An open letter to the editor re. Easton et al. 2002. Chemosphere 46:1053-1074, involving the safety of farmed salmon.
> Dear Editor:
>
> I would like to express my concerns about a manuscript that appeared recently in an issue of Chemosphere (Easton, M.D.L., D. Luszniak and E.Von der Geest. 2002. Preliminary examination of contaminant loadings in farmed salmon, wild salmon and commercial salmon feed. 46:1053-1074) because I feel that the data were presented in an unconventional manner that would tend to misinform the reader into believing that farm-raised salmon is a heavily contaminated fish that should be avoided by at-risk populations. A closer look at the PCB data reveals that farm-raised and wild salmon are both extremely low in contaminants and are a recommended source of omega-3 fatty acids for pregnant and lactating women, infants and children. Readers of this manuscript that are unfamiliar with comparable levels of PCBs in fish could read this manuscript and inadvertently increase their risk from contaminants by avoiding salmon and eating other species that may contain much higher levels of contaminants. Let me detail some of my concerns that are raised by this manuscript.
>
> First, the sample size of only 8 fish (4 farmed and 4 wild salmon) and 5 feeds was extremely small. Since the authors indicate that the number of samples was not even adequate for a statistical analysis, it can be surmised that the small sample size does not allow the data to even represent the number of farmed or wild salmon that are harvested each year. A main problem with the small sample size is the manner in which the samples were collected from a grocery store with no documentation of their point of origin or prior handling.
>
> Second, the abstract states that PCBs were measured in farmed-salmon at concentrations around 50,000 ppt. I was first confused as to why the data was presented in this fashion (i.e., ppt instead of ppm or ppb) since for studies of this nature, it is typical to use a lower limit of detection of 0.050 ppm (or 50,000 ppt). Most regulatory bodies do not even consider concentrations of PCB less than 0.05 ppm because they are inconsequential from a health perspective. From this manuscript, the reader may surmise that farmed-salmon are heavily contaminated. The authors should have provided the reader with a point of reference by which to evaluate these residue levels. For instance, they could have mentioned that the U.S. FDA action limit for fish entering interstate commerce is 2 ppm (2,000,000 ppt). Actually, our State regulatory body has measured levels of PCBs in wild fish as high as 400,000,000 ppt. In the U.S., 35 States have issued fish consumption advisories due to high levels of PCBs in wild fish. As noted above, an unintended effect of this manuscript could be to drive consumers from eating salmon, a generally low contaminant species, in favor of eating a more heavily contaminated fish.
>
> Third, the manuscript suggests that farm-raised fish are inferior to the wild fish due to the level of contaminants in the feed. Actually, our laboratory has demonstrated that farm-raised fish generally are much lower in contaminants because they are fed a commercial feed rather than having to obtain their food in other manners. Please refer to:
>
> Santerre, C.R., P.B. Bush, D. Xu, G.W. Lewis, J.T. Davis, R.M. Grodner, R. Ingram, C.I. Wei and J. Hinshaw. 2001. Metal residues in farm-raised channel catfish, rainbow trout and red swamp crayfish from the southern U.S. J. Food Sci. 66(2): 270-273.
>
> Santerre, C.R., R. Ingram, G.W. Lewis, J.T. Davis, L.G. Lane, R.M. Grodner, C.I. Wei ,P.B. Bush, D. Xu, J. Shelton, E.G. Alley and J.M. Hinshaw. 2000. Organochlorines, organophosphates and pyrethroids in channel catfish, rainbow trout and red swamp crayfish from aquaculture facilities. J. Food Sci.> 65(2):231-235.
>
> Fourth, the manuscript barely mentions the fact that the wild salmon contained higher levels of mercury than the farmed fish. Why didn> '> t the manuscript also make the point that wild salmon was twice as contaminated by mercury as was farmed salmon, whereas, it may a point of indicating that PCB levels were much higher in farm-raised salmon that in wild salmon? Also, why was the mercury content reported in ppb rather than ppt as used for PCB concentration? From my perspective, the low levels of both mercury and PCBs in these 8 fish are inconsequential from a health perspective.
>
> Fifth, the Tolerable Daily Intake (TDI) for selected PCB congeners was not presented in the conventional manner. The manuscript correctly cites the WHO recommendation that TDI be below 1-4 pg/kg body weight-day. In Table 2 of the manuscript, the TEQ is provided based upon lipid concentration instead of based upon fresh weight of the fish tissue, thereby inflating the value. We have calculated the actual TEQ and TDI based upon U.S. EPA adopted fish consumption data for 75 and 60 kg persons. For a 75 kg man consuming 16.7 g fish per day (actually the EPA normally uses 10 g fish per day), the TDI is 0.252 pg/kg body weight-day which is well below the WHO recommended intake maximum and well below the values indicated by the authors of 6.80 pg/kg body weight-day (lipid). We have provided a Table containing other TDIs based upon various fish consumption estimates (see attachment).
>
> Finally, since I noted that this research was supported by the David Suzuki Foundation, I went to their website to see what spin was placed on this research. On their site you can find the headline, > "> International science journal publishes landmark study on wild and farmed salmon.> "> Some of the comments that can be seen here include, > "> Dr. Easton> '> s study shows that the contaminants, known as persistent organic pollutants, are especially dangerous for children, nursing mothers and pregnant women or women considering pregnancy. The samples studied showed that farmed salmon contained much higher levels of pollutants, including 10 times more Polychlorinated Biphenyls (PCBs) than wild fish.> "> From a scientific perspective, how is it that contaminants detected at such low levels have toxicological significance. It appears that the presentation of these data was made with an agenda in mind.
>
> My concern is that this manuscript is written in such an unconventional manner so as to scare consumers away from eating salmon whether it be farm-raised or wild, thus discouraging them from consuming a low contaminant fish, like salmon, which can be an important source of healthy omega-3 fatty acids in the diet. I request that Chemosphere further review this manuscript and attempt to clarify this situation with readers and reviewers.
>
> Sincerely,
> Charles R. Santerre, Ph.D.
> Associate Professor
> Department of Foods and Nutrition Purdue University
> 1264 Stone Hall West Lafayette, IN 47907-1264
> telephone 765/496-3443
> e-mail santerre@purdue.edu
>
P.S. In the interest of disclosure, I have never worked with or consulted for the salmon industry or any other seafood company and I have no known personal financial interests associated with this industry. My role at Purdue University as a faculty member and cooperative extension specialist is to provide science-based information to consumers so they can make informed decisions on chemical food safety issues.
> > <<EastonListserv.doc>>
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