Farmed Salmon Found to Contain Cancer Causing Toxics

BLOOMINGTON, Indiana, January 8, 2004 (ENS) - Toxic chemicals are present at higher levels in farmed salmon than in wild salmon, according to new research released today that warns of health risks to people who consume salmon produced on fish farms more frequently than once a week. Farmed salmon is what most people eat in the United States when they choose salmon because it is cheaper than wild salmon and available all year round.

Researchers at Indiana University and five other research centers conducted the most comprehensive analysis to date of the concentrations of environmental contaminants in salmon. Their findings appear in this week's issue of the journal "Science."

"We think it's important for people who eat salmon to know that farmed salmon have higher levels of toxins than wild salmon from the open ocean," said Indiana University Bloomington School of Public and Environmental Affairs Distinguished Professor Ronald Hites, who led the study.

Ronald Hites specializes in applying organic analytical chemistry techniques to the analysis of trace levels of potentially toxic environmental pollutants. (Photo courtesy IU)

Using a standard method known as gas chromatographic high-resolution spectrometry, the researchers found that with very few exceptions, farmed salmon samples tested significantly higher for concentrations of 14 organochlorine toxics.

The toxics they studied were polychlorinated biphenyls (PCBs), dioxins, toxaphene, dieldrin, hexachlorobenzene, lindane, heptachlor epoxide, cis-nonachlor, trans-nonachlor, gamma-chlordane, alpha-chlordane, Mirex, endrin and total DDT.

Many of these chemicals, including PCBs, dioxins and toxaphene, are each "reasonably anticipated to be a human carcinogen," according to a recent report by the U.S. Department of Health and Human Services.

Hites and his colleagues also measured toxic levels in "salmon chow," a mixture of ground up fish and oil fed to salmon raised in farms. They found a strong correlation between the toxicities of chow and the salmon that ate it, suggesting the toxics are passed into the farmed salmon from their feed.

Salmon being reared in a net cage (Photo courtesy British Columbia Salmon Farmers Association)

Only four of the 14 chemicals tested - PCBs, dioxins, dieldrin and toxaphene - were used to calculate human consumption safety guidelines, because these four chemicals most strongly impact human health, the researchers said.

Levels of PCBs, dioxins, toxaphene and dieldrin were highest in farmed salmon from Scotland and the Faroe Islands (Denmark) and lowest in farmed salmon from Chile and Washington state, though Hites pointed out that even these comparatively uncontaminated South American salmon had high levels of other toxics.

The salmon samples from Scotland were so contaminated with PCBs, dioxins, dieldrin and toxaphene that no more than three meals of Scottish farmed salmon per year are recommended.

To determine recommendations for human consumption, the researchers applied U.S. Environmental Protection Agency fish consumption advisory methods, which are stricter than the standards established by the U.S. Food and Drug Administration (FDA).

Farmed salmon purchased for the study from supermarkets in Frankfurt, Edinburgh, Paris, London, Oslo, Boston, San Francisco, and Toronto triggered consumption recommendations of one-half to one meal of salmon per month. A meal is defined as eight ounces of uncooked meat.

Farmed salmon from supermarkets in Los Angeles, Washington, DC, Seattle, Chicago, New York and Vancouver triggered a recommendation of no more than two salmon meals per month.

British Columbia farmed salmon products (Photo courtesy British Columbia Salmon Farmers Association)

Wild salmon were found to be much less contaminated and can be consumed at levels as high as eight meals per month, the scientists advise.

While the health benefits of eating salmon have been established by numerous studies, concerns about the fish's tendency to accumulate toxics have gone largely unaddressed, Hites says. As fish eaters themselves, salmon occupy high positions in their food chains and store in their flesh the toxic chemicals from the fish they consume.

Don Staniford of Scotland's Salmon Farm Protest Group, said, "Given the cocktail of chemicals, artificial colorings and contaminants, Scottish farmed salmon should surely carry a government health warning rather than being sold as a safe, healthy and nutritious foodstuff."

Supermarkets have a duty of care to their customers and should list what chemicals, contaminants and artificial colorings farmed salmon contains, said Staniford. "The Salmon Farm Protest Group urges consumers to count to ten and think again and list 10 reasons to boycott fresh farmed salmon.

In Vancouver, the David Suzuki Foundation says the Hites team's results Science support a pioneering study the foundation conducted three years ago.

In 2001, the foundation reported that potentially dangerous levels of toxic chemicals are contained in the feed given to farmed salmon in Canada and Europe. “While European farmed fish are worse, Canadian farmed salmon are still a potential health risk,” says Otto Langer, the foundation's director of marine conservation.

Dr. David Bates, former dean of medicine at the University of British Columbia, is an international expert on pollution. He warned today that there is a serious risk to health from ingesting contaminants such as PCBs in our everyday diet.

“Studies have shown that PCBs have a remarkable ability to potentiate cancer,” Bates says. “The European Union and the World Health Organization have set acceptable levels and this was done after analysis of an array of scientific studies. Unfortunately, Canadian levels are much less stringent and the Canadian government has been lax in dealing with this issue.”

The BC Salmon Farmers Association (BCSFA) interpreted the study as confirming that both farmed and wild salmon are safe to eat. In this and previous studies, levels of contamination in salmon test well below health and food safety standards set by the Canadian Food Inspection Agency, the U.S. Food and Drug Administration and the World Health Organization, the salmon farmers association said.

“Consumers can be confident that both wild and farmed remain one of the best protein choices we have today,” said Mary Ellen Walling, BCSFA executive director. “Salmon is a safe and healthy food choice, and the salmon aquaculture industry has an important role to play in the development of a vibrant and sustainable seafood industry in British Columbia.”

Tugboat works net cages at a Maine salmon farm. (Photo courtesy Salmon of the Americas)

"Meal and oil for fish feed are formulated from the least contaminated sources possible," said SOTA, adding that the industry has reduced fishmeal and oil use by over 60 percent in the past decade with the substitution of vegetable sources.

SOTA Executive Director Alex Trent says the organization has asked FDA Commissioner Mark McCellan to reconcile the recommendations of various federal agencies on salmon consumption. Several organizations and individuals have used risk assessment data out of context and without any reference to corresponding benefit information and this has caused consumer confusion, he says.

Trent adds, "It is unfortunate that environmental contaminants are so widespread that they appear in food at any level. However, if consumers get past the scare headlines and look at the facts, they will see that salmon is typically 1/100 of the FDA tolerance for PCBs and that the benefits greatly outweigh the risks."

Heart disease is the number one killer of Americans, and the omega-3 fatty acids found in salmon protect humans against heart disease. For this reason, health officials say the benefits of eating even farmed salmon outweigh the risks of consuming carcinogenic chemicals. The American Heart Association advises eating fish at least twice a week because it helps prevent heart disease and is low in harmful mercury found in tuna and other large fish.

The researchers say they are not warning people away from eating fish, just away from eating farmed fish.

"Ultimately, the most important determinant of risk has to do with where the fish is farmed not where it is purchased," said Dr. David Carpenter, an author of the study and Director of the Institute for Health and the Environment at the University at Albany. "And because it's a global market, it's hard to be sure what you're getting."

To make it easier for consumers to follow the consumption advice identified in the study, the authors recommend that all farmed and wild salmon be clearly labeled and that the country of origin also be displayed.

Jeffrey Foran of the University of Michigan, M. Coreen Hamilton of AXYS Analytical Services Ltd., as well as Barbara Knuth and Steven Schwager of Cornell University, and Amy Matthews Amos of Turnstone Consulting, in West Virginia also contributed to the study. It was funded by a grant to the University at Albany from the Pew Charitable Trusts' Environmental Division.