Salmon raised on farms have significantly higher levels of PCBs and other potentially harmful substances than wild salmon, researchers report. Levels of contaminants were higher in European-raised salmon than in salmon raised in North and South America, researchers report.
But the findings do not mean that diners should go cold turkey on salmon, the study's authors say, noting the health benefits of salmon, including its content of omega-3 fatty acids, which are thought to be beneficial in fighting heart disease.
The researchers hope this new information will help the US Food and Drug Administration (FDA) and other health agencies develop updated advice on fish consumption to help consumers make decisions about what type and how much fish to eat. But they also caution that the study was designed to measure contaminant levels in salmon, not to develop guidelines for fish consumption.
Until new guidelines are developed, however, the researchers suggest that people who are concerned about contaminated fish may want to steer clear of Atlantic salmon, since virtually all Atlantic salmon comes from farms. Consumers may want to seek out wild Alaskan king salmon or ask before purchasing salmon whether the fish is wild or farm-raised.
The presence of contaminants in salmon is not a new issue. The authors note that contaminant levels in salmon have been an issue in the Great Lakes area for the past 20 years. But salmon has become increasingly popular in recent years, as the beneficial health effects of the fish have become more widely known. The increased demand for salmon, however, has lead to more and more salmon being grown on farms rather than caught in the wild. He noted that there is very little information on the levels of PCBs and other contaminants in farm-raised salmon, whose feed is made from other fish and fish oil. It appears that much of the contamination of farm-raised salmon comes from the feed the fish are given. Therefore, there may be an opportunity to change the formulation of the feed and reduce contaminants.
The researchers measured levels of PCBs, dioxins and other contaminants in about 700 salmon from around the world. Levels of 13 out of 14 contaminants were higher in farmed salmon than in wild salmon. Concentrations of all contaminants were significantly higher in European farmed salmon than in fish raised in North and South America.
The researchers conducted additional analysis on four contaminants that are proven to be harmful to human health: PCBs, dioxins, toxaphene and dieldrin. Concentrations of these substances were consistently higher in farmed salmon than in wild fish. Levels were greatest in farmed salmon from Scotland and the Faroe Islands and lowest in farmed fish from Chile and Washington state. But even the least contaminated farm-raised salmon had significant higher levels of PCBs, dioxins and dieldrin than wild salmon.
Although the researchers did not study the health impact of eating farmed salmon, the findings suggest that eating farmed salmon may expose people to contaminants that could have harmful health effects. The authors note that these findings also highlight the importance of labeling salmon.
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