The Microplastic–PFAS Nexus: From Co-Occurrence to Combined Toxicity in Aquatic Environments

The pervasive environmental contamination by microplastics (MPs) and per- and polyfluoroalkyl substances (PFAS) represents a critical challenge of the Anthropocene. While historically studied in isolation, a growing body of evidence confirms that these pollutants interact to form a complex and dynamic MP-PFAS Nexus. This review synthesizes current knowledge to elucidate the multifaceted mechanisms of this interaction, where MPs act as vectors, concentrators, and secondary sources for PFAS. We detail how environmental aging and water chemistry modulate adsorption and transport, fundamentally altering the fate of both contaminants. Crucially, the review consolidates evidence demonstrating that co-exposure often leads to synergistic toxicity, disrupting physiological processes from photosynthesis in algae to lipid metabolism and neurogenesis in animals, with significant implications for trophic transfer. The nexus also presents formidable challenges for water treatment and soil remediation, while simultaneously offering opportunities for targeted destructive technologies like pyrolysis. Furthermore, we explore the emerging threats of this complex to human health via seafood and water, and the amplifying feedback of climate change. Finally, we argue that current regulatory frameworks, which assess pollutants individually, are inadequate and must evolve to account for combined effects. This review underscores the imperative to reframe MPs and PFAS as an interconnected pollutant system, necessitating integrated research and policy for effective environmental risk assessment and management.