Size Distribution of Micro-/Nanoplastic Particles and Their Chemical Speciation in the Atmosphere of Shanghai, China

The significance of microplastics in urban air has gained increasing recognition; however, a comprehensive understanding of their size distribution and composition remains limited. This study presents analyzed results of micro-/nanoplastics collected from Shanghai's winter atmosphere using thermal desorption/pyrolysis-gas chromatography-mass spectrometry. Six major plastic types were identified, with polyethylene (PE) accounting for 40.0% of the detected atmospheric plastics. Fine plastic particles (FPPs, ≤3.2 μm) constituted 59.2% of the total mass concentration of microplastics (MPs), while nanoplastics (NPs, ≤1.0 μm) accounted for 36.3%. As the aerodynamic particle size decreased, the proportion of plastics other than PE increased. This size-dependent compositional variation suggests that nanoplastics, due to their smaller size, can more easily penetrate sensitive biological regions. At the nanoscale, the accumulated mass in pulmonary regions exceeds that in the head airway. These findings underscore the critical need for detailed assessments of plastic characteristics in the atmosphere to better understand their environmental behavior and potential health impacts.