Nitrogen Oxides (NOx)

US EPA Approves Arizona Gila County RACT SIP for 2015 Ozone NAAQS

In May 2026, the US EPA approved Arizona’s 2025 state implementation plan revision demonstrating reasonably available control technology for ozone precursors in the Gila County portion of the Phoenix–Mesa nonattainment area, with the rule taking effect on 22 June 2026. This makes ADEQ’s RACT analysis and extensive negative declarations for VOC and NOx source categories federally enforceable, giving operators greater certainty on current control expectations while shaping how future sources and permits will be evaluated under the Clean Air Act.

23 May 2026, 11:16federalregister.govUnited States

Dutch EIA Commission Criticises Environmental Impact Report for Schiphol Airport Traffic Decree 2026

In May 2026 the Dutch Commission for Environmental Impact Assessment issued a highly critical review of the environmental impact report for the proposed Schiphol Airport Traffic Decree 2026, finding that the study does not adequately demonstrate noise, air-quality, nature-protection or safety outcomes and must be comprehensively revised before the minister can lawfully decide. This pushes the LVB 2026 process back into further technical work, delaying clarity on future flight limits and potentially leading to stricter environmental measures around Schiphol that could constrain capacity growth and require additional mitigation investments.

20 May 2026, 19:20zoek.officielebekendmakingen.nlNetherlands

California Air Resources Board Settles $196.5 Million NOx Emissions Case With Volvo Group North America

In May 2026, the California Air Resources Board agreed a $196.5 million settlement with Volvo Group North America over undisclosed NOx-related emission control devices on around 10,000 heavy-duty diesel engines in California. The case signals aggressive enforcement of California’s heavy-duty engine rules and highlights the need for manufacturers and fleets to tighten AECD disclosure, certification documentation, and planning for future Clean Truck Check compliance and recall-related repairs.

20 May 2026, 08:28ww2.arb.ca.govUnited States

Netherlands Outlines 2030 EU Ambient Air Quality Obligations for National and Local Authorities

The Netherlands’ environment information portal is briefing national and local authorities on how the new EU Ambient Air Quality Directive 2024/2881 will tighten nitrogen dioxide and particulate matter limits from 2030 and what must happen between now and then. For operators and project developers, this signals earlier consideration of 2030 standards in permits and spatial planning, mandatory air-quality roadmaps by 2028 where exceedances are likely, and growing pressure to curb NO2 and PM emissions ahead of the deadline.

20 May 2026, 07:10eur-lex.europa.euEuropean UnionNetherlands

US EPA Approves Illinois 2015 Ozone Moderate Attainment SIP Elements for Chicago and Metro East Areas

In May 2026, the US Environmental Protection Agency finalised approval of key Illinois State Implementation Plan elements for the Chicago and Metro East areas under the 2015 ozone standard, effective 15 June 2026. This makes the state's updated emissions inventory, 2023 motor vehicle emissions budgets, inspection and maintenance program, and nonattainment new source review requirements federally enforceable, tightening air quality planning and transportation conformity expectations for sources and planners in these regions.

14 May 2026, 19:09federalregister.govUnited States

DNREC Advises on Delaware City Refining Repairs and Elevated Sulfur Dioxide Emissions

DNREC has warned that planned repair work at Delaware City Refining will temporarily shift pollution controls, driving significantly higher sulphur dioxide emissions for about four weeks while expanded air and fenceline monitoring tracks community exposure. This points to an expected period of permit exceedances and continued enforcement focus on air quality around the refinery, heightening operational and reputational risk for refinery operators and nearby industrial emitters.

11 May 2026, 11:56news.delaware.govUnited States

CJEU Preliminary Reference on Diesel Defeat Devices and Burden of Proof (Case C-8/26, Bager)

An Austrian court has asked the EU Court of Justice to clarify how Euro 5/6 vehicle-emissions rules on defeat devices apply to EGR “temperature windows” and similar strategies in diesel vehicles, and how burdens of proof should be shared between buyers and manufacturers. The ruling could reshape litigation risk and compliance expectations across the EU for diesel vehicle emissions controls and real-driving performance, even though the underlying regulations remain unchanged.

7 May 2026, 05:58eur-lex.europa.euEuropean UnionAustria

EU Court of Justice Publishes Preliminary Reference in Case C-74/26 (Volkswagen) on Diesel Emissions Defeat Devices

In May 2026, the EU Court of Justice published an Austrian preliminary reference in Case C-74/26 (Volkswagen) on how Euro 5/6 "defeat device" rules apply to diesel NOx control systems and real-driving emissions. The case could tighten expectations on vehicle design and testing, shift litigation burdens toward manufacturers, and influence future enforcement and compliance strategies for diesel and other combustion vehicles across the EU.

7 May 2026, 05:58eur-lex.europa.euEuropean UnionAustria

Mexico Proposes Emission Limits and OBD Requirements for New Gasoline Motorcycles (PROY-NOM-175-SEMARNAT-2026)

Mexico has published draft standard PROY-NOM-175-SEMARNAT-2026 to impose Euro-style exhaust and evaporative emission limits, durability requirements, and onboard diagnostics for new gasoline motorcycles, with public consultation open until 29 June 2026. If adopted, the rule will materially tighten compliance obligations for motorcycle manufacturers and importers in Mexico, requiring upgraded emission-control technologies, new certification testing strategies, and preparation for a 180-day transition period after final publication.

5 May 2026, 13:52sidofqa.segob.gob.mxMexico

Texas Commission on Environmental Quality Opens $116 Million TERP Rebate Grants Program

In late April 2026, the Texas Commission on Environmental Quality opened a $116 million TERP Rebate Grants funding round to support NOx-reducing upgrades of heavy-duty vehicles, equipment and associated alternative-fuel infrastructure in eligible Texas counties through a first-come, first-served process. This creates a time-bound opportunity for fleet operators and other eligible entities in Texas to secure up to 80% co-funding for cleaner technologies ahead of a 28 July 2026 application deadline, supporting air quality and emission-reduction strategies.

4 May 2026, 18:28content.govdelivery.comUnited States

Texas Commission on Environmental Quality Opens TERP Rebate Grants for Heavy-Duty Diesel Vehicles and Equipment

Texas has opened the TERP Rebate Grants Program with $116 million in first-come, first-served funding through July 2026 to support replacement, repower and electrification of heavy-duty diesel vehicles and equipment in eligible Texas counties. This materially reduces the cost of fleet decarbonisation and air-quality compliance investments for Texas operators, so eligible businesses should quickly identify projects and prepare applications before funding is exhausted.

4 May 2026, 18:27tceq.texas.govUnited States

Satellite Observations Reveal Nitrogen Oxide Emissions From World's Largest Copper Mines

A peer-reviewed Environmental Research Letters study, highlighted by the Business & Human Rights Resource Centre in April 2026, uses satellite NO2 data to quantify nitrogen oxide emissions from 14 of the world’s largest open-pit copper mines in the United States, Chile, Peru, Mexico and Zambia, revealing high and in many cases rising emissions linked to diesel mining fleets and material moved. This offers regulators, investors and operators an independent tool to benchmark mine-level NOx performance, potentially increasing pressure for stricter air permits, better NOx reporting and accelerated electrification of mobile equipment at large copper mines in the highlighted jurisdictions.

4 May 2026, 18:24business-humanrights.orgUnited StatesChilePeruMexico

Informative Inventory Report 2026: Emissions of Transboundary Air Pollutants in the Netherlands (1990–2024)

The Netherlands has published its 2026 Informative Inventory Report confirming that 2023 emissions of key transboundary air pollutants remain comfortably below the reduction commitments set by the EU National Emission Reduction Commitments Directive and the CLRTAP framework. For compliance and strategy teams this is a signalling, not binding, development: it confirms current headroom under existing emission caps and may shape future Dutch and EU air-quality policy, but it does not itself create new obligations for individual companies.

4 May 2026, 09:15rivm.nlNetherlandsEuropean Union

US EPA Proposes Approval of Maryland NOX RACT Plan for Municipal Waste Combustors

EPA has proposed to approve Maryland’s SIP revisions that embed NOX RACT emission limits and continuous monitoring requirements for municipal waste combustors into the federally enforceable Clean Air Act framework, with comments due by 29 May 2026. This would lock in tighter long-term NOX controls for Maryland’s two large waste-to-energy facilities and confirm their role in meeting 2008 and 2015 ozone standards, reinforcing compliance obligations and operating costs for waste incineration in the state.

3 May 2026, 09:13federalregister.govUnited States

Denmark Environment And Food Appeals Board Upholds Monitoring Obligations For Helsingør CHP Plant

Denmark’s Environment and Food Appeals Board has confirmed that a 133 MW gas‑fired CHP plant in Helsingør must continue to comply fully with strict continuous emissions monitoring and QAL2/AST quality‑assurance obligations under the national large combustion plant rules. This ruling signals that operators of large combustion plants in Denmark cannot rely on EU BAT footnotes or low operating hours to relax AMS monitoring requirements, reinforcing conservative compliance planning for emissions monitoring investments and maintenance.

30 Apr 2026, 15:44mfkn.naevneneshus.dkDenmark

Oklahoma DEQ Opens Public Comment On Draft Title V Renewal For Spirit AeroSystems Tulsa Facility (2025-0637-TVR4)

On 29 April 2026, Oklahoma DEQ opened a 30-day public comment period on the draft renewal of Spirit AeroSystems’ Tulsa Title V air operating permit 2025-0637-TVR4, setting updated emission limits for VOCs, NOx, CO, PM10, SO2 and HAPs. This keeps the facility operating as a major air source, so affected businesses should review the draft conditions now to understand future emissions constraints, investment needs, and any implications for local permitting or community expectations.

30 Apr 2026, 06:54applications.deq.ok.govUnited States

Netherlands Amends Vehicle Regulation To Enforce NOx Emissions-System Reagent Use and Ban Tampering

From 1 July 2026, the Netherlands will enforce new obligations on vehicle owners, holders, and drivers to keep NOx emissions-control systems working properly and to use urea-based reagents correctly. This strengthens roadside enforcement against tampering and defective systems, cutting NOx emissions from trucks and other diesel vehicles while removing unfair cost advantages for non-compliant operators.

29 Apr 2026, 18:13zoek.officielebekendmakingen.nlNetherlands

Rechtbank Oost-Brabant Annuls NOx Limit in Dow Terneuzen Environmental Permit

A Dutch court has annulled the nitrogen-oxide emission condition in Dow Terneuzen’s environmental permit after ILT’s appeal, ordering the Province of Zeeland to issue a new, better-justified decision within six months while stricter statutory NOx limits temporarily apply. This raises immediate air-emissions compliance risk for one of the Netherlands’ largest industrial nitrogen emitters and tightens the standard for any future permit deviations from statutory NOx norms, signalling closer scrutiny of large combustion installations.

28 Apr 2026, 11:33ilent.nlNetherlands

MassDEP Penalizes Power Plant for Air Permit Violations in Pittsfield

MassDEP has issued a $21,500 consent-order penalty to Pittsfield Generating Company for exceeding nitrogen oxide and ammonia emission limits in its Pittsfield power plant air operating permit in 2025. The case signals strict state enforcement of air permits for power generators, reinforcing expectations for continuous emissions monitoring, operator training, and prompt corrective action when limits are breached.

23 Apr 2026, 14:17mass.govUnited States

UK MCA Issues MGN 717 on Air-Quality Amendments to MARPOL and IGF/NOx Codes

The UK Maritime and Coastguard Agency has issued Marine Guidance Note MGN 717 to explain 2026 international air-quality amendments under MARPOL Annex VI, the IGF Code and the NOx Technical Code, and how they take effect in UK merchant shipping law. Shipowners and operators using marine diesel engines or gas-fuelled ships should align SEEMP documentation, IGF Code compliance and engine certification with these updated international standards and dates, noting that the UK has not added requirements beyond the global rules.

22 Apr 2026, 21:02gov.ukUnited Kingdom