Wildfires that consume homes and vehicles can release harmful compounds into the air through ash and smoke. A study published in ACS ES&T Air indicates that individuals returning to intact homes may experience health issues long after nearby fires are put out. A survey conducted among victims of the 2021 Marshall Fire in Boulder, Colorado revealed that residents near burned properties often reported headaches, sore throats, and coughs.
Wildland-urban interface fires, such as the Marshall Fire and the numerous blazes in early 2025 around Los Angeles, incinerate both vegetation and human-made materials. When these materials burn, they release polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) in greater amounts than natural biomass. The World Health Organization has linked exposure to these airborne substances with adverse health effects, including respiratory and cardiovascular diseases. Following the Marshall Fire, researchers from the University of Colorado, Boulder, detected increased levels of PAHs and VOCs in homes that didn’t burn but were still affected by smoke; however, they did not explore the potential negative health impacts of exposure to these compounds. Hence, another team at CU Boulder, led by Colleen Reid, created and conducted a survey to assess the symptoms that residents experienced.
The survey took place on two occasions: six months after the fire (with 642 participants) and again at one year (with 413 participants), specifically among those whose homes were not damaged. The researchers inquired about the effects of smoke post-fire and the health issues reported. They discovered the following:
- The most commonly reported fire-related symptoms included itchy or watery eyes, headaches, dry coughs, sneezing, and sore throats.
- 61% of participants noted that their homes smelled like campfire or chemicals one week after the fire, but those odors diminished over time.
- 65% of respondents reported finding ash in their homes after the fire.
- At six months post-fire, most respondents felt less assured about the air quality in their homes and neighborhoods compared to before the fire, although that sense of security largely returned by the one-year mark.
The research team noted that many symptoms reported by participants, such as headaches and unusual tastes, were more prevalent among those living within 250 meters of a burned area. Symptoms like dry coughs, itchy or watery eyes, and sneezing were statistically linked to changes in home odors following the fire, as well as to the presence of smoke damage or ash inside the home. Remarkably, respondents who discovered visible ash were over three times more likely to report headaches than those who did not. Many participants indicated that cleaning their homes or HVAC systems, hiring professional cleaners, or replacing damaged furniture or carpets helped to lessen odors over time. The researchers hope their findings will aid in shaping future regulations and recommendation for safely returning home after a wildfire.
The authors thank the National Science Foundation, the Cooperative Institute for Research in Environmental Sciences (CIRES) Rapid Innovation Research Program at the University of Colorado, Boulder, the Harvard JPB Environmental Health Fellowship, and the Developmental Core of the University of Colorado Population Center for their support.
