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

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

Lake County had the highest median Air Quality Index (US EPA) of 43 counties in 2001, at 70. Wayne County had the lowest, at 15. The median was 49. Source: the U.S. Environmental Protection Agency.

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Highest70Lake County
Lowest15Wayne County
Median4943 counties

Map of counties, 2001

Allen County: 43 indexBartholomew County: 19 indexBoone County: 48 indexCarroll County: 47 indexClark County: 58 indexDaviess County: 16 indexDeKalb County: 16 indexDelaware County: 57 indexDubois County: 57 indexElkhart County: 45 indexFloyd County: 50 indexGibson County: 30 indexGreene County: 54 indexHamilton County: 49 indexHancock County: 49 indexHendricks County: 48 indexHenry County: 58 indexHoward County: 60 indexHuntington County: 46 indexJackson County: 49 indexJasper County: 15 indexJohnson County: 49 indexKnox County: 44 indexLake County: 70 indexLaPorte County: 55 indexMadison County: 59 indexMarion County: 69 indexMorgan County: 49 indexPerry County: 49 indexPorter County: 42 indexPosey County: 49 indexPutnam County: 20 indexSt. Joseph County: 43 indexShelby County: 54 indexSpencer County: 15 indexTippecanoe County: 60 indexVanderburgh County: 42 indexVigo County: 58 indexWabash County: 36 indexWarrick County: 50 indexWashington County: 55 indexWayne County: 15 indexWhitley County: 17 index
  • Under 20
  • 20 to 44
  • 44 to 49
  • 49 to 50
  • 50 to 58
  • 58 and over
  • No data
index, 2001. 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, 2001

Lake County: 70 indexLake County70Marion County: 69 indexMarion County69Howard County: 60 indexHoward County60Tippecanoe County: 60 indexTippecanoe County60Madison County: 59 indexMadison County59Clark County: 58 indexClark County58Henry County: 58 indexHenry County58Vigo County: 58 indexVigo County58Delaware County: 57 indexDelaware County57Dubois County: 57 indexDubois County57LaPorte County: 55 indexLaPorte County55Washington County: 55 indexWashington County55Greene County: 54 indexGreene County54Shelby County: 54 indexShelby County54Floyd County: 50 indexFloyd County50Warrick County: 50 indexWarrick County50Hamilton County: 49 indexHamilton County49Hancock County: 49 indexHancock County49Jackson County: 49 indexJackson County49Johnson County: 49 indexJohnson County49Morgan County: 49 indexMorgan County49Perry County: 49 indexPerry County49Posey County: 49 indexPosey County49Boone County: 48 indexBoone County48Hendricks County: 48 indexHendricks County48Carroll County: 47 indexCarroll County47Huntington County: 46 indexHuntington County46Elkhart County: 45 indexElkhart County45Knox County: 44 indexKnox County44Allen County: 43 indexAllen County43St. Joseph County: 43 indexSt. Joseph County43Porter County: 42 indexPorter County42Vanderburgh County: 42 indexVanderburgh County42Wabash County: 36 indexWabash County36Gibson County: 30 indexGibson County30Putnam County: 20 indexPutnam County20Bartholomew County: 19 indexBartholomew County19Whitley County: 17 indexWhitley County17Daviess County: 16 indexDaviess County16DeKalb County: 16 indexDeKalb County16Jasper County: 15 indexJasper County15Spencer County: 15 indexSpencer County15Wayne County: 15 indexWayne County15Lake County: 70 indexLake County70Marion County: 69 indexMarion County69Howard County: 60 indexHoward County60Tippecanoe County: 60 indexTippecanoe County60Madison County: 59 indexMadison County59Clark County: 58 indexClark County58Henry County: 58 indexHenry County58Vigo County: 58 indexVigo County58Delaware County: 57 indexDelaware County57Dubois County: 57 indexDubois County57LaPorte County: 55 indexLaPorte County55Washington County: 55 indexWashington County55Greene County: 54 indexGreene County54Shelby County: 54 indexShelby County54Floyd County: 50 indexFloyd County50Warrick County: 50 indexWarrick County50Hamilton County: 49 indexHamilton County49Hancock County: 49 indexHancock County49Jackson County: 49 indexJackson County49Johnson County: 49 indexJohnson County49Morgan County: 49 indexMorgan County49Perry County: 49 indexPerry County49Posey County: 49 indexPosey County49Boone County: 48 indexBoone County48Hendricks County: 48 indexHendricks County48Carroll County: 47 indexCarroll County47Huntington County: 46 indexHuntington County46Elkhart County: 45 indexElkhart County45Knox County: 44 indexKnox County44Allen County: 43 indexAllen County43St. Joseph County: 43 indexSt. Joseph County43Porter County: 42 indexPorter County42Vanderburgh County: 42 indexVanderburgh County42Wabash County: 36 indexWabash County36Gibson County: 30 indexGibson County30Putnam County: 20 indexPutnam County20Bartholomew County: 19 indexBartholomew County19Whitley County: 17 indexWhitley County17Daviess County: 16 indexDaviess County16DeKalb County: 16 indexDeKalb County16Jasper County: 15 indexJasper County15Spencer County: 15 indexSpencer County15Wayne County: 15 indexWayne County15
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2001
index		Change on 2000
1Lake County70+1
2Marion County69+2
3Howard County60-3
3Tippecanoe County60-1
5Madison County59+5
6Clark County58+1
6Henry County58+2
6Vigo County58+5
9Delaware County57-5
9Dubois County57-7
11LaPorte County55+5
11Washington County55n/a
13Greene County54+6
13Shelby County54+5
15Floyd County500
15Warrick County50+3
17Hamilton County49+1
17Hancock County49+4
17Jackson County49+2
17Johnson County49+1
17Morgan County490
17Perry County49+2
17Posey County49-5
24Boone County48+1
24Hendricks County48-12
26Carroll County47n/a
27Huntington County46-2
28Elkhart County45+1
29Knox County44+1
30Allen County43-1
30St. Joseph County43+1
32Porter County42-1
32Vanderburgh County42-4
34Wabash County36-2
35Gibson County30+3
36Putnam County200
37Bartholomew County190
38Whitley County17n/a
39Daviess County16-3
39DeKalb County16-6
41Jasper County15-2
41Spencer County150
41Wayne County15-6

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. 10 counties with data in other periods have no value for 2001 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 Indiana by median Air Quality Index (US EPA), 2001) [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 Indiana by median Air Quality Index (US EPA), 2001. 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/indiana-counties?period=2001. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Counties in Indiana by median Air Quality Index (US EPA), 2001. 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/indiana-counties?period=2001.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Indiana by median Air Quality Index (US EPA), 2001 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/indiana-counties?period=2001 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_indiana_by_2001,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Indiana by median Air Quality Index (US EPA), 2001}},
  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/indiana-counties?period=2001. 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 Indiana by median Air Quality Index (US EPA), 2001
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/indiana-counties?period=2001
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/indiana-counties?period=2001.
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 Indiana 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)?

Lake County, with 70 in 2001, according to the U.S. Environmental Protection Agency.

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

Wayne County, with 15 in 2001.

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. 10 counties have no value for 2001 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Indiana: more rankings