Median AQI
45
Good
New Jersey · County air quality · 2025
Union County, New Jersey
Median AQI 45 (Good). 62.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 45
- Median AQI
- 62.2%
- Good-air days
- 0
- Unhealthy days
- 18%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Union County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 45 with 62.2% of 180 monitored days in the Good band, driven mainly by PM2.5.
- 45
- median AQI · Good
- 62.2%
- days rated Good
- PM2.5
- main pollutant
- 18%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 71.
Data updated July 2026
- Good · 112 d · 62.2%
- Moderate · 68 d · 37.8%
How did Union County's air break down in 2025?
Across 180 monitored days, 112 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 71 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 180 days monitored. Median AQI: 45 (Good).
Insights: Union County, New Jersey. EPA monitors recorded a median Air Quality Index of 45 across 180 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 112 (62%) fell in the Good band (AQI 0–50), 68 (38%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 62, while the worst single-day peak hit 71 (Moderate). Residents averaged about 18.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (131 days), NO2 (47 days), CO (2 days). Across the 2020–2025 trend window, good days shifted by -86 and the median AQI moved -3 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 71, moderate but never Unhealthy. Nearby counties show comparable readings: Atlantic (79.6% good, AQI 38); Bergen (71.1% good, AQI 40); Camden (69.4% good, AQI 44); Cumberland (73.0% good, AQI 42); Gloucester (72.4% good, AQI 43); Hudson (74.7% good, AQI 41).
Air Quality Summary
Good Days
62.2%
112 of 180 monitored days
-12.8pp vs 75% target
Max AQI Recorded
71
Moderate
Health Grade
Moderate
90th-pct AQI 62
Union County, Good days share 62.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Union County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 180 monitored days across EPA AQI categories.
Good
112
62%
Moderate
68
38%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Union County.
- PM2.5 · 131 days · 72.8%
- NO₂ · 47 days · 26.1%
- CO · 2 days · 1.1%
Health Impact Assessment
Moderate
Union County's air quality is rated Moderate based on 62.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 62.2% of monitored days in 2025, with a median AQI of 45. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 131 of 180 monitored days.
5-Year Air Quality Trend
Air quality is improving in Union County. Best year: 2024 (229 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 198 | 167 | 1 | 0 | 48 | 111 |
| 2021 | 157 | 207 | 1 | 0 | 52 | 139 |
| 2022 | 191 | 174 | 0 | 0 | 49 | 82 |
| 2023 | 163 | 197 | 1 | 3 | 52 | 227 |
| 2024 | 229 | 137 | 0 | 0 | 43 | 85 |
| 2025 | 112 | 68 | 0 | 0 | 45 | 71 |
How does Union County compare?
How Union County compares
Good-day share worse than US avg
Union County 62.2%
Atlantic County, New Jersey 79.6%
US average 76.5%
Median AQI worse than US avg
Union County 45
Atlantic County, New Jersey 38
US average 38
Unhealthy days / yr about average
Union County 0
Atlantic County, New Jersey 0
US average 0
Other Counties in New Jersey
Air quality comparison for nearby counties in New Jersey.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Union County.
Adair County, Oklahoma
AQI 45 · 59.2% good
Allen County, Indiana
AQI 45 · 58.2% good
Atascosa County, Texas
AQI 45 · 58.0% good
Baker County, Florida
AQI 45 · 69.1% good
Carson City County, Nevada
AQI 45 · 79.3% good
Clinton County, Iowa
AQI 45 · 59.9% good
What Union County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 45 means for exposure. Health guidance
- See how Union County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Union County with its New Jersey neighbours before drawing a conclusion about the region. All of New Jersey
Based on 180 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Union County, New Jersey? ▼
Union County has a median Air Quality Index (AQI) of 45, rated "Good." 62.2% of monitored days (112 out of 180) had good air quality in 2025.
What is the main pollutant in Union County? ▼
The primary pollutant in Union County is Fine Particles (PM2.5), which was the main AQI driver on 131 days (73% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Union County have? ▼
In 2025, Union County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 71.
Is the air quality in Union County getting better or worse? ▼
Air quality in Union County is improving based on 5-year trends (2020-2025). Best year: 2024 with 229 good days. Worst year: 2025 with 112 good days.
What does AQI 45 mean for health? ▼
Union County's median AQI of 45 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Union County compare to other counties in New Jersey? ▼
Union County has 62.2% good air days. Nearby counties in New Jersey: Atlantic (79.6% good), Bergen (71.1% good), Camden (69.4% good), Cumberland (73.0% good), Gloucester (72.4% good), Hudson (74.7% good).
What is the 90th percentile AQI in Union County? ▼
The 90th percentile AQI for Union County is 62, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 71 (Moderate).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir 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.