Size-Resolved Airborne Micro- and Nanoplastics in Beijing: Comparative Analysis of Heating and Non-Heating Seasons

Airborne micro- and nanoplastics (MNPs) are emerging pollutants of concern due to their widespread presence, inhalation exposure risks, and potential ecological and human health impacts. In this study, pyrolysis–thermal desorption–gas chromatography–mass spectrometry (Py-TD-GC-MS) was applied to quantify MNPs (PP, PE, PS, PVC, and PET) in PM 2.5, PM 10, and total suspended particulate matter (TSP) collected during the non-heating and heating seasons in Beijing. The average concentrations of MNPs in PM 2.5, PM 10, and TSP during the non-heating season were 0.21 ± 0.05 μg/m 3, 0.45 ± 0.20 μg/m 3, and 0.84 ± 0.42 μg/m 3, respectively, rising to 0.41 ± 0.12 μg/m 3, 1.23 ± 0.58 μg/m 3, and 2.30 ± 0.75 μg/m 3 during the heating season, with polyethylene (PE) dominating all size fractions (>50%). Complementary vibrational spectroscopy results confirmed the presence of additional polymers, including polyamide (PA) and poly(methyl methacrylate) (PMMA), highlighting the value of multimethod approaches for comprehensive characterization and the ongoing need to develop new analytical techniques. Exposure assessment indicated daily per capita inhalation of outdoor MNPs in urban Beijing at 60–344 ng during the non-heating season and 374–926 ng during the heating season. This study provides the first size-resolved, multimethod assessment of airborne MNPs in a northern Chinese megacity, with a comparative analysis between heating and non-heating seasons.