Counties in Kentucky by highest daily Air Quality Index (US EPA)

Hardin County had the highest highest daily Air Quality Index (US EPA) of 37 counties in 1993, at 212. Whitley County had the lowest, at 50. The median was 154. Source: the U.S. Environmental Protection Agency.

Highest212Hardin County

Lowest50Whitley County

Median15437 counties

Map of counties, 1993

Under 61
61 to 130
130 to 150
150 to 180
180 to 190
190 and over
No data

index, 1993. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 1993

index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

Rank	Counties	1993 index	Change on 1992
1	Hardin County	212	+111
2	Jefferson County	206	+55
3	Livingston County	201	+54
4	Fayette County	197	+82
5	Campbell County	187	+44
5	Daviess County	187	+51
5	Greenup County	187	+51
8	Hancock County	182	+10
9	Kenton County	179	+32
9	Oldham County	179	+57
9	Washington County	179	+15
12	Boyd County	177	+18
12	Bullitt County	177	+77
14	Jessamine County	169	+26
14	Scott County	169	n/a
16	Henderson County	166	-11
17	Lawrence County	159	+8
18	McCracken County	154	+4
18	Simpson County	154	+11
20	McLean County	151	+11
20	Pulaski County	151	+11
22	Christian County	147	n/a
23	Boone County	136	+7
23	Edmonson County	136	+14
25	Graves County	133	+36
26	Perry County	129	-27
27	Bell County	126	-3
27	Pike County	126	+11
29	Morgan County	105	n/a
30	Trigg County	64	n/a
31	Harlan County	61	-2
32	Warren County	60	+10
33	Marshall County	57	-6
34	Carter County	52	+7
34	Madison County	52	-8
36	Floyd County	50	+5
36	Whitley County	50	+7

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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. 18 counties with data in other periods have no value for 1993 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: highest 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: highest daily AQI (Counties in Kentucky by highest daily Air Quality Index (US EPA), 1993) [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: highest daily AQI, Counties in Kentucky by highest daily Air Quality Index (US EPA), 1993. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/kentucky-counties?period=1993. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in Kentucky by highest daily Air Quality Index (US EPA), 1993. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/kentucky-counties?period=1993.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in Kentucky by highest daily Air Quality Index (US EPA), 1993 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/kentucky-counties?period=1993 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_kentucky_by_1993,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Counties in Kentucky by highest daily Air Quality Index (US EPA), 1993}},
  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/highest-daily-air-quality-index/kentucky-counties?period=1993. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest 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: highest daily AQI: Counties in Kentucky by highest daily Air Quality Index (US EPA), 1993
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/highest-daily-air-quality-index/kentucky-counties?period=1993
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/kentucky-counties?period=1993.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest 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 highest daily Air Quality Index (US EPA)?

Hardin County, with 212 in 1993, according to the U.S. Environmental Protection Agency.

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

Whitley County, with 50 in 1993.

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: highest daily AQI. Retrieved 2026-10-12. 18 counties have no value for 1993 and are not ranked.