Perfluoroalkyl substances (PFAS) are highly versatile chemicals. These fluorine-containing organic molecules are the reason why rain drops simply slide off outdoor jackets. They are used in the greaseproof coating of paper food packaging and are key ingredients in fire-extinguisher foams and the protective gear worn by firefighters. PFAS were first introduced in the 1940s and since then, the number of products and areas in which they are used has grown astronomically.