Size Distribution, Chemical Composition, and Source Contributions of Underground Coal Mine Dust

XIAOLIANG WANG, Mohammadreza Elahifard, Bankole Osho, L.-W. Antony Chen, Judith Chow, John Watson, Behrooz Abbasi, Desert Research Institute

     Abstract Number: 327
     Working Group: Health-Related Aerosols

Abstract
Determination of size distributions, chemical compositions, and source contributions of respirable coal mine dust (RCMD) in mining environments is important for health effect assessment and dust control. This study collected source and ambient samples from an underground coal mine and conducted detailed chemical speciation. The effective-variance chemical mass balance (EV-CMB) model was used to apportion RCMD and respirable crystalline silica (RCS) contributions from coal dust, fire suppression limestone dust, rock strata particles, diesel engine exhaust, and intake air.

RCMD concentrations vary significantly within the mine with several locations exceeding the 1.5 mg/m3 permissible exposure limit. The mass size distributions are similar to those measured over a decade ago, with a mass median aerodynamic diameter of ~10 μm and most mass in the size range >1 μm. Among the three locations with the highest RCMD concentrations, limestone dust contributed ~80% to the RCMD mass in the tailgate and return air, while coal dust contributed 51% to the RCMD mass at the longwall face. Intake air dominated the RCMD mass at locations with low concentrations, indicating that these locations were effectively ventilated by intake air. Diesel exhaust is a minor contributor to RCMD mass at most locations. Limestone and rock strata are the main sources of RCS, supporting the concerns for more RCS generation due to the more powerful mining tools cutting more into rock strata.