Influence of Differing Microenvironments on Personal Carbon Monoxide Exposure in Auckland, New Zealand

Epidemiological studies typically estimate pollutant exposures using data from outdoor fixed monitoring stations (FMS). However, due to individual mobility through space, time spent in indoor environments and the heterogeneity of the urban atmosphere, data from FMS provides a poor representation of the actual personal exposure to air pollutants. The aim of this study is to investigate the relative importance of time spent in common microenvironments (such as commuter, home, work and recreational) to determine personal exposure to air pollution. The study also investigates the extent to which fixed monitoring stations (FMS) are representative of personal exposures. For this purpose, 17 participants monitored their personal exposure to carbon monoxide (CO) for a full working week and completed a time activity diary identifying the particular microenvironments in which they spent their time. Overall, the participants exposure to CO were lower than those observed in other northern hemisphere cities reported upon in the literature. FMS located in central Auckland were found to provide reasonable estimates of mean daily personal exposure but were poorly correlated with diurnal variations in personal exposure. The results found that, while the highest mean exposures were recorded in the commuter microenvironment, the home microenvironment accounted for 55% of the total CO dose during the week. Increased levels of personal CO exposure were observed in indoor areas where gas heating, gas stoves and tobacco smoke were present. Participants recorded highly variable exposure to CO in recreational microenvironments, in part explained by the wide range of recreational activities.