Establishing Chronic Toxicity Effect Levels for Zebrafish (Danio rerio) Exposed to Perfluorooctane Sulfonate (PFOS).

Zebrafish (Danio rerio) are among the aquatic species most sensitive to perfluorooctane sulfonate (PFOS). Environmental regulatory agencies and researchers use effect benchmarks from laboratory zebrafish PFOS toxicity studies in PFOS-spiked water to calculate PFOS aquatic life criteria. Threshold values as low as 0.7 micrograms per liter (µg/L; identified in an early, limited scope study) have been used in criteria derivation and site-specific aquatic ecological risk assessments. This paper reviews PFOS effects benchmarks for lethality, growth, and reproduction endpoints from more than 20 zebrafish toxicity studies, including a recent multi-generational study (Gust et al., submitted) conducted by the United States Army Corps of Engineers Engineer Research & Development Center (ERDC). This review of 12 key studies examining long-term, chronic exposures (including multigenerational exposures of 300 days or more) indicated that 0.7 µg/L should not be used as a conservative screening threshold given that effects could not be repeated at this concentration by the recent, enhanced multigenerational study. Based on this finding and multiple chronic sublethal studies on PFOS in zebrafish, chronic effects on lethality, growth, and reproduction occur at concentrations two orders of magnitude higher than 0.7 µg/L. Overall, this review indicates a no-effect screening level of 31 µg/L and a low-effect screening level of 96 µg/L should be used to develop PFOS aquatic life criteria and to inform site-specific ecological risk assessments that are charged with evaluating risks to freshwater fish.