Risk assessment for people exposed to particulate PAHs at the bus express lane station in Taipei
Date Issued
2008
Date
2008
Author(s)
Chen, Chien-Jen
Abstract
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.or 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.
Subjects
Diesel bus
carcinogenic risk assessment
principal component analysis
Type
thesis
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