PFAS exposure is associated with accelerated epigenetic ageing in a wild marine mammal

Chronic contaminant exposure may impose hidden physiological costs long before obvious demographic or health effects become detectable in wildlife populations. Epigenetic clocks quantify biological ageing and may provide sensitive biomarkers of cumulative toxicological stress. Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants that bioaccumulate in marine food webs, yet their long-term physiological consequences for wildlife remain poorly understood. Here, we tested whether PFAS exposure is associated with accelerated biological ageing in common dolphins (Delphinus delphis). We analysed liver PFAS concentrations and skin DNA methylation profiles from 30 stranded or bycaught dolphins from New Zealand waters. Epigenetic age was estimated using a recently developed species-specific epigenetic clock, and age acceleration was calculated as the residual deviation between epigenetic and chronological age. Using an information-theoretic modelling framework, we assessed the effects of total PFAS burden, sex, and their interactions on epigenetic age acceleration. Total PFAS concentrations were positively associated with epigenetic age acceleration, indicating that dolphins with higher PFAS burdens were biologically older than expected for their chronological age. Each 1 ng/g increase in total PFAS was associated with an average increase of 0.031 years in biological age. Sex did not significantly influence age acceleration, suggesting that PFAS-associated ageing effects occur across both sexes. Although modest, this effect is consistent with PFAS acting as a chronic physiological stressor influencing molecular ageing processes. Our findings provide the first evidence linking PFAS exposure to accelerated biological ageing in a wild mammal, highlighting epigenetic ageing as an integrative biomarker of long-term contaminant effects in wildlife.