MON VALLEY (KDKA) — For the past two days, an air monitor in the Mon Valley has registered the worst air quality in the nation.

Don’t let the sunny skies deceive you.

(Photo Credit: KDKA)

“It’s the top of the leaderboard, although it’s the leaderboard we don’t want to be on,” said Matthew Mahalik of CMU’s Breath Project.

Once again, the air near U.S. Steel Clairton Coke Works has hit a Code Red, meaning particulates and ozone are in excess of 150 on the federal air quality index and deemed unhealthy for all who breathe it.

While it’s especially bad in the Mon Valley, since Saturday morning, people in Greenfield, Squirrel Hill and throughout the city have been reporting bad-smelling air on Carnegie Mellon’s Smell Pittsburgh app.

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“A lot of frequent reports are saying it smells like rotten eggs, and that’s usually associated with hydrogen sulfide that is associated with burning coal of coke making,” Mahalik said.

On Monday, a judge approved a class-action lawsuit settlement between U.S. Steel and residents of Clairton over air quality.

This past summer, the steel giant entered into an agreement with the Allegheny County Health Department to make $200 million in environmental improvements at the Coke Works.

But Howard Riger of Eastend Neighbors Corned About Air Pollution says the problem is regional, and U.S. Steel has made such promises in the past.

“We’re stuck with a problem that they don’t seem to want to fix,” Riger said.