Rising Health Impacts of Wildfire Smoke Exposure

As is evident in California, recent years have seen wildfires pose increased threats to health. Climate change has been linked to multiple conditions that favor more fire, including earlier and lessened snow melt, changing precipitation patterns, altered wind patterns, insect infestation, and increasing vapor pressure deficit. Wildfire risk is projected to continue to increase. By the middle of the century, the number of days of exposure to very high or high wildfire risk is expected to increase by 11%. The absence of government commitment and health system mobilization does not keep these wildfires from occurring. Therefore, our preparation will be key.

The environmental impacts of wildfire include air quality degradation, climate change, a loss of biodiversity, and soil and water quality issues, thus affecting aspects of social, economic, and human health. Wildfire smoke can travel thousands of miles, affecting the air quality in regions far from the fire source. This smoke contains particulate matter (PM), carbon monoxide, and other toxic pollutants that can harm human health and ecosystems. Wildfires also release significant amounts of carbon dioxide (CO2) and other greenhouse gases, contributing to more global warming. The loss of forests reduces the planet’s capacity to sequester carbon. Fires can destroy habitats and threaten the survival of species. The recovery of ecosystems can take decades, and some species may face extinction. The removal of vegetation can lead to soil erosion and the loss of nutrients. Ash and debris can contaminate water sources, affecting aquatic life and human water supplies. Fire scars are more prone to flooding and landslides caused by climate induced strong atmospheric rivers.  

Patients and emergency responders near fires are at risk of burns, injuries, motor vehicle accidents, death, smoke inhalation, exposure to water and land contamination, landslides, uncommon infections, and mental health issues. In those with trauma and burns resulting from direct exposure to wildfires, some studies show that invasive resistant bacteria and fungi are more prevalent both in skin infections and in respiratory events.  For example, Coccidiomycosis was increased after the California wildfires in 2014-2018.

Wildfire smoke is a complex and dynamic mixture of pollutants, being made up of both gases and particles. The primary gases emitted by wildfires include carbon monoxide, ammonia, oxides of nitrogen, volatile organic compounds, and polyaromatic hydrocarbons. These gases then inter-react with each other and the atmosphere to form secondary gases, particularly ground-level ozone. However, particle pollution represents a main component of wildfire smoke and the principal public health threat. Individuals at greater risk of health effects from wildfire smoke include those with cardiovascular or respiratory disease, older adults, children under 18 years of age, pregnant women, outdoor workers, and those of lower socio-economic status.  Even in healthy people, exposure to fine particles can potentially lead to transient reductions in lung function, and pulmonary inflammation. WHO says globally, climate change could be responsible for 60,000 air pollution-linked premature deaths in 2030 under current emission trends. In the United States, climate-driven wildfire smoke is projected to cause 76% more annual premature deaths and $244 billion in economic losses by 2050, compared to 2011–2020. The cost of recent California fires is growing daily.

A growing body of epidemiological evidence suggests that wildfire-derived particulates (PMs) are associated with a variety of symptoms (e.g., respiratory and ocular symptoms) and health outcomes (e.g., cardiorespiratory diseases), birth outcomes, and skin inflammation.  Toxicology studies discovered that inhaled wildfire PMs deposited in the lungs or entering the bloodstream cause intense systemic inflammation and oxidative stress, leading to pulmonary and vascular dysfunction and contributing to the development of cardiorespiratory diseases.  Inhaled PMs disrupt the autonomic nervous system, which has also been linked to cardiovascular issues. Existing research suggests that oxidative stress and inflammation are key mechanisms through which PM2.5 causes multiorgan damage. (see ACOI newsletter Sept 2024).

Wildfire smoke exposure also contributes to the development of immune-related diseases.  Some of the harmful substances found in wildfire smoke can also bind to DNA, causing damage, genetic mutations, and cancer.  

Wildfires have short-term and long-term psychological effects on affected people, first responders, and the public at large. Within 3–6 months of wildfires, 24–60% of adult survivors might experience symptoms of post-traumatic stress disorder, 25–33% might experience major depressive disorder, and 25–33% might have anxiety disorders. Wildland firefighters have a 55% increase in suicidal ideation within the year of fighting a fire.  Although psychological distress tends to wane over time, symptoms can persist for years after a fire disaster.  

Your patients who are at risk for health effects due to wildfire smoke should be especially concerned about particles that are 10 micrometers (µm) in diameter or smaller because these are the particles that generally pass through the nose and throat and enter the lungs, with the smallest particles (< 2.5 µm) possibly even translocating into circulation. This group of particles also includes ultrafine particles, which are generally classified as having diameters less than 0.1 µm.

If you practice in an area that is prone to wildfires or smoke events, or if the National Interagency Fire Center has issued a National Significant Wildland Fire Potential Outlook indicating the potential for significant fires in your area, it’s important to help your patients be prepared to reduce their exposure to smoke.  Because physicians have a high degree of credibility with the public, consistent messaging reinforces the importance of preventative measures and actions to take during a wildfire to reduce exposure, the health care team can access these for local points of contact, responsibilities of state agencies and other partners, and instructions for acquiring extra resources such as monitors or masks. State and local health departments are also good resources, even when there is no formal emergency smoke response plan. This is especially important now that vital national input has been lessened.  

One resource that can provide you with information to educate your patients is Wildfire Smoke: A Guide for Public Health Officials (Wildfire Guide) . Factsheets created for public use can be found on the AirNow website and the thoracic association has a handout for patients.  

References:

https://www.thoracic.org/patients/patient-resources/resources/wildfires.pdf

https://www.airnow.gov/wildfire-smoke-guide-publications/

https://ehp.niehs.nih.gov/doi/10.1289/ehp.1409277

For Wildfire Tip sheet: https://www.americares.org/wp-content/uploads/WildfireActionPlanTipSheet_FINAL.pdf  

Note: The views expressed in this article are the author’s own and do not necessarily represent the views of ACOI.