Perchlorate in review

April 1, 2015

Another look at this controversial contaminant.

According to an article published by the San Bernardino Sun in late February, a California state agency lowered the Public Health Goal for perchlorate from 6 parts per billion (ppb) to 1 ppb. This controversial water contaminant is worth another review. Perchlorate (ClO4) is both a natural product and a synthetic chemical with numerous uses, including in rocket fuel and fireworks. Perchloric acid (HClO4) forms salts, such as potassium perchlorate (KClO4), ammonium perchlorate (NH4ClO4) and sodium perchlorate (NaClO4).

In water, perchlorate is highly mobile. It is also durable and can persist for many decades under typical groundwater conditions. It was also analyzed as part of the Unregulated Contaminant Monitoring Rule 1 (UCMR 1) program, where it was found at above 4 ppb in just over four percent of public water systems in the U.S.

ANSI/NSF Standard 58 requires a reverse osmosis (RO) unit to be able to reduce water containing 130 ppb of perchlorate to 4 ppb or less. Additional industry standards for other devices are under consideration. In addition to RO, anion exchange and carbon adsorption will reduce perchlorate to some extent.

Regulatory considerations

In 2008, EPA had proposed not to regulate perchlorate in drinking water and issued an interim Drinking Water Health Advisory (DWHA) of 15 ppb based upon a review, recommended assessment and reference dose provided by the National Research Council (NRC). EPA reversed that decision in 2011. At that time, the agency issued a determination to regulate perchlorate with a different interpretation of the requirements in the Safe Drinking Water Act (SDWA) that should have been met and a decision reached by 2013, but has since been delayed. State MCLs range across the country, such as California’s MCL is 6 ppb and Massachusetts’ is 2 ppb. The WHO/FAO Joint Expert Committee on Food Additives (JECFA) concluded that environmental exposures to perchlorate were not a health concern.

A Regulatory Determination requires that: The contaminant may have an adverse effect on public health; it occurs in public water systems with a frequency and at levels of public health concern; and in the judgment of the administrator regulation presents a meaningful opportunity for health-risk reduction. What concentration will EPA propose for regulation? Will it be supportable by cost- and risk-benefit analysis, and will it be challenged?

In previous Water Technology issues and in WaterTech e-News Daily, we have been covering this contaminant which is currently being heavily debated. Visit for an in-depth look and update of perchlorate.

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