State air quality · 2025

New Jersey Air Quality Ranking

Across 15 monitored counties, the typical county in New Jersey posts a median AQI of 40 (Good) and 75.5% of monitored days were rated Good, from EPA AQS.

40
Avg median AQI
75.5%
Good-air days
15
Counties monitored
42%
Cleaner than US states

New Jersey's typical county median AQI is 40 (Good) across 15 monitored counties

According to the U.S. EPA Air Quality System, New Jersey monitors 15 counties with a day-weighted Good-day share of 75.5%. Cleanest: Monmouth County (91.3% Good). Most polluted: Union County (61.2%). These are annual summaries, not live AirNow readings.

Data source EPA Air Quality System (AQS)

Cleaner than US states
New Jersey's day-weighted Good-day share of 75.5% places it cleaner than 42% of US states.
In-state spread
Within New Jersey, Monmouth County leads at 91.3% Good days while Union County sits at 61.2% across 15 monitored counties.
2024→2025 release
New Jersey's Good-day share moved +0.5 points vs the 2024 EPA annual release.
Typical median AQI
Typical median AQI: 40

Verify with AirNow → · EPA AQS →

EPA state monitoring brief

AQS state key NEW-JERSEY

New Jersey · 2025 EPA AQS · 15 counties · med AQI 40 · 75.5% Good · Monmouth→Union spread

  • GOOD 40 Median AQI · Good
  • SHARE 75.5% Good-day share
  • COUNT 15 Counties monitored
  • UNH 4 Unhealthy+ days
  • RANK 42% Cleaner than states
  • O3 54.3% Main pollutant share

Good-day share peers

Missouri75.9%New Jersey (this)75.5%Kansas74.7%Michigan74.7%
Good-day share neighbourhood · nearest ABS peers vs New Jersey

New Jersey's 75.5% Good-day share is cleaner than 42% of monitored US states; Monmouth and Union County bracket the in-state range. Open Monmouth County →

According to EPA AQS annual summaries on PlainAirData, New Jersey ranks #30 of 52 by day-weighted good-day share (75.5%) and #30 by mean county median AQI (39.7). Hawaii is #1 of 52 by day-weighted good-day share (93.8% of monitored days) at mean county median-AQI #4 (27.3) ≠ Alaska #1 lowest mean county median AQI (20.3) at good-day share #8 (84.4%).

Data updated August 2026

What changed, what drives it, and how thick is the sample

Three derived views WPR-style word count does not substitute for: release-over-release movement from county annual rows, the EPA main-pollutant day mix, and how many counties sit below the 100-day ranking floor.

Release change

75.5%

Good-day share in 2025, up 0.5 percentage points vs 2024. County-mean median AQI 40, within half a point of the 2024 county-mean median.

Pollutant mix

Ozone

Main driver on 54.3% of pollutant-assigned days.

  • Ozone 54.3%
  • PM2.5 40.0%
  • NO2 5.6%
  • PM10 0.1%

Monitoring coverage

354

Average monitored days per county in the latest release. Every monitored county clears the 100-day ranking floor.

Counties Monitored

15

Good Days %

75.5%

Avg Median AQI

40

Total Unhealthy Days

4

Best Air Quality

Monmouth County

Worst Air Quality

Union County

Where New Jersey sits nationally

COUNT-derived placement among 52 US states with at least 365 monitored days in the latest county release. New Jersey's day-weighted Good-day share is 75.5% - cleaner than 42% of that comparison set.

New Jersey Good-day share vs. every US state

Day-weighted share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release

75.5% 42nd percentile higher than 42% of 52 US states

0.0%–5.0%: 0 US states (0%). Below this entry. 5.0%–10.0%: 0 US states (0%). Below this entry. 10.0%–15.0%: 0 US states (0%). Below this entry. 15.0%–20.0%: 0 US states (0%). Below this entry. 20.0%–25.0%: 0 US states (0%). Below this entry. 25.0%–30.0%: 0 US states (0%). Below this entry. 30.0%–35.0%: 0 US states (0%). Below this entry. 35.0%–40.0%: 0 US states (0%). Below this entry. 40.0%–45.0%: 0 US states (0%). Below this entry. 45.0%–50.0%: 0 US states (0%). Below this entry. 50.0%–55.0%: 0 US states (0%). Below this entry. 55.0%–60.0%: 0 US states (0%). Below this entry. 60.0%–65.0%: 2 US states (4%). Below this entry. 65.0%–70.0%: 9 US states (17%). Below this entry. 70.0%–75.0%: 11 US states (21%). Below this entry. 75.0%–80.0%: 11 US states (21%). This entry sits in this band. 80.0%–85.0%: 13 US states (25%). Above this entry. 85.0%–90.0%: 5 US states (10%). Above this entry. 90.0%–95.0%: 1 US states (2%). Above this entry. 95.0%–100.0%: 0 US states (0%). Above this entry. 100.0%–105.0%: 0 US states (0%). Above this entry. This state 0.0% 100% every floor-qualified US state, bucketed by value

Each bar is a band; taller bars hold more US states. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.

Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025

Which counties in New Jersey have the cleanest and most polluted air?

Cleanest counties in New Jersey

Share of monitored days rated Good (AQI 0–50)

  1. 1 Monmouth County 91.3%
  2. 2 Morris County 84.4%
  3. 3 Atlantic County 82.2%
  4. 4 Middlesex County 81.5%
  5. 5 Ocean County 78.8%
  6. 6 Gloucester County 78.7%
  7. 7 Warren County 77.5%
  8. 8 Cumberland County 76.2%
  9. 9 Hunterdon County 74.2%
  10. 10 Passaic County 73.6%
  11. 11 Hudson County 71.5%
  12. 12 Bergen County 71.1%

Good-day share · EPA Air Quality System

County Good % Median AQI
Monmouth 91.3% 36
Morris 84.4% 39
Atlantic 82.2% 36
Middlesex 81.5% 36
Ocean 78.8% 39
Gloucester 78.7% 39
Warren 77.5% 37
Cumberland 76.2% 40
Hunterdon 74.2% 41
Passaic 73.6% 41
Hudson 71.5% 41
Bergen 71.1% 40
Mercer 69.9% 43
Camden 65.6% 44
Union 61.2% 44

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025. See our methodology for how AQI and median figures are computed.

Coverage: 15 counties in New Jersey with active monitoring stations. Unmonitored counties are not represented.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files, aggregated to the state level · 2020–2025

Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.

Informational only, not professional advice. Data from EPA AQS. See our disclaimer.