Physicochemical Characterization of Personal Exposures to Smoke Aerosol and PAHs of Wildland Firefighters in Prescribed Fires

Particle mass and number of smoke aerosol exposures of firefighters were studied during prescribed fire events. In addition, organic and elemental carbon, functional content and polynuclear aromatic hydrocarbons were determined by spectrometric and chromatographic methods. During the study, firefighters engaged in working tasks including maintenance of the fire front using drip torch ignition and support activities related to fire progression monitoring. Particle number concentration was dominated by particles in the fine range (diameter 0.5-2.5 mu m) including significant quantities (about 10-30%) of coarse particles (diameter > 2.5 mu m). Particle number concentrations varied substantially during a fire event and were related to topography as well as firefighter's activity with elevated particle number concentrations during increased walking speeds. This variation was in agreement with the median and standard deviation of the percent relative concentration difference values indicating within-subject variability. Both organic and elemental carbon were accumulated in particles with a diameter lower than 1.0 mu m. Combustion 4- and 5-ring PAHs including pyrene, chrysene and benzo[a]pyrene were accumulated in fine aerosol, with naphthalene being present mostly in larger particles. The values of PAHs concentration diagnostic ratios indicated a mixture of biomass burning and fossil fuel combustion probably due to the use of gasoline and diesel to ignite the fire. These findings may also be relevant for environmental exposures to wildifres smoke because of the proximity of large and intense wildfires in populated centers.

Automated summary

Firefighters were exposed to particle mass and number during prescribed fire events, with particle number concentrations varying based on topography and activity. Both organic carbon and elemental carbon were found in particles smaller than 1.0 μm, while combustion PAHs were mainly accumulated in fine aerosols. The use of both biomass burning and fossil fuels during ignition was indicated by PAHs concentration diagnostic ratios.