Data / Rankings / Median Air Quality Index (US EPA) / Counties in Ohio

Counties in Ohio by median Air Quality Index (US EPA)

Cuyahoga County had the highest median Air Quality Index (US EPA) of 46 counties in 2000, at 71. Seneca County had the lowest, at 18. The median was 45. Source: the U.S. Environmental Protection Agency.

Keep it in a collection in your library.
Highest71Cuyahoga County
Lowest18Seneca County
Median4546 counties

Map of counties, 2000

Allen County: 42 indexAshtabula County: 44 indexAthens County: 54 indexBelmont County: 24 indexButler County: 64 indexClark County: 51 indexClermont County: 48 indexClinton County: 50 indexColumbiana County: 31 indexCrawford County: 36 indexCuyahoga County: 71 indexDelaware County: 45 indexFayette County: 39 indexFranklin County: 66 indexGeauga County: 45 indexGreene County: 43 indexHamilton County: 68 indexHancock County: 25 indexJefferson County: 63 indexKnox County: 45 indexLake County: 40 indexLawrence County: 58 indexLicking County: 45 indexLorain County: 39 indexLucas County: 57 indexMadison County: 48 indexMahoning County: 61 indexMedina County: 43 indexMiami County: 46 indexMonroe County: 21 indexMontgomery County: 66 indexNoble County: 40 indexOttawa County: 22 indexPortage County: 53 indexPreble County: 49 indexRichland County: 19 indexSandusky County: 22 indexScioto County: 21 indexSeneca County: 18 indexStark County: 45 indexSummit County: 64 indexTrumbull County: 60 indexWarren County: 45 indexWashington County: 42 indexWood County: 41 indexWyandot County: 19 index
  • Under 25
  • 25 to 41
  • 41 to 45
  • 45 to 49
  • 49 to 61
  • 61 and over
  • No data
index, 2000. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2000

Cuyahoga County: 71 indexCuyahoga County71Hamilton County: 68 indexHamilton County68Franklin County: 66 indexFranklin County66Montgomery County: 66 indexMontgomery County66Butler County: 64 indexButler County64Summit County: 64 indexSummit County64Jefferson County: 63 indexJefferson County63Mahoning County: 61 indexMahoning County61Trumbull County: 60 indexTrumbull County60Lawrence County: 58 indexLawrence County58Lucas County: 57 indexLucas County57Athens County: 54 indexAthens County54Portage County: 53 indexPortage County53Clark County: 51 indexClark County51Clinton County: 50 indexClinton County50Preble County: 49 indexPreble County49Clermont County: 48 indexClermont County48Madison County: 48 indexMadison County48Miami County: 46 indexMiami County46Delaware County: 45 indexDelaware County45Geauga County: 45 indexGeauga County45Knox County: 45 indexKnox County45Licking County: 45 indexLicking County45Stark County: 45 indexStark County45Warren County: 45 indexWarren County45Ashtabula County: 44 indexAshtabula County44Greene County: 43 indexGreene County43Medina County: 43 indexMedina County43Allen County: 42 indexAllen County42Washington County: 42 indexWashington County42Wood County: 41 indexWood County41Lake County: 40 indexLake County40Noble County: 40 indexNoble County40Fayette County: 39 indexFayette County39Lorain County: 39 indexLorain County39Crawford County: 36 indexCrawford County36Columbiana County: 31 indexColumbiana County31Hancock County: 25 indexHancock County25Belmont County: 24 indexBelmont County24Ottawa County: 22 indexOttawa County22Sandusky County: 22 indexSandusky County22Monroe County: 21 indexMonroe County21Scioto County: 21 indexScioto County21Richland County: 19 indexRichland County19Wyandot County: 19 indexWyandot County19Seneca County: 18 indexSeneca County18Cuyahoga County: 71 indexCuyahoga County71Hamilton County: 68 indexHamilton County68Franklin County: 66 indexFranklin County66Montgomery County: 66 indexMontgomery County66Butler County: 64 indexButler County64Summit County: 64 indexSummit County64Jefferson County: 63 indexJefferson County63Mahoning County: 61 indexMahoning County61Trumbull County: 60 indexTrumbull County60Lawrence County: 58 indexLawrence County58Lucas County: 57 indexLucas County57Athens County: 54 indexAthens County54Portage County: 53 indexPortage County53Clark County: 51 indexClark County51Clinton County: 50 indexClinton County50Preble County: 49 indexPreble County49Clermont County: 48 indexClermont County48Madison County: 48 indexMadison County48Miami County: 46 indexMiami County46Delaware County: 45 indexDelaware County45Geauga County: 45 indexGeauga County45Knox County: 45 indexKnox County45Licking County: 45 indexLicking County45Stark County: 45 indexStark County45Warren County: 45 indexWarren County45Ashtabula County: 44 indexAshtabula County44Greene County: 43 indexGreene County43Medina County: 43 indexMedina County43Allen County: 42 indexAllen County42Washington County: 42 indexWashington County42Wood County: 41 indexWood County41Lake County: 40 indexLake County40Noble County: 40 indexNoble County40Fayette County: 39 indexFayette County39Lorain County: 39 indexLorain County39Crawford County: 36 indexCrawford County36Columbiana County: 31 indexColumbiana County31Hancock County: 25 indexHancock County25Belmont County: 24 indexBelmont County24Ottawa County: 22 indexOttawa County22Sandusky County: 22 indexSandusky County22Monroe County: 21 indexMonroe County21Scioto County: 21 indexScioto County21Richland County: 19 indexRichland County19Wyandot County: 19 indexWyandot County19Seneca County: 18 indexSeneca County18
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2000
index		Change on 1999
1Cuyahoga County71+1
2Hamilton County68-3
3Franklin County66-3
3Montgomery County66+1
5Butler County64-3
5Summit County64-2
7Jefferson County63+1
8Mahoning County61-3
9Trumbull County60-3
10Lawrence County580
11Lucas County57+1
12Athens County54-2
13Portage County53-5
14Clark County51+1
15Clinton County50-14
16Preble County49-5
17Clermont County48-16
17Madison County48-3
19Miami County46-1
20Delaware County45-2
20Geauga County45+1
20Knox County45-2
20Licking County45-4
20Stark County45-4
20Warren County45-9
26Ashtabula County44-2
27Greene County43-4
27Medina County43-1
29Allen County42-3
29Washington County42-3
31Wood County41-3
32Lake County40-5
32Noble County400
34Fayette County39-6
34Lorain County39-5
36Crawford County36-3
37Columbiana County31-3
38Hancock County25+6
39Belmont County24+2
40Ottawa County22+3
40Sandusky County22-5
42Monroe County21-1
42Scioto County21-8
44Richland County190
44Wyandot County190
46Seneca County18-4

Other periods

About this ranking

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.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 12 counties with data in other periods have no value for 2000 and are left out rather than filled from another source. Equal values share a rank.

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 (Counties in Ohio by median Air Quality Index (US EPA), 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: median daily AQI, Counties in Ohio by median Air Quality Index (US EPA), 2000. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/median-air-quality-index/ohio-counties?period=2000. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Counties in Ohio by median Air Quality Index (US EPA), 2000. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/median-air-quality-index/ohio-counties?period=2000.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Ohio by median Air Quality Index (US EPA), 2000 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/ohio-counties?period=2000 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_ohio_by_2000,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Ohio by median Air Quality Index (US EPA), 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/rankings/median-air-quality-index/ohio-counties?period=2000. 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: Counties in Ohio by median Air Quality Index (US EPA), 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/rankings/median-air-quality-index/ohio-counties?period=2000
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/ohio-counties?period=2000.
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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Rank Counties in Ohio by median Air Quality Index (US EPA) using official data, and cite the source.
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Questions

Which county has the highest median Air Quality Index (US EPA)?

Cuyahoga County, with 71 in 2000, according to the U.S. Environmental Protection Agency.

Which county has the lowest median Air Quality Index (US EPA)?

Seneca County, with 18 in 2000.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12. 12 counties have no value for 2000 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Ohio: more rankings