Per-and polyfluoroalkyl substances (PFAS) are a group of substances of high environmental and toxicological concern gaining increasing attention due to bioaccumulation and a growing reputation as "forever chemicals" -so much so that there is now a drive to treat PFAS as a class for environmental regulation . The 2011 definition of PFAS by Buck et al. included substances as PFAS if they contained two (or more) connected saturated CF 2 groups. In 2021, the Organisation for Economic Co-operation and Development (OECD) revised the definition of PFAS in ENV/CBC/MONO(2021)25 as follows: "PFAS are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (-CF 3 ) or a perfluorinated methylene group (-CF 2 -) is a PFAS."