Major US cities among world's most polluted as suffering from Canada wildfires

Smoke from wildfires in Canada has again drifted to the US, placing American cities among the most polluted in the world. Detroit, New York and Chicago have the worst air quality in the US, ranking 13th, 15th and 20th, respectively, among the world's most polluted cities, according to real-time data from IQAir on Wednesday afternoon. The National Weather Service has issued an air-quality alert for a large swath of the Upper Midwest and the Great Lakes region, with millions of people expected to be affected.