Understanding the Debate over POPs in Norwegian Farmed Salmon

Salmon farm pens nearby Vestre Jakobselv, Finnmark. (Photo: Christi Turner)

The complex debate over toxins in Norwegian farmed salmon has experts speaking out on both sides, with some maintaining that farmed salmon is safe while others advise against consuming it at all.


The crux of the concern is a group of toxins known as persistent organic pollutants, commonly referred to as POPs.  POPs are a group of chemicals which resist degradation in nature, and instead accumulate in the environment for the long term.  POPs include herbicides, pesticides, coolants, and flame retardants, and many are known to pose significant health risks to humans.  The International Agency for Research on Cancer has classified polychlorinated biphenyls – or PCBs, a type of POPs once widely used as coolants, lubricants and “plasticizers” – as probably carcinogenic to humans.  Many other POPs are also suspected as cancer-causing, on top of other documented adverse health effects on both humans and animals, especially those higher up on the food chain.

This is where farmed salmon come into play.  Marc Berntssen, a scientist at the National Institute of Nutrition and Seafood Research (NIFES), said that it’s important to understand that POPs are highly present in marine ecosystems, mostly as a result of industrial and agricultural run-off.  Just as important, POPs are fat-soluble and accumulate in the “fat” part of the ocean – such as in the bodies of oily, high-fat fish. 

A major ingredient in feed pellets for farmed salmon is typically fish oil, produced from fatty wild fish like blue whiting and capelin that are processed into oil for feed.  This issue in itself has sparked public outcry against the unsustainable harvesting of fish for feed pellets, and prompted the fish farming industry to find ways to use less fish to produce the same amount of farmed fish, and improve the so-called Fish In Fish Out ratio.  

Sustainability concerns aside, the fish oil production process further concentrates the POPs that the blue whiting, capelin, or other fish used for feed have accumulated in nature.  When the feed pellets are given to farmed fish such as salmon, the POPs are passed onto them.

Berntssen said that reducing POPs in farmed salmon is above all a matter of reducing the amount of fish oil in feed pellets.  He said that consumer demand has prompted a shift to vegetable oil in recent years.

“Consumers wanted a more sustainable product, and to reduce the destruction of fish to feed other fish,” Berntssen said.  “The reduction in POPs was a welcome byproduct.”

But as consumers become more aware of the POPs issue, public concern is mounting.  The Barents Observer recently reported on local fishermen’s concern that salmon farms are poisoning surrounding wild fish, which may be accumulating POPs by eating the pellets that fall through the salmon pens to the sea floor.  Recent research suggests that this may be a valid concern.

Despite disagreement from health officials and conflicting scientific evidence, the Norwegian Health Directorate maintains that it is safe to eat farmed salmon.  In 2009, the total value of Norway’s farmed salmon exports was NOK 23.7 billion (EUR 3.1 billion).