PURPOSE:  Reduce worker exposure to respirable silica dust in metal/nonmetal operations by developing improved control technologies.

RESEARCH SUMMARY:  Chronic overexposure to respirable crystalline silica can lead to the progressive lung disease known as silicosis, which can be disabling or fatal. Data in the Mine Safety and Health Administration’s (MSHA) compliance sampling database indicates that a significant percentage of both underground and surface metal/nonmetal miners are overexposed to respirable silica dust each year. For samples collected from 2001 through 2004, 12% of all samples exceeded the permissible exposure limit (PEL), with numerous high-risk occupations having over 20% of their samples exceeding the PEL. This research program will conduct field surveys to identify dust sources for these high risk occupations, develop control technologies through laboratory and/or field studies, and transfer successful technologies to stakeholders.

To date, research has been conducted to: 1) develop optimized pressurization and filtration systems for enclosed cabs on mobile mining equipment and associated implementation guidelines, 2) develop a cost-effective method for cleaning work clothes in an enclosed booth and associated instructional video, 3) evaluate existing dust controls and develop improved ventilation controls for iron ore processing plants, and 4) demonstrate the effectiveness of improved mine-wide and localized ventilation systems in limestone mines for diluting dust and reducing residence time.

Future research will address: 1) the development and testing of control technologies to reduce worker exposure to silica dust in dimension stone shops, 2) the development of a stand-alone, clothes cleaning booth, which will increase its application in the industry 3) the benchmarking of controls for the silica sand industry and preparation of a handbook through a cooperative effort with Industrial Minerals Association – North America, and 4) the identifying of major dust sources for mobile workers to develop controls to reduce these exposures.

Successful outcomes will be measured by the effectiveness of the control technologies to lower exposure to respirable silica dust and the willingness of industry to adopt these control technologies at their mines and processing plants. A measure of this success would be a 50% reduction in the silica compliance samples for high risk occupations that exceed the permissible exposure limits over a five year time period.