silica exposure Facts, Measurement, and Resources

SKC offers this resource page as a one-stop source for seasoned OEHS professionals and novice industrial hygiene technicians, alike to help you sample for respirable crystalline silica (RCS) to assess exposure levels for compliance and effectiveness of controls to keep workers healthy and safe and safeguard your operation from regulatory risk.  

Silica Questions and Answers

What is Respirable crystalline silica (RCS) and its sources? Crystalline silica is a common mineral found in the earth's crust. Materials like sand, stone, concrete, and mortar contain crystalline silica.   

Where is silica used? Silica is a component in products such as concrete, glass, pottery, ceramics, bricks, and artificial stone. 

What activities cause RCS to become airborne and cause a hazard? Very small particles, at least 100 times smaller than ordinary sand like that found on beaches and playgrounds, are created during high-risk activities including but not limited to: 

• Abrasive blasting with sand 
• Cutting concrete or bricks 
• Sanding or drilling into concrete walls 
• Grinding mortar 
• Manufacturing brick, concrete blocks, stone countertops, or ceramic products 
• Cutting or crushing stone
• Mining activities

Industrial sand use is also a source of RCS exposure. Approximately  2.3 million US workers are exposed to silica.

What industries have the most silica exposure?

• Construction 
• Mining 
• Quarrying 
• Foundry work 
• Concrete production 
• Sandblasting 
• Hydraulic fracturing 
• Stone cutting/ grinding 
• Abrasive blasting

What are the health risks of exposure to RCS? According to OSHA, breathing in very small ("respirable") crystalline silica particles, causes multiple diseases, including:

• Silicosis 
• Lung cancer 
• Chronic obstructive pulmonary disease (COPD) 
• Kidney disease

Exposure to RCS is related to autoimmune disorders and cardiovascular impairment that are life-altering and debilitating disorders annually affecting thousands of workers across the US. 

What are the regulations? OSHA and MSHA regulations offer cohesive exposure limits for RCS exposure, sampling requirements, and controls and reporting guidance in your industry.

• OSHA Final Silica Rule (published March 25, 2016) to better protect workers in construction and general industry
• MSHA Final Silica Rule (published April 18, 2024) to reduce exposure to RCS in mines.

   Summary Exposure Limits in OSHA and MSHA Final Silica Rules 

• Permissible exposure limit (PEL) of 50 micrograms per cubic meter (μg/m³) for a full shift (calculated as an 8-hour time-weighted average or TWA)  
• Action Level for RCS at 25 μg/m³ for a full shift (calculated as an 8-hour time TWA).  

Both OSHA and MSHA silica rules require employers to evaluate the exposure of each employee who is, or may reasonably be expected to be, exposed to RCS. This evaluation should be done using respirable dust samplers that conform to ISO 7708 criteria. Assessment options are spelled out in each regulation.

How can I measure silica exposure? What kind of equipment is needed?

COMPLIANCE SAMPLING

For compliance sampling, you must use a size-selective sampler containing a filter that meets the requirements in OSHA and MSHA Final Silica Rules and an air sampling pump to pull air through the sampler. Resulting samples are sent to an accredited laboratory for analysis, which issues a report of the results. The following PPI Samplers are specifically mentioned in both OSHA and MSHA Final Silica Rules, as is the SKC Aluminum Cyclone. SKC Touch Series air sampling pumps provide accurate, reliable flow rates from 5 to 5000 ml/min with easy touch screen operation.