A cluster of US Environmental Protection Agency (EPA) regulatory actions published in mid-April 2026, together with the approaching transposition deadline for the EU's recast Ambient Air Quality Directive, confronts compliance officers and regulatory affairs teams with a complex, fast-moving air-quality landscape. This analysis maps the three EPA actions against the EU trajectory and highlights the emerging risks.
MATS Repeal Correction: Reverting to 2012 Standards for Power Plants
On 16 April 2026, the EPA published a correction to its February 2026 final rule repealing the 2024 amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for coal- and oil-fired electric utility steam generating units-commonly known as the Mercury and Air Toxics Standards (MATS). The repeal, originally published in the Federal Register at 91 FR 9088 on 24 February 2026, rolled back the Biden-era 2024 strengthening of mercury, non-mercury metallic HAP, and acid gas limits, reinstating the original 2012 MATS standards. 1National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units: Final Repeal; Correction
The April correction addresses technical errors in the February rule text but does not alter the substance of the repeal. A coalition of nonprofit organizations and a separate coalition of states have already petitioned for judicial review of the repeal in the D.C. Circuit. 2Mercury and Air Toxics Standards - Environmental and Energy Law Program For operators of coal- and oil-fired electric generating units (EGUs), the practical effect is a return to less stringent emission limits for mercury and other hazardous air pollutants. However, given pending litigation, compliance teams should consider maintaining monitoring infrastructure and documentation systems capable of supporting both the 2012 and 2024 standard sets until the legal uncertainty resolves.
New LDAR Obligations for Chemical Manufacturing Area Sources
In a contrasting move that tightens rather than loosens standards, the EPA on 1 April 2026 finalized amendments to the Chemical Manufacturing Area Sources (CMAS) NESHAP under 40 CFR Part 63, Subpart VVVVVV. The final rule introduces new leak detection and repair (LDAR) requirements for equipment leaks and heat exchange systems handling organic hazardous air pollutants at chemical manufacturing area sources-the most significant technology review for this sector in over a decade. 3National Emission Standards for Hazardous Air Pollutants: Chemical Manufacturing Area Sources Technology Review
The rule adds generally available control technology (GACT) standards pursuant to Clean Air Act section 112(d)(6). Key provisions include:
- LDAR programs for equipment in organic HAP service, covering valves, pumps, connectors, and other components
- Monitoring requirements for heat exchange systems where organic HAPs may be released
- Updated recordkeeping and reporting obligations
The CMAS NESHAP covers nine area source categories, including facilities manufacturing inorganic chemicals, plastics, and synthetic materials. 4Chemical Manufacturing Area Sources: National Emission Standards for Hazardous Air Pollutants - EPA Existing affected sources face compliance deadlines that will require prompt assessment of current leak detection programs and potential capital investment in monitoring equipment.
California Title V Permit Revision: Post-SSM Litigation Group Cleanup
The EPA's proposed revision to the Monterey Bay Air Resources District's (MBARD) Title V Operating Permits Program, published on 2 April 2026, represents a notable post-litigation adjustment. The proposal removes emergency affirmative defense provisions from the district's Title V program, removes permitting requirements for greenhouse gases, and creates procedures for electronic public noticing of permits. 5Clean Air Act Operating Permit Program Revision; California; Monterey Bay Air Resources District
This action follows the D.C. Circuit's September 2025 decision in SSM Litigation Group v. EPA, which reversed the EPA's 2023 rule rescinding the emergency affirmative defense for Title V permit holders. The court in SSM Litigation Group v. EPA, 150 F.4th 593 (D.C. Cir. 2025), rejected the legal bases for the EPA's 2023 rescission of the emergency defense, effectively restoring the prior framework at the federal level. 6SSM Litigation Group v. EPA, 150 F.4th 593 (D.C. Cir. 2025) Critically, the court's ruling does not prohibit states from voluntarily removing such provisions. MBARD's request to remove its emergency defense provisions thus proceeds on independent grounds. Other state and local air districts may follow a similar path, creating a patchwork of emergency defense availability across jurisdictions.
EU Directive 2024/2881: A Contrasting Trajectory
While the US regulatory environment displays conflicting signals-repealing power plant standards while tightening chemical manufacturing rules-the EU is moving unambiguously toward stricter air quality requirements. Directive (EU) 2024/2881 on ambient air quality and cleaner air for Europe entered into force on 10 December 2024, with Member States required to transpose it into national law by 11 December 2026. 7Directive (EU) 2024/2881 on ambient air quality and cleaner air for Europe (recast)
The recast directive aligns EU air quality standards more closely with WHO Global Air Quality Guidelines: annual limit values for PM₂.₅ will drop from 25 µg/m³ to 10 µg/m³, and for NO₂ from 40 µg/m³ to 20 µg/m³, with compliance required by 1 January 2030. 8The European Union Agreed on New Rules & PM2.5/NO2 Limits for Cleaner Air Member States may request extensions to 2040 under specific circumstances, but the direction is clear. For multinational operators with facilities on both sides of the Atlantic, the divergence creates asymmetric compliance risk: relaxed standards in the US power sector versus substantially tighter ambient limits in the EU.
What Compliance Teams Should Watch
The coming months will test compliance infrastructure across sectors:
- Power sector (US): Monitor D.C. Circuit litigation on the MATS repeal. Maintain readiness for potential reinstatement of 2024 standards.
- Chemical manufacturing (US): Assess LDAR program gaps against the new CMAS NESHAP requirements and begin planning for compliance.
- Title V permit holders (California and beyond): Evaluate whether emergency defense provisions remain available in applicable jurisdictions, given the split between federal court restoration and voluntary state-level removal.
- EU operations: Track national transposition of Directive 2024/2881 ahead of the December 2026 deadline, and begin modelling against the new PM₂.₅ and NO₂ limits applicable from 2030.
The simultaneous loosening and tightening of air quality standards across different sectors and jurisdictions underscores a broader reality: compliance risk management in 2026 requires granular, jurisdiction-by-jurisdiction analysis rather than reliance on any single regulatory trend.
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