California Proposition 65: Notice of Intent to List Hydrochlorothiazide, Voriconazole, and Tacrolimus

The California Office of Environmental Health Hazard Assessment (OEHHA) has issued a Notice of Intent to list three substances as known to the State of California to cause cancer under Proposition 65 (Safe Drinking Water and Toxic Enforcement Act of 1986).

The proposed listing is being advanced under the Labor Code mechanism, which applies where substances have been identified as carcinogens by the International Agency for Research on Cancer (IARC). Under this mechanism, OEHHA's role is ministerial — the listing does not require an independent hazard assessment, and public comments are limited to whether IARC has sufficiently identified the specific substances as human or animal carcinogens.

The three substances proposed for listing are:

• Hydrochlorothiazide — a thiazide diuretic widely used in the treatment of hypertension and fluid retention, and present as an active pharmaceutical ingredient in a range of medicinal products
• Voriconazole — a broad-spectrum antifungal agent used in the treatment of serious fungal infections
• Tacrolimus — an immunosuppressant used in organ transplantation and in topical formulations for certain skin conditions

For manufacturers and suppliers, the practical significance of a Proposition 65 listing is that products sold in California which expose consumers or workers to a listed substance above the applicable No Significant Risk Level (NSRL) must carry a warning. This obligation applies regardless of where the product is manufactured.

Public comments must be received by OEHHA no later than 8 June 2026 and should be submitted electronically via oehha.ca.gov/comments.

For the full notice, refer to the OEHHA Proposition 65 Notice of Intent.