16 Feb 2022
What are PFAS?
- Depending on the definition of “PFAS” - also known as per- and polyfluoroalkyl substances - between 4700 and 9000 substances may be labelled as PFAS. Not all PFAS are in commercial use. OECD definition of PFAS (version July 2021): “PFASs 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 (–CF3) or a perfluorinated methylene group (–CF2–) is a PFAS.”1 This definition includes about 9000 PFAS substances with a large variety of properties, including gases, polymers and liquids, as well as hazard profiles. The OECD finds within this grouping approach 24 subcategories.
- ECHA and the 5 competent authorities’ (Netherlands, Germany, Denmark, Sweden, Norway) propose the following definition of PFAS: “PFAS are defined as substances that contain at least one fully fluorinated methyl (CF3-) or methylene (-CF2-) carbon atom (without any H/Cl/Br/I atom attached to it).” This includes about 9000 substances and is similar to the 2021 OECD definition. .
- An early and widely recognized technical definition of PFAS is provided by Buck et al. (2011), who defined PFAS as, “highly fluorinated aliphatic substances that contain one or more carbon (C) atoms on which all the hydrogen (H) substituents (present in the nonfluorinated analogues from which they are notionally derived) have been replaced by fluorine (F) atoms, in such a manner that they contain the perfluoroalkyl moiety CnF2n+1 –.”