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NIOSH Respiratory Diseases Research Program

Evidence Package for the National Academies' Review 2006-2007

NIOSH Programs > Respiratory Diseases > Evidence Package > 3. Interstitial Lung Diseases > 3.2 Silica-Induced Respiratory Diseases

3.2c) Assessment of Silica Exposures and Controls

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The OSHA PEL for crystalline silica in general industry53 dates from 1971. The OSHA PEL for crystalline silica in the construction industry54 dates from 1970. Recent studies showed that from 1993-1999, an average of 40 percent of OSHA-collected silica samples exceeded the current PEL in the construction industry.55 A hazard review concluded that even the more restrictive NIOSH REL is not fully protective.56 Revision of the silica standard is an important issue for OSHA. In 1998, the OSHA Office of Regulatory Analysis (ORA) asked NIOSH to collect data on silica exposure and engineering controls in a variety of settings to support their determination of technical feasibility of a proposed rule.


Thirty-two site visits were conducted in 15 states a variety of industries (13 in construction and 19 in general industry) between late 1998 and early 2000. RDRP scientists, in consultation with OSHA ORA personnel, planned and conducted these field studies, and prepared reports on site observations and laboratory reports of air and bulk sample analyses. Of 740 breathing zone samples, 30 percent exceeded the NIOSH REL for crystalline silica and 20 percent exceeded the OSHA PEL. Of the 152 samples from the construction industry, 43 percent exceeded the REL and 36 percent exceeded the PEL. Of the 588 samples from general industry 27 percent exceeded the REL and 16 percent exceeded the PEL.

As a result of these findings, RDRP researchers began a series of projects to evaluate engineering control technologies for various tasks in construction settings, including concrete grinding, cement mixer truck cleaning, and masonry tuck pointing. In addition, RDRP researchers’ involvement with the SENSOR Silica Program led to participation in the New Jersey Silica Partnership,57 which included efforts to evaluate engineering controls to reduce silica dust exposures associated with highway construction tasks, including jack-hammering to break concrete and milling of asphalt pavement. In addition to developing and evaluating engineering controls to reduce exposure to silica, RDRP researchers are developing documents and other information to disseminate these findings so that they can be implemented effectively in the workplace.


The knowledge gained through the evaluation of silica exposures and controls has resulted in several publications authored by RDRP researchers. In addition, the work of RDRP researchers is often cited by other researchers working in this field. The 32 site visit reports from the silica exposure and engineering control study are publicly available upon request. These have been cited several times,58,59,60 indicating their importance as sources of exposure data.

The approximately 20 site-specific reports based on subsequent research efforts in evaluating engineering controls for construction are also available upon request. In 2002 and 2003, RDRP researchers published three peer-reviewed papers based upon this work in “Applied Occupational and Environmental Hygiene” (A3-55, A3-56, A3-57). The site reports and the papers have been cited several times by other authors,61,62,63,64,65,66 indicating that they are a useful source of control technology data for other researchers.

Intermediate Outcomes

OSHA is in the process of preparing a proposed standard.67 The technological feasibility study and cost and impact analysis that is part of the docket for the draft silica in construction standard draws upon the 32-site study and the subsequent engineering control evaluations conducted by RDRP.68

The efforts of the New Jersey Silica Partnership resulted in a New Jersey Department of Transportation requirement to use engineering and work practice controls to limit silica dust exposure levels.69 New Jersey also enacted a law prohibiting the dry grinding and dry cutting of masonry materials.70 The New Jersey Laborers’ Health and Safety Fund has produced a “how to” worksheet that provides instructions for building a jack-hammer with a water-spray dust-control attachment that was developed with the assistance of RDRP researchers.

What’s Ahead

RDRP researchers are currently conducting research that seeks to transfer engineering control knowledge from mining machinery to asphalt milling machines. In addition, work is in progress to issue Workplace Solutions (short, non-technical) documents that provide practical guidance on dust control technology based on the work described above.  Finally, RDRP researchers are involved in efforts to evaluate engineering control technology to control silica dust generated from cutting concrete roofing tiles.

53. 29CFR1910.1000. Table Z-3. Code of Federal Regulations. Washington DC: U.S. Government Printing Office, Office of the Federal Register.

54. 29CFR1926.55. Code of Federal Regulations. Washington DC: U.S. Government Printing Office, Office of the Federal Register.

55. NIOSH [2003]. Work-related lung disease surveillance report 2002. Cincinnati, OH: 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. 2003-111 p74.

56. NIOSH [2002]. NIOSH hazard review – health effects of occupational exposure to respirable crystalline silica.  Cincinnati, OH: 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. 2003-111 p2.

57. Valiante DJ, Schill DP, Rosenman KD, Socie E [2004]. Highway repair: a new silicosis threat. Am J Public Health 94:876–880.

58. Flanagan ME, Seixas N, Majar M, Camp J, Morgan M [2003]. Silica dust exposures during selected construction activities. AIHA Journal 64:319–328.

59. Flynn MR, Susi P [2003]. Engineering controls for selected silica and dust exposures in the construction industry—a review.  Applied Occupational and Environmental Hygiene 18:268–277.

60. Croteau et al. 2004.

61. Flanagan ME. Seixas N, Becker P, et al. [2006]. Silica exposure on construction sites: results of an exposure monitoring data compilation project. J Occup Environ Hyg 3:144-152.

62. Lahiri S, Levenstein C, Nelson DI, et al. [2005]. The cost effectiveness of occupational health interventions: prevention of silicosis. Am J Ind Med 48:503-514.

63. Nij ET, Heederik D [2005]. Risk assessment of silicosis and lung cancer among construction workers exposed to respirable quartz. Scand J Work Env Hea 31, Suppl 2:49-56.

64. Croteau GA,  Flanagan ME, Camp JE, Seixas NS [2004]. The efficacy of local exhaust ventilation for controlling dust exposures during concrete surface grinding. Ann occup Hyg 48:509–518.

65. Valiante DJ, Schill DP, Rosenman KD, Socie E [2004]. Highway repair: a new silicosis threat. Am J Public Health 94:876–880.  

66. Nij ET, Hilhorst S, Spee T, et al [2003]. Dust control measures in the construction industry. Ann Occup Hyg 47:211-218.

67. OSHA [2006]. Standard for occupational exposure to crystalline silica. Request for comments. 
External link: Accessed June 1, 2006.

68. ERG [2003]. Draft final report. Technological feasibility study and cost and impact analysis of the draft crystalline silica standard for construction. (Contract No. Gs-10f-0036k).
External link: Accessed June 1, 2006.

69. NJDOT [2001]. Baseline document change. Subsection 107.10 sanitary, health and safety provisions, crystalline silica safety. February 13, 2001.
External link: Accessed June 1,2006.

70. NJ Title 34 [2004]. 34:5-182 Dry cutting, grinding of masonry, certain circumstances; prohibited.
External link: Accessed June 1, 2006.

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