Mercury in Seafood

U.S. Fish Advice May Expose Babies to Too Much Mercury

March 16, 2016

Mercury in Seafood: Executive Summary

To protect your baby from toxic mercury and ensure his or her healthy development, you should not only watch how much fish you eat, but what kind of fish.

Federal agencies advise women who are pregnant, nursing or planning to become pregnant to eat much more seafood, an excellent source of the omega-3 fatty acids essential to babies’ development. The most recent draft recommendations from the Food and Drug Administration and the Environmental Protection Agency say these women should eat eight to 12 ounces of fish and shellfish a week – more than twice as much as the average American.

The agencies also list fish they say are lower in mercury, a powerful neurotoxin harmful to the developing brains of fetuses, babies and young children. The aim is to encourage seafood consumption without overdoing the mercury. Among almost all experts, in recent years this goal has supplanted the once-prevailing view that to avoid mercury pregnant women should eat less fish or even cut it out of their diet altogether.

“When you eat seafood during pregnancy, you get the benefits from omega-3s but from mercury you have the risk of toxicity,” said Dr. Philippe Grandjean, an adjunct professor at the Harvard School of Public Health. “If you get a little bit of mercury it can be offset by the omega-3s. But that means you don't get the full benefit of the omega-3s and other nutrients in seafood. So women should minimize mercury exposure because only then will they get the maximum benefit of seafood.”

Now a new EWG study finds that adhering to the federal government’s recommendations on seafood and mercury may be risky, potentially leading women to eat too much of the wrong kind of fish. Nationwide testing found that mothers who eat the species of fish in the amounts recommended by FDA and EPA risk exposing their babies to harmful doses of mercury while not providing them with enough healthy omega-3s.

EWG recruited 254 women of childbearing age from 40 states who reported eating as much or slightly more fish than the government recommends. A university lab tested samples of their hair, where mercury accumulates and reflects the level in the body as the hair grew.

Nearly three in 10 of the women had more mercury in their bodies than the EPA says is safe – a level many experts say is much too high for pregnant women. Almost 60 percent of participants had more mercury than a stricter limit recommended by Grandjean, who analyzed hair samples for EWG’s study, and scientists from two prestigious European institutions. The frequent seafood eaters had an average of 11 times as much mercury as a comparison group who eat seafood rarely, proving that the high mercury levels came from the fish rather than other sources.

Mercury emissions from coal-fired power plants and other industrial sources are carried by air and deposited on oceans and waterways. Bacteria convert it to methylmercury, the form that accumulates in fish and is most harmful to human health. In the U.S., an estimated 75,000 infants born each year are exposed in the womb to potentially harmful levels of mercury.

To limit mercury consumption, FDA and EPA recommend that women eat no more than six ounces a week of canned albacore tuna and no shark, swordfish, tilefish or king mackerel. But our study suggests that many women who follow that advice will not have low enough levels of mercury or get enough omega-3s in their diets.

Our analysis of the women's dietary surveys found that while only a small amount of their mercury intake came from species the government says to avoid or limit, the great majority of the toxin came from species the government does not warn against, especially tuna steaks and tuna sushi. And although the women in our study eat more than twice as much fish as the average American, almost 60 percent still don’t get the amount of omega-3s recommended during pregnancy from seafood in their diets.

In light of the tradeoff between mercury and omega-3s, and because seafood harbors other contaminants, some people believe it is safer to avoid fish completely during pregnancy. We don’t agree.

Researchers overwhelmingly recommend low mercury fish as the most reliable source of omega-3s.The mercury in seafood erodes the benefits of an otherwise healthy food, and in some cases tips the scale to the point that the fish becomes harmful. The tradeoff is like exercising outdoors even when the air quality is less than ideal: Air pollution erodes the benefits of outdoor exercise, but in most cases it is still worth it. If air quality is bad enough, you should stay indoors.

EWG and the Mercury Policy Project urge FDA and EPA to update their recommendations to specify the full list of low mercury-high omega-3 fish, such as salmon, that women should add to their diets. This information is already included in the most recent edition of the Dietary Guidelines from the Department of Agriculture and the Department of Health and Human Services, so aligning the recommendations would provide greater clarity to the government’s advice, which doctors and other health professionals look to for guidance.

The advice should also educate women about the hazards of mercury and name additional species they should limit or avoid for up to a year before conception, such as seabass, halibut and marlin.

In the absence of government action, EWG’s Good Seafood Guide provides model guidelines for consumers looking to reduce intake of mercury consumption and increase intake of omega-3 fats. The EWG Seafood Calculator estimates portion size and frequency based on a child or adult’s weight and recommends that pregnant women and children ingest 25 percent less mercury than the current EPA guideline.