Six Air-Rule Signals in Ten Weeks: What EPA's Q2 2026 Deregulatory Cycle Means for Manufacturing Compliance

If you lead EHS for a manufacturer, power producer, or oil and gas operator, the second quarter of 2026 has been a regulatory ten-week sprint. EPA has moved on at least six distinct air-rule fronts since early February — final repeals, proposed rescissions, and narrow technical amendments each running on their own timeline. Underneath them sits the larger schedule EPA announced on March 12, 2025: 31 planned deregulatory actions, eight sector NESHAPs in reconsideration, and a proposed 2-year compliance exemption under CAA section 112(i)(4) for facilities caught mid-cycle.

Rules that had been stable for a decade are now a rule set in motion. The compliance question is no longer “are we covered?” but “what applies today, what will apply in six months, and what should we document about our choice either way?”

Here is the Q2 2026 digest — six signals, what each one does, and what EHS leaders should do about it before Q3 opens.

Signal 1: Rescission of the GHG Endangerment Finding (Final — February 12, 2026)

On February 12, 2026, EPA finalized the rescission of the 2009 Greenhouse Gas Endangerment Finding along with the associated motor vehicle GHG emission standards under the Clean Air Act. The endangerment finding was the legal prerequisite for regulating greenhouse gases from new motor vehicles and engines under CAA section 202.

What it changes: Federal motor vehicle GHG standards under section 202 lose their statutory foundation. The rescission is prospective.

What it does not change: California’s authority under CAA section 177 to set its own motor vehicle standards is unaffected. States that follow California’s standards (under section 177) can continue to do so. Industrial stationary source GHG regulations under other CAA sections (Title V, NSPS, NESHAP for specific pollutants) are on separate legal tracks.

Action for EHS leaders: If your fleet planning assumed federal GHG standards as the baseline, reconfirm which state standards your fleet operates under. A vehicle registered for use in California or one of the Clean Cars states operates under a different standard than the same vehicle used in a section-177-nonadopting state.

Signal 2: MATS NESHAP Coal & Oil EGU Repeal (Final — Effective April 27, 2026)

The Mercury and Air Toxics Standards (MATS) for Coal- and Oil-Fired Electric Utility Steam Generating Units were the subject of a final repeal published at 91 FR 03638 on February 24, 2026. The repeal takes effect on April 27, 2026 — the Monday after this article publishes.

What it changes: The federally required emissions limits for mercury, HCl, non-mercury HAPs, and other MATS pollutants from coal- and oil-fired EGUs no longer apply under 40 CFR 63 Subpart UUUUU from the effective date forward.

What it does not change: Historical MATS violations incurred before April 27, 2026 remain enforceable under the Clean Air Act. Repeal is prospective, not retroactive. State-level enforcement authority in states that have adopted MATS-aligned standards into their SIPs continues independently. Judicial review petitions under CAA section 307(b)(1) must be filed in the U.S. Court of Appeals within 60 days — the D.C. Circuit is likely to see multiple challenges by late June 2026.

Action for EGU operators: Document the operational decisions you make based on the repeal. Facilities that choose to remove control equipment should document the repeal reliance; facilities that retain equipment should document that choice as a risk mitigation decision. The two-scenario plan — repeal holds vs. repeal is vacated on judicial review — should be the working framework.

Signal 3: EtO Commercial Sterilization NESHAP Reconsideration (Proposed — Comments Due May 1, 2026)

The Ethylene Oxide Commercial Sterilization Facilities NESHAP proposed reconsideration was published at 91 FR 12700 on March 17, 2026. The proposal reopens the 2024 Final Rule’s Residual Risk and Technology Review.

What it proposes:

Rescind the risk-based standards promulgated under CAA section 112(f)(2)
Revise the standard for new aeration room vents (ARVs) at facilities using at least 10 tpy of EtO
Amend compliance demonstration requirements to allow facilities to choose between parametric monitoring and CEMS
Rescind the requirement that permanent total enclosure (PTE) be used to ensure complete EtO capture

What it does not change: The underlying NESHAP remains in effect during reconsideration. Commercial sterilizers already operating under the 2024 Final Rule must continue compliance until any final revision is published.

Action for commercial sterilizers and their downstream medical device customers: A virtual public hearing was held April 1, 2026. Written comments close May 1, 2026. Operators with specific concerns on parametric monitoring-versus-CEMS flexibility, on PTE requirements for existing facilities, or on the 10 tpy threshold for new ARVs have a short window to comment through docket EPA-HQ-OAR.

Signal 4: NSPS OOOOb/EG OOOOc Narrow Technical Amendments (Final — Signed April 4, 2026)

EPA Administrator Lee Zeldin signed a final rule on April 4, 2026 revising two narrow technical aspects of the 2024 NSPS OOOOb and EG OOOOc for oil and natural gas operations:

Revised temporary flaring provisions for associated gas in certain situations
Revised requirements for continuous monitoring of the net heating value (NHV) of vent gas from flares and enclosed combustion devices, and alternative performance test options

EPA estimates the action saves the oil and natural gas industry $2.5 billion from 2024 through 2038 (3% discount rate), equivalent to $208 million per year.

What it does not change: The broader OOOOb/c compliance framework remains in place. The extended compliance deadline of January 22, 2027 for most OOOOb/c provisions, the November 30, 2026 annual reporting deadline, and the 98% waste gas capture requirement for new oil wells by end of 2026 all continue to apply. See the EPA Oil & Gas NESHAP Technology Review 2026 post for the broader framework.

Action for oil and gas operators: The April 4 amendments narrow two specific compliance paths. Operators who had planned around strict CEMS-only net heating value monitoring may now have alternative performance test options. Operators relying on temporary flaring of associated gas in specific scenarios should review the revised provisions before finalizing capital investment in gas capture infrastructure.

Signal 5: Oil & Gas NESHAP Proposed Rule (Proposed — Comments Due June 22, 2026)

Separately from the NSPS OOOOb/c action, EPA published in April 2026 a proposed rule on the NESHAP for Crude Oil and Natural Gas Production Facilities and Natural Gas Transmission and Storage Facilities (40 CFR 63 Subparts HH and HHH).

What it proposes: Largely retain existing standards with limited updates — adding methanol as a regulated pollutant, clarifying the scope of major source definitions, and providing alternative approaches for previously unregulated emissions points.

What it does not change: The underlying HAP and VOC standards for glycol dehydrators, storage vessels, and equipment leaks continue to apply during the rulemaking.

Action for oil and gas operators: Comment period closes June 22, 2026. Operators with concerns about the methanol addition, major source definition clarification, or the alternative approaches for previously unregulated emissions points should comment through docket EPA-HQ-OAR.

Signal 6: Missouri SIP Actions (Federal Register — April 23, 2026)

Two Missouri state implementation plan actions published in the same Federal Register edition as this article. Both are state-specific, neither depends on federal deregulation, and both illustrate the point that state SIPs do not wait for federal direction.

10 CSR 10-6.060 Construction Permits Required (final EPA approval). Missouri’s revised air construction permit fee schedule — effective January 1, 2026 at the state level — is now federally approved and takes effect at the federal level on May 26, 2026. Major NSR, PSD, and HAP permits in Missouri now carry a $6,000 filing fee plus $100-per-hour processing. See the Missouri Air Construction Permit Fee Schedule 2026 post for the full fee table.

10 CSR 10-5.220 Petroleum Liquid Storage, Loading and Transfer (proposed approval). Missouri’s revision to the St. Louis-area petroleum vapor recovery rule aligns the rule with the Kansas City analog (10 CSR 10-2.260). Small-tank applicability threshold moves from 500 gallons to 550 gallons. VR system modifications at gasoline dispensing facilities no longer require a construction permit — a streamlined procedural process replaces it. Comment period closes May 26, 2026. See the St. Louis Petroleum Vapor Recovery SIP Alignment with Kansas City post for the operator’s compliance map.

Action for Missouri-area operators: Both Missouri actions have May 26, 2026 deadlines. Capital project teams planning 2026 or 2027 air construction permits need to budget the new fee schedule. Petroleum operators in St. Louis should reconfirm applicability at the 550-gallon threshold and adopt the streamlined VR modification process where applicable.

The Eight Sector NESHAPs Still in Reconsideration

Beneath the six signals is the longer reconsideration schedule. EPA’s March 12, 2025 announcement identified eight sector NESHAPs for reconsideration:

Integrated iron and steel manufacturing
Rubber tire manufacturing
Synthetic organic chemical manufacturing industry (the HON rule)
Commercial sterilizers for medical devices and spices
Lime manufacturing
Coke ovens
Copper smelting
Taconite ore processing

Several of these have already seen interim final rules extending compliance deadlines. The Integrated Iron and Steel NESHAP compliance deadline was pushed to April 3, 2027 by a July 3, 2025 interim final rule. A partial administrative stay of the iron and steel NESHAP technology review was published March 31, 2025.

The 2-year compliance exemption under CAA section 112(i)(4) is under consideration for affected facilities while the rulemakings proceed. The exemption is not automatic. Operators in affected sectors should monitor the specific NESHAP reconsideration docket for their sector and evaluate whether a 112(i)(4) petition is warranted.

Reconsideration Is Not Rescission

One distinction is worth being specific about because it is easy to miss in a compliance update memo: reconsideration is not rescission. A rule under reconsideration remains in effect and enforceable until the reconsideration rulemaking produces a final rescission or revision. The iron and steel NESHAP, the HON rule, and the commercial sterilizer NESHAP are all still enforceable today — the reconsideration just means EPA is re-examining them.

That means operators in reconsidered sectors have to continue complying with the existing NESHAP. A compliance exemption under 112(i)(4), if granted, would provide a formal mechanism to delay certain compliance obligations — but the exemption requires an active petition and EPA determination. It is not self-executing.

The State SIP Framework Does Not Flow Automatically from Federal Deregulation

A mistake EHS leaders make in a deregulatory cycle is assuming that federal repeal flows through automatically to state implementation plans. It does not.

California maintains Advanced Clean Cars II and a suite of stationary-source air rules independent of federal direction. Colorado Regulation 7 (oil and gas ozone precursors) is not tied to NSPS OOOOb/c. New Mexico 20.2.50 NMAC operates independently. Northeast Ozone Transport Commission states coordinate regionally on air-quality standards that may retain MATS-aligned controls on coal units regardless of federal repeal.

Missouri’s April 23, 2026 SIP actions are state-specific and move on state timelines regardless of federal deregulatory direction. Kansas, Oklahoma, Texas, and Nebraska each maintain their own SIPs.

For a multi-state operator, the correct compliance question after each federal action is: “Does this repeal flow through to every state where we operate, or does a more stringent state rule remain in force?” The answer is usually a mix.

The Seven Questions to Run Against Each Signal

For each of the six signals — and each of the eight sector NESHAPs in reconsideration — EHS teams should run the same seven-question loop:

Does this rule still apply to our facility?
What is the current compliance deadline of record (accounting for any interim final rule extensions)?
Is a CAA section 112(i)(4) compliance exemption a credible path?
Are there open comment windows we should participate in?
Does the federal action flow through to every state where we operate, or is a state SIP retaining the rule?
What is our documentation of the compliance choice — repeal reliance, control retention, exemption petition?
What does the two-scenario plan look like if the rule is vacated or remanded on judicial review?

A compliance binder with answers to those seven questions for each rule is the audit-defensible artifact that holds up across the cycle.

When iSi Steps In

iSi supports manufacturers, power producers, and oil and gas operators through exactly this kind of regulatory cycle — applicability reverification, compliance deadline tracking across federal and state programs, comment preparation on proposed rules, and the compliance documentation that holds up when a rule is vacated a year later. If your EHS team is managing across multiple sectors in the March 2025 announcement or coordinating state SIP exposure alongside federal actions, the next step is a 60-minute applicability and documentation review.