Introduction

Crystalline silica is an abundant mineral in the earth’s crust. It occurs in several forms, the most common being quartz. Quartz is a common component of sand, stone, rock, concrete, brick, block, and mortar. Common workplace operations involving cutting, sawing, drilling, and crushing of concrete, brick, block, rock, and stone products (such as in construction operations), and operations using sand products (such as in glass manufacturing, foundries, and sand blasting), can result in worker inhalation of small (respirable) crystalline silica particles in the air.

Inhalation of respirable crystalline silica particles has long been known to cause silicosis, a disabling and sometimes fatal lung disease. Respirable crystalline silica also causes lung cancer. The International Agency for Research on Cancer has designated crystalline silica as carcinogenic to humans, and the U.S. National Toxicology Program has concluded that respirable crystalline silica is known to be a human carcinogen. The National Institute for Occupational Safety and Health (NIOSH) has also recommended that respirable crystalline silica be considered a potential occupational carcinogen. In addition, exposure to respirable crystalline silica has been associated with other respiratory diseases, such as chronic obstructive pulmonary disease (including bronchitis and emphysema), as well as kidney and immune system diseases.

Exposures to crystalline silica are addressed in specific standards for the general industry, shipyard employment, and the construction industry.

OSHA Standards

This section highlights OSHA standards, the Regulatory Agenda (a list of actions being taken with regard to OSHA standards), preambles to final rules (background to final rules), directives (instructions for compliance officers), and standard interpretations (official letters of interpretation of the standards) related to crystalline silica.

Note: Twenty-five states, Puerto Rico and the Virgin Islands have OSHA-approved State Plans and have adopted their own standards and enforcement policies. For the most part, these States adopt standards that are identical to Federal OSHA. However, some States have adopted different standards applicable to this topic or may have different enforcement policies.

General Industry (29 CFR 1910)

• 1910.94, Ventilation [related topic page]
• 1910.1000, Air contaminants
  • Table Z-1, Limits for air contaminants
  • Table Z-3, Mineral dusts

Shipyard Employment (29 CFR 1915)

• 1915.34, Mechanical paint removers
• 1915.1000, Air contaminants

Construction Industry (29 CFR 1926)

• 1926.55, Gases, vapors, fumes, dusts, and mists
  • Appendix A, Gases, vapors, fumes, dusts, and mists
• 1926.57, Ventilation

Regulatory Agenda

• The OSHA Regulatory Agenda contains an entry on crystalline silica.

Preambles to Final Rules

• Air Contaminants (1989)
  • VI. Health Effects Discussion and Determination of Final PEL. Includes information on silica and silicosis.
• Search all available preambles to final rules.

Directives

• National Emphasis Program - Crystalline Silica. OSHA Directive CPL 03-00-007, (2008, January 24). Includes an updated list of industries commonly known to have overexposures to silica; detailed information on potential hazards linked to silica and about current research regarding silica exposure hazards; guidance on calculating the Permissible Exposure Limits (PELs) for dust containing respirable crystalline silica in the construction and maritime industries; and guidance on conducting silica-related inspections.
• Search all available directives.

Standard Interpretations

• Requirements for maintaining Material Safety Data Sheets (MSDSs) for coal including coal dust, fly ash, and silica dust. (2005, April 27).
• Respirators for silica dust must be selected based on exposure levels. (1999, May 12).
• Special emphasis program for silicosis. (1998, March 27).
• Label requirements for crystalline silica. (1991, February 11).
• Search all available standard interpretations.

Construction

For information related to construction, see OSHA's Silica, Crystalline - Construction page.

Hazard Recognition

Recognizing potential hazards is key in preventing and minimizing the effects of silica exposure. Silicosis is a disabling, nonreversible and sometimes fatal lung disease caused by overexposure to respirable crystalline silica. The following references aid in recognizing crystalline silica hazards and health effects.

General Resources

• "Crystalline Silica Exposure" Health Hazard Information for General Industry Employees. OSHA Publication 3176, (2002). A Spanish version is also available. Discusses what silica is, what are its hazards, and what employers and employees can do to protect against exposures to silica.
• Crystalline Silica Exposure Health Hazard Information [52 KB PDF^*, 2 pages]. OSHA Fact Sheet, (2002) A Spanish version [75 KB PDF^*, 2 pages] is also available. Provides information regarding silicosis disease and exposures.
• Silica. National Institute for Occupational Safety and Health (NIOSH) Safety and Health Topic. Provides information about silica as well as links to related publications and references.
  • Occupational Health Guideline for Crystalline Silica. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 81-123, (1981, January). Provides evaluation information for employers, industrial hygienists, and physicians.
• Criteria for a Recommended Standard: Occupational Exposure to Crystalline Silica. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 75-120, (1974). Contains information on health effects, environmental data, work practices, and development of the crystalline silica standard.
• Crystalline Silica Primer [99 KB PDF, 54 pages]. US Department of the Interior, US Bureau of Mines, Branch of Industrial Minerals, (1992). Provides a good starting point for anyone wanting to learn about crystalline silica. Includes information on silica and other pertinent regulatory information.

Health Effects

• Health Effects of Occupational Exposure to Respirable Crystalline Silica. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 2002-129, (2002, April).
• Surveillance for Silicosis, 1993 - Illinois, Michigan, New Jersey, North Carolina, Ohio, Texas and Wisconsin. Centers for Disease Control and Prevention (CDC), Morbidity and Mortality Weekly Report (MMWR) 46(SS1);13-28, (1997, January 31). Describes surveillance information on silicosis disease.
• Preventing Silicosis. National Institute for Occupational Safety and Health (NIOSH), US Department of Labor (DOL), (1996, October 31). Provides a general information sheet about silicosis.
• Silicosis Mortality and Silica Exposure [2 MB PDF, 22 pages]. National Institute for Occupational Safety and Health (NIOSH), (1996, October). Provides a report from NIOSH's Work-Related Lung Disease Surveillance Report and contains information on the mortality rates from silicosis.
• Current Trends Occupational Silicosis - Ohio, 1989-1994. Centers for Disease Control and Prevention (CDC), Morbidity and Mortality Weekly Report (MMWR) 44(04);61-64, (1995, February 3). Describes the investigation of a report of occupational silicosis in Ohio and summarizes the impact of hospital-based reporting on surveillance for silicosis in Ohio during 1989-1994.
• Report on Carcinogens (RoC). US Department of Health and Human Services (DHHS), National Toxicology Program (NTP). Identifies and discusses agents, substances, mixtures, or exposure circumstances that may pose a hazard to human health by virtue of their carcinogenicity.
  • Silica, Crystalline (Respirable Size) [186 KB PDF, 2 pages]. Discusses the carcinogenicity, properties, use, production, exposure, and regulations of crystalline silica.
• Are Other Health Effects of Silica Exposure Being Overlooked? Public Health Institute (David F. Goldsmith), (1997, July 8).  Discusses other health effects of silica that are commonly overlooked.
• Pitfalls in Diagnosing Occupational Lung Disease (OLD) for Purposes of Compensation. (Lawrence Martin), (1995). Lists and summarizes several pitfalls that can occur when physicians diagnose occupational lung diseases.
• Lung, silicosis, polarized light microscopic. The University of Utah, Department of Pathology. Shows a micrograph of a silicosis diseased lung.

Exposure Evaluation

The following references aid in evaluating silica exposures in the workplace.

• Kane F. "The campaign to end silicosis." Job Safety & Health Quarterly (JSHQ). 1997 Winter/Spring. Discusses the national education campaign, "If It's Silica, It's Not Just Dust."
• Exposure to Silica Dust on Continuous Mining Operations Using Flooded-Bed Scrubbers. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 97-147, (1997, August). Describes the hazard of silica exposures when flooded-bed scrubbers are designed improperly, and provides recommendations.
• Silica Crystalline: Quartz - Analytical Methodologies. OSHA, (2003). Reviews analytical methods for silica.
• OSHA Technical Manual (OTM). OSHA Directive TED 01-00-015 [TED 1-0.15A], (1999, January 20).
  • Crystalline Silica. Includes sampling information for crystalline silica.
  • Sample Shipping and Handling. Contains sample handling, packaging, and mailing instructions for industrial hygiene samples to be shipped.
• Cyclone Leak Test Procedure. OSHA, (1997, September 15). Describes a method of leak testing cyclone sampler assemblies used for respirable sampling of silica.
• Silica Industrial Hygiene Monitoring - OSHA Consultation Program [39 KB PDF^*, 3 pages]. OSHA, (1994, August). Shows the x-ray diffraction pattern - quartz standard, and other information for evaluating silica.
• Issues and Controversy: The Measurement of Crystalline Silica. International Symposium, (1992, August 20-21). Includes a paper entitled "Evaluation of the Detectability and Quantification of Respirable Crystalline Silica by X-ray Powder Diffraction Methods."
• Overview of Analytical Procedure [2 MB PDF^*, 1 page]. OSHA. Shows a flow chart for the handling of silica samples.

Sampling and Analysis

• Chemical Sampling Information (CSI). OSHA. Presents, in concise form, data on a large number of chemical substances that may be encountered in industrial hygiene investigations:
  • Silica, Crystalline Quartz, Respirable Dust
  • Silica, Crystalline Tripoli (as Quartz), Respirable Dust
  • Silica, Crystalline Cristobalite, Respirable Dust
  • Silica, Crystalline Tridymite, Respirable Dust
  • Silica (Quartz, Total)
  • Coal Dust (> or = 5% SiO₂)(Respirable Quartz Fraction)

• Partial list of substances that may contain crystalline silica >1%:
  • Soapstone (Total Dust)
  • Soapstone (Respirable Fraction)
  • Portland Cement (Total Dust)
  • Graphite, natural respirable dust
• Other:
  • Silica, Amorphous, Precipitated and Gel
  • Silica, Amorphous, Diatomaceous Earth (<1% Crystalline Silica)
  • Silica, Fused (Respirable Dust)
  • Coal Dust (<5% SiO₂, Respirable Fraction)

Analytical Methods

• Quartz and Cristobalite in Workplace Atmospheres. OSHA Method ID-142, (1996, December). Describes the collection of airborne respirable α-quartz and/or cristobalite in the breathing zone of personnel and the subsequent analysis by x-ray diffraction (XRD). Tridymite can also be collected and analyzed using this method if a reference material and diffraction pattern for tridymite are used.
• Sampling and Analysis of Crystalline Silica - X-ray Diffraction (XRD). OSHA, (1997, June 27). Provides extensive sampling information, including links and frequently asked questions (FAQs).
• NIOSH Manual of Analytical Methods (NMAM). US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 2003-154, (2003). Contains extensive information on direct-reading instruments. The following NIOSH methods use direct-reading techniques:
  • Silica, Crystalline by XRD [35 KB PDF, 8 pages]. Method No.7500.
  • Silica, Amorphous [29 KB PDF, 8 pages]. Method No. 7501.
  • Silica, Crystalline by VIS [23 KB PDF, 5 pages]. Method No. 7601.
  • Silica, Crystalline by IR [22 KB PDF, 5 pages]. Method No. 7602.
  • Silica, Crystalline in coal mine dust, by IR [26 KB PDF, 6 pages]. Method No. 7603.
• Quartz Analytical Method (P-7), Infrared Determination of Quartz in Respirable Coal Mine Dust. Mine Safety and Health Administration (MSHA), (1994, November 14). This method uses infrared to determine the silica content of a sample.

Possible Solutions

Controlling the exposure to silica may be done through engineering controls, administrative actions, and personal protective equipment. Engineering controls include such things as replacing silica with a material that does not contain crystalline silica, using local exhaust ventilation, using containment methods such as blast-cleaning machines and cabinets, and wet sawing, or wet drilling of silica-containing materials. Administrative actions may include limiting the worker's exposure time and requiring workers to shower and change into clean clothes before leaving the worksite. Personal protective equipment may include wearing the proper respiratory protection to keep workers' exposure below the OSHA permissible exposure limit and the use of personal protective clothing. The following references aid in controlling hazards in the workplace.

• Crystalline Silica Exposure in General Industry. OSHA Health Hazard Information Card. Also available as a 52 KB PDF, 2 pages. Provides health hazard information and good work practices for workers.
• Kane F. "The campaign to end silicosis." Job Safety & Health Quarterly (JSHQ), (1997 Winter/Spring). Discusses the national education campaign, "If It's Silica, It's Not Just Dust."
• Silica Flour: Silicosis (Crystalline Silica). US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 81-137 (Current Intelligence Bulletin 36), (1981, June 30). Describes hazards in the silica flour industry and provides control recommendations.
• Controlling Silica Dust from Foundry Casting-Cleaning Operations. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 98-106 (Hazard Controls 23), (1997, December). The local exhaust ventilation system described in this document may keep worker exposures to respirable silica below permissible limits and eliminate the need for workers to wear respirators.
• NIOSH - Supported Study Examines Substitutes for Silica Sand to Further Efforts in Silicosis Prevention. National Institute for Occupational Safety and Health (NIOSH) Update, (1997, March 25). Examines the performance of other abrasive materials.
• Silicosis Prevention Furthered by NIOSH Pilot Program Aiding Identification of Cases in Seven Participating States. National Institute for Occupational Safety and Health (NIOSH) Update, (1997, March 25). Describes a program used to gather occupational information on silicosis disease and silica exposures.
• A Guide to Working Safely With Silica: If It's Silica, It's Not Just Dust [213 KB PDF, 21 pages]. National Institute for Occupational Safety and Health (NIOSH), (1997, January 31). Provides information about the health hazards of silica and suggests ways to prevent silicosis.
• NIOSH Respirator User Notices. National Institute for Occupational Safety and Health (NIOSH), The National Personal Protective Technology Laboratory (NPPTL), (1996, May 23). Provides an update of information on the kinds of respirators approved for abrasive-blast (sandblasting) operations and provides recommendations for selection and use of these respirators.
• Dust Monitoring and Control Downloadable Mining Publications. National Institute for Occupational Safety and Health (NIOSH) Mining Safety and Health Research.
• Handbook for Dust Control in Mining. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 2003-147, (2003, June). Provides methods of dust control in mines by ventilation, water and dust collectors, as well as dust control for mines with continuous miner and roof bolter sections, longwall mines, stone mines, surface mines, underground hard rock mines, and mines with hard rock tunnels. There are additional chapters on finding major dust sources and dust respirators.
• Dust Control Handbook for Minerals Processing. US Department of the Interior, Bureau of Mines, (1987, February). Contains valuable information on preventing dust formation and dust control systems.
• Safe Sandblast Cleaning [115 KB PDF, 2 pages]. Manitoba Safe Work Bulletin 153, (1999, April). Discusses controls required for sandblasting, including respiratory protection, personal protective equipment (PPE), work practices, and other sandblasting equipment requirements.
• Profitt-Henry A. "Silica overexposure in sandblasting." Applied Occupational and Environmental Hygiene 15.7(2000, July): 537-9. Discusses silica problems at a sandblasting operation, and how to eliminate the hazard.
• For additional information, see OSHA's Safety and Health Topics Pages on:
  • Medical Screening and Surveillance
  • Personal Protective Equipment (PPE)
  • Respiratory Protection
  • Sampling and Analysis

Additional Information

Related Safety and Health Topics Pages

• Carcinogens
• Construction Industry
• Hazardous and Toxic Substances

Training

• Silica. OSHA. Links to program information, presentation and training materials, National Institute for Occupational Safety and Health (NIOSH) articles, and so forth.

Safety and Health Success Stories

• The following are accounts submitted to OSHA, or that were based on information obtained by OSHA from secondary sources, where the employer implemented programs or utilized best practices and reported successful results.
  • PJ Hoerr: HEPA-filtered vacuum cleaner
  • PJ Hoerr: Extended water-spray hose

Other Resources

• OSHA Silica Stakeholder Meetings. OSHA. Provides links to summaries of stake holders meetings.
• Silicosis Prevention. Mine Safety and Health Administration (MSHA). Provides links to silica related information.
• Job Hazards - Silica. The University of Washington (UW), Department of Environmental Health, Field Research Consultation Group. Serves the occupational safety and health needs of the State of Washington. Their services are provided without charge to businesses and labor groups to promote the safety and health of workers in Washington state.
• Video: "Don't Let Silica Dust You!". Produced by the Association of Occupational and Environmental Clinics with support from NIOSH, the California Department of Public Health, San Francisco Bay area bricklayers and roofers unions, and other partners, the video describes the use of controls and identifies enablers and barriers for reducing workplace exposure to crystalline silica.

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