Announcement of Availability of a Second Public Review Draft Technical Support Document for Proposed Public Health Goals for Trihalomethanes in Drinking Water


The California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) is announcing the release of a draft document for a second public review describing proposed 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 requires OEHHA to develop PHGs based exclusively on public health considerations. 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. The technical support document, available for download below, presents the scientific information available on the toxicity of the THMs and the calculation of the proposed PHGs. The proposed 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. The draft technical support document was originally released for a 90-day public comment period in October 2018, and underwent an external scientific peer review in May 2019. The draft technical support document has been revised per public and peer review comments and is being released for a second public comment that begins 8 November 2019 and ends 9 December 2019. Following the second public comment period, OEHHA will evaluate all the comments received, and revise the document as appropriate.  After any subsequent revisions, the final document will be posted on the OEHHA website along with responses to the external peer review comments and to major comments received during the two public comment periods.

Further information is available at:

OEHHA, 8 November 2019