Abstract
Per- and polyfluoroalkyl substances (PFAS) have historically been a key component in aqueous film-forming foams (AFFF) used in fire suppression. With the increasing emphasis on phasing out PFAS use due to health and environmental concerns, several new chemical technologies have been used to create fluorine-free foam (F3) alternatives. Recent research has demonstrated that these replacement formulations are more acutely toxic to aquatic species than the traditional PFAS-containing AFFF. Given their relatively high acute toxicity, prolonged exposure to the formulations could lead to adaptive responses (i.e., evolved tolerance) in exposed populations. In this study, we examined the effects of chronic exposure to six F3 alternatives and one PFAS-containing AFFF on tolerance to the formulations in the water flea Daphnia magna . Following an 84-day exposure to different concentrations of each formulation, we used a series of laboratory lethal concentration (LC 50 ) tests on a subset of populations to examine the potential change in tolerance. We found that chronic exposure to three formulations led to a change in tolerance in exposed populations as compared to those with no prior exposure; two populations displayed increased tolerance while one showed decreased tolerance. This work is the first to examine evolved responses to F3 alternatives. Our results highlight the frequently overlooked evolutionary effects of contaminant exposure and the broader need to understand the effects of F3 alternatives on the environment.