A critical review of the application of polymer of low concern and regulatory criteria to perfluoropolyethers

Abstract

Perfluoropolyethers (PFPEs) are a class of per- and polyfluoroalkyl substances (PFAS) that are widely used as synthetic oils in various industries including space, health, semiconductor, electronics and automotive, due to their unique physical and chemical properties. To the best of our knowledge, PFPEs have not yet been evaluated using the Polymers of Low Concern (PLC) criteria. The objective of this study is to provide a brief overview of four commercially available PFPEs including their synthesis, typical applications, and evaluate them using PLC criteria. PFPEs are large molecular weight polymers with a narrow molecular weight distribution that makes them markedly different than non-polymeric PFAS. They are highly insoluble in water and octanol which enables the properties of immobility, non-bioaccumulativity and non-bioavailability in the environment. PFPEs also do not contain any significant amounts of residual monomer or low molecular weight oligomeric leachables as these are removed during the manufacturing processes. They also demonstrate excellent chemical, oxidative, biological, photolytic, and thermal stability under conditions of foreseeable use, and in the environment. Additionally, the life cycle impacts of PFPEs are also briefly discussed and found not to pose any significant risk. Overall, the unique properties of PFPEs as well as life cycle considerations demonstrate that PFPEs are of low concern from human health and environmental impact perspective, and that there is no scientific basis to group them with other non-polymeric PFAS. This study corroborates that PFPEs, like fluoropolymers, need to be evaluated as a separate, distinct class for regulatory risk assessment purposes.