CNN: Air Pollution from Canada's Wildfires Threatens 50 Million People in USA

 Air quality levels are slowly improving across the northeastern United States and Midwest, as smoke from wildfires in Canada begins to clear.

And the US (CNN) channel reported on Friday that the number of people who are still subject to air quality warnings in the United States of America (USA) decreased from 75 million people the last Wednesday and Thursday to almost 50 million people.

Hundreds of firefighters from around the world have flocked to Canada to help fight wildfires, which Canadian Prime Minister Justin Trudeau said was the country's worst-ever wildfire season.

Smoke from more than 400 wildfires has caused breathing difficulties for millions of people, triggered air quality alerts across states and counties, and caused thousands of flights and baseball games to be delayed across the East Coast of the United States.