A federal exposure limit, an enforcement programme aimed specifically at stone fabrication, and state rules that go considerably further.
Federal OSHA sets a permissible exposure limit for respirable crystalline silica of 50 micrograms per cubic metre as an eight-hour time-weighted average, with an action level of 25 micrograms per cubic metre triggering monitoring obligations. Source: 29 CFR 1926.1153 and the corresponding general industry standard.
OSHA operates a National Emphasis Program directed at establishments that manufacture, finish or install engineered stone, making countertop fabrication one of the most actively inspected silica settings in the country.
California goes furthest. Cal/OSHA's respirable crystalline silica regulation under Title 8 section 5204, adopted permanently following emergency standards introduced in December 2023, imposes task-based controls on work with artificial stone and with natural stone above 10% silica by weight. The Silicosis Training, Outreach and Prevention Act (SB 20) took full effect on 1 January 2026, prohibiting dry cutting, requiring shop certification and classifying silicosis as a serious injury. In May 2026 the state's Occupational Safety and Health Standards Board granted a petition to begin rulemaking that would prohibit the fabrication and installation of artificial stone containing more than 1% crystalline silica, which would bring California close to the Australian position.
Watch this one. California's threshold in that proposed rulemaking is 1%, the same figure Australia legislated and the same boundary the registry uses.
Requirements vary by state and are changing. Confirm with federal OSHA and your state plan.
This is regulatory information, not legal advice or compliance certification. Positions change, implementation can vary within federal jurisdictions, and readers must confirm the current position with the named authority before relying on it.