Median Air Quality Index (US EPA) in Douglas County

Median Air Quality Index (US EPA) in Douglas County was 46 in 2025, according to the U.S. Environmental Protection Agency. That is down 2 from 2024. That is the 13th highest of 30 counties in 2025.

2025, index46
Change on 2024-2
Series high512002
Series low141994

Next release: Tuesday, 13 July 2027, estimated by Invokely from past publication dates (low confidence), not announced by the publisher. Release calendar

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Median Air Quality Index (US EPA) in Douglas County, 1989 to 2025

10203040506019891995200120072013201920251989: 22 index1990: 16 index1991: 15 index1992: 17 index1993: 44 index1994: 14 index1995: 47 index1996: 49 index1997: 48 index1998: 48 index1999: 48 index2000: 49 index2001: 48 index2002: 51 index2003: 50 index2004: 44 index2005: 44 index2006: 45 index2007: 44 index2008: 46 index2009: 44 index2010: 46 index2011: 46 index2012: 48 index2013: 44 index2014: 44 index2015: 44 index2016: 44 index2017: 49 index2018: 49 index2019: 47 index2020: 47 index2021: 48 index2022: 46 index2023: 49 index2024: 48 index2025: 46 index10203040506019892002201520251989: 22 index1990: 16 index1991: 15 index1992: 17 index1993: 44 index1994: 14 index1995: 47 index1996: 49 index1997: 48 index1998: 48 index1999: 48 index2000: 49 index2001: 48 index2002: 51 index2003: 50 index2004: 44 index2005: 44 index2006: 45 index2007: 44 index2008: 46 index2009: 44 index2010: 46 index2011: 46 index2012: 48 index2013: 44 index2014: 44 index2015: 44 index2016: 44 index2017: 49 index2018: 49 index2019: 47 index2020: 47 index2021: 48 index2022: 46 index2023: 49 index2024: 48 index2025: 46 index
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 37 values
Periodindex
202546
202448
202349
202246
202148
202047
201947
201849
201749
201644
201544
201444
201344
201248
201146
201046
200944
200846
200744
200645
200544
200444
200350
200251
200148
200049
199948
199848
199748
199649
199547
199414
199344
199217
199115
199016
198922

Douglas County compared with nearby places

Adams County: 49 indexAlamosa County: 25 indexArapahoe County: 48 indexArchuleta County: 34 indexBoulder County: 48 indexChaffee County: 48 indexClear Creek County: 48 indexDelta County: 29 indexDenver County: 50 indexDouglas County: 46 indexEl Paso County: 46 indexFremont County: 23 indexGarfield County: 47 indexGilpin County: 46 indexGrand County: 44 indexGunnison County: 46 indexJackson County: 9 indexJefferson County: 48 indexLa Plata County: 48 indexLarimer County: 50 indexMesa County: 46 indexMontezuma County: 45 indexPark County: 48 indexPitkin County: 19 indexProwers County: 27 indexPueblo County: 45 indexRoutt County: 22 indexSan Juan County: 12 indexSan Miguel County: 36 indexWeld County: 52 index
  • Under 25
  • 25 to 41
  • 41 to 46
  • 46 to 48
  • 48 and over
  • No data
Median Air Quality Index (US EPA), 2025, index. Douglas County is outlined. Same source and period for every area shown. Source: U.S. Environmental Protection Agency. Boundaries: U.S. Census Bureau cartographic boundary files.

Rankings

Definition

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.

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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 (Median Air Quality Index (US EPA), Douglas County, 1989 to 2025) [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, Median Air Quality Index (US EPA), Douglas County, 1989 to 2025. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/en/median-air-quality-index/douglas-county-colorado. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Median Air Quality Index (US EPA), Douglas County, 1989 to 2025. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/en/median-air-quality-index/douglas-county-colorado.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Douglas County, 1989 to 2025 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/median-air-quality-index/douglas-county-colorado (Accessed: 12 October 2026).

BibTeX
@misc{environmental_median_air_quality_index_2025,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Median Air Quality Index (US EPA), Douglas County, 1989 to 2025}},
  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/en/median-air-quality-index/douglas-county-colorado. 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: Median Air Quality Index (US EPA), Douglas County, 1989 to 2025
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/en/median-air-quality-index/douglas-county-colorado
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/douglas-county-colorado.
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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Questions

What is the median Air Quality Index (US EPA) in Douglas County?

Median Air Quality Index (US EPA) in Douglas County was 46 in 2025, according to the U.S. Environmental Protection Agency. That is down 2 from 2024. That is the 13th highest of 30 counties in 2025.

Where does this figure come from?

U.S. Environmental Protection Agency. EPA AirData annual AQI by county: median daily AQI. Retrieved by Invokely on 2026-10-12.

What was the highest median Air Quality Index (US EPA) in Douglas County?

51 in 2002, the highest value since 1989 in this series.

Related statistics for Douglas County

All statistics for Douglas County | Douglas County in figures