OSHA has proposed to reduce the occupational healthexposure to crystalline silica dust due to the evidence of risk of lung cancer, silicosis, chronic obstructive pulmonary disease, and kidney disease.
The current OSHA permissible exposure limit (PEL) is based on a formula based on the percent of crystalline silica in sets of bulk samples rather than the percent crystalline silica in each individual air sample. OSHA and MSHA collected and reviewed occupational health data of crystalline silica dust exposures (1974–1994) by inspecting various manufacture, construction, and maritime industries. The data showed elevated occupational exposures above equivalent permissible exposure limits of 100 micrograms/m3 (µg/m3) for general industry and a 250 µg/m3 for an 8-hour time weighted average (TWA).