‘I couldn’t breathe’: the deadly health burden of wildfire smoke

Smoke from Distant Fires Claims Millions of Lives Worldwide

Wanderstayfinder.com – As climate change intensifies fire seasons across continents, scientists are racing to understand how wildfire smoke affects human health far beyond the flames themselves. The invisible threat has become one of the deadliest environmental hazards on Earth, claiming more lives annually than floods, storms, and extreme heat combined.

Erin O’Connor stood outside Toronto General hospital and felt the weight of the crisis firsthand. The sky above Canada’s largest city had transformed into an almost post-apocalyptic orange, filled with particles of soot and ash that scattered light in every direction. The smell was unmistakable—like standing beside a roaring campfire, only this one stretched across thousands of kilometres of burning boreal forest in northern Ontario.

It really hit you in the face as soon as you walked outside. As the days progressed, it was like that everywhere. It seemed even inside you could smell that burning.

O’Connor, who directs the emergency department at University Health Network, noticed something troubling. Patients were arriving with allergies and difficulty breathing in greater numbers than usual. The smoke was not merely an inconvenience; it was a medical emergency unfolding in real time.

The numbers tell a staggering story. A 2024 study published in the Lancet revealed that landscape fires kill approximately 1.5 million people each year worldwide. These deaths occur not only among those caught in the flames but also among populations thousands of kilometres away, where toxic gases inflame airways and microscopic particulates penetrate deep into lungs, traveling through the bloodstream to damage every organ in the body.

The reach of wildfire smoke extends across borders with remarkable efficiency. In 2023, Canadian wildfires generated 82,000 premature deaths according to research published in Nature. Unfavourable wind patterns carried a third of this mortality burden into the United States and another quarter into European nations. Researchers discovered in March that roughly ten percent of the United Kingdom’s fine particulate pollution originates from biomass burned in foreign countries.

Unanswered Questions in a Warming World

While the scale of the problem is clear, the scientific community is only beginning to map the complex relationships between smoke exposure and mortality. Climate breakdown is making fire weather more severe, raising critical questions that current research cannot fully answer.

What happens when hotter fires push pollution levels to even more extreme heights? What if contaminated air persists for days or weeks rather than hours? What if a severe smoke episode strikes before a person has recovered from the previous one? These gaps in knowledge make it difficult to predict the full impact of increasingly furious fire seasons.

Early indicators are concerning. Vast areas of vegetation near major European cities have been consumed by flames. In North America, a late but explosive start to the fire season sent smoke choking into population centres including Chicago and New York City. Toronto briefly held the distinction of having the worst air quality among major global cities, a title later claimed by Portland, Oregon.

I had never looked outside and had the sky seem orange in the middle of the day. Certainly, we have had other wildfire smoke, but in more of a transient way.

O’Connor recalled rushing to retrieve her son from summer camp as conditions deteriorated rapidly. The pollution arrived suddenly and lingered longer than expected, unlike previous episodes that passed more quickly.

Wind Patterns Dictate the Human Toll

Perhaps surprisingly, the death toll from any given fire season depends as much on wind direction as on the size of the blazes themselves. France released record pollution levels during the first half of the year, while Spain’s emissions approached their historical worst. Yet monster fires that threatened to engulf Madrid and Bordeaux were largely contained because prevailing winds carried smoke away from populated areas.

Even so, daily particulate levels worsened across southern Europe. Bordeaux recorded 342 micrograms of PM2.5 per cubic metre on July 24, while Limoges, located 180 kilometres away, reached 486 μg/m³ the following day. These figures far exceed the World Health Organization’s recommended limit of 25 μg/m³ for 24-hour exposure, though many residents remained unaware of the danger.

North America faced a different challenge. Winds blowing south and southeast from sparsely populated forests in Ontario and the Northwest Territories carried pollution toward millions of people. Preliminary analysis conducted for The Guardian shows that at least 36 million people across the continent breathed air classified as very unhealthy, with PM2.5 concentrations exceeding 125.5 μg/m³ on July 16 alone. At least 10 million individuals were exposed to levels above 250 μg/m³, a threshold that triggers health warnings for sensitive groups and can cause respiratory distress even in healthy individuals.

As fire seasons grow longer and more intense, the question is no longer whether smoke will affect millions of people—it is how severely, and for how long, we must prepare for the invisible threat that continues to reshape public health challenges worldwide.