Ecological and Health Risk Mediated by Micro(nano)plastics Aging Process: Perspectives and Challenges

Aged micro­(nano)­plastics (MNPs) are normally the ultimate state of plastics in the environment after aging. The changes in the physical and chemical characteristics of aged MNPs significantly influence their environmental behavior by releasing additives, forming byproducts, and adsorbing contaminants. However, a systematic review is lacking on the effects of aged MNPs on ecological and human health regarding the increasing but scattered studies and results. This Review first summarizes the unique characteristics of aged MNPs and methods for quantifying their aging degree. Then we focused on the potential impacts on organisms, ecosystems, and human health, including the “Trojan horse” under real environmental conditions. Through combining meta-analysis and analytic hierarchy process (AHP) model, we demonstrated that, compared to virgin MNPs, aged MNPs would result in biomass decrease and oxidative stress increase on organisms and lead to total N/P decrease and greenhouse gas emissions increase on ecosystems while causing cell apoptosis, antioxidant system reaction, and inflammation in human health. Within the framework of ecological and human health risk assessment, we used the risk quotient (RQ) and physiologically based pharmacokinetic (PBK) models as examples to illustrate the importance of considering aging characteristics and the degree of MNPs in the process of data acquisition, model building, and formula evaluation. Given the ecological and health risks of aged MNPs, our urgent call for more studies of aged MNPs is to understand the potential hazards of MNPs in real-world environments.