Per- and Polyfluoroalkyl Substances (PFASs) in Aquatic Birds of the Ravi and Sutlej Rivers, Punjab, Pakistan: Insights from Feather Analysis

Per- and polyfluoroalkyl substances (PFASs) are a diverse group of persistent synthetic chemicals that are distributed globally in aquatic environments and biota. Despite increasing concern regarding their ecological and health impacts, data from South Asia, mostly concerning wildlife exposure, remain limited. In this study, a nonlethal biomonitoring approach was employed to quantify perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in feathers of aquatic birds inhabiting the Ravi and Sutlej Rivers in Punjab, Pakistan. Feathers from three waterbird species, the common kingfisher ( Alcedo atthis ), white-throated Kingfisher ( Halcyon smyrnensis ), and white egret ( Ardea alba ), were collected from multiple river sections and analyzed via liquid chromatography–tandem mass spectrometry (LC–MS/MS). PFOSs and PFOAs were detected in all the species, with significant interspecific and spatial variation. The mean PFOS concentrations ranged from 2.64 to 5.97 ng/g, whereas the PFOA concentrations ranged from 3.81 to 15.32 ng/g across species. White-throated Kingfishers presented the highest PFOA burdens, whereas White Egrets presented the highest PFOS concentrations. These findings provide the first baseline evidence of PFAS accumulation in aquatic birds from major river systems in Pakistan and highlight the utility of feathers as effective bioindicators of PFAS exposure in freshwater ecosystems. The results contribute to the growing global dataset on PFAS contamination and underscore the need for further monitoring in understudied regions.