Numerous synthetic organic toxicants have been reported in Lake Superior in the past quarter century although relatively few industrial centers are located on its shores. The chemicals enter the lake primarily through atmospheric deposition via transport from regional and distant sources. This contribution discusses research issues regarding the processes by which the chemicals enter and exit the lake, their in-lake cycling and bioaccumulation, and recently reported potential toxicological effects. Research issues that remain for historically important synthetic organic toxicants are discussed as well as those of emerging chemicals of concern. Although concentrations of some historically important toxicants are decreasing in Lake Superior's waters through volatilization and sedimentation and burial, abiotic and biotic in-lake cycling opens routes of entry into the lake's lower food web, contributing to concentrations in fish that warrant consumption advisories in certain cases. Concentrations of some non-polar emerging chemicals of concern that are increasing in production (such as polybrominated diphenyl ethers) can be expected to increase in the lake and be subject to similar processes occurring to historically important persistent organic pollutants unless regulatory intervention leads to decreasing atmospheric emissions. Other emerging chemicals of concern await measurement in Lake Superior. Our ability to understand the fate and effects of synthetic organic toxicants on the Lake Superior ecosystem, whether they are 'legacy' chemicals or emerging chemicals of concern, is limited by the availability of techniques to determine physical-chemical properties, concentrations, fluxes, bioaccumulation pathways and rates, and mechanisms of toxicity. Future research on synthetic organic toxicants in Lake Superior relies on advances in development of these techniques. Policy decisions must take into account the variety factors that lead to the presence of the chemicals in the lake and their toxic effects.
Copyright 2008 Elsevier B.V., All rights reserved.
- Great Lakes