The United States Department of Defense is one of the primary stewards of Threatened and Endangered (T&E) species on Federal lands. As part of a Strategic Environmental Research and Development Program project, guidance on the current methods for assessing risks to T&E aquatic life from exposure to per and polyfluoroalkyl substances (PFAS) was developed.
To evaluate risks to aquatic T&E species, over 50 laboratory aquatic toxicity studies on PFAS were reviewed. To reflect a high level of conservatism for T&E species, no observed effect concentrations (NOEC) or 10% effective concentrations (EC10) were compiled for U.S. resident species and reviewed for inclusion in a Species Sensitivity Distribution (SSD) for PFOS and PFOA (no other PFAS met minimum data requirements for SSDs). A total of 82 NOECs for freshwater aquatic species and 14 NOECs for marine aquatic species were included in SSDs for PFOS and PFOA. One percent and five percent hazardous concentrations (HC1 and HC5) were calculated from the SSD following USEPA guidance. HC1 values for PFOS were 0.56 ug/L and 2.57 ug/L for freshwater and marine species, respectively. HC5 values for PFOS were 5.8 and 7.7 ug/L for freshwater and marine species, respectively. The HC1 and HC5 value for PFOA were 537 ug/L and 1,110 ug/L for freshwater species, respectively (data were insufficient for marine species). HC5 values are typically accepted as protective thresholds for aquatic life. Based on the inclusion of NOEC values as the basis for the SSD, the HC5 values reported here are expected to represent conservative thresholds for evaluating risks to aquatic T&E species and aquatic life.