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Wildfire and Wildfire Smoke

Wildfire is an unplanned, uncontrolled fire burning in a natural area. Wildfires can directly cause immediate human casualties and displacement of affected communities, and indirectly produce high levels of air pollution, which can influence the respiratory and cardiovascular health of the immediate community and distant regions, alike.
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Transcript: Hi, I’m Wildfire Smoke. Although you may not live near a wildfire, I most likely have impacted your health in the last few years. I’m a relative of PM2.5 so I can travel near and far. I’m complex. Beyond the immediate stress of a fire. Wildfire smoke is a mix of particles, gases, and water vapor. I include carbon monoxide, nitric oxides, and volatile organic compounds. Wildfires result in displacement, but my presence can result in PM2.5 levels exceeding some of the most polluted cities. When outside, you can breathe in these particles but if you are in a poorly ventilated building, I can settle in the dust and get on your skin or be ingested. My impact can be both mental and physical: from increased levels of stress to poor respiratory and cardiovascular health outcomes. I can exacerbate asthma. It may seem like the science of the invisible but without attention it can have lasting impacts. Wildfires result in increased air pollution, physical damage, loss of agriculture and destruction of our built environment. Vulnerable populations suffer disproportionate exposure to catastrophic loss from wildfire. Due to rising housing costs, low-income families are having to move to outer areas, where human communities and forests, shrublands, or grasslands intermingle, making the risk for wildfire especially high. Living with poverty, disability or language barriers make absorbing this risk particularly difficult.


Areas deemed susceptible to wildfires are defined by US Federal Emergency Management Agency (FEMA) as having burn potential and possibility of fires reaching greater intensity. This can be unplanned and uncontrolled fire in natural or wildland areas.

Human Health Mechanism

Wildfires, characterized by their rapid spread and intense heat, not only lead to immediate human casualties and the displacement of affected communities but can also produce extraordinarily high levels of air pollution that surpass those found in some of the world’s most heavily polluted urban areas, posing severe health risks to both the immediate and surrounding regions.

Indicator Measurement

The US FEMA National Risk Index calculates a Wildfire Risk Index score to represent a community’s relative risk for wildfires when compared to the rest of the US.  A Wildfire Risk Index score is based on the sum of expected building and population loss each year due to wildfires and is derived by identifying census blocks with developed or agricultural areas with elevated potential for ignition and/or elevated possibility of high intensity fires.

Source of Exposures

Wildfire smoke is a complex mix of particles, gasses (e.g. carbon monoxide, nitric oxides, and volatile organic compounds) and water vapor.

Related Health Outcomes & Exposures

Stress, Respiratory Health, Cardiovascular Health, Displacement


Click here for References
  1. Wildfire Data Source: Climate Mapping for Resilience and Adaptation (CRMA). US FEMA National Risk Index: Wildfire. Data year 2021. Accessed April 2023.
  2. Adetona O, Reinhardt TE, Domitrovich J, et al. Review of the health effects of wildland fire smoke on wildland firefighters and the public. Inhal Toxicol. 2016;28(3):95-139. doi:10.3109/08958378.2016.1145771
  3. Brauer M, Johnston FH, Jerrett M, Balmes JR, Elliott CT. Critical Review of Health Impacts of Wildfire Smoke Exposure. Environ Health Perspect. 2016;124(9):1334-1343. doi:10.1289/ehp.1409277
  4. Lambrou N, Kolden C, Loukaitou-Sideris A, Anjum E, Acey C. Social drivers of vulnerability to wildfire disasters: A review of the literature. Landscape and Urban Planning. 2023;237:104797. doi:10.1016/j.landurbplan.2023.104797
  5. US FEMA. National Risk Index: Wildfire. Accessed November 10, 2023.
  6. World Health Organization (WHO). Wildfires. Published 2022.