RESULTS & DISCUSSION Characterization of Emissions Preliminary Work – Toxicity Assessed at a Single Endpoint

• Results indicated that optimization of the exposure system (i.e., reduction of toxicity not attributable to diesel exhaust) was necessary to increase sensitivity for toxicity assessment. • More endpoints were needed to fully characterize the biological response of A549 cells. Optimization of the Exposure System: • Handling and exposure protocols were revised to increase viability of the cells (Figure 6, Figure 7). • The synthetic air control was determined to have a relative humidity of 0.5%. This likely reduced viability due to dehydration. A bubble humidifier with computer-controlled gas delivery system was purchased from TesSol.4 Work is underway to incorporate this instrument into the diesel exposure set-up (Figure 8)