Examination of the reproductive effects of fluorine-free foam alternative exposure on fathead minnows ( <i>Pimephales promelas</i> )

Aqueous film forming foams (AFFF) containing per- and polyfluoroalkyl substances (PFAS) have been used for decades to fight fuel-based fires. Given the known health risks of PFAS to wildlife and humans, there has been an increasing focus on developing fluorine-free foam (F3) alternatives as replacements. Before F3 alternatives are widely adopted, it is important to assess their potential ecological risk. We evaluated the reproductive and physiological effects of six F3 alternatives and one AFFF on the fathead minnow (Pimephales promelas) using 21-day chronic exposure tests. Of the tested formulations, one F3 (Naval Research Laboratory 502 W, 502 W) and the AFFF (Buckeye Platinum Plus C6 MILSPEC 3%, Buckeye) exhibited the most significant reproductive toxicity. For 502 W, daily egg production per female was 81 to 82% lower at the two highest concentrations compared to the control. For Buckeye, daily egg production per female was 78 to 97% lower and 63 to 93% fewer reproductive events occurred at the two highest concentrations compared to the control. Female gonadosomatic index (GSI) was 34% and 32% lower at the highest concentrations of 502 W and Buckeye, respectively, compared to their controls. Additionally, hepatosomatic index (HSI) of females was 45% greater at the highest concentration of Buckeye compared to the control. Male GSI decreased in one concentration of one F3 formulation and HSI increased in one concentration for three F3 formulations. Overall, our results suggest that adult fathead minnows were relatively tolerant of F3 alternatives with effects largely observed at the highest concentrations. Given that previous work has documented that larval fathead minnows are sensitive to F3 alternatives, future work conducting exposures through maturation is recommended to assess potential long-term reproductive effects.