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Letter to Science Mag. Editor on PCB's in Salmon
02/26/04
By Dr. Brad Hicks, BSc, MSc, DVM
The paper by Hites et al , “Global Assessment of Organic Contaminants in Farmed Salmon, Science volume 303 pages 226 – 229� is more of an exercise in yellow journalism than an exercise in scientific reporting. From the skewed publicity this article has received it appears that the article may have partially met its objective of demonizing farmed salmon rather than contributing to the body of knowledge of science.
First the authors make inappropriate comparisons. They compare different species from different areas and may have also compared fish of differing ages. All of these differences could explain the results presented rather than whether the fish were farmed or wild. Yet the paper is published as a comparison of farmed and wild salmon.
All of the low levels of PCBs in wild salmon are in chums and pinks both species have very low lipid levels and therefore would have very low levels of PCBs. In addition if these fish were from maturing the lipid that would have been in the muscle would have begun to translocate to reproductive products further lowering the PCB levels in the muscle. This leaves the misleading impressing that wild salmon have lower levels of PCBs than farmed salmon when the reality is that farmed salmon and wild salmon of similar species from similar regions have very similar miniscule levels of such contaminants.
The authors also appear to ignore the previously published literature which reports much higher levels of PCBs in wild salmon. Not necessarily, chums and pinks but Coho and Chinook where the levels of lipids are more comparable to farmed salmon and the levels of PCBs reported in these wild salmon species is actually higher than the levels reported in farmed salmon. The PCB levels in wild salmon have been reported at levels many times higher than those found in farmed salmon. Why is this information not presented in this paper?
For the material examined from the supermarkets, there is no indication of species or whether the salmon are from wild or farmed sources. The inference is that they are from farmed sources but without knowledge of species or source it is not possible to tell. And since there are a number of reports in the literature that wild Coho and Chinook have levels of PCBs in the ranges of those found in the supermarket fish is possible that some of the supermarket fish were wild salmon?
Comparing different geographic regions with wild salmon from one region and farmed salmon from another region is also problematic. The highest levels of PCBs are in farmed fish are from regions of northern Europe. The lowest are from South America and the levels in North America are in the middle. Yet there is no comparison for wild salmon of the same species in the same geographic region. It is likely that the reported finding are more a reflection of the geographic region where the salmon are being raised or harvested from the wild rather than whether the fish are of farmed or wild origin.
The other major flaw in this paper is the authors fail to discuss the relative benefits and risk associated with their findings. The benefits of eating fish with these low levels of PCBs are much greater than the risks. Indeed, the levels in wild Coho and Chinook from the Pacific Northwest are higher than farmed salmon from the same region yet the authors fail consider this information. If farmed fish are dangerous to eat at the levels reported then it must be even more dangerous to eat wild salmon. The fact is that both are good for you and neither is dangerous to eat.
The authors appear to have an agenda beyond the reporting of scientific information and their agenda in part appears to be demonizing farmed salmon. This is not science. This is politics. This type of report belongs in a political publication where yellow journalism is considered and art. It does not belong in a scientific publication where yellow journalism is usually considered a scourge. Perhaps the next time these authors try to use your publication for their political agenda you will more careful.
Sincerely yours,
Brad Hicks, BSc, MSc, DVM
Langley, BC
Canada
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