EnviroNearby

Baltimore County, Maryland air quality history

Daily Air Quality Index summaries from EPA monitors in Baltimore, Maryland, 1980–2025.

65%
Good days in 2025
45
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 Baltimore, Maryland on 365 days. 236 of those days (65%) were in the Good range, and the median daily AQI was 45. That median is higher than the typical monitored county in Maryland (median 39.5 across 16 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 192 days. Across the years with fuller monitoring, the share of Good days rose: an average of 56% in 1980–1982 versus 64% in 2023–2025.

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 205 of 354 days1980: Moderate 64 of 354 days1980: Unhealthy for Sensitive Groups 39 of 354 days1980: Unhealthy 24 of 354 days1980: Very Unhealthy 22 of 354 days19801981: Good 213 of 362 days1981: Moderate 89 of 362 days1981: Unhealthy for Sensitive Groups 31 of 362 days1981: Unhealthy 21 of 362 days1981: Very Unhealthy 8 of 362 days1982: Good 182 of 363 days1982: Moderate 103 of 363 days1982: Unhealthy for Sensitive Groups 49 of 363 days1982: Unhealthy 22 of 363 days1982: Very Unhealthy 7 of 363 days1983: Good 180 of 350 days1983: Moderate 91 of 350 days1983: Unhealthy for Sensitive Groups 38 of 350 days1983: Unhealthy 21 of 350 days1983: Very Unhealthy 20 of 350 days1984: Good 236 of 365 days1984: Moderate 84 of 365 days1984: Unhealthy for Sensitive Groups 26 of 365 days1984: Unhealthy 13 of 365 days1984: Very Unhealthy 6 of 365 days1985: Good 187 of 365 days1985: Moderate 115 of 365 days1985: Unhealthy for Sensitive Groups 37 of 365 days1985: Unhealthy 21 of 365 days1985: Very Unhealthy 5 of 365 days19851986: Good 205 of 365 days1986: Moderate 105 of 365 days1986: Unhealthy for Sensitive Groups 31 of 365 days1986: Unhealthy 21 of 365 days1986: Very Unhealthy 3 of 365 days1987: Good 180 of 365 days1987: Moderate 121 of 365 days1987: Unhealthy for Sensitive Groups 30 of 365 days1987: Unhealthy 24 of 365 days1987: Very Unhealthy 10 of 365 days1988: Good 207 of 366 days1988: Moderate 88 of 366 days1988: Unhealthy for Sensitive Groups 23 of 366 days1988: Unhealthy 22 of 366 days1988: Very Unhealthy 26 of 366 days1989: Good 235 of 365 days1989: Moderate 97 of 365 days1989: Unhealthy for Sensitive Groups 25 of 365 days1989: Unhealthy 7 of 365 days1989: Very Unhealthy 1 of 365 days1990: Good 232 of 364 days1990: Moderate 87 of 364 days1990: Unhealthy for Sensitive Groups 31 of 364 days1990: Unhealthy 12 of 364 days1990: Very Unhealthy 2 of 364 days19901991: Good 216 of 358 days1991: Moderate 75 of 358 days1991: Unhealthy for Sensitive Groups 38 of 358 days1991: Unhealthy 23 of 358 days1991: Very Unhealthy 6 of 358 days1992: Good 260 of 366 days1992: Moderate 78 of 366 days1992: Unhealthy for Sensitive Groups 17 of 366 days1992: Unhealthy 11 of 366 days1993: Good 237 of 365 days1993: Moderate 75 of 365 days1993: Unhealthy for Sensitive Groups 35 of 365 days1993: Unhealthy 13 of 365 days1993: Very Unhealthy 5 of 365 days1994: Good 231 of 365 days1994: Moderate 96 of 365 days1994: Unhealthy for Sensitive Groups 25 of 365 days1994: Unhealthy 11 of 365 days1994: Very Unhealthy 2 of 365 days1995: Good 267 of 365 days1995: Moderate 60 of 365 days1995: Unhealthy for Sensitive Groups 20 of 365 days1995: Unhealthy 13 of 365 days1995: Very Unhealthy 5 of 365 days19951996: Good 287 of 366 days1996: Moderate 53 of 366 days1996: Unhealthy for Sensitive Groups 21 of 366 days1996: Unhealthy 5 of 366 days1997: Good 252 of 331 days1997: Moderate 43 of 331 days1997: Unhealthy for Sensitive Groups 21 of 331 days1997: Unhealthy 12 of 331 days1997: Very Unhealthy 3 of 331 days1998: Good 245 of 346 days1998: Moderate 50 of 346 days1998: Unhealthy for Sensitive Groups 38 of 346 days1998: Unhealthy 13 of 346 days1999: Good 231 of 363 days1999: Moderate 90 of 363 days1999: Unhealthy for Sensitive Groups 24 of 363 days1999: Unhealthy 12 of 363 days1999: Very Unhealthy 6 of 363 days2000: Good 146 of 366 days2000: Moderate 197 of 366 days2000: Unhealthy for Sensitive Groups 20 of 366 days2000: Unhealthy 2 of 366 days2000: Very Unhealthy 1 of 366 days20002001: Good 98 of 365 days2001: Moderate 226 of 365 days2001: Unhealthy for Sensitive Groups 25 of 365 days2001: Unhealthy 14 of 365 days2001: Very Unhealthy 2 of 365 days2002: Good 87 of 365 days2002: Moderate 229 of 365 days2002: Unhealthy for Sensitive Groups 26 of 365 days2002: Unhealthy 19 of 365 days2002: Very Unhealthy 4 of 365 days2003: Good 103 of 365 days2003: Moderate 240 of 365 days2003: Unhealthy for Sensitive Groups 19 of 365 days2003: Unhealthy 2 of 365 days2003: Very Unhealthy 1 of 365 days2004: Good 102 of 366 days2004: Moderate 242 of 366 days2004: Unhealthy for Sensitive Groups 20 of 366 days2004: Unhealthy 2 of 366 days2005: Good 99 of 365 days2005: Moderate 233 of 365 days2005: Unhealthy for Sensitive Groups 26 of 365 days2005: Unhealthy 6 of 365 days2005: Very Unhealthy 1 of 365 days20052006: Good 112 of 365 days2006: Moderate 220 of 365 days2006: Unhealthy for Sensitive Groups 25 of 365 days2006: Unhealthy 7 of 365 days2006: Very Unhealthy 1 of 365 days2007: Good 120 of 365 days2007: Moderate 218 of 365 days2007: Unhealthy for Sensitive Groups 25 of 365 days2007: Unhealthy 2 of 365 days2008: Good 121 of 366 days2008: Moderate 223 of 366 days2008: Unhealthy for Sensitive Groups 17 of 366 days2008: Unhealthy 5 of 366 days2009: Good 156 of 365 days2009: Moderate 200 of 365 days2009: Unhealthy for Sensitive Groups 8 of 365 days2009: Unhealthy 1 of 365 days2010: Good 217 of 362 days2010: Moderate 111 of 362 days2010: Unhealthy for Sensitive Groups 30 of 362 days2010: Unhealthy 3 of 362 days2010: Very Unhealthy 1 of 362 days20102011: Good 227 of 363 days2011: Moderate 110 of 363 days2011: Unhealthy for Sensitive Groups 20 of 363 days2011: Unhealthy 6 of 363 days2012: Good 228 of 366 days2012: Moderate 113 of 366 days2012: Unhealthy for Sensitive Groups 23 of 366 days2012: Unhealthy 1 of 366 days2012: Very Unhealthy 1 of 366 days2013: Good 256 of 365 days2013: Moderate 105 of 365 days2013: Unhealthy for Sensitive Groups 4 of 365 days2014: Good 257 of 365 days2014: Moderate 105 of 365 days2014: Unhealthy for Sensitive Groups 3 of 365 days2015: Good 242 of 365 days2015: Moderate 110 of 365 days2015: Unhealthy for Sensitive Groups 13 of 365 days20152016: Good 200 of 366 days2016: Moderate 144 of 366 days2016: Unhealthy for Sensitive Groups 17 of 366 days2016: Unhealthy 4 of 366 days2016: Very Unhealthy 1 of 366 days2017: Good 262 of 365 days2017: Moderate 91 of 365 days2017: Unhealthy for Sensitive Groups 11 of 365 days2017: Unhealthy 1 of 365 days2018: Good 218 of 365 days2018: Moderate 142 of 365 days2018: Unhealthy for Sensitive Groups 5 of 365 days2019: Good 232 of 365 days2019: Moderate 124 of 365 days2019: Unhealthy for Sensitive Groups 9 of 365 days2020: Good 257 of 365 days2020: Moderate 106 of 365 days2020: Unhealthy for Sensitive Groups 2 of 365 days20202021: Good 207 of 365 days2021: Moderate 148 of 365 days2021: Unhealthy for Sensitive Groups 10 of 365 days2022: Good 238 of 365 days2022: Moderate 126 of 365 days2022: Unhealthy for Sensitive Groups 1 of 365 days2023: Good 228 of 365 days2023: Moderate 124 of 365 days2023: Unhealthy for Sensitive Groups 9 of 365 days2023: Unhealthy 3 of 365 days2023: Very Unhealthy 1 of 365 days2024: Good 240 of 366 days2024: Moderate 121 of 366 days2024: Unhealthy for Sensitive Groups 5 of 366 days2025: Good 236 of 365 days2025: Moderate 126 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 year0501001502001980: 90th percentile AQI 1691981: 90th percentile AQI 1361982: 90th percentile AQI 1401983: 90th percentile AQI 1741984: 90th percentile AQI 1151985: 90th percentile AQI 1291986: 90th percentile AQI 1331987: 90th percentile AQI 1501988: 90th percentile AQI 1771989: 90th percentile AQI 931990: 90th percentile AQI 1081991: 90th percentile AQI 1431992: 90th percentile AQI 931993: 90th percentile AQI 1221994: 90th percentile AQI 1011995: 90th percentile AQI 1051996: 90th percentile AQI 901997: 90th percentile AQI 1011998: 90th percentile AQI 1221999: 90th percentile AQI 1122000: 90th percentile AQI 882001: 90th percentile AQI 1082002: 90th percentile AQI 1262003: 90th percentile AQI 902004: 90th percentile AQI 932005: 90th percentile AQI 992006: 90th percentile AQI 972007: 90th percentile AQI 932008: 90th percentile AQI 872009: 90th percentile AQI 752010: 90th percentile AQI 972011: 90th percentile AQI 842012: 90th percentile AQI 892013: 90th percentile AQI 672014: 90th percentile AQI 692015: 90th percentile AQI 772016: 90th percentile AQI 872017: 90th percentile AQI 692018: 90th percentile AQI 692019: 90th percentile AQI 712020: 90th percentile AQI 592021: 90th percentile AQI 712022: 90th percentile AQI 642023: 90th percentile AQI 712024: 90th percentile AQI 712025: 90th percentile AQI 651980: Median AQI 441981: Median AQI 471982: Median AQI 501983: Median AQI 501984: Median AQI 441985: Median AQI 501986: Median AQI 481987: Median AQI 511988: Median AQI 471989: Median AQI 441990: Median AQI 451991: Median AQI 461992: Median AQI 421993: Median AQI 431994: Median AQI 451995: Median AQI 391996: Median AQI 341997: Median AQI 361998: Median AQI 421999: Median AQI 442000: Median AQI 552001: Median AQI 612002: Median AQI 612003: Median AQI 582004: Median AQI 592005: Median AQI 612006: Median AQI 602007: Median AQI 582008: Median AQI 562009: Median AQI 542010: Median AQI 462011: Median AQI 432012: Median AQI 442013: Median AQI 412014: Median AQI 422015: Median AQI 432016: Median AQI 482017: Median AQI 432018: Median AQI 462019: Median AQI 462020: Median AQI 432021: Median AQI 472022: Median AQI 452023: Median AQI 452024: Median AQI 452025: Median AQI 451980198519901995200020052010201520202025
  • 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
Ozone19253%
Fine particles (PM2.5)17347%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536523612630004565129Ozone
202436624012150004571115Ozone
202336522812493104571205Ozone
202236523812610004564122Ozone
2021365207148100004771140Ozone
202036525710620004359105Ozone
201936523212490004671150Ozone
201836521814250004669115PM2.5
201736526291111004369166Ozone
2016366200144174104887204Ozone
2015365242110130004377143Ozone
201436525710530004269136Ozone
201336525610540004167119Ozone
2012366228113231104489204Ozone
2011363227110206004384190Ozone
2010362217111303104697210Ozone
200936515620081005475151PM2.5
2008366121223175005687185PM2.5
2007365120218252005893172PM2.5
2006365112220257106097205PM2.5
200536599233266106199208PM2.5
2004366102242202005993195PM2.5
2003365103240192105890204PM2.5
20023658722926194061126216PM2.5
20013659822625142061108218PM2.5
2000366146197202105588204PM2.5
19993632319024126044112213Ozone
19983462455038130042122197Ozone
19973312524321123036101223Ozone
199636628753215003490182Ozone
19953652676020135039105222Ozone
19943652319625112045101201NO2
19933652377535135043122214NO2
1992366260781711004293190NO2
19913582167538236046143227Ozone
19903642328731122045108215NO2
198936523597257104493215NO2
198836620788232226047177261Ozone
1987365180121302410051150217NO2
198636520510531213048133213NO2
198536518711537215050129226NO2
19843652368426136044115225Ozone
198335018091382120050174226NO2
198236318210349227050140212NO2
19813622138931218047136225NO2
198035420564392422044169237Ozone

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 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