As thick layers of smoke descended from hundreds of Canadian wildfires over a large swath of the United States this week, millions were urged to stay indoors, use HEPA filters and only wear high-quality face coverings when outside to be done. Wildfire smoke, a seasonal hazard in some parts of the United States, had become a problem for everyone virtually overnight.
“It’s a risk to our health,” says Christine Wiedenmeyer, associate director of science at the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences. “It’s everything, from effects on the respiratory system, such as asthma, to the cardiovascular system. There is evidence that newborns of women exposed to wildfire smoke during pregnancy have a statistically lower birth rate.” it occurs.”
In many North American cities, some level of air pollution is routine, whether from fossil fuels, vehicle emissions, natural gas used for heating, or fumes from chemical production. But smoke from wildfires is particularly bad for humans, and has as much to do with the size of the particles involved as it does the composition of the particles.
“Wildfire smoke, especially long-lasting smoke, is made up of very small particles,” says Luke Montrose, an assistant professor and environmental toxicologist at Colorado State. “That’s what gives it the ability to be ephemeral.”
Because the particles in wildfire smoke are tiny—much smaller than the tiniest grain of sand—they have little trouble passing through the guardrails set up by our bodies to keep pollutants out. Smoke particles can pass through the hairs of the nose and through the mucous membranes that line the upper respiratory tract.
The smallest particles, known as PM2.5, can also cross mucous membranes and reach the lower respiratory tract. The job of that airway is to “transfer oxygen to the lungs across the blood barrier,” Montrose said, making this type of pollution especially devastating for people who already have lung conditions like asthma or COPD. Even people with healthy lungs effectively get less oxygen, and those effects are not always indicated by a visible symptom such as a cough.
“People who may not be sensitized often have other symptoms like lethargy,” Montrose said. “They may just feel bad, be giddy, or have no energy. And this can be attributed to the lack of oxygen in the body.”
This lack of oxygen is also the reason that people who are experiencing poor air quality, especially outdoors, are discouraged from exercising. More activity means heavier, faster breathing, which brings more particles into the body and pushes them deeper into the lungs, ironically inhibiting the body’s ability to absorb oxygen when it is needed most. does. The effects can also be long lasting. A 2020 study looked at a community in Montana that was exposed to wildfire smoke for more than a month; One year later, the residents were still suffering from decreased lung function.
Wildfire smoke also contains thousands of compounds, some of them potentially toxic, such as volatile organic compounds, hydrocarbons and oxides of nitrogen. A 2022 study published in The Lancet Planetary Health journal looked at the effects of wildfire smoke on Canadians, finding that those who lived within 30 miles of a wildfire had a 4.9% increased risk of breast cancer There was a 10% higher risk of lung and brain damage. cancer compared to the unaffected population.
The dangers of wildfire smoke don’t go away as it travels either: Smoke released into the atmosphere becomes “old” and more toxic over time. A 2020 study found that smoke samples taken more than five hours after a fire was released were twice as toxic as those taken when first released; After further aging in a lab, they were four times as toxic.
“The smoke that’s traveled that far has had time to interact with the chemicals in the air, has had time to interact with the sun,” says Montrose.
This week’s fires are just the beginning of what could be a smoky summer in North America, and a new normal of sorts thanks to climate change. “It gets progressively worse in terms of fire severity, length of fire season and amount of smoke released into the air,” says Wiedenmayer of the University of Colorado Boulder. “But there are ways to protect yourself. Stay inside, turn on your air conditioner when it’s smoky, wear a mask outside[and]avoid exercising so you’re not breathing in these particles for a long time.”