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 48 counties in 1994, at 51. Adams County had the lowest, at 13. The median was 37. Source: the U.S. Environmental Protection Agency.

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Highest51Cuyahoga County
Lowest13Adams County
Median3748 counties

Map of counties, 1994

Adams County: 13 indexAllen County: 45 indexAshtabula County: 43 indexAthens County: 16 indexBelmont County: 28 indexButler County: 40 indexClark County: 50 indexClermont County: 46 indexClinton County: 49 indexColumbiana County: 35 indexCrawford County: 37 indexCuyahoga County: 51 indexFayette County: 38 indexFranklin County: 35 indexGreene County: 19 indexHamilton County: 43 indexHancock County: 32 indexJackson County: 19 indexJefferson County: 42 indexKnox County: 46 indexLake County: 33 indexLawrence County: 44 indexLicking County: 47 indexLogan County: 51 indexLorain County: 36 indexLucas County: 35 indexMadison County: 48 indexMahoning County: 28 indexMedina County: 46 indexMiami County: 35 indexMonroe County: 25 indexMontgomery County: 35 indexNoble County: 37 indexOttawa County: 23 indexPickaway County: 26 indexPortage County: 45 indexPreble County: 44 indexRichland County: 24 indexSandusky County: 31 indexScioto County: 27 indexSeneca County: 23 indexStark County: 34 indexSummit County: 34 indexTrumbull County: 42 indexTuscarawas County: 40 indexWarren County: 47 indexWashington County: 50 indexWyandot County: 23 index
  • Under 25
  • 25 to 34
  • 34 to 37
  • 37 to 43
  • 43 to 46
  • 46 and over
  • No data
index, 1994. 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, 1994

Cuyahoga County: 51 indexCuyahoga County51Logan County: 51 indexLogan County51Clark County: 50 indexClark County50Washington County: 50 indexWashington County50Clinton County: 49 indexClinton County49Madison County: 48 indexMadison County48Licking County: 47 indexLicking County47Warren County: 47 indexWarren County47Clermont County: 46 indexClermont County46Knox County: 46 indexKnox County46Medina County: 46 indexMedina County46Allen County: 45 indexAllen County45Portage County: 45 indexPortage County45Lawrence County: 44 indexLawrence County44Preble County: 44 indexPreble County44Ashtabula County: 43 indexAshtabula County43Hamilton County: 43 indexHamilton County43Jefferson County: 42 indexJefferson County42Trumbull County: 42 indexTrumbull County42Butler County: 40 indexButler County40Tuscarawas County: 40 indexTuscarawas County40Fayette County: 38 indexFayette County38Crawford County: 37 indexCrawford County37Noble County: 37 indexNoble County37Lorain County: 36 indexLorain County36Columbiana County: 35 indexColumbiana County35Franklin County: 35 indexFranklin County35Lucas County: 35 indexLucas County35Miami County: 35 indexMiami County35Montgomery County: 35 indexMontgomery County35Stark County: 34 indexStark County34Summit County: 34 indexSummit County34Lake County: 33 indexLake County33Hancock County: 32 indexHancock County32Sandusky County: 31 indexSandusky County31Belmont County: 28 indexBelmont County28Mahoning County: 28 indexMahoning County28Scioto County: 27 indexScioto County27Pickaway County: 26 indexPickaway County26Monroe County: 25 indexMonroe County25Richland County: 24 indexRichland County24Ottawa County: 23 indexOttawa County23Seneca County: 23 indexSeneca County23Wyandot County: 23 indexWyandot County23Greene County: 19 indexGreene County19Jackson County: 19 indexJackson County19Athens County: 16 indexAthens County16Adams County: 13 indexAdams County13Cuyahoga County: 51 indexCuyahoga County51Logan County: 51 indexLogan County51Clark County: 50 indexClark County50Washington County: 50 indexWashington County50Clinton County: 49 indexClinton County49Madison County: 48 indexMadison County48Licking County: 47 indexLicking County47Warren County: 47 indexWarren County47Clermont County: 46 indexClermont County46Knox County: 46 indexKnox County46Medina County: 46 indexMedina County46Allen County: 45 indexAllen County45Portage County: 45 indexPortage County45Lawrence County: 44 indexLawrence County44Preble County: 44 indexPreble County44Ashtabula County: 43 indexAshtabula County43Hamilton County: 43 indexHamilton County43Jefferson County: 42 indexJefferson County42Trumbull County: 42 indexTrumbull County42Butler County: 40 indexButler County40Tuscarawas County: 40 indexTuscarawas County40Fayette County: 38 indexFayette County38Crawford County: 37 indexCrawford County37Noble County: 37 indexNoble County37Lorain County: 36 indexLorain County36Columbiana County: 35 indexColumbiana County35Franklin County: 35 indexFranklin County35Lucas County: 35 indexLucas County35Miami County: 35 indexMiami County35Montgomery County: 35 indexMontgomery County35Stark County: 34 indexStark County34Summit County: 34 indexSummit County34Lake County: 33 indexLake County33Hancock County: 32 indexHancock County32Sandusky County: 31 indexSandusky County31Belmont County: 28 indexBelmont County28Mahoning County: 28 indexMahoning County28Scioto County: 27 indexScioto County27Pickaway County: 26 indexPickaway County26Monroe County: 25 indexMonroe County25Richland County: 24 indexRichland County24Ottawa County: 23 indexOttawa County23Seneca County: 23 indexSeneca County23Wyandot County: 23 indexWyandot County23Greene County: 19 indexGreene County19Jackson County: 19 indexJackson County19Athens County: 16 indexAthens County16Adams County: 13 indexAdams County13
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties1994
index		Change on 1993
1Cuyahoga County51+1
1Logan County51+7
3Clark County50+5
3Washington County50+3
5Clinton County49-2
6Madison County48-2
7Licking County47+3
7Warren County47-2
9Clermont County46-2
9Knox County460
9Medina County46-1
12Allen County45+1
12Portage County45+1
14Lawrence County44+5
14Preble County44+1
16Ashtabula County43+4
16Hamilton County430
18Jefferson County42+2
18Trumbull County42+1
20Butler County40+2
20Tuscarawas County40+3
22Fayette County38+1
23Crawford County37-1
23Noble County37+12
25Lorain County36+2
26Columbiana County35-5
26Franklin County35+2
26Lucas County35+4
26Miami County35-9
26Montgomery County35+5
31Stark County34-1
31Summit County34+2
33Lake County33+2
34Hancock County32+2
35Sandusky County310
36Belmont County28+2
36Mahoning County28-1
38Scioto County27-2
39Pickaway County26+5
40Monroe County25-2
41Richland County240
42Ottawa County23+4
42Seneca County23+3
42Wyandot County23+1
45Greene County19+2
45Jackson County19-2
47Athens County160
48Adams County13-3

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. 10 counties with data in other periods have no value for 1994 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), 1994) [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), 1994. 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=1994. 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), 1994. 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=1994.

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), 1994 [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=1994 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_ohio_by_1994,
  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), 1994}},
  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=1994. 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), 1994
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=1994
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/ohio-counties?period=1994.
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 51 in 1994, according to the U.S. Environmental Protection Agency.

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

Adams County, with 13 in 1994.

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. 10 counties have no value for 1994 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Ohio: more rankings