Aerosols Generated in the Wastewater Treatment Process Are a Potential Source of Airborne Microplastics

Airborne microplastics pose a significant risk to human health. Similarly to the water-air transfer process, such as sea spray, aerosols generated during the wastewater treatment process, driven by aeration and mechanical agitation, are an overlooked potential source of airborne microplastics. This study constitutes the first attempt to investigate the pollution characteristics of microplastics in aerosols generated during wastewater treatment, based on laser direct infrared spectroscopy (LDIR) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Microplastics were ubiquitously observed in aerosols from each unit of the wastewater treatment plant, with abundances in the range of 0.83-28.03 items·m^-3. A total of 30 different polymer types were identified by LDIR, while polyvinyl chloride and polyethylene terephthalate were the most common polymers. Film and fragment were the main shapes, with a predominant size range of 20-50 μm. The aerosolization degree of microplastics is affected by the aeration intensities and hydrodynamic conditions maintained in each unit, but also varied depending on their inherent characteristics. These findings suggest that the aerosolization of microplastics from wastewater treatment is a potential source of airborne microplastics. This study contributes a novel insight into the occurrence of microplastics in aerosols generated during wastewater treatment.