Data / Median Air Quality Index (US EPA) / Denver County

Median Air Quality Index (US EPA) in Denver County

Median Air Quality Index (US EPA) in Denver County was 50 in 2025, according to the U.S. Environmental Protection Agency. That is down 5 from 2024. That is the 2nd highest of 30 counties in 2025.

2025, index50
Change on 2024-5
Rank2nd of 30Counties in Colorado ranked
Series high871980
Series low441991

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 Denver County, 1980 to 2025

40506070809019801987199420012008201520251980: 87 index1981: 82 index1982: 77 index1983: 84 index1984: 77 index1985: 77 index1986: 77 index1987: 71 index1988: 64 index1989: 60 index1990: 45 index1991: 44 index1992: 60 index1993: 52 index1994: 56 index1995: 52 index1996: 55 index1997: 52 index1998: 56 index1999: 48 index2000: 53 index2001: 57 index2002: 55 index2003: 56 index2004: 50 index2005: 53 index2006: 54 index2007: 54 index2008: 51 index2009: 47 index2010: 51 index2011: 52 index2012: 54 index2013: 52 index2014: 53 index2015: 54 index2016: 54 index2017: 53 index2018: 54 index2019: 54 index2020: 53 index2021: 55 index2022: 52 index2023: 54 index2024: 55 index2025: 50 index40608010019801996201220251980: 87 index1981: 82 index1982: 77 index1983: 84 index1984: 77 index1985: 77 index1986: 77 index1987: 71 index1988: 64 index1989: 60 index1990: 45 index1991: 44 index1992: 60 index1993: 52 index1994: 56 index1995: 52 index1996: 55 index1997: 52 index1998: 56 index1999: 48 index2000: 53 index2001: 57 index2002: 55 index2003: 56 index2004: 50 index2005: 53 index2006: 54 index2007: 54 index2008: 51 index2009: 47 index2010: 51 index2011: 52 index2012: 54 index2013: 52 index2014: 53 index2015: 54 index2016: 54 index2017: 53 index2018: 54 index2019: 54 index2020: 53 index2021: 55 index2022: 52 index2023: 54 index2024: 55 index2025: 50 index
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 46 values
Periodindex
202550
202455
202354
202252
202155
202053
201954
201854
201753
201654
201554
201453
201352
201254
201152
201051
200947
200851
200754
200654
200553
200450
200356
200255
200157
200053
199948
199856
199752
199655
199552
199456
199352
199260
199144
199045
198960
198864
198771
198677
198577
198477
198384
198277
198182
198087

Denver 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. Denver 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), Denver County, 1980 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), Denver County, 1980 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/denver-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), Denver County, 1980 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/denver-county-colorado.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Denver County, 1980 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/denver-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), Denver County, 1980 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/denver-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), Denver County, 1980 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/denver-county-colorado
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/denver-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 Denver County?

Median Air Quality Index (US EPA) in Denver County was 50 in 2025, according to the U.S. Environmental Protection Agency. That is down 5 from 2024. That is the 2nd 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 Denver County?

87 in 1980, the highest value since 1980 in this series.

Related statistics for Denver County

All statistics for Denver County | Denver County in figures