Notice of Intent to List Chemicals by the Labor Code Mechanism: Molybdenum Trioxide and Indium Tin Oxide

The California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) intends to list the following chemicals as known to the state to cause cancer under the Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65^[1]): molybdenum trioxide (CAS No. 1313-27-5) and indium tin oxide (CAS No. 50926-11-9).  This action is being proposed pursuant to the “Labor Code” listing mechanism^[2].  OEHHA has determined that each of these substances meets the criteria for listing by this mechanism.

Background on listing by the Labor Code mechanism:  Health and Safety Code section 25249.8(a) incorporates California Labor Code section 6382(b)(1) into Proposition 65.  The law requires that certain substances identified by the International Agency for Research on Cancer (IARC) be listed as known to cause cancer under Proposition 65.  Labor Code section 6382(b)(1) refers to substances identified as human or animal carcinogens by IARC.  OEHHA has adopted regulations concerning these listings in Title 27, Cal.Code of Regs., section 25904.  As the lead agency for the implementation of Proposition 65, OEHHA evaluates whether a chemical’s listing is required.

OEHHA’s determination:  Molybdenum trioxide and indium tin oxide meet the requirements for listing as known to the state to cause cancer for purposes of Proposition 65.

IARC has published on its website “IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 118. Welding, Molybdenum Trioxide, and Indium Tin Oxide.” (IARC 2018).  IARC concludes that molybdenum trioxide and indium tin oxide are classified in Group 2B (“possibly carcinogenic to humans”) based on sufficient evidence of carcinogenicity in animals (IARC 2018).

Opportunity for comment:  OEHHA is providing this opportunity to comment as to whether the chemicals identified above meet the requirements for listing as causing cancer specified in Health and Safety Code section 25249.8(a), Labor Code section 6382(b)(1), and Title 27, Cal. Code of Regs., section 25904(b).  Because these are ministerial listings, comments should be limited to whether IARC has identified the specific chemical or substance as a human or animal carcinogen.  Under this listing mechanism, OEHHA cannot consider scientific arguments concerning the weight or quality of the evidence considered by IARC when it identified these chemicals and will not respond to such comments if they are submitted (Title 27, Cal. Code of Regs., section 25904(c)).

Written comments must be received by Monday, November 23, 2020 to be considered.  This comment period has been extended an additional by 15 days due to the COVID-19 Emergency.

Because of limited in-office staffing during the COVID-19 emergency, OEHHA strongly recommends that comments be submitted electronically through our website at https://oehha.ca.gov/comments, rather than in paper form.  Comments submitted in paper form can be mailed or delivered in person to the address below, but delays may occur if staff are unable to timely access them.

All non-electronic submissions should be directed to:

Comments submitted in paper form may still be mailed or delivered in person to the address below.  Please be aware that most OEHHA employees are currently working remotely so receipt of materials that are mailed or delivered in person may be delayed.

Tyler Saechao
Office of Environmental Health Hazard Assessment
1001 I Street
P.O. Box 4010, MS-12B
Sacramento, California 95812-4010
Telephone: 916-445-6900

Comments received during the public comment period will be posted on the OEHHA website after the close of the comment period.  Electronic files should not have any form of encryption because OEHHA is subject to the California Public Records Act and other laws that require the release of certain information upon request.  If you provide comments, please be aware that your name, address and e-mail may be available to third parties.  OEHHA must also meet federal and state requirements for materials posted on our websites to be accessible to people with disabilities^[3].  We request that comments be submitted in an accessible format to the extent feasible.

If you have any questions, please contact Tyler Saechao at Tyler.Saechao@OEHHA.ca.gov or at (916) 445-6900.