THURSDAY, Jan. 8, 2004 (HealthDayNews) -- Chemical contaminants in farm-raised salmon are at unacceptably high levels and may dramatically increase the risk of cancer, a new report claims.
The key contaminant, polychlorinated biphenyl (PCB), has been banned in the United States since the late 1970s. It is among the "dirty dozen" chemical contaminants to be eliminated under the United Nations treaty on persistent organic pollutants. PCBs have been linked to cancer and impaired fetal brain development.
"Levels of 14 different chemical contaminates pesticides are higher in farmed salmon than in wild salmon," says co-researcher Dr. David O. Carpenter, a professor of environmental health and toxicology and director of the Institute for Health and the Environment at the State University of New York at Albany.
In the current study, the largest to date, Carpenter's team tested more than 2 metric tons of farmed and wild salmon from around the world.
They found farm-raised salmon had significantly higher PCB levels and many chlorinated pesticides than wild Pacific salmon. The researchers report the finding in the Jan. 9 issue of Science. High PCB levels in farmed salmon result from the fish meal and fish oil they are fed.
While these levels of PCBs are far below those called dangerous by the U.S. Food and Drug Administration (FDA), they are unsafe by the standards used by the U.S. Environmental Agency (EPA). FDA standards have not been changed since 1984.
The EPA sets acceptable levels for PCBs in wild salmon, and its 1999 updated standards are 500 times more protective than the PCB limits used by the FDA to rate fish sold commercially, according to a 2003 report on PCBs in salmon from the Environmental Working Group (EWG).
The EWG report notes new research shows the PCBs found in fish and people are more potent cancer-causing agents than originally thought.
Using the EPA standard, "to avoid an excessive risk of cancer, one should reduce consumption of farm salmon," Carpenter says. "On average, one meal of farmed salmon a month is what one should not exceed," he adds. "And some European farmed salmon should be eaten only once every four months."
The researchers suggest that because PCB levels in salmon vary throughout the world, the fish should be labeled "wild" or "farmed" and from where it came.
Carpenter notes the FDA's PCB limit is not health-based (it is a regulatory advisory), while the EPA limit is based only on health effects. "I hope the FDA and the EPA will come together and review the standards, because the present circumstance is confusing to the consumer."
Salmon, which is rich in omega-3 fatty acids, has been recommended as a food source that can significantly help reduce the risk of heart disease. Carpenter points out that omega-3 fatty acids are also in many other wild fish and in canola and flaxseed oil and soy.
More Americans are eating salmon and the annual worldwide production of farmed salmon over the past 20 years has increased by a factor of 40.
"We think that consumers should be overjoyed that farmed salmon are between 1 to 2 percent of the FDA tolerance for PCBs," says Alex Trent, executive director of Salmon of the Americas, an industry lobbying group. "There is absolutely no reason to be concerned about PCBs in salmon any more than there is in any other food."
Trent goes on to say the industry tolerance for PCBs is zero, and they are working to change the food mix given to salmon in hopes of eliminating PCBs altogether within five years.
Trent accuses the researchers and the Pew Charitable Trusts, which paid for the study, of having a political agenda. "The agenda is that they don't like farmed salmon for reasons that don't have to do with food safety," he says. Trent believes the real reason salmon farming is criticized is because of its environmental impact.
Carpenter says that the Pew Charitable Trusts has a "forceful position opposed to fish farming, because of the antibiotics used in feed and pollution of coastal waters."
"But it is not a position that we [the researchers] buy into. We have found the key for the salmon farming industry, which is clean up the food you feed to the fish, and the problem will go away."
Jane Houlihan, vice president for research at the Environmental Working Group, says this study confirms other studies that show that "it is not safe for people to eat regularly farmed salmon."
She notes that using the EPA standard, farmed salmon is safe to eat only about once a month. "Stay away from regularly eating farmed salmon," Houlihan advises. She recommends wild salmon as a good alternative.
PCBs have to be eliminated from farmed fish and the industry has to find ways to farm fish that do not degrade the environment, Houlihan says. It is time for the salmon farming industry to "clean up its act," she adds.
However, Dr. Mike Gallo, a professor of toxicology and public health at the Robert Wood Johnson Medical School, disagrees. He says the study confirms the safety of farmed salmon based on FDA standards.
Gallo believes the EPA standards are unproved and only hypothetical models. He also notes that PCBs are found in pork, lamb and beef, foods that Americans eat more often then salmon.
Gallo also believes there is a strong bias against fish farming by groups concerned with the environment.
Farmed salmon is much cheaper than wild salmon, making it more available to consumers, Gallo says. "I don't think Americans should change their diet based on this paper," he adds.
Dr. David Katz, director of the Yale Prevention Research Center at Yale University School of Medicine and author of The Way to Eat, says "there has long been concern that failure to feed farm-raised salmon the green algae their wild counterparts eat would deplete their flesh of health-promoting omega-3 fatty acids."
"There is evidence that this is occurring. Now we can add new evidence that we are not merely depleting vital nutrients, but replacing them with industrial byproducts," he says.
Katz adds that "overall, eating fish is health-promoting, and eating salmon can be particularly so. But it is increasingly important to know the source of those fish. Until or unless fish farmers step away from the transgressions of their counterparts on land, consumers should step away from their product, and ask for wild fish instead."