SmogRank / World / United States / Pennsylvania / September 2025
Most polluted cities in Pennsylvania, United States, September 2025
34 cities in Pennsylvania, United States ranked by their average PM2.5 over the 30 days. Worst: York at 10.3 µg/m³, #603 of 3,052 cities in the world. Cleanest: Allentown at 5.9. A city needs measurements on 70% of the days to be ranked.
Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.
- 1York 0%
- 2West Mifflin 0%
- 3Beaver Falls 0%
- 4Abingtonlow-cost sensors 0%
- 5Kennedy Township 0%
- 6Lebanon 0%
- 6Monessen 0%
- 6New Holland 0%
- 9Jefferson Hills 0%
- 9Natrona Heights 0%
- 9Pittsburgh 0%
- 12Bensalem 0%
- 12Wilkinsburg 0%
- 14Hershey 0%
- 15Harrisburg 0%
- 16Lancaster 0%
- 17Philadelphia 0%
- 17Canonsburg 0%
- 17Scranton 0%
- 20Uniontown 0%
- 20Greensburg 0%
- 22Johnstown 0%
- 22New Brighton 0%
- 24Schlusser 0%
- 25Wyomissing 0%
- 26Erie 0%
- 26Warren 0%
- 28Kennett Square 0%
- 29Norristown 0%
- 29State College 0%
- 31Hermitage 0%
- 32Altoona 0%
- 32Bethlehem 0%
- 34Allentown 0%
Low-cost sensors: consumer units, counted only in cities with no government-grade monitor; they read close to reference monitors on the whole, but 15 to 25% high in humid air. How we use them.
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
All cities in the world, September 2025 · All cities in United States, September 2025 · Pennsylvania now
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SmogRank, most polluted cities in Pennsylvania, United States, PM2.5, September 2025, smogrank.com/us/region/pennsylvania/history/2025-09 (accessed 6 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.