台北都會區居民之戴奧辛暴露風險評估 之研究

Abstract

本研究以臺北市為研究範圍，首先計算臺北市、臺北縣與基隆市戴奧辛排放源之年排放量，接著以ISC-ST3高斯擴散模式模擬戴奧辛空氣中濃度與總沉降量之擴散情形，再分別計算居民之空氣吸入與飲食攝入兩種途徑之戴奧辛致癌暴露風險增量。本研究並探討針對特定污染源設定之減量方案下，居民戴奧辛暴露風險增量之變化情形。 臺北市戴奧辛年排放量於2003年為0.992 g I-TEQ/yr，來源為大型垃圾焚化廠之62.7%、火葬場之17.9% 與機動車輛排放之19.4%。三年之年平均空氣中濃度模擬結果平均值為1.17 fg I-TEQ/Nm3，沉降量模擬結果為6.85 ng I-TEQ/yr-m2，兩者之最大值發生點均位於大安區內。在依照實際飲食比例之情境下計算之臺北市居民之戴奧辛終生致癌風險增量平均值為1.29×10-7，居民之飲食攝入暴露風險約佔總量之64.1%；空氣吸入暴露風險約佔總量之35.9%，以穀物、根莖蔬菜、豬肉為主要貢獻來源；在假設食物均為臺北市當地生產之情境下計算之臺北市居民之戴奧辛終生致癌風險增量平均值為2.07×10-5，居民之飲食攝入暴露風險約佔總量之99.78%；空氣吸入暴露風險約佔總量之0.22%，以穀物、雞肉、魚肉為主要貢獻來源。 以臺北市火葬場為對象之案例研究中，當污染源減量87%時，臺北市居民之空氣吸入戴奧辛暴露風險增量平均值降為未減量時之79.1%，降低較多之區域前三者為大安區、中正區、信義區；最大值降為未減量時之22.5%，其中風險降低較多之區域前三者為大安區、文山區、中正區，顯示火葬場之減量對居民之空氣吸入暴露風險增量之降低有明顯之效果。

This research takes Taipei City as the range of study. First we calculate the annual PCDDF/s emission of sources around Taipei City, then we use ISC-ST3 (Industrial Source Complex-Short Term model 3) gaussian diffusion model to simulate the dispersion of PCDD/Fs air concentration and total depostition. Base on the simulation results, we calculate resident’s annual carcinogenic risk increment due to PCDD/Fs exposure of inhalation and dietary intake. In this study we also confer the change of resident’s PCDD/Fs exposure risk by reducing of specific emission sources. Taipei’s annual PCDD/Fs emission in 2003 is 0.992 g I-TEQ/yr, in which 62.7% is emitted by MSWIs, 17.9% by crementory, and 19.4% by mobile sources. The three year average PCDD/Fs air concentration and total deposition simulation result is 1.17 fg I-TEQ/Nm3 and 6.85 ng I-TEQ/Nm3, while both of the maximum results fall into Daan district. In scenario one, which we take the actual local dietary production into account, the average annual carcinogenic risk increment is 1.29×10-7, in which dietary exposure is 64.1% and inhalation exposure is 35.9%, while grain, below ground vegetables and pork are the three main sources of exposure. In scenario two, we assume the food which residents eat were all produced inside Taipei City, the average annual carcinogenic risk increment is 2.07×10-5, in which dietary exposure is 99.78% and inhalation exposure is 0.22%, while grain, chicken and fish are the three main sources of exposure. In the case study of reducing PCDD/Fs emitted from Taipei Crementory, while the emission decreased by 87%, residents’ average inhalation exposure risk increment decreased by 20.9%, which Daan district, Zhongzheng district and Xinyi district decreased most; residents’ maximum inhalation exposure risk increment decreased by 77.5%, which Daan district, Wenshan district and Zhongzheng district decreased most. This result shows that reducing Taipei Crementory’s PCDD/Fs emission would have great influence on residents’ decrease on PCDD/Fs exposure risk.