Respirable Crystalline Silica Standards and Resources

graphic of silica in a person's lungsDANGER: Silica exposures from artificial stone (also called engineered stone) are much more toxic and dangerous than silica exposures from other sources such as natural stone or sintered stone. Exposure to silica from artificial stone can lead to rapid onset of severe silicosis, which is permanently disabling and frequently fatal. Uncontrolled artificial stone fabrication presents a significant and immediate health hazard.

This webpage provides a brief overview of Cal/OSHA's standards and links to resources to control employee exposures to respirable crystalline silica (RCS), a known carcinogen that can cause silicosis (an incurable and frequently fatal lung disease), lung cancer, kidney and autoimmune disease, and other serious health effects.

July 1, 2026

Applicable RCS Standards 

Occupational Exposures to RCS in General Industry (Section 5204)

Section 5204 applies to all California workplaces where workers are exposed to RCS except the following:

  • Construction work covered under section 1532.3.
  • Agricultural operations covered under section 3436.
  • Processing of sorptive clays

Section 5204 has requirements including the following subjects (see section 5204 for details):

  • 5204(c) – Permissible exposure limit
  • 5204(d) – Assessment of employee exposures
  • 5204(e) – Establishment of regulated areas
  • 5204(f) – Engineering controls, safe work practices, written exposure control program
  • 5204(g) – Imminent Hazards (Cal/OSHA must immediately halt dangerous operations)
  • 5204(h) – Respiratory Protection
  • 5204(i) – Housekeeping
  • 5204(j) – Medical Surveillance
  • 5204(k) – Medical Removal
  • 5204(l) – Communication of hazards to employees
  • 5204(m) – Reporting of silicosis and lung cancer
  • 5204(n) – Recordkeeping

Updates to Section 5204 – Fabrication of Countertops and Similar Products

The December 2023 and February 2025 updates to section 5204 require employers to provide additional worker protections when fabricating countertops, backsplashes, walls, flooring, waterfall countertop edges, and other products made from slabs or panels.

Any machining, crushing, cutting, drilling, abrading, abrasive blasting, grinding, chiseling, carving, gouging, polishing, buffing, fracturing, intentional breaking, or intentional chipping of the following materials is considered a “High-Exposure Trigger Task”:

  • Artificial stone (also called engineered stone or quartz) products containing more than 0.1 percent crystalline silica by weight
  • Other silica-containing materials, including natural stone, that contain more than 10 percent crystalline silica by weight

High-Exposure Trigger Tasks also include cleaning up, disturbing, or handling wastes, dust, residues, debris, or other materials created during the tasks listed above.

High-Exposure Trigger Tasks automatically require enhanced protections under section 5204, regardless of exposure levels.

Enhanced protections required under section 5204 include, but are not limited to:

  • Effective wet methods
  • Safe housekeeping practices
  • Prohibition of certain unsafe work practices
  • High-level respiratory protection
  • Additional medical surveillance requirements
  • Medical removal protections
  • Reporting of silicosis and lung cancer to CDPH and Cal/OSHA

Cal/OSHA Resources for General Industry

Occupational Exposures to RCS in Construction (Section 1532.3) 

Construction work includes employment existing in connection with the construction, alteration, painting, repairing, construction maintenance, renovation, removal, or wrecking of any fixed structure or its parts. Excavations not covered by other safety orders for a specific industry or operation are also included in construction work. Section 1532.3 applies to exposures to RCS during construction work.

Section 1532.3 has requirements that cover the following (see section 1532.3 for details):

  • 1532.3(c) – Exposure control methods for tasks using Table 1
  • 1532.3(d) – Alternative exposure control methods for tasks not listed in Table 1
  • 1532.3(e) – Respiratory Protection
  • 1532.3(f) – Housekeeping
  • 1532.3(g) – Written exposure control plan
  • 1532.3(h) – Medical surveillance
  • 1532.3(i) – Communication of hazards to employees
  • 1532.3(j) – Recordkeeping

Cal/OSHA Resources for Construction

Section 5155 – Airborne Contaminants 

Section 5155 applies in addition to section 5204 and 1532.3. It requires employers to ensure that employee exposure to RCS does not exceed the permissible exposure limit (PEL).

NOTE: Construction employers who fully and properly implement the engineering controls, work practices, and respiratory protection listed in Table 1 of section 1532.3 for the specific equipment and tasks identified in that table do not have to separately measure employee exposures to confirm they are below the PEL.

What is the action level for RCS?

The action level for RCS is 25 micrograms per cubic meter (µg/m³) of air as an eight-hour time-weighted average. In general, sections 1532.3 and 5204 apply when worker exposures may equal or exceed the action level under any foreseeable conditions. However, employers who perform any high-exposure trigger tasks must comply with section 5204 even if exposures are below the action level.

What is the permissible exposure limit (PEL) for RCS? 

The PEL for RCS is 50 micrograms per cubic meter (µg/m³) of air as an eight-hour time-weighted average. This is the maximum concentration of RCS in air to which an employee may be exposed.

What are the broad categories of requirements in sections 1532.3 and 5204?

The broad categories of requirements are as follows:

Broad Categories of Requirements Section 1532.3 Section 5204 Section 5204 High-Exposure Trigger Tasks
Exposure assessments 1532.3(d)(2) 5204(d) 5204(d)
Methods of compliance (engineering, work practice, and other controls) 1532.3(c) or (d)(3) 5204(f)(1) 5204(f)(2)
Respiratory protection 1532.3(e) 5204(h) 5204(h)(3)
Housekeeping 1532.3(f) 5204(i) 5204(f)(2)(B)
Restricted or regulated areas 1532.3(g)(1)(D) 5204(e) 5204(e)
Written exposure control plans 1532.3(g) 5204(f)(3) 5204(f)(3)
Medical surveillance 1532.3(h) 5204(j) 5204(j)
Medical removal n/a n/a 5204(k)
Communication of RCS hazards to employees 1532.3(i) 5204(l) 5204(l)
Reporting of silicosis and lung cancer 342(a) 5204(m)
and
342(a)		 5204(m)
and
342(a)
Recordkeeping 1532.3(j) 5204(n) 5204(n)

Related Labor Code Requirements 

Amendments to the Labor Code expand definitions and reporting obligations related to silicosis and silica-related lung cancer. The law also requires certain employers engaged in artificial stone fabrication to provide specialized worker training and to submit training attestations annually to Cal/OSHA. These obligations are separate from, and in addition to, Title 8 requirements. Employers should review the applicable Labor Code provisions in addition to Title 8 requirements.

Required Reporting

Links for employer-required reporting:

Additional requirements for employers engaged in artificial stone fabrication:

Additional Resources 

Additional resources for employers and workers:

July 1, 2026