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

The Office of Environmental Health Hazard Assessment (OEHHA) of the California Environmental Protection Agency is announcing the release of a draft document for public review describing proposed Public Health Goals (PHGs) for the four regulated trihalomethanes (THMs) found in drinking water as a result of disinfection methods: chloroform, bromoform, bromodichloromethane and dibromochloromethane.  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, available for download below, presents the scientific information available on toxicity of the THMs and the calculation of the proposed PHGs.  The proposed PHGs of 0.4 parts per billion (ppb) for chloroform, 0.5 ppb for bromoform, 0.06 ppb for bromodichoromethane, and 0.1 ppb for dibromochloromethane are all 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 non-cancer health effects. 

The draft technical support document is being released for public comment.  The public comment period begins October 5, 2018 and ends November 29, 2018.  This draft document supersedes all previous PHG draft documents for trihalomethanes.

The public is encouraged to submit written comments via OEHHA’s website, rather than in paper form.  Comments may be submitted electronically through the following link:, or they can be emailed to   

Hard-copy comments may be mailed, faxed, or hand-delivered to the address below.  Any written comments concerning this draft PHG document, regardless of the form or method of transmission, must be received by the PHG program by 5:00 p.m. on November 29, 2018 to be considered.

The Office will hold a public workshop on November 29, 2018 at the California Environmental Protection Agency Headquarters Building, 1001 I Street, Sacramento, California, 95814, Coastal Hearing Room, from 10:00 a.m. to 1:00 p.m., or until business is concluded. The workshop will be webcast, which can be accessed on the day of the workshop at OEHHA follows the requirements set forth in Health and Safety Code Sections 57003(a) and 116365 for conducting the workshop and receiving public input. 

The workshop is provided to enable a dialogue between OEHHA scientists and the public to discuss the scientific basis of the proposed PHGs, and to receive comments.  After the public workshop, OEHHA will submit the draft risk assessment for external scientific peer review.[4]  

Following the workshop, public comment period and external scientific peer review, OEHHA will evaluate all the comments received, revise the document as appropriate, and make it available for an additional 30-day public comment period.  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 at the workshop and during the two public comment periods.

If you would like to receive further information on this announcement or have questions, please contact Hermelinda Jimenez at or at (916) 324-7572.  FAX inquiries or comments can be submitted to (916) 323-2265.  Written inquiries or comments 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

Footnotes and References

[1] Codified at Health and Safety Code, section 116270 et. seq.

[2] Health and Safety Code, section 116365(c)

[3] Health and Safety Code, section 116365(a) and (b)

[4] Health and Safety Code section 116365(c)(3)(D)