Salmon or no?

Last week, a study published in the journal Science showed that farm-raised salmon have higher levels of PCBs and other contaminants than their wild counterparts. While the finding could mean that consumption of farmed salmon poses an increased health risk, such a possibility must be set against many uncertainties and potential benefits.

Scientists found PCB concentrations of 36.63 parts per billion in farm-raised salmon, compared to 4.75 parts per billion in wild. The Food and Drug Administration’s (FDA) standard for PCBs in salmon is 2,000 parts per billion, 55 times higher than those found in the farmed fish, but the Environmental Protection Agency is far more restrictive.

Still, it is far from certain if higher levels of PCBs mean an increased risk of cancer. PCBs have not been shown to cause cancer in humans, and in animals, some non-carcinogenic PCBs have been shown to block other carcinogenic PCBs. “No one is really sure how important these interactions are in the real world,” said Mark Hahn, a toxicologist at Woods Hole Oceanographic Institute. Even the Science study acknowledged, “The potential risks to human health remain unclear.”

Moreover, those risks must be set against the benefits salmon consumption has in reducing cardiovascular disease, which remains the leading cause of death in America. Not eating salmon means substituting something else. However, few foods — flesh or fruit — are completely free of potential carcinogens. While the dose does not always make the poison, it is often a part of the equation.

The source for the higher levels of PCBs appear to be the feed fed to farmed fish. Industry scientists are working on ways to reduce such contaminants and should continue to do so.

In the meantime, consumers will have to decide for themselves if the health benefits of farmed salmon outweigh its potential risks. They may simply wish to pay a premium for wild salmon. Terry Troxell, the FDA’s director of the office of plant and dairy foods and beverages said, “Our advice to consumers is not to alter their consumption of farmed or wild salmon.” On balance, that seems reasonable advice.