US President Donald Trump on Friday threatened to impose additional tariffs on Canada, accusing Ottawa of failing to manage its forests and allowing wildfire smoke to blanket large parts of the United States with what he described as “filthy, polluted and unhealthy air”.
In a post on Truth Social, Trump said Canada would be held responsible for deteriorating air quality in several American cities and warned that the economic costs of the smoke would be added to existing US tariffs on Canadian imports.
“We are holding Canada responsible for the fact that they are not properly maintaining their forests… and the United States is being unnecessarily invaded by filthy, polluted, and unhealthy air,” Trump wrote, calling the situation “dangerous” and “totally unacceptable”.
He said he planned to speak with Canadian Prime Minister Mark Carney to seek an explanation and discuss Ottawa’s response.
“I will call the Prime Minister during the day to find out what they are going to do about it. The cost is incalculable!” Trump said.
The US president also accused Canada of “wilful negligence” in failing to undertake adequate forest management and debris removal, claiming the recurring wildfire smoke had caused billions of dollars in losses to the United States.
“The cost of this pollution must of necessity be added to the tariffs Canada is currently paying,” he said.
Trump’s remarks came as smoke from hundreds of active wildfires in Canada drifted south, prompting air quality alerts across several US states. According to NASA, smoke from nearly 850 active wildfires in Canada—including more than 180 in Ontario—has spread across more than 20 US states, from the Upper Midwest to the Northeast.
The Canadian Interagency Forest Fire Centre said 888 wildfires were burning across the country on Friday, with most classified as out of control. More than 190 of the fires were in Ontario.
The smoke has significantly affected air quality in states including Minnesota, Michigan, Pennsylvania, Ohio and New York. Air quality monitoring platform IQAir reported that Detroit recorded the world’s worst air quality on Friday, followed by Chicago, Washington DC and New York.
Trump’s tariff threat follows criticism from several Republican lawmakers, who accused Canada of failing to take sufficient action to prevent wildfire smoke from repeatedly crossing the border. In a letter to Canadian authorities, Representatives John James, John Moolenaar, Jack Bergman and Lisa McClain wrote: “We are done accepting apologies in place of action,” adding that “American lungs are paying the price for Canadian inaction, year after year.”
Canadian officials had not responded to Trump’s latest comments at the time of publication. Earlier, Prime Minister Mark Carney said Canada and the United States shared responsibility for tackling climate change, while Ontario Premier Doug Ford urged Washington to provide additional firefighting support instead of criticising Canada’s response.
Scientists, however, said the movement of wildfire smoke is driven primarily by weather patterns rather than national borders. Patrick James, a professor at the University of Toronto, noted that “weather doesn’t care about international borders” and pointed out that smoke from major US wildfires has also affected Canada in recent years. Experts added that many of the current fires are burning in remote boreal forests, where detection and containment are inherently difficult, and that while forest management can reduce fire risk near populated areas, it cannot eliminate wildfires across such vast ecosystems.
