On October 23, 2017, the U.S. Occupational Safety and Health Administration (OSHA) began enforcement of its Respirable Crystalline Silica in Construction Standard (Construction Silica Standard). OSHA enforcement of its Construction Silica Standard actually began on September 23, 2017, but for a period of 30 days, OSHA offered compliance assistance in lieu of enforcement for employers who were making good faith efforts to comply with the Construction Silica Standard.

California’s Occupational Safety and Health Administration (Cal/OSHA) has a nearly identical construction silica standard that requires employers to limit worker exposure to respirable crystalline silica above 25 micrograms per cubic meter of air (25 μg/m3) as an 8-hour time-weighted average (TWA) under any foreseeable condition.