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Inmaculada Aguilera,^1,2,3,4 Mònica Guxens,^1,2,3 Raquel Garcia-Esteban,^1,2,3 Teresa Corbella,⁵ Mark J. Nieuwenhuijsen,^1,2,3 Carles M. Foradada,⁶ and Jordi Sunyer^1,2,3,4

¹Centre for Research in Environmental Epidemiology, Barcelona, Spain; ²Municipal Institute of Medical Research (IMIM-Hospital del Mar), Barcelona, Spain; ³Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública, Barcelona, Spain; ⁴Pompeu Fabra University, Barcelona, Spain; ⁵Servei de Salut, Ajuntament de Sabadell, Sabadell, Spain; ⁶Servei de Ginecologia i Obstetrícia, Hospital de Sabadell, Sabadell, Spain

Abstract
Background: There is growing evidence that traffic-related air pollution reduces birth weight. Improving exposure assessment is a key issue to advance in this research area.

Objective: We investigated the effect of prenatal exposure to traffic-related air pollution via geographic information system (GIS) models on birth weight in 570 newborns from the INMA (Environment and Childhood) Sabadell cohort.

Methods: We estimated pregnancy and trimester-specific exposures to nitrogen dioxide and aromatic hydrocarbons [benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene (BTEX) ] by using temporally adjusted land-use regression (LUR) models. We built models for NO₂ and BTEX using four and three 1-week measurement campaigns, respectively, at 57 locations. We assessed the relationship between prenatal air pollution exposure and birth weight with linear regression models. We performed sensitivity analyses considering time spent at home and time spent in nonresidential outdoor environments during pregnancy.

Results: In the overall cohort, neither NO₂ nor BTEX exposure was significantly associated with birth weight in any of the exposure periods. When considering only women who spent < 2 hr/day in nonresidential outdoor environments, the estimated reductions in birth weight associated with an interquartile range increase in BTEX exposure levels were 77 g [95% confidence interval (CI) , 7–146 g] and 102 g (95% CI, 28–176 g) for exposures during the whole pregnancy and the second trimester, respectively. The effects of NO₂ exposure were less clear in this subset.

Conclusions: The association of BTEX with reduced birth weight underscores the negative role of vehicle exhaust pollutants in reproductive health. Time–activity patterns during pregnancy complement GIS-based models in exposure assessment.

Key words: air pollution, aromatic hydrocarbons, birth weight, cohort study, exposure assessment, geographic information system, INMA study, nitrogen dioxide, pregnancy. Environ Health Perspect 117:1322–1327 (2009) . doi:10.1289/ehp.0800256 available via http://dx.doi.org/ [Online 13 April 2009]

Address correspondence to I. Aguilera, Centre for Research in Environmental Epidemiology, Barcelona Biomedical Research Park, Doctor Aiguader 88, 08003 Barcelona, Spain. Telephone: 34-93-2147300. Fax: 34-93-2147301. E-mail: iaguilera@creal.cat

We thank K. Meliefste (Institute for Risk Assessment Sciences, Utrecht University, the Netherlands) and R. Fernández-Patier, A. Aguirre, T. Bomboi, and D. Herce (National Centre for Environmental Health, Madrid, Spain) for the laboratory analysis of passive samplers.

The INMA (Environment and Childhood) study has the financial support of the “Carlos III Health Institute, Spanish Ministry of Health” (G03/176) , Red de Centros de Investigación en Epidemiología y Salud Pública (C03/09) , and Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública.

The authors declare they have no competing financial interests.

Received 6 October 2008 ; accepted 13 April 2009.