Size-resolved identification and quantification of micro/nano-plastics in indoor air using pyrolysis gas chromatography-ion mobility mass spectrometry

Humans are exposed to differing levels of micro-/nanoplastics (MNPs) through inhalation, but few studies have attempted to measure <1 µm MNPs in air, in part due to a paucity of analytical methods. We developed an approach to identify and quantify MNPs in indoor air using a novel pyrolysis gas chromatographic cyclic ion mobility mass spectrometer (pyr-GCxcIMS). Four common plastic types were targeted for identification, namely (polystyrene (PS), polyethylene (PE), polypropylene (PP), and polymethyl methacrylate (PMMA). The method was applied to size-resolved particulate (56 nm-18µm) collected from two different indoor environments using a Micro-Orifice Uniform Deposit Impactors (MOUDI) model 110 cascade impactor. Comprehensive two-dimensional separation by GCxcIMS also enabled the retrospective analysis of other polymers and plastic additives. The mean concentrations of MNP particles with diameters <10 µm and <2.5 µm in the laboratory were 47 ± 5 and 27 ± 4 µg/m3 respectively. In the private residence, the concentrations were 24 ± 3 and 16 ± 2 µg/m3. PS was the most abundant MNP type in both locations. Approximately 57-67% of MNPs were characterized by particle diameters <2.5 µm, and 50-60% of the total particulate matter in the private residence was plastic. Non-targeted screening revealed the presence of plastic additives, such as TDCPP (Tris(1,3-dichloro-2-propyl)phosphate) whose abundance correlated with that of polyurethane (PU). This is consistent with their use as flame retardants in PU-based upholstered furniture and building insulation. This study provides evidence of exposure to MNPs which constitute over half of PM2.5 indoors and underlines the need for further study of this route of exposure to MNPs and the plastics additives carried with them.