EnviroNearby

Oxford County, Maine air quality history

Daily Air Quality Index summaries from EPA monitors in Oxford, Maine, 1981–2025.

76%
Good days in 2025
38
Median daily AQI, 2025
3
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 Oxford, Maine on 365 days. 277 of those days (76%) were in the Good range, and the median daily AQI was 38. That median is higher than the typical monitored county in Maine (median 34 across 11 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 260 days. Across the years with fuller monitoring, the share of Good days fell: an average of 87% in 1982–1989 versus 82% in 2023–2025.

Years with fewer than 120 monitored days (1981, 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%1981: Good 117 of 117 days19811982: Good 157 of 207 days1982: Moderate 39 of 207 days1982: Unhealthy for Sensitive Groups 7 of 207 days1982: Unhealthy 4 of 207 days1987: Good 79 of 87 days1987: Moderate 8 of 87 days1988: Good 127 of 138 days1988: Moderate 11 of 138 days1989: Good 136 of 148 days1989: Moderate 12 of 148 days1990: Good 160 of 166 days1990: Moderate 6 of 166 days19901991: Good 178 of 180 days1991: Moderate 2 of 180 days1992: Good 233 of 248 days1992: Moderate 10 of 248 days1992: Unhealthy for Sensitive Groups 4 of 248 days1992: Unhealthy 1 of 248 days1993: Good 258 of 268 days1993: Moderate 10 of 268 days1994: Good 248 of 270 days1994: Moderate 20 of 270 days1994: Unhealthy for Sensitive Groups 2 of 270 days1995: Good 263 of 273 days1995: Moderate 7 of 273 days1995: Unhealthy for Sensitive Groups 2 of 273 days1995: Unhealthy 1 of 273 days19951996: Good 263 of 273 days1996: Moderate 9 of 273 days1996: Unhealthy for Sensitive Groups 1 of 273 days1997: Good 269 of 274 days1997: Moderate 5 of 274 days1998: Good 262 of 272 days1998: Moderate 9 of 272 days1998: Unhealthy for Sensitive Groups 1 of 272 days1999: Good 265 of 273 days1999: Moderate 7 of 273 days1999: Unhealthy for Sensitive Groups 1 of 273 days2000: Good 242 of 245 days2000: Moderate 3 of 245 days20002001: Good 195 of 212 days2001: Moderate 15 of 212 days2001: Unhealthy for Sensitive Groups 2 of 212 days2002: Good 194 of 209 days2002: Moderate 14 of 209 days2002: Unhealthy for Sensitive Groups 1 of 209 days2003: Good 201 of 210 days2003: Moderate 8 of 210 days2003: Unhealthy for Sensitive Groups 1 of 210 days2004: Good 208 of 213 days2004: Moderate 5 of 213 days2005: Good 176 of 183 days2005: Moderate 6 of 183 days2005: Unhealthy for Sensitive Groups 1 of 183 days20052006: Good 174 of 178 days2006: Moderate 4 of 178 days2007: Good 166 of 172 days2007: Moderate 2 of 172 days2007: Unhealthy for Sensitive Groups 4 of 172 days2008: Good 226 of 232 days2008: Moderate 6 of 232 days2009: Good 210 of 216 days2009: Moderate 6 of 216 days2010: Good 229 of 230 days2010: Moderate 1 of 230 days20102011: Good 196 of 199 days2011: Moderate 3 of 199 days2012: Good 209 of 213 days2012: Moderate 4 of 213 days2013: Good 200 of 204 days2013: Moderate 4 of 204 days2014: Good 237 of 248 days2014: Moderate 11 of 248 days2015: Good 249 of 340 days2015: Moderate 91 of 340 days20152016: Good 280 of 363 days2016: Moderate 83 of 363 days2017: Good 260 of 351 days2017: Moderate 91 of 351 days2018: Good 290 of 354 days2018: Moderate 64 of 354 days2019: Good 305 of 334 days2019: Moderate 29 of 334 days2020: Good 299 of 324 days2020: Moderate 25 of 324 days20202021: Good 308 of 360 days2021: Moderate 51 of 360 days2021: Unhealthy for Sensitive Groups 1 of 360 days2022: Good 324 of 358 days2022: Moderate 34 of 358 days2023: Good 288 of 356 days2023: Moderate 68 of 356 days2024: Good 326 of 364 days2024: Moderate 38 of 364 days2025: Good 277 of 365 days2025: Moderate 85 of 365 days2025: Unhealthy for Sensitive Groups 3 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 year0501001981: 90th percentile AQI 171982: 90th percentile AQI 741987: 90th percentile AQI 501988: 90th percentile AQI 501989: 90th percentile AQI 481990: 90th percentile AQI 351991: 90th percentile AQI 341992: 90th percentile AQI 441993: 90th percentile AQI 441994: 90th percentile AQI 481995: 90th percentile AQI 461996: 90th percentile AQI 451997: 90th percentile AQI 431998: 90th percentile AQI 441999: 90th percentile AQI 442000: 90th percentile AQI 422001: 90th percentile AQI 492002: 90th percentile AQI 472003: 90th percentile AQI 452004: 90th percentile AQI 442005: 90th percentile AQI 482006: 90th percentile AQI 442007: 90th percentile AQI 442008: 90th percentile AQI 442009: 90th percentile AQI 442010: 90th percentile AQI 462011: 90th percentile AQI 442012: 90th percentile AQI 442013: 90th percentile AQI 442014: 90th percentile AQI 442015: 90th percentile AQI 612016: 90th percentile AQI 592017: 90th percentile AQI 592018: 90th percentile AQI 582019: 90th percentile AQI 492020: 90th percentile AQI 472021: 90th percentile AQI 522022: 90th percentile AQI 502023: 90th percentile AQI 562024: 90th percentile AQI 512025: 90th percentile AQI 601981: Median AQI 71982: Median AQI 401987: Median AQI 251988: Median AQI 211989: Median AQI 241990: Median AQI 201991: Median AQI 171992: Median AQI 231993: Median AQI 291994: Median AQI 301995: Median AQI 311996: Median AQI 261997: Median AQI 251998: Median AQI 271999: Median AQI 262000: Median AQI 272001: Median AQI 302002: Median AQI 312003: Median AQI 302004: Median AQI 302005: Median AQI 322006: Median AQI 312007: Median AQI 312008: Median AQI 302009: Median AQI 292010: Median AQI 342011: Median AQI 312012: Median AQI 312013: Median AQI 302014: Median AQI 312015: Median AQI 392016: Median AQI 352017: Median AQI 402018: Median AQI 392019: Median AQI 332020: Median AQI 362021: Median AQI 352022: Median AQI 332023: Median AQI 382024: Median AQI 322025: Median AQI 38198119901995200020052010201520202025
  • 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
Fine particles (PM2.5)26071%
Ozone10529%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253652778530003860135PM2.5
2024364326380000325171Ozone
2023356288680000385683PM2.5
2022358324340000335096Ozone
20213603085110003552113PM2.5
2020324299250000364769Ozone
2019334305290000334972PM2.5
2018354290640000395898PM2.5
2017351260910000405987PM2.5
2016363280830000355990PM2.5
2015340249910000396190PM2.5
2014248237110000314490Ozone
201320420040000304487Ozone
201221320940000314487Ozone
201119919630000314471Ozone
201023022910000344654Ozone
200921621060000294467Ozone
200823222660000304484Ozone
2007172166240003144150Ozone
200617817440000314474Ozone
2005183176610003248101Ozone
200421320850000304493Ozone
2003210201810003045101Ozone
20022091941410003147150Ozone
20012121951520003049122Ozone
200024524230000274284Ozone
1999273265710002644119Ozone
1998272262910002744115Ozone
199727426950000254371Ozone
1996273263910002645143Ozone
1995273263721003146156Ozone
19942702482020003048150Ozone
1993268258100000294497Ozone
19922482331041002344159Ozone
199118017820000173476PM10
199016616060000203572PM10
1989148136120000244891PM10
1988138127110000215065PM10
1987877980000255077PM10
19822071573974004074197Ozone
19811171170000071742NO2

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 Maine with a similar median AQI in 2025

All monitored counties in Maine

Source: U.S. EPA AirData, “Annual AQI by County” files for 1981–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem