California Proposes Strict Drinking Water Standard For Rocket Fuel Chemical

The California Department of Health Services (CDHS) announced on Aug. 28 it proposed a maximum contaminant level (MCL) for perchlorate in drinking water of 6 parts per billion (ppb). 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.

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, state officials said. 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.

"Establishing the MCL allows CDHS to address a contaminant that, unfortunately, is quite common in certain areas of California," State Public Health Officer Dr. Mark 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."

Last month, Massachusetts became the first state in the nation to promulgate drinking water and waste site cleanup standards for perchlorate, setting the standard at 2 ppb. Earlier this year, EPA set a interim cleanup goal for perchlorate at 24.5 ppb. However, the federal agency has yet to set an enforceable standard for drinking water.

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 EPA'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 (Health Implications of Perchlorate Ingestion).

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 also has been detected in the Colorado River, an important source of water for drinking and irrigation in Southern California.

CDHS' announcement opens a public comment period that ends on Nov. 3. The proposed regulation, accompanying documents and information about submitting comments and the public hearing are on the CDHS Web site at

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