Updated April 2026 · EPA Air Quality System
Fastest-Improving Air Quality Cities
Of 1,020 U.S. cities tracked, 346 show improving air quality trends across 10 years of EPA monitoring. The 200 cities below have the steepest declines — places where the air is measurably cleaner today than a decade ago, and the structural shifts behind that progress (cleaner cars, retired coal plants, tighter EPA standards) are durable.
What's Actually Changing
The improvements on this list are not a measurement artifact. Three concrete shifts are doing the work. First, vehicle fleet turnover: every year cleaner Tier 3 cars and electric vehicles replace older, dirtier ones, and the cumulative effect on urban NO2 and PM2.5 is now substantial — visible in EPA AirNow daily data and clearly in the long EPA AQS archive used here.
Second, the power-generation mix. Hundreds of U.S. coal-fired generating units have retired since 2010, replaced by natural gas and renewables that emit far less SO2, NO2, and primary PM2.5 — the upwind improvement shows up in cities downwind of the retired plants, sometimes hundreds of miles away. Third, tighter EPA standards on major industrial sources: refineries, cement plants, pulp mills, and ports have absorbed real emission-control investments. The WHO air-quality guidelines document the public-health value of those declines.
Top 10 Steepest Improvers
| # | City | Trend (AQI/yr) | Current Median | Grade | Dominant Pollutant |
|---|---|---|---|---|---|
| 1 | Hawaii, Hawaii | -5.21 | 23 | A | PM2.5 |
| 2 | Carbon, Wyoming | -4.85 | 8 | A | Ozone |
| 3 | Uinta, Wyoming | -4.54 | 6 | A | Ozone |
| 4 | Rosebud, Montana | -3.62 | 3 | A | Ozone |
| 5 | St Croix, Virgin Islands | -3.45 | 29 | A | PM2.5 |
| 6 | Monroe, Michigan | -3.16 | 25 | A | PM10 |
| 7 | Matanuska-Susitna, Alaska | -2.72 | 14 | A | PM2.5 |
| 8 | Alexandria City, Virginia | -2.47 | 6 | A | PM10 |
| 9 | Napa, California | -2.33 | 41 | B | PM2.5 |
| 10 | Colleton, South Carolina | -2.31 | 26 | A | PM2.5 |
Improving vs. Already Clean
"Improving" and "clean" are different signals. A city near the top of this list might still post above-average AQI today — it has come a long way, but is not yet at the U.S. mean. Conversely, a city already at the cleanest tier may show a flat trend because there is little headroom left to improve. The improvement ranking captures rate of change; the cleanest-air ranking captures absolute level. Both are useful, and they answer different questions.
For someone deciding whether to relocate, the absolute level matters more than the trend. For someone evaluating policy effectiveness, the trend is the headline. For someone with asthma, COPD, or pregnancy, the count of unhealthy days per year — visible on each city's profile — is often the most actionable single number. The personal exposure estimator ties cumulative exposure to years lived in a city.
What Could Reverse the Progress
Two forces work in the other direction. Wildfire smoke, particularly across the West, has reversed multiple years of progress in the worst fire seasons — a single late-summer smoke event can push a metro's annual AQI well above its long-run trend line. And rollbacks of EPA emission standards or deferred enforcement could slow the cleaner-vehicle pipeline that drives much of the urban improvement. The trend slope shown on this page averages across the dataset window, smoothing single-year volatility.
For the opposite end of the distribution — cities where air is still well above the national norm — see theworst-air-quality ranking, which focuses on the public-health cost of sustained elevated PM2.5 and ozone exposure.
Full Ranking — Top 200 Fastest-Improving Cities
#1Hawaii, Hawaii
Primary pollutant: PM2.5
#2Carbon, Wyoming
Primary pollutant: Ozone
#3Uinta, Wyoming
Primary pollutant: Ozone
#4Rosebud, Montana
Primary pollutant: Ozone
#5St Croix, Virgin Islands
Primary pollutant: PM2.5
#6Monroe, Michigan
Primary pollutant: PM10
#7Matanuska-Susitna, Alaska
Primary pollutant: PM2.5
#8Alexandria City, Virginia
Primary pollutant: PM10
#9Napa, California
Primary pollutant: PM2.5
#10Colleton, South Carolina
Primary pollutant: PM2.5
#11Caguas, Puerto Rico
Primary pollutant: NO2
#12Humboldt, California
Primary pollutant: Ozone
#13Wyoming, Pennsylvania
Primary pollutant: PM2.5
#14Jefferson, Oregon
Primary pollutant: PM2.5
#15Cook, Minnesota
Primary pollutant: PM2.5
#16Floyd, Indiana
Primary pollutant: Ozone
#17Floyd, Georgia
Primary pollutant: PM2.5
#18Juncos, Puerto Rico
Primary pollutant: Ozone
#19Douglas, Nevada
Primary pollutant: PM2.5
#20Jackson, Indiana
Primary pollutant: Ozone
#21Fairbanks North Star, Alaska
Primary pollutant: PM2.5
#22Jackson, North Carolina
Primary pollutant: Ozone
#23Morgan, Indiana
Primary pollutant: Ozone
#24Adjuntas, Puerto Rico
Primary pollutant: PM2.5
#25Roane, Tennessee
Primary pollutant: PM2.5
#26Fresno, California
Primary pollutant: Ozone
#27Kern, California
Primary pollutant: Ozone
#28Allen, Indiana
Primary pollutant: PM2.5
#29Mercer, Pennsylvania
Primary pollutant: Ozone
#30Pike, Kentucky
Primary pollutant: PM2.5
#31Tuscaloosa, Alabama
Primary pollutant: Ozone
#32Howard, Maryland
Primary pollutant: PM2.5
#33Clermont, Ohio
Primary pollutant: PM2.5
#34Westmoreland, Pennsylvania
Primary pollutant: PM2.5
#35Orleans, Louisiana
Primary pollutant: PM2.5
#36Anchorage, Alaska
Primary pollutant: PM2.5
#37Luna, New Mexico
Primary pollutant: PM10
#38Madera, California
Primary pollutant: Ozone
#39Suffolk, Massachusetts
Primary pollutant: PM2.5
#40Marion, West Virginia
Primary pollutant: PM2.5
#41Taney, Missouri
Primary pollutant: PM2.5
#42Prince George's, Maryland
Primary pollutant: Ozone
#43Marin, California
Primary pollutant: PM2.5
#44Lemhi, Idaho
Primary pollutant: PM2.5
#45Northampton, Pennsylvania
Primary pollutant: PM2.5
#46Maui, Hawaii
Primary pollutant: PM2.5
#47Montgomery, Tennessee
Primary pollutant: PM2.5
#48San Joaquin, California
Primary pollutant: PM2.5
#49Hughes, South Dakota
Primary pollutant: PM2.5
#50Silver Bow, Montana
Primary pollutant: PM2.5
#51Martin, North Carolina
Primary pollutant: Ozone
#52Cobb, Georgia
Primary pollutant: Ozone
#53St John, Virgin Islands
Primary pollutant: PM2.5
#54Deschutes, Oregon
Primary pollutant: PM2.5
#55Kings, California
Primary pollutant: Ozone
#56Garfield, Washington
Primary pollutant: PM2.5
#57Bucks, Pennsylvania
Primary pollutant: Ozone
#58Ravalli, Montana
Primary pollutant: PM2.5
#59Bay, Michigan
Primary pollutant: PM2.5
#60Elkhart, Indiana
Primary pollutant: PM2.5
#61Howard, Indiana
Primary pollutant: PM2.5
#62Monroe, Pennsylvania
Primary pollutant: Ozone
#63Chester, Pennsylvania
Primary pollutant: PM2.5
#64Erie, Pennsylvania
Primary pollutant: PM2.5
#65Athens, Ohio
Primary pollutant: PM2.5
#66Baltimore (City), Maryland
Primary pollutant: PM2.5
#67Caswell, North Carolina
Primary pollutant: Ozone
#68Ellis, Texas
Primary pollutant: PM2.5
#69New York, New York
Primary pollutant: PM2.5
#70Lebanon, Pennsylvania
Primary pollutant: PM2.5
#71Maverick, Texas
Primary pollutant: PM2.5
#72Mitchell, North Carolina
Primary pollutant: PM2.5
#73Scott, Iowa
Primary pollutant: PM2.5
#74Hartford, Connecticut
Primary pollutant: PM2.5
#75Lake, Ohio
Primary pollutant: PM2.5
#76Sarpy, Nebraska
Primary pollutant: PM2.5
#77Warren, Ohio
Primary pollutant: PM2.5
#78Lubbock, Texas
Primary pollutant: PM2.5
#79Riverside, California
Primary pollutant: Ozone
#80Orange, California
Primary pollutant: PM2.5
#81Black Hawk, Iowa
Primary pollutant: PM2.5
#82Ventura, California
Primary pollutant: PM2.5
#83San Juan, Puerto Rico
Primary pollutant: CO
#84Salem City, Virginia
Primary pollutant: PM2.5
#85Cumberland, Pennsylvania
Primary pollutant: PM2.5
#86Aroostook, Maine
Primary pollutant: PM2.5
#87Skagit, Washington
Primary pollutant: PM2.5
#88Solano, California
Primary pollutant: PM2.5
#89Greene, Ohio
Primary pollutant: PM2.5
#90Hardin, Kentucky
Primary pollutant: PM2.5
#91Harrison, West Virginia
Primary pollutant: PM2.5
#92Orange, Florida
Primary pollutant: Ozone
#93Androscoggin, Maine
Primary pollutant: PM2.5
#94Campbell, Kentucky
Primary pollutant: PM2.5
#95Lynchburg City, Virginia
Primary pollutant: PM2.5
#96San Luis Obispo, California
Primary pollutant: PM2.5
#97Fayette, Texas
Primary pollutant: PM2.5
#98Clay, Alabama
Primary pollutant: PM2.5
#99Juneau, Alaska
Primary pollutant: PM2.5
#100Armstrong, Pennsylvania
Primary pollutant: PM2.5
#101Calaveras, California
Primary pollutant: Ozone
#102Posey, Indiana
Primary pollutant: Ozone
#103Richmond, New York
Primary pollutant: PM2.5
#104Wasco, Oregon
Primary pollutant: PM2.5
#105Berks, Pennsylvania
Primary pollutant: PM2.5
#106Box Elder, Utah
Primary pollutant: Ozone
#107Putnam, Tennessee
Primary pollutant: PM2.5
#108Hudson, New Jersey
Primary pollutant: PM2.5
#109Jefferson, Ohio
Primary pollutant: PM2.5
#110Lexington, South Carolina
Primary pollutant: PM2.5
#111Rockingham, New Hampshire
Primary pollutant: Ozone
#112Los Angeles, California
Primary pollutant: PM2.5
#113Muscatine, Iowa
Primary pollutant: PM2.5
#114Bristol City, Virginia
Primary pollutant: PM2.5
#115Carroll, Indiana
Primary pollutant: Ozone
#116Merced, California
Primary pollutant: Ozone
#117Perry, Indiana
Primary pollutant: Ozone
#118Lackawanna, Pennsylvania
Primary pollutant: PM2.5
#119Tulare, California
Primary pollutant: Ozone
#120Washington, Pennsylvania
Primary pollutant: PM2.5
#121Warrick, Indiana
Primary pollutant: Ozone
#122Chesterfield, South Carolina
Primary pollutant: PM2.5
#123Kent, Maryland
Primary pollutant: Ozone
#124Maury, Tennessee
Primary pollutant: PM2.5
#125Saint Louis, Missouri
Primary pollutant: PM2.5
#126Washington, Minnesota
Primary pollutant: Ozone
#127Fairfield, Connecticut
Primary pollutant: PM2.5
#128Thurston, Washington
Primary pollutant: PM2.5
#129Union, Oregon
Primary pollutant: PM2.5
#130Blair, Pennsylvania
Primary pollutant: PM2.5
#131Kay, Oklahoma
Primary pollutant: PM2.5
#132Twin Falls, Idaho
Primary pollutant: PM2.5
#133Boone, Indiana
Primary pollutant: Ozone
#134Nassau, Florida
Primary pollutant: PM2.5
#135Oconee, South Carolina
Primary pollutant: Ozone
#136Butte, California
Primary pollutant: PM2.5
#137Charlton, Georgia
Primary pollutant: PM2.5
#138Montgomery, Maryland
Primary pollutant: PM2.5
#139Cecil, Maryland
Primary pollutant: PM2.5
#140East Baton Rouge, Louisiana
Primary pollutant: PM2.5
#141Lawrence, Tennessee
Primary pollutant: PM2.5
#142Washington, Maryland
Primary pollutant: PM2.5
#143Jefferson, Missouri
Primary pollutant: PM2.5
#144Van Buren, Iowa
Primary pollutant: PM2.5
#145Northampton, North Carolina
Primary pollutant: PM2.5
#146Bayamon, Puerto Rico
Primary pollutant: CO
#147Shoshone, Idaho
Primary pollutant: PM2.5
#148San Mateo, California
Primary pollutant: PM2.5
#149Santa Barbara, California
Primary pollutant: PM2.5
#150Wake, North Carolina
Primary pollutant: PM2.5
#151Imperial, California
Primary pollutant: PM2.5
#152Muskogee, Oklahoma
Primary pollutant: PM10
#153Clayton, Georgia
Primary pollutant: PM2.5
#154Hyde, North Carolina
Primary pollutant: PM2.5
#155Scotts Bluff, Nebraska
Primary pollutant: PM2.5
#156Cowlitz, Washington
Primary pollutant: PM2.5
#157Harford, Maryland
Primary pollutant: PM2.5
#158Miami-Dade, Florida
Primary pollutant: PM2.5
#159Penobscot, Maine
Primary pollutant: PM2.5
#160Rapides, Louisiana
Primary pollutant: PM2.5
#161Cass, Nebraska
Primary pollutant: PM10
#162Delaware, Pennsylvania
Primary pollutant: PM2.5
#163Erie, New York
Primary pollutant: PM2.5
#164Shelby, Indiana
Primary pollutant: Ozone
#165Anne Arundel, Maryland
Primary pollutant: Ozone
#166Kauai, Hawaii
Primary pollutant: PM2.5
#167LaPorte, Indiana
Primary pollutant: Ozone
#168Palo Alto, Iowa
Primary pollutant: PM2.5
#169Coffee, Georgia
Primary pollutant: PM2.5
#170Buchanan, Missouri
Primary pollutant: PM2.5
#171Tippecanoe, Indiana
Primary pollutant: PM2.5
#172Davidson, North Carolina
Primary pollutant: PM2.5
#173DeKalb, Georgia
Primary pollutant: PM2.5
#174Dubois, Indiana
Primary pollutant: PM2.5
#175Guayama, Puerto Rico
Primary pollutant: PM2.5
#176Honolulu, Hawaii
Primary pollutant: Ozone
#177Macoupin, Illinois
Primary pollutant: Ozone
#178San Bernardino, California
Primary pollutant: Ozone
#179Cass, Missouri
Primary pollutant: PM2.5
#180Etowah, Alabama
Primary pollutant: PM2.5
#181Garfield, Utah
Primary pollutant: Ozone
#182Lawrence, Alabama
Primary pollutant: PM2.5
#183Lucas, Ohio
Primary pollutant: PM2.5
#184Jefferson, Washington
Primary pollutant: PM2.5
#185Lyon, Nevada
Primary pollutant: Ozone
#186Spencer, Indiana
Primary pollutant: PM2.5
#187Franklin, Idaho
Primary pollutant: PM2.5
#188Lafayette, Louisiana
Primary pollutant: PM2.5
#189Ohio, West Virginia
Primary pollutant: Ozone
#190Catawba, North Carolina
Primary pollutant: PM2.5
#191Columbia, Georgia
Primary pollutant: Ozone
#192Ector, Texas
Primary pollutant: PM2.5
#193Kootenai, Idaho
Primary pollutant: PM2.5
#194Orange, New York
Primary pollutant: Ozone
#195Richland, South Carolina
Primary pollutant: PM2.5
#196Stoddard, Missouri
Primary pollutant: PM2.5
#197Washington, Nebraska
Primary pollutant: PM2.5
#198San Francisco, California
Primary pollutant: PM2.5
#199Stafford, Virginia
Primary pollutant: Ozone
#200Clark, Illinois
Primary pollutant: Ozone
Frequently Asked Questions
What is actually changing in these cities?
Three forces drive the improvements visible on this list. First, vehicle fleets: every year the share of older, dirtier cars on the road shrinks as fleet turnover replaces them with cleaner Tier 3 vehicles and EVs. Second, power generation: coal plants have retired in large numbers since 2010, replaced by natural gas and renewables that emit far less SO2, NO2, and primary PM2.5. Third, industrial controls: tighter EPA standards on refineries, cement plants, and other major sources have driven sustained emission cuts. The fastest-improving city on this list, Hawaii, Hawaii, is dropping AQI by roughly 5.21 points per year — a ~52-point reduction over the dataset window.
Are wildfires undoing the progress?
In some Western metros, yes. The fastest-improving list excludes cities where wildfire smoke is reversing trend gains. Even on this list, a single bad fire season can briefly push a city back into elevated AQI territory. The improvements visible here are typically driven by year-round structural shifts (fleet turnover, plant retirements, industrial controls) that hold up in non-fire months but are temporarily masked when smoke arrives. The ten-year trend slope on this page averages out single-year smoke spikes.
Does an "improving" trend mean a city is now clean?
No — improving and clean are different things. A city with very high baseline pollution can show fast improvement without yet reaching the U.S. average; a city already at the cleanest tier may have a flat trend simply because there is little headroom left. The improvement ranking captures rate of change; the cleanest-air ranking (a separate list) captures absolute level. Among the top 50 fastest-improving cities, PM2.5 is the dominant pollutant in 31 of them — meaning that's the contaminant whose decline is doing most of the work.
Why does the average city improve at all?
National PM2.5 has dropped substantially since 2010 according to EPA AQS data, even though some Western metros saw setbacks from wildfire smoke. The dominant contributors are coal-plant retirements, vehicle-fleet turnover, and tighter EPA standards on industrial sources. The top 50 cities here average a trend slope of -2.01 AQI points per year — meaning their median AQI has been falling year after year throughout the dataset window.
How are these rankings calculated?
For each city we compute a linear-regression slope across the 10 years of EPA AQS Annual AQI by County data. Negative slope = improving (AQI declining over time). Cities are then sorted by the steepness of their negative slope. The slope contributes 30% of the city's composite Air Quality Grade; the absolute level (5-year median AQI) is the largest factor at 40%. Full math at /methodology.
How These Ranks Are Calculated
Trend slope is computed by linear regression across the 10 years of EPA AQS Annual AQI by County data for each city. Negative slope = improving (AQI declining over time). The slope contributes 30% of the composite Air Quality Grade; the absolute level (5-year median AQI) is the largest factor at 40%. Read the full methodology.
Fastest-improving air quality cities in America — top 200 ranked by 10-year AQI trend slope from EPA AQS Annual AQI by County data.