Data / Highest daily Air Quality Index (US EPA) / Richland County

Highest daily Air Quality Index (US EPA) in Richland County

Highest daily Air Quality Index (US EPA) in Richland County was 50 in 2000, according to the U.S. Environmental Protection Agency. That is down 5 from 1999.

2000, index50
Change on 1999-5
Series high591991
Series low502000

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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Highest daily Air Quality Index (US EPA) in Richland County, 1990 to 2000

5052545658601990199219941996199820001990: 57 index1991: 59 index1992: 59 index1993: 57 index1994: 58 index1995: 56 index1996: 59 index1997: 55 index1998: 56 index1999: 55 index2000: 50 index5052.55557.5601990199420001990: 57 index1991: 59 index1992: 59 index1993: 57 index1994: 58 index1995: 56 index1996: 59 index1997: 55 index1998: 56 index1999: 55 index2000: 50 index
index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 11 values
Periodindex
200050
199955
199856
199755
199659
199556
199458
199357
199259
199159
199057

Richland County compared with nearby places

Allen County: 177 indexAshtabula County: 201 indexAthens County: 94 indexBelmont County: 59 indexButler County: 195 indexClark County: 209 indexClermont County: 187 indexClinton County: 205 indexColumbiana County: 88 indexCrawford County: 195 indexCuyahoga County: 174 indexDelaware County: 177 indexFayette County: 201 indexFranklin County: 179 indexGeauga County: 190 indexGreene County: 201 indexHamilton County: 187 indexHancock County: 44 indexJefferson County: 177 indexKnox County: 207 indexLake County: 187 indexLawrence County: 164 indexLicking County: 201 indexLorain County: 182 indexLucas County: 156 indexMadison County: 203 indexMahoning County: 185 indexMedina County: 182 indexMiami County: 192 indexMonroe County: 50 indexMontgomery County: 192 indexNoble County: 172 indexOttawa County: 44 indexPortage County: 182 indexPreble County: 164 indexRichland County: 50 indexSandusky County: 51 indexScioto County: 151 indexSeneca County: 77 indexStark County: 190 indexSummit County: 185 indexTrumbull County: 190 indexWarren County: 200 indexWashington County: 179 indexWood County: 151 indexWyandot County: 64 index
  • Under 83
  • 83 to 170
  • 170 to 180
  • 180 to 190
  • 190 to 200
  • 200 and over
  • No data
Highest daily Air Quality Index (US EPA), 2000, index. Richland 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

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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: highest 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: highest daily AQI (Highest daily Air Quality Index (US EPA), Richland County, 1990 to 2000) [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: highest daily AQI, Highest daily Air Quality Index (US EPA), Richland County, 1990 to 2000. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/en/highest-daily-air-quality-index/richland-county-ohio. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Highest daily Air Quality Index (US EPA), Richland County, 1990 to 2000. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/en/highest-daily-air-quality-index/richland-county-ohio.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Highest daily Air Quality Index (US EPA), Richland County, 1990 to 2000 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/highest-daily-air-quality-index/richland-county-ohio (Accessed: 12 October 2026).

BibTeX
@misc{environmental_highest_daily_air_quality_2000,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Highest daily Air Quality Index (US EPA), Richland County, 1990 to 2000}},
  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/highest-daily-air-quality-index/richland-county-ohio. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest 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: highest daily AQI: Highest daily Air Quality Index (US EPA), Richland County, 1990 to 2000
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/highest-daily-air-quality-index/richland-county-ohio
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/highest-daily-air-quality-index/richland-county-ohio.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest 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 highest daily Air Quality Index (US EPA) in Richland County?

Highest daily Air Quality Index (US EPA) in Richland County was 50 in 2000, according to the U.S. Environmental Protection Agency. That is down 5 from 1999.

Where does this figure come from?

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

What was the highest highest daily Air Quality Index (US EPA) in Richland County?

59 in 1991, the highest value since 1990 in this series.

Related statistics for Richland County

All statistics for Richland County | Richland County in figures