Bioaccumulation and age-dependent risks of per- and polyfluoroalkyl substance (PFAS) in tropical Barn Swallows (Hirundo rustica) from South China

Exposure and risks of per- and polyfluoroalkyl substance (PFAS) to juvenile birds are complex due to the transient nature of biological processes when chicks grow. This study quantified the concentrations of 33 PFASs in environmental media, insects, and eggs, guano, and chicks (aged 1–20 days) of Barn Swallows (Hirundo rustica) from a tropical rural site in South China. Biomagnification factors (BMFs) from insects to swallows were higher than 1, indicating trophic magnification of PFASs in swallows. Non-dietary sources of water and soil ingestion contributed to the bioaccumulation of long-chain perfluorocarboxylic acid in swallows. The concentrations of all PFASs showed a U-shaped trajectory with development of eggs and chicks. The growth of chick body leads to the dilution effect of PFAS concentrations in chicks of 1–13 days, and dietary exposure overwhelms the dilution effect in chicks of 13–20 days. The body burden of PFASs except perfluorooctane sulfonic acid and perfluorooctanoic acid showed a U-shaped trajectory with chick age, because of the compound-specific exposure sources and metabolism processes. Estimated hazard quotients indicated much higher risks for chicks at the first developmental days than eggs and chicks at later developmental period. The human health risk assessment demonstrated that Barn Swallow guano can act as a biovector of PFAS from agricultural fields to indoor environments, and pose potential exposure risks to residents. Overall, these findings highlight the age-dependent dynamics of PFAS exposure and risks in early life period of birds.