Toronto had the worst air quality of any major city in the world on Wednesday, the Swiss air quality monitoring firm IQAir said, as Canadian authorities urged people to stay indoors. Toronto edged out New Delhi and the Democratic Republic of Congo's capital Kinshasa as wildfire smoke turned the skies a hazy yellowish-grey in Canada's largest city. While this year's wildfire season has been fairly muted compared to the devastation caused in recent years, there are more than 800 active fires nationwide.