CHICAGO (CBS) — The Chicago area’s air quality again received failing grades in the latest report by the American Lung Association.

WBBM Newsradio’s Bernie Tafoya reports the Chicago area received an F in the Lung Association’s annual “State Of The Air” report, due to the region’s high levels of smog and soot.

The Chicago metropolitan area — covering 20 counties in northeast Illinois, northwest Indiana, and southern Wisconsin — ranked 14th worst in the nation for 24-hour particle pollution – also known as soot – and 20th worst for high ozone levels – also known as smog – and annual particle pollution, according to the Lung Association.

“Here in Cook County, what we’re seeing is unfortunately a negative trend, compared to what we’re seeing nationwide,” said Mike Kolleng, manager of the Lung Association’s Healthy Air Campaign.

He said the Lung Association’s air quality report released Wednesday provides a snapshot of air quality from 2010 to 2012. For real-time air quality, he suggested looking at the Lung Association’s “State of the Air” app for mobile devices.

“Especially when it’s mothers with young children, or elderly people, people with asthma or COPD,” he said. “They can really use that to determine kind of whether there’s outdoor play day or something like that.”

Much of the air pollution in the Chicago area can be blamed on its status as a leading transportation hub, with two major airports, several highways with heavy trucking traffic, and the nation’s main freight rail network.

Kolleng said the worst pollution can be found where there are high concentrations of cars, trucks, and buses.

“Especially near 90/94, Lake Shore Drive, you’re really seeing just these pockets of air quality that are really poor,” he said.

The Lung Association said nearly half of all Americans live in counties where pollution makes the air unhealthy to breathe.