Exposure to PFAS induced differential oxidative stress-related responses in nestlings of two resident passerine birds nearby a fluoropolymer production plant

Per- and polyfluoroalkyl substances (PFAS) are a diverse group of chemicals of growing concern due to their persistence and potential impacts on human and environmental health. While the occurrence and toxicity of several legacy PFAS are relatively well understood, knowledge of emerging PFAS, particularly in free-living organisms, remains limited. This study investigated the occurrence and biological effects of a mixture of thirty-eight legacy and emerging PFAS nearby a Fluoropolymer Production Plant (FPP) located in Northwestern Italy. Legacy and emerging PFAS were measured in eggs of two resident passerine species, the European starling (Sturnus vulgaris) and the great tit (Parus major), breeding near the FPP and in an agricultural-rural area (AA). Oxidative stress-related biomarkers, including antioxidant and detoxifying enzyme activities and lipid peroxidation, were assessed in nestling blood samples. PFAS were detected in eggs of both the species, reaching concentrations of Σ21PFAS up to 1451 ng/g f.w. in starlings and 6576 ng/g f.w. in great tits. Eggs collected near the FPP showed PFAS levels up to ten-fold higher than those from the AA, with chloro-perfluoropolyether carboxylic acids (Cl-PFPECAs) dominating the contamination profile. Despite similar exposure patterns, biological responses differed between species. No significant effects were observed in great tit nestlings, whereas starling nestlings breeding near the FPP exhibited altered antioxidant defenses and increased lipid peroxidation, indicating they suffered an oxidative stress condition. These findings demonstrate that environmental exposure to PFAS mixtures near an FPP can induce oxidative stress in free-living birds and highlight the need for further field-based studies to improve understanding of PFAS toxicity and support environmental risk assessment.