PFAS, short for per- and polyfluoroalkyl substances, are a group of more than 4,700 synthetic chemicals created to repel water, oil, grease and stains.  The chemicals, dating to the 1940s and nearly indestructible over time, appear in a range of industrial and everyday consumer products, including makeup, food wrappers, nonstick cookware, carpets, stain repellants, and firefighting foams. 

Because PFAS have been so widely used, most Americans have been exposed to them.

Based on research cited by the State Water Resources Control Board, PFAS can enter the body through various routes, including the consumption of contaminated food or liquids (including water), inhalation of PFAS particles, and contact with products treated with PFAS, such as carpets or clothing.