Traffic Is Biggest Source of Chicago Region's Air Pollution

"Downtown Chicago has the highest peak levels of nitrogen dioxide in the country, and is the only site in violation of new stricter guidelines against the irritant, which inflames asthma and other lung conditions.

That news raised the question of how bad is the Chicago area's overall air quality, 40 years after the Clean Air Act as we know it was created.

Several recent rankings may make sensitive readers choke:"

Robert McCoppin reports for the Daily Herald February 7, 2010.