EnviroNearby

Carroll County, Maryland air quality history

Daily Air Quality Index summaries from EPA monitors in Carroll, Maryland, 1983–2025.

90%
Good days in 2025
38
Median daily AQI, 2025
0
Days above 100 in 2025
238
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Carroll, Maryland on 238 days. 215 of those days (90%) were in the Good range, and the median daily AQI was 38. That median is about the same as the typical monitored county in Maryland (median 39.5 across 16 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 238 days. Across the years with fuller monitoring, the share of Good days rose: an average of 69% in 1983–1985 versus 81% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (238 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.

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%1983: Good 84 of 135 days1983: Moderate 17 of 135 days1983: Unhealthy for Sensitive Groups 13 of 135 days1983: Unhealthy 17 of 135 days1983: Very Unhealthy 4 of 135 days19831984: Good 254 of 327 days1984: Moderate 43 of 327 days1984: Unhealthy for Sensitive Groups 23 of 327 days1984: Unhealthy 6 of 327 days1984: Very Unhealthy 1 of 327 days1985: Good 234 of 350 days1985: Moderate 58 of 350 days1985: Unhealthy for Sensitive Groups 40 of 350 days1985: Unhealthy 16 of 350 days1985: Very Unhealthy 2 of 350 days1986: Good 258 of 351 days1986: Moderate 58 of 351 days1986: Unhealthy for Sensitive Groups 26 of 351 days1986: Unhealthy 8 of 351 days1986: Very Unhealthy 1 of 351 days1987: Good 213 of 325 days1987: Moderate 48 of 325 days1987: Unhealthy for Sensitive Groups 39 of 325 days1987: Unhealthy 21 of 325 days1987: Very Unhealthy 4 of 325 days1988: Good 221 of 321 days1988: Moderate 37 of 321 days1988: Unhealthy for Sensitive Groups 22 of 321 days1988: Unhealthy 23 of 321 days1988: Very Unhealthy 18 of 321 days19881989: Good 160 of 249 days1989: Moderate 56 of 249 days1989: Unhealthy for Sensitive Groups 24 of 249 days1989: Unhealthy 9 of 249 days1990: Good 124 of 211 days1990: Moderate 52 of 211 days1990: Unhealthy for Sensitive Groups 22 of 211 days1990: Unhealthy 11 of 211 days1990: Very Unhealthy 2 of 211 days1991: Good 84 of 215 days1991: Moderate 60 of 215 days1991: Unhealthy for Sensitive Groups 45 of 215 days1991: Unhealthy 23 of 215 days1991: Very Unhealthy 3 of 215 days1992: Good 134 of 209 days1992: Moderate 48 of 209 days1992: Unhealthy for Sensitive Groups 21 of 209 days1992: Unhealthy 6 of 209 days1993: Good 109 of 213 days1993: Moderate 55 of 213 days1993: Unhealthy for Sensitive Groups 35 of 213 days1993: Unhealthy 13 of 213 days1993: Very Unhealthy 1 of 213 days19931994: Good 113 of 208 days1994: Moderate 48 of 208 days1994: Unhealthy for Sensitive Groups 37 of 208 days1994: Unhealthy 8 of 208 days1994: Very Unhealthy 2 of 208 days1995: Good 122 of 214 days1995: Moderate 49 of 214 days1995: Unhealthy for Sensitive Groups 26 of 214 days1995: Unhealthy 15 of 214 days1995: Very Unhealthy 2 of 214 days1996: Good 121 of 213 days1996: Moderate 58 of 213 days1996: Unhealthy for Sensitive Groups 25 of 213 days1996: Unhealthy 9 of 213 days1997: Good 127 of 203 days1997: Moderate 41 of 203 days1997: Unhealthy for Sensitive Groups 27 of 203 days1997: Unhealthy 8 of 203 days1998: Good 104 of 208 days1998: Moderate 56 of 208 days1998: Unhealthy for Sensitive Groups 30 of 208 days1998: Unhealthy 17 of 208 days1998: Very Unhealthy 1 of 208 days19981999: Good 111 of 213 days1999: Moderate 59 of 213 days1999: Unhealthy for Sensitive Groups 29 of 213 days1999: Unhealthy 13 of 213 days1999: Very Unhealthy 1 of 213 days2000: Good 135 of 214 days2000: Moderate 55 of 214 days2000: Unhealthy for Sensitive Groups 19 of 214 days2000: Unhealthy 5 of 214 days2001: Good 121 of 212 days2001: Moderate 53 of 212 days2001: Unhealthy for Sensitive Groups 30 of 212 days2001: Unhealthy 8 of 212 days2002: Good 123 of 213 days2002: Moderate 58 of 213 days2002: Unhealthy for Sensitive Groups 23 of 213 days2002: Unhealthy 9 of 213 days2003: Good 156 of 213 days2003: Moderate 48 of 213 days2003: Unhealthy for Sensitive Groups 7 of 213 days2003: Unhealthy 2 of 213 days20032004: Good 148 of 205 days2004: Moderate 45 of 205 days2004: Unhealthy for Sensitive Groups 11 of 205 days2004: Unhealthy 1 of 205 days2005: Good 129 of 212 days2005: Moderate 58 of 212 days2005: Unhealthy for Sensitive Groups 21 of 212 days2005: Unhealthy 4 of 212 days2006: Good 143 of 211 days2006: Moderate 53 of 211 days2006: Unhealthy for Sensitive Groups 14 of 211 days2006: Unhealthy 1 of 211 days2007: Good 119 of 213 days2007: Moderate 58 of 213 days2007: Unhealthy for Sensitive Groups 29 of 213 days2007: Unhealthy 7 of 213 days2008: Good 149 of 210 days2008: Moderate 46 of 210 days2008: Unhealthy for Sensitive Groups 14 of 210 days2008: Unhealthy 1 of 210 days20082009: Good 183 of 212 days2009: Moderate 28 of 212 days2009: Unhealthy for Sensitive Groups 1 of 212 days2010: Good 128 of 212 days2010: Moderate 63 of 212 days2010: Unhealthy for Sensitive Groups 21 of 212 days2011: Good 148 of 211 days2011: Moderate 54 of 211 days2011: Unhealthy for Sensitive Groups 9 of 211 days2012: Good 141 of 213 days2012: Moderate 61 of 213 days2012: Unhealthy for Sensitive Groups 10 of 213 days2012: Unhealthy 1 of 213 days2013: Good 162 of 209 days2013: Moderate 46 of 209 days2013: Unhealthy for Sensitive Groups 1 of 209 days20132014: Good 163 of 214 days2014: Moderate 51 of 214 days2015: Good 162 of 213 days2015: Moderate 49 of 213 days2015: Unhealthy for Sensitive Groups 2 of 213 days2016: Good 167 of 212 days2016: Moderate 41 of 212 days2016: Unhealthy for Sensitive Groups 4 of 212 days2017: Good 201 of 245 days2017: Moderate 43 of 245 days2017: Unhealthy for Sensitive Groups 1 of 245 days2018: Good 199 of 240 days2018: Moderate 41 of 240 days20182019: Good 205 of 241 days2019: Moderate 35 of 241 days2019: Unhealthy for Sensitive Groups 1 of 241 days2020: Good 225 of 242 days2020: Moderate 17 of 242 days2021: Good 208 of 243 days2021: Moderate 34 of 243 days2021: Unhealthy for Sensitive Groups 1 of 243 days2022: Good 210 of 243 days2022: Moderate 32 of 243 days2022: Unhealthy for Sensitive Groups 1 of 243 days2023: Good 183 of 244 days2023: Moderate 57 of 244 days2023: Unhealthy for Sensitive Groups 4 of 244 days20232024: Good 189 of 244 days2024: Moderate 55 of 244 days2025: Good 215 of 238 days2025: Moderate 23 of 238 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 year0501001502001983: 90th percentile AQI 1771984: 90th percentile AQI 971985: 90th percentile AQI 1261986: 90th percentile AQI 1001987: 90th percentile AQI 1331988: 90th percentile AQI 1721989: 90th percentile AQI 1121990: 90th percentile AQI 1151991: 90th percentile AQI 1561992: 90th percentile AQI 1121993: 90th percentile AQI 1361994: 90th percentile AQI 1331995: 90th percentile AQI 1431996: 90th percentile AQI 1221997: 90th percentile AQI 1291998: 90th percentile AQI 1431999: 90th percentile AQI 1362000: 90th percentile AQI 1052001: 90th percentile AQI 1262002: 90th percentile AQI 1262003: 90th percentile AQI 842004: 90th percentile AQI 842005: 90th percentile AQI 1012006: 90th percentile AQI 932007: 90th percentile AQI 1192008: 90th percentile AQI 902009: 90th percentile AQI 582010: 90th percentile AQI 1002011: 90th percentile AQI 802012: 90th percentile AQI 902013: 90th percentile AQI 642014: 90th percentile AQI 712015: 90th percentile AQI 672016: 90th percentile AQI 672017: 90th percentile AQI 642018: 90th percentile AQI 612019: 90th percentile AQI 542020: 90th percentile AQI 492021: 90th percentile AQI 542022: 90th percentile AQI 542023: 90th percentile AQI 742024: 90th percentile AQI 672025: 90th percentile AQI 501983: Median AQI 341984: Median AQI 331985: Median AQI 401986: Median AQI 341987: Median AQI 401988: Median AQI 361989: Median AQI 421990: Median AQI 461991: Median AQI 741992: Median AQI 441993: Median AQI 501994: Median AQI 481995: Median AQI 481996: Median AQI 461997: Median AQI 441998: Median AQI 511999: Median AQI 492000: Median AQI 432001: Median AQI 472002: Median AQI 472003: Median AQI 422004: Median AQI 442005: Median AQI 472006: Median AQI 442007: Median AQI 472008: Median AQI 432009: Median AQI 392010: Median AQI 462011: Median AQI 442012: Median AQI 452013: Median AQI 432014: Median AQI 432015: Median AQI 432016: Median AQI 422017: Median AQI 412018: Median AQI 412019: Median AQI 432020: Median AQI 392021: Median AQI 412022: Median AQI 422023: Median AQI 442024: Median AQI 422025: Median AQI 381983198819931998200320082013201820232025
  • 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
Ozone238100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025238215230000385090Ozone
2024244189550000426793Ozone
20232441835740004474143Ozone
20222432103210004254112Ozone
20212432083410004154112Ozone
2020242225170000394984Ozone
20192412053510004354101Ozone
2018240199410000416197Ozone
20172452014310004164108Ozone
20162121674140004267122Ozone
20152131624920004367115Ozone
2014214163510000437184Ozone
20132091624610004364101Ozone
201221314161101004590159Ozone
20112111485490004480150Ozone
2010212128632100046100150Ozone
20092121832810003958112Ozone
200821014946141004390177Ozone
2007213119582970047119174Ozone
200621114353141004493197Ozone
2005212129582140047101164Ozone
200420514845111004484179Ozone
20032131564872004284182Ozone
2002213123582390047126192Ozone
2001212121533080047126200Ozone
2000214135551950043105187Ozone
19992131115929131049136213Ozone
19982081045630171051143206Ozone
1997203127412780044129195Ozone
1996213121582590046122187Ozone
19952141224926152048143203Ozone
1994208113483782048133209Ozone
19932131095535131050136204Ozone
1992209134482160044112185Ozone
1991215846045233074156202Ozone
19902111245222112046115206Ozone
1989249160562490042112185Ozone
198832122137222318036172230Ozone
19873252134839214040133216Ozone
1986351258582681034100205Ozone
19853502345840162040126215Ozone
198432725443236103397224Ozone
1983135841713174034177212Ozone

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 Maryland with a similar median AQI in 2025

All monitored counties in Maryland

Source: U.S. EPA AirData, “Annual AQI by County” files for 1983–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem