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

Median Air Quality Index (US EPA) in Sangamon County

Median Air Quality Index (US EPA) in Sangamon County was 41 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged from 2024. That is the 15th highest of 23 counties in 2025.

2025, index41
Change on 20240
Rank15th of 23Counties in Illinois ranked
Series high512023
Series low311997

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 Sangamon County, 1980 to 2025

30354045505519801987199420012008201520251980: 44 index1981: 39 index1982: 42 index1983: 43 index1984: 41 index1985: 40 index1986: 37 index1987: 35 index1988: 35 index1989: 38 index1990: 32 index1991: 36 index1992: 32 index1993: 34 index1994: 34 index1995: 33 index1996: 33 index1997: 31 index1998: 32 index1999: 37 index2000: 39 index2001: 39 index2002: 40 index2003: 39 index2004: 38 index2005: 39 index2006: 34 index2007: 36 index2008: 36 index2009: 33 index2010: 40 index2011: 32 index2012: 37 index2013: 35 index2014: 33 index2015: 35 index2016: 36 index2017: 43 index2018: 49 index2019: 45 index2020: 44 index2021: 43 index2022: 45 index2023: 51 index2024: 41 index2025: 41 index30354045505519801996201220251980: 44 index1981: 39 index1982: 42 index1983: 43 index1984: 41 index1985: 40 index1986: 37 index1987: 35 index1988: 35 index1989: 38 index1990: 32 index1991: 36 index1992: 32 index1993: 34 index1994: 34 index1995: 33 index1996: 33 index1997: 31 index1998: 32 index1999: 37 index2000: 39 index2001: 39 index2002: 40 index2003: 39 index2004: 38 index2005: 39 index2006: 34 index2007: 36 index2008: 36 index2009: 33 index2010: 40 index2011: 32 index2012: 37 index2013: 35 index2014: 33 index2015: 35 index2016: 36 index2017: 43 index2018: 49 index2019: 45 index2020: 44 index2021: 43 index2022: 45 index2023: 51 index2024: 41 index2025: 41 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
202541
202441
202351
202245
202143
202044
201945
201849
201743
201636
201535
201433
201335
201237
201132
201040
200933
200836
200736
200634
200539
200438
200339
200240
200139
200039
199937
199832
199731
199633
199533
199434
199334
199232
199136
199032
198938
198835
198735
198637
198540
198441
198343
198242
198139
198044

Sangamon County compared with nearby places

Adams County: 38 indexChampaign County: 43 indexClark County: 33 indexCook County: 53 indexDuPage County: 42 indexEffingham County: 35 indexHamilton County: 42 indexJersey County: 42 indexJo Daviess County: 33 indexKane County: 45 indexLake County: 39 indexMcHenry County: 42 indexMcLean County: 44 indexMacon County: 44 indexMacoupin County: 34 indexMadison County: 49 indexPeoria County: 45 indexRandolph County: 43 indexRock Island County: 41 indexSt. Clair County: 47 indexSangamon County: 41 indexWill County: 44 indexWinnebago County: 40 index
  • Under 38
  • 38 to 42
  • 42 to 43
  • 43 to 45
  • 45 and over
  • No data
Median Air Quality Index (US EPA), 2025, index. Sangamon 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), Sangamon 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), Sangamon 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/sangamon-county-illinois. 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), Sangamon 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/sangamon-county-illinois.

Harvard

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

Median Air Quality Index (US EPA) in Sangamon County was 41 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged from 2024. That is the 15th highest of 23 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 Sangamon County?

51 in 2023, the highest value since 1980 in this series.

Related statistics for Sangamon County

All statistics for Sangamon County | Sangamon County in figures