Nanoplastic Particle Emissions from Plastic Smoldering Combustion

Atmospheric nanoplastic particles (NPPs) are an emerging environmental concern due to their potential adverse effects on human and ecosystem health. Many recently identified sources involve subjecting plastic materials to elevated temperatures; however, fundamental understanding of airborne emissions is limited. This study is the first systematic characterization of particle and volatile organic compound emissions from plastic smoldering combustion. Five common plastic types were studied, including low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). For all types of plastics, a dominant submicron mode of emitted particles is observed. The composition of NPPs and oxidation products is identified in aerosol mass spectra, where mass fractions of NPPs are estimated based on their distinctive fragment ions: hydrocarbon ions (LDPE and PP), aromatic ions (PS), phthalate ions (PET), and organochlorine and polycyclic aromatic hydrocarbons ions (PVC). Emission factors of submicron particles (0.5-769 g kg^-1) and VOCs (46-393 g kg^-1) are calculated. NPPs from open plastic combustion are estimated to exceed oceanic microplastic emissions and be comparable to microplastics from tire and brake wear. Open plastic combustion is suggested to be an important source of atmospheric NPPs and to play a central role in the global plastic cycle.