Counties in Ohio by highest daily Air Quality Index (US EPA)

Noble County had the highest highest daily Air Quality Index (US EPA) of 45 counties in 1995, at 222. Ottawa County had the lowest, at 44. The median was 190. Source: the U.S. Environmental Protection Agency.

Highest222Noble County

Lowest44Ottawa County

Median19045 counties

Map of counties, 1995

Under 62
62 to 170
170 to 190
190 to 200
200 to 210
210 and over
No data

index, 1995. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 1995

index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

Rank	Counties	1995 index	Change on 1994
1	Noble County	222	+61
2	Butler County	217	+11
3	Hamilton County	216	+24
4	Ashtabula County	215	+61
4	Clermont County	215	+38
4	Warren County	215	+14
7	Licking County	210	+41
8	Clark County	208	+1
8	Mahoning County	208	+65
10	Lake County	206	+14
11	Clinton County	205	+5
11	Madison County	205	+10
13	Franklin County	203	+29
14	Portage County	202	+41
15	Stark County	200	+34
16	Knox County	197	+23
16	Logan County	197	0
16	Lucas County	197	-22
19	Montgomery County	195	-5
20	Allen County	192	+15
20	Trumbull County	192	+20
22	Crawford County	190	+16
22	Cuyahoga County	190	-5
22	Jefferson County	190	-43
25	Lorain County	187	+18
25	Miami County	187	+33
27	Medina County	185	-18
27	Summit County	185	+31
27	Washington County	185	-15
30	Preble County	174	0
31	Lawrence County	172	-32
32	Fayette County	169	-16
33	Adams County	103	+64
34	Columbiana County	88	-61
35	Seneca County	80	-2
36	Belmont County	69	+7
37	Sandusky County	67	-1
38	Scioto County	59	-14
38	Wyandot County	59	-10
40	Richland County	56	-2
41	Greene County	52	-2
41	Monroe County	52	-34
43	Athens County	46	-6
44	Hancock County	44	-1
44	Ottawa County	44	-4

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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. 13 counties with data in other periods have no value for 1995 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: highest 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: highest daily AQI (Counties in Ohio by highest daily Air Quality Index (US EPA), 1995) [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: highest daily AQI, Counties in Ohio by highest daily Air Quality Index (US EPA), 1995. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/ohio-counties?period=1995. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in Ohio by highest daily Air Quality Index (US EPA), 1995. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/ohio-counties?period=1995.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in Ohio by highest daily Air Quality Index (US EPA), 1995 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/ohio-counties?period=1995 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_ohio_by_1995,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Counties in Ohio by highest daily Air Quality Index (US EPA), 1995}},
  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/highest-daily-air-quality-index/ohio-counties?period=1995. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest 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: highest daily AQI: Counties in Ohio by highest daily Air Quality Index (US EPA), 1995
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/highest-daily-air-quality-index/ohio-counties?period=1995
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/ohio-counties?period=1995.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. 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 highest daily Air Quality Index (US EPA)?

Noble County, with 222 in 1995, according to the U.S. Environmental Protection Agency.

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

Ottawa County, with 44 in 1995.

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: highest daily AQI. Retrieved 2026-10-12. 13 counties have no value for 1995 and are not ranked.