This story was updated at 1:58 p.m. EDT.
A federal appeals court on Tuesday faulted EPA for failing to set drinking water limits for a chemical commonly used in explosives and rocket fuel.
Three judges of the U.S. Court of Appeals for the District of Columbia Circuit sided with environmental groups that had challenged EPA’s continuation of a Trump-era decision not to set Safe Drinking Water Act regulations for perchlorate — years after the agency had determined that rules were needed.
“Because the Safe Drinking Water Act requires that the agency ‘shall’ regulate after making a regulatory determination, EPA lacks authority to withdraw that determination and decide that it ‘shall not’ regulate,” wrote Senior Judge David Sentelle, a Reagan appointee, in the court’s majority opinion.
Perchlorate has been the subject of fraught back-and-forth for years. The compound has been a notorious contaminant near military sites and contractor facilities, entering groundwater and at times jeopardizing drinking water. It can interfere with the thyroid gland and hormone production, making it a notable public health risk, particularly for pregnant people and infants.
Perchlorate cropped up in wells during the 1990s, sparking a major public push for federal action, with EPA stating in 2008 that it would not regulate the compound. Later, under the Obama administration, EPA determined in 2011 that perchlorate met the criteria under the Safe Drinking Water Act, or SDWA, for regulation. But the agency failed to follow through on that determination, sparking litigation from the Natural Resources Defense Council in 2016.
A settlement agreement gave EPA until 2018 to propose a standard, but regulators asked for an extension.
Then, under former President Donald Trump, the agency revoked the 2011 determination, arguing that monitoring requirements for perchlorate would be too intensive and states were already addressing the problem.
Advocates were hopeful that the Biden administration might offer a new outlook.
But EPA announced last year that it would continue the Trump-era approach, arguing that a review of the former administration’s process had found that the conclusion was based on the best available science. In particular, regulators argued that perchlorate contamination was not widely spread out enough throughout the country to merit that level of response under SDWA.
At that time, EPA had not moved on its own initiative to regulate a drinking water contaminant since the statute was amended in 1996. This past spring, the agency countered that narrative with a move to crack down on six PFAS — per- and polyfluoroalkyl substances — in a notable shift from its typical approach to pollutants in drinking water systems.
NRDC has been angling to make perchlorate one of the next contaminants to face regulator scrutiny while pushing forward with its long-running litigation. The decision Tuesday brings the group closer to that goal, although how EPA will proceed is unclear.
“We think it’s a very important decision,” said Erik Olson, senior strategic director for health at NRDC, of the D.C. Circuit’s ruling. “The court made it clear that EPA has to regulate toxic perchlorate that is occurring in millions of people’s drinking water because the agency had found it posed a health risk.”
Reached via email, EPA said it is reviewing the court decision but offered no further reaction regarding the news. Attorneys for the American Water Works Association, which intervened in the litigation on the agency’s behalf, did not respond to a request for comment.
During oral argument in January, the D.C. Circuit panel asked why EPA had not invoked the Chevron doctrine — which gives agencies legal leeway to interpret ambiguous statutes — to defend its decision not to regulate perchlorate in drinking water.
While the D.C. Circuit still uses Chevron to uphold federal rules, the doctrine has fallen out of favor at the conservative-dominated Supreme Court, which last week signaled that it may be ready to do away with the agency deference standard.
In a concurring opinion in the perchlorate case, Judge Florence Pan wrote that the D.C. Circuit might have considered deferring to EPA’s decision if the agency had raised a Chevron claim that SDWA remained ambiguous about whether the agency can change course on a regulatory determination.
“But because the EPA did not cite Chevron in its brief and avoided relying on it at oral argument,” she wrote, “I decline to consider the applicability of Chevron here.”
Pan, a Biden appointee, wrote that she believes EPA is able to withdraw a decision to regulate if it can show that the move is based on changes in the best available, peer-reviewed science. In the perchlorate case, however, she wrote that EPA had relied on “selectively updated data” on the prevalence of the chemical in drinking water to support its decision not to regulate.
Senior Judge David Tatel, a Clinton pick, also joined the majority opinion.