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, #1,458 in the world.

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.

Ohio: 27 measured citiesPennsylvania: 36 measured citiesNew York: 10 measured citiesVirginia: 14 measured citiesMaryland: 10 measured citiesDelaware: 7 measured citiesNew Jersey: 19 measured citiesWest Virginia: 4 measured cities#36 Altoona: 3.3 µg/m³#35 Norristown: 4.0 µg/m³#34 Erie: 4.3 µg/m³#33 Bethlehem: 4.4 µg/m³#31 Schlusser: 4.5 µg/m³#32 Warren: 4.5 µg/m³#30 Allentown: 4.6 µg/m³#28 Kennett Square: 4.7 µg/m³#29 State College: 4.7 µg/m³#26 Hermitage: 4.8 µg/m³#27 Wyomissing: 4.8 µg/m³#25 Uniontown: 4.9 µg/m³#24 Monessen: 5.0 µg/m³#22 Bridgeville: 5.2 µg/m³#23 Greensburg: 5.2 µg/m³#21 Scranton: 5.3 µg/m³#20 New Holland: 5.4 µg/m³#18 Johnstown: 5.5 µg/m³#19 New Brighton: 5.5 µg/m³#12 Chambersburg: 5.6 µg/m³#13 Beaver Falls: 5.6 µg/m³#14 Canonsburg: 5.6 µg/m³#15 Hershey: 5.6 µg/m³#16 Lebanon: 5.6 µg/m³#17 Wilkinsburg: 5.6 µg/m³#9 Philadelphia: 5.7 µg/m³#10 Jefferson Hills: 5.7 µg/m³#11 Natrona Heights: 5.7 µg/m³#8 Abington: 5.9 µg/m³#7 Bensalem: 6.0 µg/m³#6 Kennedy Township: 6.1 µg/m³#5 Pittsburgh: 6.3 µg/m³#4 York: 6.4 µg/m³#2 Harrisburg: 6.5 µg/m³#3 West Mifflin: 6.5 µg/m³#1 Lancaster: 6.7 µg/m³
Each dot is a measured city, coloured by its PM2.5; tap a dot to open the city.
← Lancaster 0% 0.75%0
Every measured city in Pennsylvania, United States, one column each, ranked by unhealthy days: height is the share of its measured days that were unhealthy, colour its average. Point at it to read a city; tap to open it.

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.

Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

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.

City7-day estimateBand
Reading≈ 7 µg/m³Good
Levittown≈ 7 µg/m³Good
Havertown≈ 8 µg/m³Good
Wilkes-Barre≈ 4 µg/m³Good
Chester≈ 8 µg/m³Good
Mount Lebanon≈ 9 µg/m³Good
Bethel Park≈ 9 µg/m³Good
Wayne≈ 8 µg/m³Good
Radnor≈ 8 µg/m³Good
Williamsport≈ 4 µg/m³Good
Monroeville≈ 7 µg/m³Good
Cranberry Township≈ 7 µg/m³Good
Drexel Hill≈ 8 µg/m³Good
Plum≈ 7 µg/m³Good
Back Mountain≈ 4 µg/m³Good
Easton≈ 5 µg/m³Good
Whitehall Township≈ 5 µg/m³Good
Hazleton≈ 7 µg/m³Good
Springfield≈ 8 µg/m³Good
Pottstown≈ 6 µg/m³Good
New Castle≈ 6 µg/m³Good
Allison Park≈ 9 µg/m³Good
Murrysville≈ 7 µg/m³Good
King of Prussia≈ 8 µg/m³Good
West Chester≈ 6 µg/m³Good
Baldwin≈ 9 µg/m³Good
McKeesport≈ 8 µg/m³Good
Upper Saint Clair≈ 9 µg/m³Good
Carlisle≈ 5 µg/m³Good
Limerick≈ 6 µg/m³Good
Phoenixville≈ 6 µg/m³Good
Lansdale≈ 6 µg/m³Good
Willow Grove≈ 8 µg/m³Good
Hanover≈ 5 µg/m³Good

Bad-air episodes in Pennsylvania

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, 22:00 UTC, smogrank.com/us/region/pennsylvania?w=30d.

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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 22:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.