EnviroNearby

Boone County, Missouri air quality history

Daily Air Quality Index summaries from EPA monitors in Boone, Missouri, 1987–2025.

93%
Good days in 2025
37
Median daily AQI, 2025
0
Days above 100 in 2025
248
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Boone, Missouri on 248 days. 231 of those days (93%) were in the Good range, and the median daily AQI was 37. That median is lower than the typical monitored county in Missouri (median 41 across 19 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 248 days. Across the years with fuller monitoring, the share of Good days rose: an average of 85% in 2009–2011 versus 89% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (248 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

Years with fewer than 120 monitored days (1990, 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 26 of 27 days1987: Moderate 1 of 27 days19871988: Good 40 of 42 days1988: Moderate 2 of 42 days1989: Good 56 of 57 days1989: Moderate 1 of 57 days19891990: Good 44 of 44 days2002: Good 31 of 87 days2002: Moderate 56 of 87 days20022003: Good 40 of 115 days2003: Moderate 74 of 115 days2003: Unhealthy for Sensitive Groups 1 of 115 days2004: Good 53 of 112 days2004: Moderate 59 of 112 days20042005: Good 43 of 112 days2005: Moderate 67 of 112 days2005: Unhealthy for Sensitive Groups 2 of 112 days2006: Good 26 of 60 days2006: Moderate 34 of 60 days20062009: Good 195 of 214 days2009: Moderate 19 of 214 days2010: Good 178 of 214 days2010: Moderate 34 of 214 days2010: Unhealthy for Sensitive Groups 2 of 214 days20102011: Good 200 of 245 days2011: Moderate 42 of 245 days2011: Unhealthy for Sensitive Groups 3 of 245 days2012: Good 138 of 212 days2012: Moderate 61 of 212 days2012: Unhealthy for Sensitive Groups 13 of 212 days20122013: Good 178 of 214 days2013: Moderate 36 of 214 days2014: Good 190 of 214 days2014: Moderate 24 of 214 days20142015: Good 197 of 214 days2015: Moderate 17 of 214 days2016: Good 198 of 214 days2016: Moderate 16 of 214 days20162017: Good 219 of 245 days2017: Moderate 26 of 245 days2018: Good 208 of 245 days2018: Moderate 36 of 245 days2018: Unhealthy for Sensitive Groups 1 of 245 days20182019: Good 239 of 245 days2019: Moderate 6 of 245 days2020: Good 235 of 244 days2020: Moderate 9 of 244 days20202021: Good 233 of 245 days2021: Moderate 12 of 245 days2022: Good 235 of 245 days2022: Moderate 10 of 245 days20222023: Good 195 of 244 days2023: Moderate 44 of 244 days2023: Unhealthy for Sensitive Groups 5 of 244 days2024: Good 248 of 263 days2024: Moderate 15 of 263 days20242025: Good 231 of 248 days2025: Moderate 17 of 248 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 year0501001987: 90th percentile AQI 431988: 90th percentile AQI 451989: 90th percentile AQI 401990: 90th percentile AQI 342002: 90th percentile AQI 742003: 90th percentile AQI 752004: 90th percentile AQI 652005: 90th percentile AQI 752006: 90th percentile AQI 662009: 90th percentile AQI 502010: 90th percentile AQI 612011: 90th percentile AQI 612012: 90th percentile AQI 932013: 90th percentile AQI 582014: 90th percentile AQI 512015: 90th percentile AQI 492016: 90th percentile AQI 492017: 90th percentile AQI 512018: 90th percentile AQI 542019: 90th percentile AQI 462020: 90th percentile AQI 442021: 90th percentile AQI 472022: 90th percentile AQI 482023: 90th percentile AQI 672024: 90th percentile AQI 482025: 90th percentile AQI 491987: Median AQI 231988: Median AQI 251989: Median AQI 241990: Median AQI 212002: Median AQI 562003: Median AQI 542004: Median AQI 512005: Median AQI 552006: Median AQI 532009: Median AQI 372010: Median AQI 402011: Median AQI 432012: Median AQI 452013: Median AQI 422014: Median AQI 382015: Median AQI 382016: Median AQI 372017: Median AQI 412018: Median AQI 402019: Median AQI 382020: Median AQI 332021: Median AQI 372022: Median AQI 382023: Median AQI 422024: Median AQI 392025: Median AQI 3719871989200220042006201020122014201620182020202220242025
  • 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
Ozone248100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025248231170000374987Ozone
2024263248150000394877Ozone
20232441954450004267143Ozone
2022245235100000384867Ozone
2021245233120000374777Ozone
202024423590000334493Ozone
201924523960000384671Ozone
20182452083610004054105Ozone
2017245219260000415177Ozone
2016214198160000374997Ozone
2015214197170000384990Ozone
2014214190240000385187Ozone
2013214178360000425897Ozone
201221213861130004593150Ozone
20112452004230004361112Ozone
20102141783420004061101Ozone
20092141951900003750100Ozone
20066026340000536676PM2.5
2005112436720005575105PM2.5
200411253590000516588PM2.5
2003115407410005475113PM2.5
20028731560000567490PM2.5
1990444400000213439PM10
1989575610000244051PM10
1988424020000254557PM10
1987272610000234358PM10

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 Missouri with a similar median AQI in 2025

All monitored counties in Missouri

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