Toxicological Differences Between Perfluoroalkyl Substances (PFAS) Isomers Using Developmental Biomarkers

Perfluoroalkyl substances (PFAS) are metabolically stable synthetic chemicals that have been manufactured for commercial and industrial purposes since the 1950s. PFAS possess surfactant properties that make them ideal to fight hydrocarbon fires and are therefore present in aqueous film forming foams (AFFF). Furthermore, AFFF may contain blends of both linear and branched PFAS isomers. Research suggests that branched PFAS isomers have greater relative placental transfer efficiencies than their linear counterpart, but few studies have evaluated their toxicity. Therefore, the sustained use of AFFF in the U.S. Air Force presents a risk of branched PFAS exposures in pregnant females. This study investigated the toxicological differences between branched and linear PFAS isomers in vitro using the JEG-3 human placental cell-line as a model. Cells were exposed to linear and branched perfluorohexane sulfonate (PFHXS) for 24 to 48 hours at concentrations ranging from 0.2 M to 50 M. Subsequently, changes in three specific biomarkers were examined. No significant statistical differences in cellular proliferation and cellular viability were highlighted in cells exposed to both compounds at equivalent concentrations; however, mean cell proliferation appeared greater when exposed to linear PFHxS. Reactive oxygen species (ROS) generation was statistically higher in JEG-3 cells exposed to branched PFHxS isomers at corresponding concentrations