Critical evaluation of ECOSAR and E-FAST platforms to predict ecological risks of PFAS

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment. Unlike other persistent chemicals, PFAS are highly soluble in water and tend to partition to surface and groundwater rather than soil and sediment. While numerous studies have evaluated the potential ecological effects of certain PFAS, there remain data gaps, especially for newer PFAS. Consequently, this study evaluated a high-throughput in silico approach for a screening-level risk assessment of PFAS in aquatic species. We focused on two well-studied PFAS, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), to provide a better context to our estimates. The Ecological Structural Activity Relationships (ECOSAR) program was used to estimate acute and chronic toxicity thresholds for fish, Daphnid, mysid, and green algae. The Exposure and Fate Assessment Screening Tool (E-FAST) model was used to derive estimated environmental concentrations (EECs) in surface water following hypothetical discharges from wastewater treatment plants (WWTPs). The predicted toxicity thresholds and EECs were compared to reported values. Subsequently, risk quotients (RQs) were calculated. We showed that (1) the acute toxicity thresholds for PFOA and PFOS were typically lower (i.e., more conservative) than reported values, whereas chronic toxicity thresholds were typically in the range of reported values, (2) the EECs were in the range of reported environmental concentrations in most cases, and (3) the acute and chronic RQs were mostly below the levels of concern. Additionally, the study highlighted that even for the well-studied PFOA and PFOS, there were still data gaps with regards to ecotoxicity in certain aquatic species as well as environmental concentrations for certain water bodies.