Plastic and rubber polymers in urban PM₁₀ by pyrolysis-gas chromatography-mass spectrometry

Microplastics, including tyre and road wear particles, have been detected in every environmental compartment in both urban and remote areas. However, their contribution to atmospheric particulate matter is still sparsely explored. These airborne micro- and nanosized particles are continuously inhaled and pose risks to the environment and public health. The objectives of this study were to develop and validate a thermoanalytical method for the quantification of microplastics in urban particulate matter. Aerosol particles smaller than 10 µm in aerodynamic diameter (PM₁₀) were sampled at the kerbside in Helsinki, Finland, during spring 2024. The samples were pretreated by homogenization and thermal desorption prior to chemical analysis by micro-furnace pyrolysis-gas chromatography-mass spectrometry. The developed method was validated in terms of selectivity, limits of quantification, linear range, trueness, precision, and measurement uncertainty. Instrument quantification levels were 8-270 ng. Expanded measurement uncertainties were 25-30% and 50-70% for the studied tyre wear rubbers and thermoplastics, respectively. Polyethylene, polyethylene terephthalate, polypropylene, polystyrene, and tyre and road wear particles were detected in urban PM₁₀ samples, and their sum accounts for 1-3% of total PM₁₀. These results represent the level of airborne microplastic particles to which people can be exposed in urban environments.