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Wildland Firefighter Health & Safety Report

Issue No. 13

Field Notes
Health Hazards of Smoke

MTDC coordinated an 8-year study of the health hazards of smoke, culminating in a consensus conference and a publication, "Health Hazards of Smoke: Recommendations of the Consensus Conference April 1997." In recent years, interest in the topic has reemerged, driven in part by smoke exposure and by emerging information concerning the health hazards of smoke. This section discusses some of the activities that are underway now.

Followup on some of the 1997 recommendations has been inconsistent. One recommendation of the report was to increase medical surveillance of fire personnel. Pulmonary function tests were included in the medical evaluation for wildland firefighters. The National Institute for Occupational Safety and Health (NIOSH) is working to improve the quality of these tests and to help evaluate the records. NIOSH also conducted carbon monoxide and smoke sampling at a fire camp in California during 2008.

Respiratory Protection

The 1997 recommendations said that respiratory protection should be considered only when other controls, such as training, tactics, and monitoring, fail to protect worker health and safety. In 2006, the National Fire Protection Association was asked to consider developing a respiratory standard for wildland firefighters. That standard is scheduled for release in December 2010. Dave Haston of the San Dimas Technology and Development Center chairs the working group, which includes Roger Ottmar of the Forest Service's Pacific Northwest Research Station and Tim Radtke, an industrial hygienist with the U.S. Department of the Interior. The working group's goal is to establish standards for a respirator that protects firefighters from the health hazards of smoke, including particulate and toxins such as carbon monoxide and aldehydes.

Monitoring and Mitigating Smoke Exposures

For several weeks and months each year, wildland firefighters and support personnel work and rest for weeks and months in locations where they are exposed to varying concentrations of smoke and fine air particulates. The National Wildfire Coordinating Group (NWCG) is working to identify the health effects of such prolonged exposures. Protocols for monitoring exposure as well as for identifying exposure baselines for various components of smoke must be established. Methods to mitigate exposures also should be identified. The NWCG requested that a working group:

  • Survey existing research and conduct an analysis to determine whether new information or technological advances since the Health Hazards of Smoke studies would be a basis for changing current recommendations.

  • Recommend monitoring alternatives for incident base camps. These should range from very simple forms of monitoring, such as visual cues, to monitoring devices or technologies.

  • Explore the need to identify exposure baseline(s) for smoke (and other associated airborne hazards) for firefighting and incident base camp personnel and the exposure levels that would indicate a possible need for monitoring or mitigation.

A working group was formed, including Forest Service and U.S. Department of the Interior employees, including an industrial hygienist with many years experience measuring firefighters' exposure to smoke. The group also examined the neurobehavioral effects of carbon monoxide exposure.

The working group's report, which is being reviewed by the NWCG's Safety and Health Working Team, considers new studies on inhalation hazards for wildland firefighters. It concludes: "The toxicological and epidemiological evidence of adverse effects for those with chronic exposure to smoke is troubling, especially so for those with preexisting cardiovascular health conditions." What the research means for healthy workers is less clear. It seems that the minor decrements in lung function that are seen may be at least partially reversible after periods of no exposure.

The report discusses the impact of ultrafine particles and their effect on respiratory disease and cancer and their relationship to inflammation and coronary artery disease. The risks of silica and asbestos documented in breathing zone air samples were also considered. A key portion of the report focuses on occupational exposure limits at incident base camps and on the fireline.

Occupational Exposure Limits

Exposure limits need to be adjusted to account for the extended shifts and the mixture of contaminants at wildland fires. As an interim measure, the report recommends that the NWCG should adopt a standard reduction factor to adjust OSHA exposure limits on the fireline and at incident base camps.

Adopting an adjusted carbon monoxide (CO) exposure limit has the advantage of keeping CO levels below reported thresholds that may trigger neurobehavioral effects, while also lowering the average exposure to respiratory irritants, aldehydes, and PM3.5 (particulate matter 3.5 microns in diameter or smaller). Table 1 shows the recommended CO and PM3.5 exposure limits.

Table 1—Interim recommended occupational exposure limits for wildland firefighting. PM3.5 stands for particulate matter 3.5 microns in diameter and smaller.
Exposure conditions Interim recommended
adjusted CO exposure
(parts per million)
Equivalent estimated
PM3.5 exposure
Fireline (14 h/d, 7 d/wk) 21 (14-h average) 2.4 mg/m³
Fire camp (24 h/d, 7 d/wk) 13 (24-h average) 1.5 mg/m³

The interim recommended CO value is well below the 50 parts per million exposure limit set by OSHA for an 8-hour work shift. The recommended values are adjusted for extended work shifts (14 hours) and for possible 24-hour exposure at incident base camps. The recommended occupational exposure limits are well above the average exposure for firefighters' work shifts at wildland fires in the West (2.8 parts per million, Reinhardt and Ottmar. 2000. Smoke exposure at western wildfires. Res. Pap. PNW-RP-525. Pacific Northwest Research Station) and at prescribed fires in the Pacific Northwest (4.1 parts per million, Reinhardt, Ottmar, and Hanneman. 2000. Smoke exposure among firefighters at prescribed burns in the Pacific Northwest. Res. Pap. PNWRP-526. Pacific Northwest Research Station).

The PM3.5 values are below OSHA's recommended occupational exposure limit for particulate matter (5 milligrams per cubic meter), but above the average exposure for firefighters' work shifts at wildland fires in the West (0.5 milligram per cubic meter) and at prescribed fires in the Pacific Northwest (0.63 milligram per cubic meter).

The report to the NWCG includes recommendations on monitoring smoke at incident base camps and on the fireline (Reinhardt, Ottmar, and Hallett. 1999. Guide to monitoring smoke exposure of wildland firefighters. Gen. Tech. Rep. PNWGTR-448. Pacific Northwest Research Station).

Neurobehavioral Effects of Carbon Monoxide

An extensive review by the U.S. Environmental Protection Agency (EPA) on the effects of CO in 2000 concluded that behavioral impairments in healthy adults are not significant when the carboxyhemoglobin levels in their blood are below 20 percent. Some studies showed mild impairments when carboxyhemoglobin levels were at 5 percent, a level that could be produced by an 8-hour exposure to a CO concentration of 50 parts per million. Cigarette smokers have carboxyhemoglobin levels of 5 to 10 percent and may have levels as high as 15 percent.

Recommended Research

The report concludes with an extensive list of recommended research, focusing on unanswered questions and on preparing for the release of the National Fire Protection Association respiratory protection standard. It is essential to document the relationship between firefighter exposure to the health hazards of smoke and the incidence and severity of adverse health effects.

Smoke researchers will meet during the fall of 2009 to review current knowledge of smoke effects and to recommend occupational exposure limits for wildland firefighters and incident base camp personnel. Their recommendations will be reviewed by management and field personnel during the spring of 2010.