Rich in heart-protective fats, salmon has become the favorite entrée of the health conscious, so much in demand it is farmed around the world. But environmentalists have fretted that fish farms also breed toxins, and in January the largest study of its kind revealed that farmed salmon often have dangerous levels of poisons like PCBs and dioxins.
Led by environmental health physician David O. Carpenter of the University at Albany (SUNY), scientists examined more than 700 farmed and wild salmon from North America, South America, and Europe, looking for 14 organochlorines thought to cause cancer and birth defects. All 14 were present in North American and European farmed salmon and in higher amounts than in wild specimens. South American farmed fish proved somewhat more palatable: PCB and dioxin concentrations were less elevated.
The source of the toxins appears to be fish food. Salmon are carnivores and thus are fed meal and oil derived from smaller fish. Organochlorines are fat soluble, so trivial amounts in small, plant-nibbling fish become concentrated in the fatty tissues of salmon. To protect their children, Carpenter suggests “women should avoid eating farmed salmon at all, from the day they are born through menopause.”
Using the cancer-risk assessment methods of the Environmental Protection Agency, he calculates that men can safely eat wild salmon as often as eight times a month but farmed salmon only once or twice a month. Carpenter says salmon from farms in Scotland and the Faeroe Islands are so contaminated they should not be eaten more than three times a year.
American salmon farmers strongly disagree, saying they meet Food and Drug Administration standards for organochlorines. FDA requirements are more permissive than the EPA’s, which govern wild fish. French farmers sued a public relations firm that publicized Carpenter’s study for allegedly colluding with Alaskan fishermen to undermine the market.