Determination of some specific isomers of polychlorinated biphenyl congeners in fatty foods of the Canadian diet

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Abstract
A total of 93 fatty food composites from the cities of Ottawa and Halifax (Canada) were analyzed for 34 selected isomers of polychlorinated biphenyls (PCBs). All fatty foods contained some PCB isomers with the 2,3,4,2’,4’,5'‐ and 2,4,5,2’,4’,5'‐hexachlorobiphenyls present in all samples, except in skim milk and some dehydrated soups. The overall lowest PCB residues of all food commodities were found in skim milk, lamb, margarine and soups. Among the dairy products the highest PCB isomer levels were found in cheese and butter. The sum of all PCB isomers in these two commodities gave residue levels on a wet basis of 2.0 and 3.4 ng/g respectively. In the meat, fish and poultry class the highest specific PCB isomer levels were found in fish, especially freshwater fish, which contained a total of 21.0 ng PCB/g fish. In addition 28 out of the 34 selected PCB isomers were present in freshwater fish. Residue levels in canned fish were the second highest of all food commodities. The observed total PCB residue levels were below the Canadian guidelines for fish, dairy products, poultry, eggs and beef. A comparison of the percentage distribution of PCB isomers in fatty foods and human milk was difficult to evaluate due to the large variation of the fatty food data. However out of 31 PCB isomers reported in fatty foods, 25 were also found in human milk, although not to the same extent.