# Engineering Controls Database

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## Best Practices for Dust Control in Coal Mining – Surface Mines –Controlling Haulage Road Dust

| Problem:                | Respirable dust exposure has long been known to be a serious health threat to workers in many industries. In coal mining, overexposure to respirable coal mine dust can lead to coal workers’ pneumoconiosis (CWP). CWP is a lung disease that can be disabling and fatal in its most severe form. In addition, miners can be exposed to high levels of respirable silica dust, which can cause silicosis, another disabling and/or fatal lung disease.  Exposure to coal mine dust may also increases a miner’s risk of developing chronic bronchitis, chronic obstructive pulmonary disease, and pathologic emphysema. Once contracted, there is no cure for CWP or silicosis. The goal, therefore, is to limit worker exposure to respirable dust to prevent development of these diseases.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
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| What this means to you: | U.S. mine workers continue to be at risk of exposure to excessive levels of silica dust. The percentage of Mine Safety and Health Administration (MSHA) dust samples during 2004–2008 that exceeded the applicable or reduced respirable dust standard because of the presence of silica were: 12% for sand and gravel mines, 13% for stone mines, 18% for nonmetal mines, 21% for metal operations, and 11% for coal mines [MSHA 2009]. At surface mining operations, occupations most frequently exceeding the applicable respirable dust standard are usually operators of mechanized equipment such as drills, bulldozers, scrapers, front-end loaders, haul trucks, and crushers.Off-road haul trucks used in the mining industry typically contribute most of the total dust emissions at a mine site. Given their mobility, trucks have the potential to expose other downwind mine workers to respirable dust, as well as other truck drivers on the haul road. NIOSH has recently studied the size characteristics, concentrations, and spatial variation of airborne dust generated along unpaved mine haulage roads to examine the potential human health and safety impacts of this dust source and is examining other avenues of truck dust mitigation.  Although most of the airborne dust generated from unpaved haulage roads is nonrespirable, up to 20% is in the respirable size range [Organiscak and Reed 2004]. The most common method of haul road dust control is surface wetting with water. Although the road treatment methods have been shown to be very effective, their application generally involves periodic  maintenance due to road degradation from traffic, dry climatic conditions, and material spillage on the road. Road dust generation then can be inevitable at times during the mining operation if controls are not applied when this degradation occurs.   |
| Description of control: | Techniques for controlling haulage road dust are summarized below:Treatment of unpaved road surfaces. Figure 1 shows the effectiveness of road wetting with water on respirable dust liberation next to the haul road and its time-frame of effectiveness at this mine [Organiscak and Reed 2004]. The road was wetted in the morning but dried out in the afternoon, resulting in much higher dust levels. Other haulage road treatments include adding hygroscopic salts, surfactants, soil cements, bitumens, and films (polymers) to the road surface, which can extend the time of effectiveness between treatments up to several weeks [Organiscak et al. 2003b; Olson and Veith 1987].**Figure 1 - Increase in dust when a wet haul road dries**Increase the distance between vehicles traveling the haul road. Research has shown that airborne dust concentrations generated from haulage roads rapidly decreased and approached ambient air dust levels 100 ft from the road [Organiscak and Reed 2004]. This road dust dissipation and dilution provides an opportunity to use administrative and mine planning controls to reduce worker dust exposure. If a trailing haul truck was not allowed to follow within 20 sec of a leading truck, the resulting distance between trucks allowed generated dust to dissipate. This led to more than a 40% reduction in respirable dust exposure to the following truck [Reed and Organiscak 2005]. Finally, advantageous road layout and traffic patterns can be designed into the mine plan to isolate the dust sources from other workers [Organiscak and Reed 2004].                                                                                                                                                                                                                                                                             |
| References:             | NIOSH [2010]. Information circular 9517. Best practices for dust control in coal mining. Morgantown, WV: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2010-110.MSHA [2009]. Program Evaluation and Information Resources, Standardized Information System. Arlington, VA: U.S. Department of Labor, Mine Safety and Health Administration. Organiscak JA, Reed WR [2004]. Characteristics of fugitive dust generated from unpaved mine haulage roads. Int J Surface Min Reclam Environ 18(4):236–252.Organiscak JA, Page SJ, Cecala AB, Kissell FN [2003b]. Surface mine dust control. In: Kissell FN, ed. Handbook for dust control in mining. Pittsburgh, PA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2003-147, IC 9465, pp. 73–81.Reed WR, Organiscak JA [2005]. Evaluation of dust exposure to truck drivers following the lead haul truck. In: Yernberg WR, ed. Transactions of Society for Mining, Metallurgy, and Explorations, Inc. Vol. 318. Littleton, CO: Society for Mining, Metallurgy, and Exploration, Inc., pp. 147–153.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Keywords:               | coal minerscoal miningminingoff-road haul truckssurface minessurface mining                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |

November 16, 2018
National Institute for Occupational Safety and Health