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Contaminants in Farm Raised Salmon Suggest Restrictions in Consumption
(Beyond Pesticides, January 12, 2004) A study published in the January 9th issue of Science (vol. 303, 2004) found significantly higher levels of cancer-causing and other health-related contaminants in farm raised salmon than in their wild counterparts. Concentrations of several cancer-causing substances in particular are high enough to suggest that consumers should consider severely restricting their consumption of farmed salmon, according to the study's authors. Analyzing fillets from about 700 farmed and wild salmon produced in eight major farmed salmon producing regions around the world and purchased in 16 large cities in North America and Europe, the study, "Global Assessment of Organic Contamination in Farmed Salmon," is the largest and most comprehensive study done to date. Four substances that have been well studied for their ability to cause cancer - PCBs, dioxins, dieldrin and toxaphene were consistently and significantly more concentrated in farmed salmon as a group.

In most cases, as detailed in the study, consumption of more than one meal of farmed salmon per month could pose unacceptable cancer risks according to U.S. Environmental Protection Agency (EPA) methods for calculating fish consumption advisories. The majority of salmon served in restaurants and found on grocery store shelves is farmed rather than wild.

Among the study's conclusions, salmon farmed in Europe were generally more contaminated than farmed salmon from North or South America. Farmed salmon purchased for the study from supermarkets in Frankfurt, Edinburgh, Paris, London, and Oslo were the most contaminated and triggered consumption recommendations of four to eight ounces per month - based on U.S. EPA consumption advisories for these contaminants.

Farmed salmon purchased from supermarkets in Los Angeles, Washington, D.C., Seattle, Chicago, New York, and Vancouver triggered a recommendation of no more than 16 ounces per month. There was slightly more variation in fish purchased in North America than those purchased in Europe. While farmed salmon purchased for the study in New Orleans and Denver were generally least contaminated - triggering a recommendation of about 24 ounces, or three meals, per month - farmed salmon purchased in Boston, San Francisco, and Toronto triggered the more stringent consumption recommendations of the European-purchased 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." According to Carpenter, "Just because Europeans have the most contaminated farmed salmon, this doesn't mean American consumers shouldn't be concerned."

With very few exceptions, farmed salmon samples tested significantly exceeded the contaminant levels of wild salmon, which could be consumed at levels as high as 8 meals, or 64 ounces, per month. Even the least contaminated farmed salmon, from Chile and the state of Washington, had significantly higher levels of PCBs, dioxins, and dieldrin than wild salmon.

The Pew-sponsored study concluded that the contamination problem is likely related to what salmon are being fed when they're on the farm. While wild salmon eat a diverse buffet from small aquatic organisms like krill to larger fish, farmed salmon are fed a concentrated and high fat mixture of ground up fish and fish oil. And since chemical contaminants a fish is exposed to during its life are stored in its fat, the higher fat "salmon chow" passes along more of these contaminants to the farmed salmon.

Given the overall contaminant levels found, if these were locally caught fish instead of fish purchased commercially EPA and many state consumption advisories would suggest that consumers restrict their consumption of farmed salmon to an average of no more than one eight once meal per month. However, consumers need to be aware that in some cases even that could exceed advised contaminant exposure levels. EPA's consumption advisories use acceptable lifetime risk levels to identify the maximum number of fish meals per month that can be safely eaten.

"If anything, the study conservatively estimates the health risks from the contaminants in farmed salmon," said the University at Albany's Carpenter. The EPA fish consumption guidelines don't take into account exposures people have to the same cancer-causing substances from all other sources in the environment. "They assume," said Carpenter, "that fish consumption is the only source of exposure people have to these substances; and we know that's not true." "Also," according to Carpenter, "the recommendations only consider the risk of cancer and don't take into account the neurological, immune, and endocrine system effects that have been associated with these contaminants."

Consumers interested in knowing whether salmon is wild or farmed should be aware that the word "Fresh" on the label does not mean the salmon is wild-caught from the ocean. And any salmon labeled "Atlantic" in the U.S. and in other countries is most likely farmed. The authors recommended that governments require clear and prominent labeling of farmed and wild salmon as well as the country of origin of all farmed salmon.

The authors also said their results strongly reinforced the recommendations of a July 2003 National Academy of Sciences report on dioxins in the food supply which called for reducing dioxin levels in animal feed such as fishmeal. Since contaminants build up in the fatty tissue of the fish, the authors point out that consumers may be able to reduce their consumption of contaminants in farmed salmon by following the recommendations of many state governments and the federal government to remove as much skin and visible fat as possible. However, it is difficult to determine how much of the contaminant load can be removed in this way.

In assessing the human health risks of consuming farmed salmon, the authors of the study used U.S. EPA consumption guidance for PCBs, toxaphene, and dieldrin covering locally caught fish rather than U.S. Food and Drug Administration (FDA) standards for these substances governing commercially-sold fish because EPA's recommendations are based on health effects only. While FDA is the agency that actually regulates contaminants in commercial fish, unlike EPA FDA does not have consumption standards for toxaphene in fish, and the agency's standards for PCBs and dieldrin weren't set using purely health-based criteria. According to Dr. Barbara Knuth of Cornell University and one of the study's authors, "Because the FDA regulatory levels take into account factors such as effects on the food production system, they were never designed to consider exclusively human health risk-which was the only concern we were looking at in this study."

"Plus," said Knuth, "the health and diet information and the technology FDA used to help set the regulatory levels for PCBs are 20 years out of date. We can detect PCBs at much lower levels today; new studies provide more information about the health risks associated with these substances; and people eat more fish today." Knuth said, "It's this vast difference in the approach of the two agencies that explains why farmed salmon with these levels of contaminants could trigger such restrictive consumption recommendations based on EPA methods, but is still allowed to be sold legally in the U.S. by the FDA."

The annual global production of farmed salmon has increased 40 times during the last two decades - making inexpensive salmon available to consumers year-round. Between 1987 and 1999, salmon consumption increased at an annual rate of 14% in the European Union and 23% in the U.S. Since 2000, over half of the salmon eaten globally has been farmed, coming primarily from fish farms in Northern Europe, Chile, and Canada.

Source: University at Albany's Institute for Health and the Environment, http://www.albany.edu/ihe/salmonstudy/index.html.