Data / Rankings / Median Air Quality Index (US EPA) / Counties in Texas

Counties in Texas by median Air Quality Index (US EPA)

Harris County had the highest median Air Quality Index (US EPA) of 41 counties in 2015, at 58. Culberson County had the lowest, at 21. The median was 42. Source: the U.S. Environmental Protection Agency.

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Highest58Harris County
Lowest21Culberson County
Median4241 counties

Map of counties, 2015

Bell County: 36 indexBexar County: 53 indexBowie County: 51 indexBrazoria County: 33 indexBrewster County: 42 indexCameron County: 48 indexCollin County: 36 indexCulberson County: 21 indexDallas County: 52 indexDenton County: 46 indexEctor County: 39 indexEllis County: 46 indexEl Paso County: 54 indexFayette County: 33 indexGalveston County: 44 indexGregg County: 33 indexHarris County: 58 indexHarrison County: 42 indexHidalgo County: 49 indexHood County: 34 indexHunt County: 33 indexJefferson County: 47 indexJohnson County: 35 indexKaufman County: 42 indexKleberg County: 44 indexMcLennan County: 42 indexMaverick County: 44 indexMontgomery County: 48 indexNavarro County: 43 indexNueces County: 48 indexOrange County: 42 indexParker County: 37 indexPolk County: 31 indexPotter County: 29 indexRandall County: 42 indexRockwall County: 36 indexSmith County: 33 indexTarrant County: 50 indexTravis County: 49 indexVictoria County: 32 indexWebb County: 49 index
  • Under 33
  • 33 to 36
  • 36 to 42
  • 42 to 46
  • 46 to 49
  • 49 and over
  • No data
index, 2015. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2015

Harris County: 58 indexHarris County58El Paso County: 54 indexEl Paso County54Bexar County: 53 indexBexar County53Dallas County: 52 indexDallas County52Bowie County: 51 indexBowie County51Tarrant County: 50 indexTarrant County50Hidalgo County: 49 indexHidalgo County49Travis County: 49 indexTravis County49Webb County: 49 indexWebb County49Cameron County: 48 indexCameron County48Montgomery County: 48 indexMontgomery County48Nueces County: 48 indexNueces County48Jefferson County: 47 indexJefferson County47Denton County: 46 indexDenton County46Ellis County: 46 indexEllis County46Galveston County: 44 indexGalveston County44Kleberg County: 44 indexKleberg County44Maverick County: 44 indexMaverick County44Navarro County: 43 indexNavarro County43Brewster County: 42 indexBrewster County42Harrison County: 42 indexHarrison County42Kaufman County: 42 indexKaufman County42McLennan County: 42 indexMcLennan County42Orange County: 42 indexOrange County42Randall County: 42 indexRandall County42Ector County: 39 indexEctor County39Parker County: 37 indexParker County37Bell County: 36 indexBell County36Collin County: 36 indexCollin County36Rockwall County: 36 indexRockwall County36Johnson County: 35 indexJohnson County35Hood County: 34 indexHood County34Brazoria County: 33 indexBrazoria County33Fayette County: 33 indexFayette County33Gregg County: 33 indexGregg County33Hunt County: 33 indexHunt County33Smith County: 33 indexSmith County33Victoria County: 32 indexVictoria County32Polk County: 31 indexPolk County31Potter County: 29 indexPotter County29Culberson County: 21 indexCulberson County21Harris County: 58 indexHarris County58El Paso County: 54 indexEl Paso County54Bexar County: 53 indexBexar County53Dallas County: 52 indexDallas County52Bowie County: 51 indexBowie County51Tarrant County: 50 indexTarrant County50Hidalgo County: 49 indexHidalgo County49Travis County: 49 indexTravis County49Webb County: 49 indexWebb County49Cameron County: 48 indexCameron County48Montgomery County: 48 indexMontgomery County48Nueces County: 48 indexNueces County48Jefferson County: 47 indexJefferson County47Denton County: 46 indexDenton County46Ellis County: 46 indexEllis County46Galveston County: 44 indexGalveston County44Kleberg County: 44 indexKleberg County44Maverick County: 44 indexMaverick County44Navarro County: 43 indexNavarro County43Brewster County: 42 indexBrewster County42Harrison County: 42 indexHarrison County42Kaufman County: 42 indexKaufman County42McLennan County: 42 indexMcLennan County42Orange County: 42 indexOrange County42Randall County: 42 indexRandall County42Ector County: 39 indexEctor County39Parker County: 37 indexParker County37Bell County: 36 indexBell County36Collin County: 36 indexCollin County36Rockwall County: 36 indexRockwall County36Johnson County: 35 indexJohnson County35Hood County: 34 indexHood County34Brazoria County: 33 indexBrazoria County33Fayette County: 33 indexFayette County33Gregg County: 33 indexGregg County33Hunt County: 33 indexHunt County33Smith County: 33 indexSmith County33Victoria County: 32 indexVictoria County32Polk County: 31 indexPolk County31Potter County: 29 indexPotter County29Culberson County: 21 indexCulberson County21
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2015
index		Change on 2014
1Harris County580
2El Paso County54-1
3Bexar County53-1
4Dallas County52-2
5Bowie County51-1
6Tarrant County50-1
7Hidalgo County49+2
7Travis County49-2
7Webb County49-3
10Cameron County48-3
10Montgomery County48-1
10Nueces County480
13Jefferson County47-4
14Denton County46-2
14Ellis County46-2
16Galveston County44+1
16Kleberg County44+1
16Maverick County44-4
19Navarro County43-4
20Brewster County420
20Harrison County42-3
20Kaufman County42-2
20McLennan County42-2
20Orange County42-1
20Randall County42+1
26Ector County39-4
27Parker County370
28Bell County36-3
28Collin County36-1
28Rockwall County360
31Johnson County35-1
32Hood County34-2
33Brazoria County33+1
33Fayette County33-6
33Gregg County330
33Hunt County33-2
33Smith County33-1
38Victoria County32+2
39Polk County31-1
40Potter County29-2
41Culberson County21-5

Other periods

About this ranking

Median of the daily Air Quality Index (AQI) values of a US county over the days of the year with an AQI, from the EPA AirData annual summaries.

More on how it is measured
  • The daily county AQI is the highest AQI among the monitors and pollutants reported that day (ozone, PM2.5, PM10, carbon monoxide and nitrogen dioxide).
  • Lower is cleaner: 0 to 50 is good, 51 to 100 moderate and above 100 unhealthy for sensitive groups.

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. 22 counties with data in other periods have no value for 2015 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: median daily AQI. 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: median daily AQI (Counties in Texas by median Air Quality Index (US EPA), 2015) [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: median daily AQI, Counties in Texas by median Air Quality Index (US EPA), 2015. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/median-air-quality-index/texas-counties?period=2015. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Counties in Texas by median Air Quality Index (US EPA), 2015. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/median-air-quality-index/texas-counties?period=2015.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Texas by median Air Quality Index (US EPA), 2015 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/texas-counties?period=2015 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_texas_by_2015,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Texas by median Air Quality Index (US EPA), 2015}},
  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/median-air-quality-index/texas-counties?period=2015. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. 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: median daily AQI: Counties in Texas by median Air Quality Index (US EPA), 2015
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/median-air-quality-index/texas-counties?period=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/texas-counties?period=2015.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Rank Counties in Texas by median Air Quality Index (US EPA) using official data, and cite the source.
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Questions

Which county has the highest median Air Quality Index (US EPA)?

Harris County, with 58 in 2015, according to the U.S. Environmental Protection Agency.

Which county has the lowest median Air Quality Index (US EPA)?

Culberson County, with 21 in 2015.

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: median daily AQI. Retrieved 2026-10-12. 22 counties have no value for 2015 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Texas: more rankings