UCLA report: Standing homes air quality worsened over time in wildfire areas

A UCLA study released Friday, Jan. 2, found that homes that survived the Eaton and Palisades fires but were exposed to ash or smoke saw worsening air quality over time.

According to the study, concentrations of volatile organic compounds, benzene, toluene, ethylbenzene, and xylenes, remained significant or even increased after the fires were controlled and outdoor air quality recovered. Researches began collecting samples on the second day of the fires and concluded on Feb. 18.

“These findings underscore the need for targeted interventions to minimize indoor exposures during the recovery phase,” study co-author Dr. Michael Jerrett, professor in UCLA Fielding’s Department of Environmental Health Sciences and the Jonathan Fielding Chair in Climate Change and Public Health said in a statement. “These findings raise concerns about indoor air quality post-wildfire, and the potential for prolonged exposure leading to significant health impacts.”

The study appeared in the journal Environmental Science and Technology Letters. Researchers gathered samples in phases from both fire areas. During the period before 50% containment, the active burning period with more than 50% contained and the post-fire period.

Different volatile organic compounds peaked at different points during and post-fire. Compared to the active burning period, indoor-to-outdoor ratios were significantly higher post-fire. Elevated VOC levels were particularly present in uninhabited homes within burn zones.

“Even after wildfires are extinguished, residents may remain at risk of exposure to indoor VOCs,”  Dr. Yifang Zhu, professor in the Department of Environmental Health Sciences and a co-author of the study said a statement. “This pattern suggests that smoke-impacted materials within the home could continue to release VOCs into the indoor environment, creating a prolonged source of exposure. To reduce these risks, residents returning to affected homes should adopt measures to improve ventilation and filtration.”

According to UCLA, mitigation methods include regularly opening windows, operating central heating, ventilation and air conditioning systems with filters rated at least minimum efficiency reporting value 13 and using portable high efficiency particulate air purifiers with charcoal filters when available.

“What made these urban wildfires particularly concerning was the potential toxicity of the resulting smoke, because VOCs are ubiquitous in residential areas, with common sources including building materials and household products, like cooking and cleaning supplies,” Zhu said.