Median AQI
52
Moderate
Arkansas · County air quality · 2025
Union County, Arkansas
Median AQI 52 (Moderate). 41.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 52
- Median AQI
- 41.8%
- Good-air days
- 0
- Unhealthy days
- 4%
- Cleaner than US counties
Union County's 2025 annual median AQI is 52 (Moderate), with 41.8% Good days
According to the U.S. EPA Air Quality System, Union County, Arkansas posted a 2025 median AQI of 52 (Moderate) across 122 monitored days, with 41.8% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Union County's 41.8% Good-day share places it cleaner than 4% of US counties in 2025.
- Closest median-AQI peer
- Allegheny County (46.0% Good, median AQI 52) is the closest nationwide median-AQI peer to Union County.
- 2020–2025 trend
- Union County's floor-qualifying Good-day share is worsening from 2020 to 2025 (61.2% → 41.8%).
- Median AQI
- Median AQI: 52
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 41.8% of 122 monitored days in the Good band, driven mainly by PM2.5.
- 52
- median AQI · Moderate
- 41.8%
- days rated Good
- PM2.5
- main pollutant
- 4%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 73.
Annual release change
What changed in the 2025 EPA annual release
- Union County's Good-day share fell from 51.2% to 41.8% between the 2024 and 2025 EPA annual releases, a change of -9.4 percentage points.
- Union County's peak single-day AQI fell from 93 to 73 between the 2024 and 2025 EPA annual releases, a change of -20 points.
- Union County's median AQI rose from 49 to 52 between the 2024 and 2025 EPA annual releases, a change of +3 points.
Data updated August 2026
- Good · 51 d · 41.8%
- Moderate · 71 d · 58.2%
How did Union County's air break down in 2025?
Across 122 monitored days, 51 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 73 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 122 days monitored. Median AQI: 52 (Moderate).
Insights: Union County, Arkansas. EPA monitors recorded a median Air Quality Index of 52 across 122 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 51 (42%) fell in the Good band (AQI 0–50), 71 (58%) 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 73 (Moderate). Residents averaged about 12.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (122 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -19.4 points 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 73, moderate but never Unhealthy. Nearby counties show comparable readings: Arkansas (52.9% good, AQI 48); Ashley (55.7% good, AQI 48); Clark (96.7% good, AQI 34); Crittenden (80.8% good, AQI 39); Garland (49.2% good, AQI 51); Jackson (62.3% good, AQI 46).
Air Quality Summary
Good Days
41.8%
51 of 122 monitored days
-33.2pp vs 75% target
Max AQI Recorded
73
Moderate
Health Grade
Poor
90th-pct AQI 62
Union County, Good days share 41.8%
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 122 monitored days across EPA AQI categories.
Good
51
42%
Moderate
71
58%
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 · 122 days · 100.0%
Health Impact Assessment
Poor
Union County's air quality is rated Poor based on 41.8% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 41.8% 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 122 of 122 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Union County. Highest Good-day share: 2020 (61.2%, 74 of 121 monitored 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 | 51 | 71 | 0 | 0 | 52 | 73 |
How does Union County compare?
How Union County compares
Good-day share worse than typical
Union County 41.8%
Allegheny County, Pennsylvania 46.0%
Typical US county 76.0%
Median AQI worse than typical
Union County 52
Allegheny County, Pennsylvania 52
Typical US county 39
Unhealthy days / yr better than typical
Union County 0
Allegheny County, Pennsylvania 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Union County (52), not geographic neighbors.
Allegheny County, Pennsylvania
Median AQI 52 · 46.0% Good-day share
Bexar County, Texas
Median AQI 52 · 43.3% Good-day share
Bibb County, Georgia
Median AQI 52 · 42.7% Good-day share
Hidalgo County, Texas
Median AQI 52 · 44.4% Good-day share
Hinds County, Mississippi
Median AQI 52 · 45.8% Good-day share
Jefferson County, Alabama
Median AQI 52 · 43.6% Good-day share
Same primary pollutant: PM2.5
PM2.5 led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Kent County, Michigan
41.9% Good-day share · median AQI 52
Lake County, Indiana
41.6% Good-day share · median AQI 53
Cook County, Illinois
40.8% Good-day share · median AQI 53
Dallas County, Texas
40.5% Good-day share · median AQI 53
Nueces County, Texas
40.5% Good-day share · median AQI 53
Cuyahoga County, Ohio
43.3% Good-day share · median AQI 53
Arkansas counties on the map
Geographic containment only, other monitored counties in Arkansas, independent of AQI or pollutant match.
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 122 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
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." 41.8% of monitored days (51 out of 122) 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 122 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 73.
Is the air quality in Union County getting better or worse? ▼
Air quality in Union County is worsening across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2020 at 61.2% (74 of 121 days). Lowest qualifying Good-day share: 2025 at 41.8% (51 of 122 days).
What does AQI 52 mean for health? ▼
Union County's median AQI of 52 falls in the "Moderate" category. See the AQI category guide for what each range means for health.
How does Union County compare to other counties in Arkansas? ▼
Union County has 41.8% good air days. Nearby counties in Arkansas: Arkansas (52.9% good), Ashley (55.7% good), Clark (96.7% good), Crittenden (80.8% good), Garland (49.2% good), Jackson (62.3% 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 73 (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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Union County, Arkansas · 2020–2025
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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.