Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Ohio

Counties in Ohio by share of days with good air quality (US EPA AQI)

Athens County had the highest share of days with good air quality (US EPA AQI) of 49 counties in 1998, at 100%. Clark County had the lowest, at 40.7%. The median was 63%. Source: EPA.

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Highest100Athens County
Lowest40.7Clark County
Median6349 counties

Map of counties, 1998

Allen County: 54.4 %Ashtabula County: 61.8 %Athens County: 100 %Belmont County: 100 %Butler County: 63.8 %Clark County: 40.7 %Clermont County: 47.4 %Clinton County: 43.5 %Columbiana County: 91.9 %Crawford County: 67.9 %Cuyahoga County: 55.1 %Delaware County: 43.1 %Erie County: 85.7 %Fayette County: 63.2 %Franklin County: 69.3 %Geauga County: 60.3 %Greene County: 52.9 %Hamilton County: 51 %Hancock County: 100 %Jefferson County: 87.7 %Knox County: 61 %Lake County: 73.8 %Lawrence County: 56.7 %Licking County: 43.9 %Logan County: 63 %Lorain County: 77.3 %Lucas County: 76.7 %Madison County: 43.5 %Mahoning County: 65.8 %Medina County: 55.4 %Miami County: 53.8 %Monroe County: 98.3 %Montgomery County: 72.1 %Noble County: 61.4 %Ottawa County: 98.1 %Portage County: 57.1 %Preble County: 57.3 %Richland County: 98.3 %Sandusky County: 74.6 %Scioto County: 99.6 %Seneca County: 97.9 %Stark County: 68.5 %Summit County: 71.5 %Trumbull County: 55.8 %Union County: 59.3 %Warren County: 46.9 %Washington County: 62.3 %Wood County: 56.3 %Wyandot County: 94 %
  • Under 53
  • 53 to 57
  • 57 to 63
  • 63 to 72
  • 72 to 94
  • 94 and over
  • No data
%, 1998. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 1998

Athens County: 100 %Athens County100Belmont County: 100 %Belmont County100Hancock County: 100 %Hancock County100Scioto County: 99.6 %Scioto County99.6Monroe County: 98.3 %Monroe County98.3Richland County: 98.3 %Richland County98.3Ottawa County: 98.1 %Ottawa County98.1Seneca County: 97.9 %Seneca County97.9Wyandot County: 94 %Wyandot County94Columbiana County: 91.9 %Columbiana County91.9Jefferson County: 87.7 %Jefferson County87.7Erie County: 85.7 %Erie County85.7Lorain County: 77.3 %Lorain County77.3Lucas County: 76.7 %Lucas County76.7Sandusky County: 74.6 %Sandusky County74.6Lake County: 73.8 %Lake County73.8Montgomery County: 72.1 %Montgomery County72.1Summit County: 71.5 %Summit County71.5Franklin County: 69.3 %Franklin County69.3Stark County: 68.5 %Stark County68.5Crawford County: 67.9 %Crawford County67.9Mahoning County: 65.8 %Mahoning County65.8Butler County: 63.8 %Butler County63.8Fayette County: 63.2 %Fayette County63.2Logan County: 63 %Logan County63Washington County: 62.3 %Washington County62.3Ashtabula County: 61.8 %Ashtabula County61.8Noble County: 61.4 %Noble County61.4Knox County: 61 %Knox County61Geauga County: 60.3 %Geauga County60.3Union County: 59.3 %Union County59.3Preble County: 57.3 %Preble County57.3Portage County: 57.1 %Portage County57.1Lawrence County: 56.7 %Lawrence County56.7Wood County: 56.3 %Wood County56.3Trumbull County: 55.8 %Trumbull County55.8Medina County: 55.4 %Medina County55.4Cuyahoga County: 55.1 %Cuyahoga County55.1Allen County: 54.4 %Allen County54.4Miami County: 53.8 %Miami County53.8Greene County: 52.9 %Greene County52.9Hamilton County: 51 %Hamilton County51Clermont County: 47.4 %Clermont County47.4Warren County: 46.9 %Warren County46.9Licking County: 43.9 %Licking County43.9Clinton County: 43.5 %Clinton County43.5Madison County: 43.5 %Madison County43.5Delaware County: 43.1 %Delaware County43.1Clark County: 40.7 %Clark County40.7Athens County: 100 %Athens County100Belmont County: 100 %Belmont County100Hancock County: 100 %Hancock County100Scioto County: 99.6 %Scioto County99.6Monroe County: 98.3 %Monroe County98.3Richland County: 98.3 %Richland County98.3Ottawa County: 98.1 %Ottawa County98.1Seneca County: 97.9 %Seneca County97.9Wyandot County: 94 %Wyandot County94Columbiana County: 91.9 %Columbiana County91.9Jefferson County: 87.7 %Jefferson County87.7Erie County: 85.7 %Erie County85.7Lorain County: 77.3 %Lorain County77.3Lucas County: 76.7 %Lucas County76.7Sandusky County: 74.6 %Sandusky County74.6Lake County: 73.8 %Lake County73.8Montgomery County: 72.1 %Montgomery County72.1Summit County: 71.5 %Summit County71.5Franklin County: 69.3 %Franklin County69.3Stark County: 68.5 %Stark County68.5Crawford County: 67.9 %Crawford County67.9Mahoning County: 65.8 %Mahoning County65.8Butler County: 63.8 %Butler County63.8Fayette County: 63.2 %Fayette County63.2Logan County: 63 %Logan County63Washington County: 62.3 %Washington County62.3Ashtabula County: 61.8 %Ashtabula County61.8Noble County: 61.4 %Noble County61.4Knox County: 61 %Knox County61Geauga County: 60.3 %Geauga County60.3Union County: 59.3 %Union County59.3Preble County: 57.3 %Preble County57.3Portage County: 57.1 %Portage County57.1Lawrence County: 56.7 %Lawrence County56.7Wood County: 56.3 %Wood County56.3Trumbull County: 55.8 %Trumbull County55.8Medina County: 55.4 %Medina County55.4Cuyahoga County: 55.1 %Cuyahoga County55.1Allen County: 54.4 %Allen County54.4Miami County: 53.8 %Miami County53.8Greene County: 52.9 %Greene County52.9Hamilton County: 51 %Hamilton County51Clermont County: 47.4 %Clermont County47.4Warren County: 46.9 %Warren County46.9Licking County: 43.9 %Licking County43.9Clinton County: 43.5 %Clinton County43.5Madison County: 43.5 %Madison County43.5Delaware County: 43.1 %Delaware County43.1Clark County: 40.7 %Clark County40.7
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties1998 (%)Change on 1997
1Athens County1000 pts
1Belmont County100+4.1 pts
1Hancock County1000 pts
4Scioto County99.6+1.6 pts
5Monroe County98.3+2.7 pts
5Richland County98.3+0.6 pts
7Ottawa County98.1-1.9 pts
8Seneca County97.9+0.9 pts
9Wyandot County94-0.9 pts
10Columbiana County91.9-2.9 pts
11Jefferson County87.7+8.6 pts
12Erie County85.7n/a
13Lorain County77.3-2.7 pts
14Lucas County76.7-4.1 pts
15Sandusky County74.6+0.4 pts
16Lake County73.8-7.6 pts
17Montgomery County72.1-7.6 pts
18Summit County71.5-10.1 pts
19Franklin County69.3-9.9 pts
20Stark County68.5-9 pts
21Crawford County67.9-10.1 pts
22Mahoning County65.8-12 pts
23Butler County63.8-7.4 pts
24Fayette County63.2-8.8 pts
25Logan County63-2.7 pts
26Washington County62.3-16.8 pts
27Ashtabula County61.8-9.1 pts
28Noble County61.4-10.5 pts
29Knox County61-9.4 pts
30Geauga County60.3-2.6 pts
31Union County59.3-32.1 pts
32Preble County57.3-6.5 pts
33Portage County57.1-7.1 pts
34Lawrence County56.7-11.9 pts
35Wood County56.3-13.8 pts
36Trumbull County55.8-12.4 pts
37Medina County55.4-9.7 pts
38Cuyahoga County55.1-1.1 pts
39Allen County54.4-16.2 pts
40Miami County53.8-11.4 pts
41Greene County52.9-6.5 pts
42Hamilton County51-6.5 pts
43Clermont County47.4-12.9 pts
44Warren County46.9-15.8 pts
45Licking County43.9-19.3 pts
46Clinton County43.5-13.4 pts
46Madison County43.5-12.6 pts
48Delaware County43.1-19 pts
49Clark County40.7-11.2 pts

Other periods

About this ranking

Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.

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. 9 counties with data in other periods have no value for 1998 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: good days as a share of days with an AQI, calculated with stored counts. 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: good days as a share of days with an AQI, calculated with stored counts (Counties in Ohio by share of days with good air quality (US EPA AQI), 1998) [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: good days as a share of days with an AQI, calculated with stored counts, Counties in Ohio by share of days with good air quality (US EPA AQI), 1998. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/good-air-quality-days-share/ohio-counties?period=1998. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Counties in Ohio by share of days with good air quality (US EPA AQI), 1998. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/good-air-quality-days-share/ohio-counties?period=1998.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Ohio by share of days with good air quality (US EPA AQI), 1998 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/ohio-counties?period=1998 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_ohio_by_1998,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Ohio by share of days with good air quality (US EPA AQI), 1998}},
  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/good-air-quality-days-share/ohio-counties?period=1998. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. 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: good days as a share of days with an AQI, calculated with stored counts: Counties in Ohio by share of days with good air quality (US EPA AQI), 1998
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/good-air-quality-days-share/ohio-counties?period=1998
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/ohio-counties?period=1998.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Rank Counties in Ohio by share of days with good air quality (US EPA AQI) using official data, and cite the source.
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Questions

Which county has the highest share of days with good air quality (US EPA AQI)?

Athens County, with 100% in 1998, according to EPA.

Which county has the lowest share of days with good air quality (US EPA AQI)?

Clark County, with 40.7% in 1998.

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: good days as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 9 counties have no value for 1998 and are not ranked.

Share of days with good air quality (US EPA AQI): other rankings

Counties in Ohio: more rankings