Crystalline Silica

Exposure Assessment

A worker cutting brick pavers using a masonry saw. Photo by NIOSH

Assessing employee exposure to respirable crystalline silica is critically important to determine the need for exposure controls and personal protective equipment. This page provides NIOSH and other related methods for monitoring and measuring respirable crystalline silica exposure. Prior to exposure monitoring, review each analytical method carefully and consult an American Industrial Hygiene Association (AIHA) accredited laboratory for analysis. An accredited laboratory can provide additional guidance about appropriate sampling methods.

The NIOSH Manual of Analytical Methods (NMAM) is a collection of methods for sampling and analysis of contaminants in workplace air. These methods have been developed or adapted by NIOSH or its partners and have been evaluated according to established experimental protocols and performance criteria. NMAM also includes chapters on quality assurance, sampling, and portable instrumentation.

• NIOSH Method 7500 – Silica, Crystalline, by XRD
  • This is the preferred method for most sampling situations where crystalline silica is in a mineral matrix (i.e., in concrete or asphalt). When resin is expected to be in the dust sample, e.g., from engineered stones, muffle furnace or radio frequency plasma ashing should be specified as the preferred sample processing method. For more information, go to: Caution on Using Tetrahydrofuran for Processing Crystalline Silica Samples From Engineered Stone for XRD Analysis
• NIOSH Method 7602 – Silica, Crystalline, by IR
  • This method is recommended if there are minimal amounts of amorphous silica and silicates in the sample.  There are potential interferences with this method that are difficult to identify without the help of an experienced geologist.
• NIOSH Method 7603 – Silica in Coal Mine Dust
  • For use when analyzing for crystalline silica in coal dust.

NIOSH Pocket Guide to Chemical Hazards

The Pocket Guide is a source of general industrial hygiene information on several hundred chemicals/classes found in the work environment. Key data provided for each chemical/substance includes name (including synonyms/trade names), structure/formula, CAS/RTECS Numbers, DOT ID, conversion factors, exposure limits, IDLH, chemical and physical properties, measurement methods, personal protection, respirator recommendations, symptoms, and first aid.

• Silica, crystalline (as respirable dust)
  • Key data on respirable crystalline silica can be found in the NIOSH Pocket Guide on this page.

Hardware and Software Requirements for Field-based Respirable Crystalline Silica Monitoring

• For end-of-shift silica monitoring.

Other Methods

• Occupational Safety and Health Administration (OSHA) Method ID-142 – Silica, crystalline, by XRD
  • This OSHA method only specifies using Tetrahydrofuran as a sample processing method, and is currently withdrawn. Caution should be applied when using Tetrahydrofuran on dust samples that may contain resins, e.g., from engineered stones.
• Mine Safety and Health Administration (MSHA) Method P7 – Silica in Coal Mine Dust
  • MSHA method for sampling coal dust.