Climate change is making it harder to breathe

By Martin LaSalle May 15th, 2026

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In 5 seconds Wildfire smoke, extreme heat and longer pollen seasons are exacerbating the effects of lung diseases, especially for vulnerable groups, and it’s only going to get worse, warns a new Canadian study.

During the summer of 2023, 15 million hectares of forest burned, briefly propelling Montreal into the ranks of the world’s most polluted cities. Between 2020 and 2024, smoke from forest fires is estimated to have caused an average of 1,400 premature deaths per year.
Photo : Getty

Climate change is already worsening lung diseases for millions of Canadians, and healthcare systems need to adapt quickly to the developments.

That’s the conclusion of a literature review published in the Canadian Journal of Respiratory, Critical Care, and Sleep Medicine by Dany Doiron, a professor at Université de Montréal’s School of Public Health, with Jeffrey R. Brook (University of Toronto) and Jean Bourbeau (McGill University).

Since 1948, the average temperature in Canada has risen by 2°C—nearly double the global warming rate—leading to more frequent heat waves, droughts and wildfires.

At the same time, outdoor air pollution—primarily fine particulate matter or PM_2.5—is responsible for 15,300 premature deaths, 35 million days of acute respiratory symptoms, and 9,200 cases of chronic bronchitis in adults each year in Canada, according to a 2021 Health Canada study.

Wildfires erasing decades of progress

Since the 1970s, environmental regulations have significantly reduced air pollution in Canada, but this progress is now threatened.

“Recent studies show that a rise in fine particulate matter due to more intense wildfires linked to climate change is now reversing this trend, particularly on the country’s West Coast,” said Doiron.

Data for the 2023 Canadian wildfire season show the magnitude of the impacts. Wildfires burned 15 million hectares—six times the historical average. Smoke from the fires briefly propelled Montreal to the top of the list of the world’s most polluted cities in July 2023. In Ontario, emergency room visits for asthma were up 24 per cent.

It’s estimated that exposure to smoke from the 2023 Canadian wildfires was responsible for 1,300 acute and 8,300 chronic deaths across Canada. Between 2020 and 2024, smoke from wildfires is estimated to have caused an average of 1,400 premature deaths per year in Canada.

Projections for the coming decades are alarming: by the 2050s, concentrations of fine particulate matter linked to wildfires could almost double, and by 2100, wildfires could occur 75 per cent more frequently than they do today.

In addition to the toll on human health, the chronic health effects of wildfire smoke in Canada have a staggering annual financial impact, estimated at between $4.3 billion and $19 billion.

Dany Doiron, professor in the Department of Environmental and Occupational Health at Université de Montréal
Photo : Dany Doiron

Worsened by heat, pollen and mould

Beyond wildfire smoke, extreme heat poses its own threat to the respiratory tract. It constricts the bronchial tubes, irritates the mucous membranes and increases the lungs’ intake of pollutants—a dangerous synergistic effect for older adults and people with chronic obstructive pulmonary disease (COPD).

Exposure to extreme heat has skyrocketed for Canadians aged 60 and older, with “heatwave person-days” jumping 284 per cent in the last four years compared to the late 1980s. The devastating scale of this threat was evident in the 2021 heat dome in British Columbia, which claimed 619 lives.

Canadians are sneezing more and for longer. Since 1990, North American pollen seasons have lengthened by almost three weeks and pollen concentrations have increased by 21 per cent. This shift carries a heavy price tag: in Quebec, climate-related allergies are projected to cost $360 million by 2065.

Meanwhile, flooding brings another set of health risks by transforming damp indoor spaces into breeding grounds for mould—a well-documented trigger for asthma and persistent respiratory symptoms.

Vulnerable groups impacted more

The study highlights how climate risks are not shared equally across society. It is often those with the fewest resources, and therefore the least ability to protect themselves, who suffer the most severe impacts of climate change.

Indigenous populations in Canada are especially affected: while they represent five per cent of Canada’s population, they account for 42 per cent of wildfire evacuations. This is partly because their communities are often located in regions with high wildfire activity and in northern latitudes where the impacts of climate change are most pronounced. It is therefore essential that responses be co-developed with Indigenous communities, the researchers say.

Other vulnerable groups include people living with asthma or COPD, seniors, low-income households, and renters. Doiron also noted that “unlike vehicular or industrial pollution, wildfire smoke can travel long distances and significantly affect populations in rural and remote areas.”

A key role for clinicians

To combat these threats, the study maps out two clear paths for action.

The first involves personal protective measures such as wearing N95 masks during smoke events, tracking air quality alerts, and installing HEPA air purifiers, which a recent randomized controlled trial showed can cut indoor PM_2.5concentrations by 50 per cent and reduce COPD exacerbations by 70 per cent.

However, these solutions only mitigate short-term effects, the researchers say. Their study emphasizes the need to prioritize transformative measures: rapidly reducing greenhouse gas emissions, electrifying transportation, creating clean air centres, and integrating climate risks into health planning.

Clinicians have an important role to play in recognizing and treating climate-linked respiratory illnesses, and educating patients on how to protect themselves, the study notes: their expertise can help reduce vulnerability in high-risk communities and ensure our healthcare systems are ready for what’s next.

“Healthcare professionals are on the frontlines,” said Doiron. “Through their actions and foresight, they can help make our healthcare systems climate-resilient.”

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