Pittsburgh, PA Air Quality & Smog

Dominant pollutants, when smog is worst, notable historical episodes, and local agency resources for Pittsburgh, PA — plus how to check the current AQI. For real-time readings, the free Smog Report iOS app pulls live air quality from EPA AirNow.

Dominant pollutants

PM2.5 (steel + coal legacy + topography), ozone (summer).

Seasonal pattern: when smog is worst

Pittsburgh's topography — narrow river valleys hemmed in by hills — concentrates pollution. Allegheny County's Liberty/Clairton air quality, downwind of the Clairton Coke Works (the largest coke-making facility in North America), is the worst in the metro. PM2.5 readings in the Mon Valley regularly exceed the federal standard. Pittsburgh has improved dramatically since the 1970s but still ranks in the worst quartile for PM2.5 among major US metros.

A recent or notable event

June 2019 — a fire at the Clairton Coke Works released sulfur dioxide and PM2.5 across the Mon Valley for over a week.

Local agencies and resources

Allegheny County Health Department runs the local monitor network and has more-aggressive enforcement authority than most county-level US agencies.

• Pennsylvania DEP
• Allegheny County Health Department

How to check air quality in Pittsburgh

The EPA's AirNow.gov publishes the canonical reading from the nearest regulatory monitor. For glanceable iPhone access — including widgets, Live Activities, Siri voice queries, and Apple Watch — install Smog Report. It's free, requires no account, and pulls from the same AirNow API.

For Pittsburgh-specific advisories and alerts that go beyond the federal AirNow feed, check the agency pages above directly.

Common questions about Pittsburgh air quality

Why does Pittsburgh have air-quality and smog problems?

Pittsburgh's topography — narrow river valleys hemmed in by hills — concentrates pollution. Allegheny County's Liberty/Clairton air quality, downwind of the Clairton Coke Works (the largest coke-making facility in North America), is the worst in the metro. PM2.5 readings in the Mon Valley regularly exceed the federal standard. Pittsburgh has improved dramatically since the 1970s but still ranks in the worst quartile for PM2.5 among major US metros.

What are the main air pollutants in Pittsburgh?

Pittsburgh's dominant pollutants are PM2.5 (steel + coal legacy + topography), ozone (summer). The AQI on any given day is usually driven by whichever of these is highest.

Has Pittsburgh had a major air-quality or smog event?

June 2019 — a fire at the Clairton Coke Works released sulfur dioxide and PM2.5 across the Mon Valley for over a week.

How can I check Pittsburgh's air quality right now?

The EPA's AirNow.gov publishes the official reading from the nearest regulatory monitor. For live AQI on your iPhone — with home-screen widgets, Lock Screen Live Activities, Siri, and Apple Watch — the free Smog Report app pulls from the same AirNow feed. No account is required.

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