EPA’s Plan To Regulate Perchlorate In Drinking Water

In April 2022, the United States Environmental Protection Agency (EPA) announced its final plan for regulation of perchlorate in drinking water. The plan formalizes the agency’s withdrawal of its 2011 decision to promulgate a Maximum Contaminant Level (MCL) for perchlorate, and announces actions that will be taken to minimize perchlorate impacts in the future.

What is Perchlorate

Perchlorate (ClO4) is a compound most commonly used in solid rocket propellants, munitions, fireworks, airbag initiators, matches, signal flares, and some electroplating operations. Ninety percent of U.S. usage of perchlorate is in the defense and aerospace industries as ammonium perchlorate. It can also form in sodium hypochlorite, used as a disinfectant, under certain storage conditions. Perchlorate is highly soluble and chemically stable in groundwater. Consequently, plumes of perchlorate in groundwater can be extensive, reaching miles in length. Perchlorate’s primary pathways for human exposure are ingestion of contaminated food and drinking water, and its primary health impacts are on the thyroid.

Environmental Occurrence

EPA collected data between 2001 and 2005 on the occurrence of perchlorate in drinking water systems – concluding that between five million and 16 million people might be exposed to perchlorate in drinking water.

From 1997 to 2009, the Department of Defense (DOD) reported detecting perchlorate at 70% of the DOD  installations sampled. As of 2010, perchlorate had been detected at 40 National Priority List (NPL; Superfund) sites.

Regulatory Background

In the 2000’s, EPA had established an Interim Drinking Water Health Advisory for perchlorate of 15 micrograms per liter (µg/l) and a Preliminary Remediation Goal for NPL sites also of 15 µg/l. In 2011 EPA determined that perchlorate met the criteria for regulation under the Safe Drinking Water Act (SDWA), based on the occurrence data cited above, and began the process of promulgating an MCL.

In 2016, California and Massachusetts established enforceable drinking water standards of 6 µg/l and 2 µg/l, respectively, for perchlorate. Approximately 18 other states have established drinking water screening levels for perchlorate ranging from 0.8 µg/l to 25.6 µg/l. Some states have also adopted screening levels for soil.

In 2019, EPA completed an updated occurrence analysis that concluded that exposures to perchlorate in drinking water were significantly reduced as compared to the 2001-2005 data. The updated study suggested that only 0.03% of public water systems would have perchlorate present at concentrations of 18 µg/l or more. It also concluded that creating an MCL for perchlorate would require more than 60,000 public water systems to monitor for perchlorate. The reduction in perchlorate occurrence in drinking water since the initial study was attributed to the passage of drinking water standards in California (which had over half of the perchlorate detections in the 2001-2005 analysis) and Massachusetts; active remediation of perchlorate contamination at several sites in the Colorado River basin; DOD and NPL cleanups of perchlorate-contaminated sites; and adoption of best management practices for perchlorate.

Recent Actions

In 2020, EPA made a final determination that it would not create an MCL for perchlorate in drinking water, and withdrew the 2011 regulatory action. That determination was then subjected to peer review, which was completed in March 2022 and confirmed EPA’s decision. In announcing the results of the peer review, EPA also publicized its intention to pursue “multiple integrated    actions to address perchlorate in the Nation’s waters”, including:

  • Continue ongoing cleanups at perchlorate-contaminated sites.
  • Propose revisions to RCRA standards for open burning of waste explosives and propellants.
  • Strengthen labeling requirements for hypochlorite solutions to include storage and handling information to minimize perchlorate formation.
  • Provide resources and recommendations for water systems to address perchlorate contamination.

EPA also plans to perform studies to characterize perchlorate occurrence in natural waters (prior studies have focused on potable water supplies), especially after fireworks events, and to develop a web-based toolkit for perchlorate.

Regulatory Support…from HETI.

HETI’s staff continually reviews new and proposed changes to regulations and standards to make sure we have current knowledge of compliance and environmental issues. We have extensive experience in supporting our clients through a comprehensive range of regulatory support and other services. Whether it’s perchlorate or other contaminant issues, HETI is here to help.