The smoke from #Canada’s #wildfires may be even more #toxic than usual

A legacy of #mining means that #ToxicMetals could be carried along plumes of smoke.

by Matt Simon, June 5, 2025

"More than 200 wildfires are blazing across central and western Canada, half of which are out of control because they’re so hard for crews to access, forcing 27,000 people to evacuate. Even those nowhere near the wildfires are suffering as smoke swirls around Canada and wafts south, creating hazardous air quality all over the midwestern and eastern parts of the United States. The smoke is even reaching Europe.

"As the climate changes, the far north is drying and warming, which means wildfires are getting bigger and more intense. The area burned in Canada is now the second largest on record for this time of year, trailing behind the brutal wildfire season of 2023. That year, the amount of #carbon blazed into the atmosphere was about three times the country’s #FossilFuel emissions. And the more carbon that’s emitted from wildfires — in Canada and elsewhere — the faster the #PlanetaryWarming, and the worse the fires.

" 'There’s obviously the #ClimateFeedback concern,' said Mike Waddington, an environmental scientist at McMaster University in Ontario who studies Canada’s forests. 'But increasingly we’re also concerned about the smoke.'

"That’s because there’s much more to wildfire smoke than charred sticks and leaves, especially where these blazes are burning in Canada. The country’s #forests have long been #mined, operations that loaded #soils and #waterways with #ToxicMetals like #lead and #mercury, especially before clean-air standards kicked in 50 years ago. Now everyone downwind of these wildfires may have to contend with that legacy and those pollutants, in addition to all the other nasties inherent in #WildfireSmoke, which are known to exacerbate respiratory and cardiac problems.

" 'You have there the burning of these organic soils resulting in a lot of carbon and a lot of #ParticulateMatter,' said Waddington. 'Now you have this triple whammy, where you have the metals #remobilized in addition to that.'

"What exactly is lurking in the smoke from Canadian wildfires will require further testing by scientists. But an area of particular concern is around the mining city of #FlinFlon, in #ManitobaCanada, which is known to have elevated levels of toxic metals in the landscape, said Colin McCarter, an environmental scientist who studies pollutants at Ontario’s #NipissingUniversity. Flin Flon’s 5,000 residents have been evacuated as a wildfire approaches, though so far no structures have been destroyed.

"But a fire doesn’t need to directly burn mining operations to mobilize toxicants. For example, in #Yellowknife, in Canada’s #NorthwestTerritories, #GoldMining operations between 1934 and 2004 spread #arsenic as far as 18 miles away, adding to a landscape with an already high concentration of naturally occurring arsenic. In a paper published last year, Waddington and McCarter estimated that between 1972 and 2023, wildfires around Yellowknife fired up to 840,000 pounds of arsenic into the atmosphere. Arsenic is a known carcinogen associated with cardiovascular disease, diabetes, and developmental problems, according to the World Health Organization. (After the 2023 #LahainaFire in Maui, officials reported elevated levels of arsenic, lead, and other toxic substances in ash samples. California officials also found lots of lead in smoke from 2018’s #CampFire.)"

Source:
https://grist.org/climate/canada-wildfire-smoke-toxic-arsenic/?utm_source=firefox-newtab-en-us