Air Quality in Idaho

Idaho has 20 counties with EPA air quality monitoring. Air quality is stable across the state, with an average of 250 "Good" days per county per year. The best air quality is in Custer (median AQI 6) and the most polluted is Boise (median AQI 48).

County	Median AQI	Max AQI	Good Days	Unhealthy Days	Trend	Top Pollutant
Ada	44	214	230	35	→ stable	Ozone
Bannock	39	104	286	2	↑ worsening	PM2.5
Benewah	43	112	225	4	→ stable	PM2.5
Blaine	19	220	310	6	↑ worsening	PM2.5
Boise	48	265	189	49	→ stable	PM2.5
Bonner	32	125	272	4	→ stable	PM2.5
Bonneville	22	91	316	0	↓ improving	PM2.5
Butte	42	97	303	0	→ stable	Ozone
Canyon	36	183	248	15	→ stable	PM2.5
Custer	6	152	94	6	↓ improving	PM2.5
Franklin	22	88	304	0	↓ improving	PM2.5
Idaho	42	217	237	8	→ stable	PM2.5
Jerome	13	49	213	0	↓ improving	PM2.5
Kootenai	24	109	291	1	↓ improving	PM2.5
Latah	27	117	297	1	↑ worsening	PM2.5
Lemhi	37	198	207	16	→ stable	PM2.5
Nez Perce	29	182	276	8	→ stable	PM2.5
Shoshone	46	112	209	1	→ stable	PM2.5
Twin Falls	23	158	264	7	↓ improving	PM2.5
Valley	37	155	235	9	↑ worsening	PM2.5