Median AQI
50
Good
Pennsylvania · County air quality · 2025
Philadelphia County, Pennsylvania
Median AQI 50 (Good). 51.6% of monitored days rated Good, direct from EPA Air Quality System stations.
- 50
- 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, Philadelphia County's air is good on balance, among the most polluted counties nationally, a median AQI of 50 with 51.6% of 182 monitored days in the Good band, driven mainly by PM2.5.
- 50
- 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 147.
Data updated July 2026
- Good · 94 d · 51.6%
- Moderate · 83 d · 45.6%
- USG · 5 d · 2.7%
How did Philadelphia 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 147 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 182 days monitored. Median AQI: 50 (Good).
Insights: Philadelphia County, Pennsylvania. EPA monitors recorded a median Air Quality Index of 50 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), 83 (46%) registered Moderate readings, and 5 (3%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 71, while the worst single-day peak hit 147 (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 (100 days), Ozone (77 days), NO2 (4 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by -118 and the median AQI moved +3 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 147, usg but never Unhealthy. Nearby counties show comparable readings: Adams (73.8% good, AQI 42); Allegheny (51.6% good, AQI 49); Armstrong (68.1% good, AQI 42); Beaver (54.3% good, AQI 47); Berks (65.6% good, AQI 44); Blair (71.9% good, AQI 41).
Air Quality Summary
Good Days
51.6%
94 of 182 monitored days
-23.4pp vs 75% target
Max AQI Recorded
147
USG
Health Grade
Moderate
90th-pct AQI 71
Philadelphia County, Good days share 51.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
Philadelphia 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
83
46%
USG
5
3%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Philadelphia County.
- PM2.5 · 100 days · 54.9%
- Ozone · 77 days · 42.3%
- NO₂ · 4 days · 2.2%
- CO · 1 days · 0.5%
Health Impact Assessment
Moderate
Philadelphia 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 50. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 100 of 182 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Philadelphia County. Best year: 2020 (212 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 212 | 149 | 5 | 0 | 47 | 119 |
| 2021 | 137 | 217 | 9 | 2 | 54 | 153 |
| 2022 | 155 | 206 | 4 | 0 | 52 | 113 |
| 2023 | 83 | 268 | 9 | 3 | 58 | 331 |
| 2024 | 173 | 183 | 10 | 0 | 52 | 136 |
| 2025 | 94 | 83 | 5 | 0 | 50 | 147 |
How does Philadelphia County compare?
How Philadelphia County compares
Good-day share worse than US avg
Philadelphia County 51.6%
Adams County, Pennsylvania 73.8%
US average 76.5%
Median AQI worse than US avg
Philadelphia County 50
Adams County, Pennsylvania 42
US average 38
Unhealthy days / yr about average
Philadelphia 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 Philadelphia County.
Adams County, Colorado
AQI 50 · 50.2% good
Albany County, Wyoming
AQI 50 · 51.9% good
Boulder County, Colorado
AQI 50 · 50.9% good
Davidson County, North Carolina
AQI 50 · 50.2% good
Davidson County, Tennessee
AQI 50 · 51.8% good
Gila County, Arizona
AQI 50 · 52.0% good
What Philadelphia 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 50 means for exposure. Health guidance
- See how Philadelphia County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Philadelphia 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 Philadelphia County, Pennsylvania? ▼
Philadelphia County has a median Air Quality Index (AQI) of 50, rated "Good." 51.6% of monitored days (94 out of 182) had good air quality in 2025.
What is the main pollutant in Philadelphia County? ▼
The primary pollutant in Philadelphia County is Fine Particles (PM2.5), which was the main AQI driver on 100 days (55% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Philadelphia County have? ▼
In 2025, Philadelphia County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 147.
Is the air quality in Philadelphia County getting better or worse? ▼
Air quality in Philadelphia County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 212 good days. Worst year: 2023 with 83 good days.
What does AQI 50 mean for health? ▼
Philadelphia County's median AQI of 50 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 Philadelphia County compare to other counties in Pennsylvania? ▼
Philadelphia County has 51.6% good air days. Nearby counties in Pennsylvania: Adams (73.8% good), Allegheny (51.6% good), Armstrong (68.1% good), Beaver (54.3% good), Berks (65.6% good), Blair (71.9% good).
What is the 90th percentile AQI in Philadelphia County? ▼
The 90th percentile AQI for Philadelphia County is 71, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 147 (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.