Air pollutants may persist in homes far after wildfires are extinguished: study

Wildfire smoke may linger in homes long after first responders have extinguished the initial blaze, a new study has found.

Components of the smoke can attach to home surfaces, such as carpets, drapes or counters — prolonging exposure to those inside and possibly causing health issues, according to the study, which was published Friday in Science Advances.

Although this risk can remain even after initial air purification, the authors stressed simple surface cleaning — like vacuuming, mopping or dusting — can decrease exposure.

“Events like the Marshall Fire in Colorado, the wildfires in Canada and the recent fires in Hawaii present serious exposure potential — not just when they occur but well after,” said senior author Delphine Farmer, a chemistry professor at Colorado State University, in a statement. 

To find their conclusions, Farmer and her colleagues burned pine wood chips in a net zero energy residential sampling site, operated by the National Institute of Standards and Technology (NIST) in Maryland.

This facility, they noted, is often used to investigate how different systems affect the ways energy, water and air travel through a single-family house.

“The NIST Net Zero House allowed the researchers to track the movement and transformation of chemicals in the air and onto surfaces in real time,” said co-author Dustin Poppendieck, an environmental researcher at NIST, in a statement.

The scientists were able to deploy detailed instrumentation available at the house in ways that don’t interfere with the behavior of the smoke, according to Poppendieck.

The smoke injection occurred regularly over several days in amounts that were comparable to or slightly below the particulate matter levels present during this year’s Canadian wildfires, the authors explained. 

The team members then measured air quality levels and surface conditions after they opened exterior doors and windows and after cleaning and using the house’s built-in air purification systems.

While ventilation and portable air purifiers prove very effective for removing particles, their ability to clean up volatile organic compounds (VOCs) is much more limited, the authors noted.

Meanwhile, indoor surfaces generate what the scientists described as “a persistent emission source of smoke VOCs.”

These compounds — present in building products, paints, sprays and furnishings — are linked to many respiratory symptoms, as well as headaches, nausea and dizziness, according to the Environmental Protection Agency.

During their investigation at the Net Zero House, the scientists found many VOCs persisted for days following the smoke injection, prolonging the air pollution exposure pathways for humans.

The authors also determined wiping and cleaning surfaces could play a significant role in reducing these risks.

By publishing this paper, Farmer explained, the authors hope to provide “actionable and practical information on how to protect yourself and clean your home.”

The study results could have widespread applications, including for large-scale air pollution events, like the train derailment in East Palestine, Ohio, according to Farmer.

Because of the paucity of existing indoor air research on this subject, Farmer said she and her colleagues relied on previous research related to cigarette smoke to guide their approach.

Burning nicotine, she explained, generates certain harmful compounds called nitrosamines, which are cause for “real concern from thirdhand smoke that is left behind.”

“With wildfire smoke, we found there was a huge diversity of organic compounds that stick to surfaces, which then slowly bleed off,” Farmer added.

Moving forward, Farmer said she would like to investigate the effectiveness of different kinds of cleaning approaches — and whether residents should simply resort to commercial cleaning supplies or if they need to take “more drastic steps like replacing the drywall.”

“Continued efforts to reduce outdoor air pollution and wildfire smoke events are clearly necessary for reducing prolonged exposure to hazardous air pollutants,” the authors stated.