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Water district ordered to remove chemicals from drinking water

Release Date: 05/05/2006
Contact Information: Wendy Chavez, 415/760-5422

SAN FRANCISCO – The U.S. Environmental Protection Agency recently ordered the Mariposa Public Utility District to reduce the disinfection byproducts levels of total trihalomethanes and haloacetic acids from treated drinking water it provides to customers.

While the system exceeds the federal health standards, no effects on human health are anticipated from this short-term exposure. The EPA does not suggest that customers need alternative sources of drinking water or bottled water.

Total trihalomethanes and haloacetic acids were detected in the district’s water system, which serves as many as 1,800 customers in Mariposa, Calif.

“Chemical byproducts in treated drinking water need to be monitored, reported and reduced to meet federal health standards and protect public health,” said Corine Li, manager of the EPA’s Drinking Water Office for the Pacific Southwest region.

The district is required to notify the public when levels are above health-based standards. The drinking water standard for total trihalomethanes is 80 parts-per-billion; and 60 parts-per-billion for haloacetic acids. The Mariposa Public Utility District system had total trihalomethanes ranging from 81–123 ppb and haloacetic acids ranging from 76– 84 ppb.

After many years of consumption, these chemicals may cause liver, kidney or central nervous system problems and may increase the risk of cancer.

The district violated the standards from July 2004 to December 2005. The order requires the district to submit a compliance plan within 60 days of receiving the order, and to reduce disinfection byproducts to below federal standards no later than December 31, 2007.

The EPA established new disinfection byproduct regulations in December 1998 to protect public health from potentially harmful byproduct chemicals that form when chlorine reacts with natural organic compounds during the treatment process. The Disinfectants and Disinfection Byproduct Rule began regulating surface water systems serving 10,000 or more customers in January 2002. Phased implementation of smaller surface systems, as well as, groundwater systems began in January 2004.

The EPA works closely with the California Department of Health Services, which administers the federal safe drinking water program in the state. The EPA awaits the state's overdue adoption of several drinking water rules. In the absence of state authority, the EPA must administer these rules in the interim period.