Comparative assessment of five analytical methods for airborne microplastics highlights importance of identifying sub-$$10~\upmu \hbox {m}$$ methods

Microplastics are an emerging class of contaminants that are widespread in the environment. While studies on airborne microplastics are rapidly increasing, the lack of standardised sampling and analysis methods is hindering progress towards accurately quantifying their global distribution. This study used existing analytical methodologies to understand the variability in identifying and quantifying airborne microplastics. High-volume aerosol samples were collected at a remote site in New Zealand and were analysed by micro-Fourier transform infrared spectroscopy, micro-Raman spectroscopy, Nile red staining combined with fluorescence microscopy, pyrolysis-gas chromatography/mass spectrometry and thermal desorption-proton transfer reaction-mass spectrometry, with all methods reporting different concentrations and polymer types. No particles were larger than 100 µm, and 98% of particles were smaller than 10 µm, highlighting the importance of methods that can analyse sub-10 µm particles. This study highlights the need for caution when comparing airborne microplastic datasets analysed using different methods.