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

Jefferson County had the highest share of days unhealthy for sensitive groups or worse (US EPA AQI) of 30 counties in 1998, at 37.2%. Washington County had the lowest, at 0%. The median was 12.6%. Source: EPA.

Highest37.2Jefferson County

Lowest0Washington County

Median12.630 counties

Map of counties, 1998

Under 0.6
0.6 to 13
13 to 18
18 to 24
24 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	Jefferson County	37.2	+11.5 pts
2	Sevier County	32.8	+9.9 pts
3	Putnam County	28	+11.7 pts
4	Hamilton County	25.4	+11.4 pts
5	Knox County	24.9	+8.2 pts
6	Williamson County	23.4	+3.6 pts
7	Anderson County	22.6	+8.3 pts
8	Blount County	21.7	+2.8 pts
9	Haywood County	19.8	+6.6 pts
10	Shelby County	18.6	+6 pts
11	Wilson County	17.2	+0.8 pts
12	Sumner County	15.5	-5.3 pts
13	Lawrence County	15.4	+7.1 pts
14	Sullivan County	15.3	+6 pts
15	Rutherford County	14.7	-2 pts
16	Davidson County	10.4	+0.8 pts
17	Claiborne County	10.3	+4.5 pts
18	DeKalb County	7.4	+3.4 pts
19	Coffee County	6.7	n/a
20	Union County	0.8	+0.5 pts
21	Bradley County	0.3	-10.2 pts
22	Dickson County	0	0 pts
22	Hamblen County	0	-11.3 pts
22	Henry County	0	0 pts
22	Madison County	0	0 pts
22	Maury County	0	0 pts
22	McMinn County	0	0 pts
22	Montgomery County	0	0 pts
22	Roane County	0	0 pts
22	Washington 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. 12 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 Tennessee 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 Tennessee 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/tennessee-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 Tennessee 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/tennessee-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 Tennessee 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/tennessee-counties?period=1998 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_tennessee_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 Tennessee 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/tennessee-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 Tennessee 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/tennessee-counties?period=1998
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/unhealthy-air-quality-days-share/tennessee-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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Rank Counties in Tennessee by share of days unhealthy for sensitive groups or worse (US EPA AQI) using official data, and cite the source.

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Questions

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

Jefferson County, with 37.2% in 1998, according to EPA.

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

Washington 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. 12 counties have no value for 1998 and are not ranked.