A comprehensive review on microplastics as vectors of chemical and biological pollutants

The increase in microplastics has the potential to cause harm to ecosystems and can also create a hazard through their role as a ‘transport vector’. This review offers a novel contribution by systematically mapping evidence from multiple studies. We present a synthesis of various pollutant categories and polymer types across both aquatic and terrestrial environments, providing a broader understanding of MPs’ role in pollutant transport. This study emphasizes the importance of real-world environmental factors, such as surface properties, pollutant characteristics, environmental conditions, and biofilms, that influence the adsorption and desorption of pollutants on MPs. By integrating the effects of biofilm formation and aging into a unified framework and comparing MPs with natural particles, we offer a nuanced perspective on how these factors jointly affect pollutant dynamics. Our findings highlight the complex, context-dependent nature of MPs as vectors and link it to raising concerns about pollutant bioavailability and ecological risks. Our evidence suggests that pollutant-loaded MPs are more toxic than unbound pollutants and contribute to bioaccumulation in aquatic and terrestrial organisms. This review extends previous models, which focused on general adsorption principles derived from laboratory studies, by incorporating real-world dynamics and critically assessing the limitations of existing research. We emphasize the need for further studies in environmentally relevant conditions to better understand the ecological risks posed by MPs, which is essential for the development of effective mitigation strategies and informed policy decisions.