Farmed salmon and human health: The lowdown on PCBs


Sean Murphy, SeafoodSource online editor

Published on
July 7, 2015

There are plenty of websites and activists out there saying farmed salmon is unhealthy and possibly even dangerous to consume. A quick Google search will yield an alarming number of mainstream media articles from major newspapers and consumer magazines citing various statistics and studies, some of which the industry contends are outdated, based on false or discredited information or simply incendiary.

The predominant health concerns among the salmon farming opponents revolve around polychlorinated biphenyls (PCBs). According to the U.S. National Oceanic and Atmospheric Administration, PCBs are a class of industrial chemicals that once upon a time were used in the manufacturing of a wide variety of consumer products, from microscopes to electrical appliances to TV sets. The chemicals were even commonly sprayed on dirt roads as a dampening agent to control dust.

But by the 1970s, mounting evidence from multiple independent scientific studies began labeling PCBs as carcinogenic. Some studies even suggest – though cannot definitively prove – that PCB exposure could be linked to disorders such as autism. In 1979 the United States government banned the use of PCBs, and other nations have followed suit. Residual chemicals still exist worldwide, however, and trace amounts of PCBs have been detected in the environment.

Farmed salmon opponents are not arguing that salmon farmers deliberately use PCBs in their operations, but that the contaminants are inadvertently getting into the salmon feed. Since salmon are naturally carnivorous, the traditional method of feeding them involves using fishmeal, created by taking smaller feeder fish, such as mackerel, and using them to make pellets and/or fish oil. The problem: the feeder fish live in the open ocean, and are consuming trace elements of PCBs as they eat. That means the pellets, the anti-salmon-farming activists argue, contain a high concentration of the PCBs, which the salmon then absorb into their bodies, making the fillets unsafe for us to eat.

While no one, including the industry itself, denies that use of fishmeal carries a risk of PCB contamination, there are a few problems with the argument that all farmed salmon everywhere carries an unacceptably high level of contaminants. For one thing, virtually all of the anti-farmed-salmon literature cautioning about PCBs, along with various mass-media reports on the same subject, cite as source material three studies, each at least a decade old, back when fishmeal was a much more predominant ingredient in fish feed.

The first is a study published in the scientific journal Chemosphere back in 2002 by geneticist Michael Easton (the study itself does not appear to be available online, but this article describes it). His study showed elevated levels of PCBs in farmed salmon from Canada’s Pacific coast. He cited contaminated feed as the culprit, but there’s no indication of any follow-up studies in the 13 years since.


Also often cited is a study conducted back in 2003 by the Environmental Working Group, a nonprofit organization dedicated to studying the relationship between toxic chemicals and human health. The group purchased salmon at grocery stores in Washington, D.C., San Francisco and Portland, Ore., for examination. According to the study, “seven out of ten farmed salmon purchased were contaminated” with unsafe levels of PCBs. That study also blamed fishmeal pellets for the contamination and suggested further research was necessary, but there’s no indication that the group ever did any.

The other study is from 2004, published in the journal Science and conducted by a team of researchers including Jeffery Foran, Ph.D, a scientist and environmental activist. It is arguably the most extensive study of its kind, and is the one most often cited by activists and the media when criticizing the safety of farmed salmon. In the study, researchers examined 2 metric tons of farmed and wild salmon from around the world, and found concentrations of contaminants, including PCBs, were “significantly higher in farmed salmon than in wild.”

Patricia Lovera, assistant director of Food and Water Watch, a nonprofit that is openly critical of industrial farming of all types, said concerns about PCBs and related contaminants is one of the main reasons she advises American consumers to avoid farmed salmon, especially imported farmed salmon, which makes up the bulk of the farmed salmon available in the United States.

“Aquaculture imports in general worry us,” she said.

Lovera pointed out how the U.S. Food and Drug Administration, tasked with making sure seafood imports to the United States are safe to eat, does not inspect every single piece of fish that comes in, which she called, “a real gap in our food safety system.”


Lovera said until that improves, she tells consumers to choose wild salmon, which is regarded by even the strictest critics as being far safer, mirroring the advice in Foran’s study.

But the Foran study is hardly the smoking-gun evidence of PCB contamination the salmon farming critics say it is. Multiple pro-salmon farming activists point out that the study used a standard set by the U.S. Environmental Protection Agency as the benchmark for declaring how much exposure to PCBs is too much, while similar standards set by multiple health agencies worldwide are not as strict. Even the FDA has less stringent guidelines.

The age of Foran’s study is also a factor. Despite it being more than a decade old, like the other two studies cited here, there is no indication of any follow-up study of the same scope and detail since then.

That matters, because one thing has changed since 2004: what goes into salmon feed. Contrary to what the critics say, the industry has also been concerned about overuse of fishmeal and has been exploring alternatives for years. According to Ian Roberts, a spokesman for Marine Harvest Canada, based in British Columbia, one of the world’s largest farmed salmon producers, and Egil-Ove Sundheim, USA director for the Norwegian Seafood Council, the reasons vary from concerns about PCB contaminants to a concern about depleting the supply of feeder fish worldwide to corporate response to critics.

Whatever the reason, while it would be difficult to eliminate the use of fishmeal or fish oil in salmon feed altogether, the amounts used worldwide in salmon farming have changed dramatically in the past few decades, with various plant-based proteins replacing or supplementing traditional feeds. Roberts said he recalled fishmeal and oil making up 50 percent of the feed used in salmon farming when he joined the company in the mid-1990s. Today, he said, fishmeal and fish oil make up a mere 15 percent of Marine Harvest’s feed.


Andrew Jackson, technical director at IFFO, the Marine Ingredients Organization, said his group has been tracking the use of fishmeal and fish oil worldwide since the 1950s. The organization does not promote or discourage the use of fishmeal or fish oil in salmon feed, or anywhere else, and figures from the IFFO confirm anecdotes from farmers such as Roberts.

According to IFFO data, salmon farmers worldwide in 2000 used a feed that was 52 percent fishmeal and fish oil. In the years since, however, that figure has steadily dropped. By 2013 IFFO data shows fishmeal and fish oil use has been halved to a total of 26 percent of feed ingredients.

Jackson said IFFO doesn’t have more recent data, but there was no doubt in his mind that the trend is continuing.

“It’s certainly gone down from that now,” he said.

Even Lovera acknowledged logic certainly suggests that if the amount of fishmeal and fish oil in salmon feed has dropped by 50 percent in 13 years alone, surely the level of PCB contaminants in farmed salmon fillets has similarly dropped. Still, she said she won’t change her advice to consumers until a new study is done to definitively prove that PCB contamination has abated.

“We don’t understand everything about this model, and not looking doesn’t make it safe,” she said.

As to who should answer those questions, Lovera said she didn’t know. Past studies such as Foran’s were done at extreme expense on a volunteer basis. It’s tough to muster the funds to reexamine the issue, especially for volunteers, she said.

Ideally, government research would be best, she added, but again, there is no mandate, so whether using decade-old research makes sense or not, that’s what activists will have to keep doing.

“It’s also the best we have, and it’s nobody’s job to go look,” she said.



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