Exposure hazards for wildland firefighters

Wildland fires are common in BC, especially during the dry season. Every year thousands of fires of various sizes are started by natural or human causes. Wildland firefighters work on the front line to control the extent of damage from these fires, exposing themselves to the hazardous emissions and thermal stresses, occasionally with tragic consequences.

Exposure to hazardous fire emissions experienced by wildland firefighters differs both qualitatively and quantitatively from the types of exposure experienced by their urban counterparts. Urban firefighters typically deal with more locally restricted conflagrations that are controlled within a relatively short period of time, whereas wildland firefighters deal with fires that can extend thousands of hectares and last for weeks. The work shift of a wildland firefighter can be long, and is repeated daily for many consecutive days or weeks. Exhaustion, dehydration, poor diet, and lack of sleep are possible consequences of this demanding work schedule.

The exposure to hazards also differs significantly. Wildland firefighters are generally exposed to a complex mixture of organic material pyrolysis and decomposition. Urban firefighters are exposed to an even larger and more complex mixture of toxins from fires that can include combustion by-products of organic and synthetic material, solvents, heavy metals, pesticides, and industrial chemicals. 

Exposure situations differ as well. Urban firefighters often work indoors and in confined spaces, where the concentration of hazardous airborne toxins can be extremely high for prolonged periods of time. Wildland firefighters work outdoors, where exposure levels can be mitigated by winds and convective currents, and workers may have the freedom to position themselves in less polluted areas or work upwind. While urban firefighters typically rely on respirators for protection, wildland firefighters, for a number of pragmatic reasons, cannot use respiratory protection regularly. Some rely on bandanas, which may be psychologically reassuring and act as a minor heat barrier, but in reality a bandana offers no protection against hazardous airborne toxins.

Wildland fire emissions may consist of hundreds of toxic by-products, and their formation depends on a number of unpredictable and uncontrollable factors, including fuel type, moisture content, topography, and meteorological conditions. Flaming fires generate a lot of heat, and the combustion efficiency of the fuel produces mostly simpler molecules such as carbon dioxide. Convective forces are large, carrying the smoke high into the atmosphere and farther away. Smoldering fires aren’t as hot, so oxidative combustion isn’t complete, producing many more toxic intermediate by-products of pyrolysis. Convective winds are also weaker, and the smoke tends to stay closer to the ground. This increases the exposure risk for firefighters.

Wildland fire emissions include carbon dioxide, fine particulate matter, carbon monoxide, volatile organic compounds such as formaldehyde and acrolein, nitrogen, and sulfur oxides, as well as lower levels of carcinogens like polycyclic aromatic hydrocarbons. Measuring the exposure of wildland firefighters to these emissions is logistically challenging. Studies have generally found that the average exposures to specific toxins are lower than established occupational exposure limits, but, on occasion, they may be elevated. These sporadic peak exposures can transiently result in moderately elevated carboxyhemoglobin—typically 10% or less. 

Elevated exposure to airborne irritants can produce transient respiratory tract symptoms. Cross-shift and cross-seasonal lung function studies of wildland firefighters have observed small reductions in average lung function parameters. These appear to reverse at the end of the season, but the long-term effects are uncertain, due to the lack of data.

What you can do for patients who are wildland firefighters
Get to know your patient’s work activities. Evaluate and discuss the risks with your patient. It is useful to get a baseline spirometry that can be used for future reference if the need arises. Most patients have had a chest X-ray at some point, and that may be useful as a baseline reference.

Most firefighters, by requirement, are healthy, fit individuals. But some may have or develop cardiac disease or chronic obstructive pulmonary disease. In these cases, you will need to determine the patient’s fitness to work. Individuals with ischemic heart disease may be at high risk when engaging in this type of work, especially if they are front-line firefighters working in fire suppression. This work is extremely physically demanding. Workers with mild and well-controlled respiratory disease may be able to work with few or no restrictions. Those with more advanced COPD with fixed airway obstruction or brittle asthma may be limited in their ability to do this type of work. Such cases may warrant a referral to a cardiologist, respirologist, or occupational medicine specialist.

For more information
If your patient is a seasonal wildland firefighter and you would like further information or assistance with his or her diagnosis or treatment, please call a medical advisor in your nearest WorkSafeBC office.
—Sami Youakim MD, MSc, FRCP
Medical Advisor, WorkSafeBC Occupational Disease Services

Season’s Greetings
Have a safe holiday season and a healthy, happy 2014.
—Peter Rothfels, MD
Chief Medical Officer and Director, WorkSafeBC Clinical Services

Additional reading
Betchley C, Koenig JQ, van Belle G, et al. Pulmonary function and respiratory symptoms in forest firefighters. Am J Ind Med 1997;31:503-509.

Materna VL, Jones JR, Sutton PM, et al. Occupational exposures in California wildland fire fighting. Am Ind Hyg Assoc J 1992;53:69-76.

Naeher LP, Brauer M, Lipsett M, et al. Woodsmoke health effects: A review. InhalToxicol 2007;19:67-106.

Reinhardt TE, Ettmar RD. Smoke exposure among wildland firefighters: A review and discussion of current literature. Portland, OR: U.S. Department of Agriculture Forest Service Pacific Northwest Research Station; 1997. 61 p.

Reinhardt TE, Ottmar RD. Baseline measurements of smoke exposure among wildland firefighters. J Occup Environ Hyg 2004;1:590-606.

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This article is the opinion of WorkSafeBC and has not been peer reviewed by the BCMJ Editorial Board.