Published April 6, 2026 · Updated monthly
Fastest-Improving Air Quality Cities in America
While headlines focus on cities with worsening air, 346 of 1,020 US cities are actually getting cleaner. These cities show the steepest downward AQI trends over the past decade — proof that investment in clean energy, emission controls, and urban planning pays off in breathable results.
Top 20 Cities With the Fastest AQI Improvement
Ranked by trend slope — a negative slope means AQI is decreasing (improving) year over year. The steeper the slope, the faster the air is getting cleaner.
| Rank | City | State | Current AQI | Grade | Trend |
|---|---|---|---|---|---|
| 1 | Hawaii, Hawaii | HI | 23 | A | -5.2/yr |
| 2 | Carbon, Wyoming | WY | 8 | A | -4.8/yr |
| 3 | Uinta, Wyoming | WY | 6 | A | -4.5/yr |
| 4 | Rosebud, Montana | MT | 3 | A | -3.6/yr |
| 5 | St Croix, Virgin Islands | VI | 29 | A | -3.5/yr |
| 6 | Monroe, Michigan | MI | 25 | A | -3.2/yr |
| 7 | Matanuska-Susitna, Alaska | AK | 14 | A | -2.7/yr |
| 8 | Alexandria City, Virginia | VA | 6 | A | -2.5/yr |
| 9 | Napa, California | CA | 41 | B | -2.3/yr |
| 10 | Colleton, South Carolina | SC | 26 | A | -2.3/yr |
| 11 | Caguas, Puerto Rico | PR | 6 | A | -2.3/yr |
| 12 | Humboldt, California | CA | 32 | A | -2.3/yr |
| 13 | Wyoming, Pennsylvania | PA | 27 | A | -2.1/yr |
| 14 | Jefferson, Oregon | OR | 31 | A | -2.0/yr |
| 15 | Cook, Minnesota | MN | 13 | A | -2.0/yr |
| 16 | Floyd, Indiana | IN | 46 | A | -2.0/yr |
| 17 | Floyd, Georgia | GA | 46 | B | -1.9/yr |
| 18 | Juncos, Puerto Rico | PR | 9 | A | -1.9/yr |
| 19 | Douglas, Nevada | NV | 28 | A | -1.8/yr |
| 20 | Jackson, Indiana | IN | 35 | A | -1.8/yr |
What's Driving the Improvement?
1. Coal Plant Closures
The shift from coal to natural gas and renewables has dramatically reduced sulfur dioxide and particulate emissions near former coal-dependent cities. The US Energy Information Administration reports coal dropped from 33% of electricity generation in 2014 to under 16% by 2023.
2. Cleaner Vehicle Fleet
Newer cars emit dramatically less pollution than older ones. As the average vehicle age in the US fleet turns over, total tailpipe emissions decline — even as driving miles increase. The growth of electric vehicles, while still small in absolute numbers, contributes most in early-adopter metros like the cities above.
3. Industrial Emission Controls
EPA regulations requiring scrubbers, catalytic converters, and emission monitoring at industrial facilities continue to reduce point-source pollution. Cities near heavy industry have seen some of the steepest AQI improvements as older facilities upgrade or close.
4. The Clean Air Act Legacy
The Clean Air Act, signed in 1970 and strengthened in 1990, remains the most impactful piece of environmental legislation in US history. EPA estimates it has prevented over 230,000 premature deaths per year and delivered $32 in health benefits for every $1 spent on compliance.
Will the Improvement Continue?
For most of these cities, the trend is likely to hold. The transition to renewables and EVs accelerates each year, and few of these cities face significant wildfire risk. However, rising temperatures could increase ozone formation in some areas, and any reversal of emission regulations could slow progress.
The biggest threat to continued improvement is wildfire smoke. Even cities with declining local emissions can see AQI spikes from distant fires. Check our wildfire smoke analysis for more.
Frequently Asked Questions
Based on 10 years of EPA data, the cities at the top of our fastest-improving ranking show the steepest downward AQI trends. See the full table above for the current leaders, ranked by rate of improvement.
Yes. 346 of 1,020 tracked cities show improving AQI trends, while 244 are getting worse. National aggregate air quality has improved significantly since the 1970s, driven by the Clean Air Act and cleaner energy.
The biggest drivers of air quality improvement in US cities are: coal plant closures (replaced by natural gas and renewables), newer vehicle fleets with lower per-car emissions, industrial emission controls, and in some cities, remote work reducing commute traffic.
Yes. Several cities that had C or D grades a decade ago have improved to B or even A grades. Pittsburgh is a notable example — once infamous for steel mill smog, it has seen dramatic AQI improvement as heavy industry was replaced by technology and healthcare sectors.
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