Median AQI
52
Moderate
Arkansas · County air quality · 2025
Union County, Arkansas
Median AQI 52 (Moderate). 44.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 52
- Median AQI
- 44.0%
- Good-air days
- 0
- Unhealthy days
- 5%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Union County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 52 with 44.0% of 91 monitored days in the Good band, driven mainly by PM2.5.
- 52
- median AQI · Moderate
- 44.0%
- days rated Good
- PM2.5
- main pollutant
- 5%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 70.
Data updated July 2026
- Good · 40 d · 44.0%
- Moderate · 51 d · 56.0%
How did Union County's air break down in 2025?
Across 91 monitored days, 40 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 70 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 91 days monitored. Median AQI: 52 (Moderate).
Insights: Union County, Arkansas. EPA monitors recorded a median Air Quality Index of 52 across 91 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 40 (44%) fell in the Good band (AQI 0–50), 51 (56%) 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 70 (Moderate). Residents averaged about 13.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (91 days). Across the 2020–2025 trend window, good days shifted by -34 and the median AQI moved +7 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 70, moderate but never Unhealthy. Nearby counties show comparable readings: Arkansas (51.6% good, AQI 49); Ashley (53.9% good, AQI 49); Clark (97.5% good, AQI 35); Crittenden (79.8% good, AQI 41); Garland (52.8% good, AQI 49); Jackson (65.9% good, AQI 44).
Air Quality Summary
Good Days
44.0%
40 of 91 monitored days
-31.0pp vs 75% target
Max AQI Recorded
70
Moderate
Health Grade
Poor
90th-pct AQI 62
Union County, Good days share 44.0%
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 91 monitored days across EPA AQI categories.
Good
40
44%
Moderate
51
56%
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 · 91 days · 100.0%
Health Impact Assessment
Poor
Union County's air quality is rated Poor based on 44.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 44.0% of monitored days in 2025, with a median AQI of 52. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 91 of 91 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Union County. Best year: 2020 (74 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 74 | 47 | 0 | 0 | 45 | 90 |
| 2021 | 66 | 50 | 0 | 0 | 48 | 74 |
| 2022 | 65 | 50 | 0 | 0 | 47 | 100 |
| 2023 | 59 | 59 | 1 | 0 | 51 | 102 |
| 2024 | 62 | 59 | 0 | 0 | 49 | 93 |
| 2025 | 40 | 51 | 0 | 0 | 52 | 70 |
How does Union County compare?
How Union County compares
Good-day share worse than US avg
Union County 44.0%
Arkansas County, Arkansas 51.6%
US average 76.5%
Median AQI worse than US avg
Union County 52
Arkansas County, Arkansas 49
US average 38
Unhealthy days / yr about average
Union County 0
Arkansas County, Arkansas 0
US average 0
Other Counties in Arkansas
Air quality comparison for nearby counties in Arkansas.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Union County.
Duval County, Florida
AQI 52 · 40.7% good
Hinds County, Mississippi
AQI 52 · 43.4% good
Jefferson County, Texas
AQI 52 · 42.4% good
McLennan County, Texas
AQI 52 · 43.4% good
Orange County, California
AQI 52 · 44.5% good
Wayne County, Michigan
AQI 52 · 46.4% 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 52 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 Arkansas neighbours before drawing a conclusion about the region. All of Arkansas
Based on 91 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, Arkansas? ▼
Union County has a median Air Quality Index (AQI) of 52, rated "Moderate." 44.0% of monitored days (40 out of 91) 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 91 days (100% 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 70.
Is the air quality in Union County getting better or worse? ▼
Air quality in Union County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 74 good days. Worst year: 2025 with 40 good days.
What does AQI 52 mean for health? ▼
Union County's median AQI of 52 falls in the "Moderate" 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 Arkansas? ▼
Union County has 44.0% good air days. Nearby counties in Arkansas: Arkansas (51.6% good), Ashley (53.9% good), Clark (97.5% good), Crittenden (79.8% good), Garland (52.8% good), Jackson (65.9% 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 70 (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.