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By MARTIN MITTELSTAEDT
Globe and Mail
17th May 2002
A Canadian researcher who has found elevated levels of PCBs in British Columbia farmed salmon has published a scientific paper saying that eating as little as one meal a week of the fish could be dangerous.
The finding is based on one of the first studies to look at contaminant levels in farmed fish, which are raised in pens along the seacoast and fed fishmeal pellets made of the processed remains of other aquatic creatures.
Michael Easton, a Vancouver geneticist who led the study, said the farmed salmon he tested had far higher levels of most contaminants than wild fish. The farmed fish contained nearly 10 times the toxic load of some types of PCBs, or polychlorinated biphenyls, as wild salmon.
Using World Health Organization standards for PCB exposure, Mr. Easton's paper estimates that Canadians should not eat more than one to three meals of farmed salmon a week, although it says that under Health Canada's far laxer exposure standards an intake of 20 to 138 portions a week is considered safe.
"Depending on whether you are a child or not, you would be advised not to eat farmed salmon as frequently as one meal a week," Mr. Easton said.
Women of childbearing age and children are most susceptible to the risks of PCBs. The chemicals have been linked to immune-system suppression and reduced mental development in children among other deleterious effects. Because PCBs are extremely toxic, governments are trying to eliminate them from the food chain. Even trace exposures worry some researchers.
Margot Geduld, a spokeswoman for Health Canada, said federal standards for PCBs are under review.
Mr. Easton's data and findings were published February in Chemosphere, an international science journal that specializes in environmental chemistry.
Although most contaminant levels were found to be higher in the penned salmon, the human-raised fish had one benefit: They contained less mercury than their wild cousins.
Mr. Easton said farmed fish have high residues of toxic compounds because the feed used to fatten the fish and promote their rapid growth is laced with PCBs. After testing the salmon feed for the pollutants found in the farmed fish, he discovered that the levels of contamination were very similar.
"The use of fish oil and fishmeal in feed serves not only to produce high-energy feeds with good growth performance qualities, but also to act as a pipeline for contaminants into the human food chain," the paper concludes.
Mr. Easton said his tests are preliminary because they included only eight fish and five feed samples. He called for more research to determine whether his findings can be applied throughout the industry and to see whether wild salmon stocks in heavily polluted areas also carry excessive chemical burdens.
The Canadian Food Inspection Agency disputes the view that farmed fish contain enough PCBs, dangerous oily chemicals once used in electrical equipment, to pose a human health hazard.
However, the agency has quietly been testing fishmeal for the same industrial contaminants such as PCBs, mercury and DDT studied by Mr. Easton's team, and hopes to make its findings public next week on its Web site.
"We have found levels that are in a range where they're unlikely to pose human health risks," said Linda Webster, a toxicologist at the agency.
Although the agency says the fishmeal is safe, Canada has no standards on the amount of PCBs allowed in it or other products fed to fish and livestock. Ms. Webster said the agency's tests will help in the development of national safety levels.
She added that the government has found contaminants in fishmeal that were "lower but not totally out of whack" with what Mr. Easton and his group discovered.
Mr. Easton said the fishmeal eaten by the penned salmon could come from anywhere, including Third World regions where DDT is still used and PCBs are not regulated tightly. This means that even though the compounds are banned in Canada, they could be getting into domestic food supplies from foreign sources.
Mr. Easton tested four fresh farm-raised salmon purchased at B.C. markets, four wild salmon bought frozen from a Vancouver company and five fishmeal samples obtained from the companies that supply them.
He announced some of his initial PCB findings last year.
The tests needed to determine contaminant levels were expensive, ranging from $3,000 to $4,000 per fish.
The research was financed by the David Suzuki Foundation, a Canadian environmental organization. Mr. Suzuki used preliminary data from the research in a television program about salmon last year
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