Carbon Monoxide Exposure in Wildland Firefighting: A Comparison of Monitoring Methods

Abstract

The goals of this study were to field test and compare three methods for assessing carbon monoxide (CO) exposures to wildland firefighters, and to acquire additional exposure data to indicate activities and conditions under which this population may be exposed to hazardous CO levels. The three monitoring methods were: 1) passive colorimetric diffusion tubes; 2) electronic datalogging monitors; and 3) end-exhaled air (breath) monitoring. Full-shift time-weighted average CO exposures, determined using passive diffusion monitors, were low for all employees monitored, with a mean of 8.2 ppm (n = 51). These monitors were found to be an easy means for collecting a large number of full-shift CO measurements. The job tasks on these shifts included line construction, backfiring, line holding, and mop-up. Efforts to collect detailed individual activity information by having firefighters make entries in logbooks were largely unsuccessful. Real-time CO exposures for 12 individuals were monitored using electronic dataloggers. Two firefighters (17%) had 1-minute exposures of, respectively, 339 and 212 ppm, which exceeded the Occupational Safety and Health Administration ceiling limit of 200 ppm. One firefighter had a 45-minute CO exposure at approximately 150 ppm while performing a mop-up activity. Full-shift TWAs measured with the dataloggers agreed fairly well with those determined using the passive dosimeters. One firefighter had a postshift level of CO in end-exhaled air that exceeded a recently proposed Biological Exposure Index of 20 ppm. There was a small but statistically significant increase in CO in end-exhaled air across the shift (mean change was 2.2 ppm). Change in CO concentration in end-exhaled air across the shift did not correlate well with average airborne exposure. Further CO exposure monitoring of wildland firefighters is needed to associate the higher CO levels with specific activities and conditions. The electronic data-logging monitors are ideal for that purpose, but better methods for recording individual activities should be developed.