Counties in Iowa by highest daily Air Quality Index (US EPA)

Black Hawk County had the highest highest daily Air Quality Index (US EPA) of 20 counties in 2007, at 156. Lee County had the lowest, at 97. The median was 135. Source: the U.S. Environmental Protection Agency.

Highest156Black Hawk County

Lowest97Lee County

Median13520 counties

Map of counties, 2007

Under 110
110 to 130
130 to 140
140 to 150
150 and over
No data

index, 2007. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2007

index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2007 index	Change on 2006
1	Black Hawk County	156	+54
1	Muscatine County	156	+61
3	Scott County	152	+41
4	Bremer County	151	+54
5	Harrison County	150	+28
6	Johnson County	149	+45
7	Linn County	147	+35
8	Delaware County	140	+95
9	Clinton County	136	-3
9	Story County	136	+39
11	Pottawattamie County	134	+50
12	Wright County	132	+46
13	Woodbury County	126	+36
14	Van Buren County	122	-7
15	Warren County	119	+18
16	Polk County	112	+7
17	Montgomery County	108	-11
17	Palo Alto County	108	+5
19	Cerro Gordo County	104	+9
20	Lee County	97	+47

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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. 6 counties with data in other periods have no value for 2007 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: highest 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: highest daily AQI (Counties in Iowa by highest daily Air Quality Index (US EPA), 2007) [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: highest daily AQI, Counties in Iowa by highest daily Air Quality Index (US EPA), 2007. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/iowa-counties?period=2007. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in Iowa by highest daily Air Quality Index (US EPA), 2007. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/iowa-counties?period=2007.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in Iowa by highest daily Air Quality Index (US EPA), 2007 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/iowa-counties?period=2007 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_iowa_by_2007,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Counties in Iowa by highest daily Air Quality Index (US EPA), 2007}},
  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/highest-daily-air-quality-index/iowa-counties?period=2007. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest 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: highest daily AQI: Counties in Iowa by highest daily Air Quality Index (US EPA), 2007
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/highest-daily-air-quality-index/iowa-counties?period=2007
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/iowa-counties?period=2007.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. 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 highest daily Air Quality Index (US EPA)?

Black Hawk County, with 156 in 2007, according to the U.S. Environmental Protection Agency.

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

Lee County, with 97 in 2007.

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: highest daily AQI. Retrieved 2026-10-12. 6 counties have no value for 2007 and are not ranked.