From co-occurrence to co-existence and co-exposure: Associations between per- and polyfluoroalkyl substances and...

Per- and poly-fluoroalkyl substances (PFASs) and microplastics (MPs) are increasingly being recognized as co-occurring emerging contaminants that pose environmental and human health risks. While both pollutant classes have been extensively studied independently, their interactions, combined environmental behavior, and co-exposure pathways remain insufficiently understood. Herein, we identify their common emission sources and overlapping spatial distributions, highlighting the four major anthropogenic sources responsible for their dual emission. Subsequently, we describe their co-existence across environmental compartments, with particular emphasis on adsorption processes, providing strong evidence of their interaction and co-transport. Adsorption efficiency is shown to be strongly influenced by their molecular features (e.g., PFAS structure and polymer type) and environmental conditions (e.g., pH, NOM and ionic strength). Furthermore, we provide the first integrated comparison of their biological transfer processes, including evidence of PFAS and MP co-exposure in humans. Finally, we consolidate these findings into a coherent framework, underscoring the urgent need for standardized analytical protocols, long-term and low-dose exposure studies, and cross-scale approaches that bridge molecular interactions with ecological and human health outcomes.