Mining Program Area: Respirable Dust Assessment and Control
Inhalation of respirable-sized coal or silica dust in mining operations can lead to coal workers' pneumoconiosis (CWP) or silicosis, respectively. These are chronic, debilitating lung diseases that can be fatal in their most severe forms. Health surveillance studies of underground and surface mine workers show that CWP and silicosis continue to be a significant health threat in the mining industry.
The goal of this research program is to eliminate CWP and silicosis from the mining industry. This can be achieved through the development and implementation of control technologies that effectively limit mine worker exposure to airborne respirable dust. Dust control research for the mining industry was initially conducted by researchers in the U.S. Bureau of Mines until this responsibility and expertise was transferred into NIOSH in the Office of Mine Safety and Health Research (OMSHR). The Bureau research identified many dust control technologies that have been adopted by industry as the foundation of their dust control efforts. OMSHR dust control research continues to build upon these dust control capabilities for mining operations to address changes in mining equipment and practices, including production increases. In addition, the development of improved real-time or near real-time aerosol monitoring equipment can help reduce worker exposures to hazardous airborne particulate by identifying elevated dust exposures thus allowing for immediate corrective actions to be implemented.
Compliance dust sampling data obtained from the Mine Safety and Health Administration (MSHA) is periodically analyzed to identify the mining occupations that have the highest rates of overexposure to airborne respirable dust. Once identified, OMSHR conducts research to quantify the sources of dust exposures for these occupations and then works to develop control technologies that reduce exposures. Also, OMSHR is conducting research to develop instrumentation for mine workers and/or MSHA to more quickly analyze samples for silica content in order to reduce silica dust exposures in coal and metal/nonmetal mining operations.
OMSHR has unique, full-scale dust galleries that allow for extensive scientific testing of control technologies under controlled conditions, which would be impossible in actual mining operations. After identifying control technologies with promise and optimizing their performance through laboratory testing, these controls are typically tested in active mining operations to demonstrate effectiveness under real-world operating conditions. Longstanding cooperation with mining companies, equipment manufacturers, trade associations, labor organizations, and other government agencies has facilitated the development and implementation of dust control technologies.
OMSHR in-house research projects are addressing dust control issues found in underground coal mining, coal and nonmetal surface mining, and mineral processing operations. In addition to using in-house expertise, OMSHR has ongoing contracts with mining equipment manufacturers, instrumentation companies, and universities to take advantage of their expertise and capabilities.
The program has made several significant accomplishments and is continuing research to meet its goals; some milestones and highlights are listed below:
- Developed a “Helmet CAM” technique for identifying sources of high dust exposures for mobile workers. The technique incorporates a video camera attached to the worker’s hard hat in conjunction with a real-time dust sampler. OMSHR has developed software that allows for synchronized comparison of the video and dust files to identify high dust sources. This information can then be used to focus development on the most problematic dust sources.
- Developed and certified two real-time personal dust monitors (one with a cap lamp and one without) that have been incorporated as a compliance sampling instrument in a new respirable dust rule for the coal mining industry.
- Developing a prototype self-propelled, free-standing respirable dust scrubber for use on continuous miner sections. This unit is designed to remove respirable dust from ventilating air downwind of the continuous miner to reduce the exposure for workers positioned in the return air of the continuous miner. The scrubber, being developed under a contract with a mining equipment manufacturer, has been tested in the laboratory and will be tested in a mine upon MSHA approving the scrubber for use in underground coal mines.
- Developed a spray manifold for installation on the tailgate end of a longwall shearer that provides improved dust control for the tailgate shearer operator and jack setter. Testing in the full-scale longwall gallery has identified effective operating parameters for this spray system. OMSHR is seeking a cooperating mine to conduct an underground evaluation.
- Quantified dust levels generated in 20-foot deep cuts with and without flooded-bed scrubbers operating. This information provides MSHA and mine operators with data that can help them select mining techniques that minimize the respirable dust exposure for workers on continuous mining faces.
- Conducting tests to evaluate the potential of using foam to reduce respirable dust liberation during shield advance. The goal is to apply foam to the exposed mine roof in front of the shields prior to their advance in order to wet the immediate roof and promote agglomeration in the broken material on top of the shields. Laboratory testing of different foaming agents, foam generators, and application techniques is ongoing to identify suitable foam for underground evaluation.
- Past research conducted on filtration/pressurization systems for enclosed cabs on mobile mining equipment has identified guidelines for successful implementation of these controls. OMSHR has utilized this knowledge to design and install similar systems on operator booths/compartments in mineral processing operations and is conducting evaluations at three different field sites.
- Developing a portable, mine-worthy silica analysis instrument and measurement procedure that can be used at the end of a sampling shift to analyze for the quartz content on filters taken from respirable dust samplers. If overexposures are detected, changes in dust control technologies and/or operating practices can be implemented on the next shift to prevent further overexposures.