A study on the human exposure in various transportation modes in Hong Kong

Abstract

Vehicle exhaust is the major source of air pollution in Hong Kong. The aim of this study is to use field work data to determine the human exposure level to traffic-related air pollutants while commuting in Hong Kong. The in-vehicle air quality was assessed in eight public and two private transport. The public transport included franchised bus, minibus, taxi, Mass Transit Railway (MTR), Light Rail Transit (LRT), Kowloon Canton Railway (KCR), tram and ferry while the private transport were car and light goods vehicle. The in-vehicle concentrations of gaseous (CO, SO2 and NOX), respirable suspended particulates (RSP) and volatile organic compounds (VOCs) inside the vehicle compartment were measured. As CO is a relative stable compound among various primary traffic-related air pollutants, it was used for initial assessment of this study. The effects of traversing various commuting corridors on exposure levels of commuters were investigated. The in-vehicle CO level is greatly influenced by the out-vehicle CO level. There is an indication that external air pollutants penetrated into the in-vehicle compartment through car body cracks and ventilation system. Street canyon and high traffic volume are the causes of higher in-vehicle CO level in commercial area. In-vehicle CO level is the highest while traversing tunnel microenvironments. The choice of transport influenced the exposure level of a commuter significantly. In general, the exposure level in road transport is higher than in non-road transport. The average in-vehicle air pollution levels were similar in air-conditioned and non-air-conditioned vehicles. Height and size of vehicle, types of travelling route, leakage and intake position of ventilation system were the factors influencing human exposure to air pollution while commuting. The commuter exposure to traffic-related air pollutants in Hong Kong is lower than in most other cities.