Maternal PFAS transfer through lactation: dolphin milk reveals routes of early-life exposure

Per- and polyfluoroalkyl substances (PFAS) continue to increase in concentration and prevalence in the environment due to the creation of emerging PFAS and the lack of breakdown of legacy compounds. PFAS are known to both bioaccumulate and biomagnify; therefore, species higher on the food chain, such as marine mammals, are highly exposed to these chemicals. Although studies suggest that considerable maternal transfer of persistent organic pollutants occurs via lactation, data are still lacking on the temporal trends associated with PFAS exposure. In this study, we first optimized the extraction for PFAS from 5 and 1 mL of goat's milk using a QuEChERS extraction method to account for precious breast milk samples that are often only available in small volumes. We then utilized a set of dolphin breastmilk samples from an individual mother across a 2-year lactation period to evaluate longitudinal trends in PFAS concentrations and profiles. Thirty PFAS were detected using a multidimensional platform combining liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS), and of these, 20 PFAS were detected continuously across the nursing window of 103-706 days. Quantitative analysis using LC-IMS-MS specifically showed concentrations of perfluorooctanesulfonic acid (PFOS) alone surpass weekly intake recommendations, allometrically scaled to dolphins, from the European Food Safety Authority and Food Standards Australia New Zealand by more than 25-fold. PFOS, however, decreased slightly over time, possibly due to transfer from feedings. Suspect screening and non-targeted analysis also identified 12 compounds including 2 long-chained perfluorosulfonic acids not traditionally evaluated in targeted analyses, as well as the PFOS precursors, perfluoroethylcyclohexane sulfonate (PFECHS) and 2-(N-ethylperfluorooctanesulfonamido) ethyl phosphate (SAmPAP). This study therefore suggests that breastmilk is a major contributor to early-life PFAS exposure for mammals, particularly to long-chained PFAS.