Microplastics as a source of phthalate esters in water: A review on occurrence, release mechanism, and ecological risk assessment.

Microplastics (MPs) are increasingly recognized not only as persistent particulate pollutants but also as active sources and vectors of phthalate esters (PAEs) in aquatic environments. Because PAEs are physically incorporated rather than chemically bonded within polymer matrices, they can be progressively released through leaching, photooxidation, mechanical abrasion, and biological interactions. This review synthesizes current understanding of MP-mediated PAE release, their interactions with co-contaminants, and the implications for ecological exposure. Environmental aging enhances polymer fragmentation and surface oxidation, accelerating additive desorption and altering sorption behavior. Field evidence from major river systems shows that high-molecular-weight PAEs, particularly DEHP and DBP, frequently dominate contamination profiles and contribute most significantly to ecological risk, with cumulative risk quotients (∑RQ) reaching up to 59.22 in heavily impacted watersheds. Ingestion of MPs by aquatic organisms further promotes in situ chemical transfer under gastrointestinal conditions, increasing internal exposure beyond dissolved-phase concentrations alone. Moreover, MPs act as multi-contaminant platforms, facilitating the co-transport of PAEs with metals and hydrophobic organic pollutants, thereby intensifying mixture toxicity and trophic transfer. Collectively, these processes demonstrate that MP-associated PAE release represents a dynamic and sustained pathway of chemical pollution requiring integrated risk assessment and source-control strategies.