The proposed rule mandates a rapid phase-out of the material, which is often composed of at least 90% crystalline silica. Once the regulation takes effect, employers will have 60 days to cease purchasing new high-silica stock and a total of 180 days to exhaust existing inventories before a full prohibition on fabrication begins. This timeline allows shops roughly six months to transition to safer alternatives, a shift mirroring Australia’s nationwide ban enacted in 2024.

Medical evidence suggests that artificial stone is uniquely hazardous compared to natural stone due to the release of nano-sized, high-surface area dust during cutting and grinding. This toxic combination, exacerbated by resins and heavy metals, has been linked to 644 confirmed cases of silicosis in California. James Nevin, a partner at Brayton Purcell LLP, stated that the agency’s action acknowledges that standard control measures have failed to protect the workforce from this progressive and fatal lung disease. Cal/OSHA is accepting public comments on the draft through September 30, 2026, ahead of a final vote by the Standards Board.