Baseline Measurements of Smoke Exposure Among Wildland Firefighters

Abstract

Extensive measurements of smoke exposure among wildland firefighters are summarized, showing that firefighters can be exposed to significant levels of carbon monoxide and respiratory irritants, including formaldehyde, acrolein, and respirable particulate matter. Benzene was also measured and found to be well below permissible exposure limits, with the highest concentrations occurring among firefighters working with engines and torches burning petroleum-based fuel. Exposures to all pollutants were higher among firefighters at prescribed burns than at wildfires, while shift-average smoke exposures were lowest among firefighters who performed initial attack of wildfires in the early stages of the fires. Smoke exposure reaches its highest levels among firefighters maintaining fire within designated firelines and performing direct attack of spot fires that cross firelines. These events and the associated smoke exposures were positively correlated with increasing ambient wind speeds, which hamper fire management and carry the convective plume of the fire into firefighters' breathing zone. The pollutants measured in smoke were reasonably well-correlated with each other, enabling estimation of exposure to multiple pollutants in smoke from measurements of a single pollutant such as carbon monoxide.

Keywords:

• carbon monoxide
• firefighter
• hazard
• health
• smoke
• wildfire

ACKNOWLEDGMENTS

The use of trade or firm names in this publication is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service.

Notes

^A Relative standard deviation.

^B Includes only analytical accuracy.

^C No accuracy assessment method was available.

^A Respiratory irritant that should be evaluated as part of the irritant exposure mixture (E_m).

^B Geometric mean.

^C Among 24 engine-crew firefighters (CO₂ was not measured in 1995).

^D CO₂ was not measured in 1995.

^E Among only seven Type I hand-crew firefighters (total particulate was not measured before 1995).

^F Among 15 hand-crew firefighters (total particulate was not measured before 1995).

^G Not applicable (total particulate was not measured before 1995).

^H Combined exposure (E_m) to the mixture of respiratory irritants acrolein, formaldehyde, and respirable particulate, calculated as the summed ratios of each to their respective OSHA permissible exposure limits.

^I Combined exposure (E_m) to the mixture of respiratory irritants acrolein, formaldehyde, and respirable particulate, calculated as the summed ratios of each to their respective 2003 threshold limit values.

^A Respiratory irritant that should be evaluated as part of the irritant exposure mixture (E_m).

^B Geometric mean.

^A Units are in parts per million for all pollutants except respirable particulate, which is in milligrams per cubic meter.

^B Coefficient of determination.

^C Standard errors of regression coefficients at 95% confidence level.

^A Number of samples comprising geometric mean.