Median Air Quality Index (US EPA) in Marion County
Median Air Quality Index (US EPA) in Marion County was 54 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged from 2024.
Median Air Quality Index (US EPA) in Marion County, 1980 to 2025
All 46 values
| Period | index |
|---|---|
| 2025 | 54 |
| 2024 | 54 |
| 2023 | 60 |
| 2022 | 56 |
| 2021 | 58 |
| 2020 | 55 |
| 2019 | 58 |
| 2018 | 55 |
| 2017 | 54 |
| 2016 | 55 |
| 2015 | 56 |
| 2014 | 58 |
| 2013 | 61 |
| 2012 | 64 |
| 2011 | 64 |
| 2010 | 64 |
| 2009 | 61 |
| 2008 | 61 |
| 2007 | 66 |
| 2006 | 63 |
| 2005 | 67 |
| 2004 | 63 |
| 2003 | 63 |
| 2002 | 68 |
| 2001 | 69 |
| 2000 | 67 |
| 1999 | 65 |
| 1998 | 42 |
| 1997 | 37 |
| 1996 | 41 |
| 1995 | 44 |
| 1994 | 42 |
| 1993 | 41 |
| 1992 | 40 |
| 1991 | 42 |
| 1990 | 42 |
| 1989 | 46 |
| 1988 | 50 |
| 1987 | 54 |
| 1986 | 55 |
| 1985 | 58 |
| 1984 | 58 |
| 1983 | 61 |
| 1982 | 63 |
| 1981 | 63 |
| 1980 | 73 |
Marion County compared with nearby places
- Under 35
- 35 to 37
- 37 to 41
- 41 to 43
- 43 to 44
- 44 and over
- No data
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.
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
APA 7
U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: median daily AQI (Median Air Quality Index (US EPA), Marion 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), Marion 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/marion-county-indiana. 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), Marion 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/marion-county-indiana.
Harvard
U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Marion 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/marion-county-indiana (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), Marion 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/marion-county-indiana. 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), Marion 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/marion-county-indiana
Y2 - 2026/10/12
N1 - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/marion-county-indiana.
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 -
Use this data in your AI agent
Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:
What is the latest median Air Quality Index (US EPA) in Marion County? Cite the source.
get_value {"indicator":"aqi_median","place":"us-county-18097"}
GET https://invokely.ai/api/v1/value?indicator=aqi_median&place=us-county-18097Questions
What is the median Air Quality Index (US EPA) in Marion County?
Median Air Quality Index (US EPA) in Marion County was 54 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged from 2024.
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 Marion County?
73 in 1980, the highest value since 1980 in this series.