Colorado Saw A Lot of Wildfires In 2020. So Which Cities Suffered Most?

If you were anywhere on the Northern Front Range last summer and fall you know the wildfire smoke was bad.  Just how bad was it?  And where was it the worst?  Grace Hood is a Scripps Environmental Journalism Fellow at CU-Boulder.  We spoke with her about her recent analysis of EPA data on the fires.

Featured image: Smoke from the Calwood Fire in Boulder

Listen to the report here:

2020 was a stressful year filled with masks and social distancing. But for Boulder County resident Caitlin Moll, the biggest source of anxiety wasn’t COVID-19. It was wildfire smoke.

“We’re used to being outside,” said the 32-year-old triathlete who has suffered from asthma since childhood. “We’re used to walking, riding mountain bikes. All of that stopped when the smoke hit. I didn’t even go outside.” 

Moll moved to Boulder four years ago. She was surprised to be wearing a N95 mask indoors in her house and generally avoid social outings this summer. The alternative, a severe asthma attack, was worth any inconvenience.

“I think about it like if you have ever used a vacuum and accidentally sucked up part of a rug. That’s how my lungs feel when this is going on. It’s constricting and there’s no going back,” she said.

An analysis of Environmental Protection Agency data shows Boulder County residents were among those who suffered most from wildfire smoke. The Calwood Fire along with smoke from the Cameron Peak Fire hit residents hard in Boulder. All told, they saw 13 days during which smoke levels exceeded the EPA’s Air Quality Index of 100 for hours, considered unhealthy. Fort Collins came in a close second with 12 smoke-filled days where the AQI exceeded 100.

“A lot of that smoke from the Cameron Peak wildfire at night would drain right down into the Fort Collins area,” said Scott Landes, chief meteorologist for the Colorado Department of Public Health and Environment. “So we started seeing high values [of particulates] in the mornings where you have an inversion in place and all the smoke gets trapped near the surface of the earth.”  

Wildfire smoke carries fine particulate matter. The tiny specs of ash get measured by the EPA and other devices as PM2.5, tiny inhalable particulates that are 2.5 micrometers or smaller. Landes said the number of Denver sites on 2020 list of bad wildfire smoke days isn’t that surprising because it’s a function of wildfires situated close to the Front Range combined with strong wind. 

What stands out are the missing locations. For example, the Pine Gulch fire scorched nearly 140,000 acres in Mesa and Garfield counties, but there are fewer long-term EPA monitoring sites in Western Colorado. 

“Western parts of the state just don’t have the monitor coverage that we have here on the Front Range,” Landes said. “In a normal sequence of days we won’t see big air pollution problems in these areas because of the lack of population. But during a wildfire event that all changes.”

To fill the data gap, CDPHE purchased 20 low-cost PurpleAir sensors this summer with plans to buy another 20 monitors in 2021. The $200 monitors can cheaply measure particulates. State health officials positioned them in Gunnison, Silverton, Montrose and Ridgeway to aid in issuing air quality alerts. 

 In addition to being cheaper, the monitors offer real time data. But they’re not as accurate as EPA monitors that can cost thousands of dollars. Landes said they can overestimate wildfire smoke particulates when smoke levels are high. EPA officials have come up with a mathematical estimate to correct it. It’s used by CDPHE officials when they forecast air quality, and when EPA officials began pulling PurpleAir data into its Fire and Smoke map.   

Colleen Reid, assistant professor of geographer at the University of Colorado-Boulder, has kept a close eye on the use of low-cost sensors. She tracks the multifaceted health impacts from wildfire smoke and knows with climate change they will grow worse in the West.

“There’s a lot of variability in our systems. If 2021 turns out to be a great year and we don’t have any fires, that’s fantastic,” said Reid. “But we’re on a trend of this changing climate. We will see large parts of the West burning.”

Reid and others in the academic community are ramping up research to study the impact of wildfire smoke on humans. A lot is known on the negative health effects of fire smoke on cardiovascular and respiratory health, she said. But more research needs to be done on how the smoke might impact pregnant mothers, newborns and even contribute to things like cognitive decline.

“Most of our research is on acute health impacts. We need to try to follow people over time so we can say what the long-term health impacts are,” she said. 

Reid notes that it’s not just fire smoke that causes breathing problems. Ground-level ozone can also exacerbate health issues. In 2019, EPA officials downgraded parts of the Denver metro region as out of compliance with federal regulations. 

Keeping a watchful eye on both smoke and ozone in 2020 were local government workers like Bill Hayes, air quality coordinator for Boulder County. Hayes notes that federal and state messaging around COVID-19 rightly issued guidance to people telling them to socialize outdoors to reduce the spread of the virus. But on bad air quality days, local health officials asked residents to stay indoors.

“When you’ve got two different government bodies telling people completely different messages, for a lot of the public the reaction is, ‘They don’t know what they’re talking about so I’m not going to listen to any of it,’ Said Hayes. “That was a big challenge of not frustrating people with too many conflicting messages.”

Hayes spent a lot of time talking specifically to schools and other places where larger groups of people were gathered. He issued guidance on how to best update air filtration by maximizing the return of fresh air from HVAC systems. For individual homeowners, the focus was on the purchase of HEPA filters and to avoid the purchase of ionizing filters because some can produce ozone and make breathing worse. 

“Any device that’s labeled as ionizing I view with a great deal of skepticism,” said Hayes.


If HEPA filters aren’t available, Hayes said some ionizing filters can be ok so look for ones certified by Underwriters Laboratories. In general, winter is a good time to stock up on an air filter, not the middle of wildfire season.

As Boulder County plans for the 2021 wildfire season and beyond, Hayes said officials will be looking toward establishing fresh air centers–something that was not tenable due to the COVID-19 pandemic in 2020.

“It doesn’t need to be anything extraordinary. Movie theaters can be a good place to do that,” said Hayes. “They typically have good HVAC systems, and in the deep south they’re already used frequently for cooling stations.” 

But next year you probably won’t see Boulder County resident Caitlin Moll at a fresh air station. That’s because after four years of bad Boulder air quality, she’s eyeing a move outside of the state.

“I started hearing the term ‘climate refugees’ four years ago when we moved here,” she said. “I don’t want to undermine refugees and things people are escaping, [but] I came to realize this year we might consider ourselves in that category.”

Finding a new home will be a challenge for Moll, who hopes to raise kids one day. If she says in Boulder, she worries about them stuck indoors each and every summer. 

“It’s not just the wildfire smoke, it’s the ozone levels that are a concern every year,” said Moll, who struggled to breathe in 2019 during a bad ozone day that coincided with a triathlon. “We’re not seeing the trend get better. We’re seeing the trend get worse since we moved here.”