MSHA Urged to Enact Standards for Respirable Crystalline Silica for Coal and Metal-non-Metal Mines

January 11, 2020
David G. Zatezalo
Assistant Secretary
Mine Safety & Health Administration Room SC330
201 12th Street South Arlington, VA 22202-5452
Dear Mr. Zatezalo:
The American College of Occupational and Environmental Medicine (ACOEM) urges you to rapidly act upon your August 29, 2019, Request for Information (RFI) and update your regulations to address silica exposure to miners.
ACOEM is a national medical society representing 4,000 occupational medicine physicians and other health care professionals devoted to promoting optimal health and safety of workers, workplaces, and environments. ACOEM is dedicated to improving the care and well-being of workers through science and the sharing of knowledge.
In 2005, the National Institute for Occupational Safety and Health (NIOSH) reported a concerning increase in rapidly progressive coal workers pneumoconiosis (CWP), particularly in young miners (Antao et al., 2005). Since then, this trend has continued, and a number of studies have identified the cause to be silica and silicate exposures (Laney et al., 2010; Blackley et al., 2016; Cohen et al., 2016; Blackley et al., 2018; Hall et al., 2019).
The technology exists to control exposure to dust, including silica dust, both in the mines and topside (NIOSH, 2019). MSHA’s silica exposure limit is woefully out of date and inappropriately linked to coal dust monitoring, which limits MSHA’s ability to cite and fine mine owners for overexposures to silica (OIG, 2020). The Occupational Safety and Health Administration (OSHA) updated and expanded their regulations for respirable crystalline silica in 2016. MSHA should take advantage of OSHA’s extensive research and adopt silica standards that are at least as protective as OSHA’s.
OIG notes that MSHA has been aware and working on a rule to lower silica exposure limits for over two decades! The RFI conducted over one year ago generated many thoughtful comments. ACOEM is in agreement with comments by the American Thoracic Society (ATS) and the American Public Health Association (APHA), among others. In particular, ACOEM recommends that MSHA enact standards for respirable crystalline silica (not just quartz) for both coal mines and metal-non-metal mines. The standards should rely on the hierarchy of controls, in particular engineering controls, and not on use of personal protective equipment, i.e., respirators. As recommended by RFI commenters and by OIG, the standards should require more frequent and targeted sampling for silica, so as to obtain representative silica levels in high-risk jobs, such as roof bolting.
Regarding medical surveillance for silica-exposed miners, the medical surveillance requirements in the OHSA silica standards are an excellent model [OSHA, 2016]. However, we agree with ATS that high risk miners should have enhanced surveillance. In particular, miners in high-risk locales, i.e., central Appalachia, or found to have high exposure levels through silica monitoring, should be examined more frequently than the usual five years. We recommend a frequency of two-three years. To enable such a two-tier surveillance system, we encourage MSHA to adopt explicit criteria, based on exposure levels and findings of prior medical surveillance exams, to identify workers and workplaces that require more intensive surveillance.
Regarding diagnostic tests, both low-dose chest CT scans and diffusion capacity as part of pulmonary function testing have been found to be more sensitive for early evidence of progressive pneumoconiosis (Perret et al., 2020; ATS, 2019). These diagnostic tests should be used when evaluating miners identified to be at high risk of silica-related disease. MSHA should also consider ways to increase miners’ participation in medical surveillance so that miners can make good decisions about their health.
In summary, there is no question that increasing numbers of miners, particularly young miners, are suffering and dying of severe lung disease due to their work in the mines. Both the causes of and solutions to this epidemic are known. It is time for MSHA to fulfill its mission to ensure safe, healthful workplaces for U.S. miners and prevent needless illness and deaths.
Beth A. Baker, MD, MPH, FACOEM
[ATS, 2019] American Thoracic Society letter, October 28, 2019 with comments to MSHA in response to RIN 1219-AB36.
Antao VC, Petsonk EL, Sokolow LZ, et al. Rapidly progressive coal workers’ pneumoconiosis in the United States: geographic clustering and other factors. Occup Environ Med. 2005;62:670-674. doi: 10.1136/oem.2004.019679.
Blackley D, Crum J, Halldin C, Storey E, Laney A. Resurgence of Progressive Massive Fibrosis in Coal Miners — Eastern Kentucky, 2016. MMWR Morb Mortal Wkly Rep. 2016;65:1385-1389. doi:
Blackley DJ, Halldin CN, Laney AS. Continued Increase in Prevalence of Coal Workers’ Pneumoconiosis in the United States, 1970-2017. Am J Public Health. 2018;108(9):1220-1222. doi:10.2105/AJPH.2018.304517.
Cohen RA, Petsonk EL, Rose C, et al. Lung pathology in U.S. coal workers with rapidly progressive pneumoconiosis implicates silica and silicates. Am J Respir Crit Care Med. 2016;193(6):673-680.
Hall NB, Blackley DJ, Halldin CN, Laney AS. Current review of pneumoconiosis among US coal miners. Curr Environ Health Rep. 2019;6(3):137-147. doi:10.1007/s40572-019-00237-5.
Laney AS, Petsonk EL, Attfield MD. Pneumoconiosis among underground bituminous coal miners in the United States: is silicosis becoming more frequent? Occup Environ Med. 2010;67(10):652-656. doi:10.1136/oem.2009.047126.
[NIOSH, 2019] Dust control handbook for industrial minerals mining and processing, Second Edition. March 2019. National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Department of Health and Human Services. Accessed at:
[OIG, 2020] MSHA Needs to Improve Efforts to Protect Coal Miners from Respirable Crystalline Silica. Office of the Inspector General, Office of Audit, U.S. Department of Labor, November 12, 2020. Report Number 05-21-001-06-001. Accessed at:
[OSHA, 2016] Respirable crystalline silica. Standard 1910.1053(i) Medical surveillance. Accessed at: and Appendix B. Medical Surveillance Guidelines. Accessed at: regs/regulations/standardnumber/1910/1910.1053AppB
Perret JL, Miles S, Brims F et. al. Respiratory surveillance for coal mine dust and artificial stone exposed workers in Australia and New Zealand: A position statement from the Thoracic Society of Australia and New Zealand. Respirology. 2020;25(11):1193-1202. doi: 10.1111/resp.13952. Epub 2020 Oct 13.