January 15, 2004
by Alex A. Avery
Last year an environmental activist group warned us, based on a survey of fourteen fish, that salmon from fish farms represent a grave cancer threat due to man-made pollutants such as PCBs and dioxin. The group recommended eating only wild salmon or avoiding salmon consumption altogether.
Now these same alarmist warnings have been echoed in the pages of Science, the world’s most respected scientific journal. The journal has just published a survey of the contaminants in nearly 700 salmon from Europe, North and South America, funded by the Pew Trust Environment program.
There is no doubt that this research accurately reflects the current levels of man-made chemicals in both wild and farm-raised salmon from various parts of the world. On that there is no dispute.
But whether or not these chemical traces pose any appreciable cancer or other health risk is open to debate. In fact, some say this latest research merely proves that all salmon is safe. Purdue University toxicologist Dr. Charles Santerre says, “In my view, the study says we should be eating more farmed salmon.”
The worry is over organochlorines—chlorinated chemicals that take a long time to biodegrade. They include dioxins, PCBs, and early synthetic pesticides like DDT and toxaphene. Most countries banned these chemicals decades ago because of theoretical health and environmental risks. But traces of these chemicals continue to persist in the environment even thirty years later.
Farmed salmon raised in large pens in coastal waters are currently fed significant amounts of high-protein fishmeal that contains traces of these chemicals. The fishmeal is made up mostly of fish on the higher end of the food chain, which explains the higher contaminant levels. Wild salmon consume these chemicals in their diet too, although at 10-20 percent of the levels found in farmed salmon.
While the five to ten-fold difference in contaminant levels between farmed and wild salmon appears substantial, it is irrelevant because all the contaminant levels are so low. Both farmed and wild salmon had contaminant levels well below the FDA’s safety limits, as well as below the safety limits set by Europe and the World Health Organization.
The highest PCB levels the researchers found were still 40 times lower than the FDA and WHO safe limit of two parts per million (ppm). The FDA allows up to 3 ppm of PCBs in poultry and even 0.2 ppm in baby foods. Most contaminants were found at only a few parts per billion (ppb). For perspective, one part per billion is one inch in 16,000 miles.
So what’s the fuss about? The researchers based their cancer warnings on a fish consumption guideline established by the U.S. Environmental Protection Agency that is forty times stricter than the FDA and WHO limit.
The EPA guideline is stricter in part because the agency examines only potential risks, not benefits. In contrast, the FDA weighs the theoretical cancer risks from contaminants versus the known health and anti-cancer benefits from regular fish consumption. The FDA takes into account the heart healthy omega-3 fats in fish.
Moreover, the EPA compounds its anti-chemical bias with multiple flawed assumptions. The EPA assumes that there is no safe level of low-dose exposure (called a low-dose threshold), assumes that cancer risks from different chemicals are additive, and assumes seventy years of fish consumption at the current contaminant level.
All three of these assumptions are wrong. First, there is surely a low-dose cancer threshold. We are exposed to low doses of thousands, if not millions, of natural carcinogens in fruits and vegetables every day. Yet like fish, consumption of these foods reduces rather than raises cancer risks.
Second, cancer risks from different chemicals aren’t likely additive, and certainly not at such low exposures. This additive component is what allowed the Pew researchers to claim that it would be safe to eat farm-raised salmon only once every one to two months. Interestingly, the EPA guideline is so strict it would limit consumption of even wild salmon to no more than two to four meals per month.
Finally, and most importantly, we know that human exposures to these chemicals will decline in the future as the amounts of these chemicals in the environment continue to fall. Levels have already declined 90 percent since the mid-1970s. Thus, the EPA’s assumption of seventy years of exposure has no logical basis.
Sir John Krebs, head of the UK’s Food Standards Agency, said of the warnings, “Our advice is that people should consume at least two portions of fish a week, one of which should be oily like salmon.” Terry Troxell with the FDA said, “we’ve looked at the levels found . . . and they do not represent a health concern. In the end our advice is not to alter consumption of farmed or wild salmon.”
For all of the negative press and alarm, consumers do not seem to have been much impacted. Salmon sales remain high in Europe and North America, where much of the consumption and negative publicity have occurred. Hopefully this means that consumers are listening to the food safety and health experts rather than the environmental alarmists.
And that brings up an important point. This debate isn’t really about health; it’s about an environmental agenda. The Pew researchers aren’t toxicologists or cancer specialists. All the participants have an environmental agenda, from the author who is head of an environmental activist group, the environmental consultants who managed the research project for Pew, to the Pew Foundation itself.
In contrast, multiple food safety agencies staffed by toxicologists, cancer specialists, and nutritionists are in agreement that this research reveals little food safety risk. Truth be told, if the 30 ppb of PCBs in farm raised salmon were enough to cause legitimate concern, so would the 5 ppb PCB found in wild caught salmon, or the 7 ppb found in beef. There really isn’t much difference, or any real danger.
What’s most surprising is that environmental researchers would attempt to discourage consumers from eating farmed salmon because this source of salmon helps to relieve overfishing of wild fish stocks. You would think that environmentalists would applaud a system by which humanity supplies its own needs without putting undue pressure on nature.
Moreover, in part because of negative perceptions among some consumers, fish farmers are moving away from fish meals made from wild-caught fish and toward feeding more plant-based high protein feeds like soybean meal. Scientists are already busy developing genetically improved canola that will produce the precursors to omega-3 fatty acids, the heart health oil in fish. If they succeed, it’s likely that the farmed fish will not only have lower contaminant levels than the wild fish, but may actually be healthier for you.
Alex Avery is director of research and education for the Hudson Institute's Center for Global Food Issues.
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