Study reveals health impacts of returning to smoke-damaged homes

Six months after the Marshall Fire destroyed more than 1,000 homes in Boulder County, Colorado, more than half of the residents of remaining homes in the area have reported physical symptoms; Including headache, sore throat or strange taste in the mouth. They attribute it to poor air quality, a new study by CU Boulder finds.

An accompanying study showed that the air quality inside one home after the fire was equivalent to the air quality in downtown Los Angeles in the 1990s on a high pollution day, with the dangerous gases remaining for weeks.

“Our research suggests that there may be important health impacts on people returning to homes damaged by smoke or ash after a fire, and that we need to have systems in place to protect them,” said Colleen Reid, assistant professor of geography and co-author of the study. Author of studies.

Newspapers published this week in ACS Environmental Science and Air Technologyare the first to explore the air quality inside homes affected by smoke and ash and assess the health effects on the people living in them. They come as fires become more common in the Wildland-Urban Interface, as happened in Paradise, California, in 2018, and Lahaina, Hawaii, in 2023.

A lot of time has been spent studying wildfire smoke, which is what you get when you burn plants. But what do you get when you burn down a house with all its furniture, electronics, and cars? Until now, there was very little information known.”

Joost De Gouw, co-author, professor of chemistry and CIRES Fellow at the University of Colorado Boulder

Record winter fire

The December 30, 2021 Marshall Fire, fueled by 100 mph winds and record dry conditions, burned 1,084 structures in densely populated areas, claimed two lives and forced 37,000 people to evacuate.

Once residents returned to their homes, scientists at the University of Colorado Boulder, just 4 miles from the fire, began receiving calls.

“At first, they felt really lucky, but when they entered their homes they saw ash everywhere and it smelled different — like a campfire or chemicals,” Reid said. “They asked: What should we do? We don’t know if it is safe to return.”

With little research providing answers, scientists began investigating.

Ten days after the fire, De Gouw’s team installed field tools at an intact home on the border of the block where the homes burned. Over the course of five weeks, they continuously measured the presence of 50 gases.

Meanwhile, Reed and his colleagues developed a survey to send to residents within the burn perimeter, as well as a random sample of those living within a two-mile radius.

In six months, 642 people responded; 413 responded at the one-year mark.

About 55% of participants reported symptoms they attributed to the fire six months later, and survey answers depended largely on the condition of their homes when they returned home.

For example, those who found ashes inside were three times more likely to suffer from headaches than those who did not find ashes. Those who reported an unusual smell were four times more likely to experience a headache than those who did not pick up an unusual smell.

People with the same symptoms tend to cluster together, according to computer mapping analyses. For example, those who lived near destroyed homes, especially in the direction the wind was blowing on the day of the fire, were more likely to report a strange taste in their mouths.

“These findings are consistent with chemical exposure and suggest that residents of homes damaged by smoke and ash may have experienced persistent air quality and physical health challenges months after the fire,” Reed said.

Long-term effects are uncertain

The authors cannot determine which chemicals caused the health effects reported by survey participants. But measurements at one home found high levels of volatile organic compounds (VOCs) such as benzene, a carcinogen found in gasoline and diesel exhaust.

Dust samples also showed high levels of copper, zinc, arsenic and industrial pollutants called polycyclic aromatic hydrocarbons (PAHs), which are known to cause eye irritation.

“If your house survives, and your neighbor two doors down burns down, all that melted stuff can fly through the air and find its way into your house” and lodge itself in furniture, carpet and drywall, Reed said.

The authors stress that VOCs are only considered carcinogenic at levels much higher than they found, and people are regularly exposed to low levels daily through pollution.

Their research found that simple measures, such as opening windows and using low-cost carbon-activated air filters, can significantly improve air quality.

A year after the fire, the number of residents reporting symptoms had fallen to just 33%, and most said confidence in the air quality in their homes had improved.

Until more studies are conducted, researchers cannot determine whether such exposure can lead to long-term health problems.

However, Reid urges anyone entering a home damaged by smoke or ash immediately after a wildland urban interface (WUI) fire to be careful, and to wear KN95 masks and gloves.

They hope their ongoing research will lead to clearer guidelines for policymakers and insurers about when it is safe for people to return to smoke-damaged homes.

“This wasn’t just a fire. It was a personal feeling,” De Gouw said. “Knowing that we could at least begin to provide some answers for our community made the work more meaningful.”