Air Quality in Montana

Montana has 25 counties with EPA air quality monitoring. Air quality is generally worsening across the state, with an average of 248 "Good" days per county per year. The best air quality is in Rosebud (median AQI 4) and the most polluted is Lincoln (median AQI 49).

County	Median AQI	Max AQI	Good Days	Unhealthy Days	Trend	Top Pollutant
Beaverhead	12	180	298	2	↑ worsening	PM2.5
Cascade	46	74	52	0	→ stable	PM2.5
Custer	36	153	328	2	↑ worsening	Ozone
Dawson	14	120	321	3	↑ worsening	PM2.5
Fergus	40	155	312	4	→ stable	Ozone
Flathead	42	95	253	0	→ stable	PM2.5
Gallatin	18	84	329	0	→ stable	PM2.5
Glacier	23	99	306	0	↑ worsening	PM2.5
Hill	15	123	314	2	↑ worsening	PM2.5
Lake	9	77	108	0	→ stable	PM2.5
Lewis and Clark	46	160	233	6	→ stable	Ozone
Lincoln	49	116	185	2	→ stable	PM2.5
Missoula	43	153	237	4	→ stable	PM2.5
Phillips	21	147	323	2	→ stable	PM2.5
Powder River	44	195	244	12	→ stable	Ozone
Powell	12	144	101	2	→ stable	PM2.5
Ravalli	24	182	254	16	↓ improving	PM2.5
Richland	36	118	307	5	→ stable	Ozone
Roosevelt	13	109	87	1	→ stable	PM2.5
Rosebud	4	90	353	0	↓ improving	PM2.5
Sanders	21	69	339	0	↑ worsening	PM10
Sheridan	17	126	104	2	→ stable	PM2.5
Silver Bow	31	168	258	5	↓ improving	PM2.5
Teton	13	101	286	1	↑ worsening	PM2.5
Yellowstone	39	105	272	1	→ stable	Ozone