台北市公館地區公車專用道空氣中粒狀多環芳香烴 對人體之健康風險評估

Abstract

本研究乃探討台北市公館地區公車專用道大氣中粒狀多環芳香烴 (PAHs) 對人體之健康風險。參考環檢所空氣中粒狀污染物檢測法—高量採樣法 (NIEA A102.12A) ，使用高流量採樣器 (High-Volume Sampler) 與微孔板均勻沉積衝擊器 (Micro Orifice Uniform Deposit Impactor，MOUDI) 於公車專用道、路邊公車站及遠離道路 180 m 之校園背景站，在假日與平常上班日中於不同季節、不同時段進行大氣周界採樣，樣本使用 GC/MS 定性定量 36 種 PAHs 濃度，並藉由候車民眾之問卷調查，針對美國環保署列出 16 重要性 PAHs 對於台北市民眾進行致癌性風險評估。 研究結果大氣 16 種粒狀 PAHs 濃度公車專用道 > 路邊公車站 > 一般環境，工作日 > 假日，且冬季 > 夏季，指標性物種 BaP 平均濃度在公車專用道為 1.04 ng/m3，路邊公車站為 0.25 ng/m3，一般環境為 0.13 ng/m3 ，公車流量尖峰時易出現高濃度之粒狀PAHs與公車流量有很大之關係，且大部份集中在較高分子量之致癌性 PAHs 物種。在台北市大氣中 PAHs 濃度有季節之差異，公車專用道與路邊公車站大氣中 PAHs-16 濃度 W / S (Winter / Summer) 平均為 1.35 ，但一般環境為 1.01 ，季節之差異只存在有污染源之地區，對於無移動性污染源之地區並無差異。致癌性風險評估結果，公車專用道候車區屬於高度風險地區，長時間暴露在該處會造成風險大幅度增加，本研究並建立 Rt 值風險範圍可明顯判斷地區大氣中 PAHs 濃度所造成之風險程度，Rt值越高表示風險程度越高，公車專用道 Rt 值為 5.36 ，路邊公車站為 2.22 ，一般環境為 0.82 。公車專用道屬於柴油公車停等次數繁多之區域，由主成分分析 (PCA) 與線性迴歸法知公車專用道大氣中粒狀 PAHs 主要來自公車惰轉時所排放，且有 84% 致癌性 PAHs 集中在粒徑小於 1 mm 之微粒與公車惰轉排放也有較高之相關性，結果突顯管制公車惰轉排放致癌性粒狀 PAHs 對於民眾健康之重要性。

In this study, the risk of particulate PAHs to human health at the bus express lane station in Taipei city was assessed and investigated. The standard method - NIEA A102.12A was used to collect samples at the bus express lane, road top bus stop and the campus background station 180 m away from the road. A high-volume sampler and a micro orifice uniform deposit impactor (MOUDI) were used to collect samples during the four periods on each weekday and weekend in different seasons. The samples were analyzed by GC/MS to identify and quantify 36 PAHs. The questionnaire survey was conducted on bus users as well to carry out the carcinogenic risk assessment of 16 priority pollutants declared by USEPA. For the 16 PAHs, their particulate concentrations are the highest at bus express lane but the lowest in the background station. Experimental results indicate that concentrations are higher on weekdays than weekends and higher in winter than summer. The average concentration of the indicator PAH – BaP is 1.04 ng/m3 at express lane, 0.25 ng/m3 at road top bus stop and 0.13 ng/m3 at the background station. High PAHs concentration and proportion of high-molecular-weight PAHs caused by the traffic flow was easily observed on rush hour. According to the ratio of the summed 16 PAHs concentration in winter to that in summer at different sampling points, the seasonal difference was observed at regions with pollution source. Based on the result of carcinogenic risk assessment, bus express lane station is regarded as the high risk area. Rt, risk per unit exposure time, was introduced in this study to determine the risk of PAHs. Rt value was estimated to be 5.36 at bus express lane, 2.22 at road top bus stop and 0.82 at background station. The major source of particulate PAHs at bus express lane was found to be bus exhaust at idle speed by PCA and linear regression analysis. The high contribution of buses at idle speed to particulate PAHs at bus express lane was observed by PCA and linear regression analysis. 84% of carcinogenic PAHs were observed to exist as particles smaller than 1 mm. Based on the experimental results in this study, carcinogenic particulate PAHs from bus exhaust at idle speed make adverse effects on the public health. Therefore, to control bus emissions at idle speed is worth being paid high attention.