Rare that the boreal forest, Chibougamau or Uashat Mak Mani-Utenam make talk as far as New York and Philadelphia. The cloud of smog created by the forest fires in Quebec blurs the sky over much of the American Northeast, to the point where the air quality indices are almost all red. But how did these contaminants travel hundreds of miles? And will this phenomenon remain rare?
While we were still surprised Monday that the smoke from the raging forest fires covers Montreal, she went to North Carolina on Thursday. The air quality index had returned to “good” in Montreal. The concentration of fine particles, however, was almost 20 times higher than the threshold established by the World Health Organization (WHO) for human health in the Big Apple. The US capital has also raised its risk level to a purple code, an unprecedented move according to the council of governments of metropolitan Washington.
“It’s clear that all the factors have been brought together for several years, it’s really a conjunction of several things”, begins Philippe Lucas-Picher, professor in the Department of Earth and Atmospheric Sciences at UQAM.
“Obviously you need large fires as a base source,” he said to set the table. Thursday there were about 140 active fires on Quebec territory, including 80 classified as “out of control” by the Society for the Protection of Forests against Fire (SOPFEU).
The second condition present is a depression, “an area of low pressure over the eastern seaboard of North America, which creates an ‘anticyclonic’ atmospheric circulation,” says Patrick Hayes, professor of analytical and atmospheric chemistry. at the University of Montreal. The air mass moves counter-clockwise, takes its breath over northern Quebec and pushes it towards the northeastern part of the United States.
This type of system “is not that rare”, specifies Jules Blais, another expert in environmental pollutants, meanwhile from the University of Ottawa, but its duration explains the scope of the current phenomenon.
The other key element, mentioned by all the specialists consulted, is the north wind which has been blowing for several days. “That’s what explains the rather cool temperatures right now in Montreal. There is a constant circulation from north to south which pushes the depression in a corridor towards New York, ”explains Mr. Lucas-Picher. Washington is further south than this city, but in “the same corridor”.
It is also that “the plume of smoke did not have the chance to disperse”, he adds, continuing to form a very thick compact mass which inconveniences our neighbors to the south.
A very (re)marked episode of smog
The overwhelming majority of major American daily newspapers put the appalling air quality on the front page Thursday morning, from the east coast to San Francisco. THE New York Post used one of the formulations that caused the most reaction on social networks. “Blame Canada” headlined its orange-accented front page: “It’s the most unhealthy thing to come out of Canada after poutine,” it reads in smaller print.
A “red code” was still in effect in New York, Baltimore and Philadelphia at the time of this writing.
In a more serious tone, the washington post headlined “A Burning Truth: The Climate Threat to Health Is Inevitable”. The wildfires in Canada have “underscored that the threat to human health from climate change transcends national borders,” the article continued.
On the west coast, it was rather an empathetic tone that prevailed: “The wildfires in Canada are fueling a health scare that Californians know all too well,” wrote the San Francisco Chronicle.
Anything but an anecdote
“Depression does not move, it is stationary. And the north wind continues to blow. It’s an open faucet that pushes the particles directly south,” summarizes meteorologist Gilles Brien. He is alarmed by the poor air quality south of the border, but not only that. His explanations came out of the purely professional framework, he who was waiting for his brother-in-law and his family evacuated from Chibougamau.
The smog alert is still valid for Abitibi, where the concentration of fine particles of less than 2.5 micrometers (PM2.5 microparticles) in the air reaches 3 to 4 times the Environment Canada alert threshold , where he worked for several decades.
These particles are of concern because they are small enough to enter human lungs and end up in the bloodstream. “It’s a form of unburned waste, carbon products much smaller than a hair”, illustrates Mr. Brien.
The threshold established by the WHO is 15 micrograms per cubic meter for daily exposure and 5 micrograms for annual exposure, which is therefore more chronic to this type of smog.
By early Thursday afternoon, Toronto was on course to have that concentration several times over, sadly catching up with the orange horizons of smoky skies across the United States. The forecast of rain for the afternoon and the night gave a certain glimmer of hope there, just like in Ottawa “where we really breathe better than yesterday”, says Professor Blais, from his office in this city. .
Environment Canada is also able to predict where the wildfire smoke cloud is heading using a state-of-the-art model, says Professor Blais.
The Americans will thus breathe the trees pulverized by the fires of the North Shore, Abitibi and northern Quebec for a few more days, confirms Philippe Lucas-Picher. “It highlights that the air circulates and does not stop at national borders,” he says.
Climate prediction models show that the number and intensity of forest fires will increase in Quebec over the next few years. “It’s the new normal and it’s a good reminder that everything is interconnected,” concludes Mr. Blais.