Air Quality Rankings for Utah (2026)

Utah has 15 cities tracked by EPA air-quality monitors, with a state-wide 5-year median AQI of 43 — 2 points more polluted than the national average of AQI 41. Wayne, Utah ranks #1 with the cleanest air (AQI 11, Grade B), while Salt Lake, Utah sits at the bottom (AQI 57, Grade D). The rankings below are computed from the EPA Air Quality System (AQS), which aggregates daily AQI readings from federally certified monitors into annual averages. Cities are sorted by 5-year median AQI (lowest = cleanest = #1). The 5-year window smooths out year-to-year volatility from weather and wildfire events.

Utah is bucking the national trend of broad improvement: 7 of 15 monitored cities show measurably worse air over the past decade, more than the 5 that are improving. Across western states this usually traces back to expanding wildfire smoke exposure; elsewhere it can reflect rising local emissions from population or freight growth.

The dominant pollutant across 14 of 15 Utah cities is Ground-Level Ozone. Ground-level ozone forms when sunlight reacts with vehicle and industrial emissions. It is worst on hot, sunny, stagnant summer days and is the leading air quality concern across much of the Sun Belt and California. Other Utah cities report Fine Particulate Matter (PM2.5) (1) as their dominant concern.

The fastest-improving city in Utah is Box Elder, Utah, with median AQI falling by 1.0 points per year. Steady improvement at that pace usually reflects fleet turnover (older diesels retiring), upwind power-plant retirements, or tighter regional emissions controls.

The city with the steepest decline is Tooele, Utah, where median AQI is rising by 0.7 points per year. Rapid deterioration in a single city usually points to either wildfire-smoke exposure (in the West) or a new local emissions source — a power plant, port, or freight corridor coming online.