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

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

Christian County had the highest median Air Quality Index (US EPA) of 36 counties in 1997, at 48. Marshall County had the lowest, at 16. The median was 37. Source: the U.S. Environmental Protection Agency.

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Highest48Christian County
Lowest16Marshall County
Median3736 counties

Map of counties, 1997

Bell County: 34 indexBoone County: 40 indexBoyd County: 37 indexBullitt County: 35 indexCampbell County: 35 indexChristian County: 48 indexDaviess County: 35 indexEdmonson County: 44 indexFayette County: 37 indexFloyd County: 18 indexGraves County: 40 indexGreenup County: 40 indexHancock County: 45 indexHardin County: 36 indexHarlan County: 20 indexHenderson County: 36 indexJefferson County: 42 indexJessamine County: 41 indexKenton County: 36 indexLawrence County: 31 indexLivingston County: 44 indexMcCracken County: 35 indexMcLean County: 42 indexMadison County: 20 indexMarshall County: 16 indexMorgan County: 41 indexOldham County: 43 indexPerry County: 36 indexPike County: 38 indexPulaski County: 40 indexScott County: 41 indexSimpson County: 36 indexTrigg County: 41 indexWarren County: 17 indexWashington County: 42 indexWhitley County: 22 index
  • Under 29
  • 29 to 36
  • 36 to 37
  • 37 to 40
  • 40 to 42
  • 42 and over
  • No data
index, 1997. 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, 1997

Christian County: 48 indexChristian County48Hancock County: 45 indexHancock County45Edmonson County: 44 indexEdmonson County44Livingston County: 44 indexLivingston County44Oldham County: 43 indexOldham County43Jefferson County: 42 indexJefferson County42McLean County: 42 indexMcLean County42Washington County: 42 indexWashington County42Jessamine County: 41 indexJessamine County41Morgan County: 41 indexMorgan County41Scott County: 41 indexScott County41Trigg County: 41 indexTrigg County41Boone County: 40 indexBoone County40Graves County: 40 indexGraves County40Greenup County: 40 indexGreenup County40Pulaski County: 40 indexPulaski County40Pike County: 38 indexPike County38Boyd County: 37 indexBoyd County37Fayette County: 37 indexFayette County37Hardin County: 36 indexHardin County36Henderson County: 36 indexHenderson County36Kenton County: 36 indexKenton County36Perry County: 36 indexPerry County36Simpson County: 36 indexSimpson County36Bullitt County: 35 indexBullitt County35Campbell County: 35 indexCampbell County35Daviess County: 35 indexDaviess County35McCracken County: 35 indexMcCracken County35Bell County: 34 indexBell County34Lawrence County: 31 indexLawrence County31Whitley County: 22 indexWhitley County22Harlan County: 20 indexHarlan County20Madison County: 20 indexMadison County20Floyd County: 18 indexFloyd County18Warren County: 17 indexWarren County17Marshall County: 16 indexMarshall County16Christian County: 48 indexChristian County48Hancock County: 45 indexHancock County45Edmonson County: 44 indexEdmonson County44Livingston County: 44 indexLivingston County44Oldham County: 43 indexOldham County43Jefferson County: 42 indexJefferson County42McLean County: 42 indexMcLean County42Washington County: 42 indexWashington County42Jessamine County: 41 indexJessamine County41Morgan County: 41 indexMorgan County41Scott County: 41 indexScott County41Trigg County: 41 indexTrigg County41Boone County: 40 indexBoone County40Graves County: 40 indexGraves County40Greenup County: 40 indexGreenup County40Pulaski County: 40 indexPulaski County40Pike County: 38 indexPike County38Boyd County: 37 indexBoyd County37Fayette County: 37 indexFayette County37Hardin County: 36 indexHardin County36Henderson County: 36 indexHenderson County36Kenton County: 36 indexKenton County36Perry County: 36 indexPerry County36Simpson County: 36 indexSimpson County36Bullitt County: 35 indexBullitt County35Campbell County: 35 indexCampbell County35Daviess County: 35 indexDaviess County35McCracken County: 35 indexMcCracken County35Bell County: 34 indexBell County34Lawrence County: 31 indexLawrence County31Whitley County: 22 indexWhitley County22Harlan County: 20 indexHarlan County20Madison County: 20 indexMadison County20Floyd County: 18 indexFloyd County18Warren County: 17 indexWarren County17Marshall County: 16 indexMarshall County16
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties1997
index		Change on 1996
1Christian County48+4
2Hancock County450
3Edmonson County440
3Livingston County440
5Oldham County43-1
6Jefferson County420
6McLean County42-3
6Washington County42-3
9Jessamine County41-1
9Morgan County41-2
9Scott County41-3
9Trigg County41-3
13Boone County400
13Graves County40-3
13Greenup County40-2
13Pulaski County40+2
17Pike County38-3
18Boyd County37-1
18Fayette County37+2
20Hardin County36-8
20Henderson County36-5
20Kenton County36-3
20Perry County36+2
20Simpson County36-3
25Bullitt County350
25Campbell County35-1
25Daviess County35+1
25McCracken County35+2
29Bell County34+2
30Lawrence County31-5
31Whitley County22+4
32Harlan County20-2
32Madison County20-2
34Floyd County18-1
35Warren County170
36Marshall County16-6

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. 19 counties with data in other periods have no value for 1997 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 Kentucky by median Air Quality Index (US EPA), 1997) [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 Kentucky by median Air Quality Index (US EPA), 1997. 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/kentucky-counties?period=1997. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Counties in Kentucky by median Air Quality Index (US EPA), 1997. 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/kentucky-counties?period=1997.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Kentucky by median Air Quality Index (US EPA), 1997 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/kentucky-counties?period=1997 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_kentucky_by_1997,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Kentucky by median Air Quality Index (US EPA), 1997}},
  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/kentucky-counties?period=1997. 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 Kentucky by median Air Quality Index (US EPA), 1997
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/kentucky-counties?period=1997
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/kentucky-counties?period=1997.
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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Questions

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

Christian County, with 48 in 1997, according to the U.S. Environmental Protection Agency.

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

Marshall County, with 16 in 1997.

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. 19 counties have no value for 1997 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Kentucky: more rankings