in case you're like me and didn't know, PFAS refer to per- and polyflyoroalkyl substances, which seem to be correlated with negative health outcomes (re: developmental problems, cancer, fertility issues, etc) and are particularly tricky because they take a long time to break down.
they're highly hydrophobic substances used in e.g. teflon. their use has decreased as we've come to understand their harms more, but we're still dealing with the results of their high usage from the past. certain industries seem to still use it (stain repellants, polishes, paints, coatings)