The inhalation of toxic substances is a major threat to the health of miners, and dust containing respirable crystalline
silica (α-
quartz) is of particular concern, due to the recent rise in cases of
coal workers' pneumoconiosis and
silicosis in some U.S. mining regions. Currently, there is no field-portable instrument that can measure airborne α-
quartz and give miners timely feedback on their exposure. The U.S. National Institute for Occupational Safety and Health (NIOSH) is therefore conducting studies to investigate technologies capable of end-of-shift or real-time measurement of airborne
quartz. The present study focuses on the potential application of Fourier transform infrared (FT-IR) spectrometry conducted in the diffuse reflection (DR) mode as a technique for measuring α-
quartz in respirable mine dust. A DR accessory was used to analyze lab-generated respirable samples of Min-U-Sil 5 (which contains more than 90% α-
quartz) and
coal dust, at mass loadings in the ranges of 100-600 μg and 600-5300 μg, respectively. The dust samples were deposited onto three different types of filters, borosilicate fiberglass,
nylon, and
polyvinyl chloride (
PVC). The reflectance, R, was calculated by the ratio of a blank filter and a filter with deposited mine dust. Results suggest that for
coal and pure
quartz dusts deposited on 37 mm
PVC filters, measurements of -log R correlate linearly with known amounts of
quartz on filters, with R(2) values of approximately 0.99 and 0.94, respectively, for samples loaded up to ∼4000 μg. Additional tests were conducted to measure
quartz in
coal dusts deposited onto the borosilicate fiberglass and
nylon filter media used in the NIOSH-developed Personal Dust Monitor (PDM). The
nylon filter was shown to be amenable to DR analysis, but quantification of
quartz is more accurate when the filter is "free," as opposed to being mounted in the PDM filter holder. The borosilicate fiberglass filters were shown to produce excessive interference, making
quartz quantification impossible. It was concluded that, while the DR/FT-IR method is potentially useful for on-filter measurement of
quartz in dust samples, the use of
PVC filters produced the most accurate results.