Sen. Shelley Moore Capito (R-W.V.) in a letter to the White House on Wednesday said the Biden administration has frozen a “significant” action on perfluoroalkyl and polyfluoroalkyl substances (PFAS) drinking water standards with a recent executive order and asked the administration to “promptly” publish the rule in question.

In the letter to White House chief of staff Ron Klain, Capito said Klain’s Jan. 20 memo, which froze all new or pending rules until the administration can review them, affected the PFAS rule.

“I have long taken a lead role in bipartisan efforts to address PFAS, and of significant importance to me is the timely action of EPA [the Environmental Protection Agency] to promulgate a National Primary Drinking Water Regulation under the Safe Drinking Water Act,” Capito, the ranking member of the Senate Environment and Public Works Committee, wrote in the letter Wednesday.

The letter notes that the EPA finalized a determination to regulate two PFAS substances, perfluorooctanesulfonic acid and perfluorooctanoic acid under the Safe Drinking Water Act on Jan. 15.

“This final regulatory determination was a vital step toward ensuring the protection of public health across the nation, as well as to my constituents specifically. It still has not been published in the Federal Register,” Capito wrote.

The West Virginia senator is a vocal advocate for the introduction of a maximum contaminant level for PFAS in drinking water. In the Feb. 3 confirmation hearing for Michael Regan, Biden’s nominee for EPA administrator, Capito brought up PFAS after Sen. Kirsten Gillibrand (D-N.Y.) did the same, saying she was “like-minded with her in terms of the restlessness of getting there and the delay” in implementing a PFAS drinking water standard.

“I would impress upon you how important I think that is to our nation and to our nation’s [youth], as they are living through the impacts of what this could have on drinking water,” she said. “So I would just ask a pledge to keep working with me and us on that.”

“Absolutely,” Regan replied.