Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Iowa

Counties in Iowa by share of days with good air quality (US EPA AQI)

Cerro Gordo County had the highest share of days with good air quality (US EPA AQI) of 19 counties in 2012, at 96.6%. Scott County had the lowest, at 18.3%. The median was 50.1%. Source: EPA.

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Highest96.6Cerro Gordo County
Lowest18.3Scott County
Median50.119 counties

Map of counties, 2012

Black Hawk County: 44.2 %Bremer County: 74.2 %Cerro Gordo County: 96.6 %Clinton County: 19.1 %Delaware County: 60.5 %Harrison County: 63.7 %Johnson County: 32.5 %Lee County: 44.1 %Linn County: 43.4 %Montgomery County: 50.1 %Muscatine County: 33.9 %Palo Alto County: 55.5 %Polk County: 46.2 %Pottawattamie County: 42.1 %Scott County: 18.3 %Story County: 81.8 %Van Buren County: 50.3 %Warren County: 74.8 %Woodbury County: 56.1 %
  • Under 39
  • 39 to 45
  • 45 to 54
  • 54 to 68
  • 68 and over
  • No data
%, 2012. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2012

Cerro Gordo County: 96.6 %Cerro Gordo County96.6Story County: 81.8 %Story County81.8Warren County: 74.8 %Warren County74.8Bremer County: 74.2 %Bremer County74.2Harrison County: 63.7 %Harrison County63.7Delaware County: 60.5 %Delaware County60.5Woodbury County: 56.1 %Woodbury County56.1Palo Alto County: 55.5 %Palo Alto County55.5Van Buren County: 50.3 %Van Buren County50.3Montgomery County: 50.1 %Montgomery County50.1Polk County: 46.2 %Polk County46.2Black Hawk County: 44.2 %Black Hawk County44.2Lee County: 44.1 %Lee County44.1Linn County: 43.4 %Linn County43.4Pottawattamie County: 42.1 %Pottawattamie County42.1Muscatine County: 33.9 %Muscatine County33.9Johnson County: 32.5 %Johnson County32.5Clinton County: 19.1 %Clinton County19.1Scott County: 18.3 %Scott County18.3Cerro Gordo County: 96.6 %Cerro Gordo County96.6Story County: 81.8 %Story County81.8Warren County: 74.8 %Warren County74.8Bremer County: 74.2 %Bremer County74.2Harrison County: 63.7 %Harrison County63.7Delaware County: 60.5 %Delaware County60.5Woodbury County: 56.1 %Woodbury County56.1Palo Alto County: 55.5 %Palo Alto County55.5Van Buren County: 50.3 %Van Buren County50.3Montgomery County: 50.1 %Montgomery County50.1Polk County: 46.2 %Polk County46.2Black Hawk County: 44.2 %Black Hawk County44.2Lee County: 44.1 %Lee County44.1Linn County: 43.4 %Linn County43.4Pottawattamie County: 42.1 %Pottawattamie County42.1Muscatine County: 33.9 %Muscatine County33.9Johnson County: 32.5 %Johnson County32.5Clinton County: 19.1 %Clinton County19.1Scott County: 18.3 %Scott County18.3
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2012 (%)Change on 2011
1Cerro Gordo County96.6-0.3 pts
2Story County81.8-10.7 pts
3Warren County74.8-16.8 pts
4Bremer County74.2-15.5 pts
5Harrison County63.7-16.1 pts
6Delaware County60.5+8.8 pts
7Woodbury County56.1-7.9 pts
8Palo Alto County55.5+2.1 pts
9Van Buren County50.3-3.4 pts
10Montgomery County50.1-4.6 pts
11Polk County46.2-3.4 pts
12Black Hawk County44.2+2.6 pts
13Lee County44.1+2.2 pts
14Linn County43.4-2.9 pts
15Pottawattamie County42.1-5 pts
16Muscatine County33.9+1.8 pts
17Johnson County32.5+6.7 pts
18Clinton County19.1-4.2 pts
19Scott County18.3+0.2 pts

Other periods

About this ranking

Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.

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 2012 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: good days as a share of days with an AQI, calculated with stored counts. 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: good days as a share of days with an AQI, calculated with stored counts (Counties in Iowa by share of days with good air quality (US EPA AQI), 2012) [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: good days as a share of days with an AQI, calculated with stored counts, Counties in Iowa by share of days with good air quality (US EPA AQI), 2012. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/good-air-quality-days-share/iowa-counties?period=2012. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Counties in Iowa by share of days with good air quality (US EPA AQI), 2012. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/good-air-quality-days-share/iowa-counties?period=2012.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Iowa by share of days with good air quality (US EPA AQI), 2012 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/iowa-counties?period=2012 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_iowa_by_2012,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Iowa by share of days with good air quality (US EPA AQI), 2012}},
  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/good-air-quality-days-share/iowa-counties?period=2012. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. 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: good days as a share of days with an AQI, calculated with stored counts: Counties in Iowa by share of days with good air quality (US EPA AQI), 2012
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/good-air-quality-days-share/iowa-counties?period=2012
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/iowa-counties?period=2012.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Questions

Which county has the highest share of days with good air quality (US EPA AQI)?

Cerro Gordo County, with 96.6% in 2012, according to EPA.

Which county has the lowest share of days with good air quality (US EPA AQI)?

Scott County, with 18.3% in 2012.

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: good days as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 7 counties have no value for 2012 and are not ranked.

Share of days with good air quality (US EPA AQI): other rankings

Counties in Iowa: more rankings