A Toxicological Assessment of Airborne Microplastics in Beijing

Microplastics have emerged as a relatively new type of pollutant and have attracted significant global attention. This study focuses on toxicology of microplastics in ambient PM_2.5 and road dustfall in Beijing. It utilizes the Plasmid Scission Assay to toxicologically evaluate the oxidative damage capacity of microplastics as a component of PM_2.5. The Pollution Load Index (PLI) method, based on the mass concentration of microplastics in ambient air, was employed to assess the ecological risk of atmospheric dustfall microplastics in Beijing. The results showed that both standard microplastic samples and mixed samples of microplastics with ambient PM_2.5 exhibited a dose-response relationship in DNA damage rates. At the same dose, microplastic samples with smaller particle sizes have a higher DNA damage rate. Based on the PLI results, most road dustfall microplastics in Beijing exhibit significant spatial variation. Analysis of road dustfall along the east-west main road across Beijing's urban area revealed that microplastic pollution levels are higher in the eastern zone than in the western zone. Comparisons of pollution levels across functional areas in Beijing showed that university areas > residential areas > industrial areas > commercial areas > agricultural areas. In vertically collected samples, higher elevations (PLI_13.6m = 3.54) exhibit greater pollution levels than lower (PLI_1.5m = 1), which warrants special attention. These findings highlight the complex relationship between atmospheric microplastic accumulation and their oxidative capacity, providing essential insights for the design of targeted emission reduction strategies.