Which county in Tennessee has the best air quality?

Based on 2024 EPA AQS data, Dyer County had the best air quality in Tennessee with a median AQI of 31 and 286 good-air days.

2024 monitoring year Public dataset EPA AQS

Tennessee Air Quality Rankings

Compiled by PlainEnviro Editorial, Environmental Data Editorial Team · July 13, 2026

County-level AQI rollup using EPA Air Quality System monitor records. Refreshed as new EPA AQS data lands.

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County-by-county air quality data for Tennessee based on EPA AQS annual AQI readings. Data covers 23 monitored counties for 2024.

Tennessee (2024): 23 counties monitored. State average median AQI: 40 (national average: 38.8). 76% of monitored days rated "Good." Most unhealthy air: Shelby County (3 days above AQI 100).

Tennessee air quality on this page is drawn from the EPA Air Quality System (AQS), which aggregates daily readings from federal, state, tribal, and local monitors into annual summaries per county. The current dataset covers 23 Tennessee counties with at least ten days of valid AQI readings in 2024, out of the state's total monitored counties.

The state-average median AQI across those counties is 40, compared with a national average of 38.8 in the same reporting period. On average, 76% of monitored days fell into the "Good" AQI bucket (0–50). The heaviest burden of unhealthy days lands on Shelby County (3 days above AQI 100), while Dyer County records the cleanest air with a median AQI of 31.

AQI values translate ambient concentrations of pollutants (ozone, PM2.5, PM10, NO₂, SO₂, CO) onto a single 0–500 scale with six health-based bands. A low median AQI reflects typical daily conditions; peak values matter separately because short-term exposure drives most acute health effects. Counties without monitors are not "clean" - they are simply unmeasured by EPA AQS. For site-specific exposure guidance, check AirNow.gov alongside the county detail links below.

Counties with Data

State Avg Median AQI

National Avg Median AQI

38.8

Avg Good Days %

76%

Which Tennessee counties have the worst air quality?

Ranked by median AQI (higher = worse). Click a county for full environmental data.

#	County	Median AQI	Good Days	Good %	Unhealthy Days	Peak AQI
1	Shelby	55	126	34%	3	159
2	Davidson	50	189	52%	0	122
3	Hamilton	48	190	54%	0	126
4	Knox	48	205	56%	0	105
5	Blount	47	221	60%	0	90
6	Sumner	45	224	63%	0	133
7	Sevier	44	289	80%	0	93
8	Williamson	43	200	84%	0	87
9	Loudon	42	286	78%	0	100
10	Wilson	41	216	88%	0	100
11	Anderson	41	221	91%	0	100
12	Sullivan	41	285	79%	0	97
13	Jefferson	40	222	91%	0	105
14	Dekalb	38	312	93%	0	77
15	Lawrence	38	272	76%	0	84
16	Claiborne	36	336	96%	0	67
17	Roane	35	285	79%	0	72
18	Maury	33	297	83%	0	83
19	Madison	33	289	81%	0	90
20	Montgomery	32	302	84%	0	79
21	Mcminn	32	281	79%	0	89
22	Putnam	32	302	84%	0	74
23	Dyer	31	286	82%	0	92

Frequently Asked Questions

What is the air quality like in Tennessee?

In 2024, Tennessee had an average median AQI of 40 across 23 monitored counties, with 76% of monitored days rated "Good" (AQI 0–50). The national average median AQI is 38.8.

Which county in Tennessee has the worst air quality?

Based on 2024 EPA AQS data, Shelby County had the most unhealthy air days in Tennessee - 3 days above AQI 100, with a median AQI of 55.

Explore More

National AQI Rankings → Tennessee Full Profile → Tennessee Water Quality →

About This Data

Air quality data is from the EPA Air Quality System (AQS), Annual AQI by County dataset. Counties with fewer than 10 monitored days are excluded. "Unhealthy days" counts days with AQI above 100 (Unhealthy for Sensitive Groups or worse). All data is for 2024.

Source: U.S. Environmental Protection Agency, Air Quality System (AQS) U.S. Environmental Protection Agency, Air Quality System (AQS)

Read our methodology - how this data is sourced, computed, and verified.

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Data sourced from the U.S. Environmental Protection Agency (EPA). See our methodology for details. Retrieved and formatted by PlainEnviro Editorial