Abstract:
Exposure to ultrafine particles is of concern because of the probable adverse effects on health. Pedestrians in urban environments are in close proximity to traffic emissions which are the main source of ultrafine particles. A better understanding of pedestrian exposure is required for health risks to be better understood, pedestrians to be enabled to make informed decisions, and if effective planning and regulation to minimise exposure to ultrafine particles are to be undertaken. Although children are particularly sensitive to adverse health effects no studies of child pedestrian exposure ultrafine particles have been reported. A consistent pedestrian journey through 5 microenvironments in Auckland City was repeated a total of 5 times over summer and 7 times over winter. During each journey ultrafine particle concentrations were recorded at two heights representing adult and child pedestrians and these recordings were synchronised with recordings of location and of sources both on video and on GPS. Pedestrian exposure to ultrafine particles was found to be comparable with other international studies. Exposure in winter was twice that recorded in summer both the means and the maximums. Allowing for this two fold increase, the pattern of ultrafine particle concentration exposure was identical for the two seasons. The main predictor of a pedestrian exposure for each season was the amount of time spent in each microenvironment-- urban park, street canyons, opens road and bus station. Urban park consistently resulted in the lowest exposure Street canyons have high concentrations of ultrafine particulates for relatively low traffic flow. ’Hot Spots’ contribute a disproportionate amount to total pedestrian exposure and were located at intersections and bus stops and some at roadside events. The main sources of ‘Hot Spots’ were identified as vehicles and buses. Children were found to be no more exposed than adult pedestrians over entire journeys but may be more exposed at ‘Hot Spots’. Recommendations to minimise pedestrian exposure and for future research are made.