Thermogravimetric analysis of respirable coal mine dust for simple source apportionment

Abstract

Resurgence of coal mine dust lung diseases in the central Appalachian region of the United States and elsewhere has spurred a range of efforts to better understand respirable coal mine dust (RCMD) exposures and sources. Thermogravimetric analysis (TGA) of RCMD samples can enable the dust mass to be fractionated into three main components: coal, non-carbonate minerals, and carbonates. These are expected to approximate, respectively, the three primary dust sources in many underground mines: the coal seam being mined, the surrounding rock strata (i.e., typically dominated by non-carbonate minerals) being drilled or mined along with the coal, and the rock dust products (i.e., typically made from carbonate-rich limestone or dolostone) being applied in the mine to mitigate explosibility hazards. As proof of concept, TGA was applied to respirable dust samples that were laboratory-generated from real source materials representing 15 mines. Except in the case of two mines, compositional results were generally consistent with expectations. TGA was also applied to RCMD samples collected in standard locations of 23 mines (including the 15 mines represented by the dust source materials). Results showed significantly different compositions with respect to sampling location and geographic region (i.e., within and outside of central Appalachia). To further interpret the RCMD results, a simple source apportionment model was built using the dust compositions yielded from the source materials analysis. Model results indicated that, on average, about twice as much dust was sourced from mining into rock strata than from mining the target coal seam. This finding is particularly important for mines extracting relatively large amounts of rock along with the coal or for mines that frequently encounter high-silica rock strata.

Keywords:

• Coal worker’s pneumoconiosis
• occupational health
• progressive massive fibrosis
• respirable dust

Acknowledgments

The authors gratefully knowledge the Alpha Foundation for Improvement of Mine Safety and Health and the National Institute for Occupational Safety and Health (CDC/NIOSH) for funding this work. We would like to thank our numerous industry partners for providing mine access and logistical support for dust sampling. We are also thankful to Alex Norris, Kyle Louk and Meredith Scaggs-Witte for their assistance with mine sampling, and Baxter Jones, Nishan Pokhrel, Sydnie Wilson, and Jonathan Gonzalez for their assistance with laboratory sample generation. The views expressed here are those of the authors and do not necessarily represent the views of research partners or sponsors.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.

Additional information

Funding

This work was supported by the Alpha Foundation for the Improvement of Mine Safety and Health; and the National Institute for Occupational Safety and Health (CDC/NIOSH).