Hazard evaluation and technical assistance report: HETA 82-112-113-114-0000, Mine Safety and Health Administration, Morgantown, West Virginia.
Morgantown, WV: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, HETA 82-112-113-114-0000, 1983 Aug; :1-28
The National Institute for Occupational Safety and Health (NIOSH) received a technical assistance (TA) request from the Mine Safety and Health Administration (MSHA) to evaluate the respiratory status of highwall drill operators and drill helpers employed at five surface coal mines. This request was precipitated by the fact that one-half of the surface work positions on a reduced dust standard involved highwall drill operations, plus a previous NIOSH report had suggested an increased risk of pneumoconiosis for drill crew members. NIOSH responded to the request by conducting a respiratory health and environmental survey at the designated mines to assess the prevalence of silicosis in drill crew members and to determine if a more complete epidemiological study was indicated. Health screening consisted of a chest radiograph, spirometry and a medical questionnaire detailing occupational history. Of the 185 drillers and 166 nondrillers selected for examination, 148 drillers and 108 nondrillers participated in the study. After review of work histories, a substantial portion (41% for drillers, 21% for nondrillers) were excluded from the analysis due to past exposures in underground mining, welding, etc. A total of 88 drillers and 85 nondrillers were included in the analysis of medical data. Analysis of pulmonary function data using multiple regression techniques indicated no significant differences in values of FEV1 or peak flow between the groups of drillers and nondrillers. The difference for FVC was borderline significant (p = 0.058). Chest radiography indicated six cases of simple pneumoconiosis. Two cases were found in the total analyzed group of workers. One was a former driller helper (1 year tenure) currently employed as an electrician. The other was a mechanic (24 years tenure) with no other work experience. The four additional cases were found in the group excluded from analysis due to past exposures. Three of these had several years (14-19) of underground experience. Environmental measurements obtained at the selected mines indicated a geometric mean exposure for respirable dust of 0.49 mg/m3 . Sixty-eight percent of the personal respirable samples had quartz concentrations greater than 5 percent. The overall geometric mean percentage of quartz by weight was 12.9%. Worker exposure to respirable dust containing quartz exceeded the MSHA Threshold Limit Value (TLV) in 36.5% of the measurements. The NIOSH recommended standard (0.05 mg/m3 ) for exposure to respirable free silica was exceeded in 68% of all measurements taken. The environmental measurements indicated that the engineering controls employed on the drilling equipment at one mine reduced the dust concentrations by 70% at the operator's station, and that a large percentage (40-45%) of the dust measured at the operator's station in all three mines is in the respirable range (10 microns and less). No significant excess respiratory disease was found in this survey of currently employed surface coal mine highwall drill crews. However, in light of previous studies, the environmental data collected, and the NIOSH recommended standard for exposure to respirable free silica, it is likely that such risk is present in some situations. Therefore, NIOSH recommends further epidemiological study to effectively evaluate the respiratory status of current and former highwall drill crews throughout the industry.
Mining-industry; Surface-mining; Silica-dusts; Exposure-assessment; Risk-analysis; Respiratory-system-disorders; Pulmonary-system-disorders; Humans; Statistical-analysis; Coal-mining;
Author Keywords: Drilling; Silica; Quartz
Field Studies; Hazard Evaluation and Technical Assistance
National Institute for Occupational Safety and Health