Counties in Kentucky by share of days unhealthy for sensitive groups or worse (US EPA AQI)

Carter County had the highest share of days unhealthy for sensitive groups or worse (US EPA AQI) of 37 counties in 1998, at 24%. Whitley County had the lowest, at 0%. The median was 11%. Source: EPA.

Highest24Carter County

Lowest0Whitley County

Median1137 counties

Map of counties, 1998

Under 2.5
2.5 to 8.4
8.4 to 11
11 to 14
14 to 16
16 and over
No data

%, 1998. 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, 1998

%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

Rank	Counties	1998 (%)	Change on 1997
1	Carter County	24	n/a
2	Livingston County	23.3	+13.6 pts
3	Hancock County	22.9	+13.1 pts
4	Greenup County	19.5	+15.3 pts
5	Washington County	17.6	+9.5 pts
6	Oldham County	17.4	+7.1 pts
7	Christian County	16.4	+8.1 pts
8	Graves County	16.3	+11.5 pts
9	Pulaski County	16.2	+14.1 pts
10	McLean County	15.7	+8.1 pts
11	Jefferson County	15.1	+3.9 pts
12	Jessamine County	14.1	+7.4 pts
13	Trigg County	13.7	+3.8 pts
14	Edmonson County	13.5	+8.3 pts
14	Morgan County	13.5	+9.4 pts
16	McCracken County	12.6	+8.2 pts
16	Simpson County	12.6	+7.4 pts
18	Boone County	12	+5.9 pts
19	Bullitt County	11	+2.9 pts
20	Scott County	10.8	+8.5 pts
21	Lawrence County	10.4	+10 pts
22	Kenton County	9.9	+5.5 pts
23	Pike County	9.8	+9.8 pts
24	Campbell County	8.9	+4 pts
25	Hardin County	8.4	+6.3 pts
26	Daviess County	8.2	+0.5 pts
27	Fayette County	6.3	+0.8 pts
28	Henderson County	5.5	+1.4 pts
29	Bell County	4.9	+2.2 pts
30	Boyd County	4.1	+0.8 pts
31	Perry County	2.5	+2.5 pts
32	Floyd County	0	0 pts
32	Harlan County	0	0 pts
32	Madison County	0	0 pts
32	Marshall County	0	0 pts
32	Warren County	0	0 pts
32	Whitley County	0	0 pts

Other periods

About this ranking

Days with a daily Air Quality Index above 100 (unhealthy for sensitive groups, unhealthy, very unhealthy or hazardous) 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; the counts are stored with each value.

Use the share rather than the number of days to compare counties, since the days with an AQI differ. 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 1998 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: days with an AQI above 100 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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts (Counties in Kentucky by share of days unhealthy for sensitive groups or worse (US EPA AQI), 1998) [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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts, Counties in Kentucky by share of days unhealthy for sensitive groups or worse (US EPA AQI), 1998. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/unhealthy-air-quality-days-share/kentucky-counties?period=1998. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts. Counties in Kentucky by share of days unhealthy for sensitive groups or worse (US EPA AQI), 1998. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/unhealthy-air-quality-days-share/kentucky-counties?period=1998.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts, Counties in Kentucky by share of days unhealthy for sensitive groups or worse (US EPA AQI), 1998 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/unhealthy-air-quality-days-share/kentucky-counties?period=1998 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_kentucky_by_1998,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts: Counties in Kentucky by share of days unhealthy for sensitive groups or worse (US EPA AQI), 1998}},
  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/unhealthy-air-quality-days-share/kentucky-counties?period=1998. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: days with an AQI above 100 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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts: Counties in Kentucky by share of days unhealthy for sensitive groups or worse (US EPA AQI), 1998
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/unhealthy-air-quality-days-share/kentucky-counties?period=1998
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/unhealthy-air-quality-days-share/kentucky-counties?period=1998.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: days with an AQI above 100 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 unhealthy for sensitive groups or worse (US EPA AQI)?

Carter County, with 24% in 1998, according to EPA.

Which county has the lowest share of days unhealthy for sensitive groups or worse (US EPA AQI)?

Whitley County, with 0% in 1998.

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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 18 counties have no value for 1998 and are not ranked.