Temporal trend of organochlorine contaminant levels in the northeastern part of Lake Superior basin based on lamprey larvae lipid burdens

Formalin-preserved ed lamprey larvae collected between 1960 and 1982 were u sed to test the hypothesis that organochlorine contaminant levels in the no rtheastern part of Lake Superior basin have decreased since restrictions on their use in Ontario and the United States in the 1970s. Lipid-based burde ns of Sigma DDT and Sigma PCB were significantly higher ill the pre-regulat ion period (1960 to 1974) versus the post-regulation period (1975 to 1982). The DDD/Sigma DDT ratio was significantly higher ill the pre-regulation pe riod. Dichlorobiphenyls had significantly higher levels in the pre-regulati on period and both penta- and hexachlorobiphenyls reached significantly hig her levels in the post-regulation period. Trends of lipid-based burdens sho wed a decline in Sigma aldrin. Sigma HCH, Sigma chlordane, Sigma DDT, and S igma endosulfan during the 1960s. This trend reversed in the early 1970s, t hen reversed again to a decline in the 1980s. In the Case of PCBs, after an initial rise in the mid 1960s, levels declined to low values in the 1980s. Trends observed in lamprey ammocoetes were consistent with known pesticide and PCB use. Overall, their sources appear to be a combination of localize d inputs and long range atmospheric transport.