News Coverage
Study of farmed salmon opens a controversy
Published August 19, 2003
Casually picking up a fillet of farmed salmon from the supermarket seafood case just got more confusing.
This month, an environmental group released a study showing that farmed salmon harbored high levels of toxic PCBs. No one should eat the pen-raised fish more than once a month, the Environmental Working Group warned, and not at all if wild salmon with fewer of the contaminants could be bought.
The scoop on salmon, however, is not so clear cut and the report has unleashed a wave of controversy over how much is safe to eat. Two federal agencies have wildly disparate PCB fish consumption guidelines. Scientists argue whether the benefits of heart-healthy salmon outweigh the PCB exposure. Others beg for a little perspective: Even more commonly consumed foods -- butter and brown gravy among them -- have at times tested higher for PCBs than farmed salmon.
"Would I base my eating practices on this [study]? No," said Eric Rimm, associate professor of epidemiology and nutrition at the Harvard School of Public Health. He's concerned about the small sample size of the study -- 10 fillets -- and is attempting to get funding to test a much wider sampling of farmed fish.
There is little argument that PCBs (short for polychlorinated biphenyls) are dangerous toxins. Used for years as coolants in transformers, their US manufacturing was banned in the mid-1970s. Since then, the compounds have been linked to health problems from cancer to delayed child development.
Banning PCBs, however, didn't solve the problem. The compounds leak into the environment and can take years to break down. In the sea, small organisms ingest PCB-laden sediment while feeding. Fish then eat these organisms, accumulating more PCBs in their bodies. People who eat those fish can start to accumulate PCBs.
Farmed fish are a particular problem because they are fed ground-up fish that can have high levels of PCBs. As competition drives down prices of farmed salmon, the fish are becoming a regular part of many Americans' diet.
"We want this problem studied more," said Kristina Thayer, senior scientist for the Environmental Working Group. The non-profit group discovered an average of 27 parts per billion of PCBs in the fish they tested.
That limit is far below a Food and Drug Administration limit of 2,000 parts per billion in fish. Yet the Environmental Protection Agency recommends eating some recreationally caught fish that have PCB levels 25 to 48 parts per billion no more than once a month.
A senior FDA official said his agency is re-evaluating the current limit, but was adamant people should not change their eating habits because of the study. "The nutritional benefits far outweigh any leftover trace [of PCBs]," said Terry Troxell, of the FDA.
But others say PCBs are too dangerous to eat -- especially when other foods or fish can be substituted that reap the same benefit without the compounds. "People need to do whatever they can to reduce exposure," said David Carpenter, a professor in the Department of Environmental Health and Toxicology at the University of Albany.
Common sense will have to rule. But the salmon controversy has highlighted isolated cases of high PCB levels in other common foods. The FDA recently found two samples of butter, out of about several dozen, with levels more than twice that of farmed salmon in the recent study. One sample of canned tuna in oil and two samples of roasted chicken breast also showed elevated levels.
"We need balance, balance, balance," said K. Dun Gifford, founder and president of Oldways Preservation Trust, a dietary advocacy group that supports eating farmed fish. "Keep eating the salmon, just don't eat it seven days a week."