Mercury levels lower in farmed salmon than in wild salmon

Journal of Environmental Health, Sept, 2008

Much of the farmed salmon imported to the United States comes from British Columbia, Canada. Long-lived species higher up in the food chain, such as tuna, often have high levels of methylmercury, which can increase cancer risk. A new study published in Environmental Toxicology and Chemistry has found that levels of mercury and trace metals in both wild and farmed salmon from British Columbia are significantly below health guidelines.

Mercury levels tested in both farmed and wild salmon were well below consumption guidelines set by Health Canada. Maximum concentrations of other metals were also well below guidelines. Farmed salmon did not have significantly higher concentrations of arsenic, cobalt, copper, or cadmium than wild salmon. In fact, mercury concentrations in the flesh of wild salmon were three times higher, probably because farmed fish have such rapid growth cycles, resulting in growth dilution. No differences were found between pre- and post-processing levels for farmed fish.

Mercury and other metal concentrations in commercial feed were found to be significantly higher than in salmon flesh. This holds true for all 18 trace elements tested except for mercury, which showed similar levels in feed and fish flesh due to higher dietary uptake and slow elimination from salmon.

Compared to other foodstuffs, total mercury was found to be slightly higher in wild or farmed salmon than in chicken, beef, or pork, but was comparable to fruit, vegetables, honey, and eggs. Levels of other trace elements were lower in salmon than in other foodstuffs, and average dietary intake of mercury and trace metals from salmon remains low (0.05%--32%) compared to meat, poultry, fruit, and vegetables (68%-99%). Salmon also showed a moderate surplus of selenium, which is beneficial because of its ability to detoxify and counteract mercury toxicity.

The evidence supports weekly consumption of salmon as a healthy source of omega-3 fatty acids for heart and other health benefits as recommended by the American Heart Association. To read the entire study, visit www.allenpress.com/pdf/il552-8618-27-6-1361.pdf. Environmental Toxicology and Chemistry is the monthly journal of the Society of Environmental Toxicology and Chemistry (SETAC). For more information about the society, visit www.setac.org.