On December 30, 2021, one of the most destructive wildfires on record in Colorado swept through neighborhoods within miles of our offices at the University of Colorado Boulder. The flames destroyed more than 1,000 buildings, but when we walked through the affected neighborhoods, some houses were still completely intact, right next to dwellings where there was nothing left to burn.
Although the people who lived in these still standing houses were spared the loss of everything they owned, when they returned after the fire they found another disaster.
The noxious smells and ash on their window sills and doors initially made their homes unlivable – and potentially dangerous to human health. Some of these residents were still reporting health issues from being in their homes months later, even after the homes had been cleaned.
We studied wildfires and their health effects, and we knew people who lost their homes in the Marshall fire. We also knew we had to act quickly to study the impact of the fire so that lessons learned from the Marshall fire can help homeowners elsewhere avoid similar risks in the future.
This article is part of a collaboration with Boulder Reporting Lab, the Center for Environmental Journalism at the University of Colorado at Boulder, KUNC Public Radio, and The Conversation US to explore the impacts of the devastating Marshall Fire one year after the ‘fire. The series can be found at the Boulder Reporting Lab.
Hazardous chemicals absorbed in homes
Early on, due to our air quality and health expertise, members of our community contacted us asking how they could remove hidden odors and ashes from their homes and what health risks should concern them.
But this fire had nothing to do with the wildfires that our research groups at the University of Colorado had previously studied. Most of what burned that day was of human origin rather than vegetation. When man-made materials like electronics, vehicles, and household furniture burn, they release different types of air pollutants and can affect health differently than burning vegetation.
Outdoor air pollution was less of an issue as the wildfire was short-lived – the powerful winds that fueled the fire died down and changed direction about 11 hours after the blaze started, and the first snow of the season has finally fallen. This snowfall put an end to the fire and cleaned the outside air of pollution.
The main concern was what chemicals lingered inside undestroyed homes – absorbed into the fabrics of carpets, sofas, drywall, air vents, etc. – which would slowly release into the house for some time after the fire.
We hypothesized that there were a lot of volatile organic compounds (VOCs) – toxic gases, which were emitted during the fire which had seeped into the houses and embedded themselves in fabrics and construction materials. Aromatic compounds like benzene, a known carcinogen, and polycyclic aromatic hydrocarbons (PAHs), which are emitted by wildfires and have known health effects, were of particular concern. In addition, we were concerned about the metals in the ashes and soot deposited in the houses and the possibility of them becoming airborne when people returned and the heating systems turned on.
Although we knew some of these gases were toxic, we did not know the levels inside homes or what remediation efforts to offer residents, as little scientific research had been published on forest- interface fires. urban like this. We realized that we needed to do some of this research to help our own community – and the next community affected by a fire at the interface between the forest and the city.
Collect evidence inside
Many community members offered their homes for study sites. When we visited these houses still standing ten days after the fire, we saw what a quick evacuation looks like, with lunch being prepared, laundry being folded, toys in the middle of a simulation game… and dust, lots and lots of dust from the fire.
We collected dust samples from a dozen homes and then analyzed the samples in our labs.
We looked for molecules that could help us think about the origin of dust. Unsurprisingly, the dust was a combination of windblown dirt, ashes from the fire, and typical household dust. These ashes were rich in typical combustion by-products known to be toxic, and there was a lot of ash, so cleaning up any dust was important for sanitation.
Homes that had been exposed to heavy smoke still smelled of chemical fire. A colleague compared it to the smell of gunpowder.
As fast as we could, we moved a state-of-the-art mass spectrometer to one of Superior’s worst-hit homes and measured air pollutants for five weeks.
Shortly after the Marshall fire, we found that many pollutants, including PAHs, were indeed at higher levels inside smoke-affected homes than we expected, but by early February, these pollutants had declined to more normal levels.
We researched ways to protect people and found through experimentation that activated carbon air filters could provide excellent temporary relief from indoor pollutants.
We also observed the results of professional remediation efforts. We are always looking at air pollution data to understand which materials that have burned, such as plastics, car tires, furniture, carpets and roofing materials, have contributed the most to the air pollutants we observed in the houses.
Ongoing health effects
In addition to air pollution and ash issues, residents of burning neighborhoods are concerned about their health.
When initially surveyed, residents reported a variety of symptoms they thought were due to smoke or air quality issues from the fire, the most common being itchy or watery eyes, headaches, dry cough and sore throat. More than half of respondents also reported trouble sleeping due to the stress of the fire, and almost a quarter attributed headaches at least in part to the stress of the event.
Physical symptoms could be due to exposure during the fire. However, among those who have returned to smoke-damaged homes, they most often report the symptoms inside their homes.
This fall, more than nine months after the fire, some residents reported skin rashes and burning sensations despite cleaning their homes of ashes and the smell of VOCs having dissipated. Another round of surveys is now helping to gather more information about persistent symptoms. In addition to physical health symptoms, we also ask about mental health, which is a growing concern of so-called natural disasters.
Although we know that the indoor VOC concentrations in the homes we have worked in have returned to normal levels, some people may be more sensitive than others. And while there has been research into the health effects of certain VOCs, not all of them have been thoroughly studied, and no studies have looked at the health effects of combinations of VOCs.
As global temperatures rise and more people move into once wild landscapes on the outskirts of cities, the risk of wildfires spreading through urban areas increases. We hope our work can help people cope with the air pollution consequences of future fires.
This article was originally published on The conversation by Colleen E. Reid, Joost de Gouw and Michael Hannigan at the University of Colorado at Boulder. Read the original article here.
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