“PFAS”—short for per- and polyfluoroalkyl substances—are chemicals used to repel water, grease, and stains. They are often found in household products like nonstick pans (e.g. “Teflon”), food packaging, waterproof jackets, and carpets; personal care products like waterproof mascaras and eyeliners, sunscreen, shampoo, and shaving cream; and firefighting foam on military bases and commercial airports.