EnviroNearby

Monroe County, Missouri air quality history

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

94%
Good days in 2025
35
Median daily AQI, 2025
0
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 Monroe, Missouri on 365 days. 343 of those days (94%) were in the Good range, and the median daily AQI was 35. 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 353 days. Across the years with fuller monitoring, the share of Good days rose: an average of 79% in 1988–1990 versus 93% in 2023–2025.

Years with fewer than 120 monitored days (1987) 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 77 of 82 days1987: Moderate 3 of 82 days1987: Unhealthy for Sensitive Groups 2 of 82 days19871988: Good 217 of 331 days1988: Moderate 57 of 331 days1988: Unhealthy for Sensitive Groups 45 of 331 days1988: Unhealthy 12 of 331 days1989: Good 251 of 310 days1989: Moderate 51 of 310 days1989: Unhealthy for Sensitive Groups 8 of 310 days1990: Good 307 of 342 days1990: Moderate 33 of 342 days1990: Unhealthy for Sensitive Groups 2 of 342 days1991: Good 300 of 362 days1991: Moderate 46 of 362 days1991: Unhealthy for Sensitive Groups 13 of 362 days1991: Unhealthy 3 of 362 days1992: Good 233 of 295 days1992: Moderate 42 of 295 days1992: Unhealthy for Sensitive Groups 16 of 295 days1992: Unhealthy 4 of 295 days19921993: Good 219 of 278 days1993: Moderate 53 of 278 days1993: Unhealthy for Sensitive Groups 6 of 278 days1994: Good 200 of 313 days1994: Moderate 83 of 313 days1994: Unhealthy for Sensitive Groups 29 of 313 days1994: Unhealthy 1 of 313 days1995: Good 161 of 241 days1995: Moderate 56 of 241 days1995: Unhealthy for Sensitive Groups 21 of 241 days1995: Unhealthy 3 of 241 days1996: Good 155 of 240 days1996: Moderate 65 of 240 days1996: Unhealthy for Sensitive Groups 15 of 240 days1996: Unhealthy 5 of 240 days1997: Good 155 of 239 days1997: Moderate 69 of 239 days1997: Unhealthy for Sensitive Groups 14 of 239 days1997: Unhealthy 1 of 239 days19971998: Good 150 of 235 days1998: Moderate 72 of 235 days1998: Unhealthy for Sensitive Groups 12 of 235 days1998: Unhealthy 1 of 235 days1999: Good 132 of 256 days1999: Moderate 86 of 256 days1999: Unhealthy for Sensitive Groups 32 of 256 days1999: Unhealthy 6 of 256 days2000: Good 142 of 262 days2000: Moderate 112 of 262 days2000: Unhealthy for Sensitive Groups 8 of 262 days2001: Good 126 of 259 days2001: Moderate 125 of 259 days2001: Unhealthy for Sensitive Groups 7 of 259 days2001: Unhealthy 1 of 259 days2002: Good 137 of 264 days2002: Moderate 107 of 264 days2002: Unhealthy for Sensitive Groups 17 of 264 days2002: Unhealthy 3 of 264 days20022003: Good 141 of 259 days2003: Moderate 106 of 259 days2003: Unhealthy for Sensitive Groups 11 of 259 days2003: Unhealthy 1 of 259 days2004: Good 191 of 264 days2004: Moderate 73 of 264 days2005: Good 131 of 259 days2005: Moderate 111 of 259 days2005: Unhealthy for Sensitive Groups 17 of 259 days2006: Good 156 of 251 days2006: Moderate 89 of 251 days2006: Unhealthy for Sensitive Groups 6 of 251 days2007: Good 163 of 234 days2007: Moderate 62 of 234 days2007: Unhealthy for Sensitive Groups 9 of 234 days20072008: Good 209 of 239 days2008: Moderate 29 of 239 days2008: Unhealthy for Sensitive Groups 1 of 239 days2009: Good 211 of 232 days2009: Moderate 21 of 232 days2010: Good 194 of 227 days2010: Moderate 30 of 227 days2010: Unhealthy for Sensitive Groups 3 of 227 days2011: Good 263 of 302 days2011: Moderate 36 of 302 days2011: Unhealthy for Sensitive Groups 3 of 302 days2012: Good 296 of 365 days2012: Moderate 60 of 365 days2012: Unhealthy for Sensitive Groups 9 of 365 days20122013: Good 335 of 364 days2013: Moderate 29 of 364 days2014: Good 345 of 365 days2014: Moderate 19 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 355 of 365 days2015: Moderate 10 of 365 days2016: Good 353 of 366 days2016: Moderate 13 of 366 days2017: Good 344 of 365 days2017: Moderate 21 of 365 days20172018: Good 336 of 365 days2018: Moderate 28 of 365 days2018: Unhealthy for Sensitive Groups 1 of 365 days2019: Good 357 of 365 days2019: Moderate 8 of 365 days2020: Good 360 of 366 days2020: Moderate 6 of 366 days2021: Good 359 of 365 days2021: Moderate 6 of 365 days2022: Good 364 of 365 days2022: Moderate 1 of 365 days20222023: Good 317 of 364 days2023: Moderate 44 of 364 days2023: Unhealthy for Sensitive Groups 3 of 364 days2024: Good 357 of 366 days2024: Moderate 9 of 366 days2025: Good 343 of 365 days2025: Moderate 22 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 461988: 90th percentile AQI 1291989: 90th percentile AQI 711990: 90th percentile AQI 511991: 90th percentile AQI 671992: 90th percentile AQI 801993: 90th percentile AQI 671994: 90th percentile AQI 1001995: 90th percentile AQI 1001996: 90th percentile AQI 931997: 90th percentile AQI 901998: 90th percentile AQI 931999: 90th percentile AQI 1082000: 90th percentile AQI 802001: 90th percentile AQI 872002: 90th percentile AQI 902003: 90th percentile AQI 902004: 90th percentile AQI 592005: 90th percentile AQI 932006: 90th percentile AQI 782007: 90th percentile AQI 842008: 90th percentile AQI 512009: 90th percentile AQI 502010: 90th percentile AQI 642011: 90th percentile AQI 542012: 90th percentile AQI 742013: 90th percentile AQI 492014: 90th percentile AQI 472015: 90th percentile AQI 442016: 90th percentile AQI 442017: 90th percentile AQI 482018: 90th percentile AQI 492019: 90th percentile AQI 452020: 90th percentile AQI 432021: 90th percentile AQI 442022: 90th percentile AQI 442023: 90th percentile AQI 582024: 90th percentile AQI 452025: 90th percentile AQI 471987: Median AQI 281988: Median AQI 401989: Median AQI 351990: Median AQI 321991: Median AQI 361992: Median AQI 371993: Median AQI 391994: Median AQI 441995: Median AQI 461996: Median AQI 451997: Median AQI 461998: Median AQI 461999: Median AQI 502000: Median AQI 482001: Median AQI 512002: Median AQI 502003: Median AQI 482004: Median AQI 432005: Median AQI 502006: Median AQI 462007: Median AQI 442008: Median AQI 402009: Median AQI 372010: Median AQI 412011: Median AQI 402012: Median AQI 322013: Median AQI 352014: Median AQI 342015: Median AQI 312016: Median AQI 322017: Median AQI 372018: Median AQI 352019: Median AQI 352020: Median AQI 312021: Median AQI 322022: Median AQI 342023: Median AQI 382024: Median AQI 352025: Median AQI 35198719921997200220072012201720222025
  • 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
Ozone35397%
Coarse particles (PM10)113%
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
2025365343220000354797Ozone
202436635790000354584Ozone
20233643174430003858119Ozone
202236536410000344452Ozone
202136535960000324471Ozone
202036636060000314384Ozone
201936535780000354571Ozone
20183653362810003549105Ozone
2017365344210000374887Ozone
2016366353130000324487Ozone
2015365355100000314480Ozone
20143653451910003447101Ozone
2013364335290000354987Ozone
20123652966090003274140Ozone
20113022633630004054119Ozone
20102271943030004164115Ozone
2009232211210000375087Ozone
20082392092910004051101Ozone
20072341636290004484150Ozone
20062511568960004678150Ozone
2005259131111170005093136Ozone
2004264191730000435993Ozone
2003259141106111004890182Ozone
2002264137107173005090159Ozone
200125912612571005187156Ozone
200026214211280004880147Ozone
1999256132863260050108200Ozone
199823515072121004693159Ozone
199723915569141004690156Ozone
199624015565155004593164Ozone
1995241161562130046100154Ozone
1994313200832910044100177Ozone
19932782195360003967129Ozone
199229523342164003780182Ozone
199136230046133003667172Ozone
19903423073320003251140Ozone
19893102515180003571129Ozone
19883312175745120040129179Ozone
19878277320002846108Ozone

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