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

Counties in Iowa by median Air Quality Index (US EPA), 2016

Scott County had the highest median Air Quality Index (US EPA) of 19 counties in 2016, at 60. Cerro Gordo County had the lowest, at 15. The median was 42. Source: the U.S. Environmental Protection Agency.

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Highest60Scott County
Lowest15Cerro Gordo County
Median4219 counties

Map of counties, 2016

Black Hawk County: 51 indexBremer County: 33 indexCerro Gordo County: 15 indexClinton County: 57 indexDelaware County: 31 indexHarrison County: 37 indexJohnson County: 44 indexLee County: 42 indexLinn County: 47 indexMontgomery County: 44 indexMuscatine County: 49 indexPalo Alto County: 42 indexPolk County: 44 indexPottawattamie County: 36 indexScott County: 60 indexStory County: 35 indexVan Buren County: 51 indexWarren County: 33 indexWoodbury County: 36 index
  • Under 34
  • 34 to 38
  • 38 to 44
  • 44 to 50
  • 50 and over
  • No data
index, 2016. 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, 2016

Scott County: 60 indexScott County60Clinton County: 57 indexClinton County57Black Hawk County: 51 indexBlack Hawk County51Van Buren County: 51 indexVan Buren County51Muscatine County: 49 indexMuscatine County49Linn County: 47 indexLinn County47Johnson County: 44 indexJohnson County44Montgomery County: 44 indexMontgomery County44Polk County: 44 indexPolk County44Lee County: 42 indexLee County42Palo Alto County: 42 indexPalo Alto County42Harrison County: 37 indexHarrison County37Pottawattamie County: 36 indexPottawattamie County36Woodbury County: 36 indexWoodbury County36Story County: 35 indexStory County35Bremer County: 33 indexBremer County33Warren County: 33 indexWarren County33Delaware County: 31 indexDelaware County31Cerro Gordo County: 15 indexCerro Gordo County15Scott County: 60 indexScott County60Clinton County: 57 indexClinton County57Black Hawk County: 51 indexBlack Hawk County51Van Buren County: 51 indexVan Buren County51Muscatine County: 49 indexMuscatine County49Linn County: 47 indexLinn County47Johnson County: 44 indexJohnson County44Montgomery County: 44 indexMontgomery County44Polk County: 44 indexPolk County44Lee County: 42 indexLee County42Palo Alto County: 42 indexPalo Alto County42Harrison County: 37 indexHarrison County37Pottawattamie County: 36 indexPottawattamie County36Woodbury County: 36 indexWoodbury County36Story County: 35 indexStory County35Bremer County: 33 indexBremer County33Warren County: 33 indexWarren County33Delaware County: 31 indexDelaware County31Cerro Gordo County: 15 indexCerro Gordo County15
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2016
index		Change on 2015
1Scott County60-1
2Clinton County57+1
3Black Hawk County51-5
3Van Buren County51+4
5Muscatine County49-1
6Linn County47-1
7Johnson County44-4
7Montgomery County440
7Polk County440
10Lee County42-2
10Palo Alto County42-8
12Harrison County37-3
13Pottawattamie County36-7
13Woodbury County36-2
15Story County35-1
16Bremer County33-3
16Warren County33-2
18Delaware County31-7
19Cerro Gordo County15-1

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. 7 counties with data in other periods have no value for 2016 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 Iowa by median Air Quality Index (US EPA), 2016) [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 Iowa by median Air Quality Index (US EPA), 2016. 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/iowa-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 Iowa by median Air Quality Index (US EPA), 2016. 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/iowa-counties.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Iowa by median Air Quality Index (US EPA), 2016 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/iowa-counties (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_iowa_by_2016,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Iowa by median Air Quality Index (US EPA), 2016}},
  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/iowa-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 Iowa by median Air Quality Index (US EPA), 2016
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/iowa-counties
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/iowa-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 Iowa by median Air Quality Index (US EPA) using official data, and cite the source.
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Questions

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

Scott County, with 60 in 2016, according to the U.S. Environmental Protection Agency.

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

Cerro Gordo County, with 15 in 2016.

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. 7 counties have no value for 2016 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Iowa: more rankings