Announcement of Publication of Public Health Goals and Technical Support Document for Trihalomethanes In Drinking Water

The Office of Environmental Health Hazard Assessment (OEHHA) of the California Environmental Protection Agency is announcing the publication of Public Health Goals (PHGs) for four trihalomethanes (THMs) found in drinking water as a result of disinfection methods: chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform.  A PHG is the level of a drinking water contaminant at which adverse health effects are not expected to occur from a lifetime of exposure.  The California Safe Drinking Water Act of 1996^[1] requires OEHHA to develop PHGs based exclusively on public health considerations.^[2]  PHGs published by OEHHA are considered by the State Water Resources Control Board in setting drinking water standards (Maximum Contaminant Levels, or MCLs) for California.^[3]

The technical support document, posted on the OEHHA website (https://oehha.ca.gov/water), presents the scientific information available on the toxicity of the THMs and the calculation of the PHGs.  The PHGs of 0.4 parts per billion (ppb) for chloroform, 0.06 ppb for BDCM, 0.1 ppb for DBCM, and 0.5 ppb for bromoform are based on carcinogenicity and are set at a level of risk of one additional cancer case per one million persons exposed over a 70-year lifetime.  OEHHA also presents health-protective drinking water concentrations for noncancer health effects for the THMs. 

A companion document, also available at https://oehha.ca.gov/water, contains responses to public comments received during the two public comment periods that ended in January and December 2019, and comments received in June 2019 from an external scientific peer review.  OEHHA has evaluated all of the comments and revised the technical support document as appropriate. 

If you would like to receive further information on this announcement or have questions, please contact Hermelinda Jimenez at PHG.Program@oehha.ca.gov or at (916) 324-7572.  Written inquiries can also be addressed to:

Pesticide and Environmental Toxicology Branch
Office of Environmental Health Hazard Assessment
California Environmental Protection Agency
P.O. Box 4010, MS-12B
Sacramento, California 95812-4010
Attention: PHG Program

Link to Public Comments

Comment Submissions – Second Public Comment Period (Nov. 8 – Dec. 9, 2019)

Comment Submissions – First Public Comment Period (Oct. 5, 2018 – Jan. 4, 2019)