April 15, 2026

EPA Proposes Second NESHAP Risk Reviews Violate CAA

On March 17, 2026, EPA proposed to rescind its 2024 final rule on the residual risk and technology review (RTR) for the commercial sterilization facilities NESHAP. [91 FR 12700] The 2024 rule revamped Part 63, Subpart O by broadening applicability, adding continuous emissions monitoring requirements for most facilities, and regulating more sources. [89 FR 24090] Those provisions would have resulted in reduced ethylene oxide (EtO) emissions by 21 tons per year at commercial sterilizers, facilities that support medical device manufacturers, hospitals, the food industry, pharmaceutical manufacturers, and more. Now, EPA claims it overstepped its statutory authority in that rule and is proposing to roll back many of the 2024 provisions by predominantly:

Rescinding risk-based standards,
Revising the standard for new aeration room vents that resulted from the technology review,
Revising the compliance demonstration requirements, and
Rescinding a requirement for permanent total enclosure.

EPA’s arguments on its claimed statutory overreach

The agency’s underlying claim is that the 2024 final rule constituted a second risk review, whereas the CAA allows only a single risk review of a NESHAP. CAA Sections 112(d)(6) and 112(f)(2) [42 U.S.C. Sections 7412(d)(6) and 7412(f)(2)] when read together, form the basis of NESHAP RTRs. These provisions require EPA to revise as necessary emission standards based on new developments in “practices, processes, and control technologies” and “to provide an ample margin of safety to protect public health.” The crux is that while Section 112(d)(6) states the technology review shall be performed “no less often than every 8 years,” indicating multiple technology reviews are required, Section 112(f)(2) only states the risk review is to be conducted “within 8 years after promulgation of” a source category standard, and does not explicitly say the risk review is to be repeatedly conducted.

EPA lays out its arguments further at 91 FR 12712–13, yet as stated in the 2024 proposal, Section 112(f)(2) “does not limit our discretion or authority to conduct another risk review should we consider that such review is warranted.” [89 FR 24094] Furthermore, CAA Section 112(d)(4) [42 U.S.C. Section 7412(d)(4)] provides additional language on the use of health (i.e., risk) thresholds and creating an ample margin of safety when establishing emission standards.

If this EtO NESHAP proposal is finalized, other rules such as the miscellaneous organic chemical manufacturing NESHAP (Part 63, Subpart FFFF) and the polyether polyols production NESHAP (Part 63, Subpart PPP), which have also recently received additional risk reviews, will undoubtedly see similar recissions. See CAA Section 112 Risk and Technology Reviews: Statutory Authority and Methodology for more on the development of EPA’s RTR approach. Comments on the proposal may be submitted through May 15, 2026 via Docket ID No. EPA-HQ-OAR-2019-0178. [91 FR 23382]

Publisher’s note: We acknowledge EPA is correct that CAA Section 112(f)(6) was a one-time risk review—but it is unrelated to the periodic reviews required by CAA Section 112(d)(6). In fact, the CAA Section 112(f)(6) review was designed to make sure risk was being properly considered when setting standards by forcing EPA to act if Congress didn’t, but this is now history. EPA is explicitly allowed to consider health effects when setting standards and reviewing them under CAA Section 112(d)(6) by CAA Section 112(d)(4), so we do not believe the agency’s argument will survive court challenges.

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