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 32 counties in 1997, at 25.7%. Washington County had the lowest, at 0%. The median was 9.5%. Source: EPA.

Highest25.7Jefferson County

Lowest0Washington County

Median9.532 counties

Map of counties, 1997

Under 0.9
0.9 to 9.4
9.4 to 14
14 to 17
17 and over
No data

%, 1997. 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, 1997

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

Full ranking

Rank	Counties	1997 (%)	Change on 1996
1	Jefferson County	25.7	-3.9 pts
2	Sevier County	22.9	-0.7 pts
3	Sumner County	20.8	-2.1 pts
4	Williamson County	19.8	+3.8 pts
5	Blount County	18.9	+3.4 pts
6	Knox County	16.7	+2.5 pts
6	Rutherford County	16.7	+6.9 pts
8	Wilson County	16.4	-0.3 pts
9	Putnam County	16.3	+16.3 pts
10	Anderson County	14.3	-3.1 pts
11	Hamilton County	14	+2.5 pts
12	Haywood County	13.2	-2.7 pts
13	Shelby County	12.6	+0.6 pts
14	Hamblen County	11.3	n/a
15	Bradley County	10.5	+10.5 pts
16	Davidson County	9.6	-1.1 pts
17	Sullivan County	9.3	+0.7 pts
18	Lawrence County	8.3	n/a
19	Claiborne County	5.8	+5.8 pts
20	DeKalb County	4	-0.3 pts
21	Humphreys County	2.2	-7.1 pts
22	Union County	0.3	+0.3 pts
23	Dickson County	0	0 pts
23	Giles County	0	-12.3 pts
23	Henry County	0	0 pts
23	Loudon County	0	-10.4 pts
23	Madison County	0	0 pts
23	Maury County	0	0 pts
23	McMinn County	0	0 pts
23	Montgomery County	0	0 pts
23	Roane County	0	0 pts
23	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. 10 counties with data in other periods have no value for 1997 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), 1997) [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), 1997. 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=1997. 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), 1997. 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=1997.

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), 1997 [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=1997 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_tennessee_by_1997,
  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), 1997}},
  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=1997. 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), 1997
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=1997
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/unhealthy-air-quality-days-share/tennessee-counties?period=1997.
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 25.7% in 1997, 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 1997.

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. 10 counties have no value for 1997 and are not ranked.