EPA’s Regulation of Perchlorate in Drinking Water, Someday.
The U.S. Court of Appeals for the District of Columbia ended the U.S. Environmental Protection Agency’s (EPA) decades of waffling on perchlorate regulation when it decided on May 9, 2023 that EPA must set a Maximum Contaminant Level (MCL) for the contaminant perchlorate in drinking water. The court found that EPA exceeded its statutory authority in 2020 when it withdrew its Regulatory Determination from 2011 to regulate perchlorate under the Safe Drinking Water Act (SDWA). A concurring judge reasoned that "EPA's 2020 decision not to regulate perchlorate was arbitrary, capricious, and contrary to law because it was based on a MCLG that did not comply with a statutory directive, and relied on selectively updated data concerning the prevalence of perchlorate in drinking water."
Perchlorate is a highly soluble compound widely used in rocket propellants, munitions, signal flares, blasting materials and fireworks. Due to perchlorate’s solubility, the contaminant groundwater plumes are often extensive. Early 2000s studies requested by environmental agencies showed that perchlorate ingestion could cause health problems. In December 2008, EPA issued an Interim Drinking Water Health advisory for perchlorate of 15 ug/L (micrograms per Liter or 15 parts per billion). Although not an enforceable regulation, advisory levels provide technical guidance on contaminant concentrations at which adverse health effects are not expected to occur over a certain exposure duration.
Instead of waiting on the EPA, California and Massachusetts set enforceable drinking water levels of perchlorate at 6 ug/L, and 2ug/L, respectively. Like many other states, Indiana does not have enforceable perchlorate drinking water quality standards. For environmental remediation sites, the Indiana Department of Environmental Management has published a drinking water/residential groundwater cleanup goal of 15 ug/L. In its perchlorate technical fact sheet, EPA summarizes states with different cleanup goals and lists perchlorate health standards and studies.
While most states waited to see what would become of perchlorate under the federal SDWA, EPA’s long up and down perchlorate regulatory process was informed by more studies, public comments, EPA’s responses to those public comments, then more studies. The regulatory process included many delays, missed deadlines and litigation compelling EPA to act. With the court’s recent decision, the perchlorate regulatory work is now remanded back to EPA and we are waiting to see what next steps the agency will take to comply with the ruling.
In the meantime, the court’s decision may also inform EPA’s continued process for regulating certain per- and polyfluoroalkyl substances (PFAS) under the SDWA. In March 2023, EPA proposed drinking water MCLs at 4 parts per trillion (nanograms/Liter) for these persistent compounds found in many consumer products including nonstick/grease resistant items, stain and water repellant fabrics, and fire fighting foams. EPA is currently reviewing the public comments on the proposal to limit PFAS in drinking water, and unlike the conflicted perchlorate process, anticipates a direct route to finalizing the PFAS rule by the end of 2023.
The author thanks Summer Legal Clerk Audrey Crites for her helpful research and drafting assistance.