The influence of environmental and ecological factors on the accumulation and distribution of short- and long-chain perfluoroalkyl acids in a mid-trophic avian insectivore.

Perfluoroalkyl acids (PFAAs) include perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), and perfluorodecane sulfonic acid (PFDS), as well as increasingly used alternative short-chain perfluorosulfonic acids (PFSAs) and short- and long-chain (≥C) perfluorocarboxylic acids (PFCAs). In the present study, tissues of tree swallows (Tachycineta bicolor) from two sites in southern Ontario, Canada, were analyzed for 17 individual PFAAs and showed egg and nestling tissue (liver, carcass) profiles dominated by PFOS (57-66%). The remaining PFAAs contributed ≤7% each, although collectively the long-chain PFCAs comprised 21-29% of the PFAAs. The short-chain PFSAs and PFCAs were among the lowest concentrations, suggesting that despite increased production and use of these alternative PFAAs, they are not accumulated to the same extent as the long-chain PFSAs and PFCAs. PFOS, PFDS, and some long-chain PFCAs were significantly higher in eggs than in livers and carcasses, whereas PFOA and the two short-chain PFCAs were significantly higher in nestling tissues than in eggs. For the two short-chain PFSAs, concentrations were similar among tissues. Tree swallow tissues at the site near a wastewater treatment plant (WWTP) outfall showed higher concentrations of PFOS, PFDS, PFHxS, and some long-chain PFCAs than tree swallows sampled at the nearby reference site; however, the influence of the WWTP was more equivocal for PFOA, other long-chain PFCAs, and short-chain PFSAs and PFCAs. Carbon stable isotopes (δC) and fatty acid signatures indicated that the diets of the WWTP swallows were more terrestrial than the reference swallows. Nonetheless, models considering environmental and ecological variables indicated that site was often the primary driver of PFAA variation among the swallows, with less or no influence of dietary patterns, or sex or body condition, revealing that of WWTP effluent can be an important environmental source of the major PFAAs in tree swallows.