‘Wildfire smoke is the fastest-growing environmental threat in the US’: How a warming world will poison the air we breathe

August 28, 2026 thedigitalsolutioncentre@gmail.com

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A 2025 study found that the record-breaking 2023 Canadian wildfire season may have shortened the lives of 87,000 people exposed to the smoke plumes worldwide. Another 2025 study found that wildfire smoke contributed to 41,380 excess deaths per year in the U.S. between 2011 and 2020 and that the number will rise to 71,420 excess deaths by 2050 if global temperatures rise 5 to 8.3 degrees Fahrenheit (2.8 to 4.6 degrees Celsius) by the end of the century.

In the U.S., the picture is bleak. Between 1984 and 2015, the number of large wildfires in the U.S. West doubled, according to the National Oceanic and Atmospheric Administration (NOAA). The seasonality of fire is also shifting. A February 2026 study published in the journal Geophysical Research Letters found that climate change is nudging fire season in the boreal forests of Alaska and Canada forward as winter snow vanishes earlier, leaving spring vegetation dry and ripe to burn. In the U.S. West, on the other hand, fire season is stretching later because of summer drought.

Zhang and his colleagues found that under a scenario in which temperatures rise by about 7.9 F (4.4 C) by 2100 — a high-emission scenario in which we do little to curb carbon output — fire season would move forward by about a week in Canadian and Alaskan forests, with some of the northernmost regions of Canada and Alaska seeing shifts of up to 23 days. California, with its Mediterranean-like climate, would experience a peak burning shift later in the season. In the Southwest, fire season under this scenario would start a week later but end more than a month later than it does now.

air pollution. For instance, a 2020 study suggests that particulate smoke pollution levels will double or triple in the Pacific Northwest and Northern California under unmitigated warming by the end of the century. And even though the West is the U.S. region most prone to fire, wildfire smoke pollution won’t stay there. Instead, it will travel across the country, worsening air quality on the East Coast and in the Midwest, Burke and his colleagues found. Depending on the level of warming, smoke emissions will increase 262% to 482% between 2046 and 2055 compared to 2011 to 2020, the researchers found.

When wildlands burn, they produce PM2.5, a fine particulate matter that is small enough to slip into the bloodstream. Epidemiological studies have linked exposure to PM2.5 to a range of health issues, including dementia, kidney disease and lung cancer. The particles increase oxidative stress on cells in lab dishes, induce cell death, and cause DNA damage that can lead to cancerous mutations, among other impacts.

The damage is evident during big fires. For instance, exposure to wildfire smoke raises the risk of heart attack, stroke and other cardiovascular emergencies, according to a study of California emergency department visits during the 2015 wildfire season. Cumulative exposure over time, however, is how wildfire smoke causes the most deaths. Between 2006 and 2020, PM2.5 from wildfire smoke exposure was responsible for an average of 24,100 deaths per year in the United States, a study published in the journal Science Advances in February found. Smoke exposure worsened the death rate for every health condition studied, with neurological disease deaths rising most significantly.

Wildfire smoke may also fuel premature births. Just a week of wildfire smoke exposure raised the risk of preterm birth by 3.4%, a 2022 study found — and in a world where smoke exposure could span weeks, that could translate to a significant uptick in the rate of premature birth. Other studies tell a similar story: a 2024 study found risk of premature birth rises with every incremental increase in exposure to PM2.5 from wildfires during pregnancy. And a 2025 study found that preterm birth risk increased in the U.S. West with smoke exposure, regardless of whether that exposure was measured by high-smoke days, exposure to 4-day waves of smoke, or by the concentration of particulate matter in the air.

Wildfire smoke may also affect cognition: A 2022 study found that cumulative exposure to wildfire smoke over the school year was linked to slightly lower test scores for elementary and middle schoolers. And research using data from cognitive brain-training apps has also shown that performance on a cognitive task declines on high smoke days in adults. Over the long term, PM2.5 exposure from wildfires is linked to dementia risk.

Johnson and her team have found that smoke exposure leads to epigenetic changes associated with the immune system.‪‬ In other words, the person’s DNA doesn’t change, but the way it’s translated into building proteins and cells in the immune system shifts. And epigenetic shifts can be passed along to the next generation. One shift is a decline in regulatory T cells, immune cells that help the body tolerate itself and harmless allergens. The immune changes probably play a role in why wildfire smoke exacerbates chronic diseases, Johnson said.

More smoke days can also affect health indirectly, by keeping people from going outdoors. In California, the heaviest smoke days actually have fewer emergency department visits overall, Burke said. On the smokiest days, when the air is noticeably hazy and may even smell like a campfire, emergency department visits for asthma-related reasons rise, but visits related to injuries or car accidents decline even more, probably because everyone is staying home. That may sound like a net benefit, but if forced quarantines happen repeatedly, they can worsen physical and mental health over time, making people more sedentary or less able to socialize.

With an increasingly wildfire-friendly climate in its future, Americans will be less healthy. There are ways to reduce the impact, however. Burke and his team have found that controlled burns put off less pollution than wildfires, while reducing the fuel load that turns wildland fires into smoke-churning infernos. An investment in managing fuels could ultimately be an investment in improving the country’s health.

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The Digital Solution Centre

The Digital Solution Centre

‘Wildfire smoke is the fastest-growing environmental threat in the US’: How a warming world will poison the air we breathe

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