From measures to models: An evaluation of air pollution exposure assessment for epidemiologic studies of pregnant women

Elizabeth Nethery ^1*, Sara E Leckie ¹, K Teschke ¹ and Michael Brauer ²

¹ The University of British Columbia, Canada
² The University of British Columbia, Vancouver, Canada

^* To whom correspondence should be addressed. E-mail: enethery{at}interchange.ubc.ca.

Accepted 22 November 2007

Abstract

Objectives: To evaluate exposure estimation methods such as spatially resolved land-use regression models and ambient monitoring data in the context of epidemiologic studies of the impact of air pollution on pregnancy outcomes. Methods: We measured personal 48-hour exposures (NO, NO2, PM2.5 mass and absorbance) and mobility (time activity and GPS) for 62 pregnant women during 2005-06 in Vancouver, Canada, 1-3 times during pregnancy. Measurements were compared to modelled (using land-use regression and interpolation of ambient monitors) outdoor concentrations at subjects’ home and work locations. Results: Personal NO and absorbance (ABS) measurements were moderately correlated (NO: r=0.54, ABS: r=0.29) with monitor interpolations and explained primarily within-subject (temporal) variability. Land-use regression estimates including work location improved correlations for NO over those based on home postal code (for NO: r=0.49 changed to NO: r=0.55) and explained more between-subject variance (4% to 20%); limiting to a subset of samples (N=61) when subjects spent >65% time at home also improved correlations (NO: r=0.72). Limitations of the GPS equipment precluded assessment of including complete GPS-based mobility information. Conclusions: We found moderate agreement between short-term personal measurements and estimates of ambient air pollution at home based on interpolation of ambient monitors and land-use regression. These results support the use of land-use regression models in epidemiologic studies, as the ability of such models to characterize high resolution spatial variability is "reflected" in personal exposure measurements, especially when mobility is characterized.

Keywords: Air pollutants/adverse effects/*analysis, Environmental Exposure, Environmental Monitoring/methods, Geography, Pregnancy

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