Raccoon (Procyon lotor) as a bioindicator of mercury contamination at the US Department of Energy's Savannah River Site

Raccoons (n = 95) were collected from the U.S. Department of Energy's Savannah River Site (SRS) and from public hunting areas. Raccoons were collected near a stream drainage system (Steel Creek delta) and a former reactor-cooling reservoir (pond 13) that received inputs of mercury-contaminated Savannah River water. Mercury concentrations were determined for hair, liver, kidney, muscle, and spleen tissues. Samples were analyzed using inductively coupled plasma mass spectroscopy (ICP-MS) and cold vapor atomic absorption spectroscopy (CVAAS). Raccoons were also collected from a natural stream floodplain system (Upper Three Runs/Tinker Creek) located upstream of Hg use and storage areas and near coal ash basins. These samples were compared to samples collected from off-site hunting areas near the SRS. Hg concentrations between internal tissues were significantly correlated. Hair did not correlate well with internal tissue and was a weak indicator of raccoon exposure to Hg. Nonetheless, raccoons are potentially good indicators of Hg contamination because tissue concentrations were higher in raccoons from areas with known Hg input than in those from reference areas, and muscle biopsies can be used as biomarkers for contaminant exposure. Muscle Hg concentrations ranged from 0-0.14 ppm from nearby hunting grounds, indicating that people hunting in designated areas near the SRS are at negligible risk for Hg consumption from raccoon meat. Several raccoons collected from the SRS had muscle Hg concentrations at or near the FDA action level for seizing commercial fish due to mercury contamination of 1.0 ppm. Though Hg action levels for wild game have not been proposed, it is clear that some SRS raccoons had Hg levels that warrant concern if these areas would be open to public hunting. Last, 64 raccoons from this study had Hg concentrations that were considered elevated by the U.S. FWS standard (> 1.1 ppm) of ecosystem health for one or two tissues (hair, liver, or kidney), and 17 had high concentrations for most or all tissues.