The MIA sought to look into these safety concerns due to the U.S. Environmental Protection Agency (EPA) presenting an abstract that included some exploratory research pertaining to certain occupational exposure scenarios related to granite, namely quarry workers and fabricators. "When we learned that the EPA would be looking into these issues and that there was a lack of reliable information on the topic, the MIA decided to take a leadership role and facilitate the necessary studies to confirm employee safety," said MIA Executive Vice President and CEO, Jim Hieb.
Key findings from the Radiation Dose of Workers During Fabrication of Granite study are as follows:
- Radiation doses due to fabrication of granite are very low, and well below both occupational standards (5,000 mrem/year) and limits to the general public (100 mrem/year).
- Workers exposed to granite dust concentrations at the Occupational Safety and Health Administration (OSHA) respirable dust permissible exposure limit (PEL) of five milligram per cubic meter (mg/m³) had an estimated radiation dose of only 8.7 mrem/year, even assuming they spent their entire 2,000-hour work year only working with granite, and were exposed to dust at the OSHA limit the entire time.
- Workers exposed to respirable granite dust concentrations at the OSHA silica PEL would have an expected radiation dose of only 1.4 mrem/year, again with very conservative (i.e., health-protective) assumptions (2,000-hour work year only working with granite stone and at the OSHA silica limit).
- Key findings from the Radon Exposures in a Granite Quarry study are as follows:
- According to the Mine Safety and Health Administration (MSHA), all active granite quarries in the U.S. are considered to be surface mines, and therefore are naturally ventilated. MSHA reported that there were only 330 workers in dimension granite quarries.
- Air monitoring conducted as part of this study found that the radon concentrations measured at varying heights in a deep quarry in Vermont, selected to represent a "worst-case" scenario because of the depth and high natural background radon, were all less than 0.3 picocuries per liter (pCi/L). This observed value is less than the average background radon concentration in the U.S.
- If a temperature inversion occurs, it typically occurs at night during times when workers are not normally present in the quarry. Therefore, inversions would have little or no impact on workers' annual average exposure to radon.
- Occupational exposure to radon for granite quarry workers is insignificant, even when considering the potential for temperature inversions.
The research was funded through generous contributions by MIA members to the Truth About Granite Fund. Additional contributions were made by the Building Stone Institute, Elberton Granite Association, Indiana Limestone Institute, the National Tile Contractor's Association, the Mason Contractors Association of America and the National Building Granite Quarriers Association.
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