown.

The JAMA study adds weight to a report released in February by EPA, called “America’s Children,” which like the JAMA study was based on data from the CDC’s ongoing National Health and Nutrition Examination Survey.

The survey provided the most recent snapshot of mercury exposure in women and children. While the EPA looked at many aspects of children’s health, the JAMA study focused on mercury levels in the blood of 1,250 children and 2,314 women between 1999 and 2000. Besides reporting the 1 in 12 statistic, the EPA report also said states are increasingly issuing warnings of dangerous levels of mercury in fish.

Bush plan will increase mercury
Both these warnings come as Congress is poised to act on a Bush administration plan, called the Clear Skies Initiative, which will slow down the timetable for reducing the main source of mercury — emissions from coal-fired power plants.

Frank O’Donnell, director of the Clean Air Trust, an environmental lobby group, says the mercury data delayed for 10 months the release of the EPA report, which was made public after being leaked to the press.

“But people need to know the power industry is the biggest unregulated source of mercury and that tuna will continue to be risky as long as power plants continue to put out tons of heavy metals,” O’Donnell says. He says he fears war-dominated media coverage could allow the bill to be pushed through without notice.

”[All] the health data are worrisome enough that we should take steps to reduce mercury levels in fish and in the ambient environment through stricter emissions controls,” says John Balbus, environmental health director of the non-profit group Environmental Defense. “And we need to do a better job characterizing high-end exposures.”

Some fish have more mercury
Mercury builds up as it passes up the food chain, so longer-lived predatory fish such as shark, swordfish and others contain the highest amounts and are the biggest health threat. Mercury’s toxic qualities have been known for hundreds of years, but the risk to fish eaters was not fully recognized until more than a hundred people became ill from eating shellfish from water polluted with mercury from a local factory in Minimata, Japan, in the 1950s.

Currently, the Food and Drug Administration recommends pregnant women and those who could become pregnant avoid eating shark, swordfish, king mackerel and tile fish, all predatory fish known to contain elevated levels of methylmercury.

According to the JAMA report, people can still obtain the benefits of fish by staying away from predatory fish and instead consuming fish low in methylmercury, such as haddock, tilapia, salmon, cod, pollock and sole.

Public isn't informed sufficiently
However, some health advocates, such as Michael Bender of the Mercury Policy Project, in Montpelier, Vt., say the JAMA report findings showing such recent exposure to mercury in women raises the question of whether consumers have enough information to protect themselves. Eight percent of women corresponds to 325,000 babies born each year at risk of mercury poisoning, Bender says.

Bender charges that the FDA doesn’t test fish regularly, relies on outdated data for its advisories, has weaker standards for risk than the EPA and fails to publicize its information to consumers — particularly about tuna, one of the most popular and inexpensive seafoods.

Some doctors agree people should be better protected and informed about fish mercury. The California Medical Association passed a resolution in March saying the government needs to be more proactive in testing fish, in advising the public about mercury hazards, and in maintaining consistent risk standards across agencies.

California posts fish information
California began posting fish hazard information to consumers in January, forcing five grocery chains, Safeway, Kroger’s, Albertson’s, Trader Joe’s and Whole Foods, to warn customers that tuna, swordfish and shark sold in their markets contain mercury. Different states, however, provide conflicting information about what pregnant women should eat.

Dr. Jane Hightower, a San Francisco physician who introduced the California Medical Association resolution, had published a study in the April Environmental Health Perspectives, which revealed many of her patients showed high levels of mercury in their blood because of consumption of certain seafood.

Her study found Californians who ate presumable healthy — and, ironically, often pricey — fish meals wound up with very elevated mercury levels in their bodies. Of her 116 patients, 89 percent had mercury levels exceeding the 5 parts per billion level recognized as “safe” by the EPA and the National Academy of Sciences. More than half had blood mercury levels more than twice the level recommended.

With many people turning to seafood these days, Hightower feels more people probably are being adversely affected, and the government should better publicize findings about mercury’s health dangers with more specific advice on individual seafood varieties.

“There’s more advice when you buy your fishing license than when you go to buy fish,” she says. At the very least, she says, doctors should urge caution for women who are pregnant or who want to be.

David Acheson, chief medical officer in the Office of Science in the FDA’s Center for Food Safety and Applied Nutrition, says the agency is currently looking at ways to revise its methylmercury consumer advisory and may have a decision by the end of the year.

Francesca Lyman is an environmental and travel journalist and author of “Inside the Dzanga-Sangha Rain Forest” (Workman, 1998). She recently finished a report on the health effects of the Sept. 11 attacks titled “Messages in the Dust,” which will be available online at