The Global Atmospheric Cycle of Forever Chemicals: A Review of PFAS Distribution, Wet Deposition, and Atmospheric Fate

Abstract

Per- and polyfluoroalkyl substances (PFAS) are persistent, emerging environmental contaminants with diverse chemical properties and widespread industrial and consumer uses. They are used as key components in products like surfactants, lubricants, fire-fighting foams, non-stick cookware, and water-repellent coatings. Additionally, their volatility and stability enable global transport, often reaching pristine environments across various regions. This review thoroughly examines the global literature on atmospheric PFAS, focusing on their distribution in polar, midlatitude, and tropical areas, the role and mechanisms of wet deposition in their atmospheric behavior, and their chemical transformation and phase partitioning in the atmosphere. While midlatitude industrial and consumer activities are primary sources, PFAS are transported globally. Moreover, wet deposition acts as a sink for atmospheric PFAS, with snow and sea spray especially effective at scavenging long-chain PFAS. Although secondary emissions through re-volatilization could occur, the main factors governing the fate of atmospheric PFAS are precursor transformations and phase partitioning. Volatile PFAS degrade in the atmosphere into more persistent and less volatile forms via oxidative and photochemical processes. The partitioning of PFAS between gas and particulate phases depends on functionalization and chain length, with some studies also emphasizing the role of meteorological conditions. Although this review covers a broad range of regions and environments, the existing literature remains limited, especially in areas such as the Antarctic Peninsula, the Middle East, Africa, and Latin America, where data gaps persist. Future research should focus on monitoring PFAS levels in these underrepresented regions and on enhancing the fundamental and mechanistic understanding of PFAS transformation pathways. Meanwhile, policymakers should prioritize implementing stricter emission controls, reforming regulations on legacy and precursor PFAS, and harmonizing PFAS regulations worldwide.