TCS Daily

Are You Eating Cancerous Salmon?

By Ronald Bailey - January 14, 2004 12:00 AM

Smoked salmon with capers and onions was featured at brunch at a friend's house this past Sunday. I dug in and enjoyed two helpings, despite last week's dire headlines that I was recklessly gambling with cancer.

Those alarming headlines were based on the study "Global Assessment of Organic Contaminants in Farmed Salmon" published in Science. That study tested 700 samples of salmon from Europe and South and North America for the presence of various man-made contaminants. The researchers supported by the Pew Charitable Trusts especially focused on poly-chlorinated biphenyls (PCB) levels in wild versus farmed salmon.

PCBs and Greens

PCBs were manufactured from the 1930s until they were banned in the late 1970s. They were used as stable insulating coolants in electrical equipment, especially electrical transformers. Based on high-dose animal studies and some small human epidemiological studies, PCBs have been classified by the U.S. Environmental Protection Agency (EPA) as probable human carcinogens. As persistent chemicals, PCBs can bio-accumulate. In other words, small aquatic creatures with low levels of PCBs in their bodies get eaten by larger creatures that in turn get eaten by still larger animals, a process that concentrates the contaminants in the fatty tissues of the bigger predators.

What inspired the Science researchers to focus on farmed salmon versus wild salmon? It turns out that the PCB studies are just the latest of a series of recent attacks by green groups against farmed salmon.

But why go after farmed fish? After all, initially one might think that environmentalists would applaud fish farming since it could help take the pressure off already depleted stocks of wild fish. And make no mistake aquaculture is rapidly expanding. "Aquaculture is growing more rapidly than all other animal food producing sectors," according to the Food and Agriculture Organization's (FAO) report, The State of the World's Fisheries and Aquaculture 2002. According to the FAO, the world's capture fisheries produced 91.3 metric million tons of food, while 37.5 million metric tons were produced by aquaculture. Aquacultural production increased from 3.9 percent of total production by weight in 1970 to 27.3 percent in 2000. The consumption of farmed salmon has soared from 24,000 tons to over 1 million tons in the past two decades.

Earlier green attacks on focused on the alleged damage to the environment caused by salmon farming and on worries about fish miscegenation should escaped farm-raised fish interbreed with wild salmon. Now some are petrified by the prospect of genetically enhanced salmon.

'Their Next Strategy'

But these fears have fallen on largely deaf ears. So what to do? "Green groups were getting frustrated because they have not been able to make the case to the public that fish farming is very harmful to the environment," speculates Purdue University toxicologist Charles Santerre. "So their next strategy is to go after farmed salmon on the basis of food safety and nutrition."

And it's a tried and true strategy. By alarming consumers, some green groups hope to destroy, or at least limit, salmon farming. The first "study" seeking contaminants in farmed salmon was done in 2001 by Michael Easton, president of the for-profit International EcoGen company and was commissioned by the environmentalist David Suzuki Foundation in British Columbia. Easton tested 8 salmon, 4 farmed and 4 wild and found that the farmed salmon contained 51,216 parts of trillion of PCBs versus 5,302 parts per trillion PCBs in the wild salmon -- nearly ten times more.

But hold on -- what does that mean? The U.S. Food and Drug Administration (FDA) limits the amount of PCBs in all fish to 2 parts per million. It turns out that Easton's farmed salmon contained only 0.05 parts per million. To get a sense of the magnitudes being considered here, one part per million compares to 1 inch in 16 miles, and one part per trillion compares 1 inch in 16 million miles (600 times around the earth). Earlier in 2003, the Washington-based environmental advocacy organization, the Environmental Working Group, publicized a similar study, testing 10 fish in which similar levels of PCBs were found in farmed salmon.

Some of the researchers selected to run the Pew-backed study have strong activist credentials. For example, Jeffrey Foran is president of Citizens for a Better Environment in Milwaukee, which, among other things, warns pregnant women against the dangers of eating contaminated fish. Another researcher on the Pew project was David O. Carpenter, Director of the Institute for Health and Environment at SUNY-Albany. In the 1990s, Dr. Carpenter was concerned about the alleged cancer causing effects of electromagnetic fields produced by power lines. He also became involved in the campaign to force General Electric to dredge up PCBs that company dumped in the Hudson and serves as an advisor on the River Network's Health and Environmental Justice Committee.

Not Junk, Just Irrelevant

Just because some of the researchers are activists doesn't mean that their science is wrong. In this case, their findings are just irrelevant. The $2.4 million Science study didn't really find anything new. It basically confirmed the smaller studies which found the highest PCB concentrations in farmed salmon at about 0.05 parts per million. In other words, the PCB concentrations in farmed salmon identified by the Pew funded researchers is about 40 times less than those believed safe by the FDA.

Curiously, the U.S. Environmental Protection Agency recommends that consumers limit their consumption of fish containing more than 0.05 ppm to once a month -- the standard adopted by the Pew funded researchers. Why the difference in standards?

Purdue toxicologist Santerre makes an analogy to the risks of wearing seat belts. As of January 1, Santerre became a technical advisor to the trade group Salmon of America. According to Santerre, the EPA is setting a level at which 1 in 100,000 people who eat 8 ounces of salmon everyday for 70 years would get cancer. On the other hand, the FDA weighs both the risks and benefits of an activity -- in this case eating salmon that provides strongly health promoting omega-3 fatty acids versus some small exposure to things like PCBs. Indeed farming salmon has dramatically lowered the price of the tasty fish, increasing the access of lower income people to the health benefits offered by omega-3 fatty acids.

So the FDA threshold is set by a process that is like balancing the large number of people whose lives are saved by seatbelts versus those who lose their lives because of seatbelts. The EPA's threshold is a legitimate number but not really relevant for people making decisions about how best to minimize their risks in the case of salmon. "The Science study is a good study," says Santerre. "But it's like studying how many people get killed because they wore their seatbelts. Interesting, but irrelevant in terms of overall public health and safety."

A Scare Behind the Curve

Wild salmon dine on krill and shrimp which are a bit lower on the food chain and which are therefore not a source of concentrated contaminants like PCBs. The farmed salmon get their doses of PCBs from the fish meal fed them in their pens. The fish meal is generally made by grinding up species like mackerel, sardines and anchovies. These species are higher on the food chain and so one would expect them to have higher levels of contaminants.

But the green PCB scare is behind the curve. As University of Texas toxicologist Stephen Safe points out, levels of PCBs in fish have been falling for decades. Human exposure to PCB's is only 10 percent of what it was three decades ago and continues to fall. Environmental groups are concerned that it takes three pounds of bait-fish to produce one pound of salmon.

However, salmon farmers are moving away from fish meal and toward feeding their fish things like soybean meal produced on land. Even better, canola is being genetically modified to produce the precursors to omega-3 fatty acids so that when it's fed to farmed salmon in the future, they will produce even more of the beneficial substances. Rather than oppose genetic improvements, greens who are worried by environmental damage caused by farming salmon should celebrating the advent of genetically enhanced fish -- they grow twice as fast as regular salmon and eat 20 percent less food. This means that aquaculturalists could raise twice as many fish in the same amount of area, while producing less pollution.

Here's hoping that the new PCB scare doesn't get as far as the earlier bogus Alar scare did. In the meantime, enjoy that salmon at your Sunday brunch.

Ronald Bailey is Reason magazine's science correspondent. His email is


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