Canadian wildfire smoke is travelling south and making it difficult for some Americans to enjoy their summer, according to a letter from six members of Congress to Canada's ambassador in Washington.

"We write to you today on behalf of our constituents who have had to deal with suffocating Canadian wildfire smoke filling the air to begin the summer," begins the letter, published Monday and addressed to Ambassador Kirsten Hillman.

It was signed by Republican House representatives Tom Tiffany and Glenn Grothman of Wisconsin and Brad Finstad, Michelle Fischbach, Pete Stauber and Tom Emmer of Minnesota.

"In our neck of the woods, summer months are the best time of the year to spend time outdoors recreating, enjoying time with family, and creating new memories, but this wildfire smoke makes it difficult to do all those things," says the letter, which can be read in full here.

The representatives ask how the federal government plans to mitigate the wildfire smoke, attributing "a lack of active forest management" as a major driver of Canadian wildfires, and suggesting that some of the fires began with arson.

"With all the technology that we have at our disposal, both in preventing and fighting wildfires, this worrisome trend can be reversed if proper action is taken."

Canada takes wildfire mitigation 'very seriously,' says embassy

Research shows that climate change, largely driven by fossil fuel use, is exacerbating wildfires in both Canada and the United States.

While a proportion of wildfires is caused by human activity — like unattended campfires — and a Quebec man pleaded guilty to arson last year after he was arrested for igniting 14 fires, there is no indication that widespread arson is behind the wildfires.

Lightning causes about half of them and burns the most area, per the Canadian National Fire Database. There are currently 526 active wildfires in Canada, according to the Canadian Interagency Forest Fire Centre.

"Canada takes the prevention, response and mitigation of wildfires very seriously," the Canadian Embassy said in a statement responding to the letter. "[The letter] has been shared with the relevant Canadian agencies. We will respond in due course."

Natural Resources Canada told CBC News via an emailed statement that "Canadian firefighters, first responders and volunteers continue to work tirelessly to protect lives and property" from the present wildfires.

The department said it "actively collaborates with provinces, territories, Indigenous communities and international partners to address the impacts of wildfires."

CBC News has reached out to all six representatives for an interview. A spokesperson for Rep. Stauber declined the interview request. 

'Smoke blows both ways'

Lightning-caused fires are "often in remote areas that are difficult to get to and then very difficult to control," said Lori Daniels, a wildfire scientist at the University of British Columbia's Department of Forest and Conservation Sciences.

Some of the wildfires currently raging in Canada began in 2023 and are ongoing, she said. 

"Because of global warming, it is so hot and dry in the north that those fires [are] burning underground in the winter," Daniels said. "And then, in the spring and summer, coming back up to the surface again in these very remote areas and in ecosystems where it's incredibly difficult to stop the fires."

"So it's not that it's for lack of effort, but we're looking at extreme situations in very remote areas for those fires."

The representatives' letter does not mention that thousands of Canadians have been evacuated from their homes this wildfire season or that two Canadians died in Manitoba's Lac du Bonnet in May as a result of the fires. 

"Smoke blows both ways across that border," said Daniels.

Most recently, smoke from wildfires in California and Washington state have drifted northward, impacting air quality in Western Canada. 

Substantially reducing smoke 'a pipe dream'

"We have to recognize that we have the second-largest country in the world," said Glenn McGillivray, a wildfire mitigation expert and managing director at the Institute for Catastrophic Loss Reduction in Toronto. "The boreal forest makes up about 60 per cent of our land mass.

"We're talking about an incredibly massive area."

He said that at least half of Canadian wildfires start with lightning. "To be able to say that we can manage the forest and reduce this substantially is, I think, a pipe dream."

Canada has used prescribed burning as a mitigation tactic in the past — a type of controlled fire that burns the buildup of fuel on forest floors to undercut the intensity of future wildfires, also making them easier to control or put out, according to Parks Canada.

The practice, which originated in Indigenous communities, has a number of benefits for the natural ecosystem. "It's a question of having good fire on the landscape versus bad fires — these big, rip-roaring crown fires that burn huge areas," said McGillivray.

Both experts who spoke to CBC News noted that the health effects of wildfire smoke should be taken seriously. The smoke is an air pollutant that can impact people's health, according to the B.C. Centre for Disease Control.

It recommends a number of individual mitigation strategies to lessen the effects of wildfire smoke, such as wearing an N-95 mask if working outdoors, limiting outdoor exercise, using a HEPA air cleaner in your home, drinking water and monitoring local air quality indices.