This blog is being shared under the SOT Secretary’s name as part of their official duties and should not be interpreted as their personal or professional opinions.
This blog was written by Talia Sager.
Wildfires have become increasingly frequent, severe, and chemically complex as climate change intensifies and development continues to expand the wildland urban interface (WUI), where natural and built environments meet. WUI fires generate a unique and still poorly understood mixture of emissions produced by the burning of natural biomass and synthetic materials. These pollutants are found in, but not limited to, the ambient air, indoor air, and settled dust, creating multiple pathways for human exposure. During the 2026 Informational Session, “Wildland Urban Interface Fire Beyond the Smoke: Exploring the Broader Environmental and Health Impacts,” speakers shared insights from their diverse research efforts offering an in-depth look at how WUI fires produce and distribute harmful toxicants and what these exposures mean for public and environmental health. The session was chaired by Cynthia Choo, PhD, UL Research Institutes’ Chemical Insights and co-chaired by Sumeet Saksena, PhD, East-West Center.
Microvascular Health Effects
Timothy Nurkiewicz, PhD, West Virginia University, opened the session by presenting research on how WUI fire emissions affect systemic microvascular function, an impact that had not previously been evaluated.
Using a laboratory-scale WUI combustion model, his team exposed rats to emissions produced from combusted pellets composed of Douglas fir, oriented strand board, vinyl flooring, and foam insulation, which generated high levels of particulate matter (PM) and volatile organic compounds (VOCs). The 1–3 day exposure duration produced depositions equivalent to about seven days of human exposure, reflecting conditions faced by first responders and residents unable to evacuate. Intravital microscopy revealed a sharp reduction in endothelium-dependent dilation, indicating significant microvascular impairment and potential cardiovascular health implications following WUI emission inhalation.
Metal(loids) and Transformations
Mohammed Baalousha, PhD, University of South Carolina, followed with an examination of how WUI fires transform fuels into materials with altered chemical and physical properties. His team analyzed ash from the 2020 LNU Lightning Complex and North Complex fires, collecting 60 ash samples to assess vaporization temperature, combustion time, fuel type, and elemental composition.
Using advanced tools such as ICP-MS and SP-ICP-TOF-MS, the team identified nanoparticles within complex particle mixtures and changes in oxidation states and mixed metal phases. Notable findings included greater toxicity and bioavailability of chromium and arsenic from chromated copper arsenate (CCA)–treated wood, and the unexpected detection of magnetite though iron solid-phase speciation. The presence of magnetite raised important questions about its potential role in health outcomes associated with WUI emission exposure.
Heavy Metal Contamination and Remediation Needs
David Kalafut, UL Research Institutes’ Chemical Insights, then discussed findings from his team’s investigation of heavy metal contamination following the 2023 Maui fires. His team assessed 54 homes and two businesses in Lahaina and two homes in Kula and used an owner questionnaire to document building properties. Because Soiltac was widely used for dust suppression, the team focused on XRF field screening, soil core sampling, and geo-tagging for point-source attribution.
Key findings showed elevated contamination in older homes built before the bans on CCA-treated wood and lead materials. Metal contamination from burned vehicles extended up to 40 meters from each site. The multi-core strategy employed here was compared with federal and state agencies’ Incremental Sampling Methodology, illustrating the tradeoff between cost-effective composite sampling and higher-resolution spatial data. Despite methodological differences, both approaches indicated effective remediation of soil metal levels and informed community impact reports. The team plans to use findings from this study to recommend more targeted regulatory strategies, such as grouping homes by age and build to guide remediation efforts.
Air Quality and Indoor Exposure Profiles
Next, Parham Azimi, PhD, Harvard T.H. Chan School of Public Health, presented findings from coordinated indoor and outdoor assessments of pollutant exposure following the 2023 Maui and 2025 Los Angeles fires. Using comprehensive indoor and outdoor environmental measurements, his team monitored 20 Maui homes and 50 Los Angeles homes using gravimetric PM2.5/PM10 sampling, active and passive VOC and polycyclic aromatic hydrocarbon (PAH) sampling, continuous indoor air quality monitoring, and settled dust analysis using XRF.
Findings demonstrated outdoor PM levels generally exceeded indoor levels, and portable air cleaners reduced the indoor to outdoor PM2.5 ratio in affected homes. Dust and airborne particle composition largely reflected local soil sources rather than fire contributions. In contrast, indoor VOCs were up to 10x higher than outdoors, with pollutants such as benzene and napthalene frequently exceeding health-based benchmarks.
Hidden Ultrafine Particle Risks
The session concluded with findings from José Guillermo (Memo) Cedeño-Laurent, PhD, Rutgers Environmental and Occupational Health Sciences Institutes, whose team analyzed the environmental and health impacts from the 2025 Los Angeles fires, which coincidentally aligned with his time there for a conference. Although PM2.5 levels appeared similar to pre-fire concentrations, about 40% were in the PM0.1 size fraction (ultrafine range), suggesting significant underestimation of exposure risks based on PM2.5 alone.
Further analysis showed medium and high molecular weight PAHs, which are more toxic than lighter PAHs, and non-crustal metals were primarily found in the PM0.1 fraction. MPPD modeling estimated that PM0.1 accounted for over one-third of inhaled dose during the event. Ash analysis revealed that about 70% of ash mass was considered inhalable, with more than 25% in the PM2.5 range and able to reach lung alveoli, underscoring significant health risks.
Key Takeaways
Across all presentations, this session highlighted the multidimensional environmental and human health challenges posed by WUI fires. Speakers highlighted the need to deepen scientific understanding of WUI-specific exposures and to develop stronger, data-driven strategies that support affected communities, ultimately helping residents return home safely and more quickly after a fire.
This blog reports on the Informational Session titled “Wildland Urban Interface Fire Beyond the Smoke: Exploring the Broader Environmental and Health Impacts” that was held during the 2026 SOT Annual Meeting and ToxExpo. An on-demand recording of this session is available for meeting registrants on the SOT Online Planner and SOT Event App.
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