The respirable crystalline silica (RCS) rule applies to all occupational exposures of RCS in construction work, except where employee exposure will remain below the action level of 25 micrograms per cubic meter of air (25 μg/m3) as an 8-hour time-weighted average (TWA) under any foreseeable conditions. OSHA’s current permissible exposure limit (PEL) for RCS is 50 μg/m3, per 1926.1153. Prior to 2016, OSHA’s construction industry PEL for crystalline silica was 250 μg/m3. It was established in 1971 based on research from the 1960s. Recent scientific evidence, however, shows this PEL didn’t adequately protect worker health.
Crystalline silica is one of the most common elements on the planet, just behind oxygen. About 2.3 million workers are exposed to it in their workplace. It’s about 100 times smaller than sand and can be found on construction sites in building materials such as concrete, block, stone, sand, and mortar. Workers are commonly exposed to RCS when they cut, sand, drill, grind, or crush materials containing it. Workers exposed to RCS have an increased risk of developing serious adverse health effects including silicosis, lung cancer, chronic obstructive pulmonary disease, and kidney disease.