Study shows firefighters’ exposure to smoke increases disease risk

Study shows firefighters’ exposure to smoke increases disease risk

06 February 2018

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Depending on the type of work performed and the number of years of exposure, the increased risk can be 22 to 39 percent.

 After collecting data from wildland firefighters in the field, a group of researchers concluded that firefighters’ exposure to smoke can increase the risk of mortality from lung cancer, ischemic heart disease, and cardiovascular disease.

What is in the air that firefighters breathe?

There have been many studies about smoke dating back to the 1988 NIOSH project at the fires in Yellowstone National Park. Most of them confirmed that yes, wildland firefighters ARE exposed to smoke and in most cases they quantified the amount.

In 2004 Timothy E. Reinhardt and Roger D. Ottmar  found a witches’ brew of methyl ethyl bad stuff that firefighters are breathing. All of these are hazardous to your health:

  • Aldehydes (volatile organic compounds); can cause immediate irritation of the eyes, nose, and throat, and inhalation can cause inflammation of the lungs. Short-term effects include cough, shortness of breath, and chest pain. The most abundant aldehyde in smoke is formaldehyde. When formaldehyde enters the body, it is converted to formic acid, which also is toxic.
  • Sulfur dioxide (SO²); causes severe irritation of the eyes, skin, upper respiratory tract, and mucous membranes, and also can cause bronchoconstriction. It forms sulfuric acid in the presence of water vapor and has been shown to damage the airways of humans.
  • Carbon monoxide (CO); As CO is inhaled it displaces O2 as it attaches to red blood cells and forms COHb. COHb reduces the ability of the blood to carry oxygen and causes hypoxia (a condition in which the body does not receive sufficient oxygen). Due to their strenuous work, wildland firefighters often have increased respiratory rates, which will increase the amount of CO being inhaled when smoke is present. COHb has a half-life (the time it takes half of the COHb to dissipate from the body) of about 5 hours. Symptoms of CO exposure include headaches, dizziness, nausea, loss of mental acuity, and fatigue. Prolonged, high exposure can cause confusion and loss of consciousness
  • Particulate matter; Respirable particulates are a major concern as they can be inhaled into the deeper recesses of the lungs, the alveolar region. These particles carry absorbed and condensed toxicants into the lungs
  • Acrolein; may increase the possibility of respiratory infections. It can cause irritation of the nose, throat, and lungs. Long-term effects can include chronic respiratory irritation and permanent loss of lung function if exposure occurs over many years.
  • Benzene; can cause headaches, dizziness, nausea, confusion, and respiratory tract irritation. Although the human body can often recover and repair damage caused by irritants, prolonged exposure from extended work shifts and poorly ventilated fire camps can overwhelm the ability to repair damage to genes and deoxyribonucleic acid (DNA).
  • Crystalline silica; can cause silicosis, a noncancerous lung disease that affects lung function. But OSHA classifies it as a carcinogen.
  • Intermediate chemicals; have been shown to cause a variety of health problems including bronchopulmonary carcinogenesis, fibrogenesis, pulmonary injury, respiratory distress, chronic obstructive pulmonary disease (COPD), and inflammation.

One of the more recent research efforts, from 2009 to 2012, was led by George Broyles of the U.S. Forest Service, National Technology and Development Program, in Boise, Idaho. They collected data in 11 fuel models in 17 states on initial attack, prescribed burns, and large project fires. The group measured carbon monoxide (CO) with electronic datalogging dosimeters and particulate matter using air pumps and filters.

carbon monoxide exposure firefighters
Data from the 2009-2012 wildland firefighter study led by George Broyles. “TWA” stands for Time Weighted Average. CO is carbon monoxide. OEL is Occupational Exposure Limits.

Monitoring carbon monoxide (CO) can be important, and is also fairly easy to do and not terribly expensive. Researchers have found that it can be a surrogate for the primary irritants of concern in wildland smoke near the combustion source. If CO is present, it’s almost certain that the smorgasbord of nasty stuff is in the air.

Electronic CO monitors are available for $100 to $300. Another option is the little disposable CO monitors called diffusion tubes. With the holder they are about the size of a dry erase marker. Many are made by Drager, and for eight hours can record the cumulative CO. You can’t get an instantaneous reading, but the total hourly exposure can be monitored. They cost about $13 each. If one or two people on the crew carry them it can provide a heads up if the air quality is really bad.

What are the health effects of smoke exposure on a wildland fire?

Employers in most if not all workplaces are required to minimize hazards and provide a safe working environment. But of course it is impossible to totally eliminate all risks to firefighters. A cynic might assume that leadership in the wildland fire community may be hesitant to ask the question if they don’t want to hear the answer.

In spite of numerous studies confirming that yes, there is smoke where wildland firefighters work, there has been little in the literature that quantifies the effects on a person’s health. A new study published in August, 2017 contains a preliminary analysis addressing that question.

It is titled Wildland Fire Smoke Health Effects on Wildland Firefighters and the Public – Final Report to the Joint Fire Science Program. The authors are Joe Domitrovich, George Broyles, Roger D. Ottmar, Timothy E. Reinhardt, Luke P. Naeher, Michael T. Kleinman, Kathleen M. Navarro, Christopher E. Mackay, and Olorunfemi Adetona.

They used the field data collected in the 2009 to 2012 George Broyles study to extrapolate the physical and health effects on humans. The authors actually came up with numbers that indicate firefighters’ relative mortality risk for lung cancer, ischemic heart disease, and cardiovascular disease.

They estimate that after a 10-year career with a project fire crew a firefighter would have a 22 to 24 percent increase in mortality from those three diseases, compared to a person with no smoke exposure. After 20 years the risk is 25 to 39 percent. The risks are lower for those working in environments found at prescribed burns and initial attack.

relative risk wildland fire smoke exposurePreliminary analysis of the relative risk of wildland fire smoke exposure.


One of the authors of the study, Kathleen Navarro, told us the data should be considered preliminary. She continues to analyze their findings and may fine tune their conclusions later.

Presumably the International Association of Fire Fighters data below, primarily represents structural firefighters. It appears to show that 63 percent of firefighter line of duty deaths are from cancer.

The 2017 study summarized the recommendations that have been made by researchers over the last 25 years about how to reduce smoke exposure:

  1. Minimize mopup.
  2. Develop a medical surveillance program.
  3. Develop wildland fire-specific Occupational Exposure Limits.
  4. Train firefighters on smoke hazards.
  5. Reduce exposure by limiting shift length.
  6. Rotate crews out of heavy smoke areas.

In 2012 the National Wildfire Coordinating Group issued Guidance for Monitoring and Mitigating Exposure to Carbon Monoxide and Particulates at Incident Base Camps. The group established a new standard for carbon monoxide for wildland firefighters:

Based on the best available science to date, the Smoke Exposure Task Group (SETG) and their group of leading researchers from across the United States established an exposure recommendation for wildland fireline operations to be: Carbon monoxide of 8 ppm for a 24 hour period, and 16 ppm for a 13 hour work shift.

We checked with the U.S. Forest Service, asking about their views on the effects of smoke and the long term plans on the subject.

“The health and safety of wildland firefighters is the top priority of the USDA Forest Service in wildland fire management,” said Shawna Legarza, Director, Fire and Aviation Management, USDA Forest Service. “The agency has been working for several years with leading experts across the country to understand and further study the short and long term impacts of wildland fire smoke on firefighter health. The USDA Forest Service has guidelines in place to reduce the exposure of wildland firefighters to smoke on the fireline. Once this [2017] study is peer reviewed and a final report is published, we will review it carefully and determine measures that are needed to implement the findings.”

What should be next?

Now that we have at least some pretty good data about what firefighters are breathing on wildland fires and information about increased mortality caused by the carcinogens, what is the next step?

Long term firefighter health tracking

In order to fix or improve a situation it has to be defined. It is difficult to say firefighters’ health is a serious problem unless the  short and long-term health of firefighters is tracked. There is no national registry that tracks their exposure or health during and after their careers. Two bills introduced in Congress since 2016 have failed to gather any traction. With the track record of Congress over the last five to 10 years, we should assume there will be no national registry in our lifetimes. This means there needs to be action taken at the state, local, or national agency levels.

And of course the National Wildfire Coordinating Group should, by definition, COORDINATE this effort.

Firefighting leaders need to step up and lead from the front. Let’s see who will be first.

Presumptive illnesses

All fire departments as well as state and federal agencies that employ firefighters or “forestry technicians” must establish a system of presumptive illnesses. If a firefighter is diagnosed with a condition that is on the list, they will be presumed to have contracted the illness on the job, and would be covered like any other on the job injury. The British Columbia government recognizes at least nine “presumptive cancers” among firefighters, including leukemia, testicular cancer, lung cancer, brain cancer, bladder cancer, ureter cancer, colorectal cancer, and non-Hodgkins’s lymphoma.



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