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

Adams County had the highest share of days with good air quality (US EPA AQI) of 47 counties in 1992, at 100%. Cuyahoga County had the lowest, at 56%. The median was 82.3%. Source: EPA.

Highest100Adams County

Lowest56Cuyahoga County

Median82.347 counties

Map of counties, 1992

Under 68
68 to 76
76 to 82
82 to 89
89 to 97
97 and over
No data

%, 1992. 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, 1992

%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

Rank	Counties	1992 (%)	Change on 1991
1	Adams County	100	0 pts
1	Hancock County	100	0 pts
1	Ottawa County	100	0 pts
1	Tuscarawas County	100	n/a
5	Pickaway County	99.7	+0.3 pts
6	Greene County	98.3	+1.6 pts
7	Athens County	98.2	-1.8 pts
8	Richland County	97.6	-0.3 pts
9	Jackson County	96.6	-0.8 pts
10	Montgomery County	94	+11 pts
11	Belmont County	93.9	-1 pts
12	Seneca County	93.5	-2.3 pts
13	Scioto County	93.4	+1.5 pts
14	Wyandot County	93.2	-4.6 pts
15	Sandusky County	90.7	+0.5 pts
16	Preble County	90	+45.6 pts
17	Summit County	87.2	+18.4 pts
18	Lucas County	87.1	+7.4 pts
19	Mahoning County	86.8	+12.6 pts
20	Noble County	86.7	-1.6 pts
21	Columbiana County	85.5	0 pts
22	Lorain County	83.9	+11.7 pts
23	Franklin County	82.8	+12.4 pts
24	Clermont County	82.3	+15.5 pts
25	Fayette County	80.1	+12.2 pts
26	Medina County	79.7	+24.3 pts
26	Stark County	79.7	+12.3 pts
28	Crawford County	78.4	+10.3 pts
29	Butler County	77	+9.1 pts
30	Lake County	76.7	0 pts
31	Lawrence County	76.4	+21.1 pts
32	Portage County	75.2	+26.2 pts
33	Trumbull County	74.5	-18.1 pts
34	Allen County	73.7	+19.2 pts
35	Clark County	73.4	+22.5 pts
36	Ashtabula County	68.8	+15.2 pts
37	Hamilton County	68.6	+11.1 pts
37	Madison County	68.6	+17.4 pts
39	Washington County	68.1	+14.8 pts
40	Knox County	67.8	-3.6 pts
41	Warren County	67.3	+20.4 pts
42	Logan County	66.7	+20.3 pts
43	Union County	66.4	+20.6 pts
44	Jefferson County	60.9	+15.4 pts
45	Licking County	60.2	+11.6 pts
46	Clinton County	59.8	+14.8 pts
47	Cuyahoga County	56	+7.2 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. 11 counties with data in other periods have no value for 1992 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), 1992) [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), 1992. 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=1992. 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), 1992. 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=1992.

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), 1992 [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=1992 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_ohio_by_1992,
  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), 1992}},
  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=1992. 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), 1992
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=1992
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/ohio-counties?period=1992.
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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Questions

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

Adams County, with 100% in 1992, according to EPA.

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

Cuyahoga County, with 56% in 1992.

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. 11 counties have no value for 1992 and are not ranked.