Use of an exposure model to explore the impact of residential proximity to a highway on exposures to air pollutants of an ambient origin

Abstract

Air pollutant exposure models are generally applied to large populations living across wide urban areas, and most do not account for daily variation in activity patterns, which can result in exposure misclassification. Far fewer studies exist where exposure is modeled for specific individuals using detailed time-activity data. We employed a novel application of the US-EPA’s Air Pollution Exposure Model (APEX) to simulate exposure levels for 51 residents living within a small study area (1.5 km2) bisected by a heavily trafficked highway in South Auckland, New Zealand. The model produced daily exposure estimates of nitrogen oxides (NO x ), carbon monoxide (CO), and particulate matter (PM10) for the month of July, 2010. Inputs included pollutant and meteorological data monitored at sites positioned both upwind and downwind of the highway, as well as city monitoring sites north of the study area to represent work locations. A local resident survey provided time-activity diary input. The simulation was run once using the residents’ home locations and four times with the population artificially placed 50 and 150 m downwind, as well as 50 and 150 m upwind, relative to the highway. For NO x and CO, the population was 31–36 % more exposed when positioned 50 m downwind and 17–18 % less exposed at the upwind side (p < 0.001), compared to their actual home locations. An additional 100 m separation downwind resulted in a 56–71 % drop in total mean exposure (p < 0.001) and the difference in exposure levels for certain occupations varied by up to a factor of eight (p < 0.05). PM10 exposure was comparatively stable across the area. The effect of residential proximity and position, occupation and work location, were assessed using generalized linear models (GLMs), followed by post hoc testing. This unique application of APEX shows good promise as a planning tool for assessing the potential benefits of a buffer zone between major roads and residential homes, for particular population groups.