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Mining Project: Reducing Silica and Other Respirable Dust Exposures in the Metal/Nonmetal Mining Industry

Project DetailValue
Principal Investigators
  • Andrew B. Cecala, NIOSH, 412-386-6677
Start Date10/1/2010

The purpose of this project is to develop and evaluate control technology to reduce metal/nonmetal mine worker’s exposure to silica and other respirable dust and contaminants in metal/nonmetal mines and mills, including surface and underground operations.

Program Area
Keywordsairborne contaminants, mining, silica

Research Summary

Inhalation of excessive levels of silica dust can lead to the development of silicosis, a debilitating and potentially fatal lung disease. The metal/nonmetal mining industry currently employs approximately 160,000 workers across four sectors in surface, milling, and underground operations. The adverse health effects of breathing respirable silica dust potentially affects 70,800 workers in stone operations, 37,600 in sand and gravel operations, 30,000 in metal operations, and 22,000 in nonmetal mining operations. The Mine Safety and Health Administration (MSHA) dust sampling results indicate that overexposure to respirable silica dust continues to occur at high rates for select occupations in both underground and surface mining operations. This research effort needs to be performed because of the serious health hazards associated with silica dust inhalation. 

A factor that may significantly impact the metal/nonmetal mining industry is a proposal to reduce the current respirable silica dust standard by 50% from a 100 to a 50 microgram level. If the dust standard was reduced, it would significantly increase the number of workers whose dust levels would be exceeding the reduced standard. Although the primary focus of this project is reducing worker’s exposure to crystalline silica dust in the metal/nonmetal mining industry, this effort also includes all other types of respirable dust encountered in these operations. Meeting the silica dust standard through the development of new control technologies remains a primary objective of the mining industry.

A major cooperative effort with the Industrial Minerals Association – North America (IMA-NA) to develop a dust control handbook for mineral processing operations was completed in 2011. This handbook will be viewed as the “How To” document to lower dust levels in these types of operations throughout the world.

One of the first tasks to be performed will be the completion of the Helmet CAM, which involves a worker wearing a camera on his/her hardhat to obtain constant footage of the various tasks the worker is performing, relative to time. The individual will also be wearing an instantaneous dust monitor operating in the active sampling mode, which will deposit the respirable dust onto a dust filter. The video footage and dust data will be merged together to determine where mobile workers (bullgang laborers) are receiving their high dust exposures. Engineering controls will be developed and tested to lower the dust exposures to this job function. 

Another project task will be examining the dust exposure from bagging operations. Another project task will be performed to lower the dust exposures to crusher operators at both surface and underground locations. The most effective method to achieve this goal would be to place the worker in a booth supplied with clean filtered air. Two areas that will be addressed at mineral processing operations are reducing dust generated from conveyor belts and from screens. One additional task to be performed is to lower worker’s exposure to silica and other respirable dust during stone cutting and polishing.  Engineering control techniques will be developed, implemented, and tested to control the dust generated from the major dust sources at these stone operations. This task should be completed during the fourth year of this project.


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