Smoke — and the health of firefighters

smoke pyrocumulus bushfires Australia
Photo of smoke from bushfires by Merrin Macleod on a flight from Canberra to Melbourne, Australia, posted January 4, 2020.

Originally published by the Centers for Disease Control and Prevention

While research has not yet been conducted on all the hazards and risks associated with the wildland firefighting job, the National Institute for Occupational Safety and Health (NIOSH) is asked numerous questions about the hazards of fighting wildland fires. This blog is designed to answer some of those questions.

What Is in Wildland Fire Smoke?

Wildland fire smoke is a mixture of gases and particles such as carbon monoxide (CO) and respirable particulate matter (PM) that may cause short- and long-term health effects. Wildland firefighters can be exposed to smoke at wildfires and “prescribed” fires (planned and intentionally ignited low-intensity fires). The contents of and exposure to wildfire smoke can vary greatly throughout the day depending on the vegetation type, fire behavior, and meteorological conditions. Research has shown that wildland firefighters have been exposed to gases and particles such as CO and PM above the occupational exposure limits during both wildland and prescribed fires. While burning vegetation is the primary exposure of concern for wildland and prescribed fires, when fires burn in the wildland urban interface (WUI, where wildland vegetation and urban areas meet) the smoke may contain compounds that are more similar to what structural firefighters encounter. Wildland firefighters will often suppress these fires and may be exposed to some of the hazardous compounds of WUI smoke such as volatile organic compounds (VOCs), flame retardants, and polycyclic aromatic hydrocarbons (PAHs). However, wildland firefighters do not have the benefit of wearing some of the personal protective equipment (PPE) typically used in a structural response (e.g., self-contained breathing apparatus [SCBA], turnout gear) that could provide protection from these compounds. Additionally, wildland firefighters may be exposed to smoke at firefighting base camps (incident command posts) where they eat and rest while off-duty.

What Do We Know About the Health of Wildland Firefighters?

Cardiovascular and Lung Health

In the past decade, several studies have linked exposure to wildfire smoke to short-term health effects, such as increases in inflammation and respiratory effects, for example, lung function decline.[i] However, these studies have only examined the health effects across a few shifts or a single fire season. It is not clear if these adverse health effects continue after fire season and whether they worsen after several seasons of fighting fires. Researchers suspect that exposure to particulate matter and other contaminants from wildfire smoke, heavy physical exertion, existing health and behavior risk factors, and cardiovascular strain could contribute to sudden cardiac events for wildland firefighters. Recent research indicated that wildland firefighters may be at an increased risk of mortality from cardiovascular disease and lung cancer than the general public from career exposure to wildfire smoke.[ii]


The strenuous work, long work shifts, close living and working conditions, limited access to hygiene supplies, and a workforce that responds to incidents all over the country on short notice to wildland fire incidents may be conducive for the transmission of infectious diseases, including SARS-CoV-2. Exposure to air pollutants in wildfire smoke can irritate the lungs, cause inflammation, alter immune function, and increase susceptibility to respiratory infections, possibly including COVID-19.[iii] In addition to potentially making firefighters more vulnerable to getting COVID-19, inflammation in the respiratory tract due to wildfire smoke might also increase the risk of developing more severe outcomes for those with COVID-19.[iv] Wildland firefighters should implement the recommendations described in the CDC’s FAQ for Wildland Firefighters to prevent infection and spread of COVID-19.

Heat-Related Illness and Rhabdomyolysis

Due to the nature of their work, firefighters are at risk of developing severe heat-related illness (such as heat stroke) and rhabdomyolysis (muscle breakdown).[v],[vi] Delays in diagnosis and initiating treatment of these illnesses increase the risk of permanent muscle damage. Since 2010, 62 cases of severe rhabdomyolysis among wildland firefighters have been reported to a passive surveillance system designed to capture fatalities and certain types of injuries and illnesses including rhabdomyolysis. The actual number of cases is likely higher due to underreporting and inconsistencies in reporting requirements and systems. Prior to 2010, no cases were reported.


Wildland firefighters work around power tools and heavy equipment that produce noise levels that are hazardous to hearing. In addition to hearing loss, noise exposure may also cause tinnitus (ringing/buzzing in ears), increased heart rate, fatigue, and interfere with verbal communication. Researchers from NIOSH and the United States Forest Service (USFS) evaluated personal noise measurements on 156 wildland firefighters conducting various training and fire suppression tasks, and reported that 85 of the 174 measurements were above the NIOSH maximum allowable daily dose[vii]. A follow-up study showed use of hearing protection was mixed; while almost all the wildland firefighters were aware of the noise in their environment and potential risk, very few were enrolled in hearing conservation programs.

What Are NIOSH Researchers Doing to Better Understand Exposures and Health Effects?

NIOSH is currently conducting research to understand the exposures and health effects of firefighters suppressing wildland and WUI fires. NIOSH researchers and collaborators at the US Forest Service and Department of the Interior have finished the second year of a multi-year study investigating exposures and health effects among six federal 20-person firefighting crews. The primary goal of this study is to measure exposures in the wildland fire environment and examine associations between those exposures and changes in lung, cardiac, kidney, and hearing function during each fire season and the off season over multiple fire seasons. This study has been paused in 2020 due to COVID-19 but is expected to resume.

To understand exposures and health effects faced by WUI firefighters, NIOSH is working with researchers from the University of Arizona and University of Miami to expand an existing collaborative research study (the Fire Fighter Cancer Cohort Study) to collect data regarding exposures from WUI fire incidents during the 2019 and 2020 fire seasons. Characterizing the types of chemicals, as well as the routes and levels of exposures, will help us understand health risks for wildland firefighters.

NIOSH is also in the process of developing a study assessing self-reported exposures to wildfire smoke and COVID-19 health outcomes among wildland firefighters. Additional information about this research will be available soon on the NIOSH Fighting Wildfires Page.


Authors of this article:

LCDR Corey Butler,MS REHS, is a Lieutenant Commander with the United States Public Health Service and an Occupational Safety and Health Specialist in the NIOSH Western States Division.

CAPT Christa Hale,DVM, MPH, DACVPM (Epi), is a Captain with the United States Public Health Service and Senior Epidemiologist and Veterinarian in the NIOSH Western States Division.

Kathleen Navarro, PhD, MPH is an Associate Service Fellow with the Division of Field Studies and Engineering.

Elizabeth Dalsey, M.A., is a Health Communication Specialist in the Western States Division.

CAPT Chucri (Chuck) A. Kardous, MS, PE, is a Captain with the United States Public Health Service and a research engineer with the NIOSH Division of Field Studies and Engineering.

Pamela S. Graydon, MS, COHC, is an Electronics Engineer working in hearing loss prevention in the NIOSH Division of Field Studies and Engineering. 

CAPT David C. Byrne, Ph.D., CCC-A, is a Captain with the United States Public Health Service and a research audiologist with the NIOSH Division of Field Studies and Engineering.


[i] Adetona O, Reinhard T, Domitrovich J, Boryles G, Adetona A, Kleinman M, Ottma R, Naher L [2016]. Review of the health effects of wildland fire smoke on wildland firefighters and the public. lnhal Toxicol 28(3): 95-139. Available from:

[ii] Navarro K, Kleinman M, Mackay C, Reinhardt T, Balmes J, Broyles G, Ottmar R, Naher L, Domitrovich J [2019]. Wildland firefighter smoke exposure and risk of lung cancer and cardiovascular disease mortality. Environ Res 173:462-468. Available from:

[iii] Reid CE, Maestas MM. Wildfire smoke exposure under climate change: impact on respiratory health of affected communities. Curr Opin Pulm Med 2019;25:179–187.

[iv] Moore JB, June CH. Cytokine release syndrome in severe COVID-19Science 2020;368:473.

[v] West MR, Costello S, Sol JA, Domitrovich JW [2020]. Risk for heat-related illness among wildland firefighters: job tasks and core body temperature change. Occup Environ Med77(7):433-438. Available from:

[vi] NIOSH [2012]. Report of a NIOSH health hazard evaluation, HHE 2011–0035. By Eisenberg J and McFadden J. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. Unpublished.

[vii] Broyles G, Butler C, Kardous C [2017]. Noise exposure among federal wildland fire fighters. J Acoust Soc Am 141(2) EL177. Available from:

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Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire.

10 thoughts on “Smoke — and the health of firefighters”

  1. Are there any published data on fire conditions where ground and hand crews were effective and ineffective?

  2. You are absolutely right about the UK. I’m not advocating one way or the other, just pointing out that other places have a much different view of risk management and benefit.

  3. The Europeans are ahead of us on this. Specifically, the Spanish and the Pau Costa Foundation have been questioning the safety for firefighters in the wildland environment related to smoke for years. They often fight fire entirely differently to protect their personnel. In fact, in the UK, they don’t issue fire shelters because they will not tactically put firefighters in situations where they need them. The point is, there is a radically different view of risk and benefit across the pond. We might do well to study up on what they do as we move forward with more policy related to firefighter safety in the wildland operational environment.

    1. Okay, I hear you, but it’s a lot easier to not use tactics that require fire shelters when you have the fire environment of the UK.

      (Australia and Canada and for that matter the USA before 1985ish are more compelling arguments against carrying fire shelters.).

  4. Exposure to smoke and all of the nasty whatevers that come with it is a very real part of the job for frontline firefighters, with no ppe to provide protection.
    Another aspect to wildland firefighting that doesn’t get the attention it deserves is the exposure to long shifts of minimal rest, often for months, not days or weeks. This leads to a precipitous drop in killer T cells and other body defenses..
    I came down with pneumonia 3 times in my career….the worst almost put me under..spitting blood for 2 months doesn’t feel good…
    Each and every time came at the end of long, hard fire seasons . As a seasonal employee, I was left with no employment or sick leave to deal with those illnesses….
    That was back in the 80’s and early 90’s, before work to rest ratios were applied and seasonals were just kicked to the curb as soon as fire season looked to be over..
    Seems like there have been improvements, but I still think the long seasons with poor rest are undestimated in respect to health concerns.

  5. Great comments that have merit, The USFS has been kicking this can for decades, there have been many feeble attempts to study the health hazards of smoke here is one from the 90’s , I worked with a few who completed a exposures report for every fire they were on, I thought it was a waste of time, I wish I would have maybe done a better job documenting all of my exposures, what ever, it is what it is, I am 58 on my way to 59 soon, I know that I have left a few years on the fire line, no doubt about it, It would be pretentious of me to say I did not know the risk because I did, we used to say it can’t hurt you it’s just brush burning no big deal.
    On a stage 4 AQ day folks are asked to stay in doors…..Just saying……We know that it is bad for us, it’s about making a choice, I could go on and on about all the respiratory issues I have had but why, I always got better…..With all of the shortfalls it’s still greatest job on the planet, it just is……
    Leadership needs to be mindful of exposure and minimize as best as they can, we used to stand in smoke just for the sake of standing in smoke, work harder not smarter…..Peace…..

  6. I got into this gig mainly because my Dad’s stories of getting paid to be in the woods while being awesome and seeing amazing stuff were too good to ignore. He’s still alive but has been dealing with multiple cancers for almost two decades.
    When I accepted my first fire job he told me it would suck but to stick it out through college. I did, and 23 years later it’s my destiny.
    On a good day my lungs only hurt if I inhale deeply. On most days it feels like most cells in my body are about to explode. I rarely sleep well unless on assignment.
    I do not use tobacco, and I consume a diet that most would consider very healthy. My BMI is 23.5 and I PT as hard as I did 20 years ago.
    I realize that all my good practices cannot shield me from the onslaught of carcinogens that I inhale/ingest as a regular part of my job. I do not regret my career choice but I do hope that my later years aren’t spent in a revolving door of chemo treatments. I truly hope my son does not choose this profession.

  7. With all the negative health issues involved with wildland firefighting and the extreme low pay it doesn’t take a rocket scientist to figure out way this is a dying profession.

    1. I get your pun, John. It is a scandal that this country’s approach to fire suppression needs critical review and action to alter strategies, tactics, and worker welfare. I have found stiff resistance to any suggestion that current practice could be improved.

  8. Thanks so much for publishing/distributing this, Bill.

    While I agree that such studies need to be performed, I wonder why the precautionary principle is not invoked with respect to current practice. To ignore what IS known while continuously awaiting more research is, in my view, unconscionable.


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