National fine-particle standard
EPA’s current primary annual PM₂.₅ standard is 9.0 µg/m³, averaged over three years. The 2024 action lowered it from 12.0 µg/m³ while retaining the other PM standards.
Facts, status, dates, and primary evidence
EPA air-quality actions since 2022
Since 2022, EPA has changed national ambient standards, mobile-source requirements, industrial air-toxics rules, interstate-ozone controls, monitoring and reporting systems, grant programs, and enforcement priorities. Several actions remain operative, while others were stayed, reconsidered, revised, disapproved, or repealed. Dates and current status are linked to primary evidence.
Horizontal timeline
Click any event card to open its primary sourceEach event is positioned by year rather than exact day-scale distance so dense periods remain legible. Exact dates are printed on the cards. Additional sources for every event appear in the evidence ledger below.
Final factual synthesis
Every claim includes evidence linksHeavy-duty conventional pollutants
The December 20, 2022 heavy-duty rule applies from model year 2027 and establishes stronger standards for pollutants that contribute to ozone and particulate matter, with longer useful-life requirements.
Evidence: EPA rule page ↗ Federal Register ↗
Good Neighbor Plan
EPA finalized the plan in 2023. The Supreme Court stayed enforcement on June 27, 2024. EPA issued an administrative stay on October 29, 2024. EPA’s current page states the plan is stayed in its entirety across the 23 originally covered states.
Oil and gas
EPA announced the final methane and VOC rule on December 2, 2023 and published it on March 8, 2024. It covers new sources and supplies emissions guidelines for state plans addressing existing sources; subsequent technical corrections and reconsideration actions followed.
Chemical-sector air toxics
The April 2024 chemical-sector rule applies to about 200 plants. EPA required fenceline monitoring for six named air toxics and projected annual reductions of more than 6,200 tons of air toxics after implementation.
Commercial sterilizers
The 2024 ethylene-oxide rule took effect April 5, 2024. EPA proposed substantial revisions on March 17, 2026, including rescission of risk-based standards and changes to technology and compliance provisions.
Motor-vehicle greenhouse gases
EPA finalized rescission of the 2009 endangerment finding and federal greenhouse-gas standards for new motor vehicles and engines on February 12, 2026. This does not by itself describe the status of every separate criteria-pollutant provision.
Power-plant mercury and air toxics
EPA finalized stronger MATS amendments in 2024 and finalized their repeal in February 2026. EPA states that the pre-2024 MATS requirements continue to be enforced.
Monitoring and equipment programs
EPA selected 132 community-monitoring projects for $53.4 million in November 2022. The Clean School Bus program was authorized for $5 billion over FY2022–2026. EPA selected 55 Clean Ports applicants for nearly $3 billion in October 2024.
Observed outcomes
EPA’s national trends data show long-run reductions in common-pollutant emissions, but those data do not isolate the causal contribution of rules finalized since 2022. Many recent requirements depend on future compliance dates, state implementation, equipment deployment, or fleet turnover.
Monthly direction of major active standards
January 2022–August 2026Cumulative active strengthening actions
This is a count, not a weighted stringency index. Each major finalized strengthening action adds one when published or effective. A judicial stay, final rescission, or final repeal removes one. Proposals, endangerment findings, grants, monitoring programs, enforcement priorities, and technical guidance do not change the line.
Strengthening action Stay, rescission, or repeal
Net change by month
The monthly bars expose when the cumulative line changed. Months without a qualifying final action remain at zero.
View chart accounting and evidence
| Month | Direction | Action | Evidence |
|---|---|---|---|
| 2023-01 | Raised / strengthened | Heavy-duty NOₓ and PM standards | Primary evidence ↗ |
| 2023-06 | Raised / strengthened | Good Neighbor Plan | Primary evidence ↗ |
| 2024-03 | Raised / strengthened | Oil and gas methane/VOC standards | Primary evidence ↗ |
| 2024-03 | Raised / strengthened | Annual PM₂.₅ NAAQS strengthened | Primary evidence ↗ |
| 2024-04 | Raised / strengthened | Commercial sterilizer EtO standards | Primary evidence ↗ |
| 2024-04 | Raised / strengthened | Light- and medium-duty multipollutant standards | Primary evidence ↗ |
| 2024-04 | Raised / strengthened | Gasoline distribution air-toxics standards | Primary evidence ↗ |
| 2024-04 | Raised / strengthened | Integrated iron and steel air-toxics standards | Primary evidence ↗ |
| 2024-05 | Raised / strengthened | Chemical-sector air-toxics standards | Primary evidence ↗ |
| 2024-05 | Raised / strengthened | 2024 MATS amendments | Primary evidence ↗ |
| 2024-05 | Raised / strengthened | Primary copper-smelting air-toxics standards | Primary evidence ↗ |
| 2024-06 | Lowered / removed from active count | Good Neighbor Plan stayed by Supreme Court | Primary evidence ↗ |
| 2024-07 | Raised / strengthened | Coke-oven air-toxics standards | Primary evidence ↗ |
| 2024-07 | Raised / strengthened | Lime-manufacturing air-toxics standards | Primary evidence ↗ |
| 2024-11 | Raised / strengthened | Rubber-tire manufacturing air-toxics standards | Primary evidence ↗ |
| 2024-12 | Raised / strengthened | Secondary SO₂ NAAQS revised | Primary evidence ↗ |
| 2026-02 | Lowered / removed from active count | Motor-vehicle GHG standards rescinded | Primary evidence ↗ |
| 2026-02 | Lowered / removed from active count | 2024 MATS amendments repealed | Primary evidence ↗ |
Boundary: The count treats each major action as one unit regardless of pollutant, affected sector, projected tonnage, population exposure, or legal scope. It is suitable for showing policy direction and durability, not comparing health impact or legal stringency.
Additional verified actions and implementation changes
Material items added after the comprehensive gap reviewOctober 18, 2023
Aircraft lead endangerment finding
EPA determined that lead emissions from aircraft engines operating on leaded fuel cause or contribute to air pollution that may reasonably be anticipated to endanger public health and welfare. EPA stated that this finding is a prerequisite to proposing aircraft-engine lead-emission standards; it did not itself establish an emissions limit.
December 27, 2024
Secondary sulfur-dioxide standard revised
EPA replaced the prior secondary 3-hour sulfur-dioxide standard with an annual secondary standard of 10 parts per billion, averaged over three consecutive years, to address welfare effects associated with sulfur deposition. EPA retained the existing secondary standards for oxides of nitrogen and particulate matter.
March 14, 2024
Gasoline distribution air-toxics standards
EPA finalized amendments for gasoline distribution facilities, including bulk gasoline terminals, pipeline breakout stations, bulk plants, and gasoline dispensing facilities. EPA described the action as reducing hazardous air pollutants and volatile organic compounds from storage and transfer operations.
Evidence:
EPA announcement ↗
Federal Register ↗
April 3, 2024
Integrated iron and steel air-toxics amendments
EPA finalized amendments to the hazardous-air-pollutant standards for integrated iron and steel manufacturing facilities. The action addressed previously unregulated emissions and revised monitoring, testing, reporting, and work-practice requirements.
Evidence:
Federal Register ↗
EPA source-category page ↗
May 13, 2024
Primary copper-smelting air-toxics amendments
EPA finalized residual-risk and technology-review amendments for primary copper smelters. The final rule added and revised controls for hazardous air pollutants, including metal emissions, and included requirements intended to address risks EPA identified in the source category.
Evidence:
Federal Register ↗
EPA source-category page ↗
July 5, 2024
Coke-oven air-toxics rule
EPA finalized amendments for coke-oven batteries and pushing, quenching, and battery-stack operations. The rule added fenceline monitoring and revised emission limits and work-practice requirements. EPA later issued and then withdrew an interim deadline extension; the current EPA page should be used for implementation status.
July 16, 2024
Lime-manufacturing air-toxics amendments
EPA finalized technology-review amendments for lime-manufacturing plants and established standards for hydrogen chloride, mercury, organic hazardous air pollutants, and dioxins and furans that had not previously been regulated under this source-category rule.
Evidence:
Federal Register ↗
EPA source-category page ↗
November 29, 2024
Rubber-tire manufacturing air-toxics amendments
EPA promulgated amendments to the hazardous-air-pollutant standards for rubber-tire manufacturing. The action addressed previously unregulated emissions and revised compliance, testing, monitoring, recordkeeping, and reporting provisions.
Evidence:
Federal Register ↗
EPA source-category page ↗
January 3, 2025
Ozone implementation-rule changes
EPA finalized revisions intended to clarify state planning requirements when ozone nonattainment areas are reclassified. EPA announced reconsideration in June 2025 and proposed further revisions on June 9, 2026. The 2025 rule therefore remains subject to continuing rulemaking.
July 25, 2023
Air Emissions Reporting Requirements proposed update
EPA proposed expanding and standardizing emissions reporting, including annual hazardous-air-pollutant reporting for certain point sources beginning in 2027. As of this report, EPA describes this as a proposed action rather than a finalized reporting rule.
Evidence:
EPA AERR page ↗
Federal Register proposal ↗
December 18, 2024–June 2025
California vehicle-waiver actions and congressional disapproval
EPA granted California waivers or authorizations for several vehicle-emission programs in late 2024. Congress subsequently used the Congressional Review Act in 2025 to disapprove three waiver actions, and the resolutions were signed into law in June 2025. These actions affect California-led vehicle policy but do not replace EPA’s separate federal criteria-pollutant rules.
April 1, 2026
Clean School Bus delivery evidence
EPA’s Office of Inspector General reported that the 2023 Clean School Bus rebate program awarded approximately $815 million to 458 school districts for 3,241 replacement buses: 2,847 electric, 393 propane, and one compressed-natural-gas bus. The report distinguishes awards from payment and program completion.
Evidence:
EPA OIG report ↗
EPA awards page ↗
June 26, 2026
Wildfire and exceptional-events tools expanded
EPA expanded its Expedited Modeling of Burn Events Results tool to support ozone exceptional-event demonstrations for fire-affected monitoring data from 2021 through 2025. Data accepted under the Exceptional Events Rule may be excluded from specified regulatory determinations, but the underlying exposure still occurred.
August 17, 2023
Air-toxics enforcement priority
EPA selected reducing air toxics in overburdened communities as one of its national enforcement and compliance initiatives for fiscal years 2024–2027. This is an enforcement priority, not a new emissions standard; results depend on inspections, cases, settlements, and corrective actions.
Evidence distinction: A final rule, a funded selection, an effective requirement, a stayed requirement, and a measured air-quality outcome are different facts. EPA projections are identified as projections; they are not reported here as observed outcomes.
Timeline evidence ledger
16 dated events · multiple sources where available1
November 3, 2022
Community air-monitoring selections
EPA announced 132 air-monitoring projects in 37 states selected for $53.4 million from the Inflation Reduction Act and American Rescue Plan.
2
December 20, 2022
Heavy-duty engine and vehicle rule signed
EPA adopted stronger emissions standards for model-year 2027 and later heavy-duty engines and vehicles, covering pollutants that contribute to ozone and particulate matter.
3
March 15, 2023
Good Neighbor Plan announced
EPA finalized a federal plan to reduce interstate transport of ozone-forming NOₓ from power plants and specified industrial sources.
4
December 2, 2023
Oil and gas methane/VOC rule announced
EPA issued standards for methane and smog-forming volatile organic compounds from new sources and emissions guidelines for existing oil and natural-gas sources.
5
February 7, 2024
Annual PM₂.₅ standard set at 9.0 µg/m³
EPA strengthened the primary annual fine-particle standard from 12.0 to 9.0 micrograms per cubic meter and retained the other PM standards.
6
March 14, 2024
Commercial sterilizer EtO rule announced
EPA finalized strengthened ethylene-oxide controls for commercial sterilization facilities; the rule became effective when published on April 5, 2024 and is under reconsideration.
7
March 20, 2024
Light- and medium-duty multipollutant rule announced
EPA finalized model-year 2027–2032 standards for criteria pollutants and greenhouse gases from light- and medium-duty vehicles.
8
April 9, 2024
Chemical-sector air-toxics rule announced
EPA finalized standards for roughly 200 chemical plants, including fenceline monitoring for six listed air toxics and projected annual reductions exceeding 6,200 tons of air toxics.
9
April 25, 2024
2024 MATS amendments announced
EPA finalized tighter filterable-particulate, lignite-mercury, and continuous-monitoring requirements for coal- and oil-fired power plants; those 2024 amendments were later repealed.
10
June 27, 2024
Supreme Court stays Good Neighbor Plan
The Supreme Court granted applications to stay enforcement of the Good Neighbor Plan while judicial review proceeds.
Sources: Supreme Court opinion ↗ EPA status page ↗
11
October 29, 2024
Clean Ports selections announced
EPA selected 55 applicants across 27 states and territories for nearly $3 billion in zero-emission port equipment, infrastructure, and air-quality planning projects.
12
October 29, 2024
EPA administrative stay of Good Neighbor requirements
EPA issued a final rule administratively staying Good Neighbor Plan requirements for covered sources where an administrative stay was not already in place.
13
June 11, 2025
Power-sector repeal proposals announced
EPA proposed repealing the 2024 MATS amendments and the 2024 greenhouse-gas standards for fossil-fuel-fired power plants.
14
February 12, 2026
Motor-vehicle GHG framework rescinded
EPA finalized rescission of the 2009 greenhouse-gas endangerment finding and federal greenhouse-gas standards for new motor vehicles and engines.
15
February 19, 2026
2024 MATS amendments repealed
EPA finalized repeal of the more stringent filterable-particulate standard, lignite-mercury standard, and PM continuous-monitoring requirement added in 2024; the earlier MATS framework remains.
16
March 17, 2026
Commercial sterilizer EtO revisions proposed
EPA proposed rescinding risk-based standards and revising technology and compliance-demonstration provisions in the 2024 commercial-sterilizer rule.