1. Home
  2. Water
  3. Initiation of Risk Assessments for Chemicals in Drinking Water (2007)

Initiation of Risk Assessments for Chemicals in Drinking Water (2007)

A.     Requirements


The Calderon-Sher California Safe Drinking Water Act of 1996 requires the Office of Environmental Health Hazard Assessment (OEHHA) to post notices on its Web site of water contaminants for which it is initiating development of public health goals (PHGs) for the chemicals in drinking water.  The law also describes the intent and general context of the PHGs.  PHGs are concentrations of chemicals in drinking water that are not anticipated to produce adverse health effects following long-term exposures.  OEHHA is required to consider potential adverse effects on members of subgroups that comprise a meaningful proportion of the population, including but not limited to infants, children, pregnant women, the elderly, and individuals with a history of serious illness.  The public health goals are non-regulatory in nature but are to be used as the health basis to update the state's primary drinking water standards (maximum contaminant levels, or MCLs) established by the California Department of Public Health (DPH) for chemicals subject to regulation.

The act requires PHGs to be developed for the approximately 88 chemicals for which state or federal MCLs are provided, and review and update the risk assessments that form the basis for the PHGs as appropriate at least every five years.  Other chemicals may be added to the list by legislative or interdepartmental request.  Opportunities for public comment and peer review are provided.

B.     Implementation

OEHHA has published 80 PHGs as of September 2007.  Two MCLs, for gross alpha and gross beta radionuclides, represent screening levels for contaminants rather than specific regulatory standards; for these, OEHHA has provided risk assessments and guidance memoranda.  The technical support documents for these chemicals are posted on the OEHHA Web site.

In addition, PHG re-evaluations have been completed for eight chemicals.  For two of these chemicals (cadmium and glyphosate), a complete new PHG document was prepared and published.  For the six other chemicals (chlordane, 1,2-dichloroethane, 1,3-dichloropropene, inorganic mercury, lindane, and thallium), OEHHA concluded that no new information was available on these chemicals that would require significant changes to the PHG document.  Memoranda to this effect are available here.  The re-reviews of several other chemicals that were announced previously are in progress.  Draft PHG documents for the remaining chemicals with existing MCLs or requests for development of a PHG are in preparation.

Draft PHG documents on three chemicals (chlorite, PCBs, and TCDD) have been posted on the OEHHA Web site for public comment, along with drafts of PHG updates for copper and 2,4-D.  A 45-day public comment period is provided after posting of the initial drafts, along with a public workshop to elicit comments and discussion.  After revision with consideration of comments received, a further 30-day public comment period will follow.  The final revision will include responses to major comments. 

Evaluation is now being initiated for several other chemicals for which PHGs were developed earlier (see Section D), which are being re-reviewed as part of the ongoing PHG update process.  Information relevant to the development of PHGs is requested on each of these chemicals.

C.     PHGs to be released for public review:

Draft documents for the following “new” chemicals (those with no existing PHG) are in progress and are planned for release for initial public review and comment when they are completed:

  • Bromate
  • Haloacetic acids
  • Hexavalent chromium
  • Molinate
  • Selenium
  • Styrene
  • 1,2,3-Trichloropropane
  • Trihalomethanes

Toxicity reviews are in progress for the following additional chemicals, for which initiation of review was previously announced:

  • Alachlor
  • Atrazine and simazine
  • Chlorite
  • Copper
  • 2,4-D (Dichlorophenoxyacetic acid)
  • Fluoride
  • Lead
  • Nitrate/nitrite
  • PCBs (Polychlorinated biphenyls)
  • Trichloroethylene

D.     Initiation of risk assessments

Risk assessment is being initiated for the following list of chemicals:

  • Antimony
  • Bentazon
  • Benzo(a)pyrene
  • Cyanide
  • Dalapon
  • Dibromochloropropane (DBCP)
  • 1,2-Dichlorobenzene
  • 1,4-Dichlorobenzene
  • 1,1-Dichloroethylene
  • 1,2-Dichloropropane
  • Dinoseb
  • Endothall
  • Endrin
  • Hexachlorocyclopentadiene
  • Methoxychlor
  • Oxamyl
  • Pentachlorophenol
  • Picloram
  • 1,2,4-Trichlorobenzene
  • Trichlorofluoromethane (Freon 11)
  • Trichlorotrifluoroethane (Freon 113)

These risk assessments are updates of assessments prepared in the first two years of our program (1997 and 1999).  The chemicals had earlier been prioritized for review on the basis of availability of new data and significance as drinking water contaminants, so these chemicals on the final list were considered of lowest priority.  Little new data are available for most of them.  A brief description of the chemicals is provided below.  This announcement solicits the submission of other pertinent information on the contaminants that could assist our office in preparing or updating the risk assessment and deriving a revised PHG.

Information submitted to OEHHA in response to this request should not be proprietary in nature, because all information submitted is a matter of public record.  Information should be submitted by November 9, 2007 to:


PHG Project
Pesticide and Environmental Toxicology Branch
Office of Environmental Health Hazard Assessment
P.O. Box 4010
Sacramento, California 95812-4010

All data submitted will be considered in the development of the PHG for these chemicals.  If substantive revisions to the original PHG documents are required, the draft documents will be available for discussion in a public workshop and public comment will be solicited as described above in Section B.  The final risk assessments will be utilized by the DPH for potential revisions to the MCLs for the chemicals in drinking water, as described in more detail on their Web site.