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Mapped: The Best and Worst U.S. States for Air Quality

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Mapped: The Best and Worst U.S. States for Air Quality

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Key Takeaways

  • Wyoming has the cleanest air in the U.S., with average particle pollution of just 4 µg/m³.
  • California ranks worst, at 11.7 µg/m³, partly due to frequent wildfires.
  • Nearly half of Americans live in areas with unhealthy air pollution levels.

Wyoming’s air contains less than half the particle pollution found in California.

Across the country, fine particle pollution levels range from just over 4 µg/m³ to nearly 12 µg/m³, a gap shaped by wildfire exposure, population density, and industrial activity.

This map ranks all 50 states by average particle pollution, based on EPA data from the America’s Health Rankings 2025 report.

A Breakdown of States Ranked by Air Quality

For the analysis, states were analyzed using 2022 to 2024 average fine particle pollution (µg/m³).

The U.S. average stood at 8.8 µg/m³, exceeding the World Health Organization’s (WHO) air quality guideline of 5 µg/m³. That means the average American is breathing air that falls short of global health standards.

Below, we rank states from best to worst by air pollution levels. Where does your state rank?

Rank State Fine particle pollution (µg/m³)
1 Wyoming 4.1
2 Hawaii 4.7
3 New Hampshire 5.0
4 South Dakota 5.7
5 Alaska 5.9
6 Maine 5.9
7 New Mexico 5.9
8 Colorado 6.0
9 Vermont 6.0
10 Montana 6.5
11 Nebraska 6.6
12 Rhode Island 6.7
13 Virginia 7.2
14 Maryland 7.4
15 Utah 7.5
16 Florida 7.6
17 Idaho 7.6
18 Missouri 7.6
19 Alabama 7.7
20 Massachusetts 7.7
21 Washington 7.7
22 West Virginia 7.7
23 New York 7.8
24 Tennessee 7.8
25 North Carolina 7.9
26 New Jersey 7.9
27 Connecticut 8.1
28 Kentucky 8.1
29 Oregon 8.2
30 Mississippi 8.3
31 North Dakota 8.3
32 Iowa 8.4
33 Louisiana 8.4
34 Minnesota 8.4
35 Nevada 8.4
36 South Carolina 8.4
37 Arkansas 8.5
38 Oklahoma 8.5
39 Wisconsin 8.6
40 Arizona 8.7
41 Kansas 8.7
42 Georgia 9.2
43 Texas 9.4
44 Indiana 9.5
45 Delaware 9.7
46 Ohio 9.8
47 Illinois 10.3
48 Michigan 10.4
49 Pennsylvania 11.0
50 California 11.7
-- U.S. Average 8.8

Wyoming has the best air quality in the U.S., known for its vast stretches of land and the nation’s smallest population.

Adding to this, Wyoming’s city of Casper has the lowest year-round particle pollution across U.S. metros. Cheyenne, meanwhile, ranked eighth overall.

Hawaii ranks second by particle pollution, at 4.7 µg/m³. The state’s low population density, along with strong winds and rainfall, plays a key role in its air quality. While rain helps to clear away pollutants, trade winds bring in fresh air and mitigate the accumulation of air pollutants.

Overall, just three states—Wyoming, Hawaii, and New Hampshire—have air quality that falls within WHO’s guidelines.

In contrast, California has average particle pollution of 11.7 µg/m³, the worst nationwide. Moreover, 88% of Californians live in areas with unhealthy air quality. Several factors drive up pollution in the state including tailpipe emissions, high population density, and its hot climate.

States at the bottom of the rankings tend to combine large populations, dense transportation networks, and significant industrial activity. Trailing California at the bottom of the rankings are Pennsylvania, Michigan, and Illinois.

Learn More on the Voronoi App

To learn more about this topic, check out this graphic on the world’s most air-polluted cities.

Source
America
California