Bad Air Days in Tooele County, Utah: 8 a Year

8 bad air days a year

More bad air days than three quarters of monitored counties. Ranked 128 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (34% particle days).

When the bad days come in Tooele

Most bad days here fall in August and July and September. Averaged over 2016 to 2025.

What to buy, and what not to

Ozone drives many bad days here. Purifiers and filters do not remove ozone, so do not buy one for that. Ozone peaks on hot afternoons: exercise outside in the morning.

Better or worse than it was

In 2000 to 2009 this county averaged 12 bad days a year; in 2016 to 2025, 8. The air has improved. The worst recent year was 2017, with 17 bad days on 365 monitored days.

Date	AQI	Main pollutant
2016-06-27	166	Ozone
2020-08-21	162	PM2.5
2021-08-18	157	PM2.5
2021-08-06	154	PM2.5
2017-07-08	147	Ozone

Most days, not the worst ones

Across 3,653 monitored days from 2016 to 2025, the air in Tooele County rated Good on 66% of them, less often than the 72% typical of monitored counties, and Moderate on 31%. The median day sat at AQI 45; one day in ten went above 72.

The pollutant setting the AQI on an ordinary day here:

ozone73%2,659 days
fine particles (PM2.5)27%990 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	271	93	1	0	44	101
2024	366	227	127	12	0	46	143
2023	365	248	117	0	0	45	97
2022	365	248	111	6	0	44	119
2021	365	229	120	16	2	43	157
2020	366	253	108	5	1	43	162
2019	365	286	77	2	0	44	117
2018	365	204	151	10	0	47	138
2017	365	209	139	17	0	48	147
2016	366	252	107	7	1	44	166
2015	365	299	62	4	0	33	143
2014	365	289	75	1	0	39	105
2013	343	210	118	15	0	47	147
2012	366	225	134	7	1	46	169
2011	364	231	126	7	0	47	119
2010	365	174	181	10	2	51	162

*2025 may be a partial year in EPA's file.

Nearby counties on file

How this is counted

A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.