EnviroNearby

Middlesex County, New Jersey air quality history

Daily Air Quality Index summaries from EPA monitors in Middlesex, New Jersey, 1980–2025.

81%
Good days in 2025
36
Median daily AQI, 2025
1
Days above 100 in 2025
362
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Middlesex, New Jersey on 362 days. 295 of those days (81%) were in the Good range, and the median daily AQI was 36. That median is lower than the typical monitored county in New Jersey (median 40 across 15 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 229 days. Across the years with fuller monitoring, the share of Good days rose: an average of 55% in 1980–1982 versus 74% 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 170 of 356 days1980: Moderate 136 of 356 days1980: Unhealthy for Sensitive Groups 27 of 356 days1980: Unhealthy 18 of 356 days1980: Very Unhealthy 5 of 356 days19801981: Good 236 of 365 days1981: Moderate 103 of 365 days1981: Unhealthy for Sensitive Groups 16 of 365 days1981: Unhealthy 9 of 365 days1981: Very Unhealthy 1 of 365 days1982: Good 195 of 361 days1982: Moderate 119 of 361 days1982: Unhealthy for Sensitive Groups 27 of 361 days1982: Unhealthy 14 of 361 days1982: Very Unhealthy 6 of 361 days1983: Good 189 of 363 days1983: Moderate 113 of 363 days1983: Unhealthy for Sensitive Groups 29 of 363 days1983: Unhealthy 18 of 363 days1983: Very Unhealthy 14 of 363 days1984: Good 228 of 366 days1984: Moderate 91 of 366 days1984: Unhealthy for Sensitive Groups 26 of 366 days1984: Unhealthy 15 of 366 days1984: Very Unhealthy 6 of 366 days1985: Good 244 of 365 days1985: Moderate 69 of 365 days1985: Unhealthy for Sensitive Groups 23 of 365 days1985: Unhealthy 20 of 365 days1985: Very Unhealthy 9 of 365 days19851986: Good 260 of 365 days1986: Moderate 62 of 365 days1986: Unhealthy for Sensitive Groups 22 of 365 days1986: Unhealthy 18 of 365 days1986: Very Unhealthy 3 of 365 days1987: Good 263 of 345 days1987: Moderate 42 of 345 days1987: Unhealthy for Sensitive Groups 22 of 345 days1987: Unhealthy 10 of 345 days1987: Very Unhealthy 8 of 345 days1988: Good 292 of 365 days1988: Moderate 25 of 365 days1988: Unhealthy for Sensitive Groups 16 of 365 days1988: Unhealthy 18 of 365 days1988: Very Unhealthy 14 of 365 days1989: Good 289 of 363 days1989: Moderate 47 of 363 days1989: Unhealthy for Sensitive Groups 13 of 363 days1989: Unhealthy 9 of 363 days1989: Very Unhealthy 5 of 363 days1990: Good 300 of 362 days1990: Moderate 35 of 362 days1990: Unhealthy for Sensitive Groups 13 of 362 days1990: Unhealthy 9 of 362 days1990: Very Unhealthy 5 of 362 days19901991: Good 274 of 363 days1991: Moderate 44 of 363 days1991: Unhealthy for Sensitive Groups 21 of 363 days1991: Unhealthy 21 of 363 days1991: Very Unhealthy 3 of 363 days1992: Good 309 of 365 days1992: Moderate 34 of 365 days1992: Unhealthy for Sensitive Groups 16 of 365 days1992: Unhealthy 4 of 365 days1992: Very Unhealthy 2 of 365 days1993: Good 280 of 364 days1993: Moderate 40 of 364 days1993: Unhealthy for Sensitive Groups 36 of 364 days1993: Unhealthy 7 of 364 days1993: Very Unhealthy 1 of 364 days1994: Good 271 of 365 days1994: Moderate 54 of 365 days1994: Unhealthy for Sensitive Groups 28 of 365 days1994: Unhealthy 10 of 365 days1994: Very Unhealthy 2 of 365 days1995: Good 272 of 365 days1995: Moderate 54 of 365 days1995: Unhealthy for Sensitive Groups 20 of 365 days1995: Unhealthy 14 of 365 days1995: Very Unhealthy 5 of 365 days19951996: Good 245 of 365 days1996: Moderate 86 of 365 days1996: Unhealthy for Sensitive Groups 25 of 365 days1996: Unhealthy 9 of 365 days1997: Good 285 of 365 days1997: Moderate 44 of 365 days1997: Unhealthy for Sensitive Groups 21 of 365 days1997: Unhealthy 11 of 365 days1997: Very Unhealthy 4 of 365 days1998: Good 260 of 365 days1998: Moderate 61 of 365 days1998: Unhealthy for Sensitive Groups 31 of 365 days1998: Unhealthy 13 of 365 days1999: Good 235 of 365 days1999: Moderate 89 of 365 days1999: Unhealthy for Sensitive Groups 19 of 365 days1999: Unhealthy 16 of 365 days1999: Very Unhealthy 6 of 365 days2000: Good 235 of 366 days2000: Moderate 104 of 366 days2000: Unhealthy for Sensitive Groups 18 of 366 days2000: Unhealthy 8 of 366 days2000: Very Unhealthy 1 of 366 days20002001: Good 210 of 365 days2001: Moderate 116 of 365 days2001: Unhealthy for Sensitive Groups 25 of 365 days2001: Unhealthy 10 of 365 days2001: Very Unhealthy 4 of 365 days2002: Good 221 of 365 days2002: Moderate 87 of 365 days2002: Unhealthy for Sensitive Groups 31 of 365 days2002: Unhealthy 24 of 365 days2002: Very Unhealthy 2 of 365 days2003: Good 238 of 365 days2003: Moderate 100 of 365 days2003: Unhealthy for Sensitive Groups 22 of 365 days2003: Unhealthy 3 of 365 days2003: Very Unhealthy 2 of 365 days2004: Good 242 of 366 days2004: Moderate 111 of 366 days2004: Unhealthy for Sensitive Groups 11 of 366 days2004: Unhealthy 2 of 366 days2005: Good 233 of 365 days2005: Moderate 103 of 365 days2005: Unhealthy for Sensitive Groups 19 of 365 days2005: Unhealthy 10 of 365 days20052006: Good 182 of 364 days2006: Moderate 159 of 364 days2006: Unhealthy for Sensitive Groups 18 of 364 days2006: Unhealthy 4 of 364 days2006: Very Unhealthy 1 of 364 days2007: Good 191 of 365 days2007: Moderate 146 of 365 days2007: Unhealthy for Sensitive Groups 23 of 365 days2007: Unhealthy 5 of 365 days2008: Good 190 of 366 days2008: Moderate 156 of 366 days2008: Unhealthy for Sensitive Groups 17 of 366 days2008: Unhealthy 3 of 366 days2009: Good 240 of 365 days2009: Moderate 124 of 365 days2009: Unhealthy for Sensitive Groups 1 of 365 days2010: Good 233 of 365 days2010: Moderate 105 of 365 days2010: Unhealthy for Sensitive Groups 22 of 365 days2010: Unhealthy 5 of 365 days20102011: Good 223 of 362 days2011: Moderate 123 of 362 days2011: Unhealthy for Sensitive Groups 12 of 362 days2011: Unhealthy 4 of 362 days2012: Good 245 of 360 days2012: Moderate 95 of 360 days2012: Unhealthy for Sensitive Groups 20 of 360 days2013: Good 281 of 365 days2013: Moderate 83 of 365 days2013: Unhealthy for Sensitive Groups 1 of 365 days2014: Good 279 of 362 days2014: Moderate 79 of 362 days2014: Unhealthy for Sensitive Groups 3 of 362 days2014: Unhealthy 1 of 362 days2015: Good 246 of 319 days2015: Moderate 64 of 319 days2015: Unhealthy for Sensitive Groups 9 of 319 days20152016: Good 225 of 366 days2016: Moderate 129 of 366 days2016: Unhealthy for Sensitive Groups 11 of 366 days2016: Unhealthy 1 of 366 days2017: Good 245 of 365 days2017: Moderate 114 of 365 days2017: Unhealthy for Sensitive Groups 6 of 365 days2018: Good 239 of 365 days2018: Moderate 120 of 365 days2018: Unhealthy for Sensitive Groups 6 of 365 days2019: Good 243 of 362 days2019: Moderate 116 of 362 days2019: Unhealthy for Sensitive Groups 3 of 362 days2020: Good 257 of 366 days2020: Moderate 108 of 366 days2020: Unhealthy for Sensitive Groups 1 of 366 days20202021: Good 233 of 364 days2021: Moderate 126 of 364 days2021: Unhealthy for Sensitive Groups 5 of 364 days2022: Good 261 of 365 days2022: Moderate 103 of 365 days2022: Unhealthy for Sensitive Groups 1 of 365 days2023: Good 229 of 365 days2023: Moderate 124 of 365 days2023: Unhealthy for Sensitive Groups 7 of 365 days2023: Unhealthy 4 of 365 days2023: Very Unhealthy 1 of 365 days2024: Good 286 of 365 days2024: Moderate 74 of 365 days2024: Unhealthy for Sensitive Groups 5 of 365 days2025: Good 295 of 362 days2025: Moderate 66 of 362 days2025: Unhealthy for Sensitive Groups 1 of 362 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 year0501001501980: 90th percentile AQI 1261981: 90th percentile AQI 821982: 90th percentile AQI 1081983: 90th percentile AQI 1401984: 90th percentile AQI 1151985: 90th percentile AQI 1331986: 90th percentile AQI 1191987: 90th percentile AQI 1151988: 90th percentile AQI 1191989: 90th percentile AQI 871990: 90th percentile AQI 711991: 90th percentile AQI 1121992: 90th percentile AQI 671993: 90th percentile AQI 1121994: 90th percentile AQI 1151995: 90th percentile AQI 1051996: 90th percentile AQI 931997: 90th percentile AQI 1001998: 90th percentile AQI 1081999: 90th percentile AQI 1072000: 90th percentile AQI 842001: 90th percentile AQI 1052002: 90th percentile AQI 1332003: 90th percentile AQI 902004: 90th percentile AQI 802005: 90th percentile AQI 902006: 90th percentile AQI 872007: 90th percentile AQI 932008: 90th percentile AQI 842009: 90th percentile AQI 642010: 90th percentile AQI 842011: 90th percentile AQI 742012: 90th percentile AQI 802013: 90th percentile AQI 642014: 90th percentile AQI 642015: 90th percentile AQI 672016: 90th percentile AQI 712017: 90th percentile AQI 642018: 90th percentile AQI 652019: 90th percentile AQI 632020: 90th percentile AQI 582021: 90th percentile AQI 642022: 90th percentile AQI 592023: 90th percentile AQI 672024: 90th percentile AQI 582025: 90th percentile AQI 571980: Median AQI 521981: Median AQI 431982: Median AQI 491983: Median AQI 491984: Median AQI 441985: Median AQI 421986: Median AQI 391987: Median AQI 351988: Median AQI 331989: Median AQI 321990: Median AQI 321991: Median AQI 331992: Median AQI 301993: Median AQI 311994: Median AQI 391995: Median AQI 411996: Median AQI 421997: Median AQI 401998: Median AQI 411999: Median AQI 442000: Median AQI 432001: Median AQI 452002: Median AQI 442003: Median AQI 422004: Median AQI 432005: Median AQI 442006: Median AQI 512007: Median AQI 482008: Median AQI 492009: Median AQI 422010: Median AQI 432011: Median AQI 452012: Median AQI 432013: Median AQI 402014: Median AQI 402015: Median AQI 372016: Median AQI 452017: Median AQI 442018: Median AQI 422019: Median AQI 432020: Median AQI 412021: Median AQI 442022: Median AQI 422023: Median AQI 442024: Median AQI 362025: Median AQI 361980198519901995200020052010201520202025
  • 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
Ozone22963%
Fine particles (PM2.5)11632%
Nitrogen dioxide (NO₂)175%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253622956610003657112Ozone
20243652867450003658136Ozone
202336522912474104467247PM2.5
202236526110310004259101PM2.5
202136423312650004464129PM2.5
202036625710810004158112PM2.5
201936224311630004363115Ozone
201836523912060004265133PM2.5
201736524511460004464133PM2.5
2016366225129111004571151PM2.5
20153192466490003767136Ozone
20143622797931004064174Ozone
20133652818310004064112Ozone
201236024595200004380143Ozone
2011362223123124004574166PM2.5
2010365233105225004384172Ozone
200936524012410004264105PM2.5
2008366190156173004984172PM2.5
2007365191146235004893192PM2.5
2006364182159184105187201PM2.5
20053652331031910004490179Ozone
2004366242111112004380185Ozone
2003365238100223204290213Ozone
20023652218731242044133210Ozone
200136521011625104045105216Ozone
2000366235104188104384207Ozone
19993652358919166044107232Ozone
19983652606131130041108195Ozone
19973652854421114040100213Ozone
199636524586259004293200NO2
19953652725420145041105220Ozone
19943652715428102039115206Ozone
1993364280403671031112201Ozone
199236530934164203067218Ozone
19913632744421213033112207Ozone
199036230035139503271212Ozone
198936328947139503287204Ozone
198836529225161814033119266Ozone
19873452634222108035115224Ozone
19863652606222183039119223Ozone
19853652446923209042133248Ozone
19843662289126156044115244CO
1983363189113291814049140256Ozone
198236119511927146049108223Ozone
1981365236103169104382209CO
198035617013627185052126260CO

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 New Jersey with a similar median AQI in 2025

All monitored counties in New Jersey

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