Counties Tracked
995
EPA AQS active monitors
EPA Air Quality System · 995 counties · 2020-2024
How clean is the air
where you live?
AQI summaries, pollutant breakdowns, and good-day trends for 995 U.S. counties, 501 metros, and 53 states, direct from EPA AQS.
- Counties monitored
- 995
- Metro areas
- 501
- States covered
- 53
- Years of data
- 2020-2024
- Good · 1,879 d · 100.0%
Metro Areas
501
MSA-level aggregation
Avg Median AQI
39
Good
Avg Good Days
75.4%
Share of monitored days at AQI ≤50
5.4pp vs 70% benchmark
National avg good-day share 75.4%
EPA NAAQS attainment goal
Share of monitored days at AQI 0-50 (Good band) averaged across all counties.
Coverage of US counties 31.6%
Target
995 of 3,144 U.S. counties have an active EPA AQS monitor.
Cleanest and most-polluted counties
View all rankings →Cleanest air by typical AQI
Most polluted by typical AQI
How EPA monitoring is distributed
Air-quality data isn't uniform, counties with denser monitoring networks (urban, attainment-classified, or industrial) feed more readings into the AQS database than rural counties. This grid shows where EPA AQS monitors actively report, color-encoded by the share of monitored days that fell in the Good band (AQI 0-50). Sparse coverage is itself a finding: 2,200+ U.S. counties have no active monitor, and what we don't measure, we cannot regulate.
States by Air Quality
View all Scale: 57.4%–65.6% 65.6%–73.8% 73.8%–82.0% 82.0%–90.2% 90.2%–98.4%
Cleanest states right now
Hawaii
98.4%3 counties · Avg AQI 24
Maine
90.2%11 counties · Avg AQI 34
Alaska
89.3%8 counties · Avg AQI 21
Vermont
88.8%4 counties · Avg AQI 31
Rhode Island
87.1%3 counties · Avg AQI 35
New Hampshire
87.0%7 counties · Avg AQI 37
Virginia
86.8%30 counties · Avg AQI 35
Massachusetts
85.8%13 counties · Avg AQI 37
Puerto Rico
85.7%8 counties · Avg AQI 21
Washington
85.4%31 counties · Avg AQI 28
Explore More
Air Quality Guides
Learn how to read and use air quality data from official EPA sources.
Understanding the AQI
What each level means and when to limit outdoor activity.
5 Common Air Pollutants
Ozone, PM2.5, PM10, NO₂, and CO, where they come from and why they matter.
Best & Worst Air Quality
Which US counties have the cleanest and most polluted air.
Best & Worst City Air
Metro rankings and what drives urban air quality.
Air Pollution & Health
Health effects and who is most at risk.
Frequently Asked Questions
What data does PlainAir provide?
PlainAir provides EPA Air Quality System data including annual AQI values for 995 counties, 501 metros, and 50 states + DC + US territories (53 jurisdictions) from 2020-2024.
What is the Air Quality Index?
The AQI is a standardized measure from 0-500 that indicates how clean or polluted the air is. Values below 50 are considered good, while values above 100 may be unhealthy.
Where does PlainAir data come from?
All data comes from the EPA Air Quality System, the official repository of ambient air quality monitoring data from state and local agencies.
Research
Original analysis from our editorial team, every statistic derived from our own database. See all research.
Research
Top 10 US Counties with Most Unhealthy Days in 2024
Explore the 10 counties like Baldwin, Alabama, with up to 77 unhealthy days in 2024, based on EPA AQS data for 995 counties, revealing key AQI trends and pollutant impacts on public health.
ResearchState Averages of Median AQI Across 2020-2024 in 53 US States
Discover how 50 states + DC + US territories (53 jurisdictions) like Alabama, with an average median AQI of 41.1, trended from 2020 to 2024 using EPA data, including pollutant days for ozone and PM2.5, affecting over 995 counties.
ResearchNational Trends in Good Days Percentage from 2020 to 2024
Analyze nationwide good days trends across 995 counties and 501 metros, with Alabama reaching 78.31% good days in 2024 and Alaska at 89.33%, drawn from EPA AQS data on AQI metrics.