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 39 counties in 2014, at 61. Knox County had the lowest, at 34. The median was 45. Source: the U.S. Environmental Protection Agency.

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Highest61Lake County
Lowest34Knox County
Median4539 counties

Map of counties, 2014

Allen County: 55 indexBartholomew County: 43 indexBoone County: 42 indexBrown County: 39 indexCarroll County: 41 indexClark County: 54 indexDelaware County: 41 indexDubois County: 53 indexElkhart County: 58 indexFloyd County: 56 indexGreene County: 45 indexHamilton County: 48 indexHancock County: 34 indexHendricks County: 36 indexHenry County: 48 indexHoward County: 53 indexHuntington County: 35 indexJackson County: 42 indexJohnson County: 37 indexKnox County: 34 indexLake County: 61 indexLaPorte County: 45 indexMadison County: 52 indexMarion County: 58 indexMonroe County: 44 indexMontgomery County: 54 indexMorgan County: 43 indexPerry County: 45 indexPorter County: 55 indexPosey County: 43 indexSt. Joseph County: 53 indexShelby County: 42 indexSpencer County: 52 indexTippecanoe County: 46 indexVanderburgh County: 56 indexVigo County: 54 indexWabash County: 36 indexWarrick County: 44 indexWhitley County: 51 index
  • Under 40
  • 40 to 43
  • 43 to 45
  • 45 to 52
  • 52 to 55
  • 55 and over
  • No data
index, 2014. 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, 2014

Lake County: 61 indexLake County61Elkhart County: 58 indexElkhart County58Marion County: 58 indexMarion County58Floyd County: 56 indexFloyd County56Vanderburgh County: 56 indexVanderburgh County56Allen County: 55 indexAllen County55Porter County: 55 indexPorter County55Clark County: 54 indexClark County54Montgomery County: 54 indexMontgomery County54Vigo County: 54 indexVigo County54Dubois County: 53 indexDubois County53Howard County: 53 indexHoward County53St. Joseph County: 53 indexSt. Joseph County53Madison County: 52 indexMadison County52Spencer County: 52 indexSpencer County52Whitley County: 51 indexWhitley County51Hamilton County: 48 indexHamilton County48Henry County: 48 indexHenry County48Tippecanoe County: 46 indexTippecanoe County46Greene County: 45 indexGreene County45LaPorte County: 45 indexLaPorte County45Perry County: 45 indexPerry County45Monroe County: 44 indexMonroe County44Warrick County: 44 indexWarrick County44Bartholomew County: 43 indexBartholomew County43Morgan County: 43 indexMorgan County43Posey County: 43 indexPosey County43Boone County: 42 indexBoone County42Jackson County: 42 indexJackson County42Shelby County: 42 indexShelby County42Carroll County: 41 indexCarroll County41Delaware County: 41 indexDelaware County41Brown County: 39 indexBrown County39Johnson County: 37 indexJohnson County37Hendricks County: 36 indexHendricks County36Wabash County: 36 indexWabash County36Huntington County: 35 indexHuntington County35Hancock County: 34 indexHancock County34Knox County: 34 indexKnox County34Lake County: 61 indexLake County61Elkhart County: 58 indexElkhart County58Marion County: 58 indexMarion County58Floyd County: 56 indexFloyd County56Vanderburgh County: 56 indexVanderburgh County56Allen County: 55 indexAllen County55Porter County: 55 indexPorter County55Clark County: 54 indexClark County54Montgomery County: 54 indexMontgomery County54Vigo County: 54 indexVigo County54Dubois County: 53 indexDubois County53Howard County: 53 indexHoward County53St. Joseph County: 53 indexSt. Joseph County53Madison County: 52 indexMadison County52Spencer County: 52 indexSpencer County52Whitley County: 51 indexWhitley County51Hamilton County: 48 indexHamilton County48Henry County: 48 indexHenry County48Tippecanoe County: 46 indexTippecanoe County46Greene County: 45 indexGreene County45LaPorte County: 45 indexLaPorte County45Perry County: 45 indexPerry County45Monroe County: 44 indexMonroe County44Warrick County: 44 indexWarrick County44Bartholomew County: 43 indexBartholomew County43Morgan County: 43 indexMorgan County43Posey County: 43 indexPosey County43Boone County: 42 indexBoone County42Jackson County: 42 indexJackson County42Shelby County: 42 indexShelby County42Carroll County: 41 indexCarroll County41Delaware County: 41 indexDelaware County41Brown County: 39 indexBrown County39Johnson County: 37 indexJohnson County37Hendricks County: 36 indexHendricks County36Wabash County: 36 indexWabash County36Huntington County: 35 indexHuntington County35Hancock County: 34 indexHancock County34Knox County: 34 indexKnox County34
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2014
index		Change on 2013
1Lake County61+3
2Elkhart County58+4
2Marion County58-3
4Floyd County56+5
4Vanderburgh County56+1
6Allen County55+3
6Porter County55+4
8Clark County540
8Montgomery County54n/a
8Vigo County54+1
11Dubois County53-1
11Howard County53n/a
11St. Joseph County53-4
14Madison County520
14Spencer County520
16Whitley County51-3
17Hamilton County48+9
17Henry County48-1
19Tippecanoe County46-12
20Greene County45-1
20LaPorte County45-2
20Perry County45+3
23Monroe County44-2
23Warrick County440
25Bartholomew County43+8
25Morgan County430
25Posey County43+2
28Boone County42-1
28Jackson County42-1
28Shelby County42-2
31Carroll County41-2
31Delaware County410
33Brown County39n/a
34Johnson County37-5
35Hendricks County36-2
35Wabash County36+1
37Huntington County35-1
38Hancock County34-6
38Knox County34-2

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. 14 counties with data in other periods have no value for 2014 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), 2014) [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), 2014. 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=2014. 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), 2014. 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=2014.

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), 2014 [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=2014 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_indiana_by_2014,
  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), 2014}},
  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=2014. 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), 2014
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=2014
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/indiana-counties?period=2014.
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 61 in 2014, according to the U.S. Environmental Protection Agency.

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

Knox County, with 34 in 2014.

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. 14 counties have no value for 2014 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Indiana: more rankings