The toxicity and bioaccumulation of PFAS in earthworms ( Eisenia fetida ) exposed to biosolids-amended agricultural soils

The accumulation of per- and polyfluoroalkyl substances (PFAS) in agricultural soils poses a potential threat to both human health and the environment. A proven pathway through which these persistent organic pollutants can enter the soil is through the application of biosolids and irrigation water. Earthworms, an integral component of ecosystems, play a crucial role in improving soil health and crop productivity. Understanding the impact of PFAS on earthworms is essential for comprehending the broader ecological implications. In this study, we investigated the concentrations of 38 PFAS in earthworms exposed to field-collected agricultural soils amended with biosolids. The highest measured concentration of these ∑38PFAS in biosolids-amended agricultural soil samples reached 104.02 ng g-1 dry weight. Particularly noteworthy was the elevated concentration of the legacy PFAS, perfluorooctanesulfonate (PFOS), which peaked at 48.1 ng g-1 dry weight with an average of 19.66 ng g-1 in soils. Conducting acute, chronic and cyto-genotoxicity studies with E. fetida (earthworm) revealed no lethality in biosolid-amended soils. Weight loss in exposed worms was not significant and was comparable to that of the control group. The bioaccumulation of ∑38 PFAS in the earthworms exposed to biosolids-amended soils ranged from 9.54 to 31.79 ng g-1. The earthworm-to-soil PFAS concentration ratio (CR) values indicated the following order of accumulation in earthworms: Perfluorobutane sulfonate (PFBS) > Perfluorobutanoic acid (PFBA) > Perfluorohexane sulfonate (PFHxS) > Perfluorooctanoic acid (PFOA) > PFOS. These findings highlight the need for further research on the chronic effects of PFAS, extending beyond PFOS and PFOA exposure. A holistic approach to PFAS contamination is crucial to ensure the long-term viability of ecosystems. Future research should investigate the trophic transfer of accumulated PFAS to higher organisms to address critical knowledge gaps in PFAS bioaccumulation dynamics and associated ecological impacts.