Mercury in Seafood

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

March 16, 2016

Mercury in Seafood: Where do government recommendations fall short?

The 2014 draft recommendations from FDA and EPA advise women who are pregnant, nursing or considering pregnancy to eat eight to 12 ounces of a variety of seafood a week.8 The draft retains the agencies' 2004 recommendations that such women completely avoid four fish high in mercury (swordfish, shark, king mackerel and tilefish), eat no more than six ounces of albacore tuna a week, and eat a maximum of 12 ounces of any other fish or shellfish a week. The draft names several “lower mercury” fish and shellfish, including salmon, canned light tuna, tilapia, cod and catfish. It cautions women and children to limit fish caught from local waterways that may be polluted with mercury or other harmful chemicals.

But our study shows that the government’s advice is not detailed enough.

Participants reported eating lots of tuna steaks and tuna sushi, as well as other fish with high levels of mercury that FDA and EPA don’t mention. Tuna contributed almost 40 percent of the mercury ingested by participants, based on their answers to the questionnaire. Other studies have estimated a similar contribution of tuna to mercury intake in the American diet.9 The inclusion of canned light tuna on the government’s "lower mercury" list is in error, since it is in fact not low in mercury and is a significant source of mercury in women’s diets.

Only About One-Sixth of Participants’ Mercury Intake is From Species the Food & Drug Administration Warns Women to Limit or Avoid During Pregnancy


Several other high mercury species contributed an additional 12 percent of participants' mercury intake. These include escolar, walleye and opah – species whose mercury levels are similar to those on the government’s "do not eat" list but are not named in the recommendations – and popular choices like halibut, snapper, seabass, grouper, ono and Spanish mackerel, all with mercury concentrations similar to canned albacore tuna. EWG recommends that pregnant women and children avoid eating these fish whenever possible. 

The FDA and EPA recommendations also fail to ensure that women get enough omega-3s. As EWG reported in 2014, eight of the 10 most popular seafood species are too low in omega-3s to be good sources of those fatty acids during pregnancy.10 FDA recommends tilapia and catfish as “lower mercury” species. But a pregnant woman would need to eat about 15 servings of tilapia a week, or 20 servings of catfish, to get the recommended amount of DHA+EPA.

In contrast, wild salmon stands out as a healthy and also popular choice. A single six-ounce serving of salmon can provide an entire week’s worth of omega-3s and is very low in mercury. Our participants eat a lot of salmon and we estimate it provides almost half of the omega-3s in their diets. Small oily fish such anchovies, herring, sardines and shad made up very few of participants' seafood meals but provided almost 15 percent of their omega-3s.

Confusingly, there is another set of federal guidelines for seafood. The recommendations from FDA and EPA are concerned with seafood consumption during pregnancy, while the official Dietary Guidelines of the Department of Health and Human Services and the Department of Agriculture are overarching recommendations about nutrition and health.

The newest Dietary Guidelines, published in January 2016, say all adults (not just pregnant women) should eat eight to 12 ounces of seafood a week. They conclude that people who get an average of 250 milligrams a day of DHA+EPA from seafood have lower risk of dying from heart disease, and consumption during pregnancy leads to improved infant health outcomes.

The Dietary Guidelines provide better detail to help consumers choose fish that are low in mercury and high in omega-3s, listing salmon, anchovies, herring, shad, sardines, Pacific oysters, trout and Atlantic and Pacific mackerel. They advise people to eat these species often to get the benefits of omega-3s.

Many state agencies are also providing their residents with better guidance on seafood safety. For example, California, Connecticut and Washington give clear and practical information about both mercury and omega-3s in commercial fish species.11 FDA and EPA should follow the states’ lead.