DNA Double-Strand Breakage as an Endpoint to Examine Metal and Radionuclide Exposure Effects to Water Snakes on a Nuclear Industrial Site

ABSTRACT

This study examined metal levels (especially U and Ni) in the tail tissues of water snakes from contaminated (Tim's Branch) and reference areas on the Department of Energy's Savannah River Site (SRS). Home ranges of snakes were quantified to determine the ratio of the habitat that they use in relation to the contaminated areas to better estimate exposure Compared to conventional methods that do not. The exposure assessment indicated that water snakes in the contaminated areas could expect U exposure at 3–4 orders of magnitude greater than the Agency for Toxic Substances and Disease Registry's Minimum Risk Level (MRL) from ingestion of amphibians and fish. Ni and U, in addition to Se, Mn, and Cu, were related to increased DNA double-strand breakage (DDSB) in water snakes. We report burdens for each metal individually, but the results of the DDSB indicated that these metals did not behave independently, but as a suite. If we did not have a secondary endpoint (DDSB), we might have assumed from the exposure predictions and tissue burden analyses that U was the sole metal of concern to water snakes in Tim's Branch. These data also imply that these toxicants do not biomagnify at the spatial and temporal scale of this study.

Key Words:

• DNA double-strand breaks
• exposure
• uranium
• Nerodia
• nickel
• water snakes

ACKNOWLEDGMENTS

This project was funded through the Financial Assistance Award DE-FC09– 96SR18546 from the U.S. Department of Energy to the University of Georgia Research Foundation. This research was also funded by the Consortium for Risk Evaluation with Stakeholder Participation (CRESP) through the U.S. Department of Energy (AI#DE-FC01-95EW55084 and DE-FG26-00NT-40938) and NIEHS (ESO 5022). We thank Cub Stephens for overseeing and conducting extensive field work. S. J. Mullin and the Eastern Illinois University Herpetology Laboratory edited an earlier manuscript version, thus providing additional insights that improved this article. This article also benefited from the comments of four anonymous reviewers.