"Mastering the Air Quality Index: A Beginner's Guide"

Air quality levels in parts of Canada and the US have worsened due to smoke from wildfires, with New York City having the worst air quality of any major city in the world. The Environmental Protection Agency's Air Quality Index (AQI) measures air quality based on five major pollutants regulated by the Clean Air Act. The AQI ranges from zero to 500, with values above 151 indicating a health risk for some people, and values above 301 constituting a "health warning of emergency conditions." The EPA recommends taking precautions to protect yourself from smoke pollution, including limiting outdoor activities and keeping indoor air clean.