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Background and Objectives

Background and Objectives.

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Background and Objectives

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  1. Background and Objectives Previous studies have shown that total surface area of nanoparticles is the best dose metric for particle toxicity. But these studies were conducted with intratracheal instillation, in which the surface area may not be correctly estimated because of particle agglomeration. In this study, we used inhalation exposure to compare relationship of different metrics with lung inflammation induced by zinc oxide particles. We further calculated the benchmark dose to determine the reference dose of zinc oxide. Materials and Methods ZnO NPs were produced in a evaporation and coagulation system and SMPS was used to monitor particle size and number. Healthy SD rats were exposed to 35nm NPs at 9.2x105, 2.1x106, 7.9x106 particles/cm3 and filtered air for 6 hrs. Similarly, rats were exposed to 250nm ZnO at 6.2x104, 1.5x105 , 4.0x105 particles/cm3 and filtered air (Table1). The total number of cells and proportion of neutrophils in bronchoalveolar lavage were determined. The best fit model for lung inflammation with number, mass and surface area concentrations were compared. We also used the Benchmark dose software to calculate the reference dose for ZnO NPs on this effect. Results Pulmonary responses in 35-nm and 250-nm ZnO groups are shown in figure1 and figure2. Tabe2 and figure3 showed dose metric and response metric of ZnO nanoparticles exposure. Results of BMD modeling and calculated mass dose are shown in table3. Conclusion The results indicate that total surface area of particles may play an important role in ultrafine particles related toxicity. In conclusion, ZnO nanoparticles can cause lung inflammation and injury at the concentration below current regulation. Dose metrics of lung inflammation in animals exposed to zinc oxide nanoparticles by inhalation Meng Hoa, Kuen- Yuh Wua, Hung- Min Cheinb, Jung- Yen Liua and Tsun- Jen Chenga aInstitute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, Taipei, Taiwan bEnergy & Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan E-mail: R96841009@ntu.edu.tw Table1 Operation conditions and exposure conditions in each experiment Table2 Correlation between total surface area, mass, number of particles and parameters Table 3 The ZnO current regulation and bench mark dose estimation of this study Surface area-based BMDL was estimated at 9.2x103 mm2/m3 * Calculated mass-based dose Figure1,2 Results for lung inflammation and injury markers in BAL fluid (mean ± STD) after filtered air, 35-nm and 250-nm ZnO NP exposure., respectively (a) proportion of neutrophil, (b) total cells, (c) LDH, (d) total protein Figure 3 Proportion of neutrophils (a,b,c) and total cells (d,e,f) in lung lavage of rats as indicators of inflammation.

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