Millions still under air quality warnings in US as wildfire smoke begins to clear

North-eastern states remain under air pollution alerts though National Weather Service says to expect ‘some improvement’

Millions of Americans remained under air quality warnings on Friday, even as smoke from hundreds of Canadian wildfires began to dissipate in the north-eastern US.

Moderate to unhealthy air quality continued to linger across a swathe of the country, from the midwest to the Atlantic coast, the National Weather Service said, although it said “some improvement” will continue this weekend.