EnviroNearby

Aroostook County, Maine air quality history

Daily Air Quality Index summaries from EPA monitors in Aroostook, Maine, 1980–2025.

83%
Good days in 2025
32
Median daily AQI, 2025
4
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 Aroostook, Maine on 365 days. 304 of those days (83%) were in the Good range, and the median daily AQI was 32. That median is about the same as the typical monitored county in Maine (median 34 across 11 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 223 days. Across the years with fuller monitoring, the share of Good days fell: an average of 95% in 1980–1985 versus 80% in 2023–2025.

Years with fewer than 120 monitored days (1983, 1984) 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%1980: Good 138 of 138 days19801981: Good 153 of 153 days1983: Good 40 of 49 days1983: Moderate 9 of 49 days1984: Good 62 of 101 days1984: Moderate 36 of 101 days1984: Unhealthy for Sensitive Groups 3 of 101 days1985: Good 183 of 218 days1985: Moderate 35 of 218 days1986: Good 223 of 262 days1986: Moderate 37 of 262 days1986: Unhealthy for Sensitive Groups 2 of 262 days19861987: Good 291 of 329 days1987: Moderate 36 of 329 days1987: Unhealthy for Sensitive Groups 2 of 329 days1988: Good 265 of 293 days1988: Moderate 28 of 293 days1989: Good 270 of 318 days1989: Moderate 48 of 318 days1990: Good 310 of 365 days1990: Moderate 51 of 365 days1990: Unhealthy for Sensitive Groups 4 of 365 days1991: Good 319 of 364 days1991: Moderate 38 of 364 days1991: Unhealthy for Sensitive Groups 6 of 364 days1991: Unhealthy 1 of 364 days19911992: Good 323 of 366 days1992: Moderate 39 of 366 days1992: Unhealthy for Sensitive Groups 3 of 366 days1992: Unhealthy 1 of 366 days1993: Good 334 of 365 days1993: Moderate 30 of 365 days1993: Unhealthy for Sensitive Groups 1 of 365 days1994: Good 343 of 365 days1994: Moderate 21 of 365 days1994: Unhealthy for Sensitive Groups 1 of 365 days1995: Good 346 of 365 days1995: Moderate 19 of 365 days1996: Good 330 of 355 days1996: Moderate 25 of 355 days19961997: Good 351 of 365 days1997: Moderate 11 of 365 days1997: Unhealthy for Sensitive Groups 3 of 365 days1998: Good 333 of 365 days1998: Moderate 32 of 365 days1999: Good 330 of 365 days1999: Moderate 34 of 365 days1999: Unhealthy for Sensitive Groups 1 of 365 days2000: Good 344 of 366 days2000: Moderate 22 of 366 days2001: Good 312 of 365 days2001: Moderate 52 of 365 days2001: Unhealthy for Sensitive Groups 1 of 365 days20012002: Good 334 of 365 days2002: Moderate 29 of 365 days2002: Unhealthy for Sensitive Groups 1 of 365 days2002: Unhealthy 1 of 365 days2003: Good 337 of 365 days2003: Moderate 28 of 365 days2004: Good 342 of 366 days2004: Moderate 23 of 366 days2004: Unhealthy for Sensitive Groups 1 of 366 days2005: Good 341 of 365 days2005: Moderate 24 of 365 days2006: Good 286 of 365 days2006: Moderate 78 of 365 days2006: Unhealthy for Sensitive Groups 1 of 365 days20062007: Good 305 of 365 days2007: Moderate 57 of 365 days2007: Unhealthy for Sensitive Groups 3 of 365 days2008: Good 302 of 366 days2008: Moderate 64 of 366 days2009: Good 308 of 365 days2009: Moderate 57 of 365 days2010: Good 317 of 365 days2010: Moderate 47 of 365 days2010: Unhealthy for Sensitive Groups 1 of 365 days2011: Good 325 of 365 days2011: Moderate 40 of 365 days20112012: Good 323 of 366 days2012: Moderate 43 of 366 days2013: Good 323 of 365 days2013: Moderate 42 of 365 days2014: Good 221 of 365 days2014: Moderate 143 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 226 of 365 days2015: Moderate 139 of 365 days2016: Good 265 of 366 days2016: Moderate 100 of 366 days2016: Unhealthy 1 of 366 days20162017: Good 257 of 365 days2017: Moderate 107 of 365 days2017: Unhealthy for Sensitive Groups 1 of 365 days2018: Good 262 of 365 days2018: Moderate 101 of 365 days2018: Unhealthy 1 of 365 days2018: Very Unhealthy 1 of 365 days2019: Good 304 of 365 days2019: Moderate 59 of 365 days2019: Unhealthy for Sensitive Groups 1 of 365 days2019: Unhealthy 1 of 365 days2020: Good 316 of 366 days2020: Moderate 49 of 366 days2020: Very Unhealthy 1 of 366 days2021: Good 305 of 365 days2021: Moderate 58 of 365 days2021: Unhealthy for Sensitive Groups 1 of 365 days2021: Unhealthy 1 of 365 days20212022: Good 304 of 364 days2022: Moderate 60 of 364 days2023: Good 277 of 365 days2023: Moderate 85 of 365 days2023: Unhealthy for Sensitive Groups 3 of 365 days2024: Good 299 of 366 days2024: Moderate 67 of 366 days2025: Good 304 of 365 days2025: Moderate 57 of 365 days2025: Unhealthy for Sensitive Groups 4 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 year0501001980: 90th percentile AQI 291981: 90th percentile AQI 311983: 90th percentile AQI 681984: 90th percentile AQI 691985: 90th percentile AQI 561986: 90th percentile AQI 551987: 90th percentile AQI 521988: 90th percentile AQI 491989: 90th percentile AQI 551990: 90th percentile AQI 571991: 90th percentile AQI 541992: 90th percentile AQI 551993: 90th percentile AQI 481994: 90th percentile AQI 471995: 90th percentile AQI 451996: 90th percentile AQI 441997: 90th percentile AQI 441998: 90th percentile AQI 491999: 90th percentile AQI 502000: 90th percentile AQI 452001: 90th percentile AQI 552002: 90th percentile AQI 492003: 90th percentile AQI 462004: 90th percentile AQI 462005: 90th percentile AQI 472006: 90th percentile AQI 562007: 90th percentile AQI 552008: 90th percentile AQI 552009: 90th percentile AQI 552010: 90th percentile AQI 522011: 90th percentile AQI 512012: 90th percentile AQI 512013: 90th percentile AQI 512014: 90th percentile AQI 652015: 90th percentile AQI 642016: 90th percentile AQI 572017: 90th percentile AQI 582018: 90th percentile AQI 602019: 90th percentile AQI 552020: 90th percentile AQI 532021: 90th percentile AQI 542022: 90th percentile AQI 542023: 90th percentile AQI 592024: 90th percentile AQI 552025: 90th percentile AQI 571980: Median AQI 181981: Median AQI 201983: Median AQI 281984: Median AQI 401985: Median AQI 331986: Median AQI 261987: Median AQI 221988: Median AQI 271989: Median AQI 311990: Median AQI 341991: Median AQI 321992: Median AQI 331993: Median AQI 311994: Median AQI 341995: Median AQI 321996: Median AQI 271997: Median AQI 321998: Median AQI 341999: Median AQI 342000: Median AQI 332001: Median AQI 332002: Median AQI 342003: Median AQI 342004: Median AQI 322005: Median AQI 322006: Median AQI 382007: Median AQI 372008: Median AQI 372009: Median AQI 352010: Median AQI 352011: Median AQI 362012: Median AQI 352013: Median AQI 352014: Median AQI 442015: Median AQI 442016: Median AQI 392017: Median AQI 402018: Median AQI 422019: Median AQI 362020: Median AQI 362021: Median AQI 352022: Median AQI 342023: Median AQI 372024: Median AQI 352025: Median AQI 321980198619911996200120062011201620212025
  • 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)22361%
Ozone13036%
Coarse particles (PM10)123%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253653045740003257131PM2.5
2024366299670000355596PM2.5
20233652778530003759142PM2.5
2022364304600000345480PM2.5
20213653055811003554182Ozone
20203663164900103653205Ozone
20193653045911003655182PM2.5
201836526210101104260216PM2.5
201736525710710004058120PM2.5
201636626510001003957169PM2.5
20153652261390000446497PM2.5
201436522114310004465117PM2.5
2013365323420000355194Ozone
2012366323430000355173Ozone
2011365325400000365170PM2.5
20103653174710003552101Ozone
2009365308570000355597Ozone
2008366302640000375590PM2.5
20073653055730003755129PM2.5
20063652867810003856106PM2.5
2005365341240000324797Ozone
20043663422310003246112Ozone
2003365337280000344674Ozone
20023653342911003449156Ozone
20013653125210003355108Ozone
2000366344220000334590Ozone
19993653303410003450126Ozone
1998365333320000344987Ozone
19973653511130003244126Ozone
1996355330250000274480Ozone
1995365346190000324599Ozone
19943653432110003447122Ozone
19933653343010003148113Ozone
19923663233931003355159Ozone
19913643193861003254151Ozone
19903653105140003457136Ozone
1989318270480000315595PM10
19882932652800002749100PM10
19873292913620002252139PM10
19862622233720002655123PM10
1985218183350000335692PM10
1984101623630004069124PM10
1983494090000286882PM10
198115315300000203150Ozone
198013813800000182941Ozone

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 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem