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 40 counties in 2003, at 63. Daviess County had the lowest, at 16. The median was 50. Source: the U.S. Environmental Protection Agency.

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Highest63Lake County
Lowest16Daviess County
Median5040 counties

Map of counties, 2003

Allen County: 54 indexBoone County: 50 indexCarroll County: 46 indexClark County: 50 indexDaviess County: 16 indexDelaware County: 51 indexDubois County: 60 indexElkhart County: 53 indexFloyd County: 52 indexGibson County: 30 indexGreene County: 49 indexHamilton County: 50 indexHancock County: 48 indexHendricks County: 41 indexHenry County: 55 indexHoward County: 56 indexHuntington County: 49 indexJackson County: 48 indexJohnson County: 50 indexKnox County: 43 indexKosciusko County: 50 indexLake County: 63 indexLaPorte County: 52 indexMadison County: 54 indexMarion County: 63 indexMorgan County: 50 indexPerry County: 23 indexPorter County: 43 indexPosey County: 47 indexPutnam County: 18 indexSt. Joseph County: 56 indexShelby County: 49 indexSpencer County: 57 indexTippecanoe County: 56 indexVanderburgh County: 55 indexVigo County: 52 indexWabash County: 37 indexWarrick County: 50 indexWashington County: 53 indexWhitley County: 30 index
  • Under 42
  • 42 to 49
  • 49 to 50
  • 50 to 52
  • 52 to 56
  • 56 and over
  • No data
index, 2003. 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, 2003

Lake County: 63 indexLake County63Marion County: 63 indexMarion County63Dubois County: 60 indexDubois County60Spencer County: 57 indexSpencer County57Howard County: 56 indexHoward County56St. Joseph County: 56 indexSt. Joseph County56Tippecanoe County: 56 indexTippecanoe County56Henry County: 55 indexHenry County55Vanderburgh County: 55 indexVanderburgh County55Allen County: 54 indexAllen County54Madison County: 54 indexMadison County54Elkhart County: 53 indexElkhart County53Washington County: 53 indexWashington County53Floyd County: 52 indexFloyd County52LaPorte County: 52 indexLaPorte County52Vigo County: 52 indexVigo County52Delaware County: 51 indexDelaware County51Boone County: 50 indexBoone County50Clark County: 50 indexClark County50Hamilton County: 50 indexHamilton County50Johnson County: 50 indexJohnson County50Kosciusko County: 50 indexKosciusko County50Morgan County: 50 indexMorgan County50Warrick County: 50 indexWarrick County50Greene County: 49 indexGreene County49Huntington County: 49 indexHuntington County49Shelby County: 49 indexShelby County49Hancock County: 48 indexHancock County48Jackson County: 48 indexJackson County48Posey County: 47 indexPosey County47Carroll County: 46 indexCarroll County46Knox County: 43 indexKnox County43Porter County: 43 indexPorter County43Hendricks County: 41 indexHendricks County41Wabash County: 37 indexWabash County37Gibson County: 30 indexGibson County30Whitley County: 30 indexWhitley County30Perry County: 23 indexPerry County23Putnam County: 18 indexPutnam County18Daviess County: 16 indexDaviess County16Lake County: 63 indexLake County63Marion County: 63 indexMarion County63Dubois County: 60 indexDubois County60Spencer County: 57 indexSpencer County57Howard County: 56 indexHoward County56St. Joseph County: 56 indexSt. Joseph County56Tippecanoe County: 56 indexTippecanoe County56Henry County: 55 indexHenry County55Vanderburgh County: 55 indexVanderburgh County55Allen County: 54 indexAllen County54Madison County: 54 indexMadison County54Elkhart County: 53 indexElkhart County53Washington County: 53 indexWashington County53Floyd County: 52 indexFloyd County52LaPorte County: 52 indexLaPorte County52Vigo County: 52 indexVigo County52Delaware County: 51 indexDelaware County51Boone County: 50 indexBoone County50Clark County: 50 indexClark County50Hamilton County: 50 indexHamilton County50Johnson County: 50 indexJohnson County50Kosciusko County: 50 indexKosciusko County50Morgan County: 50 indexMorgan County50Warrick County: 50 indexWarrick County50Greene County: 49 indexGreene County49Huntington County: 49 indexHuntington County49Shelby County: 49 indexShelby County49Hancock County: 48 indexHancock County48Jackson County: 48 indexJackson County48Posey County: 47 indexPosey County47Carroll County: 46 indexCarroll County46Knox County: 43 indexKnox County43Porter County: 43 indexPorter County43Hendricks County: 41 indexHendricks County41Wabash County: 37 indexWabash County37Gibson County: 30 indexGibson County30Whitley County: 30 indexWhitley County30Perry County: 23 indexPerry County23Putnam County: 18 indexPutnam County18Daviess County: 16 indexDaviess County16
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2003
index		Change on 2002
1Lake County63-3
1Marion County63-5
3Dubois County600
4Spencer County570
5Howard County56-3
5St. Joseph County560
5Tippecanoe County56-3
8Henry County55-3
8Vanderburgh County55+1
10Allen County54-1
10Madison County54-7
12Elkhart County53-3
12Washington County530
14Floyd County52-1
14LaPorte County52-3
14Vigo County52-6
17Delaware County51-3
18Boone County50-4
18Clark County50-8
18Hamilton County50+1
18Johnson County50-4
18Kosciusko County50n/a
18Morgan County50-8
18Warrick County50-8
25Greene County49-5
25Huntington County49+2
25Shelby County49-9
28Hancock County48-1
28Jackson County48-6
30Posey County47-4
31Carroll County46-8
32Knox County43+1
32Porter County430
34Hendricks County41-9
35Wabash County37+1
36Gibson County30+1
36Whitley County30+11
38Perry County23+3
39Putnam County180
40Daviess County16+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. 13 counties with data in other periods have no value for 2003 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), 2003) [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), 2003. 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=2003. 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), 2003. 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=2003.

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), 2003 [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=2003 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_indiana_by_2003,
  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), 2003}},
  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=2003. 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), 2003
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=2003
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/indiana-counties?period=2003.
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 63 in 2003, according to the U.S. Environmental Protection Agency.

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

Daviess County, with 16 in 2003.

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. 13 counties have no value for 2003 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Indiana: more rankings