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Why wildfire smoke can be worse than other air pollutants

Why wildfire smoke can be worse than other air pollutants


There’s still a lot to learn about wildfire smoke

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A haze of wildfire smoke and clouds is seen at sunset in an aerial image taken during a flight from Seattle to Los Angeles as Western wildfires, including the Bootleg, Dixie, and Tamarack fires, continue to burn in Oregon and California.
Photo by Patrick T. Fallon / AFP via Getty Images

The explosive growth of wildfires in the Western US has spewed smoke across the landscape, creating a growing threat to public health. Driven by climate change, the 2020 fire season was so bad that it doubled the previous record in California for acres burned, and at-home monitoring of the smoke’s effects on air quality became almost commonplace. This year’s season got off to a devastating start and has already darkened skies on the East Coast with smoke from West Coast wildfires.

Smoke isn’t your ordinary air pollution. The tiny particles found in smoke can be up to 10 times more harmful to human health than soot from other things like tailpipes and factories, according to research published in the journal Nature earlier this year.

Tiny particles found in smoke can be up to 10 times more harmful to human health

The researchers looked at fine particles, also called PM2.5, that are 30 times smaller than the diameter of a human hair follicle. When a fuel burns, whether it’s gas or vegetation, it sends these fine particles up into the air and sometimes into our bodies. Fine particles from wildfire smoke led to 10 percent more respiratory hospitalizations than there would be without the smoke, the study found. Pollution from other sources, while still harmful, increased hospitalizations by just around 1 percent.

The Verge spoke with Rosana Aguilera, the lead author of that study and a postdoctoral researcher at the University of California, San Diego. She walked us through what she and other researchers are doing to better understand what wildfire smoke means for our health.

This interview has been lightly edited for clarity.

What are “fine particles,” and why are we worried about them? 

The research group I work in studied the fine particles because it’s one of the main components of wildfire smoke. These particles are unique. Their chemical composition can vary in relation to the materials that are burning. There’s a myriad of potential compounds that can be present in wildfire smoke and fine particles like carbon, heavy metals. 

“Wildfire smoke as a source of emissions is becoming more predominant”

We are focusing now on these fine particles that are found in wildfire smoke because, in some regions in the US and in the world, wildfire smoke as a source of emissions is becoming more predominant. Here in California, it’s definitely one source of air pollution that seems like it’s going to be increasing in the near future. There are some publications that support the idea that wildfire smoke will be one of the main sources of fine particulate matter in regions like the Western US, for example. 

What effect can those fine particles have on human health?

It’s one of the air pollutants of concern because it’s small enough to penetrate our respiratory system and go deep into the lungs. It potentially also enters the bloodstream and from there, can travel to other organs. It can cause difficulty breathing. It can produce irritation and exacerbate conditions like asthma and other respiratory diseases and cardiopulmonary conditions. 

We deal mainly with acute effects, the response that we get after you’re exposed to wildfire smoke for some days. My research group is not specifically looking at long-term effects at this point, but I think it’s an area of research that needs to be expanded. It’s a bit more complicated to look at long-term exposure because you have to follow individuals who are exposed to multiple wildfires. 

So how does wildfire smoke compare to air pollution from other sources like cars, trucks, and industry? 

We found that wildfire smoke can be more harmful in terms of an increase of hospitalizations when compared to just looking at non-smoke fine particles. 

“Traffic emissions might be very different in composition from wildfire smoke”

Traffic emissions might be very different in composition from wildfire smoke. We haven’t really looked at the chemical composition of these fine particles with respect to their sources. But some toxicological studies have looked into more detail into that, and they find that the toxicity of wildfire smoke might be increased. If it goes through a structure, then it might pick up some chemicals found in houses and other buildings.

What impact do you hope your research will have? 

We want to start looking more into these differential impacts of fine particles with respect to the sources of emissions and also try to look for some more of the chemical composition of different wildfires as well.

If there’s a greater impact for wildfire smoke, and if wildfire smoke is going to be one of the main sources of this type of pollution in the future — or if it is already — we need to better understand why is it more harmful? And then what impact can we expect in the long term?