Is the Air Getting Better or Worse?
10-year air quality trends for 1,020 US cities. Every city gets an Air Quality Grade from A to F based on real EPA data.
Cleanest Air in America
View all →#1Caguas, Puerto Rico
Primary pollutant: NO2
#2Alexandria City, Virginia
Primary pollutant: PM10
#3Cook, Minnesota
Primary pollutant: PM2.5
#4San Juan, Puerto Rico
Primary pollutant: CO
#5Carbon, Wyoming
Primary pollutant: Ozone
#6Monroe, Michigan
Primary pollutant: PM10
#7Juncos, Puerto Rico
Primary pollutant: Ozone
#8Matanuska-Susitna, Alaska
Primary pollutant: PM2.5
#9Uinta, Wyoming
Primary pollutant: Ozone
#10Adjuntas, Puerto Rico
Primary pollutant: PM2.5
Worst Air Quality in America
View all →#1Maricopa, Arizona
Primary pollutant: Ozone
#2BAJA CALIFORNIA NORTE, Country Of Mexico
Primary pollutant: PM2.5
#3Inyo, California
Primary pollutant: Ozone
#4San Bernardino, California
Primary pollutant: Ozone
#5Los Angeles, California
Primary pollutant: PM2.5
#6Riverside, California
Primary pollutant: Ozone
#7San Diego, California
Primary pollutant: PM2.5
#8Plumas, California
Primary pollutant: PM2.5
#9Tulare, California
Primary pollutant: Ozone
#10Harris, Texas
Primary pollutant: PM2.5
Browse by State
California
53 monitored areas
Texas
42 monitored areas
Ohio
40 monitored areas
Pennsylvania
40 monitored areas
Florida
39 monitored areas
North Carolina
37 monitored areas
Indiana
36 monitored areas
Colorado
32 monitored areas
Virginia
32 monitored areas
Washington
30 monitored areas
New York
29 monitored areas
Georgia
29 monitored areas
Frequently Asked Questions
What is an Air Quality Grade?
The Air Quality Grade is AirHistory's scoring system that rates cities from A (cleanest) to F (most polluted) based on four factors: 5-year average AQI (40%), whether air quality is improving or worsening (30%), number of unhealthy days per year (20%), and the dominant pollutant type (10%).
Where does this data come from?
All data comes from the EPA's Air Quality System (AQS), which collects ambient air quality data from monitoring stations across the country. We use the annual AQI by county dataset, which covers 2014 through 2023 — a full decade of air quality measurements.
What is AQI?
The Air Quality Index (AQI) is the EPA's standardized measure for reporting air quality. An AQI of 0-50 is "Good," 51-100 is "Moderate," and above 100 is progressively unhealthy. AQI accounts for five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide.
Why trends matter more than today's reading
Real-time AQI can swing wildly due to weather, wildfires, or seasonal changes. The 10-year trend tells you whether a city's air quality is fundamentally improving or declining — a much better signal for health decisions and relocation planning.