When co-occurrence becomes risk: a SOURCE-FATE-DOSE-EFFECT-DECISION framework for microplastic-PFAS interactions, food-chain transfer, and dietary safety

Microplastics and per- and polyfluoroalkyl substances (PFAS) co-occur across wastewater, landfill leachate, sediments, agricultural soils, stormwater, aquatic food webs, and food-contact systems, yet their risks are often assessed separately. We synthesize quantitative evidence showing that PFAS sorption and release from microplastics depend on polymer identity, PFAS chain length, particle size, field conditioning, and matrix chemistry. Reported patterns include chain-length-dependent sorption, field enrichment on environmentally conditioned particles, greater PFOS sorption by smaller polyethylene particles, and 76.8-77.6% PFOS release from polyethylene microplastics under simulated fish digestive conditions. We propose a SOURCE-FATE-DOSE-EFFECT-DECISION (SFDED) framework that classifies microplastics as sinks, vectors, secondary sources, or co-stressors according to role-specific evidence requirements and extends these roles to farm-to-fork pathways. The framework distinguishes co-occurrence, bioaccessibility, absorbed internal dose, and biological effect, and links research goals to the minimum measurements needed to support each claim. Applying this framework identifies seven priority gaps: human gut-fluid desorption, mammalian internal dosimetry, mixture toxicity in human-relevant systems, dietary PFAS exposure estimation, food-related microplastic standards, treatment removal of particle-bound PFAS, and systematic synthesis across a broader primary-study base. Together, this approach provides a transparent basis for interpreting microplastic-PFAS interactions and prioritizing evidence needed for food-safety assessment, monitoring, treatment decisions, and risk management.