Study allays farmed salmon safety concerns

By Rob Fetcher

The study, which was undertaken by a team of researchers from National Institute of Nutrition and Seafood Research (NIFES), looked at the levels of environmental pollutants such as dioxins and PCBs, heavy metals, and organochlorine pesticides – substances that have increasingly been associated with seafood in the public perception over the last couple of decades. The project’s main objective was to evaluate trends of contaminant levels in Norwegian farmed Atlantic salmon in light of the derived tolerable weekly intakes (TWIs). The researchers were able to analyse fish samples compiled by the Norwegian Food Safety Authority (NFSA), which between 1999 and 2011 collected more than 2300 samples of Norwegian farmed Atlantic salmon for contaminant analyses. The fillets of these fish were homogenised and analysed for dioxins, PCBs, heavy metals and organochlorine pesticides. This new research project was able to make some interesting conclusions, and the team from NIFES was able to trace the decline of a number of contaminants coincided with the increased substitution of plant proteins for fishmeal which began during the 1999-2011 period. Indeed they noted that the clear decline in arsenic and mercury levels in the salmon corresponded to “the concurrent decline in the use of fish meal and fish oil in commercial fish feed”. Equally, the research showed that the decrease in the levels of dioxins and dioxin-like PCBs “was mainly related to the substitution of fish oils by vegetable oils in the feed”. The levels of non-dioxin like PCB 6, however, did not decrease nor increase throughout the years. In terms of pesticides, their results show a decline in the levels of DDT and its metabolites in Norwegian farmed salmon from 2002 to 2011, which is consistent with the decline of DDT in fish feed in the same period. The levels of the other pesticides remained unchanged throughout the period. Overall, however, they were able to conclude that the contaminant levels in Norwegian farmed salmon have generally decreased between 1999 and 2011. Moreover – and more importantly for consumers of farmed salmon – the researchers concluded that for all compounds except mercury and the sum of dioxins and dl-PCBs, the measured amounts were negligible compared to the current TWIs. Overall, the limiting factor for consumption of Norwegian farmed Atlantic salmon was the content of dioxins and dl-PCBs but, due to the decrease of the levels in these contaminants over the years, (if you don’t take into account other possible sources of dioxin and dlPCB) the amount of Norwegian farmed salmon that can safely be consumed has increased from 370g per week in 1999 to 1.3 kg salmon per week in 2011. This is in marked contrast to a 2004 food safety assessments of farmed Atlantic salmon in which Hites and co-workers recommended farmed Atlantic salmon meals to be reduced to one per month.

The research in full was published in Volume 74 of Environment International and the full version can be viewed at http://www.sciencedirect.com/science/article/pii/S016041201400302X