The US slashed air pollution over the past 60 years. But on Thursday, US cities suffered some of the world’s worst air.

Wildfires in Canada are pouring thick clouds of smoke into the US and will usher in unhealthy air quality for millions of people in Northeast and Midwest.

Wildfires in Canada are pouring thick clouds of smoke into the US and will usher in unhealthy air quality for millions of people in Northeast and Midwest.

States warned residents about air quality issues that could last for days

Wildfires in Canada and Minnesota are sending heavy smoke to the Midwest and Northeast U.S., causing poor air quality alerts.

A massive plume of smoke from wildfires burning across Canada has swept into the United States, degrading air quality across the Midwest, Northeast and Mid-Atlantic.

Around 100 million Americans could be affected by the wildfire smoke, though impacts will vary by location

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

Toronto had the worst air quality of any major city in the world on Wednesday, the Swiss firm IQAir said, as Canadian authorities urged people to stay indoors.

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…

A thick orange haze hung over Toronto on Wednesday 15 July as smoke from wildfires in northwestern Ontario engulfed Canada's largest city, giving it the worst air quality of any…

Massive plumes of Canadian wildfire smoke have started to pour over the border into the United States, bringing dangerous air quality to more than 100 million people in the…

Monitor ranks Toronto as having the worst air quality on earth, surpassing Kinshasa, DR Congo, and New Delhi, India.

Toronto recorded among the worst air quality of all major cities worldwide on Wednesday as thick smoke from wildfires in Ontario blanketed its skyline and drifted into the US,…

Wildfire smoke from Ontario has severely degraded air quality across the northeastern United States. Chicago recorded "Very Unhealthy" levels of fine particulate pollution on…

Wondering why it smells like smoke outside? Canadian wildfires are impacting millions in Ontario, Minnesota, Toronto, New York, Michigan, Wisconsin and Boston.

Millions of Americans face air quality alerts from Minnesota to New York as authorities urge people to stay indoors

Large swaths of the US remain under air quality warnings

Hundreds of fires are burning out of control, and several factors could help bring more smoke to the U.S. for days or even weeks to come.

NEW YORK (AP) — Heavy, pungent smoke from Canadian wildfires darkened skies in the U.S. on Thursday, from the Great Lakes to parts of the East Coast, reducing visibility for

Air quality levels in Chicago, Detroitt and New York reached dangerously high levels on Tuesday as the US cities were shrouded in smoke produced by wildfires raging through…