EnviroNearby

DeKalb County, Tennessee air quality history

Daily Air Quality Index summaries from EPA monitors in DeKalb, Tennessee, 1988–2025.

97%
Good days in 2025
34
Median daily AQI, 2025
0
Days above 100 in 2025
357
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for DeKalb, Tennessee on 357 days. 345 of those days (97%) were in the Good range, and the median daily AQI was 34. That median is lower than the typical monitored county in Tennessee (median 39 across 23 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 357 days. Across the years with fuller monitoring, the share of Good days rose: an average of 71% in 1990–1992 versus 95% in 2023–2025.

Years with fewer than 120 monitored days (1988) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1988: Good 30 of 31 days1988: Moderate 1 of 31 days19881990: Good 225 of 358 days1990: Moderate 103 of 358 days1990: Unhealthy for Sensitive Groups 29 of 358 days1990: Unhealthy 1 of 358 days1991: Good 230 of 351 days1991: Moderate 93 of 351 days1991: Unhealthy for Sensitive Groups 27 of 351 days1991: Unhealthy 1 of 351 days1992: Good 301 of 360 days1992: Moderate 53 of 360 days1992: Unhealthy for Sensitive Groups 4 of 360 days1992: Unhealthy 2 of 360 days1993: Good 236 of 345 days1993: Moderate 84 of 345 days1993: Unhealthy for Sensitive Groups 24 of 345 days1993: Unhealthy 1 of 345 days1994: Good 267 of 348 days1994: Moderate 72 of 348 days1994: Unhealthy for Sensitive Groups 7 of 348 days1994: Unhealthy 2 of 348 days19941995: Good 158 of 271 days1995: Moderate 95 of 271 days1995: Unhealthy for Sensitive Groups 18 of 271 days1996: Good 145 of 209 days1996: Moderate 55 of 209 days1996: Unhealthy for Sensitive Groups 8 of 209 days1996: Unhealthy 1 of 209 days1997: Good 250 of 351 days1997: Moderate 87 of 351 days1997: Unhealthy for Sensitive Groups 12 of 351 days1997: Unhealthy 2 of 351 days1998: Good 253 of 353 days1998: Moderate 74 of 353 days1998: Unhealthy for Sensitive Groups 25 of 353 days1998: Unhealthy 1 of 353 days1999: Good 215 of 350 days1999: Moderate 95 of 350 days1999: Unhealthy for Sensitive Groups 36 of 350 days1999: Unhealthy 4 of 350 days19992000: Good 248 of 350 days2000: Moderate 78 of 350 days2000: Unhealthy for Sensitive Groups 23 of 350 days2000: Unhealthy 1 of 350 days2001: Good 273 of 361 days2001: Moderate 79 of 361 days2001: Unhealthy for Sensitive Groups 9 of 361 days2002: Good 291 of 360 days2002: Moderate 56 of 360 days2002: Unhealthy for Sensitive Groups 12 of 360 days2002: Unhealthy 1 of 360 days2003: Good 296 of 355 days2003: Moderate 52 of 355 days2003: Unhealthy for Sensitive Groups 6 of 355 days2003: Unhealthy 1 of 355 days2004: Good 318 of 350 days2004: Moderate 31 of 350 days2004: Unhealthy for Sensitive Groups 1 of 350 days20042005: Good 287 of 357 days2005: Moderate 64 of 357 days2005: Unhealthy for Sensitive Groups 6 of 357 days2006: Good 281 of 356 days2006: Moderate 73 of 356 days2006: Unhealthy for Sensitive Groups 2 of 356 days2007: Good 255 of 365 days2007: Moderate 101 of 365 days2007: Unhealthy for Sensitive Groups 9 of 365 days2008: Good 304 of 362 days2008: Moderate 58 of 362 days2009: Good 294 of 336 days2009: Moderate 42 of 336 days20092010: Good 297 of 350 days2010: Moderate 48 of 350 days2010: Unhealthy for Sensitive Groups 5 of 350 days2011: Good 314 of 350 days2011: Moderate 36 of 350 days2012: Good 269 of 313 days2012: Moderate 39 of 313 days2012: Unhealthy for Sensitive Groups 4 of 313 days2012: Unhealthy 1 of 313 days2013: Good 332 of 346 days2013: Moderate 14 of 346 days2014: Good 340 of 359 days2014: Moderate 19 of 359 days20142015: Good 336 of 353 days2015: Moderate 17 of 353 days2016: Good 330 of 351 days2016: Moderate 21 of 351 days2017: Good 349 of 363 days2017: Moderate 14 of 363 days2018: Good 331 of 348 days2018: Moderate 17 of 348 days2019: Good 335 of 363 days2019: Moderate 28 of 363 days20192020: Good 336 of 341 days2020: Moderate 5 of 341 days2021: Good 349 of 363 days2021: Moderate 14 of 363 days2022: Good 348 of 359 days2022: Moderate 11 of 359 days2023: Good 333 of 352 days2023: Moderate 19 of 352 days2024: Good 312 of 336 days2024: Moderate 24 of 336 days20242025: Good 345 of 357 days2025: Moderate 12 of 357 days2025
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001501988: 90th percentile AQI 421990: 90th percentile AQI 1001991: 90th percentile AQI 931992: 90th percentile AQI 641993: 90th percentile AQI 901994: 90th percentile AQI 771995: 90th percentile AQI 931996: 90th percentile AQI 871997: 90th percentile AQI 841998: 90th percentile AQI 901999: 90th percentile AQI 1052000: 90th percentile AQI 902001: 90th percentile AQI 712002: 90th percentile AQI 772003: 90th percentile AQI 642004: 90th percentile AQI 502005: 90th percentile AQI 712006: 90th percentile AQI 642007: 90th percentile AQI 772008: 90th percentile AQI 612009: 90th percentile AQI 542010: 90th percentile AQI 612011: 90th percentile AQI 512012: 90th percentile AQI 582013: 90th percentile AQI 472014: 90th percentile AQI 482015: 90th percentile AQI 462016: 90th percentile AQI 492017: 90th percentile AQI 462018: 90th percentile AQI 462019: 90th percentile AQI 492020: 90th percentile AQI 442021: 90th percentile AQI 462022: 90th percentile AQI 452023: 90th percentile AQI 472024: 90th percentile AQI 492025: 90th percentile AQI 461988: Median AQI 291990: Median AQI 451991: Median AQI 421992: Median AQI 361993: Median AQI 401994: Median AQI 411995: Median AQI 461996: Median AQI 421997: Median AQI 421998: Median AQI 421999: Median AQI 442000: Median AQI 422001: Median AQI 402002: Median AQI 382003: Median AQI 382004: Median AQI 352005: Median AQI 392006: Median AQI 392007: Median AQI 432008: Median AQI 392009: Median AQI 352010: Median AQI 382011: Median AQI 382012: Median AQI 392013: Median AQI 362014: Median AQI 352015: Median AQI 352016: Median AQI 372017: Median AQI 362018: Median AQI 332019: Median AQI 372020: Median AQI 332021: Median AQI 352022: Median AQI 352023: Median AQI 372024: Median AQI 382025: Median AQI 34198819941999200420092014201920242025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Ozone357100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025357345120000344684Ozone
2024336312240000384977Ozone
2023352333190000374790Ozone
20223593481100003545100Ozone
2021363349140000354684Ozone
202034133650000334461Ozone
2019363335280000374980Ozone
2018348331170000334687Ozone
2017363349140000364684Ozone
2016351330210000374984Ozone
2015353336170000354677Ozone
2014359340190000354884Ozone
2013346332140000364797Ozone
20123132693941003958172Ozone
2011350314360000385184Ozone
20103502974850003861119Ozone
2009336294420000355493Ozone
2008362304580000396197Ozone
200736525510190004377140Ozone
20063562817320003964133Ozone
20053572876460003971119Ozone
20043503183110003550105Ozone
20033552965261003864159Ozone
200236029156121003877159Ozone
20013612737990004071126Ozone
200035024878231004290164Ozone
1999350215953640044105197Ozone
199835325374251004290159Ozone
199735125087122004284166Ozone
19962091455581004287156Ozone
199527115895180004693147Ozone
19943482677272004177177Ozone
199334523684241004090159Ozone
19923603015342003664156Ozone
199135123093271004293156Ozone
19903582251032910045100174Ozone
1988313010000294264Ozone

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Tennessee with a similar median AQI in 2025

All monitored counties in Tennessee

Source: U.S. EPA AirData, “Annual AQI by County” files for 1988–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem