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

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

Clinton County had the highest median Air Quality Index (US EPA) of 48 counties in 1993, at 51. Athens County had the lowest, at 16. The median was 37. Source: the U.S. Environmental Protection Agency.

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Highest51Clinton County
Lowest16Athens County
Median3748 counties

Map of counties, 1993

Adams County: 16 indexAllen County: 44 indexAshtabula County: 39 indexAthens County: 16 indexBelmont County: 26 indexButler County: 38 indexClark County: 45 indexClermont County: 48 indexClinton County: 51 indexColumbiana County: 40 indexCrawford County: 38 indexCuyahoga County: 50 indexFayette County: 37 indexFranklin County: 33 indexGreene County: 17 indexHamilton County: 43 indexHancock County: 30 indexJackson County: 21 indexJefferson County: 40 indexKnox County: 46 indexLake County: 31 indexLawrence County: 39 indexLicking County: 44 indexLogan County: 44 indexLorain County: 34 indexLucas County: 31 indexMadison County: 50 indexMahoning County: 29 indexMedina County: 47 indexMiami County: 44 indexMonroe County: 27 indexMontgomery County: 30 indexNoble County: 25 indexOttawa County: 19 indexPickaway County: 21 indexPortage County: 44 indexPreble County: 43 indexRichland County: 24 indexSandusky County: 31 indexScioto County: 29 indexSeneca County: 20 indexStark County: 35 indexSummit County: 32 indexTrumbull County: 41 indexTuscarawas County: 37 indexWarren County: 49 indexWashington County: 47 indexWyandot County: 22 index
  • Under 24
  • 24 to 31
  • 31 to 37
  • 37 to 42
  • 42 to 45
  • 45 and over
  • No data
index, 1993. 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, 1993

Clinton County: 51 indexClinton County51Cuyahoga County: 50 indexCuyahoga County50Madison County: 50 indexMadison County50Warren County: 49 indexWarren County49Clermont County: 48 indexClermont County48Medina County: 47 indexMedina County47Washington County: 47 indexWashington County47Knox County: 46 indexKnox County46Clark County: 45 indexClark County45Allen County: 44 indexAllen County44Licking County: 44 indexLicking County44Logan County: 44 indexLogan County44Miami County: 44 indexMiami County44Portage County: 44 indexPortage County44Hamilton County: 43 indexHamilton County43Preble County: 43 indexPreble County43Trumbull County: 41 indexTrumbull County41Columbiana County: 40 indexColumbiana County40Jefferson County: 40 indexJefferson County40Ashtabula County: 39 indexAshtabula County39Lawrence County: 39 indexLawrence County39Butler County: 38 indexButler County38Crawford County: 38 indexCrawford County38Fayette County: 37 indexFayette County37Tuscarawas County: 37 indexTuscarawas County37Stark County: 35 indexStark County35Lorain County: 34 indexLorain County34Franklin County: 33 indexFranklin County33Summit County: 32 indexSummit County32Lake County: 31 indexLake County31Lucas County: 31 indexLucas County31Sandusky County: 31 indexSandusky County31Hancock County: 30 indexHancock County30Montgomery County: 30 indexMontgomery County30Mahoning County: 29 indexMahoning County29Scioto County: 29 indexScioto County29Monroe County: 27 indexMonroe County27Belmont County: 26 indexBelmont County26Noble County: 25 indexNoble County25Richland County: 24 indexRichland County24Wyandot County: 22 indexWyandot County22Jackson County: 21 indexJackson County21Pickaway County: 21 indexPickaway County21Seneca County: 20 indexSeneca County20Ottawa County: 19 indexOttawa County19Greene County: 17 indexGreene County17Adams County: 16 indexAdams County16Athens County: 16 indexAthens County16Clinton County: 51 indexClinton County51Cuyahoga County: 50 indexCuyahoga County50Madison County: 50 indexMadison County50Warren County: 49 indexWarren County49Clermont County: 48 indexClermont County48Medina County: 47 indexMedina County47Washington County: 47 indexWashington County47Knox County: 46 indexKnox County46Clark County: 45 indexClark County45Allen County: 44 indexAllen County44Licking County: 44 indexLicking County44Logan County: 44 indexLogan County44Miami County: 44 indexMiami County44Portage County: 44 indexPortage County44Hamilton County: 43 indexHamilton County43Preble County: 43 indexPreble County43Trumbull County: 41 indexTrumbull County41Columbiana County: 40 indexColumbiana County40Jefferson County: 40 indexJefferson County40Ashtabula County: 39 indexAshtabula County39Lawrence County: 39 indexLawrence County39Butler County: 38 indexButler County38Crawford County: 38 indexCrawford County38Fayette County: 37 indexFayette County37Tuscarawas County: 37 indexTuscarawas County37Stark County: 35 indexStark County35Lorain County: 34 indexLorain County34Franklin County: 33 indexFranklin County33Summit County: 32 indexSummit County32Lake County: 31 indexLake County31Lucas County: 31 indexLucas County31Sandusky County: 31 indexSandusky County31Hancock County: 30 indexHancock County30Montgomery County: 30 indexMontgomery County30Mahoning County: 29 indexMahoning County29Scioto County: 29 indexScioto County29Monroe County: 27 indexMonroe County27Belmont County: 26 indexBelmont County26Noble County: 25 indexNoble County25Richland County: 24 indexRichland County24Wyandot County: 22 indexWyandot County22Jackson County: 21 indexJackson County21Pickaway County: 21 indexPickaway County21Seneca County: 20 indexSeneca County20Ottawa County: 19 indexOttawa County19Greene County: 17 indexGreene County17Adams County: 16 indexAdams County16Athens County: 16 indexAthens County16
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties1993
index		Change on 1992
1Clinton County51+7
2Cuyahoga County50+3
2Madison County50+6
4Warren County49+5
5Clermont County48+12
6Medina County47+8
6Washington County47+3
8Knox County46+5
9Clark County45+3
10Allen County44+3
10Licking County44-2
10Logan County44-1
10Miami County44n/a
10Portage County44+5
15Hamilton County43-1
15Preble County43+9
17Trumbull County41+1
18Columbiana County40+7
18Jefferson County40-4
20Ashtabula County39-3
20Lawrence County39+3
22Butler County380
22Crawford County38+1
24Fayette County370
24Tuscarawas County37+18
26Stark County35+2
27Lorain County34+2
28Franklin County33-1
29Summit County32+2
30Lake County31-4
30Lucas County310
30Sandusky County31+3
33Hancock County30+4
33Montgomery County30+3
35Mahoning County29-1
35Scioto County29+1
37Monroe County27n/a
38Belmont County26+4
39Noble County25-3
40Richland County24+1
41Wyandot County22+1
42Jackson County21-1
42Pickaway County21+1
44Seneca County20+2
45Ottawa County19-3
46Greene County17-4
47Adams County16-3
47Athens County16-3

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 1993 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), 1993) [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), 1993. 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=1993. 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), 1993. 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=1993.

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), 1993 [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=1993 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_ohio_by_1993,
  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), 1993}},
  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=1993. 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), 1993
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=1993
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/ohio-counties?period=1993.
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)?

Clinton County, with 51 in 1993, according to the U.S. Environmental Protection Agency.

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

Athens County, with 16 in 1993.

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 1993 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Ohio: more rankings