In December, 2025, California’s Office of Environmental Health Hazard Assessment (OEHHA) formally added Bisphenol S (BPS) and N-Methyl-N-Formylhydrazine to the Proposition 65 list, citing concerns related to reproductive harm and cancer risk.
N-Methyl-N-Formylhydrazine Classified as a Carcinogen.
Effective December 8, 2025, N-Methyl-N-Formylhydrazine is officially recognized as a carcinogen under Proposition 65. The designation followed an 8–1 approval vote by the Carcinogen Identification Committee (CIC) during its November 18, 2025 meeting, where the committee concluded that credible scientific evidence demonstrates the chemical’s cancer-causing potential. Businesses will be required to issue clear and reasonable warnings for significant exposures beginning December 8, 2026.
Regulatory review milestones:
· November 2024–January 2025: Public consultation on carcinogenicity data
· August 29–October 13, 2025: Release of the hazard identification report and public comment period
· November 18, 2025: CIC deliberation and approval of the listing
Bisphenol S Expanded to Full Reproductive Toxicant Status
On the same date, OEHHA broadened the existing Proposition 65 listing for Bisphenol S by adding developmental toxicity, thereby classifying BPS as a reproductive toxicant affecting female reproduction, male reproduction, and development. This update also becomes effective on December 8, 2025.
Phased listing history for BPS:
· December 29, 2023: Listed for female reproductive toxicity
· January 3, 2025: Expanded to include male reproductive toxicity
· December 8, 2025: Developmental toxicity added, completing the full reproductive toxicity profile
Implications for Industry
With these additions, Proposition 65 warning obligations are triggered. Companies manufacturing, distributing, or selling products containing these substances must ensure appropriate warnings are provided on products, in workplaces, or other exposure settings. Non-compliance may increase the risk of enforcement actions and litigation.
