Microplastics as Silent Invaders: A Multiscale Review of their Toxicological Effects and Contaminant Interactions in Terrestrial and Aquatic Environments

Microplastics (MPs), often termed “silent invaders,” have become ubiquitous pollutants across both terrestrial and aquatic environments, raising significant concerns in respect of their toxicological and ecological consequences. This review provides an in-depth multiscale evaluation of the toxic effects of microplastics, from molecular disruptions to ecosystem-level disturbances. Special priority is placed on the capacity of microplastics to act as vectors for a range of environmental contaminants, including heavy metals, persistent organic pollutants, and pharmaceuticals, thereby amplifying their toxic potential. This review also examines how microplastics interact with biological systems, triggering oxidative stress, inflammation, genotoxicity, endocrine disruption, and behavioural changes in organisms across various trophic levels. Comparative insights between terrestrial and aquatic systems divulge distinct exposure pathways and species-specific vulnerabilities, with remarkable research gaps persisting in soil ecosystems. Moreover, the review discusses current advances and limitations in detection methods and toxicological assays, while highlighting censorious needs for standardized protocols and long-term ecological studies. Ultimately, this synthesis underscores the urgent necessity for transdisciplinary research and regulatory frameworks to address the escalating risks posed by microplastics and their associated contaminants in global ecosystems.