Improved Method for Analysis of Airborne Asbestos Fibers Using Phase Contrast Microscopy and FTIR Spectrometry

In recent years, some studies have tried to improve Phase Contrast Microscopy (PCM) for counting asbestos fibers. Due to the lack of a universally accepted alternative method, this study aimed to improve PCM for better counting of asbestos fibers. Confirmed asbestos standards were applied using a dust generator for sampling. Sampling from the dust generator was carried out according to the Occupational Safety and Health Administration (OSHA) ID-160 method and 95 samples with diverse densities were prepared to be counted using conventional and modern PCM. All samples were counted single blindly by a co-author of this study and the obtained data were analyzed by paired t-test, correlation coefficient and Bland-Altman analysis. Duplicate samples were prepared for qualitative analysis by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X ray. Asbestos densities on filters were in the range of less than 100 to 600 fibers/mm2. Statistically, significant differences were observed for the count density of the 95 samples counted by the two phase contrast microscopes (P<0.001). Nikon microscope demonstrated higher counts compared to conventional microscope and had a lower coefficient of variation. Samples were analyzed qualitatively using FT-IR and SEM, and the presence of asbestos fibers was confirmed. The improved PCM and FT-IR methods presented in this study demonstrated more precise and accurate determination of personal exposure to airborne asbestos fibers and subsequent risk assessment.