N-Methyl-N-Formylhydrazine Added to the Proposition 65 List for Cancer

N-Methyl-N-Formylhydrazine Listed as a Carcinogen

Effective December 8, 2025, the Office of Environmental Health Hazard Assessment (OEHHA) added N-methyl-N-formylhydrazine to the Proposition 65 list as a carcinogen. This listing was done via the “State’s Qualified Experts” mechanism, based on the Carcinogen Identification Committee’s (CIC) determination that this chemical was clearly shown to cause cancer. 

The warning requirement for significant exposures to N-methyl-N-formylhydrazine will take effect on December 8, 2026.

Summary of CIC Meeting

A meeting of the CIC was held on November 18, 2025, starting at 10:00 am. During the meeting, OEHHA staff presented a summary of evidence on the carcinogenicity of N-methyl-N-formylhydrazine. This was followed by a discussion and deliberation on the evidence by the CIC, and by an opportunity for public comment. The CIC then determined that N-methyl-N-formylhydrazine was clearly shown, through scientifically valid testing according to generally accepted principles, to cause cancer by a vote of 8 (yes) to 1 (no). 

Ahead of the meeting, OEHHA had issued a request for relevant information on the potential carcinogenicity of N-methyl-N-formylhydrazine, which opened on November 29, 2024 and closed on January 10, 2025. The data call-in was followed by publication of the hazard identification document entitled “Evidence on the Carcinogenicity of N-Methyl-N-Formylhydrazine ” and a public comment period was open from August 29, 2025 to October 13, 2025. 

At the meeting, the CIC also voted 9 — 0 in favor of the consent item to remove butoxy polypropoxy polyethoxy ethanol – iodine complex, chlorophacinone, sodium chlorate, and tetraglycine hydroperiodide from the list of chemicals for which testing is required but has been inadequate (California Code of Regulations (CCR) Title 27 Section 27000). As described in the OEHHA staff report, data requirements for these compounds have been fulfilled, and further carcinogenicity (oncogenicity) and reproductive toxicity (teratogenicity) testing are not required. This list of chemicals is distinct from the Proposition 65 list.

Finally, OEHHA staff presented updates on chemical listings, safe harbor levels, and other regulations and litigation since the last CIC meeting.

Meeting Agenda

  1. Welcome and Opening Remarks
  2. Consideration of Listing N-Methyl-N-Formylhydrazine for Carcinogenicity under Proposition 65:
    1. Staff presentation
    2. Committee discussion
    3. Public comments
    4. Committee discussion and decision
  3. Consent Item - Update of the California Code of Regulations Title 27 Section 27000 List of Chemicals Which Have Not Been Adequately Tested as Required (staff report)
  4. Staff Updates
    1. Chemical listings
    2. Safe harbor levels
    3. Other regulations and litigation
  5. Summary of Committee Actions

Data Call-In

On November 29, 2024, OEHHA started a data call-in process to solicit information on N-methyl-N-formylhydrazine from the public. 

Link to Public Comments

Downloads

Chemical Reference