The US city of Chicago recorded the worst air quality in the world on Tuesday while smoke from wildfires raging in Canada stretched into Europe.
Chicago was placed in the “unhealthy” red zone with an Air Quality Index reading of 168 at 8am ET, the World Air Quality Index showed. AQI levels between 151 and 200 are deemed “unhealthy”.
Dubai ranked second-worst with an AQI of 163 and Delhi was also placed in the “unhealthy” category with a reading of 152.
Air quality in Doha and Karachi was also deemed “unhealthy for sensitive groups”, with AQI readings of 134 and 110 respectively, while Jakarta's air quality was considered “moderate” at 99.
Minneapolis, Minnesota, approximately 658 kilometres north-west of Chicago, had an AQI of 143, also considered unhealthy for sensitive groups.
Chicago's decline in air quality was caused by smoke from wildfires that continue to rage through Canada, which are also causing hazy conditions and leaving a smoky stench in the Midwestern US city.
Meanwhile, smoke from Canada's fires have reached south-western Europe. An image captured by a Nasa satellite showed that the smoke had crossed over northern Portugal and Spain on Tuesday morning, the agency's Earth Observatory reported.
A map released by the observatory showed a cloud of soot travelling more than 3,200 kilometres across the Atlantic Ocean.
Ground sensors had also detected hazy skies in northern Spain and France. Meanwhile, the British Met Office said the smoke would contributed to “vivid sunrises and sunsets” over the next few days.
Still, the air quality in Europe has so far been unaffected because the smoke from the Canadian wildfires was higher up in the atmosphere.
The Canadian Interagency Forest Fire Centre has reported that more than 76,000 square kilometres of forest have been burnt since January 1, setting a record for area burnt by wildfires in a year.
There are currently 493 active fires across Canada, with 258 considered “out of control”, the agency reported on Tuesday.
