Plastic burning: An important global source of atmospheric nanoplastic particles

Small nano-sized plastic particles can enter the atmosphere and be transported globally from source areas to remote regions. In contrast to secondary nanoplastic emissions, plastic materials exposed to high temperatures can emit large amounts of nanoplastics directly into the atmosphere. However, very little is known about emission rates and physical and chemical characteristics of these particles. In this work, we conducted laboratory smoldering experiments to simulate smoldering emissions of PVC, PP, LDPE, PET and PS. We measured the chemical composition using aerosol mass spectrometry show that both polymeric materials (characteristic of nanoplastics) and thermo-oxidation products are emitted in submicron particles. Based on the emission factors measured, we estimate that plastic waste burning and building fires can contribute roughly 0.5–5 megatons per year of nanoplastics, which exceeds emissions from oceans, and comparable to tire wear.The chemical fate of these particles was also examined by exposing the particles to atmospheric oxidants. We observe that these particles can age at appreciable rates under simulated oxidation conditions, on the order of days to weeks. These rates are similar to that of organic aerosol. This extent of oxidation in the atmosphere has strong implications on their hygroscopicity and their atmospheric fate, suggesting extensive oxidation prior to their deposition. Our laboratory studies provide mechanistic understanding for modeling atmospheric processes of nanoplastic particles and quantitative information for estimating atmospheric burden from plastic burning.