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Exposure and effects of perfluoroalkyl substances in tree swallows nesting in Minnesota and Wisconsin, USA
Citation:
Custer, C., T. Custer, P. Dummer, M. Etterson, W. Thogmartin, Q. Wu, K. Kannan, A. Trowbridge, AND P. McKann. Exposure and effects of perfluoroalkyl substances in tree swallows nesting in Minnesota and Wisconsin, USA. ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY. Springer, New York, NY, 66(1):120-138, (2014).
Impact/Purpose:
This manuscript describes exposure of tree swallows to perfluoroalkyl substances (PFASs) at several lakes in Minnesota and Wisconsin and describes the resulting effects on reproductive success for the swallows. The manuscript demonstrates the effectiveness of multistate modeling applications to avian nest success in the presence of chemical contaminants. It also furthers our understanding of the effects of chemicals in the presence of competing risks (nest predation, nest abandonment). The primary audience for this manuscript will be risk managers, toxicologists, and ornithologists.
Description:
The exposure and effects of perfluoroalkyl substances (PFASs) were studied at eight locations in Minnesota and Wisconsin between 2007 and 2011 using tree swallows (Tachycineta bicolor) as sentinel species. These eight sites covered a range of possible exposure pathways and ecological settings. Concentrations in various swallow tissues were quantified as were reproductive success endpoints. The sample egg method was used wherein an egg sample is collected and the hatching success of the remaining eggs in the nest is assessed. The association between PFAS exposure and reproductive success was assessed by site comparisons, logistic regression analysis, and multistate modeling, a technique that has not previously been used in this context. There was a negative association between concentrations of PFASs in eggs and hatching success; this is the second field study in which a negative association was found. The concentration at which effects became evident (150 200 ng/g wet wt.) was far below effect levels found in laboratory feeding trials or egg injection studies on other avian species. This discrepancy was likely because behavioral effects and other extrinsic factors are not accounted for in these laboratory studies; further, there is a mixture of PFASs in field studies rather than a single-contaminant used in laboratory studies, and the possibility that tree swallows are unusually sensitive to PFASs. Additional field effect studies on other avian species are necessary to address potential for adverse effects of PFASs on bird populations. The results from multistate modeling and simple logistic regression analyses were nearly identical. Multistate modeling provides a better method to examine possible effects of additional covariates and assessment of models using Akaike Information Criteria (AIC) analyses. There was a credible association between perfluorooctane sulfonate (PFOS) concentrations in plasma and eggs so extrapolation between these two commonly sampled tissues can be done. Finally, there was a significant difference in both exposure and PFAS profiles in isolated lakes with different pHs. This is the first time that water chemistry has been associated with differential bioavailability for PFASs in biotic tissues.
