Public Health Goal for Methyl Tertiary Butyl Ether in Drinking Water

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To: Winston H. Hickox, Secretary for Environmental Protection

From: Joan E. Denton, Ph.D., Director

Date: March 9, 1999

Subject: Adoption of a Public Health Goal for Methyl Tertiary Butyl Ether in California drinking water

In accordance to Health and Safety Code, Section 116365 (California Safe Drinking Water Act of 1996, SB 1307, Calderon/Sher), the Office of Environmental Health Hazard Assessment (OEHHA) hereby adopts a Public Health Goal (PHG) of 13 ppb (parts per billion, or micrograms per liter) for methyl tertiary butyl ether (MTBE) in drinking water based exclusively on public health considerations.

OEHHA has completed a technical support document which provides the basis for the adoption of the PHG for MTBE. This document has undergone peer review, a public workshop, and two public review and comment periods in fulfillment of the requirements of Health and Safety Code, Section 57003 (SB 1082). The final document incorporates changes in response to comments and will be available on our web site.

The technical support document provides information on health effects that may result from MTBE exposure and estimates the level of the contaminant in drinking water that would pose no significant health risk to individuals consuming the water on a daily basis over a lifetime. PHGs represent non-mandatory goals based solely on public health considerations, and are developed based on the best available data in the scientific literature. The document provides technical assistance to the Department of Health Services (DHS) for establishing a primary drinking water standard (Maximum Contaminant Level, or MCL) which also considers economic factors and technical feasibility. It also provides relevant information useful to federal, state, and local public health officials.

 Neither the U.S. Environmental Protection Agency (U.S. EPA) nor California DHS has established an MCL for MTBE. California has recently adopted a Secondary MCL of 5 ppb based on taste and odor effective January 7, 1999. The Drinking Water Advisory Level recommended by U.S. EPA in 1997 is 20 to 40 ppb.

OEHHA appreciates this opportunity for developing the PHG for MTBE in fulfillment of our mission in environmental and public health protection.