Best and Worst Air Quality Cities in the US [2026 Rankings]

Air Quality Varies Dramatically Across the US

If you think air quality is roughly the same everywhere in the United States, the data tells a very different story. The gap between the cleanest and most polluted American cities is enormous. Residents of the worst-ranking metro areas breathe air with PM2.5 concentrations three to five times higher than those in the cleanest cities, translating into measurable differences in respiratory disease rates, cardiovascular health, and even life expectancy.

These rankings draw on EPA monitoring data, AQI trends, and pollution measurements collected throughout 2025 and into early 2026. We evaluate cities on three key metrics: annual average PM2.5 concentration, number of unhealthy air quality days per year, and peak ozone levels during the warm season.

For real-time conditions in any of these cities, visit our city air quality pages.

The 10 Cities with the Worst Air Quality in 2026

1. Bakersfield, California

Bakersfield consistently ranks as the most polluted city in the United States, and 2026 is no exception. Sitting in the southern San Joaquin Valley, Bakersfield is trapped by mountains on three sides that prevent pollutants from dispersing. Agricultural dust, oil refining operations, and vehicle emissions combine with the valley's geography to produce dangerously high PM2.5 and ozone levels.

• •Average AQI: 89 (Moderate, bordering Unhealthy for Sensitive Groups)
• •Unhealthy air days per year: 120+
• •Primary pollutants: PM2.5, ozone

Check current conditions: California air quality

2. Fresno, California

Located 110 miles north of Bakersfield in the same San Joaquin Valley, Fresno faces nearly identical geographic and pollution challenges. Temperature inversions during winter months trap wood smoke and vehicle exhaust close to the ground, frequently pushing AQI above 150. Summer brings intense ozone formation driven by heat and agricultural emissions.

• •Average AQI: 82
• •Unhealthy air days per year: 105+
• •Primary pollutants: PM2.5, ozone

3. Visalia, California

The third San Joaquin Valley city in our top five, Visalia rounds out California's dominance of the worst air quality rankings. The Tulare County seat suffers from the same valley inversion patterns, compounded by significant agricultural activity including dairy operations that produce ammonia emissions.

• •Average AQI: 78
• •Unhealthy air days per year: 95+
• •Primary pollutants: PM2.5, ozone

4. Los Angeles, California

The nation's second-largest metro area has made remarkable progress since the smog crises of the 1970s, but Los Angeles still ranks among the most polluted cities in the country. The combination of 10+ million vehicles, port operations, industrial activity, and a basin geography that traps pollutants makes clean air an ongoing challenge.

• •Average AQI: 74
• •Unhealthy air days per year: 80+
• •Primary pollutants: Ozone, PM2.5

5. Phoenix, Arizona

Phoenix's air quality problems are driven by a combination of desert dust, extreme heat that accelerates ozone formation, and rapid population growth that has increased vehicle emissions. Summer temperatures frequently exceed 110 degrees Fahrenheit, creating ideal conditions for ground-level ozone production.

• •Average AQI: 71
• •Unhealthy air days per year: 70+
• •Primary pollutants: Ozone, PM10

Check current conditions: Arizona air quality

6. Sacramento, California

California's capital sits in the Sacramento Valley, another geographic bowl that traps pollutants. Vehicle traffic on the I-5 and I-80 corridors, combined with agricultural burning in surrounding counties, contributes to elevated PM2.5 and ozone readings, particularly in summer and fall.

• •Average AQI: 68
• •Unhealthy air days per year: 60+
• •Primary pollutants: Ozone, PM2.5

7. Houston, Texas

The nation's petrochemical capital faces air quality challenges from industrial emissions, vehicle traffic, and hot, humid summers that promote ozone formation. The Houston Ship Channel corridor is home to the largest concentration of refineries and chemical plants in the country, making certain neighborhoods significantly more polluted than others.

• •Average AQI: 65
• •Unhealthy air days per year: 55+
• •Primary pollutants: Ozone, NO2

Check current conditions: Texas air quality

8. Denver, Colorado

Denver's air quality has deteriorated noticeably over the past decade due to rapid population growth, increased vehicle miles traveled, and its high elevation, which intensifies UV radiation and accelerates ozone formation. Wildfire smoke from western fires has also become a significant seasonal contributor.

• •Average AQI: 63
• •Unhealthy air days per year: 50+
• •Primary pollutants: Ozone, PM2.5 (wildfire season)

Check current conditions: Colorado air quality

9. Salt Lake City, Utah

Winter temperature inversions are Salt Lake City's defining air quality challenge. Cold, dense air settles into the valley basin and becomes trapped by the surrounding Wasatch and Oquirrh mountain ranges, sometimes for weeks at a time. PM2.5 accumulates to unhealthy levels during these inversion events, which typically occur from December through February.

• •Average AQI: 61
• •Unhealthy air days per year: 45+
• •Primary pollutants: PM2.5 (winter), ozone (summer)

Check current conditions: Utah air quality

10. Las Vegas, Nevada

Rapid growth, desert dust, and proximity to Southern California's pollution plume contribute to Las Vegas's air quality challenges. Construction activity from ongoing development adds to particulate matter levels, and summer heat drives ozone formation.

• •Average AQI: 59
• •Unhealthy air days per year: 40+
• •Primary pollutants: Ozone, PM10

Check current conditions: Nevada air quality

The 10 Cities with the Best Air Quality in 2026

1. Honolulu, Hawaii

Surrounded by the Pacific Ocean with consistent trade winds that sweep pollutants away, Honolulu enjoys the cleanest air of any major US city. The absence of heavy industry and the island's geography create near-ideal conditions for clean air year-round.

• •Average AQI: 22
• •Unhealthy air days per year: 0-2
• •Primary advantage: Ocean winds, minimal industry

Check current conditions: Hawaii air quality

2. Burlington, Vermont

Nestled on the shores of Lake Champlain with minimal industrial activity and low population density, Burlington consistently ranks among the cleanest-air cities in the continental United States. The Green Mountains help channel clean air from northern forests through the region.

• •Average AQI: 25
• •Unhealthy air days per year: 1-3
• •Primary advantage: Low population density, minimal industry, forested surroundings

Check current conditions: Vermont air quality

3. Bangor, Maine

Northern Maine's low population density, vast forests, and distance from major industrial centers give Bangor some of the cleanest air in the country. Ocean breezes from the Atlantic further help disperse any localized pollutants.

• •Average AQI: 26
• •Unhealthy air days per year: 1-3
• •Primary advantage: Remote location, dense forests, Atlantic air flow

Check current conditions: Maine air quality

4. Cheyenne, Wyoming

Wyoming's capital benefits from constant wind, low population density, and vast open spaces. While occasional wildfire smoke can temporarily degrade air quality, Cheyenne's baseline conditions are excellent.

• •Average AQI: 27
• •Unhealthy air days per year: 2-5
• •Primary advantage: High winds, extremely low population density

Check current conditions: Wyoming air quality

5. Duluth, Minnesota

Positioned on the western tip of Lake Superior, Duluth benefits from lake breezes and its distance from major pollution sources. The surrounding boreal forests act as natural air filters, and the city's small population generates minimal vehicle and industrial emissions.

• •Average AQI: 28
• •Unhealthy air days per year: 2-4
• •Primary advantage: Lake Superior winds, forested region, low emissions

Check current conditions: Minnesota air quality

6. Bismarck, North Dakota

The Great Plains city benefits from persistent winds and extremely low population density. North Dakota's flat terrain allows pollutants to disperse quickly, and Bismarck sits far from any major industrial centers.

• •Average AQI: 29
• •Unhealthy air days per year: 2-5
• •Primary advantage: Plains winds, very low population density

Check current conditions: North Dakota air quality

7. Asheville, North Carolina

Tucked into the Blue Ridge Mountains, Asheville enjoys clean mountain air and a relatively small population. The surrounding Appalachian forests produce phytoncides that actually help clean the air, and the city has no heavy industry.

• •Average AQI: 30
• •Unhealthy air days per year: 3-6
• •Primary advantage: Mountain elevation, forest filtration, no heavy industry

Check current conditions: North Carolina air quality

8. Portland, Maine

Not to be confused with its Oregon namesake, Portland, Maine benefits from Atlantic Ocean breezes, low population density, and a lack of major industrial polluters. The city's compact size and walkability further reduce vehicle emissions.

• •Average AQI: 30
• •Unhealthy air days per year: 3-5
• •Primary advantage: Coastal location, small metro area

9. Rapid City, South Dakota

The gateway to the Black Hills enjoys excellent air quality thanks to its remote location, persistent prairie winds, and small population. The surrounding Ponderosa pine forests contribute to air filtration.

• •Average AQI: 31
• •Unhealthy air days per year: 3-6
• •Primary advantage: Remote, windy, low emissions

Check current conditions: South Dakota air quality

10. Missoula, Montana

While Missoula can experience poor air quality during summer wildfire events, its baseline air quality is excellent. The city sits in a mountain valley fed by clean air from surrounding wilderness areas, and its small population keeps emissions low during non-fire months.

• •Average AQI: 32 (excluding wildfire events)
• •Unhealthy air days per year: 5-15 (highly variable due to wildfires)
• •Primary advantage: Wilderness surroundings, small population

Check current conditions: Montana air quality

Key Patterns in the Data

Geography Is Destiny

The single biggest factor in city air quality rankings is geography. Valley cities, particularly in California's Central Valley, consistently rank worst because surrounding terrain traps pollutants. Coastal and high-plains cities with consistent winds rank best because pollutants disperse quickly.

The California Problem

California dominates the worst air quality rankings, with four of the top six most polluted cities. This is not due to a lack of environmental regulation. California has the strictest air quality laws in the nation. Rather, the state's Central Valley geography, massive population, agricultural activity, and warm climate create a uniquely challenging combination.

Wildfire Smoke Is Reshaping Rankings

Cities that traditionally had excellent air quality, such as Portland, Oregon and Seattle, Washington, now experience periodic severe pollution events from wildfire smoke. These events can push AQI above 300 for days at a time, dramatically impacting annual averages and resident health.

Visit our state-by-state air quality pages to track wildfire season conditions.

Population Growth Drives Deterioration

Fast-growing cities like Denver, Phoenix, Austin, and Boise are seeing gradual air quality deterioration as population growth increases vehicle miles traveled and construction activity. Without continued investment in public transit and clean energy, these cities will continue to slide in future rankings.

How These Rankings Affect Health Outcomes

The air quality differences between the best and worst cities translate directly into health disparities:

• •Asthma prevalence in the San Joaquin Valley is approximately 21% above the national average
• •Cardiovascular mortality is 8-12% higher in cities with the worst PM2.5 levels compared to the cleanest cities
• •Lung cancer rates are elevated in areas with chronic ozone exposure, even after controlling for smoking rates
• •Children's lung development is measurably impaired in the most polluted metro areas, with lower forced expiratory volume by age 18

These are not hypothetical risks. They represent real health outcomes affecting millions of Americans based on where they live.

What You Can Do Regardless of Where You Live

If You Live in a High-Pollution City

1. Monitor AQI daily using our city air quality pages and plan outdoor activities for lower-pollution periods
2. Invest in HEPA air purification for your home, especially bedrooms. See our air purifier guide for recommendations
3. Create a clean air room where you can retreat during poor air quality events. Follow our step-by-step guide
4. Use N95 masks during unhealthy air days, especially during wildfire events
5. Advocate for cleaner transportation and industrial emission standards in your community

If You Live in a Clean-Air City

1. Do not be complacent. Even clean-air cities can experience unhealthy episodes from wildfires, industrial accidents, or temperature inversions
2. Be prepared for wildfire smoke which can travel hundreds of miles. Keep N95 masks and a HEPA air purifier on hand
3. Support policies that maintain clean air as your city grows
4. Check AQI during summer months when ozone can elevate even in typically clean areas

If You Are Considering a Move

Air quality should be a factor in relocation decisions, especially for families with young children, older adults, or anyone managing respiratory or cardiovascular conditions. The difference between living in a top-10 cleanest city versus a top-10 most polluted city is meaningful enough to affect long-term health outcomes.

Use our compare tool to view side-by-side air quality data for cities you are considering.

Looking Ahead: 2026 and Beyond

Several trends will shape air quality rankings in coming years:

• •Electric vehicle adoption is reducing tailpipe emissions in early-adopter cities, with measurable AQI improvements expected by 2028-2030
• •Wildfire intensity continues to increase in the western US due to climate change, threatening to undo decades of pollution reduction progress
• •Industrial transitions away from fossil fuels are slowly reducing SO2 and NO2 emissions near former coal plant sites
• •Urban growth in Sun Belt cities will continue to put upward pressure on emissions unless offset by clean transportation infrastructure

We will continue to update these rankings as new data becomes available. Bookmark our air quality pages for the latest conditions in your city, and browse all state data for regional trends.

Methodology

These rankings are compiled from EPA Air Quality System monitoring data, AirNow real-time readings, and state-level monitoring networks. Annual averages are calculated from daily AQI values over the most recent 12-month period with complete data. Cities are ranked by a composite score that weights annual PM2.5 average (40%), number of unhealthy air days (35%), and peak ozone season severity (25%). Only metropolitan statistical areas with populations above 50,000 and sufficient monitoring coverage are included.

For a deeper dive into how air quality is measured and reported, read our guide on understanding AQI or visit our methodology page.