How did Canada end up with worse air quality than the US?

Year of devastating wildfires meant Canadians were breathing worse air than southern neighbours for first time ever

Canada's pristine air quality has been long praised by its citizens and prized by its government. But the thick plumes of smoke and miles of haze released by a record-breaking season of wildfires deteriorated the country's air so much that it has fallen behind the United States for the first time on record, highlighting the wide-ranging and damaging effects of the blazes.

In its sixth annual World Air Quality report released on Tuesday, the Switzerland-based IQAir found overall air quality in Canada was worse than its southern neighbour. Of the 15 most polluted cities in the two countries, 14 were in Canada. Overall, Canada and the United States were ranked 93 and 102 for their air quality (Bangladesh, at No 1 was the most polluted).