California moves forward to limit toxic perchlorate contamination - EPA still overdue

California is taking a big leap forward on the path to making the tap water of its residents safer than ever by setting a new public health goal (PHG) for perchlorate - a toxic water contaminant - of 1 part per billion (ppb), about 1 teaspoon of perchlorate in an Olympic-sized swimming pool.

This health-based goal is an important step, but not the final step in regulating the chemical, since the public health goal is not mandatory. Next, the California Water Resources Control Board must set an enforceable standard (known as a Maximum Contaminant Level, or MCL), which factors in health effects, feasibility of detection, clean-up technologies, and cost. We hope California will build on its strong action today and move swiftly to set an enforceable standard.

There is still no national drinking water standard and the Environmental Protection Agency (EPA) has been dragging its feet on setting one for over a decade (EPA website). Instead, there exists a hodge-podge of state-level drinking water regulations and advisories for perchlorate, ranging from about 1 to 25 ppb (ASTSWMO 2011).

Perchlorate is a hazardous chemical component of explosives that was used in rocket fuel, and is still used in fireworks and air bags. It also occurs naturally in Chilean soil nitrate, which has historically been used as fertilizer here in the US. According to a 2010 report of the U.S. Government Accountability Office, perchlorate has been found in the water supply of 45 states, three territories and the District of Columbia, as well as in the food supply. (GAO-10-769). Approximately 4% of 3865 public water supplies tested by EPA - serving over 17 million people- had detections of perchlorate at or above 4 ppb (the lowest level that was looked for) (73 Federal Register 60262, 60270, October 10, 2008). FDA finds it in over half of food samples it analyzed, including baby foods and infant formula (FDA). It's also in human breast milk (Kirk et al 2007; Pearce et al 2007).

Common treatment technologies in widespread use for other contaminants also are effective at removing perchlorate from drinking water. For example, ion exchange technology is able to treat perchlorate contamination to levels considerably below 1 ppb.

Perchlorate is such a big health concern, even at low levels and for short-term exposures, because it blocks normal thyroid hormone production. This leads to low thyroid hormone, which if it is too low, and occurs during early life development will lead to developmental delays and low IQ. We don't have enough data right now to know whether or not there may be a "safe" level of perchlorate that wouldn't be associated with harm, but many science experts suspect that there isn't one. For example, in 2008 University of Massachusetts Amherst Professors Carol Bigelow and Tom Zoeller, wrote in comments to EPA that, "... small differences in available thyroid hormone (and the iodine associated with it) during the first few weeks of life can have significant lifetime consequences" (Bigelow et al 2008).

A 2010 analysis by California state researchers reported that babies born in areas with perchlorate-contaminated tap water above 5 ppb had a 50% chance of having a measurable decline in thyroid function (Steinmaus et al 2010). The science isn't clear on whether this level of decline would necessarily lead to IQ deficits, but consumers would not willingly take such a risk with their children.

California's decision to set its public health goal for perchlorate at 1 ppb should push EPA to move ahead with a national enforceable drinking water standard that is no higher than 1 ppb.

About the Authors

Jennifer Sass

Senior Scientist, Federal Toxics, Health and Food, Healthy People & Thriving Communities Program

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