Crystalline Silica

Employer Information

A coal worker performing coal extraction in a mine.

A coal worker performing coal extraction in a mine. Photo by NIOSH

Tasks that are associated with overexposure to respirable crystalline silica dust include

  • Cutting
  • Breaking
  • Grinding
  • Abrading
  • Drilling concrete, mortar, stone, asphalt, brick, and artificial stone

Under the OSHA Respirable Crystalline Silica Rule, employers are responsible for a range of measures to ensure that workers are protected from crystalline silica. Measures include controlling dust levels below the permissible exposure limit (PEL) of 50 µg/m3 (micrograms of silica per cubic meter of air) as an 8-hour time weighted average (TWA). This is believed to be the maximum daily concentration that nearly all workers can be exposed to for a working lifetime without adverse health effects.

High levels of respirable crystalline silica dust can also be released by the mineral quartz during extraction, transport, and processing at mining operations. The Mine Safety and Health Administration (MSHA) established a PEL (100 µg/m3) for respirable quartz dust to protect mine workers.

Control dust levels by implementing effective engineering controls. This includes using local exhaust ventilation to capture dust at its source and water sprays to suppress dust where it is produced.

Employers should reference the OSHA Respirable Crystalline Silica webpage for more information on the final silica rule, requirements for employers, and specific implementation dates. Employers within states that have an OSHA-approved state plan should follow the applicable standards. Mining operators can go to the NIOSH Mining webpage for silica-related requirements and safe mining guidance.

Protections for Employees When Working Around Silica Dust
  • Ensure that workers follow dust control methods found in the OSHA compliance guides for the construction industry and general industry and maritime.
  • Use wet methods that apply water at the impact site where dust is generated.
  • Remove silica dust using local exhaust ventilation at the point where dust is made.
  • Isolate the work process using enclosures.
  • Use a combination of both water and ventilation controls, if proven effective.
  • Ensure that all engineering controls are working properly and replace water and air filters as necessary to control dust.
  • Implement regular and thorough housekeeping procedures. Avoid dry sweeping or using compressed air.
  • Use respiratory protection when dust controls and safe work practices cannot limit silica exposures below the Occupational Safety and Health Administration’s Permissible Exposure Limit (PEL).
  • Develop and implement a written exposure control plan.
  • Implement housekeeping practices that do not increase employee exposure to crystalline silica.
Silica Medical Surveillance Program
  • Offer medical exams as required by OSHA.
  • Provide worker training about the hazards of silica exposure, tasks where exposures can occur, and ways to limit exposure.
  • Keep records of silica exposure and medical exams for workers.