It's been a busy fire season in the Mountain West, especially on Colorado's Western Slope. The Lee Fire, currently burning in the northwest part of the state, is the fifth-largest in Colorado's history. It's burned over 120,000 acres as of August 13.
Throughout the summer, communities throughout the region have experienced poor air quality due to traveling smoke from big fires like Lee, as well as the South Rim Fire near Montrose, and the Turner Gulch Fire in Mesa County.
Rocky Mountain Community Radio's Caroline Llanes spoke with Joost de Gouw, a chemistry professor at the University of Colorado, Boulder, who studies atmospheric chemistry, to find out more about how wildfire smoke impacts public health.
Editor's note: this interview has been edited for length and clarity.
Caroline Llanes: Well, I think it's pretty common knowledge that air pollution is bad. But what is it about wildfire smoke that's uniquely harmful, or maybe how is that harm different from other forms of air pollution?
Joost de Gouw: Yeah, so one of the most important air pollutants, is really what we call PM2.5 fine particles. Some people call it aerosols. But what it is is fine particles in the air that are suspended in the air and can stay airborne for weeks. And they're especially harmful to us because they're so small. They can penetrate really deep into your lungs when you breathe them in. So when they contain toxic material, then that's a great way to deposit that toxic material into your body. And as it turns out, wildfire smoke has a lot of fine particles, much more so than vehicles which are tightly controlled, and other sources that we have in urban air. So yeah, wildfires are really rich in fine particles and therefore extra harmful.
Llanes: So when we're looking at some of the health impacts, do we see any sorts of things with wildfire smoke that are different from other forms of air pollution?
de Gouw: Yeah, so one thing that's really unique about wildfires is the episodic nature, right? We get smoke and then it clears out and, and that's different from urban air pollutants, which (are) more there all the time. So research has shown that when smoke hits an area, for instance, the sales of asthma inhalers goes up. And so you can see that immediate effect because of the episodic nature of wildfires. So from that, we know, wildfires are bad for your respiratory system, also your cardiovascular system. There are some other diseases that have been linked to wildfire smoke, but that research is more in its preliminary stages, I would say.
Llanes: As I'm sure you know, this summer in western Colorado, we have had a lot of wildfire smoke and a lot of times from fires that are pretty far away. Can you talk a little bit about how some of those health impacts from wildfire smoke change as we move further away from the fire itself?
de Gouw: Very good question. So smoke is not just the fine particles that I talked about. It's also a number of gases. And those gases are reactive, and so once the smoke's released in the atmosphere, those gases will react. You know, some of the toxics will actually go away with time. That's good. But then other compounds can be formed, and one of the things we worry about is ozone. So a wildfire plume from far away can contain some ozone and actually raise ozone levels in cities. So that is an effect that is true for fire plumes that have been transported for days or even longer. Defined particles, they stay in these plumes, and they're only slow to be removed. There can be some dilution, obviously the smoke is not as thick, when you're days downwind. But still, the particles stay and they don't change their toxicity by a whole lot.
Llanes: Human-caused climate change has a big impact on various aspects of wildfire behavior, including the smoke. How are some of the impacts of climate change informing the research questions that you and your colleagues are asking about wildfire smoke?
de Gouw: Yeah, so a big concern is that wildfires are offsetting a lot of the progress that we've made to improving air quality in the U.S. So if you look over the past few decades, due to the Clean Air Act, there has been a lot of progress in improving our air quality. But now, especially in the West, because of the wildfires, some of that progress is basically getting undone. You know, we're now seeing an uptick in PM2.5 again, and we're seeing a reduction in visibility where, for years, that was getting better. So that's a major concern.
Some other areas that we're working on have to do with these urban fires. So we had the Marshall Fire in Boulder County. We had the fires in Los Angeles in January of this year. And in both cases, it was wildfires that really quickly turned into urban fires. And so what was getting burned was homes and cars and not so much vegetation. As it turns out, we know really far less about the toxics you get when you burn homes and cars. And so a lot of our research is now devoted to that particular issue. As you can imagine, if you burn plastics, you get very different things than when you burn a shrub or a grass or a tree. So what we're finding is that the toxics are actually more abundant when you burn plastics, roofing material, furniture, things like that. So that's an area of active research for us right now.
Llanes: That was Dr. Joost de Gouw. He is a professor at CU Boulder who researches atmospheric chemistry and wildfire smoke. Dr. de Gouw, thank you so much for speaking with Rocky Mountain Community Radio.
de Gouw: Thank you for having me. It was a pleasure.
Copyright 2025 Rocky Mountain Community Radio. This story was shared via Rocky Mountain Community Radio, a network of public media stations in Colorado, Wyoming, Utah, and New Mexico, including KSJD.
