#143 Crystalline Silica

Crystalline silica is a basic component of soil, sand, granite, and masonry products. Different types of silica include quartz, the most common form, and cristobalite and tridymite. All 3 forms may become respirable size particles when workers chip, cut, drill or grind objects that contain crystalline silica.

About 1.85 million construction workers in the U.S. are exposed to respirable crystalline silica (aka silica dust) in the workplace. The seriousness of the health hazards associated with silica exposure is demonstrated by the fatalities and disabling illnesses that continue to occur in sandblasters and rock drillers. Inhalation of small crystalline silica particles leads to increased risk of developing lung cancer, chronic obstructive pulmonary disease, and kidney disease. Additionally, breathing crystalline silica dust can cause silicosis, which in severe cases can be disabling, or even fatal. Silicosis may occur when the respirable silica dust enters the lungs and causes the formation of scar tissue, thus reducing the lungs’ ability to take in oxygen. There is no cure for silicosis. Since silicosis affects lung function, it makes one more susceptible to lung infections like tuberculosis.

Silica dust exposure can occur during many different construction activities. The most severe exposures generally occur during abrasive blasting with sand to remove paint and rust from bridges, tans, concrete structures and other surfaces. Other construction activities that may result in severe exposure include: jack hammering, rock/well drilling, concrete mixing, concrete drilling, brick and concrete block cutting and sawing, tuck pointing, tunneling operations. Exposure can be minimized by wearing respirators and by using common dust control methods, such as wetting down work operations, enclosing operations, and by using a vacuum to collect dust where it is generated.

OSHA is implementing a new silica standard for construction beginning in September 2017. The new standard requires that silica dust particles must be limited to 50 micrograms per cubic meter of air over an average of 8 hours (the same as the Cal/OSHA standard). Contractors are also now required to develop a written silica exposure control plan, designate someone to implement the plan, adjust housekeeping practices to minimize exposure, provide medical exams to employees exposed to silica, train workers on how to limit exposure, and to keep records of workers’ exposure and related medical treatments, unless silica dust levels can be kept below 25 micrograms. Lack of compliance may result in heavy fines.