Initiation of Risk Assessments for Chemicals in Drinking Water (2010)

Jul 9, 2010

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 90 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 85 PHGs as of July 2010. 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. In addition, re-evaluations of the original PHG have been completed for 18 chemicals. OEHHA concluded that no new information was available on some of these that would require significant changes to the PHG document. The re-reviews of several other chemicals required more extensive efforts, for which complete updated documents have been published. The supporting documents are available here.
PHG review documents for all the other chemicals that have state MCLs are currently in preparation, as well as updates of the PHG for several chemicals. Drafts for public comment on eight of these chemicals (antimony, benzo(a)pyrene, hexavalent chromium, methoxychlor, selenium, styrene, TCDD (dioxin) and trihalomethanes) are currently posted on the OEHHA web site. Draft PHG documents for several more chemicals should be released this year. At the initial posting, a 45-day public comment period is provided, followed by a public workshop. All comments received are considered in the preparation of a second draft, which is then posted for a 30-day public comment period. After consideration of comments, the final PHG is then published on the OEHHA web site for public reference and use by DPH in developing California MCLs.
Evaluation is now being initiated for two more chemicals for which PHGs were developed earlier (see Section D). These are now 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 updated PHGs for three chemicals (alachlor, fluoride, and perchlorate) are nearing completion, and second postings for methoxychlor, selenium, and trihalomethanes are also being finalized.
Risk assessments are currently in progress for several other chemicals for which initiation of review has previously been announced. Workload considerations and in a few cases, complicated and difficult toxicological interpretations, do not allow us to project completion schedules for these draft updates:

Atrazine/Simazine
Cyanide
Diethylhexylphthalate
Dibromochloropropane(DBCP)
1,4-Dichlorobenzene
1,1-Dichloroethylene
1,2-Dichloropropane
Endothall
Haloacetic acids
Hexachlorocyclopentadiene
Nitrate/nitrite
Picloram
1,2,4-Trichlorobenzene
Trichlorofluoromethane (Freon 11)
Trichlorotrifluoroethane (Freon 113)

D. Initiation of risk assessments

Risk assessment is being initiated for the following chemicals for which PHGs have already been released, but are being updated after prioritization on the basis of availability of new data, concern about environmental exposures, and potential significance as drinking water contaminants:

Ethylbenzene
Xylene

A brief description of these chemicals is provided below. This announcement solicits the submission of pertinent information on these contaminants that could assist our office in 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 September 1, 2010 to:
Hermelinda Jimenez
PHG Project
Pesticide and Environmental Toxicology Branch
Office of Environmental Health Hazard Assessment
1515 Clay St., 16th floor
Oakland, California 94612

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 DPH for potential revisions to the MCLs for the chemical in drinking water, as described in more detail on the DPH Web site.