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

Counties in Missouri by median Air Quality Index (US EPA)

St. Louis city had the highest median Air Quality Index (US EPA) of 21 counties in 2020, at 54. Taney County had the lowest, at 22. The median was 38. Source: the U.S. Environmental Protection Agency.

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Highest54St. Louis city
Lowest22Taney County
Median3821 counties

Map of counties, 2020

Andrew County: 38 indexBoone County: 33 indexBuchanan County: 42 indexCallaway County: 35 indexCass County: 39 indexCedar County: 39 indexClay County: 39 indexClinton County: 37 indexGreene County: 40 indexJackson County: 51 indexJasper County: 35 indexJefferson County: 43 indexLincoln County: 37 indexMonroe County: 31 indexPerry County: 36 indexSt. Charles County: 39 indexSte. Genevieve County: 36 indexSt. Louis County: 44 indexStoddard County: 26 indexTaney County: 22 indexSt. Louis city: 54 index
  • Under 35
  • 35 to 37
  • 37 to 39
  • 39 to 42
  • 42 and over
  • No data
index, 2020. 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, 2020

St. Louis city: 54 indexSt. Louis city54Jackson County: 51 indexJackson County51St. Louis County: 44 indexSt. Louis County44Jefferson County: 43 indexJefferson County43Buchanan County: 42 indexBuchanan County42Greene County: 40 indexGreene County40Cass County: 39 indexCass County39Cedar County: 39 indexCedar County39Clay County: 39 indexClay County39St. Charles County: 39 indexSt. Charles County39Andrew County: 38 indexAndrew County38Clinton County: 37 indexClinton County37Lincoln County: 37 indexLincoln County37Perry County: 36 indexPerry County36Ste. Genevieve County: 36 indexSte. Genevieve County36Callaway County: 35 indexCallaway County35Jasper County: 35 indexJasper County35Boone County: 33 indexBoone County33Monroe County: 31 indexMonroe County31Stoddard County: 26 indexStoddard County26Taney County: 22 indexTaney County22St. Louis city: 54 indexSt. Louis city54Jackson County: 51 indexJackson County51St. Louis County: 44 indexSt. Louis County44Jefferson County: 43 indexJefferson County43Buchanan County: 42 indexBuchanan County42Greene County: 40 indexGreene County40Cass County: 39 indexCass County39Cedar County: 39 indexCedar County39Clay County: 39 indexClay County39St. Charles County: 39 indexSt. Charles County39Andrew County: 38 indexAndrew County38Clinton County: 37 indexClinton County37Lincoln County: 37 indexLincoln County37Perry County: 36 indexPerry County36Ste. Genevieve County: 36 indexSte. Genevieve County36Callaway County: 35 indexCallaway County35Jasper County: 35 indexJasper County35Boone County: 33 indexBoone County33Monroe County: 31 indexMonroe County31Stoddard County: 26 indexStoddard County26Taney County: 22 indexTaney County22
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2020
index		Change on 2019
1St. Louis city540
2Jackson County51+2
3St. Louis County44-5
4Jefferson County43+1
5Buchanan County420
6Greene County40-3
7Cass County39-3
7Cedar County39-5
7Clay County39-4
7St. Charles County39-3
11Andrew County38-2
12Clinton County37-5
12Lincoln County37-3
14Perry County36-4
14Ste. Genevieve County36-2
16Callaway County35-4
16Jasper County35-2
18Boone County33-5
19Monroe County31-4
20Stoddard County26-5
21Taney County22-4

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. 13 counties with data in other periods have no value for 2020 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 Missouri by median Air Quality Index (US EPA), 2020) [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 Missouri by median Air Quality Index (US EPA), 2020. 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/missouri-counties?period=2020. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Counties in Missouri by median Air Quality Index (US EPA), 2020. 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/missouri-counties?period=2020.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Missouri by median Air Quality Index (US EPA), 2020 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/missouri-counties?period=2020 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_missouri_by_2020,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Missouri by median Air Quality Index (US EPA), 2020}},
  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/missouri-counties?period=2020. 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 Missouri by median Air Quality Index (US EPA), 2020
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/missouri-counties?period=2020
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/missouri-counties?period=2020.
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 Missouri by median Air Quality Index (US EPA) using official data, and cite the source.
rank_places {"indicator":"aqi_median","level":"province","within":"Missouri","limit":10}
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Questions

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

St. Louis city, with 54 in 2020, according to the U.S. Environmental Protection Agency.

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

Taney County, with 22 in 2020.

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. 13 counties have no value for 2020 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Missouri: more rankings