Washington DC and Philadelphia latest to suffer hazardous air as smoke from Canada wildfires sweeps south

Summary

1. Millions across North America are being advised to wear high-grade masks outdoors due to air pollution created by intense wildfires in Canada
2. Pride events and baseball games have been postponed due to the smoke, with Washington DC recording some of the worst air pollution levels in the world
3. Flights have been grounded and delayed at some major US airports due to wildfire smoke causing low visibility
4. The Canadian government says nearly 100 million people in the US and Canada are currently experiencing very poor air quality
5. More than 400 fires are burning across Canada and 236 are out of control
6. Hundreds of firefighters from the US, Europe, Australia, New Zealand and South Africa have been deployed to Canada, and more are on the way