Abstract
Since the early 1970s the Mine Safety and Health Administration has enforced health and safety standards in metal and nonmetal mines and mills. A major concern is exposure to respirable dusts containing quartz. More than 134,000 full-shift air samples have been collected since 1974 by inspectors to determine compliance. Of these samples, more than 82,000 contained at least 1 percent quartz. The objective of this article is to show the trends in this subset of the respirable dust data. However, exposure trends are affected by periodic procedural and policy changes and by the compliance sampling strategy; thus these data may not be representative of industry-wide exposures. Since 1988, 24 percent of nearly 23,000 respirable dust samples containing at least 1 percent quartz exceeded the permissible exposure limit. Statistical analysis by the U.S. Bureau of Mines has identified the commodities, locations, and occupations with the highest quartz exposures. Commodities with more than 50 percent of the samples exceeding the limit include underground silver and copper mines and mills producing nonmetallic minerals. Nonmetallic minerals include some mills producing highly siliceous and abrasive material, which is frequently bagged. Samples from these mills contain a high mean percentage of silica (43%), have a high geometric mean quartz concentration (107 μg/m3), and have a high percentage of samples exceeding the limit (56%). This information helps target operations requiring additional dust control technology to further reduce respirable quartz dust exposure. Watts, Jr., W.F.; Parker, D.R.: Quartz Exposure Trends in Metal and Nonmetal Mining. Appl. Occup. Environ. Hyg. 10(12):1009–1018; 1995.
