Characterization of woodsmoke generated in the air pollution exposure lab and comparison to diesel exhaust

To address the increasing concern regarding woodsmoke (WS) exposure and better understand its effects on human health, a WS generation system was built in the Air Pollution Exposure Laboratory to facilitate future controlled human exposure studies. Ground lodgepole pine was burned to generate WS, with PM2.5 concentrations of approximately 500 µg/m3 obtained. The WS produced by this system was characterized and directly compared with diesel exhaust (DE) generated and collected at the same facility. For gases, WS showed slight increases in CO and CO2 compared with filtered air (FA), whereas DE had significantly higher levels of NOx, CO, CO2, and total volatile organic compounds than FA. The non-refractory composition of WS aerosols was approximately 98% organics, 0.2% ammonium, 1.3% nitrate, and 0.2% sulfate. Among the organic species, the fraction of oxygenated species was much higher in WS aerosols than in DE aerosols. Moreover, WS aerosols had higher concentrations of Cd compared with DE aerosols. Greater oxidative potential was also observed for WS compared with DE, with dithiothreitol consumption rates of 0.0090 nmol/min/µg. This study established a controlled human exposure platform for WS and described the methods used for analyzing and comparing the concentrations, particulate morphologies, chemical compositions, and oxidative potentials of different lab-generated pollutants. The observed differences between WS and DE in oxidative potential and amounts of gases, organic species, and metals provide a foundation for investigating how specific air pollution components differentially impact human health.