EnviroNearby

Monongalia County, West Virginia air quality history

Daily Air Quality Index summaries from EPA monitors in Monongalia, West Virginia, 1995–2025.

80%
Good days in 2025
42
Median daily AQI, 2025
1
Days above 100 in 2025
272
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Monongalia, West Virginia on 272 days. 217 of those days (80%) were in the Good range, and the median daily AQI was 42. That median is higher than the typical monitored county in West Virginia (median 39 across 12 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 207 days. Across the years with fuller monitoring, the share of Good days rose: an average of 48% in 2000–2002 versus 80% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (272 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 (1995, 1996, 1997, 1998, 1999) 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%1995: Good 28 of 30 days1995: Moderate 2 of 30 days19951996: Good 58 of 60 days1996: Moderate 2 of 60 days1997: Good 55 of 58 days1997: Moderate 3 of 58 days1998: Good 59 of 60 days1998: Moderate 1 of 60 days1999: Good 32 of 118 days1999: Moderate 83 of 118 days1999: Unhealthy for Sensitive Groups 3 of 118 days2000: Good 121 of 250 days2000: Moderate 118 of 250 days2000: Unhealthy for Sensitive Groups 9 of 250 days2000: Unhealthy 2 of 250 days20002001: Good 115 of 258 days2001: Moderate 131 of 258 days2001: Unhealthy for Sensitive Groups 12 of 258 days2002: Good 129 of 257 days2002: Moderate 101 of 257 days2002: Unhealthy for Sensitive Groups 22 of 257 days2002: Unhealthy 5 of 257 days2003: Good 135 of 263 days2003: Moderate 119 of 263 days2003: Unhealthy for Sensitive Groups 7 of 263 days2003: Unhealthy 2 of 263 days2004: Good 139 of 260 days2004: Moderate 120 of 260 days2004: Unhealthy for Sensitive Groups 1 of 260 days2005: Good 123 of 261 days2005: Moderate 122 of 261 days2005: Unhealthy for Sensitive Groups 15 of 261 days2005: Unhealthy 1 of 261 days20052006: Good 141 of 263 days2006: Moderate 112 of 263 days2006: Unhealthy for Sensitive Groups 10 of 263 days2007: Good 116 of 261 days2007: Moderate 131 of 261 days2007: Unhealthy for Sensitive Groups 14 of 261 days2008: Good 162 of 263 days2008: Moderate 100 of 263 days2008: Unhealthy for Sensitive Groups 1 of 263 days2009: Good 152 of 361 days2009: Moderate 209 of 361 days2010: Good 143 of 259 days2010: Moderate 109 of 259 days2010: Unhealthy for Sensitive Groups 7 of 259 days20102011: Good 170 of 257 days2011: Moderate 86 of 257 days2011: Unhealthy for Sensitive Groups 1 of 257 days2012: Good 167 of 261 days2012: Moderate 88 of 261 days2012: Unhealthy for Sensitive Groups 6 of 261 days2013: Good 183 of 248 days2013: Moderate 64 of 248 days2013: Unhealthy for Sensitive Groups 1 of 248 days2014: Good 201 of 261 days2014: Moderate 60 of 261 days2015: Good 184 of 254 days2015: Moderate 68 of 254 days2015: Unhealthy for Sensitive Groups 2 of 254 days20152016: Good 216 of 260 days2016: Moderate 44 of 260 days2017: Good 242 of 282 days2017: Moderate 40 of 282 days2018: Good 236 of 278 days2018: Moderate 42 of 278 days2019: Good 237 of 277 days2019: Moderate 40 of 277 days2020: Good 248 of 274 days2020: Moderate 26 of 274 days20202021: Good 225 of 282 days2021: Moderate 57 of 282 days2022: Good 250 of 280 days2022: Moderate 30 of 280 days2023: Good 227 of 277 days2023: Moderate 49 of 277 days2023: Unhealthy 1 of 277 days2024: Good 211 of 267 days2024: Moderate 56 of 267 days2025: Good 217 of 272 days2025: Moderate 54 of 272 days2025: Unhealthy for Sensitive Groups 1 of 272 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 year0501001501995: 90th percentile AQI 461996: 90th percentile AQI 401997: 90th percentile AQI 451998: 90th percentile AQI 381999: 90th percentile AQI 822000: 90th percentile AQI 852001: 90th percentile AQI 902002: 90th percentile AQI 1012003: 90th percentile AQI 842004: 90th percentile AQI 742005: 90th percentile AQI 932006: 90th percentile AQI 842007: 90th percentile AQI 872008: 90th percentile AQI 712009: 90th percentile AQI 672010: 90th percentile AQI 772011: 90th percentile AQI 672012: 90th percentile AQI 802013: 90th percentile AQI 592014: 90th percentile AQI 582015: 90th percentile AQI 642016: 90th percentile AQI 542017: 90th percentile AQI 532018: 90th percentile AQI 542019: 90th percentile AQI 542020: 90th percentile AQI 502021: 90th percentile AQI 582022: 90th percentile AQI 512023: 90th percentile AQI 592024: 90th percentile AQI 562025: 90th percentile AQI 581995: Median AQI 201996: Median AQI 221997: Median AQI 201998: Median AQI 181999: Median AQI 572000: Median AQI 512001: Median AQI 522002: Median AQI 502003: Median AQI 502004: Median AQI 472005: Median AQI 522006: Median AQI 492007: Median AQI 522008: Median AQI 462009: Median AQI 522010: Median AQI 492011: Median AQI 442012: Median AQI 442013: Median AQI 402014: Median AQI 412015: Median AQI 432016: Median AQI 382017: Median AQI 402018: Median AQI 382019: Median AQI 412020: Median AQI 392021: Median AQI 392022: Median AQI 372023: Median AQI 422024: Median AQI 432025: Median AQI 421995200020052010201520202025
  • 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
Ozone20776%
Fine particles (PM2.5)6524%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20252722175410004258105Ozone
2024267211560000435693Ozone
20232772274901004259169Ozone
2022280250300000375177Ozone
2021282225570000395880Ozone
2020274248260000395090Ozone
2019277237400000415474Ozone
2018278236420000385493Ozone
2017282242400000405390Ozone
2016260216440000385474Ozone
20152541846820004364133Ozone
2014261201600000415890Ozone
20132481836410004059115Ozone
20122611678860004480150Ozone
20112571708610004467119Ozone
201025914310970004977143Ozone
20093611522090000526797PM2.5
200826316210010004671101Ozone
2007261116131140005287140Ozone
2006263141112100004984147Ozone
2005261123122151005293161Ozone
200426013912010004774122Ozone
200326313511972005084179Ozone
20022571291012250050101177Ozone
2001258115131120005290136Ozone
200025012111892005185166Ozone
1999118328330005782116PM2.5
1998605910000183873PM10
1997585530000204552PM10
1996605820000224053PM10
1995302820000204660PM10

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 West Virginia with a similar median AQI in 2025

All monitored counties in West Virginia

Source: U.S. EPA AirData, “Annual AQI by County” files for 1995–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem