Environmental Fate and Ecological Risk of Micro- and Nanoplastics across Terrestrial and Aquatic Ecosystems

Microplastics (MPs) and nanoplastics (NPs) are emerging contaminants widely distributed across terrestrial and aquatic ecosystems. This review synthesizes current understanding of their sources, environmental fate, transport pathways, and ecological effects, while critically evaluating existing risk assessment approaches and identifying key knowledge gaps. Terrestrial soils function as major sinks and secondary sources, transferring plastics to freshwater and marine systems via runoff, erosion, and atmospheric deposition. In aquatic environments, particle behavior is governed by size, density, aggregation, and biofouling, influencing vertical distribution and biological exposure. Evidence demonstrates ingestion, physiological stress, and trophic transfer across multiple taxa; however, environmentally realistic dose–response relationships remain uncertain. Major uncertainties concern nanoplastic detection, chronic and multigenerational impacts, and interactions with co-occurring stressors. Current ecological risk frameworks are limited by methodological heterogeneity and sparse nanoplastic data. Advancing harmonized monitoring methods, long-term field studies, and integrative risk models is essential for translating scientific knowledge into effective environmental management and policy.