Personal exposure to carbon monoxide and particulate matter pollution in the urban transport microenvironment in Auckland and Christchurch

Abstract

A field campaign was carried out over autumn in 2009 in both Christchurch and Auckland, aiming to assess personal exposure to carbon monoxide and particulate matter pollution in the transport microenvironment during peak traffic time in the morning and afternoon. The representativeness of fixed station monitoring (FSM) with the personal monitoring in the transport microenvironment was examined in both cities. This thesis characterized the determinants of personal exposure to air pollution in the transport microenvironment, in relation to traffic emissions and prevailing meteorology. Car commuters consistently experienced the highest mean exposure to carbon monoxide in both cities, whereas personal exposure to particulate matter pollution was usually highest during journeys by bus in both sites. Cycling mode resulted in relatively lower mean exposures to both CO and particulate pollution as compared to motor vehicles. Notably, train became the ideal mode of transport in Auckland due to the least mean exposure to CO for train commuters. Mean exposure to carbon monoxide was reasonably correlated with mean exposures to PM1.0 or ultrafine particle counts during journeys by bike in both cities. The average exposures to PM10 showed a strong correlation with PM2.5 exposures during all the journeys in both cities, but displayed weaker or little correlation with the exposures to PM1.0 or ultrafine particle counts. The average background CO exposure during bike journeys showed similar levels to ‘Queen St’ station monitoring located at street kerbside in Auckland, but was generally higher than most urban background FSMs (e.g. ‘Takapuna’ station) in Auckland. In comparison, the average background exposures to PM10 or PM2.5 in the transport microenvironment were similar to most urban background FSMs (e.g. ‘Takapuna’ station) in Auckland. Notably, ‘Takapuna’ station monitoring was well correlated with the personal monitoring to both CO and PM10 pollution on bike mode in Auckland, and thus was used to predict both background and mean exposures to CO and PM10 during bike journeys in Auckland. The dominant causal factors associated with the peaks in exposure concentrations during commutes have been identified. These included neighboring diesel vehicle, traffic congestion, and traveling in street canyon and intersections. Each 1 m s-1 increase in wind speed resulted in decreases of mean CO exposure by 0.67 ppm for bike mode and 0.56 ppm for bus mode in Auckland. Temperature was also inversely correlated with CO exposure concentrations in Auckland. Relative humidity tended to ii increase the exposure concentrations of PM10 and PM2.5 in both cities. These findings improved our understanding of links between personal exposure to air pollution and health risks in the transport microenvironment, providing guidance for transport policy making and urban design.