7.0 Crystalline Silica
Revised February, 2021
Crystalline silica, also referred to as “quartz”, is a common mineral found in the earth’s crust and is a basic component of the soil, sand, and granite. Cristobalite and tridymite are two other forms of crystalline silica. Crystalline silica is found in many common construction materials including sand, stone, concrete, masonry, mortar and landscaping materials. Crystalline silica is also used to make products such as glass, pottery, ceramics, bricks and artificial stone.
Respirable crystalline silica consists of very small particles of silica (less than 10 µm), at least 100 times smaller than ordinary sand found on beaches or playgrounds for example. Crystalline silica is created when cutting, sawing, grinding, drilling and crushing stone, rock, concrete, brick, block and morter.
There are many types of activities that produce crystalline silica dust which could result in worker exposure to respirable crystalline silica; including but not limited to, the following:
- abrasive blasting with sand,
- abrasive blasting of concrete (regardless of the abrasive)
- sawing brick or concrete,
- sanding or drilling into concrete walls,
- mixing concrete
- sawing, hammering, drilling, grinding, chipping of concrete
- brick and concrete block cutting and sawing
- demolition of concrete and masonry structures
- grinding mortar,
- manufacturing brick, concrete blocks, stone countertops, or ceramic products and cutting or crushing stone
- handling soil samples or silica sand in activities such as dry pouring, mixing, sieving
- crushing, loading, hauling and dumping or rock
- dry sweeping of concrete, rock, or sand dust
- pressurized blowing of concrete, rock, or sand dust
Industrial sand used in certain operations, such as foundry work and hydraulic fracturing (fracking) is also a source of respirable crystalline silica exposure.
7.2 Hazards of Crystalline Silica
Occupational exposures to respirable crystalline silica particles increase the risk of developing serious silica-related diseases, including:
- Silicosis, an incurable lung disease that can lead to disability and death,
- Lung cancer
- Chronic obstructive pulmonary disease (COPD),
- Kidney disease
7.3 Occupational Exposure Limits
OSHA has established a maximum exposure limit, or Permissible Exposure Limit (PEL), for airborne respirable crystalline silica of 50 micrograms per cubic meter (50 µg/m3) of air, calculated as an 8-hour Time Weighted Average (TWA). Additionally, OSHA has established an action level (AL) for respirable crystalline silica of 25 µg/m3, calculated as an 8-hour TWA. Occupational exposures at or above the action level triggers additional requirements, to include medical surveillance and increased air monitoring.
7.4 Crystalline Silica Exposures and Written Exposure Control Plan
The University has developed a written Crystalline Silica Exposure Control Plan that specifies work practices and exposure control procedures. The Exposure Control Plan is available from EH&S. Silica dust hazard training is required of all individuals prior to performing work that involves crystalline silica. Before conducting work that involves potential exposure to crystalline silica, contact EH&S to determine the appropriate exposure control measures needed to perform the work safety.