Coal Age

DEC 2012

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rock dust continued Figure 5: Comparison of silica found in bagged and bulk samples. quartz and a high respirable content would provide the potential for quartz inhalation by mine workers when exposed to airborne rock dust. A summary of these results showed that 97.3% of the samples contained less than 2% quartz. This quartz content is relatively low when compared to the 5% quartz level that must be exceeded in airborne respirable coal mine dust samples to result in a reduced respirable dust standard. However, size analysis of the rock dust samples showed that 87.7% of the samples contained over 20% respirable-sized dust, while 29.6% of the samples contained over 30% respirable dust. Not all of the respirable-sized dust in these samples will be present as airborne respirable dust when the rock dust is applied in mine entries. Nonetheless, mine operators should be aware of the potential exposure to respirable rock dust containing quartz and take steps to minimize or eliminate the time that mine workers are exposed to airborne rock dust. For workers required to apply the rock dust, it may also be appropriate for them to wear respiratory protection while completing this task. Acknowledgement Appreciation is expressed to Dr. Chi Man, senior service fellow, and Gregory Green, physical science technician, of the Fires and Explosions Branch of NIOSH for their efforts in completing the size analysis of the rock dust samples. Disclaimer The findings and conclusions in this report are those of the authors and do not necessarily represent the views of NIOSH. 52 www.coalage.com Figure 6: Respirable content found in rock dust samples. References 76 Fed. Reg. 35968 [2011]. Maintenance of incombustible content of rock dust in underground coal mines; final rule. Cashdollar KL, Sapko MJ, Weiss ES, Harris ML, Man C, Harteis SP, Green GM [2010]. Recommendations for a New Rock Dusting Standard to Prevent Coal Dust Explosions in Intake Airways. Pittsburgh, PA:, U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2010-151, Report of Investigations 9679, 2010 May; : 1-49. CFR. Code of Federal Regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register. Fiscor SJ [2011]. MSHA provides update on UBB explosion. Coal Age, 116(7):30-34. Harris ML, Cashdollar KL, Man C, Thimons ED [2009]. Mitigating coal dust explosions in modern underground coal mines. In: Panigrahi DC, ed. Proceedings of the Ninth International Mine Ventilation Congress, New Delhi, India, pp. 143-149. Harris ML, Weiss ES, Man C, Harteis SP, Goodman GV, Sapko MJ [2010]. Rock dusting considerations in underground coal mines. In: Hardcastle S, McKinnon DL, eds. Proceedings of the 13th U.S./North American Mine Ventilation Symposium, Sudbury, Ontario, Canada, MIRARCO Mining Innovation, pp. 267-271. NIOSH [2006]. Float coal dust explosion hazards. U. S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Technology News No. 515, DHHS (NIOSH) Publication No. 2006-125. NIOSH [2011]. Hazard ID: non-conforming rock dust. 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. 2012-102. Ramani RV, Mutmansky JM, Bhaskar R, Qin J [1987]. Fundamental studies on the relationship between quartz levels in the host material and the respirable dust generated during mining. Volume I: Experiments, results and analyses. University Park, PA: Pennsylvania State University, Contract H0358031, Bureau of Mines, U.S. Department of Interior. 1 Samples were collected before MSHA divided District 4, creating a new District 12. 2 Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health (NIOSH). 3 When a respirable dust sample contains greater than 5% quartz, the 2 mg/m3 respirable dust standard is reduced by dividing the % quartz into 10 (e.g., 10รท10% quartz = 1 mg/m3 standard). * Code of Federal Regulations. See CFR in references. Colinet is a senior scientist and Listak is a mining engineer with the NIOSH Office of Mine Safety and Health Research in Pittsburgh. Colinet can be reached at: 412386-6825 (Email: gzc6@cdc.gov). December 2012

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