Understanding the Health Hazards of Smoke for Wildland Firefighters

Smoke has always been a problem for wildland firefighters. Research conducted in the 1960's and 70's on the health effects of smoke exposure was not conclusive. The 1987 fires in northern California and the 1988 Yellowstone fires raised serious concerns about the effects of forest fire smoke on the health of wildland firefighters. Atmospheric inversions concentrated the smoke and forced numbers of firefighters to seek medical attention for upper respiratory problems.

In 1989, the National Wildfire Coordinating Group began developing a comprehensive study plan for determining the immediate and long-term effects of exposure to forest fire smoke. The National Wildfire Coordinating Group asked the Missoula Technology and Development Center (MTDC) to coordinate the national effort. Following years of study and analysis, MTDC held a conference in 1997 to review progress in each area of the study plan, and to develop risk management recommendations. This brochure outlines project findings and recommendations for reducing exposure to the health hazards of smoke.

Dr. Darold Ward and coworkers at the Fire Sciences Laboratory in Missoula conducted a series of laboratory and field studies to determine the components of vegetative smoke.

"Through the detailed chemical characterization of smoke, we find literally hundreds of compounds. . . many of these are in very, very low concentrations." -- Darold Ward

Roger Ottmar of the Forest Service's Pacific Northwest Research Station and Tim Reinhardt, Radian Corporation, conducted studies of employee exposure at prescribed and wildland fires. The research team fitted firefighters with sampling packs to collect breathing-air samples. The samples were analyzed in the laboratory for respirable particulate, carbon monoxide, formaldehyde, acrolein and benzene, and other toxic compounds. The researchers found that exposure to particulate matter, carbon monoxide and aldehydes was considerably less than they would have expected. Fewer than 5% of the firefighters studied were exposed to concentrations that exceeded exposure levels deemed permissible by the Occupational Safety and Health Administration (OSHA).

Average exposures and exposure limits for hazards in smoke.
Hazard WL fire Rx fire OSHA/PEL 
CO (ppm) 4.1 4.1 50.0* 
RPM (mg/m3) 0.69 0.63 5.0 
Form (ppm) 0.023 0.047 0.75 
Acrol (ppm) 0.003 0.009 0.1 
Benz (ppm) 0.016 0.016 1.0 

*All limits are time-weighted averages (TWA) unless noted.

Where: WL fire = wildland fire and Rx fire = prescribed fire; CO = carbon monoxide; RPM = respirable particulate matter; Form = formaldehyde; Acrol = acrolein; and Benz = benzene. PEL = Permissible exposure limits.

"The firefighters have a health risk at both wildfires and prescribed fires. It is a risk that probably is less than some of the other risks that they have out on the fireline, such as falling snags and rolling rocks and getting hurt with their tools that they're using, and also just driving on very narrow roads and hiking in very steep and rugged terrain." -- Roger Ottmar

Dr. Brian Sharkey of MTDC was one of many looking into the health effects of exposure to smoke. Short-term exposures cause eye irritation, coughs, and sore throats. Lung function tests show a small but significant decline in lung function that reverses when the person is no longer exposed. So the short-term effects tend to be transitory and reversible.

"Given the time to recover, the human lung has a remarkable ability to cleanse itself." -- Brian Sharkey

Tiny hairlike projections called cilia sweep particles out of respiratory passages. Days or weeks of exposure may suppress ciliary action and immune function, and set the stage for particle buildup and bronchitis. Those with asthma and allergies may experience more problems with exposure. Researchers recommended a study to determine the long-term effects of exposure to smoke.

Dr. Tom Booze, a toxicologist with Radian International, conducted a risk assessment to estimate the long-term health effects of exposure. He looked at two exposure assumptions, an average exposure and a worst case scenario that assumed very high exposure levels for 9.4 hours a day, 97 days a year for 25 years-a condition that exceeds any known exposure. Under this worst case scenario, the risk assessment showed some increase in cancer risk, and the noncancer health risks indicated the likelihood of respiratory irritation.

"What we found was for the average exposure assumptions, in other words most of the people, there doesn't seem to be a problem." -- Tom Booze

Risk Management
In April 1997 MTDC convened a conference to review research findings and reach agreement on a list of recommendations for risk management, including training and tactics. monitoring , health maintenance, respiratory protection, medical surveillance, and research.

Training and Tactics: Wildfire
Include information on the health hazards of smoke in firefighter and fire manager courses.
Include smoke hazards at planning and briefing sessions and in fire behavior forcasts.
Use flank rather than head attack where appropriate.
Minimize mop-up when possible; avoid periods of inversion.
Use time and patience instead of water to put fires out; rely on burn-up instead of mop-up.
In heavy smoke, give up acres to gain control.
Locate camps and command posts in areas that are not prone to inversions.
Reduce dust by watering roads.
Use minimum impact suppression techniques (MIST).
Tactics: Prescribed Fire
Address smoke impacts in the Job Hazard Analysis.
Use equipment rather than people, when possible, in holding areas.
Design burn plans with 'maximum allowable perimeter.'
Minimize mop-up whenever possible.
Change ignition times and firing patterns to minimize smoke impact on persons lighting the fires.
Adjust prescriptions, where possible, to reduce smoke by providing more complete combustion.
Rotate personnel out of heavy smoke areas.
Researchers studied the relationships among the pollutants in smoke.

"If carbon monoxide is highly correlated to these other things, which all our data shows that it is, why not just measure carbon monoxide?" -- Tim Reinhardt

Use one carbon monoxide (CO) dosimeter per crew to monitor exposure to smoke.
Health Maintenance
Ensure that firefighters are properly trained and equipped for the conditions; provide for good rest and sleeping conditions.
Provide adequate nutrition and encourage fluid intake; provide supplements if needed.
Allow adequate time for recovery.
Follow recognized health maintenance procedures to avoid the spread of infection; limit close contact, wash hands before meals.
Don't share canteens except in emergencies.
Emphasize the importance of good health, nutrition, and fitness in all training.
Respiratory Protection
Respirator studies were conducted in the laboratory and in the field.

"I would conclude that while respirators are feasible, they are imperfect. They don't take care of carbon monoxide, they reduce work capacity, and they may not be necessary since our exposure levels are below 5% {of OSHA's Permissible Exposure Limits} and could be getting lower if we follow the recommendations of our Health Hazards of Smoke Conference." -- Brian Sharkey

Respiratory protection should be considered only if other controls, such as training, tactics, and monitoring, fail to protect worker health and safety.
If needed, develop, test, and seek National Institutes of Occupational Safety and Health (NIOSH) approval for a respirator designed specifically for the wildland firefighter.
Medical Surveillance and Research
A program of medical surveillance is needed to track firefighters' health. In addition, health-related research should be considered to determine the long-term effects of exposure to smoke.

Recommendations From Project Participants
"Probably the most important thing that can be done by managers is to plan ahead, to organize their fire-their managed fires especially-in a way that keeps firefighters out of high smoke concentration areas." -- Darold Ward

"I think the most important recommendation to reduce the risk of firefighters to smoke exposure is awareness training. . . There are ways in which they can reduce that exposure level and thus reduce their risk." -- Roger Ottmar

"I'd recommend that you . . . monitor your exposure in some way, . . listen to the alarm of your senses that are telling you this smoke is uncomfortable and avoid it." -- Tim Reinhardt

"A principle of toxicology is reduce your exposure to reduce your risk. So the more steps you take to cut back on smoke exposure, dust exposure, et cetera, the more you're doing to reduce your risk of adverse health effects." -- Tom Booze

"I think we can do some real easily implementable things to reduce the incidence of upper respiratory infection in firefighters. I don't think they'd have to cost an awful lot of money. I think we need to emphasize the importance of good physical fitness … good personal hygiene, and healthy behaviors." -- Mark Vore, USDA FS

"I think basically if an individual firefighter is sensitive to the conditions that they're experiencing, running nose, watering eyes, it looks smokey, then it's probably not a place you want to be-take the common sense step of backing off a few feet, getting into a different location … using the natural conditions that are out there to put yourself in a better environment." -- Dick Mangan, MTDC

"To reduce the risk of exposure I would first of all move forward to implement the recommendations of our conference. If we do that and if we monitor to see how we're doing, I have a feeling that we will have largely removed most of the risk. If not, then we need to take additional steps and those additional steps could include the use of respirators. It could include totally different ways of fighting fire." -- Brian Sharkey

More Information
Additional single copies of this document may be ordered from:

USDA Forest Service
Missoula Technology and Development Center
Building 1, Fort Missoula
Missoula, MT 59804-7294
Phone: 406-329-3900
Fax: 406-329-3719
E-mail: wo_mtdc_pubs@fs.fed.us

For additional technical information, contact Brian Sharkey at the address above.
Phone: (406) 329-3989
Fax: (406) 329-3719
E-mail: bsharkey@fs.fed.us

Copies of Health Hazards of Smoke: Recommendations of the Consensus Conference (NFES 2557, est. $1) and the video Health Hazards of Smoke (NFES 2560, est. $5) may be ordered from the National Interagency Fire Center, ATTN: Great Basin Cache Supply Office, 3833 S. Development Ave., Boise, ID 83705. Orders may be mailed or faxed (208-387-5573). No phone orders.

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