Health impacts of micro- and nanoplastics: key influencing factors, limitations, and future perspectives

Micro- and nanoplastics (MNPs) are emerging environmental threats, with increasing evidence of their profound ecotoxicological and human health impacts. Although these findings highlight the significant toxicity of MNPs, there has been a lack of systematic discussions on the toxicological impacts from the perspective of the physicochemical properties of MNPs. This gap severely restricts in-depth exploration of their toxicity mechanisms and hinders the development of future toxicity mitigation technologies. This review synthesizes current knowledge on the health effects of MNPs, focusing on the factors influencing their toxicity, such as size, material composition, surface properties, and aging processes. We also explore how MNPs interact with environmental pollutants, accumulate in aquatic and terrestrial organisms, and accumulate in human tissues, leading to oxidative stress, inflammation, and endocrine disruption. Despite growing evidence, critical knowledge gaps remain, particularly regarding the long-term exposure effects, mechanisms of toxicity, and the impact of MNPs on vulnerable populations. We discuss limitations in current detection methods and the need for more comprehensive studies to understand the synergistic effects of MNPs in combination with other pollutants. Finally, future research directions are proposed, emphasizing the need for standardized methodologies, in-depth toxicity mechanisms, and the development of effective mitigation strategies.