PFAS (Perfluoroalkyl and Polyfluoroalkyl Substances) are polymers that involve chains of Carbon and Fluorine, the two atoms that form the strongest bond in organic chemistry. PFAS are used in the production of many polymers and coatings, especially plastics and rubbers.
The strong bonds of PFAS causes them to only break down under high heat. PFAS do not occur naturally and once they enter the water supply, they never fully decompose. Plastics in bodies of water just break into smaller microplastics and cycle through the water supply.