ECOTOXICITY AND ACCUMULATION OF PERFLUORONONANOIC ACID (PFNA) IN THE FATHEAD MINNOW (PIMEPHALES PROMELAS) AND AN APPROACH TO DEVELOPING PROTECTIVE THRESHOLDS IN THE AQUATIC ENVIRONMENT THROUGH SPECIES SENSITIVITY DISTRIBUTION.

Per- and Polyfluoroalkyl substances (PFAS) are ubiquitous in the environment. Locations where PFAS-containing Aqueous Film Forming Foam (AFFF) have been used or accidentally released have resulted in persistently high concentrations of PFAS, including in surface water that may be adjacent to release sites. Perfluorooctanesulfonic acid (PFOS) is most frequently measured near AFFF release sites, however, other PFAS are being quantified more frequently and, of those, Perfluorononanoic acid (PFNA) is common. The goal of this study was to fill data gaps on PFNA toxicity to freshwater fish using the fathead minnow (Pimephales promelas). We aimed to understand how PFNA may impact apical endpoints following a 42-day exposure to mature fish and a 21-day exposure to second generation larval fish. Exposure concentrations were 0, 124, 250, 500 and 1000 µg/L for both adult (F0) and larval (F1) generations. The most sensitive endpoint measured was development in the F1 generation at concentrations ≥ 250 µg/L. The 10 and 20% effective concentration (ECx) of the tested population for the F1 biomass endpoint was 100.3 and 129.5 µg/L, respectively. These data were collated with toxicity values from the primary literature on aquatic organisms exposed to PFNA for sub-chronic or chronic durations. A species sensitivity distribution was developed to estimate a screening-level threshold for PFNA. The resulting Hazard Concentration protective of 95% of the freshwater aquatic species (HC5) was 55 µg PFNA/L. While this value is likely protective of aquatic organisms exposed to PFNA, it is prudent to consider organisms experience multiple stressors (including many PFAS) simultaneously; an approach to understand screening-level thresholds for PFAS mixtures remains an uncertainty within the field of ecological risk assessment.