For a Brief Time, Chicago Registers World's Worst Air Quality

Chicago briefly had the worst air quality in the world on Thursday as measured by global rankings from IQAir, though the city was surpassed later in the afternoon by Kinshasa, in the Democratic Republic of the Congo.

This extreme air pollution was caused by heavy smoke drifting in from Canadian wildfires, blanketing the region and pushing Chicago's air quality index into the "unhealthy" and even "dangerous" territory, according to reports in the Chicago Sun-Times and The Washington Post. 

So while Chicago did report having the worst air quality in the world for a few hours, it was a spike tied to wildfire smoke, not the city's normal conditions.

The smoke largely came from fires in Saskatchewan and Manitoba. A stagnant high-pressure system trapped the smoke across the Midwest, the Post said. 

The Sun-Times reported that during the wildfire event, other major U.S. cities, such as Minneapolis and Detroit, also ranked among the worst in the world. 

Climate change authorities say that wildfire seasons may become more frequent, making this type of air quality event more common moving forward, the Post reported.