A Legacy of Exposure: Lactational PFAS Transfer and Early-Life Accumulation in Northern Elephant Seals

Although PFAS are widely acknowledged as ubiquitous and persistent organic pollutants, critical gaps remain in mapping environmental distribution and clarifying health-relevant exposure pathways, especially in early life. Marine mammal milk provides a unique window into both environmental occurrence and intergenerational transfer, especially in capital-breeding species in which lactation occurs during prolonged fasting with rapid lipid mobilization. Here, we investigated PFAS burdens and maternal transfer in the northern elephant seal (Mirounga angustirostris). Elephant seals, with highly characterized nursing behavior and foraging patterns, serve as a valuable sentinel for modeling both patterns of lactational transfer and assessing PFAS concentrations in deep-ocean ecosystems. This study assessed plasma from 14 mother-pup pairs and milk from 9 mothers using a non-targeted data acquisition platform coupling liquid chromatography, ion mobility spectrometry, and high-resolution mass spectrometry (LC-IMS-HRMS). Twenty-seven PFAS were identified across all matrices and age groups, and quantitative analyses revealed concentrations in milk and plasma that exceeded relevant human-based exposure and dietary intake thresholds. Across all pairs, pup plasma PFAS concentrations were consistently higher than maternal concentrations. Specifically, the highest PFAS concentrations were observed in weaned pups (average ∑16 PFAS = 89.08 ng/mL), indicating pronounced early-life accumulation and/or redistribution during the postweaning fast. Concentrations of PFAS in the milk also correlated with maternal and pup plasma levels, demonstrating pair-specific contaminant profiles. Suspect screening further illustrated matrix- and lineage-specific exposure patterns within matched mother-pup pairs, consistent with shared foraging grounds and lactational transfer mechanisms. Together, these findings indicate that neonatal marine mammals in extreme capital-breeding systems experience elevated PFAS body burdens during sensitive developmental windows.