Median AQI
55
Moderate
Ohio · County air quality · 2025
Butler County, Ohio
Median AQI 55 (Moderate). 33.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 55
- Median AQI
- 33.3%
- Good-air days
- 1
- Unhealthy days
- 2%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Butler County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 55 with 33.3% of 273 monitored days in the Good band, driven mainly by PM2.5.
- 55
- median AQI · Moderate
- 33.3%
- days rated Good
- PM2.5
- main pollutant
- 2%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 151.
Data updated July 2026
- Good · 91 d · 33.3%
- Moderate · 177 d · 64.8%
- USG · 4 d · 1.5%
- Unhealthy · 1 d · 0.4%
How did Butler County's air break down in 2025?
Across 273 monitored days, 91 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 151 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 55 (Moderate).
Insights: Butler County, Ohio. EPA monitors recorded a median Air Quality Index of 55 across 273 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 91 (33%) fell in the Good band (AQI 0–50), 177 (65%) registered Moderate readings, and 4 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 77, while the worst single-day peak hit 151 (Unhealthy). Residents averaged about 10.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (204 days), Ozone (69 days). Across the 2020–2025 trend window, good days shifted by -188 and the median AQI moved +14 points, placing the multi-year trajectory at worsening. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Allen (65.9% good, AQI 43); Ashtabula (81.2% good, AQI 43); Athens (80.3% good, AQI 33); Belmont (63.0% good, AQI 42); Clark (59.4% good, AQI 46); Clermont (72.1% good, AQI 43).
Air Quality Summary
Good Days
33.3%
91 of 273 monitored days
-41.7pp vs 75% target
Max AQI Recorded
151
Unhealthy
Health Grade
Poor
90th-pct AQI 77
Butler County, Good days share 33.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
Butler County, Unhealthy-or-worse share 0.4%
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 273 monitored days across EPA AQI categories.
Good
91
33%
Moderate
177
65%
USG
4
1%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Butler County.
- PM2.5 · 204 days · 74.7%
- Ozone · 69 days · 25.3%
Health Impact Assessment
Poor
Butler County's air quality is rated Poor based on 33.3% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 4 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 151. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 204 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Butler County. Best year: 2020 (279 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 279 | 84 | 3 | 0 | 41 | 126 |
| 2021 | 128 | 232 | 5 | 0 | 55 | 116 |
| 2022 | 146 | 215 | 4 | 0 | 53 | 119 |
| 2023 | 107 | 242 | 12 | 4 | 56 | 197 |
| 2024 | 154 | 209 | 3 | 0 | 53 | 122 |
| 2025 | 91 | 177 | 4 | 1 | 55 | 151 |
How does Butler County compare?
How Butler County compares
Good-day share worse than US avg
Butler County 33.3%
Allen County, Ohio 65.9%
US average 76.5%
Median AQI worse than US avg
Butler County 55
Allen County, Ohio 43
US average 38
Unhealthy days / yr worse than US avg
Butler County 1
Allen County, Ohio 0
US average 0
Other Counties in Ohio
Air quality comparison for nearby counties in Ohio.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Butler County.
Cameron County, Texas
AQI 55 · 31.7% good
Montgomery County, Texas
AQI 55 · 30.7% good
Nueces County, Texas
AQI 55 · 35.0% good
Pima County, Arizona
AQI 55 · 37.0% good
Denver County, Colorado
AQI 54 · 44.2% good
Franklin County, Ohio
AQI 54 · 39.8% good
What Butler County's air means for you
On most days the air here is fine, but PM2.5 drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 55 means for exposure. Health guidance
- See how Butler County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Butler County with its Ohio neighbours before drawing a conclusion about the region. All of Ohio
Based on 273 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 Butler County, Ohio? ▼
Butler County has a median Air Quality Index (AQI) of 55, rated "Moderate." 33.3% of monitored days (91 out of 273) had good air quality in 2025.
What is the main pollutant in Butler County? ▼
The primary pollutant in Butler County is Fine Particles (PM2.5), which was the main AQI driver on 204 days (75% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Butler County have? ▼
In 2025, Butler County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 151.
Is the air quality in Butler County getting better or worse? ▼
Air quality in Butler County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 279 good days. Worst year: 2025 with 91 good days.
What does AQI 55 mean for health? ▼
Butler County's median AQI of 55 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 Butler County compare to other counties in Ohio? ▼
Butler County has 33.3% good air days. Nearby counties in Ohio: Allen (65.9% good), Ashtabula (81.2% good), Athens (80.3% good), Belmont (63.0% good), Clark (59.4% good), Clermont (72.1% good).
What is the 90th percentile AQI in Butler County? ▼
The 90th percentile AQI for Butler County is 77, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 151 (Unhealthy).
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.