Air Quality in Pennsylvania

Pennsylvania has 40 counties with EPA air quality monitoring. Air quality is generally improving across the state, with an average of 258 "Good" days per county per year. The best air quality is in Lawrence (median AQI 24) and the most polluted is Allegheny (median AQI 52).

County	Median AQI	Max AQI	Good Days	Unhealthy Days	Trend	Top Pollutant
Adams	44	131	231	3	→ stable	Ozone
Allegheny	52	129	175	9	→ stable	PM2.5
Armstrong	41	108	275	1	→ stable	Ozone
Beaver	46	112	212	1	→ stable	Ozone
Berks	43	105	254	2	→ stable	Ozone
Blair	37	100	296	0	→ stable	Ozone
Bradford	37	75	298	0	→ stable	Ozone
Bucks	36	150	293	10	→ stable	Ozone
Cambria	42	87	269	0	→ stable	PM2.5
Centre	40	97	287	0	→ stable	Ozone
Chester	41	143	264	3	↓ improving	Ozone
Clearfield	35	97	215	0	→ stable	Ozone
Cumberland	36	93	260	0	↓ improving	PM2.5
Dauphin	48	105	206	2	→ stable	PM2.5
Delaware	43	136	250	2	→ stable	PM2.5
Elk	34	67	343	0	→ stable	Ozone
Erie	38	93	295	0	↓ improving	Ozone
Fayette	42	101	269	2	→ stable	Ozone
Franklin	35	90	305	0	→ stable	Ozone
Greene	38	87	196	0	→ stable	Ozone
Indiana	37	74	291	0	→ stable	Ozone
Lackawanna	40	97	265	0	→ stable	Ozone
Lancaster	50	125	189	3	→ stable	PM2.5
Lawrence	24	31	31	0	→ stable	Ozone
Lebanon	43	108	242	2	↓ improving	PM2.5
Lehigh	39	119	267	2	→ stable	Ozone
Luzerne	37	74	224	0	→ stable	Ozone
Lycoming	39	122	281	1	↑ worsening	Ozone
Mercer	40	97	274	0	↓ improving	Ozone
Monroe	35	119	329	1	↓ improving	Ozone
Montgomery	40	140	266	1	→ stable	Ozone
Northampton	39	105	278	1	↓ improving	Ozone
Philadelphia	52	136	173	10	→ stable	PM2.5
Somerset	37	90	323	0	→ stable	Ozone
Susquehanna	25	64	321	0	→ stable	PM2.5
Tioga	36	84	316	0	→ stable	Ozone
Washington	44	105	224	1	→ stable	Ozone
Westmoreland	39	88	278	0	↓ improving	PM2.5
Wyoming	26	68	319	0	↓ improving	PM2.5
York	44	101	240	1	→ stable	Ozone