Air Quality in Ohio

Ohio has 40 counties with EPA air quality monitoring. Air quality is stable across the state, with an average of 210 "Good" days per county per year. The best air quality is in Columbiana (median AQI 12) and the most polluted is Cuyahoga (median AQI 54).

County	Median AQI	Max AQI	Good Days	Unhealthy Days	Trend	Top Pollutant
Adams	39	83	215	0	↑ worsening	PM2.5
Allen	42	97	275	0	→ stable	Ozone
Ashtabula	41	108	205	2	→ stable	Ozone
Athens	28	64	330	0	↓ improving	PM2.5
Belmont	32	77	289	0	↑ worsening	PM2.5
Butler	53	122	154	3	↑ worsening	PM2.5
Clark	45	133	239	3	→ stable	PM2.5
Clermont	39	119	305	3	↓ improving	Ozone
Clinton	44	112	176	4	→ stable	Ozone
Columbiana	12	34	63	0	↓ improving	PM10
Cuyahoga	54	122	136	6	→ stable	PM2.5
Delaware	42	105	200	1	→ stable	Ozone
Fayette	35	64	126	0	→ stable	Ozone
Franklin	53	118	151	4	→ stable	PM2.5
Geauga	41	101	196	1	→ stable	Ozone
Greene	43	119	198	1	→ stable	Ozone
Hamilton	52	140	164	11	→ stable	PM2.5
Harrison	33	71	34	0	↑ worsening	PM2.5
Jefferson	45	93	227	0	↓ improving	PM2.5
Knox	41	101	208	1	→ stable	Ozone
Lake	41	136	272	4	→ stable	Ozone
Lawrence	43	99	264	0	→ stable	PM2.5
Licking	42	100	205	0	→ stable	Ozone
Lorain	39	74	216	0	→ stable	Ozone
Lucas	52	119	155	4	→ stable	PM2.5
Madison	44	100	203	0	→ stable	Ozone
Mahoning	44	93	239	0	→ stable	PM2.5
Medina	44	100	236	0	→ stable	PM2.5
Miami	43	101	198	1	→ stable	Ozone
Montgomery	47	147	225	4	→ stable	PM2.5
Noble	40	90	290	0	→ stable	Ozone
Portage	43	108	187	2	→ stable	Ozone
Preble	44	100	252	0	→ stable	PM2.5
Scioto	40	80	248	0	↑ worsening	PM2.5
Stark	48	93	192	0	→ stable	PM2.5
Summit	44	105	224	1	→ stable	PM2.5
Trumbull	45	97	226	0	→ stable	PM2.5
Warren	43	147	267	6	→ stable	Ozone
Washington	41	90	212	0	→ stable	Ozone
Wood	41	101	203	1	→ stable	Ozone