Farmed salmon are laced with toxins, study finds

The Globe and Mail By Martin Mittelstaedt, Environment Reporter
With a report from Associated Press
Friday, Jan. 9, 2004

Farm-raised Atlantic salmon, one of the world's most popular health foods, are so laced with PCBs and other pollutants that they should be eaten only infrequently because they pose an increased risk of cancer, a new study contends in the prestigious journal Science.

Salmon from Toronto supermarkets were so contaminated they shouldn't be eaten more than once every two months, while those from Vancouver were safe to eat only once a month, according to the study. Similar consumption limits, based on tests on 700 salmon purchased from nearly 40 locations around the world, were made for European and U.S. cities.

Researchers blamed the feed used on fish farms for concentrating ocean pollutants. The study, being published today, is the most extensive ever done on industrial contaminants in farmed salmon.

Wild salmon were also studied but given a clean bill of health -- they have much lower levels of pollutants and could be eaten up to eight times a month.

The findings are sure to add to the intense controversy over salmon farming, where thousands of the carnivorous fish are raised in ocean pens and fattened up on a diet of the ocean equivalent of processed food -- pellets of fish meal made from the ground up remains of such forage species as anchovies.

Both Health Canada and Canadian Food Inspection Agency officials disputed the need for consumption restrictions. "In Canada , the fish is safe," said Glenn McGregor, seafood inspector for the CFIA. "Health Canada has been trying to promote fish as a healthy alternative for protein, certainly not trying to restrict its intake." Industry officials echoed government concerns. The U.S. Food and Drug Administration also insisted that the levels of pollutants in farm-raised salmon are too low for serious concern and urged Americans not to let the new research frighten them into a diet change.

In addition, the study tested salmon raw, with the skin on. Removing the skin and grilling it removes a significant amount of PCBs, dioxins and other pollutants stored in fish fat, the FDA said.

Salmon consumption has been rising rapidly in recent years because the fish is a rich dietary source of omega-3 fatty acids that reduce the risks of heart disease.

Most of the salmon consumers encounter in supermarkets come from farms off the coasts of Northern Europe, Canada , the United States and Chile.

Farmed salmon production has risen about 40 fold over the past two decades to more than a million tonnes a year. More than half of salmon consumed worldwide now comes from farm sources.

The new research compared levels of 14 chlorinated industrial pollutants -- such as dioxin, PCBs, and DDT-- in farmed salmon, with wild Pacific salmon caught off British Columbia and Alaska . The farmed fish had much higher contaminant levels, sometimes more than 10 times as much, as their wild ocean cousins.

"The really striking thing in our study is the number of compounds that are present in these fish," said David Carpenter, director of the Institute for Health and the Environment at the University at Albany, N.Y., one of the study authors.

Mr. Carpenter has personally given up eating farmed salmon, based on his research. The PCB level found in farmed salmon was up to about 50 parts per billion -- a tiny fraction of the FDA standards and Canadian federal guidelines of 2,000 parts per billion.

But Mr. Carpenter said the standard, developed in the 1970s, is out of date and the study's consumption advisories were based in part on a stricter level of 50 ppb used by the U.S. Environmental Protection Agency for assessing increases in cancer risk. Wild salmon generally had PCB concentrations of about 10 ppb or less.

Although the study didn't estimate the number of additional cancers that might be caused by farmed salmon, most health assessments are based on slight increases, such as a handful of extra cases among each 100,000 people.

Other common animal-derived foods also have PCBs, but Mr. Carpenter said levels in farmed salmon tend to be two to five times higher than in beef, pork, milk and eggs.

The researchers traced the contaminants to the food fed to the salmon. An analysis they conducted found that farmed salmon had similar pollutant levels to the fish meal they eat.

"We don't see any other obvious explanation [for the contaminants] because the fish are not feeding off the bottom," Mr. Carpenter said.

The fish used to make meal are absorbing the contaminants from their food and passing it along to the salmon. Mr. Carpenter said the aquaculture industry could clean up its product by switching to protein feeds based on plants, such as soybeans.

Canada currently doesn't have a regulatory standard for PCBs in fish meal, but the CFIA is considering imposing one. Most of the other compounds found in the fish do not have regulatory limits.

Up until now, the health benefits of farmed fish haven't been seriously questioned. Previous research has detected some pollutants in these salmon, but the number of fish tested was so few that scientists were uncertain about the wider significance of the findings.

Determining contaminants in salmon has not been widely done because of the prohibitive cost of the sophisticated tests needed for this research. It costs about $4,000 per fish to coax information on its pollution content from its tissues.

By sampling hundreds of fish weighing two tonnes in total, the new study, which cost $2.5-million ( U.S.), tried to overcome the problem of small sample size that undermined previous research. The fish were tested by AXYS Analytical Services in Victoria, one of the world's most sophisticated laboratories.

The study's conclusion about farmed salmon was hotly disputed by some researchers and by the aquaculture industry, which insists its product is wholesome.

"All the samples that we've seen have been way, way below [the regulatory] standard," said David Rideout, executive director of the Canadian Aquaculture Industry Alliance, a trade group.

Some nutrition experts also advised a cautious approach because the health benefits of fatty acids in the fish may outweigh the increased cancer risk suggested by the new research.

"I think that the risk part of that paper is well overstated. My advice to the North American public, probably the world's public, is to continue to eat the salmon," said Mike Gallo, a professor at the Robert Wood Johnson Medical School in New Brunswick , N.J.

How many meals?

A new study contends that farm-raised salmon are so full of PCBs and other pollutants that they pose a cancer risk if eaten often.

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