The evaluation and quantification of respirable coal and silica dust concentrations : a task–based approach

Abstract

Silicosis and coal worker's pneumoconiosis are serious occupational respiratory diseases associated with the coal mining industry and the inhalation of respirable dusts that contain crystalline silica. Silica exposure is an occupational health priority even when exposure has ceased or is below the occupational exposure limit (0.1 mg/m3). The objective of this study was to determine the individual contributions of the underground coal mining tasks to the total amount of respirable dust and respirable silica dust concentrations found in this environment. The tasks that were identified were continuous miner (CM) cutting, construction, the transfer point, tipping and roof bolting. Respirable dust sampling was conducted at the intake and return of each task, as well as at the intake and return of the section and the intake airway to the section. The five occupations that perform these tasks were also sampled to determine the personal exposure levels. Respirable dust concentrations and small concentrations of respirable silica dust were found in the intake airway and intake of the section, indicating that the air that enters the section is already contaminated. The respirable dust-generating hierarchy of the individual tasks was: transfer point>CM right cutting> CM left cutting> CM face cutting> construction> roof bolting > tipping. For respirable silica dust the hierarchy was: CM left cutting> construction> transfer point> CM right cutting. CM face cutting, tipping and roof bolting generated concentrations of below quantifiable levels. The personal exposures also differed and the eM and stamler operators had the highest exposure to respirable dust (3.417 ± 0.862 mg/m3) and respirable silica dust (0.179 ± 0.388 mg/m3) concentrations, respectively. Recommendations have been included for lowering the respirable dust and silica dust concentrations that are generated and that the workers are exposed to underground.