Wildfire smoke’s health risks can linger in homes that escape burning—as Colorado’s Marshall Fire survivors discovered

On Dec. 30, 2021, a raced through two communities just outside Boulder, Colorado. In the span of about eight hours, and businesses burned.

The fire left entire blocks in ash, but among them, , seemingly untouched. The owners of these homes may have felt relief at first. But fire damage can be deceiving, as many soon discovered.

When wildfires like the Marshall Fire reach the , they are burning both vegetation and human-made materials. Vehicles and buildings burn, along with all of the things inside them—electronics, paint, plastics, furniture.

Research shows that when human-made materials like these burn, from what is emitted when just vegetation burns. The smoke and ash can blow under doors and around windows in nearby homes, bringing in chemicals that stick to walls and other indoor surfaces and continue off-gassing for weeks to months, particularly in warmer temperatures.

In a , my colleagues and I looked at the health effects people experienced when they returned to still-standing homes. We also created a in the future to help them protect their health and reduce their risks when they return to smoke-damaged homes.

Tests in homes found elevated metals and VOCs

In the days after the Marshall Fire, residents quickly reached out to nearby scientists who study wildfire smoke and health risks at the University of Colorado Boulder and area labs. People wanted to know what was in the ash and .

In homes we were able to test, my colleagues found . We also found elevated VOCs – volatile organic compounds – in airborne samples. Some VOCs, such as , , and , can be toxic to humans. Benzene is a .

People wanted to know whether the chemicals that got into their homes that day could harm their health.

At the time, we could find no information about physical health implications for people who have returned to smoke-damaged homes after a wildfire. To look for patterns, we affected by the fire six months, one year and two years afterward.

Symptoms six months after the fire

Even six months after the fire, we found that that aligned with health risks related to smoke and ash from fires.

More than half (55%) of the people who responded to our survey reported that they were experiencing at least one symptom six months after the blaze that they attributed to the Marshall Fire. The most common symptoms reported were itchy or watery eyes (33%), headache (30%), dry cough (27%), sneezing (26%) and sore throat (23%).

All of these symptoms, as well as having a strange taste in one’s mouth, were associated with people reporting that their home smelled differently when they returned to it one week after the fire.

Many survey respondents said that the smells decreased over time. Most attributed the improvement in smell to the passage of time, cleaning surfaces and air ducts, replacing furnace filters, and removing carpet, textiles and furniture from the home. Despite this, many still had symptoms.

We found that living near a large number of burned structures was associated with these health symptoms. For every 10 additional destroyed buildings within 820 feet (250 meters) of a person’s home, there was a 21% increase in headaches and a 26% increase in having a strange taste in their mouth.

These symptoms align with what could be expected from exposure to the chemicals that we found in the ash and measured in the air inside the few in depth.

Lingering symptoms and questions

There are a still a lot of unanswered questions about the health risks from smoke- and ash-damaged homes.

For example, we don’t yet know what long-term health implications might look like for people living with lingering gases from wildfire smoke and ash in a home.

We found a significant reporting symptoms one year after the fire. However, 33% percent of the people whose homes were affected still reported at least one symptom that they attributed to the fire. About the same percentage also reported at least one symptom two years after the fire.

We also could not measure the level of VOCs or metals that each person was exposed to. But we do think that reports of a change in the smell of a person’s home one week after the fire demonstrates the likely presence of VOCs in the home. That has health implications for people whose homes are exposed to smoke or ash from a wildfire.

Tips to protect yourself after future wildfires

Wildfires are as the wildland-urban interface, and fire seasons lengthen.

It can be confusing to know what to do if your home is one that survives a wildfire nearby. To help, my colleagues and I put together a if your home is ever infiltrated by smoke or ash from a wildfire.

Here are a few of those steps:

• When you’re ready to clean your home, start by protecting yourself. Wear at least an N95 (or KN95) mask and gloves, goggles and clothing that covers your skin.
• Vacuum floors, drapes and furniture. But avoid harsh chemical cleaners because they can react with the chemicals in the ash.
• Clean your HVAC filter and ducts to avoid spreading ash further. Portable air cleaners with carbon filters can help remove VOCs.

documents how within a home can reduce reservoirs of VOCs and lower indoor air concentrations of VOCs.

Given that we don’t know much yet about the health harms of smoke- and ash-damaged homes, it is important to take care in how you clean so you can do the most to protect your health.

Colleen E. Reid is an associate professor in the  Department of Geography.

This article is republished from  under a Creative Commons license. Read the .

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After interviewing hundreds of participants, our survey shows support for Nato is at an all-time high

When Vladimir Putin sent his war machine into Ukraine last February, one of the reasons he gave for the invasion was to and prevent its government from moving the country further towards the west. Though there is , the Russian leader has long expressed concerns about the possibility of Ukraine seeking closer military cooperation with Nato, with an eye to eventually joining the alliance. The “special military operation” aimed to stop this in its tracks.

But ten months of bloody warfare has had the reverse effect. There is now a larger Nato military footprint in Ukraine than ever before. Military support – from medical equipment to training and advanced weaponry – has (£16.8 billion) from Washington alone.

This – and Russia’s inability to topple the Ukrainian government in the early days of the war – are widely accepted to be major strategic blunders by Russia. Putin overestimated the extent of Russia’s support among the Ukrainian people and underestimated the strength of Ukrainian . But how has the war affected attitudes toward neutrality and Nato among ordinary Ukrainians?

Our survey data tracing the attitudes of the same people prior to and after the invasion shows that Ukrainians who previously saw their future oriented towards Russia are now increasingly looking west. Support for Nato membership is at an all-time high, and Ukrainians who previously favoured neutrality no longer do so. These trends are particularly stark among younger respondents.

In 2019-2020, we conducted a set of nationally representative public opinion surveys across several of the states in Russia’s “near abroad”. Given that the Russian government has long used soft power mechanisms (such as pro-Russian social media and television, the church and civil society) to try to convince citizens in these countries that they are part of the “Russian world”, we wanted to assess the geopolitical orientations of ordinary people.

When we designed the project in 2017, we planned to conduct two rounds of surveys to chart whether and how geopolitical changes affected people’s views over time. In cooperation with the , we conducted the first survey in Ukraine in (funded by the US National Science Foundation), and in October 2022 conducted a follow-up survey (funded by the Norwegian Research Council).

Due to the war, the follow-up survey was done by phone rather than face to face. We were able to re-interview almost 20% of those respondents interviewed in 2019. To allow for a representative sample also in 2022, we then used random sampling to top up the sample.

Collecting public opinion is especially challenging in a . While our surveys present a unique opportunity to analyse how Russia’s war in Ukraine has shifted public opinion, there are at least two challenges that call for caution.

First, the 20% that we resurveyed may be systematically different from the 80% that we could not resurvey. Those 80% are likely part of the historic numbers of people who have been forcibly displaced within Ukraine or have fled abroad. Equally, many respondents interviewed in 2019 may have joined the Ukrainian military and so did not take part in the 2022 survey. Therefore, we may be capturing those less affected by the war – who may have different views than those most affected.

Second, we should be wary of people’s professed opinions in times of war when the desire to be seen to be “rallying around the flag” induces a strong desire to express patriotic attitudes.

Putin’s war has backfired

Figure 1: 2019 and 2022 responses to a question asking respondents to place Ukraine on an imaginary ten-point scale between the west and Russia, among the 429 interviewed in both surveys (left) and the full samples (right).

With these caveats in mind, whether we look at those respondents who were resurveyed or the full sample, we see a clear orientation towards the west between December 2019 and October 2022. In both surveys, we asked respondents to place where their country should be on an imaginary ten-point scale between the west and Russia, shown in Figure 1.

Our data shows that Russia’s invasion did little but encourage Ukrainians to turn to the west. The invasion and brutal war – including war crimes, the targeting of civilians and civilian infrastructure, children forcibly moved to Russia, and mass displacement – have, perhaps unsurprisingly, done little to make people look towards Russia for their future.

Figure 2: 2019 and 2022 responses to the question, ‘It is best for our country’s security to be neutral and stay out of military alliances’, among the 20% interviewed in both surveys (left) and the full samples (right).

This trend is particularly stark among those aged 18 to 30, among whom nearly 47% think that Ukraine should be oriented towards the west, compared with just 3% who think it should be oriented towards Russia.      

With respect to Nato and neutrality, we see a similar shift. Consistent with other public opinion surveys that, for years, for Nato membership at 30-40%, our 2019 survey showed that support for joining the alliance was about 44%. But in our October 2022 survey, eight months after the invasion, the share of respondents favouring membership was 77%.

As you might expect, by October 2022 neutrality had become less attractive to many Ukrainians than it was in 2019, when more people than not saw neutrality as the preferred option. Now there is a clear majority against neutrality.

Support is especially high among younger people in the topped-up sample in 2022 – more than 70% of respondents aged between 18 and 30 disagreed with the statement that it would be “best for our country’s security to be neutral and stay out of military alliances”.

Russia’s invasion of Ukraine has been a military fiasco for Russia. It has also accelerated the process it was designed to prevent, the alignment of Ukraine with Euro-Atlantic institutions – especially Nato. Attacking a country where the majority of people before the war looked favourably on neutrality and sceptically towards Nato, Putin’s invasion has managed to flip this sentiment.

, Professor in Political Science and International Relations, ; , Professor of Government and International Affairs, ; , Professor of Geography, , and , Research Associate at UNU-WIDER,

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Homes that survived the Marshall Fire harbored another disaster inside – here’s what we’ve learned about this insidious urban wildfire risk

On Dec. 30, 2021, on record in Colorado swept through neighborhoods just a few miles from our offices at the University of Colorado Boulder. The flames , yet when we drove through the affected neighborhoods, some houses were still completely intact right next to homes where nothing was left to burn.

Although the people who lived in these still-standing homes were spared the loss of everything they owned, when they returned after the fire, .

The aftermath of the Marshall Fire in Louisville, CO. 

Noxious smells and ash on their windowsills and doorways initially made their homes unlivable – and potentially hazardous to human health. Some of these residents were still reporting health problems from being in their homes months later, even after the homes had been cleaned.

We study wildfires and their , and we knew people who lost their homes in the Marshall Fire. We also knew we had to act fast to study the fire’s impact so lessons from the Marshall Fire could help homeowners elsewhere avoid similar hazards in the future.

Dangerous chemicals absorbed into homes

Early on, because of our expertise on air quality and health, members of our community reached out to us to ask how they could remediate their homes from the smells and hidden ash, and what health risks they should be concerned about.

But this fire was nothing like the wildfires that our research groups at the University of Colorado had previously studied. Most of what burned on that day was human-made rather than vegetation. When human-made materials like electronics, vehicles and home furnishings burn, they and may affect health differently compared to when vegetation burns.

The outdoor air pollution was less of an issue because the wildfire was short-lived – the quieted down and changed direction about 11 hours after the fire started, and the finally fell. This snowfall ended the fire and cleaned the outside air of pollution.

Wildfire ash and dust entered homes under doors and around windows. Courtesy of Joost de Gouw

The key concern was what chemicals lingered inside the undestroyed homes – soaked up into the fabrics of carpets, sofas, drywall, air vents and more – that would slowly release into the home for some time after the fire.

We hypothesized that there were lots of volatile organic compounds (VOCs) – toxic gases, which were emitted during the fire that had seeped into homes and become embedded in the fabrics and building materials. Of particular concern were aromatic compounds like , and (PAHs), which are emitted from wildfires and have known health effects. In addition, we were worried about metals in the ash and soot deposited in homes, and the potential for it to become suspended in the air again when people returned and heating systems came on.

Despite knowing that some of these gases were toxic, we did not know the levels inside the homes, or what remediation efforts to suggest to residents, because little scientific research had been published on . We realized that we needed to do some of that research to help our own community – and the next community affected by a wildland-urban interface fire.

Collecting evidence inside

Many community members volunteered their homes for study sites. When we toured these still-standing homes 10 days after the fire, we saw what a rapid evacuation looks like, with lunch in the process of being made, laundry being folded, toys in the middle of pretend play … and dust, lots and lots of dust resulting from the fire.

We collected dust samples in about a dozen homes and then analyzed the samples in our labs.

We looked for molecules that could help us think about the origin of the dust. Not surprisingly, the dust was a combination of windblown soil, ash from the fire and typical household dust. That ash was high in typical combustion byproducts that are known to be toxic, and there was lots of ash, so cleaning up all the dust was important to remediation.

The homes that had been exposed to heavy smoke also still smelled like a chemical fire. A colleague likened it to the smell of gunpowder.

A chart shows benzene levels in a smoke-infiltrated home decreased when an air cleaner with a carbon-activated filter was running, but then rose again when the air cleaner was turned off. Joost de Gouw

As quickly as we could, we moved a state-of-the-art mass spectrometer into one of the most heavily affected homes in Superior and made measurements of airborne 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 would expect, but in early February these pollutants had decreased to more normal levels.

We researched ways in which people could protect themselves and found through experiments that air filters with activated carbon could provide excellent temporary relief from the indoor pollutants.

We also observed the results of professional remediation efforts. We are still poring over the air pollution data to understand which materials that burned, such as plastics, car tires, furniture, carpet and roofing material, contributed the most to the air pollutants we observed in the homes.

Continuing health effects

In addition to the air pollution and ash concerns, people living in the neighborhoods that burned are concerned about their health.

In an initial survey, residents reported a variety of symptoms that they think may be due to the smoke or air quality concerns of the fire, with the most common being itchy or watery eyes, headaches, dry cough and sore throat. More than half of respondents also reported disrupted sleep due to the stress of the fire, and almost a quarter attributed headaches at least in part to the stress of the event.

The physical symptoms could be due to the exposure during the fire. However, of those who have moved back into smoke-damaged homes, they report the symptoms most often inside their homes.

Left: ; Middle: ; Right: .

This fall, more than nine months after the fire, some residents reported rashes and burning sensations despite having cleaned their homes of ash and the smell of VOCs having dissipated. Another round of surveys is now helping gather more information about lingering symptoms. In addition to physical health symptoms, we are also asking questions about mental health, which is a growing concern from so-called natural disasters.

While we know that the VOC concentrations inside the homes that we worked in have returned to normal levels, some individuals may be more sensitive than others. And while there has been research into the health effects of some VOCs, , nor have studies looked at the health impacts of combinations of VOCs.

As global temperatures rise and once-wild landscapes at the edges of cities, the . We hope that our work can help people deal with the air pollution aftermath of future blazes.

This article is part of a collaboration with , The Center for Environmental Journalism at the University of Colorado Boulder, public radio and to explore the impacts of the devastating Marshall Fire one year after the blaze. The series can be found at the .

This article is republished from under a Creative Commons license. Read the .

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