Data / Rankings / Median Air Quality Index (US EPA) / Counties in Arizona

Counties in Arizona by median Air Quality Index (US EPA), 2025

Maricopa County had the highest median Air Quality Index (US EPA) of 13 counties in 2025, at 73. Navajo County had the lowest, at 13. The median was 47. Source: the U.S. Environmental Protection Agency.

Keep it in a collection in your library.
Highest73Maricopa County
Lowest13Navajo County
Median4713 counties

Map of counties, 2025

Apache County: 33 indexCochise County: 45 indexCoconino County: 46 indexGila County: 47 indexLa Paz County: 44 indexMaricopa County: 73 indexMohave County: 17 indexNavajo County: 13 indexPima County: 54 indexPinal County: 67 indexSanta Cruz County: 49 indexYavapai County: 47 indexYuma County: 48 index
  • Under 37
  • 37 to 46
  • 46 to 47
  • 47 to 52
  • 52 and over
  • No data
index, 2025. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2025

Maricopa County: 73 indexMaricopa County73Pinal County: 67 indexPinal County67Pima County: 54 indexPima County54Santa Cruz County: 49 indexSanta Cruz County49Yuma County: 48 indexYuma County48Gila County: 47 indexGila County47Yavapai County: 47 indexYavapai County47Coconino County: 46 indexCoconino County46Cochise County: 45 indexCochise County45La Paz County: 44 indexLa Paz County44Apache County: 33 indexApache County33Mohave County: 17 indexMohave County17Navajo County: 13 indexNavajo County13Maricopa County: 73 indexMaricopa County73Pinal County: 67 indexPinal County67Pima County: 54 indexPima County54Santa Cruz County: 49 indexSanta Cruz County49Yuma County: 48 indexYuma County48Gila County: 47 indexGila County47Yavapai County: 47 indexYavapai County47Coconino County: 46 indexCoconino County46Cochise County: 45 indexCochise County45La Paz County: 44 indexLa Paz County44Apache County: 33 indexApache County33Mohave County: 17 indexMohave County17Navajo County: 13 indexNavajo County13
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2025
index		Change on 2024
1Maricopa County73-4
2Pinal County67-10
3Pima County54-2
4Santa Cruz County49+6
5Yuma County48+1
6Gila County47-3
6Yavapai County470
8Coconino County460
9Cochise County45-3
10La Paz County44-3
11Apache County33+19
12Mohave County17-2
13Navajo County130

Other periods

About this ranking

Median of the daily Air Quality Index (AQI) values of a US county over the days of the year with an AQI, from the EPA AirData annual summaries.

More on how it is measured
  • The daily county AQI is the highest AQI among the monitors and pollutants reported that day (ozone, PM2.5, PM10, carbon monoxide and nitrogen dioxide).
  • Lower is cleaner: 0 to 50 is good, 51 to 100 moderate and above 100 unhealthy for sensitive groups.

United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 2 counties with data in other periods have no value for 2025 and are left out rather than filled from another source. Equal values share a rank.

How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: median daily AQI (Counties in Arizona by median Air Quality Index (US EPA), 2025) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: median daily AQI, Counties in Arizona by median Air Quality Index (US EPA), 2025. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/median-air-quality-index/arizona-counties. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Counties in Arizona by median Air Quality Index (US EPA), 2025. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/median-air-quality-index/arizona-counties.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Arizona by median Air Quality Index (US EPA), 2025 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/arizona-counties (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_arizona_by_2025,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Arizona by median Air Quality Index (US EPA), 2025}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/arizona-counties. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download\_files.html\#Annual. Retrieved 2026-10-12.},
}
RIS
TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: median daily AQI: Counties in Arizona by median Air Quality Index (US EPA), 2025
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/median-air-quality-index/arizona-counties
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/arizona-counties.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Rank Counties in Arizona by median Air Quality Index (US EPA) using official data, and cite the source.
rank_places {"indicator":"aqi_median","level":"province","within":"Arizona","limit":10}
GET https://invokely.ai/api/v1/rank?indicator=aqi_median&level=province&within=Arizona&limit=10

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Questions

Which county has the highest median Air Quality Index (US EPA)?

Maricopa County, with 73 in 2025, according to the U.S. Environmental Protection Agency.

Which county has the lowest median Air Quality Index (US EPA)?

Navajo County, with 13 in 2025.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12. 2 counties have no value for 2025 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Arizona: more rankings