Perchlorate in California's Drinking Water

California and Massachusetts are the only states that have set enforceable drinking water standards for perchlorate in drinking water. Both states acted because there is no federal standard for this contaminant, despite the fact that it has been found in hundreds of drinking water sources at harmful levels across the U.S. While California has shown great leadership in analyzing the dangers of perchlorate and regulating the chemical in drinking water, Clean Water Action and its allies in the environmental community have long contended that its standard of 6 parts per billion (ppb) is not adequately protective of the most vulnerable Californians, namely pregnant women, fetuses, and young developing children. This contention was supported in a reevaluation of the safe level of perchlorate in water released by the California Office of Environmental Health Hazard Assessment (OEHHA) in January 2015. At that time state scientists revised the public health goal (the level at which no substantial health effects would occur within a community from drinking water over a lifetime) from 6 ppb to 1 ppb.  

In mid-2020 Clean Water Action won a major victory when, despite strong opposition from both industry and some water providers, the detection limit for perchlorate was changed to 2 ppb, with an automatic switch down to 1 ppb in three years because of technological innovations.  The detection limit, which was originally 4 ppb, is the level at which technology allows laboratories to reliably see perchlorate in water.  This ultimate lowering of the detection limit to 1 ppb by 2024 will allow Clean Water Action to advocate for a new, more stringent drinking water standard so that more water systems will be treated and more Californians will be protected.

What is perchlorate?

Perchlorate is a chemical primarily used in solid fuel for missiles and rockets. Small amounts of perchlorate are also used in car air bags, military ordinance, fireworks, and fertilizer. At one time it was used as a medication, but serious side effects have resulted in it being used only rarely. While perchlorate is found naturally in the environment, most of it is man-made. Since the 1950s, over 870 million pounds of perchlorate have been manufactured in the United States. As a result of its production, use, and disposal perchlorate is being discovered in soil, drinking water, and irrigation water around the country.

Impacts on California’s Drinking Water

California hundreds of wells impacted by perchlorate, as well as surface waters such as the Colorado River, which serves as a drinking water source for Arizona, Nevada, and much of Southern California. While it is unclear how many people this effects, estimates run into the tens of millions of Californians. Impacted areas include, but are not limited to Rancho Cordova near Sacramento (Aerojet); the Llagas Basin of Santa Clara County including parts of Morgan Hill, San Martin, and Gilroy (Olin Corporation); Santa Clarita (Whittiker Bermite), much of the Inland Empire including the city of Rialto (Black and Decker, Goodrich), and the afore mentioned Colorado River (Kerr McGee in Nevada).

Health Effects

Perchlorate at levels currently found in drinking water may cause serious health problems by interfering with the thyroid’s ability to get enough iodide, thus suppressing thyroid hormones critical to growth, development, and metabolism. Because brain development in fetuses and children follows a very specific and time sensitive schedule, even a short period with insufficient iodide and thyroid hormone can result in irreversible problems. These include learning and behavioral disabilities, impaired gait, impaired hearing and vision, mental retardation, and possibly even autism. Studies also indicate that a significant number of women in the U.S. are already iodide deficient and would need to supplement their iodide intake when pregnant. Exposure to perchlorate in their water and food exacerbates such a situation and puts both the woman and her child at risk. Water and food are the most common routes of perchlorate exposure. Perchlorate has been found in some fruits and vegetables irrigated with perchlorate laden water, in dairy products and meat from animals fed with perchlorate contaminated grass or plants, and in human breast milk. Drinking water standards, therefore, need to be particularly stringent when we consider the impacts of food sources on vulnerable populations, as well as the water itself.

Regulatory History: Polluter Interference and Politics

Since perchlorate was first found in drinking water in the 1950’s, the US Air Force, defense contractors, aerospace, and other industries have interfered with government efforts to determine the extent of contamination and to regulate perchlorate. No action to regulate perchlorate at the national level has yet to be taken. In 2011, however, U.S. EPA reversed its original decision not to regulate perchlorate and is slowly moving toward developing a national drinking water standard.

Given the lack of federal regulation, the California legislature passed SB 1822 (Sher), requiring the State to establish a perchlorate drinking water standard by 2004. Sadly, the standard was delayed, thanks to unfounded legal and administrative challenges by the polluter community. In 2007, however, the California Department of Public Health established a standard of 6 ppb.

While Clean Water Action applauded California’s regulation of perchlorate, we opposed the 6 ppb drinking water standard because of scientific evidence demonstrating that any standard higher than 1 ppb would not be adequately health protective of vulnerable populations. In addition, this standard effectively let major polluters in the State off the hook for cleanup since most perchlorate measurements came in just under the 6 ppb level. Subsequent studies on the effects on fetuses and children, as well as the significant numbers of women of child bearing age who are already iodide deficient and exposures through food sources have substantiated this point of view. That is why we have continued to advocate to set a more protective standard in the state, and why our recent victories are so important.

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