title: Assessing the spatial distribution of nitrogen dioxide in London, Ontario.
abstract: Land use regression (LUR) models have been widely used to characterize the spatial distribution of urban air pollution and estimate exposure in epidemiologic studies. However, spatial patterns of air pollution vary greatly between cities due to local source type and distribution. London, Ontario, Canada, is a medium-sized city with relatively few and isolated industrial point sources, which allowed the study to focus on the contribution of different transportation sectors to urban air pollution. This study used LUR models to estimate the spatial distribution of nitrogen dioxide (NO2) and to identify local sources influencing NO2 concentrations in London, ON. Passive air sampling was conducted at 50 locations throughout London over a 2-week period in May-June 2010. NO2 concentrations at the monitored locations ranged from 2.8 to 8.9 ppb, with a median of 5.2 ppb. Industrial land use, dwelling density, distance to highway, traffic density, and length of railways were significant predictors of NO2 concentrations in the final LUR model, which explained 78% of NO2 variability in London. Traffic and dwelling density explained most of the variation in NO2 concentrations, which is consistent with LUR models developed in other Canadian cities. We also observed the importance of local characteristics. Specifically, 17% of the variation was explained by distance to highways, which included the impacts of heavily traveled corridors transecting the southern periphery of the city. Two large railway yards and railway lines throughout central areas of the city explained 9% of NO2 variability. These results confirm the importance of traditional LUR variables and highlight the importance of including a broader array of local sources in LUR modeling. Finally, future analyses will use the model developed in this study to investigate the association between ambient air pollution and cardiovascular disease outcomes, including plaque burden, cholesterol, and hypertension.
authors.affiliation: Department of Geography, Western University, London, Ontario, Canada. thoiamo@uwo.ca
authors.forename: Tor H
authors.initials: TH
authors.lastname: Oiamo
authors.forename: Isaac N
authors.initials: IN
authors.lastname: Luginaah
authors.forename: Michael
authors.initials: M
authors.lastname: Buzzelli
authors.forename: Kathy
authors.initials: K
authors.lastname: Tang
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Xu
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Brook
authors.forename: Markey
authors.initials: M
authors.lastname: Johnson
mesh_terms: D000393:Air Pollutants / Q000737:chemistry*; D004784:Environmental Monitoring; D009585:Nitrogen Dioxide / Q000737:chemistry*; D009864:Ontario
chemical_list: D000393:Air Pollutants; D009585:Nitrogen Dioxide