Source and potential risk assessment of suspended atmospheric microplastics in Shanghai

A growing body of research has recently revealed that airborne microplastics could be an important source of microplastic pollution in marine environments. However, the origins and spatial distributions of suspended atmospheric microplastics (SAMPs) are poorly understood. Further, SAMPs abundances have only been observed using passive sampling devices that could lead to underestimates of abundances. To address these knowledge-gaps, the current study investigated the potential source and spatial distribution of SAMPs in Shanghai during May 2018 using an active suspended particulate sampler. SAMPs abundances from filtered air ranged from 0 to 4.18 n/m3 (items per cubic meter of air). Microfibers comprised 67% of all SAMPs, followed by fragments and granules comprising 30% and 3% of SAMPs, respectively. μ-FT-IR analysis revealed that the SAMPs consisted of polyethylene terephthalate (PET), polyethylene (PE), polyester (PES), polyacrylonitrile (PAN), poly(N-methyl acrylamide) (PAA), rayon (RY), ethylene vinyl acetate (EVA), epoxy resin (EP), and alkyd resin (ALK). Synthetic compounds comprised 54% of the observed particles, of which PET, PE, PES, PAN, PAA, and RY comprised 91% of the microplastics. Our preliminary evaluation indicated that textile clothes are likely major source of the airborne microplastics. Modeling estimated that approximately 120.7 kg of SAMPs are annually transported through Shanghai air. Moreover, an estimation of the ecological risk from SAMPs indicated that a minor ecological consequence was present, necessitating further evaluation of SAMPs pollution. In addition, modeling estimated that approximately 21 particles of microplastics are inhaled daily by people in Shanghai from outdoor environments. Given the prevalence of airborne microfibers, it is critically urgent to reevaluate procedures for sampling, transporting, and processing microplastic field samples. Future investigations should seek to develop more rigorous and conclusive methods to evaluate these types of samples.