Wildfire smoke degrades air quality in swaths of Ontario, with Toronto ranking among the worst in the world on Monday.

The EPA's Air Quality Index can tell you whether breathing outside air can be harmful. Here's how to read the scale to plan ...

EDT on Tuesday, the National Weather Service reported an air quality alert in effect until Thursday at midnight EDT for ...

The Chicago area recorded ozone levels of 156 late Monday afternoon. Levels above 100 are considered unhealthy. Residents ...

The Illinois Environmental Protection Agency has issued an Air Pollution Action Day for Tuesday, July 15. Here's what to know ...