University at Albany Institute
for Health and the Environment

A Global Assessment of Organic Contaminants in Farmed vs. Wild Salmon: Geographical Differences and Health Risks

A Summary

Background

The annual global production of farmed salmon has increased 40-fold during the last 20 years. As a result, salmon from salmon farms in Northern Europe, North America, and Chile are available to consumers year-round and at relatively low prices. Between 1987 and 1999, salmon consumption increased at an annual rate of 14% in the European Union and 23% in the U.S. Since 1998, over half of the salmon sold globally has been farmed. Click here for more salmon production and consumption data.

While the health benefits of eating fish are well documented, previously only three small peer-reviewed studies have examined the relative concentrations of toxic contaminants in farmed vs. wild salmon. The results of these studies were inconclusive because they examined only a few fish (between 8 and 14) from a few locations.

Findings

Analysis of salmon fillets from about 700 farmed and wild salmon produced in eight major farmed salmon producing regions and purchased in 16 large cities in North America and Europe found significantly higher concentrations of contaminants in farmed salmon than in their wild counterparts. The study, which was sponsored by the Pew Charitable Trusts, focuses largely on the elevated concentrations of four contaminants because of the abundant health risk information for these compounds and because the patterns of their occurrence are similar to patterns of all contaminants evaluated in the study: PCBs, dioxins, dieldrin, and toxaphene.

In general:

  • Total PCBs, dioxins, dieldrin, and toxaphene were consistently and significantly more concentrated in the farmed salmon as a group than in the wild salmon.

  • Farmed salmon from Europe were more contaminated than farmed salmon from North or South America. The most contaminated farmed samples came from Scotland and the Faroe Islands in the North Atlantic. The least contaminated farmed samples came from Chile and Washington State in the U.S. But these still had significantly higher contaminant levels than wild salmon.

  • Store-bought samples from Frankfurt, Edinburgh, Paris, London, and Oslo were generally the most contaminated. Samples from stores in New Orleans and Denver were the least contaminated. Store-bought samples from Boston, San Francisco, and Toronto had contaminant levels approaching those found in European cities. (Most of the salmon sold in Europe is produced on European farms. More salmon sold in the U.S. is produced in Chile or Canada with lower contaminant levels.)

The large difference in farmed and wild salmon contaminant concentrations is likely due to diet. While wild salmon eat a large variety of aquatic organisms where they feed such as krill, zooplankton, and small fish, farmed salmon consume a formulated high-fat feed primarily of other fish ground into fishmeal and fish oil. As a result, farmed salmon consume and concentrate in their fat tissue more of the contaminants typically found in other fish.

Health Risks

The study assessed health risks of exposure to PCBs, dieldrin, and toxaphene using U.S. Environmental Protection Agency (EPA) fish consumption advisory methods. Consumption recommendation calculations for all of the samples tested in the study can be found in the following graph:

Salmon meals per month recommendations using EPA fish advisory methods.

  • While EPA cancer risk parameters for PCBs, dieldrin, and toxaphene generally allow safe consumption of wild salmon at levels between 4 and 8 meals (representing eight-ounce portions) per month, in most cases consumption of more than one farmed salmon meal per month could pose unacceptable cancer risks.

  • Farmed salmon purchased for the study from supermarkets in Frankfurt, Edinburgh, Paris, London, and Oslo triggered consumption recommendations of one-half to one meal per month.

  • There was more variability in contaminant levels found in farmed salmon purchased from supermarkets in the U.S. and Canada. Los Angeles, Washington, D.C., Seattle, Chicago, New York, and Vancouver triggered a recommendation of one to two meals per month. Farmed salmon fillets purchased from supermarkets in Denver and New Orleans triggered consumption advice of three meals per month. But farmed salmon purchased from supermarkets in Boston, San Francisco, and Toronto triggered the more stringent consumption recommendations of the European fish.

Consumption advice for PCBs, dieldrin, and toxaphene is based on cancer risk only. There are many potential non-cancer health risks associated with these contaminants. Some of these risks - including neurological and immune system effects - may occur at lower concentrations than those implicated in cancer.

Recommendations

  • Farmed salmon should be consumed in limited amounts. Consumers should be aware that consumption of even one or two meals of farmed salmon per month may exceed acceptable contaminant levels;

  • Farmed salmon should always be clearly labeled as "farmed;" and

  • The country of origin of all farmed salmon should be clearly identified.

  • Further studies of contaminant sources, particularly on feeds used for farmed carnivorous fish species such as salmon, are needed.

Methodology

This comprehensive study analyzed approximately 700 farmed and wild salmon (totaling about two metric tons) collected from around the world: 459 individual whole farmed salmon obtained from wholesalers in eight major producing regions; 144 fillets of farmed salmon obtained from retailers in 16 large cities in North America and Europe; and 135 whole wild fish representing five wild species of Pacific salmon (chum, coho, chinook, pink, and sockeye). To get more accurate results about average contaminant levels, the laboratory individually tested composites made from three fish or three fillets for a total of 246 tested samples. The study also analyzed 13 samples of salmon feed purchased from European, North American, and South American outlets of two major feed companies, which represent approximately 80% of the global market for fish feed.

Information from the study's authors