EnviroNearby

Essex County, Massachusetts air quality history

Daily Air Quality Index summaries from EPA monitors in Essex, Massachusetts, 1980–2025.

81%
Good days in 2025
40
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 Essex, Massachusetts on 365 days. 296 of those days (81%) were in the Good range, and the median daily AQI was 40. That median is about the same as the typical monitored county in Massachusetts (median 38 across 13 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 252 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 77% in 1980–1982 versus 77% 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 277 of 347 days1980: Moderate 37 of 347 days1980: Unhealthy for Sensitive Groups 19 of 347 days1980: Unhealthy 10 of 347 days1980: Very Unhealthy 4 of 347 days19801981: Good 223 of 262 days1981: Moderate 21 of 262 days1981: Unhealthy for Sensitive Groups 12 of 262 days1981: Unhealthy 5 of 262 days1981: Very Unhealthy 1 of 262 days1982: Good 156 of 235 days1982: Moderate 57 of 235 days1982: Unhealthy for Sensitive Groups 12 of 235 days1982: Unhealthy 7 of 235 days1982: Very Unhealthy 3 of 235 days1983: Good 195 of 309 days1983: Moderate 78 of 309 days1983: Unhealthy for Sensitive Groups 21 of 309 days1983: Unhealthy 13 of 309 days1983: Very Unhealthy 2 of 309 days1984: Good 241 of 349 days1984: Moderate 74 of 349 days1984: Unhealthy for Sensitive Groups 21 of 349 days1984: Unhealthy 13 of 349 days1985: Good 252 of 350 days1985: Moderate 73 of 350 days1985: Unhealthy for Sensitive Groups 16 of 350 days1985: Unhealthy 7 of 350 days1985: Very Unhealthy 2 of 350 days19851986: Good 233 of 282 days1986: Moderate 32 of 282 days1986: Unhealthy for Sensitive Groups 9 of 282 days1986: Unhealthy 8 of 282 days1987: Good 187 of 227 days1987: Moderate 26 of 227 days1987: Unhealthy for Sensitive Groups 10 of 227 days1987: Unhealthy 2 of 227 days1987: Very Unhealthy 2 of 227 days1988: Good 142 of 214 days1988: Moderate 28 of 214 days1988: Unhealthy for Sensitive Groups 18 of 214 days1988: Unhealthy 12 of 214 days1988: Very Unhealthy 14 of 214 days1989: Good 163 of 214 days1989: Moderate 37 of 214 days1989: Unhealthy for Sensitive Groups 11 of 214 days1989: Unhealthy 2 of 214 days1989: Very Unhealthy 1 of 214 days1990: Good 191 of 224 days1990: Moderate 24 of 224 days1990: Unhealthy for Sensitive Groups 9 of 224 days19901991: Good 173 of 237 days1991: Moderate 35 of 237 days1991: Unhealthy for Sensitive Groups 17 of 237 days1991: Unhealthy 9 of 237 days1991: Very Unhealthy 3 of 237 days1992: Good 196 of 237 days1992: Moderate 24 of 237 days1992: Unhealthy for Sensitive Groups 11 of 237 days1992: Unhealthy 6 of 237 days1993: Good 238 of 288 days1993: Moderate 32 of 288 days1993: Unhealthy for Sensitive Groups 13 of 288 days1993: Unhealthy 4 of 288 days1993: Very Unhealthy 1 of 288 days1994: Good 268 of 365 days1994: Moderate 74 of 365 days1994: Unhealthy for Sensitive Groups 17 of 365 days1994: Unhealthy 6 of 365 days1995: Good 301 of 365 days1995: Moderate 40 of 365 days1995: Unhealthy for Sensitive Groups 17 of 365 days1995: Unhealthy 6 of 365 days1995: Very Unhealthy 1 of 365 days19951996: Good 291 of 366 days1996: Moderate 57 of 366 days1996: Unhealthy for Sensitive Groups 16 of 366 days1996: Unhealthy 2 of 366 days1997: Good 309 of 365 days1997: Moderate 39 of 365 days1997: Unhealthy for Sensitive Groups 10 of 365 days1997: Unhealthy 5 of 365 days1997: Very Unhealthy 2 of 365 days1998: Good 285 of 365 days1998: Moderate 61 of 365 days1998: Unhealthy for Sensitive Groups 11 of 365 days1998: Unhealthy 7 of 365 days1998: Very Unhealthy 1 of 365 days1999: Good 196 of 306 days1999: Moderate 88 of 306 days1999: Unhealthy for Sensitive Groups 15 of 306 days1999: Unhealthy 5 of 306 days1999: Very Unhealthy 2 of 306 days2000: Good 190 of 305 days2000: Moderate 108 of 305 days2000: Unhealthy for Sensitive Groups 6 of 305 days2000: Unhealthy 1 of 305 days20002001: Good 253 of 365 days2001: Moderate 90 of 365 days2001: Unhealthy for Sensitive Groups 9 of 365 days2001: Unhealthy 12 of 365 days2001: Very Unhealthy 1 of 365 days2002: Good 262 of 365 days2002: Moderate 69 of 365 days2002: Unhealthy for Sensitive Groups 20 of 365 days2002: Unhealthy 10 of 365 days2002: Very Unhealthy 4 of 365 days2003: Good 273 of 365 days2003: Moderate 73 of 365 days2003: Unhealthy for Sensitive Groups 15 of 365 days2003: Unhealthy 4 of 365 days2004: Good 239 of 366 days2004: Moderate 117 of 366 days2004: Unhealthy for Sensitive Groups 7 of 366 days2004: Unhealthy 3 of 366 days2005: Good 190 of 365 days2005: Moderate 156 of 365 days2005: Unhealthy for Sensitive Groups 14 of 365 days2005: Unhealthy 5 of 365 days20052006: Good 215 of 365 days2006: Moderate 134 of 365 days2006: Unhealthy for Sensitive Groups 15 of 365 days2006: Unhealthy 1 of 365 days2007: Good 186 of 365 days2007: Moderate 156 of 365 days2007: Unhealthy for Sensitive Groups 17 of 365 days2007: Unhealthy 6 of 365 days2008: Good 189 of 366 days2008: Moderate 164 of 366 days2008: Unhealthy for Sensitive Groups 11 of 366 days2008: Unhealthy 2 of 366 days2009: Good 217 of 365 days2009: Moderate 144 of 365 days2009: Unhealthy for Sensitive Groups 4 of 365 days2010: Good 222 of 365 days2010: Moderate 137 of 365 days2010: Unhealthy for Sensitive Groups 5 of 365 days2010: Unhealthy 1 of 365 days20102011: Good 179 of 365 days2011: Moderate 182 of 365 days2011: Unhealthy for Sensitive Groups 3 of 365 days2011: Unhealthy 1 of 365 days2012: Good 206 of 366 days2012: Moderate 151 of 366 days2012: Unhealthy for Sensitive Groups 8 of 366 days2012: Unhealthy 1 of 366 days2013: Good 216 of 365 days2013: Moderate 141 of 365 days2013: Unhealthy for Sensitive Groups 8 of 365 days2014: Good 244 of 365 days2014: Moderate 120 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 255 of 365 days2015: Moderate 107 of 365 days2015: Unhealthy for Sensitive Groups 3 of 365 days20152016: Good 295 of 366 days2016: Moderate 68 of 366 days2016: Unhealthy for Sensitive Groups 3 of 366 days2017: Good 285 of 365 days2017: Moderate 77 of 365 days2017: Unhealthy for Sensitive Groups 3 of 365 days2018: Good 263 of 365 days2018: Moderate 98 of 365 days2018: Unhealthy for Sensitive Groups 4 of 365 days2019: Good 288 of 364 days2019: Moderate 75 of 364 days2019: Unhealthy for Sensitive Groups 1 of 364 days2020: Good 282 of 366 days2020: Moderate 84 of 366 days20202021: Good 285 of 365 days2021: Moderate 79 of 365 days2021: Unhealthy for Sensitive Groups 1 of 365 days2022: Good 276 of 365 days2022: Moderate 84 of 365 days2022: Unhealthy for Sensitive Groups 5 of 365 days2023: Good 243 of 365 days2023: Moderate 120 of 365 days2023: Unhealthy for Sensitive Groups 2 of 365 days2024: Good 300 of 366 days2024: Moderate 62 of 366 days2024: Unhealthy 2 of 366 days2024: Hazardous 2 of 366 days2025: Good 296 of 365 days2025: Moderate 66 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 971981: 90th percentile AQI 671982: 90th percentile AQI 971983: 90th percentile AQI 1051984: 90th percentile AQI 1001985: 90th percentile AQI 871986: 90th percentile AQI 741987: 90th percentile AQI 901988: 90th percentile AQI 1791989: 90th percentile AQI 841990: 90th percentile AQI 711991: 90th percentile AQI 1291992: 90th percentile AQI 711993: 90th percentile AQI 771994: 90th percentile AQI 841995: 90th percentile AQI 771996: 90th percentile AQI 721997: 90th percentile AQI 641998: 90th percentile AQI 771999: 90th percentile AQI 842000: 90th percentile AQI 722001: 90th percentile AQI 812002: 90th percentile AQI 932003: 90th percentile AQI 722004: 90th percentile AQI 732005: 90th percentile AQI 792006: 90th percentile AQI 802007: 90th percentile AQI 852008: 90th percentile AQI 772009: 90th percentile AQI 662010: 90th percentile AQI 702011: 90th percentile AQI 712012: 90th percentile AQI 712013: 90th percentile AQI 682014: 90th percentile AQI 612015: 90th percentile AQI 612016: 90th percentile AQI 582017: 90th percentile AQI 582018: 90th percentile AQI 592019: 90th percentile AQI 552020: 90th percentile AQI 562021: 90th percentile AQI 562022: 90th percentile AQI 582023: 90th percentile AQI 602024: 90th percentile AQI 582025: 90th percentile AQI 561980: Median AQI 341981: Median AQI 331982: Median AQI 421983: Median AQI 461984: Median AQI 411985: Median AQI 421986: Median AQI 371987: Median AQI 371988: Median AQI 441989: Median AQI 401990: Median AQI 321991: Median AQI 391992: Median AQI 341993: Median AQI 381994: Median AQI 421995: Median AQI 381996: Median AQI 401997: Median AQI 391998: Median AQI 391999: Median AQI 452000: Median AQI 432001: Median AQI 402002: Median AQI 392003: Median AQI 392004: Median AQI 422005: Median AQI 492006: Median AQI 452007: Median AQI 492008: Median AQI 492009: Median AQI 472010: Median AQI 442011: Median AQI 512012: Median AQI 472013: Median AQI 452014: Median AQI 432015: Median AQI 412016: Median AQI 392017: Median AQI 402018: Median AQI 422019: Median AQI 412020: Median AQI 402021: Median AQI 382022: Median AQI 412023: Median AQI 442024: Median AQI 372025: Median AQI 401980198519901995200020052010201520202025
  • 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
Ozone25269%
Fine particles (PM2.5)11331%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253652966630004056136Ozone
202436630062020237581513Ozone
202336524312020004460105PM2.5
20223652768450004158113Ozone
20213652857910003856129Ozone
2020366282840000405697PM2.5
20193642887510004155122Ozone
20183652639840004259115PM2.5
20173652857730004058136Ozone
20163662956830003958105Ozone
201536525510730004161122Ozone
201436524412010004361108PM2.5
201336521614180004568126PM2.5
201236620615181004771164PM2.5
201136517918231005171151PM2.5
201036522213751004470157PM2.5
200936521714440004766129PM2.5
2008366189164112004977169PM2.5
2007365186156176004985195PM2.5
2006365215134151004580159PM2.5
2005365190156145004979185PM2.5
200436623911773004273166Ozone
200336527373154003972187Ozone
2002365262692010403993222Ozone
200136525390912104081213Ozone
200030519010861004372159Ozone
199930619688155204584207Ozone
199836528561117103977203Ozone
199736530939105203964203Ozone
199636629157162004072164Ozone
199536530140176103877212Ozone
199436526874176004284179Ozone
199328823832134103877210Ozone
199223719624116003471187Ozone
1991237173351793039129208Ozone
19902241912490003271140Ozone
198921416337112104084201Ozone
198821414228181214044179241Ozone
198722718726102203790214Ozone
19862822333298003774177Ozone
198535025273167204287212NO2
19843492417421130041100192NO2
19833091957821132046105217NO2
198223515657127304297251Ozone
198126222321125103367201Ozone
1980347277371910403497232Ozone

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 Massachusetts with a similar median AQI in 2025

All monitored counties in Massachusetts

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