Photo Credit: Ralf Vetterle
Scientific Frontline: Extended "At a Glance" Summary: Climate Change and Respiratory Health
The Core Concept: Climate change is progressively exacerbating respiratory diseases through the increased frequency and intensity of environmental hazards such as wildfire smoke, extreme heat, flooding, and extended pollen seasons. These compounding risks are reversing decades of air quality progress and placing immense strain on public health infrastructure.
Key Distinction/Mechanism: Unlike highly localized vehicular or industrial pollution, climate-driven air quality hazards like fine particulate matter (PM2.5) from wildfires can travel vast distances, simultaneously affecting urban centers and remote rural populations. Furthermore, extreme heat acts synergistically with these pollutants by constricting bronchial tubes and increasing the lungs' intake of hazardous air.
Major Frameworks/Components:
- Wildfire Smoke and PM2.5: A rapid rise in fine particulate matter that reverses historical air pollution reductions, leading to increased rates of chronic bronchitis, asthma exacerbations, and premature mortality.
- Thermal Exacerbation: Extreme heat exposure that actively irritates mucous membranes and constricts respiratory pathways, creating a dangerous multiplier effect for those with chronic obstructive pulmonary disease (COPD).
- Allergen Proliferation: Climate-driven lengthening of pollen seasons (increasing by nearly three weeks since 1990 in North America) and significant jumps in overall pollen concentrations.
- Flooding and Indoor Mold: Increased extreme weather and flooding events that transform damp indoor spaces into breeding grounds for mold, a recognized trigger for persistent respiratory symptoms.
- Socioeconomic Vulnerability Tracking: Analytical frameworks showing that climate risks disproportionately impact populations with fewer resources, highly affected Indigenous communities, the elderly, and low-income households.
Branch of Science: Environmental Health, Pulmonology, Epidemiology, Climatology.
Future Application: These findings guide the development of climate-resilient healthcare planning, the integration of HEPA filtration and clean air centers into urban infrastructure, and the co-development of targeted public health interventions with highly vulnerable communities.
Why It Matters: With fine particulate matter concentrations linked to wildfires projected to double by the 2050s, proactive adaptation is critical. Recognizing and mitigating climate-linked respiratory illnesses can prevent thousands of premature deaths, reduce emergency room surges, and alleviate a multi-billion dollar financial burden on healthcare systems.
Climate change is already worsening lung diseases for millions of Canadians, and health care 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 PM2.5—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 percent.
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 percent 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.
Worsened by Heat, Pollen, and Mold
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 “heat wave person-days” jumping 284 percent 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 percent. 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 mold—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 5 percent of Canada’s population, they account for 42 percent 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 PM2.5 concentrations by 50 percent and reduce COPD exacerbations by 70 percent.
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 centers, 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 health care systems are ready for what’s next.
“Health care professionals are on the front lines,” said Doiron. “Through their actions and foresight, they can help make our health care systems climate-resilient.”
Published in journal: Canadian Journal of Respiratory, Critical Care, and Sleep Medicine
Title: Breathing in a changing climate: Compounding risks to respiratory health in Canada
Authors: Dany Doiron, Jeffrey R. Brook, and Jean Bourbeau
Source/Credit: Université de Montréal | Martin LaSalle
Reference Number: env051726_01
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