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

Perry County had the highest highest daily Air Quality Index (US EPA) of 37 counties in 2001, at 251. Whitley County had the lowest, at 41. The median was 155. Source: the U.S. Environmental Protection Agency.

Highest251Perry County

Lowest41Whitley County

Median15537 counties

Map of counties, 2001

Under 130
130 to 140
140 to 160
160 to 170
170 and over
No data

index, 2001. 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, 2001

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

Full ranking

Rank	Counties	2001 index	Change on 2000
1	Perry County	251	+83
2	Bullitt County	187	+26
2	Campbell County	187	-5
4	Muhlenberg County	185	n/a
5	Kenton County	174	-21
6	Daviess County	172	+53
6	Warren County	172	-10
8	Hancock County	169	+26
9	Greenup County	166	+16
9	McLean County	166	+30
9	Oldham County	166	-8
9	Simpson County	166	-6
13	Boyd County	164	+14
13	Fayette County	164	+5
15	Hardin County	161	-18
16	Bell County	159	-31
16	Christian County	159	0
18	McCracken County	156	-46
19	Jefferson County	155	-37
20	Edmonson County	154	-28
20	Henderson County	154	+4
20	Livingston County	154	-28
23	Boone County	150	-29
24	Trigg County	147	-32
25	Franklin County	144	+22
26	Washington County	140	-11
27	Madison County	138	-20
28	Morgan County	136	-11
28	Pike County	136	-35
30	Jessamine County	133	-28
31	Carter County	130	-23
32	Pulaski County	129	-40
33	Graves County	126	-84
34	Scott County	100	-19
35	Harlan County	64	-49
36	Marshall County	49	-4
37	Whitley County	41	-48

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 2001 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), 2001) [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), 2001. 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=2001. 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), 2001. 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=2001.

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), 2001 [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=2001 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_kentucky_by_2001,
  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), 2001}},
  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=2001. 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), 2001
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=2001
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/kentucky-counties?period=2001.
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)?

Perry County, with 251 in 2001, according to the U.S. Environmental Protection Agency.

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

Whitley County, with 41 in 2001.

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 2001 and are not ranked.