8
The Future of WUI Fire Research
Wildland-urban interface (WUI) communities are growing rapidly, and the threat of severe fires in these communities is also growing. WUI fires vary in their characteristics and include large wildland fires that burn communities in their path, and fires of smaller spatial extent in intermixed wildland and urban areas. Despite their varied characteristics, WUI fires have the common characteristics of fuel mixes that are distinct from both wildland and urban fires, and a combustion chemistry that is spatially and temporally heterogeneous. These unique characteristics of WUI fires can lead to toxicants and exposures that are largely uncharacterized.
Earlier chapters in this report identified research needs for WUI fires that include the following:
- Identifying at-risk communities and vulnerable populations and evaluating interventions
- Characterizing fuel types, combustion characteristics, and emissions
- Defining the chemistry of toxicants from WUI fires in air, in water, and on land, including ash and debris
- Predicting the multimedia transport and transformation of WUI fire toxicants
- Identifying and quantifying toxicant exposures and health impacts resulting from WUI fires
This chapter summarizes and prioritizes those many research needs into a research agenda. To be most effective, the research agenda should be carried out with multidisciplinary teams who integrate work that ranges from hazard identification and emission characterization to measurement of exposures and health outcomes.
Figure 8-1 maps this range of WUI fire–related research activities and their interdependences. As shown in the figure, WUI communities at significant risk of fire need to be systematically identified, along with vulnerable populations. Once communities are identified, the potential fuels in those communities can be identified and characterized, including an analysis of how those characteristics vary among different populations. Laboratory and field measurements are needed to improve understanding of the combustion conditions that these fuels are exposed to. The fuels and combustion conditions can help reveal important multimedia chemical pathways of toxicant formation in WUI fires. The toxicant formation pathways, in turn, influence the transport and transformation of toxicants as they leave the immediate fire plume and their chemical evolution over time. The transport and chemical evolution of the pollutants, and the distribution of vulnerable populations, will determine potential exposures and health outcomes. These potential exposures and health outcomes must be related back to an understanding of the at-risk communities and vulnerable populations.
Implementing an effective research agenda will be challenging. While fundamental data relevant to wildland and urban fires have been collected for decades, understanding the combustion of mixed wildland and urban fuels
requires new fundamental information that is not currently available. The variability in WUI communities and the types of fire hazards that communities and vulnerable populations are exposed to spans a wide range. Building a comprehensive and fundamental body of knowledge on WUI fires will require a long-term effort.
Field studies of WUI fires, involving both measurements and modeling, are needed to develop a shorter-term understanding and to direct longer-term research efforts. Field studies that characterize fires at the WUI will be challenging, however, because the interface, by definition, is just one part of the fire. Collecting data in targeted WUI areas of rapidly evolving fires is difficult and may require new research approaches. Field studies are essential, however, and need to be implemented despite these challenges.
Finally, the better understanding of WUI fires that will emerge from the research agenda needs to be made relevant to both decision-makers addressing WUI fires and their aftermath, and the public seeking to minimize toxicant exposures and health impacts. Measurement and modeling tools are needed to predict and quickly assess WUI fire chemistry, toxicant formation, and potential exposures. The effectiveness of interventions to minimize potential exposures also needs to be assessed.
Recommendation 1: To understand the chemistry, exposures, and health impacts of toxicants resulting from WUI fires, researchers and agencies that fund research should implement an integrated, multidisciplinary research agenda. Agencies funding, and investigators performing, research on WUI fire emissions should coordinate their research plans, and they should create widely accessible repositories for data and information relevant to WUI fires.
RESEARCH AGENDA
Tables 8-1 and 8-2 summarize the multidisciplinary research agenda recommended by the committee. In Table 8-1, the committee has summarized and prioritized research needs identified in the chapters of this report. The committee has organized research needs into four primary areas (columns) and three complementary approaches (rows). There is also an overarching research need (collecting WUI-specific data) that spans all of the primary areas (columns). This condensed list of research needs was created both by combining multiple, detailed research needs
TABLE 8-1 Research Priorities for Fires at the Wildland-Urban Interface (WUI)
| Fuels and Emissions | Chemistry, Transport, and Transformations | Exposure and Health | Measurement Science and Analytics | |
|---|---|---|---|---|
| Collecting WUI-specific data | Assemble data on fuels, emissions, chemistry, transformations, exposures, and health impacts that are attributable to fires at the WUI, differentiated from wildland fires and urban fires, which will require novel measurements and analyses | |||
| Fundamental measurements and data |
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| Field and population studies |
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| Prediction, assessment, and exposure-mitigation capabilities |
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TABLE 8-2 Factors Influencing the Prioritization of Research Needs in This Report
| Factor | Criteria |
|---|---|
| Decision-makers who are the audience for the research | Decision-makers informed by WUI fire research may range from community planners charged with defining building codes in WUI communities, to public health professionals and regulators, to officials charged with rapidly communicating information to communities impacted by WUI fires. This range of decision-makers will have different portfolios of research needs and will require information on different timescales and at different technical levels. |
| Timeliness and cost effectiveness | Within a research portfolio, projects will range from those that can be rapidly implemented with immediate impact to those that will require a long-term commitment; they will also vary in cost. |
| Extent of applicability and magnitude of effect | Research portfolios will have the objectives of being broadly applicable and of addressing the most important questions related to the impacts of WUI fires and the toxicants they emit, including inequitable impacts across populations. Nevertheless, some research will be focused relatively narrowly, such as projects examining particular materials that might be combusted in a WUI fire or particular communities impacted by WUI fire emissions; both narrowly and broadly focused research can vary in the magnitude of the effect that is addressed; for example, the extent of use of materials that might be combusted in WUI fires varies, and the toxicants released in WUI fires vary in their toxicity and health implications and in the nature of their exposure. |
| State of scientific capabilities | Some research will address focused questions using currently available techniques, while other research might expand the range of questions that could be addressed by improving measurement or other tools used in WUI research. |
appearing in individual chapters, and by identifying the research needs that the committee identified as high priority. The factors and criteria used in establishing the high-priority needs are described in more detail in Table 8-2.
Research Priorities Related to Fuels and Emissions
Fundamental Measurements and Data
Research priorities related to fuels and emissions include mapping WUI communities and their material loadings and compositions. As described in Chapters 2 and 3, a need exists for both detailed maps of WUI communities and a characterization of the types of structural materials present in each community. Systematically organized data on the materials present in structures could be coupled with local, regional, and national inventories of structures to develop fuel loading maps in geographic information systems. This type of system is already available for wildland fires and could be developed in an analogous manner for WUI regions. This is identified as a high-priority research area because it is foundational to defining the scope of other research activities (e.g., what types of urban materials should undergo laboratory testing and what types of atmospheric chemical transformations are likely to be important) and will be broadly applicable to many WUI fires.
Research is also needed to improve understanding of the combustion conditions in WUI fires and how meteorology and urban materials’ composition and configuration, both within the landscape and within a building, interact to determine the ventilation conditions and the relative contributions of smoldering, glowing, and flaming combustion in different regions of a WUI fire. As described in Chapter 3, the impact of turbulence is difficult to recreate at small scales, and a range of experimental approaches may be needed to fully understand the coupling between the fuel and the environment in a WUI fire. As with the other priority research on fundamental measurements and data, this information is critical for developing predictive models for emissions and plume dispersion.
Urban materials contain varying elemental compositions in different ratios. Laboratory testing and mechanistic modeling, as described in Chapter 3, have demonstrated the importance of fuel composition and ventilation on the resulting emissions. Research can expand on these topics to study the more diverse mixtures relevant to WUI fires using models and testing equipment able to simulate WUI fire conditions. This is identified as a high-priority research area because the information is broadly applicable and because it is essential to understanding the complex
fuel mixtures and combustion conditions that may be anticipated in a fire, to provide an initial assessment of what compounds will be emitted into the air and what residues are left behind.
Field Studies
Field measurements provide important insights into WUI chemistries that are occurring and complement the fundamental studies described in the previous section. The research needs described below were identified as high priority; these studies can be used to guide the direction of other research priorities.
Post-fire evaluations of fire exposure and damage assessments have proven a valuable tool for understanding WUI fire ignitions and the features that make a structure most vulnerable to fire. A plausible extension to these assessments is studies to supplement the information with measurements of fuel consumption and residues. An infrastructure for rapid response could allow researchers to sample emissions from smoldering fuels or off-gassing from other materials; these samples would provide important exposure information for workers involved in cleanup activities or people returning to their homes after an evacuation. Opportunistic measurement of WUI fire plumes that impact ambient monitoring locations or long-term atmospheric observatories could also provide valuable information on the composition of these plumes.
Emissions measurements in WUI fire plumes are the only way of capturing the true nature of WUI emissions at scale. Experience with wildland fire research has demonstrated that multiple skill sets are needed for a comprehensive understanding of how the fuels, the meteorology, and the topology couple to influence combustion conditions and the resulting plume emissions. Coordinated multi-platform, multimedia studies of WUI fire energetics and emissions are needed to provide a comprehensive understanding of fire and emissions phenomena. The unpredictable nature of WUI fires and the priority placed on emergency response during a WUI fire will make field studies challenging and require careful advance planning with multiple partners at the federal, state, and local levels.
Prediction, Assessment, and Exposure-Mitigation Capabilities
A comprehensive evaluation of the conditions under which WUI fires have occurred across the United States will provide valuable information on which communities are at greatest risk and under what conditions the threat is largest. WUI fires have shown characteristics distinctive from those of other wildfires, and current fire danger rating systems may not translate to WUI fire danger. A better understanding of the areas and times of highest risk is of immediate importance to develop protective danger ratings and to better target communities with the greatest need for mitigation actions.
Predictive models of wildfire emissions are an essential component of the emergency response used by frontline workers to develop public health guidance. Knowledge of the magnitude and the range of hazardous compounds that can be emitted by a WUI fire is needed in real time to determine exposure reduction actions for first responders and effective public health interventions.
Multiple WUI fire damage mitigation strategies exist, at structure, neighborhood, and community scales, and some, like maintaining defensible space around a structure or using ignition-resistant building materials, are widely adopted in some areas; yet destructive WUI fires persist. Research is needed to identify the most effective mix of mitigation strategies, while acknowledging that resources may be limited. Identifying the environmental conditions, topography, and community characteristics where WUI fires are most likely to occur can support the understanding of which strategies are most effective in differing regions. Additionally, a better understanding of how the choice of materials impacts ignition, combustion conditions, and ultimately emissions is an important step in reducing the risk and hazards associated with WUI fires.
Research Priorities Related to Chemistry, Transport, and Transformations
The research priorites identified for chemistry, transport, and transformations will both be informed by research on fuels and emissions and will inform research related to exposures and health impacts. The rationales for the need for coupled work in fundamental measurements, field studies, and modeling is analogous to the rationales for research on fuels and emissions.
Fundamental Measurements and Data
A combination of approaches is needed to quantify and characterize primary emissions (e.g., reactive species, primary toxicants) emerging from WUI fires, including controlled laboratory combustion of realistic mixtures of WUI materials at realistic combustion conditions, field measurements during plume transects with aircraft and instrumented mobile laboratories, and satellite remote sensing tools.
Identification of the secondary species with toxic potential formed during atmospheric transport and their formation kinetics and mechanisms is needed in order to predict downwind composition, concentrations, and impacts. Controlled laboratory experiments (e.g., flow tube, chamber) are needed to examine the chemistry of individual compounds and realistic WUI fire mixtures for key WUI fire oxidants. Experiments are particularly needed to elucidate the aqueous, multiphase, and catalytic chemistry, as well as secondary aerosol formation from intermediate-volatility organic compounds. Work is needed to identify tracers that assist with determining the relative importance of key chemical pathways in subsequent field campaigns. These laboratory and field data, for air and other media, should be assembled into accessible databases.
Field Studies
Coordinated field measurements in WUI fire plumes at a range of aging times are needed to determine the dominant daytime and nighttime atmospheric oxidants and the concentrations of these oxidants. Measurements should include tracers of oxidant chemistry. This work will help facilitate estimates of atmospheric lifetimes and geographic distributions of primary toxicants.
Making use of the insights from laboratory studies to identify tracers of chemical pathways, coordinated field measurements (near-field through regional or continental scale) are needed to identify the dominant precursors and formation pathways (gaseous, aqueous, multiphase, catalytic) for the major secondary species with toxic potential. These should be prioritized in model development.
Detailed assessment is needed of the potential for water and soil contamination, including standardization of procedures for testing. Efforts should address a wide range of potential chemical contaminants to determine potential areas of concern.
Prediction, Assessment, and Exposure-Mitigation Capabilities
Condensed chemical mechanisms are needed for WUI fire applications in atmospheric chemical transport models. Multimedia partitioning and reactivity should be considered when lumping chemicals to facilitate gaseous, aqueous, multiphase, and catalytic pathways, as appropriate. Sub-grid-scale processing modeling tools are also needed in atmospheric chemical transport models to represent the chemistry in the near field where concentrations are high, since the chemistry is nonlinear.
Development and use of improved retrospective/prospective models to track the atmospheric chemistry of WUI fires are needed. Insights from laboratory and field work concerning the dominant emissions, oxidants, and pathways through which WUI fire emissions are transformed in the atmosphere; condensed chemical mechanisms; and model processing tools should be incorporated.
A need exists for community water systems to evaluate risk and plan for response based on potential and expected levels of contamination after a WUI fire. Plans for evaluating risk should be standardized across local jurisdictions.
Research Priorities Related to Exposure and Health
The research priorites identified for exposure and public health are based on the need for health impact information being a primary driver for the entire research agenda. While these research needs will be informed by research on fuels and emissions, and chemistry, transport, and transformation, research on exposure and health impacts should progress in parallel with research in other areas.
Fundamental Measurements and Data
Assessments of smoke exposure typically rely on outdoor concentrations. A better understanding of the indoor penetration, composition, and persistence of smoke during wildfires in general, and of the chemical emissions profiles of WUI fires in particular, is needed.
Studies that explicitly define the particular type of fire (i.e., wildland fire vs WUI fire) to which the general population is exposed are needed to clearly delineate the types of health effects that could emerge, and to possibly mitigate them, as pollutant emissions (as well as toxicant concentrations) between wildland fires and WUI fires can be quite different.
Additional studies are needed to evaluate the health implications of wildland fire and WUI fire emissions other than particulate matter, such as volatile organic compounds, semi-volatile organic compounds, and polyaromatic compounds, as particulate matter has been the primary metric related to health outcomes in almost all studies up to now. Studies should also examine exposures to contaminants in water.
Field Studies
Research is needed to further characterize the chemicals and health impacts of WUI fire emissions via multimedia routes of exposure, including inhalation, dermal exposure, and ingestion.
A better understanding is needed of the acute and persistent effects of exposures to toxicants related to WUI fires, which may include biomonitoring studies of general populations and vulnerable subpopulations.
A better understanding is needed of the effects of exposures, especially for firefighters and local communities, and should include examining acute, chronic, and delayed health outcomes.
Prediction, Assessment, and Exposure-Mitigation Capabilities
Insufficient research exists on acute exposures and acute and chronic health effects in WUI firefighters and the community. Research is needed on the effectiveness of interventions to mitigate WUI firefighter exposures and the associated adverse health effects.
A need exists to better identify at-risk and vulnerable residents and workers affected by near-field WUI fires and to identify culturally appropriate interventions to reduce adverse health impacts.
A better understanding is needed of the health outcomes for vulnerable populations, resulting from exposure to the complex mixtures of chemical and particle emissions from WUI fires. Health equity considerations for vulnerable populations are needed for WUI fires. Items to consider include disparities related to being a vulnerable population, access to health care and communications, homeownership versus rental or use of a mobile home, occupation, and short- and long-term WUI fire exposures.
Further studies are critical to understanding whether long-term physiological and psychological outcomes associated with regional exposures and the general public are similar for WUI and wildland fires. Moreover, health effects of fire exposures on children are a critical direction for more research.
Research Priorities Related to Measurement Science and Analytics
Fundamental Measurements and Data
Understanding of emissions exposures and health effects associated with WUI fires is often limited by measurement capabilities. As discussed in more detail in Chapter 7, new analytical methods are needed for measuring a wide variety of chemical, particle, and biological indicators of toxicants in studies on emissions, exposures, and health outcomes.
Field Studies
Field measurements of the concentrations of species associated with WUI fires in air, water, and soil involve constraints on the size, power requirements, and other features of the analytical methods that can be deployed. Current and emergent analytical methods should be optimized for field deployment and increased accessibility.
Estimating human exposures requires that air, water, and soil measurements be combined with records of human activity that result in inhalation and ingestion of, and dermal exposure to, toxicants from WUI fires. Biomarkers can reduce the need for some of these data in exposure estimation; however, new biomarkers are needed that are more specific to WUI fires and can be used for exposure and toxicity assessment.
Standardization is needed for the methods used to test water and soil after WUI fires, and databases of information should be established.
Prediction, Assessment, and Exposure-Mitigation Capabilities
Large-scale modeling of WUI fire plumes could be assessed by augmenting ambient monitoring networks or through other sensing systems. Additional sensing capabilities should be deployed to assess chemical compositions of fire plumes.
CROSS-DISCIPLINARY COORDINATION
As shown in Figure 8-1, the information needed to understand the toxicants emerging from wildland fires, structural fires, and WUI fires; their effects; and whom they affect spans a broad range of scientific disciplines. Research findings from each of these disciplines needs to be continuously communicated across disciplinary boundaries because each step in the chain—from hazard identification to quantification of exposures and health effects—depends on information emerging from other steps.
INFORMATION DISSEMINATION
The research agenda outlined in Table 8-1 and described in detail in the chapters of this report has the potential to fill decision-critical gaps in information. This includes information needed by decision-makers charged with mitigating wildfire impacts and information needed by the public to minimize their exposure to WUI fire toxicants. To achieve this potential requires predictive tools, assessment capabilities, and exposure mitigation recommendations. Tools and assessment capabilities need to be applied rapidly, and information emerging from the tools and assessments will need to be synthesized into guidance in near real time.
This need is not unique to WUI fires. Systems have been developed for wildfires to provide information to decision-makers charged with mitigating fire impacts. The research community should build on these existing wildfire tools to provide information frameworks that incorporate the unique attributes of WUI fires.
For example, tools for decision-makers could include plume tracking that incorporates an understanding of the chemistry of WUI fires; it could include summaries of research results relevant to policies such as codes for construction materials used in WUI communities. Public dissemination of research findings could include activities such as expanding the information assembled in resources such as the federal government’s Ready campaign website (www.ready.gov/wildfires) to include the unique attributes of WUI fires. This could include public guidance on selecting materials used to build, renovate, or repair WUI homes, or the types of personal protective equipment that are effective against the toxicants generated by WUI fires and that could be included in personal readiness kits.
Recommendation 2: Those implementing research programs should design and implement a multidisciplinary WUI research program that includes the development of tools, resources, and messaging designed to inform a wide variety of decision-makers charged with mitigating wildland and WUI fire impacts. They should also create periodic summaries of policy-relevant research findings, and actionable messaging for decision-makers working with at-risk communities and vulnerable populations.
Policy-relevant research findings and actionable messaging could include recommendations for building materials to be used in WUI communities, public information regarding the effectiveness of measures to mitigate exposures, and community mappings of toxicant precursors, accessible to decision-makers.
More than 40 million homes in the United States are located at the WUI, in communities throughout the United States. Diverse and vulnerable populations will be increasingly exposed to hazards from WUI fires. The development of a multidisciplinary WUI research program, summarized in Table 8-1, will have long-term benefits, but immediate action is also needed. The committee identified a number of areas where rapid action could have immediate benefits. These areas are listed in Box 8-1 and were identified based on their ability to provide foundational information that plays a critical role in defining the scope of the broader research agends. Commitment to both long-term progress and immediate action on improving the understanding of WUI fires would benefit communities throughout the United States and the world.
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