Allegheny, Pennsylvania vs Philadelphia, Pennsylvania Air Quality

Side-by-Side Analysis

Philadelphia, Pennsylvania outperforms Allegheny, Pennsylvania on overall air quality with a Grade C (59/100) versus C (54/100). Philadelphia, Pennsylvania's 5-year median AQI of 52 sits in the "Moderate" range, while Allegheny, Pennsylvania averages 56 ("Moderate") — a 4-point gap that shows up consistently in year-over-year readings, not just in a single year.

The two cities are moving in opposite directions: Allegheny, Pennsylvania is stable (-0.2 AQI/yr) while Philadelphia, Pennsylvania is improving (-0.5 AQI/yr). Over time, today's ranking may flip if these trends hold.

What's in the Air

Both cities share the same dominant pollutant: Fine Particulate Matter (PM2.5). These cities' dominant issue is fine particulate matter — typically driven by combustion (vehicles, wildfire smoke, industry, residential wood burning). PM2.5 is the air pollutant most strongly linked to long-term cardiovascular and respiratory disease because the particles penetrate the bloodstream.

Health Implications

Over a 5-year window, Allegheny, Pennsylvania averages roughly 11 unhealthy air days per year (AQI above 100, where sensitive groups should limit outdoor exertion) versus 8 for Philadelphia, Pennsylvania. The two cities offer comparable counts of unhealthy days, suggesting that day-to-day exposure planning would look similar for residents of either. For long-term residents, the cleaner-air city is associated with measurably better outcomes on respiratory disease, cardiovascular events, and life expectancy — Harvard cohort research consistently finds 0.5 to 1.0 years of additional life expectancy for each 10-µg/m³ reduction in long-term PM2.5 exposure.