Mining Contract: Characterization of Coal Mine Dust Size Distribution, Chemical Composition, and Source Contributions

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

As recommended by a 2018 National Academies of Sciences, Engineering, and Medicine (NAS) report, a comprehensive assessment of respirable coal mine dust (RCMD) particle characteristics is needed because different particle characteristics (for example, composition and surface area) can pose different health hazards. This study will collect samples in various locations in-mine, characterize the size distribution, and determine the chemical composition of the samples. With known chemical compositions of source and ambient samples, receptor-based source apportionment models will be used to estimate contributions from major RCMD sources (e.g., dust from cutting, drilling, or crushing coal or rock strata; rock dust application; intake air; and diesel exhaust).

Mine safety regulations require monitoring of RCMD. RCMD is a size fraction of the dust that can be inhaled and transferred to the gas exchange region (alveolar) of the lung. Using instruments designed to collect dust, RCMD is measured after air passes through a cyclone inlet meant to approximate human inhalation. However, much of the data on coal mine dust size distributions was collected more than a decade ago, and it may not represent data for mines using modern technologies and practices (i.e., increased equipment size and power; higher production rates; mining thinner coal seams with high out-of-seam dilution rates; higher air velocities around mine workings). Studies show the RCMD sampling method is a crude approximation of the actual amount of particles that will deposit in the lung. For these reasons, the NAS 2018 report recommended that size distributions of coal mine dust in modern mines should be quantified.

Although current mining regulations only require monitoring for RCMD mass and crystalline silica, other properties, such as size, morphology, and chemical composition also affect health outcomes. RCMD and silica concentrations have decreased in all mining regions since 1969 when the Federal Coal Mine Health and Safety Act was passed. However, studies show that since about 2000, there has been an increase in the prevalence and severity of coal mine dust-related lung diseases in some U.S. mining regions, suggesting health influences other than mass and silica, possibly related to particle size and specific chemical constituents.

The University of Nevada, Reno, research team has extensive past experience in projects related to mine dust characterization and control specifically in Illinois, Indiana, Western Kentucky, western mines (Utah and Wyoming), and Alberta, Canada.

This contract research will advance knowledge in areas related to several recommendations of the NAS report. Specifically, the team will undertake the following:

• Characterize coal mine dust size distribution, chemical composition, and source and health risk contributions around mining areas (e.g., face, haulage units, roof bolters, coal transfer points) where workers are subject to long-term dust exposure (Recommendations 4 and 8).
• Determine exposure level of workers to RCMD, with a focus on miners wearing and not wearing a continuous personal dust monitor (CPDM) in the targeted areas (Recommendation 2).
• Explore the potential of improving crystalline silica quantification sensitivity with portable Raman spectrometry (Recommendation 5).