A thermogravimetric analysis application to determine coal, carbonate, and non-carbonate minerals mass fractions in respirable mine dust

Abstract

Occupational lung diseases such as coal worker’s pneumoconiosis, often called black lung, are caused by exposures to respirable coal mine dust. Dust composition is increasingly understood as an important disease factor, and it can vary significantly depending on dust source materials and generation processes. For regulatory compliance purposes, the mass concentration and quartz percentage of respirable dust are monitored in U.S. coal mines, but the whole composition is not typically determined. Previous work has indicated that thermogravimetric analysis (TGA) can be used to apportion the respirable dust mass to three important component fractions (i.e., coal, non-carbonate minerals, and carbonate), which should generally correlate with three different dust sources (i.e., coal strata, rock strata, and limestone rock dusting products being applied in the mine). However, a primary shortcoming of that previous work was use of fibrous sampling filters, which limited dust recovery and thus analytical accuracy. Here, an improved TGA application is presented using smooth polycarbonate filters. Based on experiments with laboratory-generated dust samples (masses ranging between 95–1,319 µg), the TGA-derived mass fractions (reported as percentage values) for all three components were found to generally be within ±10% of expected values.

Keywords:

• Black lung
• coal worker’s pneumoconiosis
• dust characterization
• rock dust

Acknowledgments

Thanks to Meredith Scaggs-Witte and Kent Phillips for contributions toward TGA method development, and Alex Norris, Bethany Witter, and Sarah Price for assistance in the laboratory. Views represented here are those of the authors and do not necessarily represent those the funding source or research partners.

Funding

The authors would like to thank the Alpha Foundation for the Improvement of Mine Safety and Health for funding this work, and industry partners that provided bulk dust source materials used here.