66 A New Raman Spectroscopy Approach for the Measurement of Respirable Crystalline Silica Aerosols Collected onto Filters: Practical Considerations and Advantages

Abstract It is estimated that 560,000 workers in the United Kingdom are potentially exposed to respirable crystalline silica (RCS), which can cause disabling diseases such as silicosis and cancer. The incidence of silicosis in exposed workers can occur at levels below current workplace exposure limits and sensitive analytical techniques are needed to measure low RCS concentrations. The analytical performance of a new Raman spectroscopy method was compared with current X-ray diffraction (XRD) methods. The study investigated limits of detection, measurement uncertainty and measured samples collected from inside respirators. In total, 119 respirable, thoracic, and samples from the Sioutas impactor (PM10 to PM2.5) were also collected from cutting and polishing of engineered and natural stones and analysed for RCS. The LOD for Raman of 0.26 µg is lower than those published for current XRD or infrared methods (5 to 10 µg). The coefficients of determination were between 0.97 and 0.94. The Raman response is as stable as XRD when measuring samples with different median particle sizes (from 0.5 to 7 µm). Raman measurements were significantly different at the 95 % confidence level for the respirable samples (slope = 1.11) but not for thoracic samples (slope = 1.03). Raman spectroscopy has an advantage when measuring quartz in the presence of some minerals that cause interferences with XRD such as zircon. Raman spectroscopy is a promising alternative to XRD for RCS measurements. It has a low LOD and few modifications of current protocols would be necessary to adopt a Raman analysis approach. 2022© Crown copyright