Farmed salmon found to harbor toxins

Health risks from eating fish could offset benefits, international study says

January 09, 2004|By Heather Dewar | Heather Dewar,SUN STAFF

Farm-raised salmon, widely regarded as one of the healthiest meats on American tables, is a storehouse for toxins and may pose health risks that offset its benefits for some consumers, according to a new study by an international scientific team.

The study, based on a chemical analysis of more than two tons of salmon filets from three continents, found the fat-marbled flesh harbors as many as 14 dangerous man-made chemicals, including dioxin, PCBs and an assortment of long-lived toxic pesticides. The findings appeared today in the journal Science.

Researchers said eating more than one meal of farm-raised salmon a month could increase adults' lifelong risk of developing cancer, and might increase the risk of developmental and reproductive problems.

The American Heart Association recommends eating fatty fish such as salmon twice a week because they are rich in natural chemicals called omega-3 fatty acids that help protect against sudden heart failure.

One of the study's six authors said consumers must balance the risks of salmon against its benefits. He urged them to ask restaurants and fish markets where their salmon comes from, and to eat less-contaminated, wild salmon whenever possible.

"My advice would be not to eat farmed salmon if you think it's contaminated," said David Carpenter, director of the Institute for Health and the Environment at the State University of New York at Albany.

Unfortunately, that advice is hard to follow, according to dioxin expert Robert S. Lawrence of the Johns Hopkins Bloomberg School of Public Health.

"In local Baltimore restaurants, I see salmon on the menu and ask, `Is this farmed or wild?' and they almost never know," Lawrence said.

For people at high risk of heart disease, the benefits of any kind of salmon might outweigh the risks, Carpenter said. But girls and women of child-bearing age should be more concerned about chemical contaminants because there is evidence they can harm developing fetuses, Carpenter said.

"I would tell a mother not to eat farmed salmon," he said.

U.S. Food and Drug Administration officials rejected that recommendation. "We don't believe these findings are cause for concern," said Terry Troxell, director of the FDA's office of plant and dairy foods and beverages, which started a similar study.

Troxell said consumers "should not alter their consumption of wild or farmed salmon," since "there's evidence that fish consumption can prevent cardiovascular disease."

Michael Bolger, head of the FDA's office of risk analysis, disputed the new study's method for calculating the potential cancer risk. But independent experts from Harvard University and the Johns Hopkins University said the study's methods followed standard practices.

Salmon is the nation's third most popular seafood, after shrimp and tuna. According to the National Fisheries Institute, the average American ate more than two pounds of salmon in 2002. About half of the world's salmon is farm-raised and sold mostly as filets, while wild salmon are usually canned.

Salmon consumption is on the rise, in part because of its health benefits, government and private experts say. But for years many have wondered whether the fish contain potentially dangerous chemicals.

The chemical analyses required to answer that question can cost up to $700 per sample, so there has been little information to go on, Lawrence said. "That's why this study is so important," he added. "It's a major contribution to our knowledge."

The researchers tested 738 salmon filets from Europe, the United States, Canada and South America, looking for about 50 different substances, Carpenter said.

The most widespread were dioxins and PCBs - industrial chemicals known to increase cancer risks - along with pesticides known as organochlorines.

The most common organochlorines have been banned in the United States and other countries because they collect in the environment and remain poisonous for a long time.

Although they're becoming less common in the environment, almost all humans has measurable amounts of organochlorines in their bodies. Some are classified as carcinogens and some can affect production of hormones, scientists say.

There is growing agreement that these "endocrine disrupters" can affect developing fetuses and children, although the nature of their effects and the level of contamination that causes harm are debated.

Even more uncertain is the effect of chemical cocktails such as those found in salmon filets and in many other foods. James K. Hammitt, director of the Harvard University Center for Risk Assessment, said toxicologists assume that each chemical adds to the danger posed by the others. In reality, he said, they might multiply the harm or cancel each other out.

The Science study found that salmon contaminants seem to come from commercial fish feed, which is made from "trash fish" - species people dislike but captive salmon devour.

Many of the trash fish used in feed come from polluted coastal waters, Carpenter said. Wild salmon contained fewer chemicals at lower levels - probably because they eat different fish and shellfish than the captive salmon, Carpenter said.

Salmon from the world's most polluted waters, including Northern Europe's Baltic and North Seas, had the most contaminants. Those from cleaner Pacific waters - the source of most salmon sold in the United States - were the purest.

Lawrence said the study illuminates a disturbing pattern in the industrialized world's food supply. Just as bovine spongiform encephalopathy, or mad cow disease, is transmitted by body parts from diseased animals recycled into cattle feed, so the feeding of contaminated fish to other fish transmits and spreads danger, he said.

"We've got to look much more closely at what we're feeding to the animals that we're raising for human consumption."

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