Mill Run, Pennsylvania Air Quality
Mill Run air quality today — the AQI, the main pollutant, and whether it’s safe to exercise outside right now
Mill Run, PA · Air quality right now
The air quality index in Mill Run, PA is 29 (Good) right now — safe for outdoor activity.
Is it safe to be outside in Mill Run today?
AQI 29 Yes — air quality is Good
Air is clean — great for outdoor activity.Main pollutant: OzoneObserved 11:00 AM EDT
Pollutants right now
- PM2.55.2 µg/m³fine particles — smoke, exhaust, soot
- PM105.3 µg/m³coarse particles — dust, pollen, ash
- Ozone66 µg/m³Main pollutantsmog — builds on hot, sunny days
- NO₂1.7 µg/m³nitrogen dioxide — traffic, combustion
ExerciseOK to run — no air-quality limits on outdoor exercise.
How to read Mill Run’s air quality
Guides: The AQI Scale, Explained · Air Quality Alerts, Decoded · How to Read a Wildfire Smoke Map · Why Wildfire Smoke Travels 1,000 Miles.
Air quality over time in Mill Run
Across the EPA’s county records from 2020 to 2025, Mill Run’s cleanest year was 2024 (median AQI 37) and its most polluted was 2021 (median AQI 45); the typical (median) day has trended cleaner since 2020.
| Year | Median AQI | Unhealthy+ | Main pollutant | USG | Moderate | Good |
|---|---|---|---|---|---|---|
| 2020 | 43 | 0 | PM2.5 | 0 | 98 | 262 |
| 2021 | 45 | 0 | PM2.5 | 2 | 128 | 206 |
| 2022 | 44 | 0 | PM2.5 | 0 | 129 | 234 |
| 2023 | 43 | 5 | PM2.5 | 1 | 123 | 229 |
| 2024 | 37 | 0 | Ozone | 0 | 70 | 296 |
| 2025 | 40 | 0 | Ozone | 1 | 83 | 279 |
“USG” is Unhealthy for Sensitive Groups (AQI 101–150); “Unhealthy+” combines the Unhealthy, Very Unhealthy, and Hazardous days. In 2024 the EPA tightened the annual fine-particle (PM2.5) standard to 9 µg/m³ from the previous 12 µg/m³, so counties near the old limit read worse against the new one. Source: EPA AQS annual summaries, 2020–2025.
Frequently asked
- What was the worst year for air quality in Mill Run?
- In the EPA's 2020–2025 county records, 2023 had the most days above AQI 100: 6 days (1 Unhealthy for Sensitive Groups, 5 Unhealthy or worse). The highest median AQI came in 2021 (45; 2023's was 43).
- How many unhealthy air days does Mill Run have?
- Across 2020–2025, under 1% of the days reported for Mill Run's county had an AQI above 100 (9 of 2146), about 2 days a year. 2025 had 1 day.
- What's the main air pollutant in Mill Run?
- PM2.5 drove Mill Run's county AQI on the most days in 4 of 6 years (2020–2025); Ozone in 2024, 2025.