Tree swallows as indicators of per- and polyfluoroalkyl substance exposure and effects at select Department of Defense sites along the East Coast and at sites with different sources in the Upper Midwest, United States

Questions remain about the distribution of per- and polyfluoroalkyl substances (PFAS) in the environment, the sources and movement within and between ecosystems, and whether there are effects from such exposure. Information from the Upper Midwest and the mid-Atlantic regions of the United States, which have different PFAS sources, were investigated. Concentrations of Total40 (sum of 40 PFAS), perfluorooctane sulfonate, perfluorohexane sulfonate, and Total13 (sum of 13 PFAS) were consistently higher, by as much as a factor of 40, in tree swallow (Tachycineta bicolor) tissue samples (eggs, nestlings, and diet) at sites along the East Coast, where aqueous film-forming foams (AFFF) were extensively used when compared with East Coast reference sites. Sites in the Upper Midwest, with other PFAS sources, had qualitatively lower concentrations of PFAS than AFFF source sites. Perfluorooctane sulfonate was the only PFAS detected in all samples. Concentrations of most other PFAS, such as the carboxylates and fluorotelomers, did not differ between AFFF and reference sites. Perfluorohexane sulfonate, the second-most common constituent of some legacy AFFF formulations, was <1% of Total40 at the reference sites in eggs and nestlings, but perfluorohexane sulfonate represented up to 9.7% (eggs) and 9.0% (nestlings) at AFFF-influenced sites. Despite differences in PFAS exposure, the daily probability of egg and nestling survival, as well as haptoglobin-like activity (PIT54) and total immunoglobulin Y, was similar across all sites. There were also no significant associations between these end points and concentrations of Total40 or individual PFAS in eggs or nestlings.