Combustion Conditions Influence Physiochemical Properties and Cytotoxicity of Flame-Generated Soot to Ocular (ARPE-19) and Lung (A549) Cells
DHRUV MITROO, Durgesh Das, Paul Hamilton, Benjamin Kumfer, Nathan Ravi,
Veterans Research and Education Foundation Abstract Number: 415
Working Group: Health-Related Aerosols
AbstractSoot forms due to incomplete combustion and typically refers to the carbonaceous aerosol produced by a flame. Many sources of soot exist. Depending on the source and combustion condition, the resulting soot bears different physicochemical properties. As a laboratory equivalent of soot, carbon black or commercial ink powders have been used. Both physical and chemical properties of such nanoparticles do not capture those of real soot. Moreover, a range of properties is not readily available. Bench-scale soot generators have been proposed to reproduce a more realistic soot model, with the setup consisting of a way to manipulate the flame properties to controllably reproduce different types of soot.
We developed such a system based using ethylene gas. Our system can switch between premixed and non-premixed modes while online. We have begun characterization of the physicochemical properties of the resulting soot and collected samples for in-vitro toxicity studies. We are targeting the eye and the lung using ARPE-19 (ocular; human retinal pigment epithelial cells) and A549 (pulmonary; adenocarcinomic human alveolar basal epithelial cells) tissue culture cells. Soot particles produced in premixed flames are generally smaller in size, exhibit a lesser fractal structure, and are considerably more toxic to cells than soot particles produced in non-premixed flames. In premixed flames, we find that soot toxicity increases with increasing oxygen concentration in the fuel-rich premixed flame feed, and weakly increases with decreasing flame temperature. We attribute this mostly to increased amorphous carbon compared to graphitic carbon.
Compared to control cells, we find increased presence for proteins indicative of apoptosis, such as Cytochrome C, with exposure to soot. We also find increased presence of other proteins indicative of DNA damage, such as Poly (ADP-ribose) polymerase (PARP), with exposure to soot. This is a step in understanding how properties of soot influence the proteome.