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

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

Oldham County had the highest median Air Quality Index (US EPA) of 38 counties in 1999, at 90. Floyd County had the lowest, at 21. The median was 49. Source: the U.S. Environmental Protection Agency.

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Highest90Oldham County
Lowest21Floyd County
Median4938 counties

Map of counties, 1999

Bell County: 39 indexBoone County: 48 indexBoyd County: 49 indexBullitt County: 49 indexCampbell County: 46 indexCarter County: 60 indexChristian County: 61 indexDaviess County: 46 indexEdmonson County: 50 indexFayette County: 50 indexFloyd County: 21 indexFranklin County: 57 indexGraves County: 64 indexGreenup County: 50 indexHancock County: 61 indexHardin County: 61 indexHarlan County: 25 indexHenderson County: 44 indexJefferson County: 68 indexJessamine County: 48 indexKenton County: 45 indexLawrence County: 26 indexLivingston County: 67 indexMcCracken County: 48 indexMcLean County: 54 indexMadison County: 58 indexMarshall County: 29 indexMorgan County: 47 indexOldham County: 90 indexPerry County: 44 indexPike County: 61 indexPulaski County: 61 indexScott County: 50 indexSimpson County: 40 indexTrigg County: 48 indexWarren County: 61 indexWashington County: 46 indexWhitley County: 23 index
  • Under 41
  • 41 to 46
  • 46 to 49
  • 49 to 56
  • 56 to 61
  • 61 and over
  • No data
index, 1999. 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, 1999

Oldham County: 90 indexOldham County90Jefferson County: 68 indexJefferson County68Livingston County: 67 indexLivingston County67Graves County: 64 indexGraves County64Christian County: 61 indexChristian County61Hancock County: 61 indexHancock County61Hardin County: 61 indexHardin County61Pike County: 61 indexPike County61Pulaski County: 61 indexPulaski County61Warren County: 61 indexWarren County61Carter County: 60 indexCarter County60Madison County: 58 indexMadison County58Franklin County: 57 indexFranklin County57McLean County: 54 indexMcLean County54Edmonson County: 50 indexEdmonson County50Fayette County: 50 indexFayette County50Greenup County: 50 indexGreenup County50Scott County: 50 indexScott County50Boyd County: 49 indexBoyd County49Bullitt County: 49 indexBullitt County49Boone County: 48 indexBoone County48Jessamine County: 48 indexJessamine County48McCracken County: 48 indexMcCracken County48Trigg County: 48 indexTrigg County48Morgan County: 47 indexMorgan County47Campbell County: 46 indexCampbell County46Daviess County: 46 indexDaviess County46Washington County: 46 indexWashington County46Kenton County: 45 indexKenton County45Henderson County: 44 indexHenderson County44Perry County: 44 indexPerry County44Simpson County: 40 indexSimpson County40Bell County: 39 indexBell County39Marshall County: 29 indexMarshall County29Lawrence County: 26 indexLawrence County26Harlan County: 25 indexHarlan County25Whitley County: 23 indexWhitley County23Floyd County: 21 indexFloyd County21Oldham County: 90 indexOldham County90Jefferson County: 68 indexJefferson County68Livingston County: 67 indexLivingston County67Graves County: 64 indexGraves County64Christian County: 61 indexChristian County61Hancock County: 61 indexHancock County61Hardin County: 61 indexHardin County61Pike County: 61 indexPike County61Pulaski County: 61 indexPulaski County61Warren County: 61 indexWarren County61Carter County: 60 indexCarter County60Madison County: 58 indexMadison County58Franklin County: 57 indexFranklin County57McLean County: 54 indexMcLean County54Edmonson County: 50 indexEdmonson County50Fayette County: 50 indexFayette County50Greenup County: 50 indexGreenup County50Scott County: 50 indexScott County50Boyd County: 49 indexBoyd County49Bullitt County: 49 indexBullitt County49Boone County: 48 indexBoone County48Jessamine County: 48 indexJessamine County48McCracken County: 48 indexMcCracken County48Trigg County: 48 indexTrigg County48Morgan County: 47 indexMorgan County47Campbell County: 46 indexCampbell County46Daviess County: 46 indexDaviess County46Washington County: 46 indexWashington County46Kenton County: 45 indexKenton County45Henderson County: 44 indexHenderson County44Perry County: 44 indexPerry County44Simpson County: 40 indexSimpson County40Bell County: 39 indexBell County39Marshall County: 29 indexMarshall County29Lawrence County: 26 indexLawrence County26Harlan County: 25 indexHarlan County25Whitley County: 23 indexWhitley County23Floyd County: 21 indexFloyd County21
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties1999
index		Change on 1998
1Oldham County90+42
2Jefferson County68+25
3Livingston County67+9
4Graves County64+13
5Christian County61+3
5Hancock County61-3
5Hardin County61+17
5Pike County61+17
5Pulaski County61+13
5Warren County61+44
11Carter County60-4
12Madison County58+38
13Franklin County57n/a
14McLean County54+3
15Edmonson County50+2
15Fayette County50+14
15Greenup County50-1
15Scott County50+6
19Boyd County49+16
19Bullitt County49+11
21Boone County48+3
21Jessamine County48+1
21McCracken County48+8
21Trigg County48+4
25Morgan County47+3
26Campbell County46+12
26Daviess County46+11
26Washington County46+2
29Kenton County45+7
30Henderson County44+5
30Perry County44+8
32Simpson County400
33Bell County39+4
34Marshall County29+5
35Lawrence County26-12
36Harlan County25+4
37Whitley County23+3
38Floyd County21+4

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. 17 counties with data in other periods have no value for 1999 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), 1999) [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), 1999. 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=1999. 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), 1999. 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=1999.

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), 1999 [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=1999 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_kentucky_by_1999,
  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), 1999}},
  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=1999. 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), 1999
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=1999
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/kentucky-counties?period=1999.
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 Kentucky 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)?

Oldham County, with 90 in 1999, according to the U.S. Environmental Protection Agency.

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

Floyd County, with 21 in 1999.

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. 17 counties have no value for 1999 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Kentucky: more rankings