Silica, which is synonymous with silicon dioxide (SiO2), occurs in both crystalline and noncrystalline (amorphous) forms. Crystalline silica, often referred to as free silica, is the basic component of sand, quartz and granite rock. Amorphous silica has been found to exist in nature as opal, flint, siliceous (silica-containing) glass, diatomaceous earth and vitreous (glass-like) silica.

In addition to mining, several non-mining industries have the greatest number of U.S. workers potentially exposed to respirable crystalline silica: masonry, stonework, tile setting and plastering; services to dwellings and other buildings; concrete, gypsum and plaster products; roofing and sheet metal work; general industrial machinery and equipment; medical and dental laboratories; gas and electric and other utilities; automotive repair shops; pottery and related products; and construction. Significant exposure to crystalline silica can also occur during hydraulic fracturing (“fracking”) to extract natural gas and oil from shale in which sand, water and chemicals are injected into the ground at high pressure.


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What are the hazards associated with silica?

Silicosis is a type of pneumoconiosis that results from inhaling dust that contains crystalline silica. Inhalation of dust containing respirable quartz (crystalline) silica over time results in scarring of the lung tissue. This reduces the ability of the lungs to provide oxygen to the body. Although silicosis is completely preventable, once silicosis begins its effects cannot be reversed even after the individual is removed from silica exposure.

There are three types of silicosis that are distinguished by the length of exposure and relative airborne concentrations. Chronic silicosis occurs after 10 or more years of exposure to relatively low concentrations of crystalline silica. Accelerated silicosis results from exposure to high concentrations of crystalline silica and develops five to 10 years after initial exposure. Acute silicosis develops where free silica concentrations are the highest. The time of onset for symptoms of acute silicosis can range from a few weeks to four or five years following initial exposure.

Is there a special emphasis program associated with this topic?

Occupational exposure to respirable crystalline silica falls within the OSH Division health hazards special emphasis program.

What can I do to protect myself?

Where appropriate, employees engaged in processes that use silica sand and other sources of crystalline silica should consider substituting materials that do not contain silica. When this is not possible, your employer must provide adequate exhaust ventilation and/or ensure the use of wet methods when cutting or drilling into silica-containing materials using high speed equipment (e.g., saws and drills). Equipment used for these operations should be designed by the manufacturer to incorporate dust suppression using water or local exhaust ventilation.

When dust levels are above the permissible exposure limit and engineering and administrative controls have been fully implemented, your employer must provide respiratory protection that meets the requirements of the respiratory protection standard, 29 CFR 1910.134. In addition, adequate hearing protection must be provided when noise levels generated by cutting, drilling, etc. on silica-containing materials exceed an 8 hour time-weighted average of 90 decibels (dB) and a hearing conservation program (general industry) implemented when noise levels meet or exceed an 8 hour time-weighted average of 85 dB as required by the occupational noise exposure standard, 29 CFR 1910.95.

What resources are available to assist employers?

Training and Outreach Services

Presentations on occupational exposure to respirable crystalline silica and health hazards special emphasis program are available for workplaces in general industry and construction and can assist employers in training their staff.  The presentations should be modified to address site-specific conditions and hazards. Other presentations that may be applicable include hazard communication, respiratory protection and personal protective equipment. These pre-recorded webinars on respirable crystalline silica in construction.  hazard communication. and respiratory protection are also available and can be accessed at any time.

In addition, the education, training and technical assistance bureau provides free online safety and health training and outreach services (i.e., speaker's bureau requests, safety booths) upon request. 

The NCDOL Library offers free safety and health videos (including streaming video services) and related research assistance on consensus standards (i.e., ANSI, NFPA, NEC).

Safety and Health Programs

In addition, several example programs pertaining to occupational exposure to silica can be downloaded and customized to fit individual workplaces including hazard communication programrespiratory protection programhazardous chemicals and hearing conservation program, An example PPE hazard assessment is also available and can be customized to fit workplace conditions. Employers are required to perform a workplace hazard analysis to determine what personal protective equipment is necessary to protect employees from continued exposure to identified hazards.

A-Z Safety and Health Topics

Other related resources can be found on the A-Z topics pages for respiratory protection, hazard communication, personal protective equipmentnoise and health hazards special emphasis program

Consultation Services

The consultative services bureau provides free and confidential onsite consultation regarding worksite safety and health hazards.


Which standards apply?

OSH has adopted the following standards which are applicable to silica in North Carolina. Note: Please also check the standards information and activity webpage to see if there has been any recent or upcoming regulatory activity on this topic. 

General Industry

Maritime, Shipyard Employment


In addition, following standards can apply to employee exposure to silica:

  • 29 CFR 1926.52 - occupational noise exposure - construction

  • 29 CFR 1910.95 - occupational noise exposure - general industry

  • 29 CFR 1910.132 - personal protective equipment, general requirements - general industry

  • 29 CFR 1910.134 - respiratory protection - general industry, maritime and construction

  • 29 CFR 1910.1020 - access to employee exposure and medical records - general industry, maritime and construction

  • 29 CFR 1910.1200 - hazard communication - general industry, maritime and construction

Other Applicable Standards

The Which OSHA Standards Apply webpage can also help identify other standards that may be applicable to your worksite.

Where can I learn more?

Compliance Documents

Industry Guides

Technical Assistance

Inquiries about workplace safety and health requirements can be submitted to Ask OSH through the online form, by email to, or by phone at 919-707-7876.