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

Contract # 75D30119C05759
Start Date 9/1/2019
Research Concept

As recommended by the 2018 National Academies of Sciences, Engineering, and Medicine 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).

Contract Status & Impact

This contract is ongoing. For more information on this contract, send a request to mining@cdc.gov.

Inhalation of coal mine dust is known to be associated with coal workers' pneumoconiosis (black lung disease) and silicosis in underground coal miners. There is a direct relationship between respirable coal mine dust (RCMD) exposure and risks of lung cellular damage and inflammation. When inhaled, dust particles can deposit in different regions of the respiratory tract depending on their size and shape.

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. Much of the data on coal mine dust size distributions was collected more than a decade ago, and may not represent data for mines using modern technologies and practices (e.g., 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 National Academies of Sciences, Engineering, and Medicine 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 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.

As a result, the NAS recommended research to provide a better understanding of the RCMD particle composition. The research under this contract will help provide that understanding through a comprehensive characterization of RCMD chemical compositions and size distributions.

Additionally, the NAS recommended an assessment to characterize and quantify important source contributions to airborne RCMD, including rock dusting and extraction of rock strata adjacent to the mined coal seam. Using the known chemical compositions of source and ambient samples obtained from the particle characterization effort, the contractor will use receptor-based source apportionment models 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).

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 project will advance knowledge in areas related to Recommendations 2, 4, 5, 8 and 9 of the NAS report. Specifically, the team will:

  • 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 (Recommendation 4 & 8)
  • determine exposure level of workers to respirable coal mine dust (RCMD), with focus on miners wearing and not wearing 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)

Page last reviewed: 2/4/2020 Page last updated: 2/4/2020