Dense wildfire smoke billowing down from Canada and northern Minnesota has set off unhealthy air-quality alerts across the United States.
US President Donald Trump lashed out at Canada, where authorities said more than 200 fires were burning out of control on Friday, calling the pollution “totally unacceptable”.
He wrote on Truth Social: “The United States is being unnecessarily invaded by filthy, polluted, and unhealthy air, the quality of which is dangerous, and totally unacceptable.
“I will call [Canadian Prime Minister Mark Carney] during the day to find out what they are going to do about it.
“We are holding Canada responsible for the fact that they are not properly maintaining their forests... Canada has refused to engage in basic forest management and debris removal, knowing that such refusal will lead to exactly this result.”
Trump accused Canada of “wilful negligence”, saying the cost of pollution ran into the billions of dollars, which must be “added to the tariffs Canada is currently paying”.
Detroit, in the US Midwest, remained the most polluted city in the world, according to tracker IQAir. Washington and Chicago weren’t far behind and officials warned against spending unnecessary time outside.
In New York and neighbouring New Jersey, where the World Cup football final will be played in an open stadium on Monday, the metro area was experiencing air that could be unhealthy for sensitive groups, an improvement after smog on Thursday made the Manhattan skyline barely visible.
But the National Weather Service (NWS) warned the smoke may thicken overnight and into Sunday morning.
White House World Cup taskforce executive director Andrew Giuliani said organisers were “monitoring closely” the air quality.
Joel Dreessen, an air-quality forecaster for the state of Maryland, said the issue for the World Cup final was whether more smoke spilled south after weekend storm systems.
He said: “Some of the models are starting to indicate that we’ll start to pull down some smoke.”
In cities across the Midwest and Northeast, people wore masks outdoors to filter out the dangerous air. In New York, libraries and train stations were handing masks out for free.
Chris Carlsten, who studies the health impacts of fire smoke at the University of British Columbia, told AFP the fine pollution particles from wildfires were particularly harmful on the lungs, with plumes filled with wood and vegetation debris, paint, plastic or metal.
He said as smoke plumes travelled, they underwent “photochemical ageing”, which “seem to make, from everything we understand in the chemistry, the aerosol more toxic”.
Advocates have stressed the connection between repeated episodes of wildfire smoke and climate change.
Mark Parrington, a scientist at the Copernicus Atmosphere Monitoring Service, said climate change was providing conditions for a longer fire season, with higher surface air temperatures and lower soil moisture.
Trump has regularly played down climate change as a phenomenon, often referring to it as a “hoax”.
Meanwhile, fires were worsening in Canada, where more than 200 blazes were burning out of control.
Fires in Ontario have not caused any casualties but several remote communities have been evacuated as dozens of aircraft battle the blazes.
There are also 16 active fires in the US, burning in the Superior National Forest on Minnesota’s border with Canada.
- AFP