Forever Chemicals, Per-and Polyfluoroalkyl Substances (PFAS), in Lubrication

Per- and polyfluoroalkyl substances (PFAS), also known as forever chemicals, exhibit exceptional chemical stability and resistance to environmental degradation thanks to their strong C-F bonds and nonpolar nature. However, their widespread use and persistence have a devastating impact on the environment. This review examines the roles of PFAS in tribological applications, specifically in lubricants and lubricating systems. This article focuses on conventional and advanced lubricants, including ionic liquids (ILs) and their use in modern automotive vehicles. The objective of this paper is to provide a comprehensive overview of the adverse impacts of PFAS whilst acknowledging their outstanding performance in surface coatings, composite materials, and as additives in oils and greases. The pathways through which PFAS are introduced into the environment via lubricating systems such as in seals and O-rings are identified, alongside their subsequent dispersion routes and the interfaces across which they interact. Furthermore, we examine the toxicological implications of PFAS exposure on terrestrial and aquatic life forms, including plants, animals, and humans, along with the ecological consequences of bioaccumulation and biomagnification across trophic levels and ecosystems. This article ends with potential remediation strategies for PFAS use, including advanced treatment technologies, biodegradation, recovery and recycling methods, and the search for more environmentally benign alternatives.