Effect of cooking on the loss of persistent organic pollutants from salmon

Recent studies have raised concern over the presence of high levels of persistent organic pollutants (POPs) in farmed fish relative to wild specimens of the same species, particularly salmon. Although cooking is known to reduce the burden of POPs in fish, the mechanisms of loss/degradation are not clearly understood. This study investigated the loss of POPs, including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), p,p'-DDT [2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane] and its related metabolites (sum noted as DDTs), and chlordane congeners, from salmon (Salmo salar) steaks when subjected to baking, boiling, frying, or microwave cooking. Ranges in the raw flesh were 25.1-62.9 ng/g wet weight (ww) for PCBs, 2.5-7.6 ng/g ww for PBDEs, 2.4-5.3 ng/g ww for chlordanes, and 17.5-43.8 ng/g ww for DDTs. Analysis of raw steaks from along the fish body revealed a significant variation of POP concentrations along the fish body, with higher concentrations at the head end than the tail, with a peak in the central section. After cooking, levels of POPs decreased in salmon steak with an average loss of 26 +/- 15% relative to the initial POP load in the raw steak. The removal of the skin from the cooked salmon steak resulted in a further average loss of 9 +/- 3%. The loss of POPs did not differ significantly between cooking methods. Losses of POPs were significantly and linearly correlated with the losses of lipid during cooking, suggesting removal of lipids is the critical factor for POPs reduction in cooked fish. Cooking of raw fish contaminated with POPs can therefore be expected to reduce the consumption exposure risk to human health.