Friends of the Earth is calling for clearer labelling so that consumers can tell whether the fish they are buying is wild or farmed, and where it has come from.
The study, which looked at 700 farmed and wild salmon from eight major salmon-producing regions, concluded that the contamination levels in farmed salmon on sale in Europe were so high that consumers should only eat one portion every two months to avoid an increased risk of cancer. The fish, sampled from wholesale and supermarket outlets, were contaminated with a range of persistent chemicals, including PCBs, dioxins, dieldrin and toxaphene.
Farmed salmon on sale in Europe was found to be generally more contaminated than salmon farmed in North and South America. Atlantic salmon contain significantly higher concentrations of PCBs and many chlorinated pesticides than wild Pacific salmon, according to an analysis of more than two metric tons of farmed and wild salmon from around the world.
Farmed salmon on sale in Scotland was found to have the highest levels of contamination, with the authors suggesting it would be unadvisable for consumers to eat more than one portion of supermarket salmon every two months. The researchers also stressed the need for additional studies on salmon feed that is high in fish meal and fish oil and could be a source of contamination.
The conclusion made by the report is that contaminant levels in some farmed salmon may be high enough to detract from the health benefits of eating fish. The authors note that their study demonstrates the importance of labelling salmon as farmed and identifying the country of origin.
"This study shows yet again how the use of persistent chemicals contaminates our environment and food sources, which can be magnified by intensive farming practices," said Friends of the Earth chemicals campaigner Mary Taylor. "Consumers and retailers alike should be shocked by these findings. As the study says, better labelling and consumer information would allow consumers to minimise the risks, but we also need to ensure that new chemicals legislation properly protects the environment from persistent chemicals in the long run."
The issue of seafood labelling has been a big issue of late in Europe. In Norway, for example, there has been great consumer and industry pressure for salmon raised in certain conditions to be able to bear the label 'This is a free range salmon fillet'. This move comes after growing demand for the ethical production of seafood.
"We are noticing an international trend where consumers demand ethics in the methods of fish farming and slaughtering. Manufacturers who fail to meet these demands are likely to suffer economically," said Børge Damsgård, principal scientist at Norwegian research company Fiskeriforskning.
The Norwegian labelling initiative is very much in line with the EU-funded project SEAFOODplus. The stated strategic objective of this programme is to make seafood safe for the consumer by identifying risk factors, avoiding risks caused by viral and bacterial contamination, biogenic amines in seafood and to undertake risk-benefit analysis.
"This project will broaden our perspective and consider the ethics of the entire chain of production of various types of fish," said Damsgård. "In order to develop a set of ethical methods we have to know more about differences in behaviour and properties of fish such as salmon, halibut, sea bass and cod. Thanks to this project, we are given the opportunity to work with these issues over a long period of time."