EnviroNearby

Iron County, Utah air quality history

Daily Air Quality Index summaries from EPA monitors in Iron, Utah, 1988–2025.

75%
Good days in 2025
44
Median daily AQI, 2025
1
Days above 100 in 2025
364
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Iron, Utah on 364 days. 272 of those days (75%) were in the Good range, and the median daily AQI was 44. That median is about the same as the typical monitored county in Utah (median 45 across 15 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 298 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 81% in 2018–2020 versus 81% in 2023–2025.

Years with fewer than 120 monitored days (1992, 1993, 1994, 1995, 1996, 1997…) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1988: Good 13 of 13 days19881989: Good 57 of 60 days1989: Moderate 3 of 60 days1990: Good 51 of 53 days1990: Moderate 2 of 53 days19901991: Good 55 of 59 days1991: Moderate 4 of 59 days1992: Good 54 of 58 days1992: Moderate 4 of 58 days19921993: Good 56 of 57 days1993: Moderate 1 of 57 days1994: Good 58 of 60 days1994: Moderate 2 of 60 days19941995: Good 57 of 57 days1996: Good 57 of 57 days19961997: Good 56 of 56 days2018: Good 257 of 365 days2018: Moderate 108 of 365 days20182019: Good 320 of 365 days2019: Moderate 45 of 365 days2020: Good 312 of 366 days2020: Moderate 54 of 366 days20202021: Good 286 of 365 days2021: Moderate 75 of 365 days2021: Unhealthy for Sensitive Groups 3 of 365 days2021: Unhealthy 1 of 365 days2022: Good 309 of 365 days2022: Moderate 56 of 365 days20222023: Good 309 of 365 days2023: Moderate 55 of 365 days2023: Unhealthy for Sensitive Groups 1 of 365 days2024: Good 303 of 365 days2024: Moderate 62 of 365 days20242025: Good 272 of 364 days2025: Moderate 91 of 364 days2025: Unhealthy for Sensitive Groups 1 of 364 days2025
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001988: 90th percentile AQI 461989: 90th percentile AQI 381990: 90th percentile AQI 311991: 90th percentile AQI 441992: 90th percentile AQI 341993: 90th percentile AQI 361994: 90th percentile AQI 311995: 90th percentile AQI 251996: 90th percentile AQI 271997: 90th percentile AQI 242018: 90th percentile AQI 712019: 90th percentile AQI 522020: 90th percentile AQI 532021: 90th percentile AQI 622022: 90th percentile AQI 542023: 90th percentile AQI 542024: 90th percentile AQI 552025: 90th percentile AQI 641988: Median AQI 221989: Median AQI 211990: Median AQI 171991: Median AQI 181992: Median AQI 191993: Median AQI 191994: Median AQI 181995: Median AQI 171996: Median AQI 151997: Median AQI 162018: Median AQI 442019: Median AQI 432020: Median AQI 412021: Median AQI 402022: Median AQI 422023: Median AQI 422024: Median AQI 432025: Median AQI 441988199019921994199620182020202220242025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Ozone29882%
Fine particles (PM2.5)6518%
Nitrogen dioxide (NO₂)1<1%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253642729110004464105Ozone
20243653036200004355100Ozone
20233653095510004254103Ozone
2022365309560000425480Ozone
20213652867531004062176Ozone
2020366312540000415388Ozone
2019365320450000435284Ozone
20183652571080000447190Ozone
1997565600000162430PM10
1996575700000152741PM10
1995575700000172543PM10
1994605820000183169PM10
1993575610000193656PM10
1992585440000193466PM10
1991595540000184463PM10
1990535120000173168PM10
1989605730000213886PM10
1988131300000224646PM10

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Utah with a similar median AQI in 2025

All monitored counties in Utah

Source: U.S. EPA AirData, “Annual AQI by County” files for 1988–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem