Differences in Fine Particulates and Estimated Pulmonary Ventilation Rate with Respect to Work Tasks of Wildland Firefighters: A Repeated Measures Study

摘要

Background: Wildland firefighters are exposed to a mixture of chemicals found in woodsmoke and emissions from non-woodsmoke sources such as gasoline or diesel. Improved exposure assessment approaches capable of distinguishing among the sources and estimating internal dose are needed for determining accurate exposure response relationships in epidemiological studies. Objectives: We investigated compositional differences in fine particulate matter associated with various work tasks employed during prescribed burning. We used dual functioning personal aerosol monitors to collect personal PM2.5 (particulate matter with aerodynamic diameter of 2.5 microns and less) and accelerometry data on wildland firefighters. The PM2.5 samples are being analyzed for black carbon and levoglucosan. Methods: Repeated measures on ten wildland firefighters employed by the United States Forest Service-Savannah River, SC and two individuals certified to work on prescribed burns were collected on burn and non-burn days during January-July 2015. Personal monitoring consisted of real-time and gravimetric PM2.5 (MicroPEM, RTI International, Research Triangle Park, NC) and carbon monoxide measurements (Drager Pac III, DragerSafety Inc., Pittsburgh, PA). The MicroPEM's accelerometer data were correlated with participant activity level to estimate average person-day ventilation rates. Estimated ventilation rates were then applied to calculate inhaled total PM2.5 dose. Primary analyses consisted of linear mixed-effects models. Results: Least square means and corresponding 95% upper and lower confidence limits [95% CLs] showed gravimetric PM2.5 did not statistically differ between firefighters who managed fire boundaries (holders) and firefighters who conducted lighting (lighters) (p=0.486; n=16, 290 [162, 520] ug/m3; n=30, 250 [148, 424] ug/m3, respectively). Lighters had significantly higher ventilation rates compared to holders (p<0.0001; n=30, 30.7 [28.7, 32.8] L/min; n=16, 13.8 [12.7, 15.0] L/min, respectively). Additionally, lighters had marginally significantly higher inhaled total dose compared to holders (p=0.0751; n=30, 1310 [561, 3054] ug; n=16, 841 [344, 2054] ug, respectively). Conclusion: Our study is the first to apply accelerometry data to estimate ventilation rates and inhaled particulate matter dose of wildland firefighters. We observed no difference in PM2.5 exposure concentrations by work task; however, after adjusting for ventilation rates, estimated inhaled total PM2.5 dose resulted in significant (marginally) differences. Even with some uncertainty, the ability to account for ventilation rate to estimate inhaled dose instead of the traditionally used air exposure concentration would result in more accurate assessment of the associations between occupational exposures and biological responses observed among wildland firefighters.