Using In Vitro Cultured Lung Cell Exposure Systems to Compare the Toxicity of Fresh and Aged Diesel Exhaust Utilizing an Outdoor Smog Chamber

Previous observations indicated that as urban-like atmospheres were oxidized, the modifications to their chemical composition also affected their toxicological potential. Based on these studies, I hypothesized that atmospheric oxidative processes will alter the composition of urban-like atmospheres containing diesel exhaust, resulting in a modification of biological responses from exposure. The Electrostatic Aerosol in Vitro Exposure System (EAVES) efficiently deposits particles with no significant biological response from any internal processes and only produces a biological response when toxic PM pass through the sampler with the deposition voltage field on. Direct comparison of direct exposure EAVES with the commonly used traditional particle exposure method using a resuspension technique clearly demonstrated that the biological response in the latter was changed by extensive sample handling during the resuspension method, Furthermore, the EAVES is produces a biological effect from a much smaller sample. This new methodology was coupled with a gas phase only exposure system to the outdoor smog chamber to further test the overall hypothesis. Two test atmospheres were generated using diesel exhaust from two vehicles mixed into urban-like gaseous conditions and these systems were subsequently modified by either thermal (dark) or photochemical oxidation. Changes were evident in biological effect and chemical composition, but varied by source and oxidative environment. The gas phase exposures biological responses were increased only from the Mercedes thermally aged condition and in the fresh conditions for the Volkswagen. To understand the biological response from the PM exposures I examined three methods of comparison to the biological response. This indicated that aged atmospheres are significant in biological response and that the primary and secondary carbonyls present during the exposure are important. From these studies, I have demonstrated my hypothesis that atmospheric processes do alter the chemical composition and biological effect of diesel exhaust oxidized in an urban-like environment, with the qualifier that the degree of the effect is dependent on the amount of toxic components deposited on the cells. Further, I can conclude that the source and aging environment of the test atmosphere play important roles in complex mixture toxicity.Doctor of Philosoph