Characteristics of Polychlorinated Dibenzo-p- Dioxins and Dibenzofurans and Exposure Risk of Labors in Indoor Air of Steel Sintering Plant

• Main Authors: Sheng-Lung Huang, 黃生龍
• Other Authors: Perng-Jy Tsai
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/88560137529636101603

碩士 === 國立成功大學 === 環境工程學系碩博士班 === 92 === 　　Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) generally denotes as dioxin. In this study, a time-activity model was used to examine the dioxin exposure of workers in a molten process plant. According the model, workers were divided into four similar exposure groups (SEGs), including labors work at the raw materials inlet and control room (group A), at sintering grate and control room (group B), at rough roll shredder and control room (group C), and only at control room (group D). The partition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) between gas-phase and particle-bound and particle size distributions of PCDD/Fs in the atmosphere of different workplace of a sinter plant were investigated. Those results were as follows: 1. The average TSP concentrations of raw materials inlet (site A), sintering grate (site B), and rough roll shredder (site C) are 3780, 1210, and 1240 μg/m3, respectively. Site A has the highest TSP concentration among those selected sampling sites, and it may be due to the emissions of particles in raw material inlet. 2. The PCDD/Fs I-TEQs of sites B and C were all higher than that of site A for three sampling events. Studied results showed that site A has the highest TSP concentration. Meanwhile, the particle-bound PCDD/Fs concentration of sites B and C were higher than that of other sampling sites. It was estimated that PCDD/Fs formation at sites B and C was though the mechanism of de Novo after raw material sintered. 3. The PCDD/Fs concentration of gas phase of sites B and C were higher than that of other sampling sites, which may be due to the emission of fugitive gas from the sintering process. 4. Partition of PCDD/Fs in the particle-phase was higher than that in gas-phase, which was due to the high TSP concentration in the atmosphere of the sinter plant and most of the PCDD/Fs bounded in particle surface. Hence, to decrease the PCDD/Fs concentration of a sinter plant, controlling particles emission is the first priority. 5. Site C has higher aggregates PCDD/Fs I-TEQs (gas phase plus particle phase) than that of site B for both the first and second samplings events. However, site B has higher aggregates PCDD/Fs I-TEQs for the third sampling event. Nevertheless, site D has the lowest aggregates PCDD/Fs I-TEQs for those three samplings events. 6. Owing to small particle has lower momentum than large particle; small particle was easier to be pulled down than large particle through the sintering bed by strong airflow (site B). However, rough roll shredder (site C) could cause large particle formation in its process. The particle size distribution of site C for the second and third sampling events was similar to each other. 7. Emission particles from sintering grate (site B) are mostly the coarse particle. After fugitive gas cool down and adsorbed on the surface of particle, the particle size distribution of aggregate PCDD/Fs should contain mostly in coarse particle. The studied results indicated that particle size distribution of aggregate PCDD/Fs of the site C was similar to that of site B. 8. The MMDo of aggregate PCDD/Fs are all lower than that of the TSP for all sampling events. It indicates that small particle containing more PCDD/Fs than the large particle. Meanwhile, the majority of the gas PCDD/Fs is adsorbed to the small particle owing to larger surface on it. 9. According to the σgf and σgc of the TSP, it indicates that the distribution range of small particles is larger than the coarse particles. The distribution of seventeen 2,3,7,8 chlorinated substituted PCDD/Fs congeners were more concentrated in coarse particle range than in small particle range. According the σgo of TSP, PCDD/Fs, and seventeen 2,3,7,8 chlorinated substituted PCDD/Fs congeners, the range of particle distribution is quite large. 10. Small particle has higher PCDD/Fs content than that of larger particle. It could be due to the small particle has larger surface and adsorb more PCDD/Fs on it. However, there is a peak at the coarse particle range. That could be due to the PCDD/Fs formation through the de Novo mechanism. 11. After W-test, all similar exposure groups are belongs to the logarithm-normal distribution. The values of AMMVUE were between 0.023∼0.066 pg I-TEQ/Nm3. Group A has the lowest AMMVUE, and then is the Group B, Group D, and Group C. 12. Assuming that labors don’t wear dust-proof masks, the risk assessment is as follows: Group C labors have the highest cancer risk (3.30E-05) and Group A labors have the lowest cancer risk (1.15E-05). Low-chlorinated PCDDs and PCDFs contribute to the major part of PCDD/Fs concentration in gas phase and are the major dedicator of cancer risk. To the contrary, high-chlorinated PCDDs and PCDFs contribute to the major part of PCDD/Fs concentration in particle phase and are the major dedicator of cancer risk