Air quality in Allegheny County the cleanest in decades

PITTSBURGH — There’s a change in the air - air quality in Allegheny County is the cleanest it’s been in decades and the area is meeting air quality standards for the first time.

We have a long history of trouble when it comes to air quality. At one point, Pittsburgh had some of the worst air in the country to breathe. In the early 1900s, a deadly smog filled the air over the industrial town of Donora, leading to at least 20 deaths and hundreds of people sick with respiratory infections.

It’s not just what’s in the air that can cause problems in our area. Weather patterns can trap pollution and make things worse. In normal conditions, temperatures get colder the higher you go into the atmosphere. Sometimes that gets flipped, with warm air trapping cooler air below. It’s called a temperature inversion and is like putting a lid on a pot. This is what made what happened in Donora so deadly.

“In fall and winter, we have atmospheric conditions that keep pollution from going anywhere where particulate problems, soot builds up in our valleys and doesn’t go anywhere,” said Jim Kelly with the Allegheny County Health Department.

A situation like this happened just before Christmas in 2019. A temperature inversion and light winds trapped pollution and set the stage for a stretch of air quality alert days.

The hills and valleys that define our region can also play a role in holding on to air pollution. Low-lying towns along the rivers are hemmed in by steep hills that block the wind, preventing airflow from carrying away pollution.

“When an inversion sets up, it’s about the height of the river valley. So it effectively creates lids over all the valleys and causes pollution to start working its way from facilities that create a lot of it. It starts working its way up river valleys and all the way into the City of Pittsburgh,” Kelly said.

The EPA uses colors to report daily air quality. You can get that information right from the Severe Weather Team 11 mobile app.

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