After the Flames in Post-Fire WUI Homes: Characterization of Toxic Emissions, Environmental Concentrations, and Exposures

An increasing umber of wildfires that approach has made the Wildland-Urban Interface (WUI) one of the most dangerous regions in the United States. When WUI fires burn through communities, the destruction extends far beyond structural losses. Unlike wildland fires that mostly burn trees and grass, WUI fires ignite plastics, electronics, and household furnishings, releasing a complex mix of harmful air pollutants. This project will identify the pollutants that are released and quantify the amount produced when materials typically present in WUI environments burn. Controlled burns will be conducted in the laboratory to understand how these pollutants move through homes, settle on surfaces, and become airborne again, potentially exposing returning residents and workers. Air samples from homes affected by the 2025 Los Angeles fires will also be collected. Results of the project will improve our understanding of indoor air quality after a fire and help guide safer clean-up and reoccupation strategies. Although the frequency and severity of WUI fires have increased dramatically in recent years, critical gaps remain in our understanding of the chemical emissions and exposure risks they create. Most existing studies focus on wildland vegetation fires and fail to account for the complex mixture of pollutants released when manmade materials burn. Additionally, there is limited knowledge of how combustion conditions influence pollutant formation in WUI fires, and even less is known about how toxic emissions infiltrate homes, persist on indoor surfaces, and re-emerge after cleanup. To address these challenges, this project has three integrated objectives: (1) characterize multi-phase organic and inorganic emissions (including speciated particulate metals, volatile organic compounds (VOCs), carbonaceous particles, as well as gases such as carbon dioxide (CO2) and nitrogen dioxide (NO2)) from materials commonly found in WUI environments under controlled combustion conditions that simulate real-world fire scenarios; (2) investigate the penetration of outdoor fire emissions into indoor environments, examining the roles of environmental and human factors, chemical signatures, spatial gradients, source apportionment, and long-term pollutant dynamics; and (3) develop and validate a computational model that simulates indoor pollutant dynamics, including dispersion, deposition, resuspension, and off-gassing. This research will advance fundamental understanding in chemical, atmospheric, and exposure sciences by bridging key knowledge gaps in the emission, transport, and indoor infiltration of pollutants from WUI fires. By integrating real-time field measurements using innovative instrumentation with bench-scale and larger-scale combustion experiments and advanced exposure modeling, the project will provide a comprehensive framework for understanding the fate of WUI fire-emitted pollutants across environments. Furthermore, this research will refine exposure modeling frameworks by incorporating empirical data on time-varying indoor concentrations and surface interactions, enabling the simulation of critical yet understudied human exposure processes in WUI fire-impacted communities. The outcomes will reshape our understanding of post-fire air quality hazards and set the foundation for predictive models of WUI fire emissions and their health impacts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.