Perfluorinated chemicals (PFCs) are of concern due to their widespread use, persistence in the environment, tendency to accumulate in animal tissues, and growing evidence of toxicity. Between 2006 and 2011 we collected blood plasma from 261 bald eagle nestlings in six study areas from the upper Midwestern United States. Samples were assessed for levels of 16 different PFCs. We used regression analysis in a Bayesian framework to evaluate spatial and temporal trends for these analytes. We found levels as high as 7370 ng/mL for the sum of all 16 PFCs (∑PFCs). Perfluorooctanesulfonate (PFOS) and perfluorodecanesulfonate (PFDS) were the most abundant analytes, making up 67% and 23% of the PFC burden, respectively. Levels of ∑PFC, PFOS, and PFDS were highest in more urban and industrial areas, moderate on Lake Superior, and low on the remote upper St. Croix River watershed. We found evidence of declines in ∑PFCs and seven analytes, including PFOS, PFDS, and perfluorooctanoic acid (PFOA); no trend in two analytes; and increases in two analytes. We argue that PFDS, a long-chained PFC with potential for high bioaccumulation and toxicity, should be considered for future animal and human studies.

In this study, we assessed mercury (Hg) exposure in several tissues (brain, liver, and breast and primary feathers) in bald eagles (Haliaeetus leucocephalus) collected from across five Great Lakes states (Iowa, Michigan, Minnesota, Ohio, and Wisconsin) between 2002-2010, and assessed relationships between brain Hg and neurochemical receptors (NMDA and GABA(A)) and enzymes (glutamine synthetase (GS) and glutamic acid decarboxylase (GAD)). Brain total Hg (THg) levels (dry weight basis) averaged 2.80 μg/g (range: 0.2-34.01), and levels were highest in Michigan birds. THg levels in liver (r(p) = 0.805) and breast feathers (r(p) = 0.611) significantly correlated with those in brain. Brain Hg was not associated with binding to the GABA(A) receptor. Brain THg and inorganic Hg (IHg) were significantly positively correlated with GS activity (THg r(p) = 0.190; IHg r(p) = 0.188) and negatively correlated with NMDA receptor levels (THg r(p) = -0245; IHg r(p) = -0.282), and IHg was negatively correlated with GAD activity (r(s) = -0.196). We also report upon Hg demethylation and relationships between Hg and Se in brain and liver. These results suggest that bald eagles in the Great Lakes region are exposed to Hg at levels capable of causing subclinical neurological damage, and that when tissue burdens are related to proposed avian thresholds approximately 14-27% of eagles studied here may be at risk.

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