The Estimation of the Particle Size of Respirable Crystalline Silica (PSDRCS) from the Particle Size Distribution Measurement of Archived Dust Samples (PSDDUST)

Abstract

The study aimed to investigate the performance of an affordable, high-throughput method, i.e. Laser Light Scattering (LLS) to estimate the particle size of respirable crystalline silica (RCS) in archived dust samples, by comparing the results obtained by LLS with the results from a Scanning Electron Microscopy (SEM), the gold standard, an expensive, labour-intensive method. The length and width of approximately 100 RCS particles were measured using SEM (SEMRCS) in 12 respirable dust samples from NIST, Arizona dust and gold mine dust. The remainder of the dust sample was used to measure the particle size distribution (PSD) of all the dust particles using LLS (LLSDust). Linear regression models were derived for SEMRCS and LLSDust pairs, i.e., volume, length and area, and these regression models were used to estimate the SEMRCS from the LLSDust. The estimated SEMRCS was compared with the measured SEMRCS, and it was found that LLSDust is not a good predictor of SEMRCS and future research is needed to explore whether a more robust prediction model can be developed. In this study it was found that improvements on the SEMRCS methodology can be made to make the measurements more efficient and affordable. Hence, since a better estimate of the PSD of RCS will improve both the risk assessment and measures to control RCS in workplaces, it is recommended that direct SEM measurements of the RCS particle size are routinely incorporated.