Temporal Trend of Organochlorine Contaminant Levels in the Northeastern Part of Lake Superior Basin Based on Lamprey Larvae Lipid Burdens

Abstract Formalin-preserved lamprey larvae collected between 1960 and 1982 were used to test the hypothesis that organochlorine contaminant levels in the northeastern part of Lake Superior basin have decreased since restrictions on their use in Ontario and the United States in the 1970s. Lipid-based burdens of ∑DDT and ∑PCB were significantly higher in the pre-regulation period (1960 to 1974) versus the post-regulation period (1975 to 1982). The DDD/∑DDT ratio was significantly higher in the pre-regulation period. Dichlorobiphenyls had significantly higher levels in the pre-regulation period and both penta- and hexachlorobiphenyls reached significantly higher levels in the post-regulation period. Trends of lipid-based burdens showed a decline in ∑aldrin, ∑HCH, ∑chlordane, ∑DDT, and ∑endosulfan during the 1960s. This trend reversed in the early 1970s, then 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 localized inputs and long range atmospheric transport.