The EPA's Air Quality Index (AQI) measures how safe, unhealthy, or hazardous the air outside is. Here's a guide on how to read the AQI.

The smoke from the Canadian wildfires is causing air quality issues in the U.S. See where.

TORONTO/NEW YORK: Toronto’s air quality ranked the worst among major cities globally on Wednesday as wildfire smoke from northwestern Ontario blackened skies and spread into the…