Tens of millions of Americans are enduring another day of smoky skies, irritated eyes and bad air quality, as Canadian wildfire smoke spread again over huge swathes of the US, affecting about 109 million people across the midwest, mid-Atlantic and north-east.
The pungent smoke blanketed cities such as Chicago and Detroit, where residents on Friday were warned to stay indoors and reduce activity levels after the air-quality index reached a “hazardous” 361, according to the government website AirNow.
