Microplastics as vectors for environmental contaminants in the food chain: Assessing the combined toxicological effects and bioavailability

The global proliferation of microplastics (MPs) and nanoplastics (NPs) has raised concerns not only for their persistence in ecosystems but also for their role as transport agents of environmental contaminants through food chains. This review provides a comprehensive analysis of the mechanisms driving the sorption and desorption of diverse pollutants-including hydrophobic organics, metals, additives, and microbial agents-onto plastic particles, emphasizing how polymer composition, particle size, environmental aging, and eco-corona formation influence these interactions. Particular attention is paid to the transfer of MPs/NPs across trophic levels and their documented presence in various food items consumed by humans. The paper evaluates how ingestion may lead to desorption of contaminants in gastrointestinal environments, with in vitro studies demonstrating variable bioaccessibility depending on physicochemical and digestive conditions. Furthermore, the review synthesizes findings on cellular and systemic toxicity, highlighting how exposure to MPs/NPs-alone or in combination with other contaminants-can disrupt oxidative balance, immune responses, metabolic regulation, and reproductive health. Notably, combined exposures often result in synergistic or antagonistic effects, contingent on concentration, particle properties, and biological context. The potential for translocation of smaller particles and their associated chemicals across epithelial barriers introduces an additional vector of concern for internal exposure. Methodological variability in contamination assessment, limited real-world exposure data, and unresolved questions regarding long-term health consequences underscore the need for standardization and further investigation. This review aims to inform future risk assessments by integrating current knowledge of contaminant transport, bioavailability, and co-toxicological effects related to MPs/NPs in environmental and food systems.