Wildfire

Wildfire smoke is a complex mixture of water vapor, gases, and particles. These particles, also called particulate matter (PM), consist of a mixture of solid particles and liquid droplets that are suspended in the air). Particles may be either directly emitted by a wildfire or formed through complex atmospheric reactions of other chemicals emitted by wildfires, including sulfur dioxide or nitrogen dioxide. Of the pollutants in wildfire smoke, fine particulate matter (PM_2.5), or particles with an aerodynamic diameter less than or equal to 2.5 µm, is of greatest health concern. These particles can be inhaled into the body and travel to the lungs. Some particles can even enter the blood, where they can travel throughout the body and affect other organs.

Decades of research on ambient PM_2.5 concentrations (i.e., air quality people experience during a typical day), and more recent studies of wildfire smoke when PM_2.5 concentrations are elevated, show that short-term (or daily) PM_2.5 exposure is associated with health effects. These range from eye and respiratory tract irritation to reduced lung function, bronchitis, exacerbation of asthma, heart failure, and even death. The health effects of long-term smoke exposure (i.e., weeks or months of exposure or repeated exposure over multiple years) currently remain unclear, but there is some initial evidence for changes in lung function, increased risk of respiratory infection, and adverse birth outcomes. Most healthy adults and children will recover quickly from short-term smoke exposure, but people at some life stages and some populations may be at greater risk of experiencing health effects.

Source: Kathleen M. Navarro, Michael T. Kleinman, Chris E. Mackay, Timothy E. Reinhardt, John R. Balmes, George A. Broyles, Roger D. Ottmar, Luke P. Naher, Joseph W. Domitrovich, Wildland firefighter smoke exposure and risk of lung cancer and cardiovascular disease mortality, Environmental Research, Volume 173, 2019, Pages 462-468, ISSN 0013-9351, https://doi.org/10.1016/j.envres.2019.03.060.

One study funded by the Joint Fire Science Program found that wildland firefighters are at an increased risk for the development of lung cancer (8 percent to 43 percent above the general population) and cardiovascular disease (16 percent to 30 percent above the general population). This risk increases with an increase in career duration and days spent on wildfire incidents (short and long season) each year. The risk of lung cancer steadily rose as career length, while the risk of cardiovascular disease increased sharply for firefighters with 5- to 15-year careers and increased slightly over 20- and 25-year careers. As fire seasons continue to increase in severity and duration, firefighters should reduce exposure to smoke in any way possible.

Figure: This infographic from US Forest Service Research and Development illustrates wildland fire smoke transport and dispersion. 

Smoke from wildfires in Canada caused significant air quality issues for millions in the Northeast and Great Lakes in the summer of 2023. Around 100 million people across 16 states were under air quality alerts from this smoke and it led to New York City and Chicago reporting the worst air quality of major cities in the world.

Figure: Example of the AirNow Fire and Smoke Map run by U.S. EPA and the U.S. Forest Service. This screenshot, from September 15, 2020, shows the far distances smoke can travel from the location of wildfires. The map also shows the U.S. Air Quality Index (AQI) from hundreds of air quality monitors and more than 10,000 privately owned air sensors. Green symbols indicate a good AQI; yellow indicates moderate; orange indicates unhealthy for sensitive groups; red indicates unhealthy for everyone; and purple indicates very unhealthy. The flame symbols indicate a large fire incident, and the small yellow spark symbols indicate unverified satellite fire detections.

Wildfire smoke can impact the health of people close to the fire and at distances far from fire impacted areas, depending on meteorological conditions, such as wind speed and direction. As wildfires burn, they generate smoke that is comprised of a mixture of particulate matter (PM) (also referred to as particle pollution) and gaseous pollutants (e.g., carbon monoxide). The pollutant of most concern to public health during a smoke event is fine particulate matter, or PM2.5, because these particles can penetrate deep into your lungs and cause adverse health effects.

In our June edition, we shared information on farmworkers’ inequitable exposure to wildfire smoke. Since then, CDC’s National Institute for Occupational Safety and Health (NIOSH) released a draft Hazard Review: Wildland Fire Smoke Exposure Among Farmworkers and Other Outdoor Workers in the Federal Register for public comment and technical review. This draft Hazard Review is the first federal-level authoritative document with a focus on wildland fire smoke for outdoor workers. It will increase awareness about the overall risk of exposure to wildland fire smoke on outdoor worker health.

This draft Hazard Review aims to provide a comprehensive review of the available science and recommendations to address the potential hazards for outdoor workers exposed to wildland fire smoke. NIOSH estimates that approximately 20 million outdoor workers in the U.S. were potentially exposed to wildland fire smoke in 2023. The draft Hazard Review addresses the risks faced by these outdoor workers exposed to wildland fire smoke, such as farmworkers and construction workers. NIOSH proposes recommendations to reduce outdoor worker exposures through a hierarchy of controls approach. This approach includes prioritizing engineering controls (such as air filtration), then administrative controls (such as altering work schedules), and finally, personal protective equipment. NIOSH suggests using the EPA's Air Quality Index to assess PM2.5 levels to determine the severity of exposure and necessary controls.

The document can drive the development of new, innovative control options and may stimulate new research and inform policies that better protect outdoor workers from the growing threat of wildland fire smoke exposure. Public comments on the draft document have been extended and will be accepted through January 10, 2025. NIOSH will convene a webinar on Tuesday, December 3, 2024, at 1:00 PM Eastern Time (U.S. and Canada) to present an overview of the draft Hazard Review and provide information about the public comment period. Attendees should register in advance for this webinar.

Figure. This graph overlays the percentage of Emergency Department (ED) visits due to asthma or reactive airway disease (RAD) in San Mateo County during the 2018 Camp Fire. It uses Morbidity and Mortality Weekly Report weeks, which begin with 1 for the first week of the year. Each red dot indicates an instance where the percent of ED visits due to asthma or RAD is exceptionally high. You can learn more on the CDC’s website.

As wildfires continue to threaten the public’s health across the country, agencies are demonstrating the utility, reliability, and timeliness of syndromic surveillance data for monitoring and characterizing health impacts. During the first two weeks of the 2018 Camp Fire in California, there were higher-than-expected increases in 24-hour particulate matter (PM2.5) concentrations in San Mateo County, which reached unhealthy levels. San Mateo County public health officials monitored for acute respiratory health effects and, in collaboration with the CDC National Syndromic Surveillance Program and the California Department of Public Health, they demonstrated an increase in the weekly percentage of ED visits for asthma or reactive airway disease (RAD) exacerbation, and an increase in the number of visits for smoke exposure or smoke inhalation. Among participating EDs, the county’s safety net hospital had the highest average daily percentage of ED visits for all respiratory syndromes, excluding influenza-like illness and pneumonia.

Wildfires are occurring more frequently across the U.S., exposing more Americans to wildfire smoke. Wildfire smoke is composed of complex mixtures of toxic gasses and particulate matter, including PM_2.5. Exposure to elevated levels of PM_2.5 is associated with negative health effects including eye and respiratory tract irritation, exacerbation of respiratory conditions, heart failure, and even death, especially for outdoor workers and other at-risk groups of people.

Wildfire smoke is hard to predict and can persist in areas for long periods of time, placing outdoor workers, including agricultural workers, at elevated risks of exposure. Since wildfire smoke often comes along with heat waves, outdoor workers are regularly exposed to both hazards simultaneously, compounding their health risks. Recent studies showing a predicted 35% increase in worker smoke exposure days for agriculture workers in the Central Valley of California by 2050 and the high correlation between high heat index days and large peaks in PM_2.5 exposure emphasize the urgency of protecting agricultural workers from these cumulative climate hazards.

There are an estimated 2.9 million agricultural workers in the U.S. with the majority identifying as Hispanic and/or born outside of the U.S. The creation of culturally and linguistically appropriate training and resources related to wildfire smoke protection can help migrant and seasonal agricultural workers protect themselves from the dangers of smoke exposure. Important preventative measures for agricultural workers, as well as all outdoor workers, include providing masks or respirators that filter out PM_2.5 particles during wildfire smoke events, and providing water, shade, and breaks during the working day to limit dehydration.

Farmworkers harvest lettuce in Salinas, CA despite wildfire smoke-filled air in August 2020. Image source: Migrant Clinicians Network.

The Pediatric Environmental Health Specialty Units (PEHSUs) are a federally funded national network of experts in the prevention, diagnosis, management, and treatment of health issues that arise from environmental exposures in children. The PEHSU network is managed by the American Academy of Pediatrics and follows a regional model, with a PEHSU in each of the 10 HHS regions.

When wildfire smoke from Canada blanketed the East Coast in early June 2023, the Region 2 PEHSU located in New York City at the Icahn School of Medicine at Mount Sinai quickly disseminated information about the health impacts of wildfire smoke on children and ways to reduce exposure. They collaborated with PEHSU regions out west that have more experience with wildfire events, as well as with local partners at the New York State Children’s Environmental Health Centers network and the National Institute for Environmental Health Sciences research centers both at Mount Sinai and nationally, allowing them to tailor existing messaging to meet local needs and rapidly provide resources. 

The Region 2 PEHSU collaborates closely with the New York City Department of Health and Mental Hygiene, which provides syndromic surveillance data on asthma cases. On June 7th, when the wildfire smoke was at its worst, these data showed about 100 more asthma emergency department visits than expected for this time of year, similar in magnitude to the increase seen during high pollen days. These data help to quantify the impacts of exposure to hazards like wildfire smoke and pollen, which are anticipated to worsen as climate change continues.

Wildfire smoke exposure is particularly harmful for children, who breathe more air relative to their size and are more active than adults. The PEHSU network’s rapid response to provide families with information about safeguards for their children is a great example of how the environmental health community collaborates in real time to protect the health of a particularly vulnerable population during a hazard event.

The 2021 California Health Interview Survey asked a representative sample of Californians about their health impacts from climate change. Forty-five percent of California adults reported experiencing a hazardous weather-related event in the past two years (i.e., heat wave, flooding, wildfire, smoke from wildfire, or public safety power shutoff). Of those, 17 percent said their physical health was harmed by these events and 22 percent said their mental health was harmed. The survey also asked teens (age 12-17) about the impact of climate change on their mental health, and 38 percent, said the issue of climate change makes them feel nervous, depressed, or emotionally stressed (figure to the right shows percentages by demographic groups). This effect was more commonly reported among female teens than male teens. Learn here about how the California Department of Public Health’s Climate Change and Health Equity Section is working to advance health equity through climate action.

Figure: U.S. wildfire statistics from the National Interagency Fire Center (NIFC) for January 2000–December 2023 in the contiguous U.S.

Across the contiguous U.S., 56,580 wildfires were reported in 2023, which is close to the 10-year average (2013–2022). These wildfires burned nearly 2.7 million acres of land, which is well below the 10-year average. Notably, close to 300,000 acres burned in Alaska, which is less than half of the state’s seasonal average. In Hawai’i, the island of Maui experienced the deadliest wildfire in the U.S. in over a century. An official County of Maui website contains vital information for those affected by the fires and FEMA provides guidance on how to help those recovering.

During 2023, wildfire smoke traveled hundreds of miles and affected air quality in communities across the country. In a new Morbidity and Mortality Weekly Report, investigators at CDC and EPA analyzed data from April 30 through August 4, 2023, to assess the extent to which smoke from the wildfires in Canada resulted in asthma-associated emergency department (ED) visits in the United States. Overall, ED visits for asthma were 17% higher than expected during 19 days of wildfire smoke. Higher-than-expected asthma-associated ED visits were observed among people of all ages, but the highest increase was among people 5–64 years-old. The largest increase in asthma-associated ED visits occurred in HHS Region 2, which includes New York and New Jersey. The observed increase in asthma ED visits highlights the need to reduce smoke exposure during wildfires and can help guide emergency response planning and public health communication strategies, especially in U.S. regions where wildfire smoke was previously uncommon. The findings suggest that clinicians can consider counseling patients about protective measures, including awareness of current and predicted air quality conditions, staying indoors, using air filtration, and using properly fitted N95 respirators when outdoors. These measures are especially important for people with asthma, chronic obstructive pulmonary disease, and for children, older adults, and pregnant people.

In June 2008, smoke from a peat bog wildfire billowed into the atmosphere and fouled the air in rural parts of eastern North Carolina, impacting the daily lives and health of over a million people. A peat bog is a wetland with decomposing plant remains. In drought conditions, peat bogs are exceptionally susceptible to wildfires that are difficult to extinguish and produce large amounts of smoke. The rising temperatures and more frequent drought associated with climate change coupled with damage from exploitation of peat bogs for energy increase the risk of peat fires.

U.S. EPA researchers, along with state and academic collaborators, evaluated air quality impacts from the North Carolina 2008 peat bog wildfire and found that wildfire-impacted counties experienced significant increases in Emergency Department (ED) visits for cardiopulmonary outcomes including chest pain, asthma, chronic obstructive pulmonary disease, pneumonia, heart failure, and acute bronchitis. The counties most highly exposed to wildfire smoke were largely rural with a higher percentage of African Americans and people of lower socioeconomic status (SES) than in other North Carolina counties. Another analysis using County Health Ranking data reported a difference in the risk of ED visits between bottom and top ranked counties by SES factors for asthma and congestive heart failure.    

Complimentary EPA toxicological studies analyzed smoke samples from this peat bog wildfire during two burn phases: actively smoldering versus nearly extinguished. Researchers found that coarse particulate matter (PM) from the two burn phases had similar chemical composition while the composition of fine and ultrafine PM differed between phases. In a mouse study, researchers found that ultrafine particles affected the heart, whereas coarse particles affected the lung, with more pronounced effects for particles from the smoldering phase. Together, these studies suggest that different size particles from the same air shed could adversely affect the cardiovascular and respiratory systems. 

Discover your community's relative risk for wildfires when compared to the rest of the U.S. via FEMA's Wildfire National Risk Index Score. The Ready.gov Wildfires site, Centers for Disease Control and Prevention (CDC) Wildfires site, and Environmental Protection Agency (EPA) Smoke-Ready Toolbox for Wildfires include information about how to prepare for wildfires, stay safe during a fire, and return home after a fire.

The AirNow Fire and Smoke Map, a joint project of EPA and the U.S Forest Service, provides information on fire locations, smoke plumes, and air quality, using the color-coding of the Air Quality Index (AQI), along with recommended actions to take to reduce smoke exposure. The AirNow Wildfires site provides additional information on steps to protect your health. The Map is also available in the AirNow app. NOAA also provides daily maps and outlooks for wildfires in the U.S.

Download the Federal Emergency Management Agency (FEMA) App to receive real-time weather and emergency alerts from the National Weather Service.  The App can also help you find a nearby shelter if you need to evacuate to a safe space. You can also text SHELTER and your ZIP code to 43362 (e.g. Shelter 12345) to find up to emergency shelters or FEMA Disaster Recovery Centers nearby.

If you do not have health insurance and are in a federally-identified disaster, the Emergency Prescription Assistance Program can help you get the prescription drugs, vaccinations, medical supplies, and equipment that they need.

If you have Medicare and your medical device is damaged or lost due to an emergency or disaster, Medicare may cover the cost to repair or replace your equipment or supplies.

You can locate and access your electronic health records from a variety of sources by using the U.S. Department of Health and Human Services' online tool.

Smoke Sense is a crowdsourcing, participatory science research project developed by EPA researchers focused on increasing public awareness and engagement related to wildfire smoke health risks.

Image source: https://www.epa.gov/sites/default/files/2014-09/howbigpm.jpg

Most healthy adults and children will recover quickly from short-term smoke exposure, but people at some life stages and some populations may be at greater risk of experiencing health effects. These include children, who inhale more air per pound of body weight than adults and have immature immune systems, older adults, people with chronic disease (i.e., asthma and other lung diseases, and cardiovascular disease), and pregnant people. In addition, some people may experience greater smoke exposures due to economic, social, environmental, and other factors that impact their ability to reduce smoke exposure. These include disabled people, people from minority and low-income communities, and outdoor workers.

Pregnant people should take actions to reduce their exposure to wildfire smoke, which could affect the developing fetus. Other groups like young children, the elderly, those with pre-existing heart and lung disease, and outdoor workers also should take extra care to reduce their exposures to wildfire smoke. Monitor fires and air quality in your area through AirNow and follow instructions about exercise and going outside for "sensitive individuals."

Additional steps you can take to prepare include stocking up on medicine and buying groceries that don’t need to be cooked. In particular, frying or grilling food can make indoor air pollution worse. More information is available for older adults, people experiencing homelessness, people with access and functional needs, people with disabilities, people with chronic conditions, pregnant people , and children.

The California Air Resources Board Air Cleaner Information for Consumers has information about how to select a safe and effective air cleaner. Exercise caution in using air-cleaning devices in the home; some can produce ozone levels that are higher than health-based standards. The Environmental Protection Agency (EPA) also has information on how to Create a Clean Room to Protect Indoor Air Quality During a Wildfire and the California Air Resources Board has information on Protecting Yourself from Wildfire Smoke.

Image source: https://ww2.arb.ca.gov/protecting-yourself-wildfire-smoke

Feelings such as overwhelming anxiety, constant worrying, trouble sleeping, and other depression-like symptoms are common responses before, during, and after wildfires. The Substance Abuse and Mental Health Services Administration (SAMHSA) Helpline and Text Service is available 24/7, free, and staffed by trained crisis counselors. Call or text 1-800-985-5990 to get help and support for any distress that you or someone you care about may be feeling related to any disaster.

Learn more about wildfires and mental health at the SAMHSA’s Wildfires site. SAMHSA also has other disaster behavioral health resources, including resources specifically about wildfires and their impacts on mental health. The CDC also has resources in English and Spanish on Coping with a Disaster or Traumatic Event.

Check out SAMHSA’s newly launched Climate Change and Health Equity site for more information on the behavioral health impacts of climate change, preparing for a disaster, and resources for disaster planning and climate change education.

The Administration for Strategic Preparedness and Response Technical Resources, Assistance Center, and Information Exchange (ASPR TRACIE) has collected lessons learned on Wildfires. An HHS emPOWER Program Story from the Field on Wildfires in Los Angeles County, California briefly explains how HHS emPOWER tools were used to rapidly conduct outreach to nearly 40 durable medical equipment (DME) and oxygen suppliers to provide recovery assistance to more than 600 individuals impacted by the historic 2017 wildfires.

Smoke-Ready Communities is an EPA and U.S. Forest Service Collaboration that is built around a series of interactive workshops and is designed to increase local readiness and improved public health response to wildfire smoke events.

Wildfire Smoke: A Guide for Public Health Officials -- the product of an inter-agency collaboration that includes the California Air Resources Board; California Office of Environmental Health Hazard Assessment; CDC; U.S. Forest Service; and EPA -- is designed to help local public health officials prepare for smoke events, to take measures to protect the public when smoke is present, and communicate with the public about wildfire smoke and health.

The CDC produced a summary for health departments on Evidence on the Use of Indoor Air Filtration as an Intervention for Wildfire Smoke Pollutant Exposure. For commercial buildings, the ASHRAE Planning Framework for Protecting Commercial Building Occupants from Smoke During Wildfire Events provides recommended heating, ventilation, and air conditioning (HVAC) and building measures to minimize occupant exposures and health impacts from smoke.

Workers face hazards even after fires are extinguished. The CDC’s Worker Safety During Fire Cleanup Fact Sheet reviews potential dangers during post-wildfire cleanup.

The HHS emPOWER collects and shares de-identified Medicare data to help response agencies take action to protect the health of Medicare beneficiaries who depend on vulnerable electrical medical equipment.

Wildland fire presents unique challenges and fire fighters must understand how to best protect their health and safety while fighting fires. Wildland Fire Fighting: Hot Tips to Stay Safe and Healthy reviews some recommended practices for fire fighters and their supervisors. Wildland Firefighter Health: Some Burning Questions offers information on hazards and risks associated with the wildland firefighting job.

Wildland fire fighting involves exposure to heat and prolonged, intense exertion. These factors increase the risk for rhabdomyolysis. The CDC Rhabdomyolysis site has additional information, factsheets, and wallet cards.

Important preventative measures for outdoor workers include providing masks or respirators that filter out PM_2.5 particles during wildfire smoke events, and providing water, shade, and breaks during the working day to limit dehydration. NIOSH also has further information on protecting outdoor workers from wildfire smoke.

Workers face hazards even after fires are extinguished. The CDC’s Worker Safety During Fire Cleanup Fact Sheet reviews potential dangers during post-wildfire cleanup.

OCCHE’s Referral Guide summarizes resources that can address patients’ social determinants of health and mitigate health harms related to climate change. These resources include social services and assistance programs to which patients can be referred, as well as references for anticipatory guidance and counseling to help patients prepare for potential hazards.

The EPA and CDC continuing education program Wildfire Smoke and Your Patients’ Health  can also help educate healthcare professionals about the health effects of wildfire smoke and highlights actions that individuals can take to reduce exposure. This printable card contains additional information about the course.