Appendix A
Glossary
Acute exposure (Chapter 6): Contact with a substance that occurs once or for only a short time (acute exposure can occur for up to 14 days) compared with intermediate-duration exposure and chronic exposure
Acute health effect (Chapter 6): A health effect that develops immediately or within minutes, hours, or even days after an exposure
Ash (Chapter 3): The solid residue remaining after combustion, generally consisting of minerals and lesser amounts of char; ash may become lofted in the plume to become a component of PM
Atmospheric lifetime (Chapter 4): Average time a molecule of species i remains in the atmosphere
Bioavailability (Chapter 6): The potential for uptake (ability to be absorbed and used by the body) of a substance by a living organism; it is usually expressed as the fraction that can be taken up by the organism in relation to the total amount available
Biomass (Chapter 3): Organic material derived from plants or animals
Black carbon or soot (Chapter 3): A component of PM derived from high-temperature flaming processes; black carbon is composed of aggregates of carbon particles typically 20–40 nm in diameter
Char (Chapter 3): The solid residue remaining after combustion; char generally refers to carbonaceous residues with some minerals
Chronic exposure (Chapter 6): Continuous or repeated contact with a toxic substance over a long period of time (months or years)
Chronic health effect (Chapter 6): An adverse health effect resulting from long-term exposure to a substance; examples could include diabetes, bronchitis, cancer, or any other long-term medical condition
Coarse particulate matter (PM10) (Chapter 6): Inhalable particles with diameters equal to or less than 10 micrometers in diameter
Combustion efficiency (CE) (Chapter 3): The fraction of carbon in the fuel that is emitted as CO2
Combustion factor (CF) (Chapter 3): The fraction of combustible material exposed to a fire that was actually consumed or volatilized
Combustion zone (Chapter 2): Region in which air temperatures are sufficiently high to drive combustion chemistry
Community water system (CWS) (Chapter 5): A water system serving populations greater than 25 people, year round
Continental scale (Chapters 2, 3, 4, 6): Greater than 1,000 km, where chemistry is driven by processes that occur over days
Dissolved organic matter (DOM) (Chapter 5): A mixture of organic compounds found ubiquitously in surface and groundwaters; derived from terrestrial and aquatic sources
Dry atmospheric deposition (Chapter 4): The removal of particles and gases from the atmosphere to surfaces in the absence of precipitation (i.e., through gravitational settling, impaction, interception, and diffusion)
Emissions (or effluents) (Chapters 3, 5): Species emitted into the air, water, soil, or other media, from a process; these are sometimes called releases
Emission factor (EF) (Chapter 3): The mass of a specific compound (or class of compounds) emitted per kilogram of dry fuel combusted, for a specified dry material or collection of materials
Emission ratio (ER) (Chapter 3): The ratio of the mass of a compound emitted to the mass of a reference compound that is conserved in the plume, often CO or CO2; it is often reported as an “enhanced” ER where the background concentrations of the compound and reference compound have been subtracted
Enclosure fire (Chapter 3): A fire contained within a room or compartment inside a building in which oxygen supply is typically constrained, contrary to open fires; these are sometimes called compartment fires
Energy content (Chapter 3): The amount of energy contained within a mass of fuel; it can be quantified as the higher heating value (or gross calorific value), defined as the amount of heat released from complete combustion of a material when the products are returned to 25°C, or the lower heating value (or net calorific value), defined as the amount of heat released from complete combustion of a dry material initially at 25°C when water as a combustion product remains in the vapor state; other initial and final state temperatures may be found in the literature
Environmental justice (Chapter 6): A social movement developed in response to environmental racism; environmental justice research and practice involves identifying the disproportionate health burdens that populations experience from environmental exposures and social vulnerabilities, and focusing on solutions to alleviate those burdens in partnership with affected communities
Equivalence ratio (ϕ) (Chapter 3): The ratio of the actual fuel/oxidizer ratio to the stoichiometric fuel/oxidizer ratio; the stoichiometric fuel/oxidizer ratio is the ratio that is theoretically required to fully oxidize the fuel
Fine particulate matter (PM2.5) (Chapters 3, 4, 6): Airborne particles with diameters of 2.5 micrometers or less, small enough to enter the lungs and bloodstream, posing risks to human health
Fire plume (Chapters 2, 3, 4): Air mass downwind of combustion zone, containing elevated concentrations of combustion products
Flaming combustion (Chapter 3): Luminous oxidation of gases evolved from the rapid decomposition of a solid biomass fuel
Glowing combustion (Chapter 3): Incandescent heterogeneous oxidation of a solid biomass fuel in which all the volatiles have been driven off
Health equity (Chapter 6): Identifying health disparities between populations that are driven largely by social, economic, and environmental factors, and focusing on solutions to eliminate those disparities
Interface WUI (Chapter 2): Areas characterized by development (housing or other structures) located at the edge of a large area of wildland
Intermediate-volatility organic compounds (IVOCs) (Chapter 4): Compounds with vapor pressures between those of VOCs and semi-VOCs; a suite of compounds that, based on their vapor pressure, tend to evaporate from the particle phase with near-field dilution of plumes
Intermix WUI (Chapter 2): Areas characterized by alternating development (housing or other structures) and wildlands
Local scale (Chapters 2, 3, 4, 6): From 10 to 100 km, where chemistry is driven by processes that occur on a timescale of minutes to hours
Lower heating value or net calorific value (Chapter 3): amount of heat release from complete combustion of material not including the energy required to vaporize products
Modified combustion efficiency (MCE) (Chapter 3): The measured, enhanced emission of CO2 divided by the sum of the enhanced emission of CO and enhanced emission of CO2; MCE is typically linearly correlated with CE and used as a proxy for CE since it is easier to measure
Near-field scale (Chapters 2, 3, 4, 6): From 1 to 10 km downwind of the fire, where the plume remains quite concentrated, dilution has a major effect on the gas-particle partitioning, and chemistry is driven by fast processes that occur on a timescale of minutes
Oxidative pyrolysis (Chapter 3): The thermal decomposition of a combustible material in the presence of molecular oxygen in the surrounding atmosphere
Particulate matter (PM) (Chapters 3, 6): A complex mixture of solid particles and liquid droplets found in the air
Partitioning (Chapters 4, 5): The distribution of a species i between two media, such as air and particles, or air and water
Plume injection parameters (Chapter 3): The initial characteristics of a fire plume, including its injection altitude and multi-phase chemical composition
Pollutant (Chapters 3, 4, 5, 6): A chemical or biological substance that harms water, air, or land quality
Prescribed burn (Chapter 4): Fire set intentionally for forest or farmland management
Primary organic aerosol (Chapter 4): Organic particulate matter that is emitted from the source (e.g., WUI fire) in particulate form
Primary species with toxic potential (Chapter 4): Toxic substance that is emitted directly from the source (e.g., WUI fire)
Pyrolysis (Chapter 3): The thermal decomposition of a combustible material in the absence of molecular oxygen; the term “pyrolysis” sometimes appears in wildland fire literature to represent oxidative pyrolysis
Regional scale (Chapters 2, 3, 4, 6): From 100 to 1,000 km, where chemistry is driven by processes that occur on a timescale of hours to days
Secondary organic aerosol (Chapters 3, 4): Organic particulate matter that is formed in the atmosphere from precursor gases
Secondary species with toxic potential (Chapter 4): Toxic substances that are formed through atmospheric chemistry
Semi-volatile organic compounds (SVOCs) (Chapters 3, 6): Organic compounds that, based on their vapor pressure, tend to evaporate from the particle phase with near-field dilution of plumes; SVOCs are of concern because of their abundance in the indoor environment and their ability to accumulate and persist in the human body, the infrastructure of buildings, and environmental dust
Smoldering combustion (Chapter 3): Combined processes of thermal decomposition and slow, low-temperature, flameless burning of porous solid biomass fuels; sometimes called glowing combustion
Structural racism (Chapter 6): The totality of ways in which societies foster racial discrimination through mutually reinforcing systems of housing, education, employment, earnings, benefits, credit, media, health care, and criminal justice; these patterns and practices in turn reinforce discriminatory beliefs, values, and the distribution of resources
Toxic (Chapter 6): Related to harmful effects on the body by either inhalation (breathing), ingestion (eating), or dermal absorption of the chemical
Toxic product yield (Chapter 3): The maximum possible mass of a combustion product generated during combustion, per unit mass of test specimen consumed (typically expressed in units of grams per gram or kilograms per kilogram)
Toxicant (Chapters 5, 6): Any chemical that can injure or kill humans, animals, or plants (depending on the magnitude and duration of exposure); a poison
Ultrafine particles (Chapter 6): Particles with a diameter less than or equal to 0.1 micrometers
Urban fire (Chapter 3): Fire that occurs primarily in cities or towns with the potential to rapidly spread to adjoining structures; these fires mostly damage and destroy homes, schools, commercial or industrial buildings, and vehicles
Volatile organic compounds (VOCs) (Chapters 3, 4, 5, 6): Organic compounds with vapor pressures high enough to exist in the atmosphere primarily in the gas phase, typically excluding methane; VOCs can easily become airborne for inhalation exposure
Vulnerable populations (Chapter 6): Individuals or communities at higher risk of adverse health effects from exposures, such as from greater pollutant exposure concentrations, higher health response to a given level of exposure, or reduced capacity to adapt
Wet atmospheric deposition (Chapter 4): The removal of particles and gases to the earth’s surface via scavenging by precipitation
Wildfire: Although in common usage, the term wildfire is not used in this report; a wildfire is generally defined as a wildland fire originating from an unplanned ignition, such as lightning, volcanos, unauthorized and accidental human-caused fires, and prescribed fires that are declared wildfires
Wildland fire: Any non-structure fire that occurs in vegetation or natural fuels; includes wildfires and prescribed fires
Wildland-urban interface (WUI): The community that exists where humans and their development meet or intermix with wildland fuel
