Health Hazards of Smoke Spring 2001
Risk Management
Carbon Monoxide Exposure
In 1998, the National Institute for Occupational Safety and Health (NIOSH) assisted the Colorado Department of Public Health and Environment, the Forest Service, and the Bureau of Land Management in an evaluation of carbon monoxide exposure. Four crews were equipped with carbon monoxide monitors during wildland firefighting activities. The data did not exceed recommended limits for time-weighted average exposure to carbon monoxide. The time-weighted average for 40 exposure periods was 3.48 ppm (ppm ranging from 0.0 to 22 ppm), well below the OSHA permissible exposure limit of 50 ppm. This time-weighted average compares with the 4.1 ppm time-weighted average reported for numerous prescribed fire exposures and wildfire exposures reported by Reinhardt and Ottmar (1997). During 8 of 40 monitoring periods, the carbon monoxide exposure concentrations exceeded the carbon monoxide ceiling limit of 200 ppm. The time-weighted average data indicate that values above 200 ppm were brief because they did not elevate the averages. The highest exposure, 450 ppm, was associated with a time-weighted average of 6 ppm over an 8-hour sampling period. While the health effects of brief, transient exposures are not known and are unlikely to elevate carboxyhemoglobin (COHb) levels significantly, firefighters should try to avoid high concentrations of smoke during mop up and other tasks associated with exposure to carbon monoxide. (McCammon, J. and McKenzie, L. 1998. Health Hazards Evaluation Report. 98-0173-2782. Washington, DC: National Institute of Safety and Health).
Note: Apparently healthy young men can perform upper- and lower-body work at carbon monoxide exposures that result in COHb levels of 20 percent without impairing cardiovascular function (Kizakevich and others, 2000. European Journal of Applied Physiology). It takes a carbon monoxide exposure of 200 ppm for 8 hours before COHb levels reach 20 percent (figure 4). A COHb of 20 percent means that 20 percent of the oxygen-carrying capacity of the blood (hemoglobin) is tied up with carbon monoxide. A COHb of 20 percent is equivalent to working at 18,000 feet.
Figure 4—Exposure duration and carboxyhemoglobin levels in the blood.
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