Median AQI
49
Good
Pennsylvania · County air quality · 2025
Allegheny County, Pennsylvania
Median AQI 49 (Good). 51.6% of monitored days rated Good, direct from EPA Air Quality System stations.
- 49
- Median AQI
- 51.6%
- Good-air days
- 0
- Unhealthy days
- 7%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Allegheny County's air is good on balance, among the most polluted counties nationally, a median AQI of 49 with 51.6% of 182 monitored days in the Good band, driven mainly by PM2.5.
- 49
- median AQI · Good
- 51.6%
- days rated Good
- PM2.5
- main pollutant
- 7%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 129.
Data updated July 2026
- Good · 94 d · 51.6%
- Moderate · 86 d · 47.3%
- USG · 2 d · 1.1%
How did Allegheny County's air break down in 2025?
Across 182 monitored days, 94 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 129 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 182 days monitored. Median AQI: 49 (Good).
Insights: Allegheny County, Pennsylvania. EPA monitors recorded a median Air Quality Index of 49 across 182 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 94 (52%) fell in the Good band (AQI 0–50), 86 (47%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 80, while the worst single-day peak hit 129 (USG). Residents averaged about 15.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (92 days), Ozone (89 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by -44 and the median AQI moved -5 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 129, usg but never Unhealthy. Nearby counties show comparable readings: Adams (73.8% good, AQI 42); Armstrong (68.1% good, AQI 42); Beaver (54.3% good, AQI 47); Berks (65.6% good, AQI 44); Blair (71.9% good, AQI 41); Bradford (77.4% good, AQI 39).
Air Quality Summary
Good Days
51.6%
94 of 182 monitored days
-23.4pp vs 75% target
Max AQI Recorded
129
USG
Health Grade
Moderate
90th-pct AQI 80
Allegheny County, Good days share 51.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
Allegheny 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 182 monitored days across EPA AQI categories.
Good
94
52%
Moderate
86
47%
USG
2
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Allegheny County.
- PM2.5 · 92 days · 50.5%
- Ozone · 89 days · 48.9%
- CO · 1 days · 0.5%
Health Impact Assessment
Moderate
Allegheny County's air quality is rated Moderate based on 51.6% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 51.6% of monitored days in 2025, with a median AQI of 49. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 92 of 182 monitored days.
5-Year Air Quality Trend
Air quality is improving in Allegheny County. Best year: 2024 (175 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 138 | 218 | 10 | 0 | 54 | 128 |
| 2021 | 118 | 240 | 6 | 1 | 57 | 154 |
| 2022 | 129 | 225 | 10 | 1 | 56 | 151 |
| 2023 | 121 | 227 | 15 | 1 | 56 | 237 |
| 2024 | 175 | 182 | 9 | 0 | 52 | 129 |
| 2025 | 94 | 86 | 2 | 0 | 49 | 129 |
How does Allegheny County compare?
How Allegheny County compares
Good-day share worse than US avg
Allegheny County 51.6%
Adams County, Pennsylvania 73.8%
US average 76.5%
Median AQI worse than US avg
Allegheny County 49
Adams County, Pennsylvania 42
US average 38
Unhealthy days / yr about average
Allegheny County 0
Adams County, Pennsylvania 0
US average 0
Other Counties in Pennsylvania
Air quality comparison for nearby counties in Pennsylvania.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Allegheny County.
Arkansas County, Arkansas
AQI 49 · 51.6% good
Ashley County, Arkansas
AQI 49 · 53.9% good
Clayton County, Georgia
AQI 49 · 53.1% good
Cleveland County, Oklahoma
AQI 49 · 53.7% good
Dewey County, Oklahoma
AQI 49 · 56.6% good
Douglas County, Colorado
AQI 49 · 57.9% good
What Allegheny 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 49 means for exposure. Health guidance
- See how Allegheny County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Allegheny County with its Pennsylvania neighbours before drawing a conclusion about the region. All of Pennsylvania
Based on 182 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 Allegheny County, Pennsylvania? ▼
Allegheny County has a median Air Quality Index (AQI) of 49, rated "Good." 51.6% of monitored days (94 out of 182) had good air quality in 2025.
What is the main pollutant in Allegheny County? ▼
The primary pollutant in Allegheny County is Fine Particles (PM2.5), which was the main AQI driver on 92 days (51% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Allegheny County have? ▼
In 2025, Allegheny County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 129.
Is the air quality in Allegheny County getting better or worse? ▼
Air quality in Allegheny County is improving based on 5-year trends (2020-2025). Best year: 2024 with 175 good days. Worst year: 2025 with 94 good days.
What does AQI 49 mean for health? ▼
Allegheny County's median AQI of 49 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 Allegheny County compare to other counties in Pennsylvania? ▼
Allegheny County has 51.6% good air days. Nearby counties in Pennsylvania: Adams (73.8% good), Armstrong (68.1% good), Beaver (54.3% good), Berks (65.6% good), Blair (71.9% good), Bradford (77.4% good).
What is the 90th percentile AQI in Allegheny County? ▼
The 90th percentile AQI for Allegheny County is 80, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 129 (USG).
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.