Throwing off the long chains: Maternal transfer of perfluoroalkyl acids increases with chain length in an Arctic seabird

Per- and polyfluoroalkyl substances (PFAS) are persistent and bioaccumulative synthetic chemicals that can impair wildlife reproduction and development. In birds, maternal transfer is a key pathway of contaminant exposure for developing embryos; yet patterns of PFAS accumulation and transfer to eggs remain poorly understood, especially for emerging PFAS replacements. We examined the occurrence, concentrations, and maternal transfer of legacy and emerging PFAS in adult plasma and eggs of thick-billed murres breeding at Coats Island (Nunavut, Canada). Among 17 legacy PFAS analyzed in birds, the perfluoroalkyl acids (PFAAs) grouped as perfluorinated carboxylic (PFCAs) and sulfonic acids (PFSAs), perfluorooctane sulfonate (PFOS) and six long-chain PFCAs (C₉-C₁₄) were detected in >70 % of adults and eggs, with odd-chain length PFCAs being predominant. Perfluorooctane sulfonamide (FOSA) was also frequently detected, likely contributing to PFOS accumulation in murres. Targeted emerging PFAS were shorter-chain and replacement PFAAs which were generally detected at low frequencies and concentrations. Yet, FBSA, PFEtCHxS, and 9Cl-PF3ONS were measurable in adults or eggs, indicating that emerging PFAS are entering Arctic ecosystems. Maternal transfer ratios were positive for most PFAAs and increased with PFCA carbon chain length, plausibly explained by greater binding affinity of long-chain PFCAs to phospho- and lipo-proteins that facilitate their transfer and accumulation in eggs. Egg production therefore constitutes a major depuration pathway for females, which exhibited significantly lower PFAA concentrations than males. Our results reveal exposure of Arctic seabirds to both legacy and emerging PFAAs, calling for long-term monitoring to assess how exposure pathways respond to legislative restrictions in a rapidly changing Arctic environment.