Farm-raised salmon, a growing staple of American diets, contains significantly higher concentrations of PCBs, dioxin and other cancer-causing contaminants than salmon caught in the wild and should be eaten infrequently, according to a new study of commercial fish sold in North America, South America and Europe.
The study, using Environmental Protection Agency health guidelines, concluded that while consumers could safely eat four to eight meals of wild salmon a month, consumption of more than one 8-ounce portion of farmed salmon a month in most cases poses an "unacceptable cancer risk."
People in Seattle, Chicago, New York, Los Angeles and Washington should not eat farmed salmon more than once or twice a month, the study advises. Store-bought samples from Frankfurt, Germany; Edinburgh, Scotland; Paris; London; and Oslo, Norway, were generally the most contaminated, while samples from stores in New Orleans and Denver were the least contaminated.
The two-year, $2.4 million study, funded by the Pew Charitable Trust and published Thursday in the journal Science, is the latest blow to the commercial fish industry, already suffering from growing concerns about elevated levels of mercury in tuna and shellfish.
Officials of the Food and Drug Administration and the fishing industry immediately took issue with the findings. They said the contaminant levels in salmon have declined by 90 percent since the 1970s and the remaining "trace levels" do not warrant consumers denying themselves the high protein and cardiovascular health benefits of eating salmon.
"We’ve looked at the levels found … and they do not represent a health concern," said Terry Troxell, director of the FDA’s Office of Plant and Dairy Food and Beverages. "In the end our advice is not to alter consumption of farmed or wild salmon."
On average, farmed salmon has concentrations of health-threatening contaminants 10 times greater than those found in wild salmon, according to the study. EPA guidelines say that if a person eats fish twice a week, it should contain no more than 4 to 6 parts per billion of PCBs. The study found that PCB levels in farmed salmon sold in the United States and Canada averaged about five times that amount: 30 parts per billion.
Consumers may have difficulty distinguishing between farmed and wild salmon because many stores and restaurants don’t clearly label them. Wild salmon generally is more expensive, but some retailers confuse the issue by identifying farmed salmon as "Atlantic salmon."
Farmed fish contain higher concentrations of contaminants than wild fish largely because they are fed a meal that consists of ground-up fish tainted with the contaminants, while wild salmon feed on smaller fish and tiny aquatic organisms.
Salmon of the Americas, an industry group representing farmed salmon producers in the United States, Canada and Chile, described salmon as an unparalleled source of omega-3 fatty acids for prevention of coronary heart disease, and noted that contaminant levels for both North and South American wild and farmed salmon are well below FDA and World Health Organization limits.
Alex Trent, the group’s executive director, said his industry doesn’t discount some of the health problems associated with PCB contamination of farmed salmon. However, he said, meat and dairy products, when eaten in large quantities, pose similar problems, and consumers would be foolish to deny themselves the health benefits of salmon.
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