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. 2011 Aug;119(8):1123-9.
doi: 10.1289/ehp.1002976. Epub 2011 Mar 31.

Creating national air pollution models for population exposure assessment in Canada

Perry Hystad  1 , Eleanor Setton, Alejandro Cervantes, Karla Poplawski, Steeve Deschenes, Michael Brauer, Aaron van Donkelaar, Lok Lamsal, Randall Martin, Michael Jerrett, Paul Demers
Affiliations

Creating national air pollution models for population exposure assessment in Canada

Perry Hystad et al. Environ Health Perspect. 2011 Aug.

Abstract

Background: Population exposure assessment methods that capture local-scale pollutant variability are needed for large-scale epidemiological studies and surveillance, policy, and regulatory purposes. Currently, such exposure methods are limited.

Methods: We created 2006 national pollutant models for fine particulate matter [PM with aerodynamic diameter ≤ 2.5 μm (PM2.5)], nitrogen dioxide (NO2), benzene, ethylbenzene, and 1,3-butadiene from routinely collected fixed-site monitoring data in Canada. In multiple regression models, we incorporated satellite estimates and geographic predictor variables to capture background and regional pollutant variation and used deterministic gradients to capture local-scale variation. The national NO2 and benzene models are evaluated with independent measurements from previous land use regression models that were conducted in seven Canadian cities. National models are applied to census block-face points, each of which represents the location of approximately 89 individuals, to produce estimates of population exposure.

Results: The national NO2 model explained 73% of the variability in fixed-site monitor concentrations, PM2.5 46%, benzene 62%, ethylbenzene 67%, and 1,3-butadiene 68%. The NO2 model predicted, on average, 43% of the within-city variability in the independent NO2 data compared with 18% when using inverse distance weighting of fixed-site monitoring data. Benzene models performed poorly in predicting within-city benzene variability. Based on our national models, we estimated Canadian ambient annual average population-weighted exposures (in micrograms per cubic meter) of 8.39 for PM2.5, 23.37 for NO2, 1.04 for benzene, 0.63 for ethylbenzene, and 0.09 for 1,3-butadiene.

Conclusions: The national pollutant models created here improve exposure assessment compared with traditional monitor-based approaches by capturing both regional and local-scale pollution variation. Applying national models to routinely collected population location data can extend land use modeling techniques to population exposure assessment and to informing surveillance, policy, and regulation.

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Conflict of interest statement

The authors declare they have no actual or potential competing financial interests.

Figures

Figure 1
Figure 1
Location of NAPS monitors that were used to create national PM2.5, NO2, benzene, ethylbenzene, and 1,3-butadiene models.
Figure 2
Figure 2
National annual average models for PM2.5, highlighting southern Ontario and the city of Toronto (A), and for NO2, highlighting southwestern British Columbia and the city of Vancouver (B), that incorporate satellite-derived pollutant estimates, geographic land use variables, and deterministic gradients. The seven cities shown in (B) represent locations of independent monitoring data used to evaluate the national NO2 and benzene models.
Figure 3
Figure 3
National benzene LUR model plus gradients (illustrating the city of Toronto) calculated for each street block point in Canada (n = 478,831).
See this image and copyright information in PMC

Comment in

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