08/29/2025

EPA Strips ‘Affirmative Defense’ from Polyether Polyols Air Toxics Rule

Inside EPA | Stuart Parker | August 28, 2025

EPA Strips ‘Affirmative Defense’ from Polyether Polyols Air Toxics Rule

EPA is stripping “affirmative defense” provisions from its air toxics regulation governing polyether polyols (PEPO) manufacturers, as part of an ongoing effort to remove the measures that provide a shield from civil liability for industry in the event of malfunctions, after courts found such provisions unlawful.

In a rule signed Aug. 27 by Administrator Lee Zeldin ahead of its upcoming publication in the Federal Register, EPA removes the affirmative defense from the national emission standard for the hazardous air pollutants (NESHAP) for the PEPO sector, which produces products used in polyurethane and foam.

“EPA is finalizing the removal of affirmative defense provisions associated with the violation of air emission standards due to malfunctions,” the agency says. EPA is under a consent decree agreement to finalize the rule by Sept. 10, and EPA says 24 plants are affected by the change.

The agency continues to remove affirmative defenses from air rules after key decisions from the U.S. Court of Appeals for the District of Columbia Circuit on affirmative defenses and wider exemptions for emissions during periods of plant startup, shutdown and malfunction (SSM).

A 2008 ruling in Sierra Club v. EPA found generally that emissions limits in air toxics rules must apply at all times, and that automatic exemptions for periods of SSM are unlawful. A 2014 ruling in Natural Resources Defense Council (NRDC) v. EPA then found affirmative defenses unlawful because they usurp courts’ ability to fashion equitable remedies to Clean Air Act (CAA) violations.

In its 2024 finding in Environmental Committee of the Florida Electric Power Coordinating Group v. EPA the court faulted the Obama EPA’s decision to strip affirmative defense provisions from state implementation plans (SIPs) for meeting federal air quality standards.

The resulting ruling largely reversed EPA’s 2015 “SIP Call” rule removing SSM exemptions from SIPs. But the court reached a mixed conclusion in the context of SIPs that while “complete” affirmative defenses are acceptable in state plans, partial defenses that only shield industry from penalties are incompatible with the NRDC precedent.

EPA nonetheless continues to remove affirmative defenses from NESHAP rules, which are governed by a different air law section than SIPs.

The affirmative defense provisions in the NESHAP “imply legal authority that the D.C. Circuit has stated the EPA does not have,” EPA says in the new rule.

“Since the NRDC decision, the EPA has been removing affirmative defense provisions from CAA section 112 rules, as well as from section 111 (New Source Performance Standards) and section 129 (Solid Waste Combustion) rules,” EPA says.

“As indicated in the previous actions removing affirmative defense provisions and in the proposed rulemaking, the EPA will continue to evaluate possible violations on a case-by-case basis and determine whether an enforcement action is appropriate,” the agency says.

“If the EPA determines that bringing an enforcement action under CAA section 113(d)(2)(B) against a source for a violation of an emission standard is warranted, the source can raise all defenses available under the law, and the Federal district court will determine what, if any, relief is appropriate,” the agency adds.

EPA Proposal

EPA in June 2024 proposed to remove the affirmative defense from the PEPO NESHAP and 17 other rules. “This final action removes affirmative defense provisions only from the PEPO NESHAP and does not take final action on any of the other regulatory changes set out in the proposal,” EPA says.

Meanwhile, the Trump EPA has not yet acted on a December 27 Biden-era proposal to tighten ethylene oxide (EtO) emissions limits for the sector. The plan, sought by environmentalists, would tighten the limits in line with a 2016 assessment by the agency’s integrated risk information system (IRIS) that found health risks from the solvent far higher than previously thought.

But the Trump administration appears very unlikely to finalize the rule as proposed, and Republican lawmakers and industry groups are in general strongly opposed to IRIS, which they argue has exaggerated health risks of EtO and other chemicals.

Also, EPA has elected to proceed with D.C. Circuit litigation brought by industry against a Biden-era rule that strips affirmative defenses from air permits, in SSM Litigation Group v. EPA, rather than reconsidering the rule and asking the court for abeyance.

A panel of Judges Neomi Rao, Justin Walker, both Trump appointees, and Senior Judge Douglas Ginsberg, appointed by President Ronald Reagan, heard arguments in the case Jan. 14, prior to the transition to the Trump administration, with EPA defending the rule. While some judges doubted industry’s standing to sue, if the court reaches the merits, the panel appears inclined to side with industry and vacate the rule.