Toxic Tuna and Contaminated Cod

March 26, 2012

By Rachel Nuwer

Parents face a difficult decision when it comes to serving seafood at the dinner table: does the risk that fish contains toxic contaminants outweigh its nutritional benefits? TheEnvironmental Protection Agency and the Food and Drug Administration sometimes provide contradictory information about what quantities of seafood are safe to consume, and the extent of contamination for many populations and species of fish remains unknown.

Fish become contaminated in a variety of ways. Mercury, for example, can makes its way into an aquatic ecosystem from power plant runoff,. Rivers feed into the ocean, and so the contaminant finds its way into the marine ecosystem as well. Microbes change the element into methyl mercury, which travels up the food chain and bioconcentrates in larger and larger fish. Methyl mercury binds to muscles, while PCBs bind to fats. Hazardous waste sites may be dredged, but ultimately some contaminant traces will remain in the ecosystem and continue to diffuse into the ocean.

“People once thought of the ocean as being such a big, infinite source that we couldn’t possibly contaminate the whole thing, but that’s not true,” says David Carpenter, the director of the University at Albany’s Institute for Health and Environment. “We’ve really screwed up the ocean in a big way,” he says.

Fish can contain single toxins or multiple toxins. During an experiment with farmed salmon, Carpenter and his team found that dioxins, PCBs, and 12 other pesticides were all linked; if fish had concentrations of one chemical, they had concentrations of all 14. The scientists concluded that, in order to safely consume farmed salmon from Northern Europe, people should not eat it more than once every 5 months without increasing their risk of cancer. For children, that risk is even greater since studies indicate exposure to chemicals before birth or early in life can irreversibly reduce a child’s IQ.

But seafood is one of the best sources for omega-3 fatty acids, which some studies suggest plays important roles in neural development, immune function, and heart health. The U.S. Department of Agriculture recommends at least two servings of fish per week, while the United Kingdom Department of Health recommends one portion of white fish and one portion of oily fish (anchovies, sardines, salmon) per week, since oily fish have a higher proportion of omega-3s.

So, how to balance a healthy diet with safety? For now, a definitive guide to buying safe seafood does not exist, but organizations like Kids Safe Seafood can help provide guidance. Carpenter, who serves as a scientific advisor to the organization, suggests opting for smaller fish that are lower in the food chain, and also concentrating on shellfish and shrimp. Unfortunately, these animals contain fewer omega-3 fatty acids then foods like salmon, though salmon may have more contaminants.

Carpenter suggests skipping farmed salmon in favor of wild (especially favoring fish from the North Pacific) and going easy on tuna, since it contains high amounts of mercury. Selectively choosing light tuna over albacore or white tuna can help, though. Carpenter suggests putting farmed salmon, shark, swordfish, and king mackerel all on the no-eat list, and not serving other types of fish in excess.

Kids Safe Seafood lists anchovies, farmed arctic char, farmed Atlantic mackerel, farmed oysters, farmed rainbow trout, wild salmon, and wild sardines as sustainable species safe to feed to young children at least once a week.

“Responsible consumption doesn’t have to mean eliminating seafood from your diet, but rather selecting the right species for your family’s priorities and lifestyle,” says Simone Lewis-Koskinen of Kids Safe Seafood.

Chef and author Barton Seaver agrees, and has helped Kids Safe Seafood develop kid-friendly recipes, like his mackerel melt. “Canned tuna occupies such a seminal place in our pantries,” he says, “but there are quite a few concerns with tuna sustainability and toxicity.” To avoid these issues, he replaced tuna with smoked mackerel in a “comfortable favorite” dish, giving families a way to explore new options without stepping outside of their comfort zone. “The canned seafood aisle is stocked with a wade array of products that are highly sustainable, have manageable toxicity, and are delicious,” he says. In his own professional cooking, Seaver tends to prefer smaller species and filter feeders, avoiding toxicity by a quirk of personal taste.

Paul Greenberg, author of Four Fish: The Future of the Last Wild Food, is interested in developing safe, tasty seafood recipes for his own five-year-old. Knowing that his son would turn his nose up at most fish dishes, Greenberg developed an “I-can’t-believe-there’s-fish-in-there” spaghetti sauce recipe. The recipe calls for sardines, which can also be substituted with one 2-ounce can of anchovies. The fish dissolves into the tomato sauce, which also conceals the fishy flavor. Greenberg catches most of the fish his family eats, and limits his collection to small species on the low-pollutant, high-population scale, like mackerel.

“Getting Americans to eat any fish is always a good thing, especially versus red or even white meat,” Greenberg thinks, though he advocates for focusing on those species that are most sustainable and healthy.

Top Image Credit: Kenski1970, Flickr