Widespread distribution of PET and PC microplastics in dust in urban China and their estimated human exposure

Dust is a fate of many contaminants and may be an important medium for the human exposure to these contaminants. Microplastics (MPs) have been observed in dust in previous studies. However, the mass concentrations of dominant MPs in dust and the exposure risk to human remain unclear. In this study, indoor and outdoor dust samples were collected from 39 major cities of China. The mass concentrations of polyethylene terephthalate (PET) and polycarbonate (PC) MPs were determined through alkali-assisted thermal depolymerization-liquid chromatography-tandem mass spectrometry, and the shape and component distribution of MPs were analyzed by optical microscopy and micro-Fourier transform infrared spectroscopy. PET MPs were detected in all the samples at high concentrations of 1550-120,000 mg/kg (indoor) and 212-9020 mg/kg (outdoor) and PC MPs were detected in approximately 70% of the samples, with median concentrations of 4.6 mg/kg (indoor) and 2.0 mg/kg (outdoor). Fiber was the main shape of suspected MPs, and polyester (including PET) was identified as an important component in MPs from dust. Indoor dust is a non-negligible source of human exposure to MPs, accounting for a geomean daily intake of 17,300 ng/kg-bw of PET MPs in children.