SACRAMENTO - The California Department of Health Services (CDHS) has proposed a maximum contaminant level (MCL) for perchlorate in drinking water of 6 parts per billion, State Public Health Officer Dr. Mark Horton announced today. If the proposed standard is adopted, public water systems cannot provide drinking water that exceeds a MCL without notifying their customers and must take steps to bring their water supply into compliance with drinking water regulations.

CDHS’ announcement opens a public comment period that ends on Nov. 3. A public hearing will be held at 10 a.m. on Oct. 30 in CDHS’ auditorium, 1500 Capitol Ave., Sacramento.

"Establishing the MCL allows CDHS to address a contaminant that, unfortunately, is quite common in certain areas of California," Horton said. "Perchlorate’s potential for harm is of concern to pregnant women and their developing fetuses, as well as children, so limiting exposure to this contaminant is important for protecting public health."

Perchlorate, primarily used in rocket fuel, explosives, fireworks, road flares and airbag inflation systems, is an inorganic chemical that is known to interfere with iodine uptake of the thyroid gland. A reduction in iodine uptake can result in decreased production of thyroid hormones, which are needed for prenatal and postnatal growth and development, as well as for normal metabolism and mental function in the adult.  

State law requires CDHS to establish a MCL for perchlorate that protects public health, but also is as close to the Public Health Goal (PHG) as technically and economically feasible. PHGs are levels of contaminants in drinking water that would not be expected to pose a significant health risk to individuals consuming an average of two liters a day of water over a 70-year lifetime. A PHG for perchlorate was established in 2004 by the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA). OEHHA’s PHG for perchlorate is 6 ppb, the same as the MCL being proposed and consistent with the findings of a 2005 report on the chemical by the National Academy of Sciences.

CDHS began monitoring for perchlorate in 1997. In 1999, CDHS required water systems to monitor for the chemical as an "unregulated contaminant" to collect information on the extent of contamination throughout the state. Results from nearly 7,000 drinking water sources in California showed perchlorate to be present in approximately 450 sources in approximately 110 public water systems. Perchlorate has been detected primarily in groundwater wells located in Los Angeles, Orange, Riverside, San Bernardino and Sacramento counties.  The chemical has also been detected in the Colorado River, an important source of water for drinking and irrigation in Southern California.

The proposed regulation, accompanying documents and information about submitting comments and the public hearing are on the CDHS Web site at http://www.dhs.ca.gov/ps/ddwem/chemicals/perchl/perchlindex.htm.

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