EnviroNearby

Duchesne County, Utah air quality history

Daily Air Quality Index summaries from EPA monitors in Duchesne, Utah, 1987–2025.

60%
Good days in 2025
46
Median daily AQI, 2025
2
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Duchesne, Utah on 365 days. 218 of those days (60%) were in the Good range, and the median daily AQI was 46. 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 rose: an average of 53% in 2011–2013 versus 57% in 2023–2025.

Years with fewer than 120 monitored days (1988, 2002, 2003, 2004, 2005, 2006…) 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%1987: Good 13 of 14 days1987: Moderate 1 of 14 days19871988: Good 39 of 44 days1988: Moderate 5 of 44 days2002: Good 15 of 15 days20022003: Good 55 of 55 days2004: Good 56 of 56 days20042005: Good 52 of 52 days2006: Good 50 of 50 days20062011: Good 207 of 365 days2011: Moderate 135 of 365 days2011: Unhealthy for Sensitive Groups 17 of 365 days2011: Unhealthy 2 of 365 days2011: Very Unhealthy 4 of 365 days2012: Good 206 of 366 days2012: Moderate 151 of 366 days2012: Unhealthy for Sensitive Groups 9 of 366 days20122013: Good 171 of 365 days2013: Moderate 150 of 365 days2013: Unhealthy for Sensitive Groups 17 of 365 days2013: Unhealthy 22 of 365 days2013: Very Unhealthy 5 of 365 days2014: Good 268 of 365 days2014: Moderate 95 of 365 days2014: Unhealthy for Sensitive Groups 2 of 365 days20142015: Good 269 of 365 days2015: Moderate 93 of 365 days2015: Unhealthy for Sensitive Groups 3 of 365 days2016: Good 268 of 366 days2016: Moderate 90 of 366 days2016: Unhealthy for Sensitive Groups 5 of 366 days2016: Unhealthy 3 of 366 days20162017: Good 261 of 365 days2017: Moderate 95 of 365 days2017: Unhealthy for Sensitive Groups 6 of 365 days2017: Unhealthy 3 of 365 days2018: Good 209 of 365 days2018: Moderate 145 of 365 days2018: Unhealthy for Sensitive Groups 11 of 365 days20182019: Good 226 of 365 days2019: Moderate 128 of 365 days2019: Unhealthy for Sensitive Groups 7 of 365 days2019: Unhealthy 4 of 365 days2020: Good 239 of 366 days2020: Moderate 122 of 366 days2020: Unhealthy for Sensitive Groups 5 of 366 days20202021: Good 220 of 365 days2021: Moderate 137 of 365 days2021: Unhealthy for Sensitive Groups 7 of 365 days2021: Unhealthy 1 of 365 days2022: Good 223 of 365 days2022: Moderate 138 of 365 days2022: Unhealthy for Sensitive Groups 3 of 365 days2022: Unhealthy 1 of 365 days20222023: Good 180 of 365 days2023: Moderate 151 of 365 days2023: Unhealthy for Sensitive Groups 22 of 365 days2023: Unhealthy 11 of 365 days2023: Very Unhealthy 1 of 365 days2024: Good 225 of 366 days2024: Moderate 136 of 366 days2024: Unhealthy for Sensitive Groups 3 of 366 days2024: Unhealthy 2 of 366 days20242025: Good 218 of 365 days2025: Moderate 145 of 365 days2025: Unhealthy for Sensitive Groups 2 of 365 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 year0501001501987: 90th percentile AQI 471988: 90th percentile AQI 512002: 90th percentile AQI 172003: 90th percentile AQI 142004: 90th percentile AQI 142005: 90th percentile AQI 142006: 90th percentile AQI 142011: 90th percentile AQI 802012: 90th percentile AQI 802013: 90th percentile AQI 1122014: 90th percentile AQI 612015: 90th percentile AQI 652016: 90th percentile AQI 642017: 90th percentile AQI 642018: 90th percentile AQI 842019: 90th percentile AQI 722020: 90th percentile AQI 682021: 90th percentile AQI 772022: 90th percentile AQI 722023: 90th percentile AQI 992024: 90th percentile AQI 702025: 90th percentile AQI 741987: Median AQI 191988: Median AQI 192002: Median AQI 112003: Median AQI 72004: Median AQI 62005: Median AQI 72006: Median AQI 62011: Median AQI 492012: Median AQI 482013: Median AQI 512014: Median AQI 462015: Median AQI 452016: Median AQI 452017: Median AQI 452018: Median AQI 472019: Median AQI 482020: Median AQI 462021: Median AQI 482022: Median AQI 482023: Median AQI 512024: Median AQI 472025: Median AQI 46198720022004200620122014201620182020202220242025
  • 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)6317%
Coarse particles (PM10)41%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536521814520004674112Ozone
202436622513632004770165Ozone
20233651801512211105199215Ozone
202236522313831004872177Ozone
202136522013771004877155Ozone
202036623912250004668125Ozone
201936522612874004872177Ozone
2018365209145110004784129Ozone
20173652619563004564156Ozone
20163662689053004564177Ozone
20153652699330004565129Ozone
20143652689520004661119Ozone
201336517115017225051112213Ozone
201236620615190004880146Ozone
2011365207135172404980220Ozone
200650500000061417PM10
200552520000071422PM10
200456560000061420PM10
200355550000071433PM10
2002151500000111720PM10
1988443950000195155PM10
1987141310000194756PM10

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 1987–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem