PFAS in the circular economy: An unintended consequence of recycling and wastewater reuse?

Abstract

The circular economy has emerged as one of the most prominent sustainability paradigms of our time, promising to decouple economic growth from resource depletion through strategies centred on recycling, reuse, and resource recovery. Governments, industries, and international organisations have invested heavily in closing material loops, from wastewater reclamation for agricultural irrigation to the land application of biosolids as soil amendments, and from paper and textile recycling to composting of organic waste. These practices are essential pillars of a resource-efficient future. However, as circular economy pathways expand in scale and ambition, an uncomfortable question is surfacing with increasing urgency: Are we inadvertently recycling persistent contaminants alongside the resources we seek to recover? Among the most concerning of these contaminants are per- and polyfluoroalkyl substances (PFAS), a diverse class of synthetic chemicals whose extraordinary environmental persistence has earned them the moniker “forever chemicals” (Evich et al., 2022). Per- and polyfluoroalkyl substances encompass over 12,000 individual substances characterised by exceptionally strong carbon-fluorine bonds that resist thermal, chemical, and biological degradation (Brunn et al., 2023). These properties, which make PFAS invaluable in industrial and consumer applications ranging from nonstick coatings and water-repellent textiles to food packaging and firefighting foams, also render them virtually indestructible in natural systems. Once released into the environment, PFAS persist indefinitely, accumulating in soils, water bodies, biota, and human tissues. Cousins et al. (2020) have argued persuasively that the extreme persistence of PFAS alone is sufficient justification for their management as a chemical class, irrespective of individual toxicological profiles, because environmental contamination by these substances is essentially irreversible.