Air Quality in Maryland

Maryland has 16 counties with EPA air quality monitoring. Air quality is generally improving across the state, with an average of 250 "Good" days per county per year. The best air quality is in Howard (median AQI 32) and the most polluted is Baltimore (median AQI 45).

County	Median AQI	Max AQI	Good Days	Unhealthy Days	Trend	Top Pollutant
Anne Arundel	40	129	186	1	↓ improving	Ozone
Baltimore	45	115	240	5	→ stable	Ozone
Baltimore (City)	42	112	258	6	↓ improving	Ozone
Calvert	41	108	203	1	→ stable	Ozone
Carroll	42	93	189	0	→ stable	Ozone
Cecil	44	126	236	3	→ stable	PM2.5
Charles	40	119	209	2	→ stable	Ozone
Dorchester	40	108	294	1	→ stable	Ozone
Frederick	43	100	192	0	→ stable	Ozone
Garrett	39	87	311	0	→ stable	Ozone
Harford	42	154	262	6	→ stable	Ozone
Howard	32	75	307	0	↓ improving	PM2.5
Kent	40	105	289	2	↓ improving	Ozone
Montgomery	40	100	271	0	→ stable	Ozone
Prince George's	39	129	280	3	↓ improving	Ozone
Washington	40	90	287	0	→ stable	Ozone