In 1987 the International Agency for Research on Cancer reviewed the health literature and concluded that crystalline silica (quartz, cristobalite, and tridymite) was a probable human carcinogen. As a result, the Occupational Safety and Health Administration (OSHA) was required to regulate crystalline silica under its hazard communication standard (hcs). Mine Safety and Health Administration (MSHA) will probably promulgate similar regulations. All materials that contain 0.1 pct or more crystalline silica must be labeled according to hcs and workers who handle them must receive training. The permissible exposure level is 50 micrograms for an 8-h day. This report addresses two major concerns with the hcs: (1) the widespread occurrence of crystalline silica in common ores and commodities, and (2) the suitability of current technology for routinely determining crystalline silica at the 0.1 pct level. Osha's hcs will have greatest impact on producers of crushed stone, diatomite, dimension stone, gravel, industrial sand, perlite, pumice, pyrophyllite, sand, and talc because these materials are frequently shipped directly from the mill to the customer. MSHA's hcs will affect nearly all mineral producers. Crystalline silica can be quantified at the 0.1 pct level by x-ray diffractometry in simple systems if (1) none of the accessory minerals has x-ray diffraction reflections that coincide or overlap those of crystalline silica, and (2) the standard has a particle size distribution and crystallinity similar to those of the sample.
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