SmogRank / World / North America / United States / Pennsylvania
Most polluted cities in Pennsylvania, United States
36 measured cities, last 30 days; 0 above the WHO 24-hour guideline. Worst: Lancaster at 6.7 µg/m³, #1,459 in the world.
About 0 people in these 3 cities breathed unhealthy air on an average day over the last 30 days.
Ranked by people: each city's population times its share of unhealthy days, those with a daily mean over 35.4 µg/m³ (US AQI 101+). That is how many people living there breathed unhealthy air on an average day. Only cities measured at 2 or more places at least 3 km apart are ranked: one monitor shouldn't speak for a whole city. Population is the city itself, not its wider metro area.
Cities coloured by their PM2.5 over the last 24 hours. Fires, smoke and ash: Oct 5, the newest UTC day mapped.
- 1West Mifflin 0
- 2Abingtonlow-cost sensors 0
- 3Philadelphia 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
Estimated: cities without a monitor
Pennsylvania cities we can't measure, with model estimates for the last 7 days. Listed by population, not ranked: estimates aren't precise enough to rank. Model estimates from the Copernicus Atmosphere Monitoring Service (CAMS), adjusted to measured cities nearby where there are any. Adjusted, a single day lands within ×1.5 of what a monitor would read about two times in three; unadjusted, it can be off by half or double. Treat them as a guide, not a measurement.
| City | 7-day estimate |
|---|---|
| Reading | ≈ 7 µg/m³ |
| Levittown | ≈ 7 µg/m³ |
| Havertown | ≈ 8 µg/m³ |
| Wilkes-Barre | ≈ 4 µg/m³ |
| Chester | ≈ 8 µg/m³ |
| Mount Lebanon | ≈ 9 µg/m³ |
| Bethel Park | ≈ 9 µg/m³ |
| Wayne | ≈ 8 µg/m³ |
| Radnor | ≈ 8 µg/m³ |
| Williamsport | ≈ 4 µg/m³ |
| Monroeville | ≈ 7 µg/m³ |
| Cranberry Township | ≈ 7 µg/m³ |
| Drexel Hill | ≈ 8 µg/m³ |
| Plum | ≈ 7 µg/m³ |
| Back Mountain | ≈ 4 µg/m³ |
| Easton | ≈ 5 µg/m³ |
| Whitehall Township | ≈ 5 µg/m³ |
| Hazleton | ≈ 7 µg/m³ |
| Springfield | ≈ 8 µg/m³ |
| Pottstown | ≈ 6 µg/m³ |
| New Castle | ≈ 6 µg/m³ |
| Allison Park | ≈ 9 µg/m³ |
| Murrysville | ≈ 7 µg/m³ |
| King of Prussia | ≈ 8 µg/m³ |
| West Chester | ≈ 6 µg/m³ |
| Baldwin | ≈ 9 µg/m³ |
| McKeesport | ≈ 8 µg/m³ |
| Upper Saint Clair | ≈ 9 µg/m³ |
| Carlisle | ≈ 5 µg/m³ |
| Limerick | ≈ 6 µg/m³ |
| Phoenixville | ≈ 6 µg/m³ |
| Lansdale | ≈ 6 µg/m³ |
| Willow Grove | ≈ 8 µg/m³ |
| Hanover | ≈ 5 µg/m³ |
Bad-air episodes in Pennsylvania
- Northern United States and Canada, July 202614 to 21 July 2026, 8 days327 cities548 µg/m³peak, Superior
- North-eastern United States, June and July 202630 June to 2 July 2026, 3 days38 cities32 µg/m³peak, Westerville
- North-eastern United States and Canada, 14 to 19 February 20266 days108 cities54 µg/m³peak, Lancaster
- Pennsylvania, United States, February 20266 February 2026, 1 day11 cities48 µg/m³peak, New Holland
- South-eastern Canada and United States, February 20263 to 4 February 2026, 2 days11 cities40 µg/m³peak, Nepean
- North-eastern United States and Canada, 2 to 3 February 20262 days18 cities33 µg/m³peak, Ann Arbor
Times when many cities around here had PM2.5 at twice their usual or more on the same days.
Use this board
SmogRank, most polluted cities in Pennsylvania, United States, PM2.5, last 30 days to 6 Oct 2026, 23:00 UTC, smogrank.com/us/region/pennsylvania?w=30d.
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.
Updated 2026-10-06 23:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.