Microplastics as Emerging Contaminants: Pathways, Environmental Persistence, and Human Health Implications

Microplastics (MPs) have emerged as persistent environmental contaminants due to their persistence, widespread distribution, and potential risks to the environment and human health. This review focuses on the sources of MPs, their potential environmental risks, and human impacts, as documented in the recent literature from 2020 to 2026. Recent studies focusing on pathways, environmental weathering, and toxicity were evaluated and synthesized into the analysis. Previous studies have demonstrated that microplastics are transported across and between environmental compartments. Environmental degradation, driven by ultraviolet radiation, mechanical fragmentation, and oxidation, can alter microplastics’ surface characteristics, which may affect microplastic mobility, reactivity, and the solid-state adsorption of contaminants. Human exposure occurs primarily through ingestion and inhalation, with dermal and occupational exposure also contributing under certain conditions. Emerging evidence from in vitro, animal, and human tissue studies suggests that smaller particles, particularly nanoplastics, may contribute to oxidative stress, inflammation, and cellular injury; however, important uncertainties remain regarding environmentally realistic exposure levels, long-term health outcomes, and the extrapolation of experimental findings to real-world human health risk. Overall, the current literature highlights the need for standardized methodologies, improved integration of environmental monitoring and exposure assessment, and stronger evidence to support risk assessment and policy development.