The U.S. Environmental Protection Agency released a final rule Friday to designate two types of PFAS chemicals as hazardous substances. Those two chemicals are perfluorooctanoic acid, also known as PFOA, and perfluorooctanesulfonic acid, or PFOS. PFOA is the chemical that DuPont formerly used to make Teflon while PFOS was used as an ingredient in 3M’s Scotchgard.