California's Division of Occupational Safety and Health (Cal/OSHA) released a draft emergency regulation on September 16, 2026 that would prohibit the manufacture, fabrication and installation of engineered, or artificial, stone containing more than 1% crystalline silica by weight. The proposal is in a public comment period and is not yet in force.
The draft would also prohibit onsite fabrication and onsite cutting, with a narrow exception for minor onsite adjustments needed to improve the fit of pre-fabricated pieces. Public comments are open through September 30, 2026, while the standard still requires approval by the California Occupational Safety and Health Standards Board (COSHSB).
What the draft would cover
The proposed threshold is material-specific: engineered stone with more than 1% crystalline silica by weight would fall within the prohibition. The text covers manufacture, fabrication and installation. It also addresses the jobsite stage, barring onsite fabrication and cutting except for minor fit adjustments to pieces fabricated before installation.
That distinction matters for specifications and procurement records. The proposal concerns engineered stone rather than every surface used in a countertop project. Fired ceramic and porcelain tiles and slabs are expressly exempt. Buyers considering an engineered quartz surface should therefore track the proposed rule's material threshold and the status of the standard rather than treating the draft as a current statewide prohibition.
Items stated in the September draft
- Engineered stone above 1% crystalline silica by weight would be covered.
- Manufacture, fabrication and installation would be prohibited if the rule is adopted.
- Onsite fabrication and cutting would be barred, apart from minor fit adjustments to pre-fabricated pieces.
- Fired ceramic and porcelain tiles and slabs would remain exempt.
The wording remains a draft, so commercial decisions should distinguish between its proposed scope and an adopted requirement. Cal/OSHA released it after COSHSB unanimously voted on May 21, 2026 to direct the agency to draft a standard. The current comment window is part of that rulemaking path, not an indication that the requirements have already taken effect.
Approval and transition timing
If COSHSB adopts the emergency regulation, it would take effect 60 days after official adoption. The brief does not set a fixed adoption date. If approval occurs at the Board's October or November meeting, the regulation could become effective as early as December 2026 or January 2027.
The draft includes a defined transition for material already in the supply chain. Engineered-stone surfaces purchased, contracted for or held in possession before adoption could still be worked, but the work would have to be completed within 180 days after adoption. That is a sell-through window for existing inventory, not an open-ended exemption for future purchases.
Importers and fabricators also face a separate US trade setting through the US quartz safeguard TRQ. The proposed California rule has a different purpose and process: it is a draft occupational-safety regulation. Keeping those two developments separate is important when reviewing timing, product availability and project commitments.
Worker-health background and industry response
As of September 10, 2026, California had confirmed 644 silicosis cases and 35 deaths among engineered-stone countertop workers, most of them immigrant fabricators. Those figures form the worker-health backdrop to the proposed standard. Buyers seeking the underlying context can review the silicosis epidemic report.
The International Surface Fabricators Association (ISFA) said it will propose an alternative shop-licensing program for California instead of an outright ban. That response is a proposal from the industry association; it does not change the status of Cal/OSHA's draft or the need for COSHSB approval.
The next formal milestone remains the Board's consideration. Until then, suppliers, specification teams and fabricators have a limited public-comment period in which to assess the text, its silica threshold, its exemption for fired ceramic and porcelain products, and its transition treatment for stock already purchased, contracted for or possessed.
What it means for buyers
For buyers with California work, the practical starting point is to confirm whether a proposed engineered-stone surface is above the draft's more-than-1% crystalline-silica threshold and to retain clear records for any material already ordered or held before adoption. The proposed 180-day completion period applies only after adoption and only to that existing category of material.
Specifications should avoid describing the draft as a rule already in effect. The comment period runs through September 30, 2026, and a possible effective date depends on Board approval and the 60-day period after official adoption. Procurement teams may also want to separate products that are covered by the proposed engineered-stone language from fired ceramic and porcelain tiles or slabs, which the draft exempts.
For cross-border sourcing, the regulatory question should be reviewed alongside, rather than conflated with, the federal quartz safeguard framework. The available facts point to a moving California proposal, an industry licensing alternative and a transition mechanism for qualifying inventory. They do not establish a fixed adoption date or a current ban.
