Mining Project: Reducing Silica and other Respirable Hazards in the Industrial Minerals and Metal/Nonmetal Mining Industries

Principal Investigators
Start Date 10/1/2014

To develop control interventions to reduce occupational exposure to silica and other respirable dusts in metal/nonmetal mines and mills.

Topic Areas

Research Summary

Occupational exposures to respirable crystalline silica are associated with the development of silicosis, lung cancer, pulmonary tuberculosis, and airway diseases such as chronic obstructive pulmonary disease, which includes chronic bronchitis and emphysema. MSHA’s compliance 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, including mobile workers, bagging operators, and stone polishers.

While the MSHA standard is unchanged at 100 µm/m3,  the Occupational Safety and Health Administration (OSHA) issued a final rule, which took effect on June 23, 2016, containing two standards on respirable crystalline silica that, among other things, lowered the permissible exposure limit (PEL) from 100 to 50 µm/m3 as an 8-hour time-weighted average concentration in the construction, maritime, and general industry sectors.  The final rule is being fully implemented over a period of five years and portions of it are already active in certain industry sectors.

This project has five research aims, as follows:

  1. Optimize pressurization/filtration systems for control rooms and operator compartments to reduce silica exposures to miners working in these types of enclosures.
  2. Use Helmet-CAM assessment technology on mobile workers to identify high respirable dust exposure job duties and tasks, then develop engineering controls and behavioral interventions to reduce these exposures.
  3. Identify, evaluate, and improve the effectiveness of engineering control technologies and interventions currently being used to reduce respirable dust levels at bagging operations.
  4. Determine effective control techniques and interventions to reduce silica exposures of miners while performing the thermalling process in dimensional stone operations.
  5. Determine a simplified and accurate correction tool for various light-scattering nephelometers/instruments to more closely represent compliance dust sampling in the metal/nonmetal industry using Helmet-CAM technology.

This project will develop, implement, and evaluate engineering controls to minimize respirable dust exposures at targeted job classifications. In order to develop feasible and successful engineering control technologies, NIOSH will perform the following tasks: (1) Conceptualize, design, and fabricate dust control systems; (2) When appropriate, laboratory test the dust control systems at NIOSH laboratory facilities over a wide range of representative operating controls and parameters that closely represent real mining conditions; (3) Take the optimized laboratory design into the field to perform real-world evaluations of these interventions.

NIOSH's strong working relationship with metal/nonmetal mining industrial associations, as well as with individual companies, has helped solve other mineral industry dust problems in the past and has led to wide-scale industry adoption of developed technologies. Successful completion of this research as well as adoption of the developed engineering controls by industry will lower dust levels at occupations with high rates of overexposures. This will in turn reduce the incidence of silicosis and other respirable diseases in the metal/nonmetal mining industry.

Related Handbooks

Dust Control Handbook for Industrial Minerals and Processing

Design, Testing, and Modeling of Environmental Enclosures for Controlling Worker Exposure to Airborne Contaminants

Best Practices for Dust Control in Metal/Nonmetal Mining

Analysis of the Silica Percent in Airborne Respirable Mine Dust Samples from U.S. Operations

Key Design Factors of Enclosed Cab Dust Filtration Systems

Related Journal Articles

Reducing Float Coal Dust: Field Evaluation of an Inline Auxiliary Fan Scrubber

Control of Respirable Dust

Improving Silica Dust Controls for Metal/Nonmetal Mining Operations in the United States

Silica Dust Sources in Underground Metal/Nonmetal Mines - Two Case Studies

Air Cleaning Performance of a New Environmentally Controlled Primary Crusher Operator Booth

Assessing Noise and Dust

Related Project Research

Particulate Measurement and Characterization in Mining

Ventilation to Control Contaminants in Metal/NonMetal Mining Operations

Related Workshop

Silica Dust Control for Metal/Nonmetal Mining

Page last reviewed: 3/6/2019 Page last updated: 3/6/2019