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updated 1/22/2004 9:55:02 PM ET 2004-01-23T02:55:02

Farmed salmon is more contaminated than wild salmon. A lot more, a large-scale study shows.

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The findings come from a well-respected group of researchers. The study analyzed more than two tons of salmon from fish farms, supermarkets, and wholesalers in Europe, North America, and South America.

But there's lots of disagreement over the most important questions: Is farmed salmon safe to eat -- and if so, how much?

Study researcher Jeffery A. Foran, Ph.D., is president of Citizens for a Better Environment, Milwaukee, Wisc., and faculty member at the University of Michigan School of Natural Resources and Environment. His family now eats wild instead of farmed salmon.

"People need to eat fish. Fish are good for you," Foran tells WebMD. "We hope this will simply get people to choose fish that are less contaminated. And we want industry and regulatory agencies to make fish safer."

But the FDA sees no problem with farmed salmon. Terry Troxell, pH, is director of the Federal Drug Administration's Office of Plant and Dairy Foods and Beverages.

"The FDA's advice to consumers is not to alter their consumption of farmed or wild salmon," Troxell tells WebMD. "Salmon is an excellent source of protein and omega-3 fatty acids. There is evidence that salmon is protective against cardiovascular disease. ... If anything we would like to see consumers eat more salmon."

The most highly contaminated salmon came from farms in Europe, the study shows -- especially Scotland. North American and South American salmon farms had a lot less -- but still more than wild salmon. The report appears in the Jan. 9 issue of the journal Science.

What's inside your salmon?
Foran and colleagues looked for 14 contaminants in salmon. These contaminants include PCBs and other dioxins and various pesticide residues. All are known or suspected causes of cancer, neurological problems, immune suppression, and/or hormonal disruption.

And they found them -- with concentrations in farmed salmon significantly higher than those in wild salmon for all 14 contaminants. These contaminants exceed what the U.S. Environmental Protection Agency deems safe levels for caught fish. But they are well under 25-year-old tolerance levels set by the U.S. FDA for bought fish.

The different safety levels reflect the two U.S. agencies different agendas. The EPA approach is designed to minimize health risks by providing risk-based consumption advice. The FDA approach -- and it's the FDA, after all, that regulates food -- is different. Mike Bolger, pH, is director of the FDA's division of risk assessment.

"We focus on controllable sources of dioxin-like contaminants in the diet," Bolger tells WebMD. "We became convinced that the most effective public-health approach is to find out how much of which contaminant is in what foods, and do something about it. A recent National Academies of Science report pretty much said the same thing and reaffirmed that what we are doing is pretty much on target. We have re-thought how to approach these ubiquitous contaminants. Talking about the tolerance is not going to be helpful."

Not everyone agrees with the FDA's approach. Just last month, a group of 26 scientists petitioned the FDA to establish new, stricter tolerance levels for environmental contaminants such as PCBs.

Still, levels of PCBs and pesticides in salmon have been steadily going down, says Alex Trent, executive director of the trade group Salmon of the Americas. Today, he says, PCB levels in U.S. fish are lower than they are in beef and whole milk. Even so, there's more work to be done.

The focus of this work is where the contaminants come from in the first place. Farmed fish are fed fish meal and fish oil. These products are made from small fish, and tend to concentrate any contaminants the smaller fish pick up. Trent says the industry already is reducing the amount of fish-based products used in salmon farming.

"PCBs have no place in fish," Trent tells WebMD. "The reason the PCB numbers are continuing to go down is we spend a lot of money sourcing fish oil and meal. If you work real hard at getting low-PCB oil, it goes down. We work as hard as we can on that. The other way we get down is moving away from fish oil and fish meal altogether. Twenty-five years ago, everything we fed salmon was fish. Today, it's 50% fish oil and meal, the rest vegetable and other nonPCB-contaminated feed. The industry spends literally millions of dollars -- and we will redouble those efforts -- to work on the right problems in the right sequence at the right time to feed more vegetable oil to fish. But there is a lot of work to be done on that."

What's your risk?
"All of these 14 contaminants pose risks to human health," Foran says. "We know there are significant health effects of these compounds that we didn't know about 25 years ago."

What to do would be a no brainer -- if salmon didn't also have enormous health benefits. Salmon's fatty acids significantly reduce a person's risk of heart disease. And recent research shows that they are enormously helpful to early child development when eaten by pregnant and nursing women.

These benefits far exceed the risks, argues food toxicologist Charles Santerre, pH, associate professor in Purdue University's department of foods and nutrition. He's also spokesperson for the Institute of Food Technologists, and recently began consulting work for Salmon of the Americas.

Santerre notes that some 250,000 people a year die of sudden cardiac death. If at-risk people ate a gram of fatty fish oils a day, he says, these deaths would be reduced by 40%.

"If you took 100,000 people and fed them 8 ounces per week of farmed salmon for 70 years, one person would get cancer from the contaminants," Santerre says.

"If this were extended to the entire U.S. population, that would mean a few thousand lives. How do you stack that up against a million lives saved every year? It is kind of like the seat belt. We know a few people die every year as a result of wearing a seat belt. Does that mean we want to stop recommending people wear seat belts? That is exactly what is happening here. This study points out that a few people can be injured by eating farmed salmon. But many, many, many times more will benefit from it."

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