Following hard on the heels of recent public protests over contaminants in farmed salmon, two new reports confirm previous concerns about toxic organochlorides (PCBs, dioxin) and pesticides (malachite green) in farmed salmon.

The PCB/Dioxin Dilemma
Writing in the January 9, 2004 issue of the respected journal Science, researchers at U.S. and Canada universities and laboratories reported on their tests of two metric tons of wild and farmed salmon from wholesalers and retailers around the world. They tested for toxic pollutants called organochlorides—a group of chemicals linked to cancer and infant developmental defects, which includes polychlorinated biphenyls (PCBs), dioxin, and certain pesticides. The Science study is the first large, rigorous examination of persistent toxic pollutants in salmon*.

As the authors wrote: "¼ we show that concentrations of these contaminants are significantly higher in farmed salmon than in wild. European-raised salmon have significantly greater contaminant loads than those raised in North and South America ¼ Risk analysis indicates that consumption of farmed Atlantic salmon may pose health risks that detract from the beneficial effects of fish consumption."

Here are the highlights of the study, and the response by the U.S. Food and Drug Administration (FDA):

• Farmed salmon carry up to ten times more cancer-causing chemicals than their wild counterparts. The average dioxin level in farmed salmon was as 11 times that found in wild salmon, or 1.88 parts per billion (ppb) versus 0.17 ppb. For PCBs, the average was 36.6 ppb in farmed salmon versus 4.75 in wild salmon.
• Farmed salmon in Scotland and the nearby Faroe Islands had the most contaminated samples, followed by fish from North American farms. (Note: Wild chinook salmon caught near-shore in Puget Sound contain similarly high levels of toxins, which is why we only purchase salmon caught far offshore. We also have an independent lab test our salmon regularly—see graph below.)
• Based on U.S. Environmental Protection Agency (EPA) guidelines, the study’s authors suggest that people shouldn't eat farm-raised salmon more than once a month.
• The main source of PCBs in farmed salmon is the fish oil that constitutes a large part of their feed. Small "forage fish" (e.g., herring) are processed into salmon farm chow. (Salmon in U.S. farms are also fed recycled fat from slaughtered livestock, including cows.)
• To reduce the problem, fish farmers should substitute soybeans or flaxseed for fish protein and livestock fat.

However, the FDA’s advice seems dubious at best, since salmon’s fat provides most of its flavor and all of its beneficial omega-3 fatty acids. In addition, the organochlorides people consume in farmed salmon merely compound the risks from comparably high levels of organochlorides found in many other foods—especially butter, poultry and red meats—and no one knows what, if any, amount of organochlorides is safe to eat.

British salmon faces ban over persistent pesticide abuse
You may recall that we reported on the alarming contamination of Chilean and British salmon by a dye called malachite green, used as a fungicide on the eggs of farmed fish. Britain’s Food Standards Agency admits to the safety risks, and a US safety panel is expected to soon declare malachite green a proven carcinogen that also causes genetic mutations.