Scientists’ Statement on the Chemical Definition of PFASs

The undersigned are scientists with expertise in per- and polyfluoroalkyl substances (PFASs) and/or the management of chemicals. We assert that the Organization for Economic Co-operation and Development (OECD) definition of PFASs is scientifically grounded, unambiguous, and well suited to identify these chemicals. We are concerned that some individuals and organizations are seeking a redefinition of PFASs endorsed by the International Union of Pure and Applied Chemistry (IUPAC) to exclude certain fluorinated chemical subgroups from the scope of the existing definition. We are concerned that this effort is politically and/or economically, rather than scientifically, motivated. An IUPAC-endorsed and potentially narrower PFAS definition could confer undue legitimacy from the endorsement by a recognized global scientific organization and, thereby, influence regulatory bodies and others to adopt less protective policies. Organofluorine chemicals are used in consumer products and industrial applications to impart oil-, water-, and stainresistance, stability, inertness, and/or other useful properties. The term “PFASs” arose from the need to identify a subgroup of organofluorine chemicals with a common feature, the very stable perfluorinated carbon. There are millions of theoretical PFAS structures, but the much lower number of PFASs actually manufactured and used is estimated to be several thousands.