Tracing the environmental lifecycle of nanoparticles: pathways, persistence, and ecotoxicological impacts.

The rapid production and extensive use of nanoparticles (NPs) in biomedical, industrial, agricultural, and environmental technologies have led to increased release into natural ecosystems, heightening concerns about their environmental fate and ecological risks. Nanoparticles, owing to their nan and biological toxicity via three primary mechanismsoscale dimensions and distinctive physicochemical properties, exhibit intricate and dynamic behaviour in environmental systems, undergoing processes such as aggregation, dissolution, surface alteration, and interactions with biotic and abiotic components. These processes regulate nanoparticle transport, persistence, bioavailability, and toxicity, and are significantly affected by environmental variables. Notwithstanding considerable progress in nanotechnology and nanotoxicology, the current understanding of the ecological life-cycle behaviour of nanoparticles remains fragmented, and risk assessment frameworks often fail to account for their dynamic and context-dependent characteristics adequately. This review systematically integrates recent literature on the origins and release mechanisms of engineered, incidental, and naturally occurring nanoparticles; their movement through atmospheric, aquatic, and terrestrial environments; and the principal physicochemical and biological transformation processes that govern their environmental fate. The review assesses the ecological implications of nanoparticles across trophic levels and highlights significant knowledge gaps, methodological constraints, and research needs. This review seeks to enhance environmental risk assessment methodologies and facilitate the development of safer, more sustainable nanomaterials by adopting a life-cycle perspective.