Thoracic Dust Exposures on Longwall and Continuous Mining Sections

Abstract

Past data on the prevalence of symptoms of chronic bronchitis and decreases in pulmonary function indicate a potential problem due to deposition of coal mine dust in the bronchial airways. Difficulty with dust control in certain jobs indicates that chronic bronchitis may continue to be a problem.

Compliance with the respirable dust standard does not equally limit the thoracic dust exposure of all miners. Coal mine dust size distributions indicate that thoracic dust levels may be as high as five times respirable dust levels in some work areas on continuous mining sections and seven times respirable dust levels in some work areas on longwall mining sections. The largest thoracic dust generating sources are the longwall shearer, shield support advancement, and the continuous miner. The worst case scenario for thoracic dust exposure occurs on bidirectional cutting longwall mining sections where some mine personnel are very likely to work downwind of the shearer and/or support advancement for a significant portion of the shift. Continuous miner operators who are not utilizing remote control and roof bolter operators working downwind of the continuous miner may also be exposed to relatively high concentrations of thoracic dust.

Future thoracic dust control techniques will differ from respirable dust control techniques by paying more attention to the > 5 μm particles present in the airstream.