Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Kentucky

Counties in Kentucky by share of days with good air quality (US EPA AQI), 2004

Harlan County had the highest share of days with good air quality (US EPA AQI) of 36 counties in 2004, at 100%. Jefferson County had the lowest, at 18.9%. The median was 69.3%. Source: EPA.

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Highest100Harlan County
Lowest18.9Jefferson County
Median69.336 counties

Map of counties, 2004

Bell County: 69.2 %Boone County: 84.9 %Boyd County: 64 %Bullitt County: 70 %Campbell County: 64.9 %Carter County: 70.3 %Christian County: 52.5 %Daviess County: 68.9 %Edmonson County: 65.5 %Fayette County: 66.4 %Franklin County: 34.8 %Graves County: 85.3 %Greenup County: 75.5 %Hancock County: 82 %Hardin County: 61.4 %Harlan County: 100 %Henderson County: 68.7 %Jefferson County: 18.9 %Jessamine County: 81.8 %Kenton County: 53.8 %Laurel County: 23.1 %Livingston County: 74.6 %McCracken County: 66.1 %McLean County: 75.9 %Madison County: 35.8 %Marshall County: 100 %Morgan County: 86 %Oldham County: 71.7 %Perry County: 65.5 %Pike County: 69.4 %Pulaski County: 80.4 %Scott County: 94.6 %Simpson County: 74.7 %Trigg County: 68.8 %Warren County: 65 %Washington County: 83.7 %
  • Under 60
  • 60 to 66
  • 66 to 69
  • 69 to 75
  • 75 to 84
  • 84 and over
  • No data
%, 2004. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2004

Harlan County: 100 %Harlan County100Marshall County: 100 %Marshall County100Scott County: 94.6 %Scott County94.6Morgan County: 86 %Morgan County86Graves County: 85.3 %Graves County85.3Boone County: 84.9 %Boone County84.9Washington County: 83.7 %Washington County83.7Hancock County: 82 %Hancock County82Jessamine County: 81.8 %Jessamine County81.8Pulaski County: 80.4 %Pulaski County80.4McLean County: 75.9 %McLean County75.9Greenup County: 75.5 %Greenup County75.5Simpson County: 74.7 %Simpson County74.7Livingston County: 74.6 %Livingston County74.6Oldham County: 71.7 %Oldham County71.7Carter County: 70.3 %Carter County70.3Bullitt County: 70 %Bullitt County70Pike County: 69.4 %Pike County69.4Bell County: 69.2 %Bell County69.2Daviess County: 68.9 %Daviess County68.9Trigg County: 68.8 %Trigg County68.8Henderson County: 68.7 %Henderson County68.7Fayette County: 66.4 %Fayette County66.4McCracken County: 66.1 %McCracken County66.1Edmonson County: 65.5 %Edmonson County65.5Perry County: 65.5 %Perry County65.5Warren County: 65 %Warren County65Campbell County: 64.9 %Campbell County64.9Boyd County: 64 %Boyd County64Hardin County: 61.4 %Hardin County61.4Kenton County: 53.8 %Kenton County53.8Christian County: 52.5 %Christian County52.5Madison County: 35.8 %Madison County35.8Franklin County: 34.8 %Franklin County34.8Laurel County: 23.1 %Laurel County23.1Jefferson County: 18.9 %Jefferson County18.9Harlan County: 100 %Harlan County100Marshall County: 100 %Marshall County100Scott County: 94.6 %Scott County94.6Morgan County: 86 %Morgan County86Graves County: 85.3 %Graves County85.3Boone County: 84.9 %Boone County84.9Washington County: 83.7 %Washington County83.7Hancock County: 82 %Hancock County82Jessamine County: 81.8 %Jessamine County81.8Pulaski County: 80.4 %Pulaski County80.4McLean County: 75.9 %McLean County75.9Greenup County: 75.5 %Greenup County75.5Simpson County: 74.7 %Simpson County74.7Livingston County: 74.6 %Livingston County74.6Oldham County: 71.7 %Oldham County71.7Carter County: 70.3 %Carter County70.3Bullitt County: 70 %Bullitt County70Pike County: 69.4 %Pike County69.4Bell County: 69.2 %Bell County69.2Daviess County: 68.9 %Daviess County68.9Trigg County: 68.8 %Trigg County68.8Henderson County: 68.7 %Henderson County68.7Fayette County: 66.4 %Fayette County66.4McCracken County: 66.1 %McCracken County66.1Edmonson County: 65.5 %Edmonson County65.5Perry County: 65.5 %Perry County65.5Warren County: 65 %Warren County65Campbell County: 64.9 %Campbell County64.9Boyd County: 64 %Boyd County64Hardin County: 61.4 %Hardin County61.4Kenton County: 53.8 %Kenton County53.8Christian County: 52.5 %Christian County52.5Madison County: 35.8 %Madison County35.8Franklin County: 34.8 %Franklin County34.8Laurel County: 23.1 %Laurel County23.1Jefferson County: 18.9 %Jefferson County18.9
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2004 (%)Change on 2003
1Harlan County1000 pts
1Marshall County1000 pts
3Scott County94.6+7.3 pts
4Morgan County86+6.6 pts
5Graves County85.3+20 pts
6Boone County84.9+8.5 pts
7Washington County83.7+7.6 pts
8Hancock County82+20.4 pts
9Jessamine County81.8+9.7 pts
10Pulaski County80.4+2.3 pts
11McLean County75.9+13.5 pts
12Greenup County75.5+8.3 pts
13Simpson County74.7+9.4 pts
14Livingston County74.6+16.9 pts
15Oldham County71.7+2.7 pts
16Carter County70.3+10.6 pts
17Bullitt County70+3.4 pts
18Pike County69.4-4 pts
19Bell County69.2+8.8 pts
20Daviess County68.9+2.6 pts
21Trigg County68.8+3.9 pts
22Henderson County68.7+9.7 pts
23Fayette County66.4+7.5 pts
24McCracken County66.1+2 pts
25Edmonson County65.5-0.1 pts
25Perry County65.5-0.9 pts
27Warren County65+5.9 pts
28Campbell County64.9+1 pts
29Boyd County64+8.8 pts
30Hardin County61.4+9.3 pts
31Kenton County53.8-6.4 pts
32Christian County52.5+8 pts
33Madison County35.8+5.6 pts
34Franklin County34.8+1.2 pts
35Laurel County23.1+5.1 pts
36Jefferson County18.9+5.5 pts

Other periods

About this ranking

Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.

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 2004 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: good days as a share of days with an AQI, calculated with stored counts. 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: good days as a share of days with an AQI, calculated with stored counts (Counties in Kentucky by share of days with good air quality (US EPA AQI), 2004) [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: good days as a share of days with an AQI, calculated with stored counts, Counties in Kentucky by share of days with good air quality (US EPA AQI), 2004. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/good-air-quality-days-share/kentucky-counties. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Counties in Kentucky by share of days with good air quality (US EPA AQI), 2004. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/good-air-quality-days-share/kentucky-counties.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Kentucky by share of days with good air quality (US EPA AQI), 2004 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/kentucky-counties (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_kentucky_by_2004,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Kentucky by share of days with good air quality (US EPA AQI), 2004}},
  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/good-air-quality-days-share/kentucky-counties. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. 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: good days as a share of days with an AQI, calculated with stored counts: Counties in Kentucky by share of days with good air quality (US EPA AQI), 2004
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/good-air-quality-days-share/kentucky-counties
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/kentucky-counties.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. 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 share of days with good air quality (US EPA AQI)?

Harlan County, with 100% in 2004, according to EPA.

Which county has the lowest share of days with good air quality (US EPA AQI)?

Jefferson County, with 18.9% in 2004.

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: good days as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 19 counties have no value for 2004 and are not ranked.

Share of days with good air quality (US EPA AQI): other rankings

Counties in Kentucky: more rankings