Assessing pedestrian exposure to fine particulates at fine levels of spatio-temporal resolution

Abstract

A compelling body of international evidence now exists suggesting a causal link between exposure to airborne particulate matter (PM) and adverse health consequences. Travel microenvironments have come under particular scrutiny because PM levels are known to be substantially higher than ambient levels from Fixed Site Monitors (FSMs) on which air quality assessments are based and because people significant proportion of time travelling (e.g., 80 minutes/day in Sydney). Over the last two years, we have developed and tested an approach for assessing the risk of exposure to PM at fine levels of temporal and spatial resolution while travelling by various modes of transport. The approach combines the capabilities of personal Global Positioning System (GPS) technology, portable particle monitors, and voice-recorded information on unusual events, to shed new light on the inherent variability in PM and importantly the location, duration and magnitude of ‘hotspots’. The current paper addresses the critical issue of pedestrian exposure along a busy mixed-use roadway environment in Sydney. We present descriptive and statistical evidence of the key factors impacting overall exposure while walking, the most important of which are general traffic conditions, ambient weather conditions (particularly windspeed), and time-of-day (worse in the morning). We then conduct a ‘hotspot’ analysis in which elevated readings are cross-compared to the information on the tape-recorder. It is clear and striking that particular vehicles (buses, trucks) and events (other pedestrian’s smoking) are highly significant and cannot be ignored if we are to accurately assess and minimise exposure in the future.