Microplastics in Urban Ambient Air: A Rapid Review of Active Sampling and Analytical Methods for Human Risk Assessment
Inkyu Han, C.-C. Lee, Caesar Belchez, Andrea Goldstein Shipper, Kirsten E. Wiens
Abstract
This study conducted a rapid review to evaluate active air sampling and analytical methods for characterizing outdoor air microplastics in urban areas. We synthesized information from 35 peer-reviewed journal articles. Studies utilizing active sampling methods were able to provide detailed data on inhalation concentrations and doses. The analytical techniques reviewed were categorized into microscopy, Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, Scanning Electron Microscopy (SEM), and mass spectrometry, including Pyrolysis-Gas Chromatography (Py-GC). While conventional FTIR and Raman spectroscopy can identify microplastics in total suspended particles, advanced instruments such as μRaman and SEM are crucial for analyzing inhalable microplastics (e.g., particles smaller than 10 μm). Characterizing the shapes and colors of microplastics can provide qualitative estimates of their sources, with fibers and the color black being the most predominant. Establishing dose-response relationships for health effects requires quantitative analyses; thus, combining techniques like μRaman with Py-GC is essential for comprehensive human risk assessments. Future studies should focus on identifying and quantifying inhalable micro-plastic compounds that are relevant to human health.