Sens. Tom Carper, D-Delaware, and Edward J. Markey, D-Massachusetts, led a March 14 letter urging Environmental Protection Agency Administrator Scott Pruitt to reinstate the longstanding policy requiring the nation’s major sources of hazardous air pollution to maintain maximum achievable control technology throughout the lifetime of their operation, known as “once-in-always-in.”

The agency abruptly reversed the policy in January without fully considering the potentially devastating health effects of such a policy change.

For 23 years, the “once in, always in” policy has served as a critical backstop to ensure air toxic reductions from the country’s largest and dirtiest sources are permanent. The air toxics MACT program with the “once in, always in” policy has resulted in the elimination of 1.7 million tons of hazardous air pollution, according to a 2017 EPA fact sheet.

However, on Jan. 25, EPA’s Office of Air and Radiation, headed by Assistant Administrator Bill Wehrum, issued new guidance that revoked the “once in, always in” policy for major sources, based on a purported ‘plain language reading’ that the lawmakers noted “…is inaccurate, ignores the broader statutory framework and likely to lead to absurd results.”

“Revoking the ‘once in, always in’ policy will lead to greater levels of arsenic, lead, mercury and almost two hundred other air toxic pollutants in communities around the United States. The policy’s revocation is not based on sound legal reasoning. We therefore request that you reinstate the ‘once in, always in’ policy at least until EPA has performed, and received public comment on, a thorough analysis of the expected increases in air toxic pollution and its corresponding impacts on human health. In a recent hearing before the Senate Environment and Public Works Committee, you acknowledged the agency failed to do such analysis before making its ill-advised decision,” the senators wrote.

During the George W. Bush administration, then-Acting Administrator Wehrum attempted to withdraw the “once in, always in” policy through the rulemaking process, but without any analysis. At the time, regional EPA officials were so concerned about the policy change that they stated the agency should not do so without looking “closely at this issue to determine whether the likely benefits would be greater than the potential environmental costs.”

However, during his appearance before the EPW Committee on Jan. 30, Pruitt admitted that EPW did not closely review — or potentially consider at all — the potential health effects of this policy change. When asked by Carper if EPA did any analysis of the health or environmental effects before deciding to withdraw the “once in, always in” policy through a written memo, Pruitt replied that the decision was made by the policy office and not by EPA’s air program.

“We believe that it is EPA’s responsibility to provide clear, consistent regulations with the goal of protecting our communities. Withdrawing the longstanding ‘once in, always in’ policy fails this responsibility,” the senators wrote.

The lawmakers have asked Pruitt to respond to their questions by April 9.

The text of the letter is available at