From the Lung Epithelial Proliferation and Immune Inflammatory Response Aspects to Assess a Suitable Exposure Metric for Quartz Dusts of Different Particle Sizes

S-01A6-4 Background/Aims: The objective of this study was to investigate the relationships between 3 exposure metrics, including mass, surface area, and number concentration for quartz of different particle size and lung epithelia cell proliferation and inflammatory response, and to determine the most suitable exposure metric for quartz exposure. Methods: The quartz dust was separated into 3 particles size by using a liquid sedimentation system, and separated quartz dust was analyzed by Scanning electron microscope and Transmission electron microscopy to determine their true particle size distributions. The MTT cell proliferation assay was used for the proliferation index of pulmonary A549 cells and ELISA measurement was used for TNF-α and TGF-β production of RAW264.7 cell as the index of acute and fibrogenic response. Results: The count median diameter (CMD) of 3 particles size of quartz were 0.98, 2.61, and 8.79 μm, and the GSDs were consistently less than 1.62. The quartz content for tested dust was higher than 97.5%. The results show that the smaller quartz particle caused the stronger cell proliferation and inflammatory response, and quartz with particle size 2.61 μm was found with the highest fibrogenic response than the other 2 particle sizes. This study also investigated the biological-based dose response relationship for quartz with different particle size while testing against different exposure metrics. The results show that the EC50 for 3 different quartz particles size, using the mass concentration as exposure metric, were similar in cell proliferation, acute inflammation, and fibrogenic response test. But the other 2 exposure metrics were not had the same trend. The R2 of the mass concentration for 3 different quartz particles size was also high than the other 2 exposure metrics. Conclusion: The above results clearly suggest that the mass concentration is the most suitable exposure metric for assessing the health-risks associated with the quartz exposures.