Effects of ambient nitrogen dioxide concentrations on adverse birth outcomes in urban and rural areas of Alberta, Canada.

Abstract

Introduction: The incidence of low birth weight (LBW), preterm birth (PB) and small for gestational age (SGA) in Alberta has been greater than the national average in the last decade, raising a public health concern. Understanding the effects (individual and interactions) of maternal, social and environmental risk factors on adverse birth outcomes (ABOs) is currently a subject of active research. We present the effects of nitrogen dioxide (NO2) emissions in the ambient air on the incidence of LBW, PB, and SGA by considering maternal risk factors and socioeconomic status, for both urban and rural areas in Alberta. Methods: We analyzed all singletons live births with 22-42 weeks of gestational age (n=334,894) in Alberta (2006-2012), and 24 maternal risk factors (e.g. diabetes). We used available postal code data for NO2 levels and socioeconomic status. We classified the mothers’ residential postal code as urban/rural. We applied multivariate logistic regression for estimating the effect (Odds ratios) of NO2 levels on LBW, spontaneous PB (categorized as 22-26 weeks; 27-28 weeks; 29-33 weeks, and 34-36 weeks), and SGA (categorized as <3rd, 3rd to 5th, and 5th to 10th percentiles), in urban and rural areas. Odds ratios were adjusted for significant maternal risk factors and socioeconomic status. Results: We detected significant (OR 95%CIs > 1) effects of ambient air NO2 with LBW in rural (OR=1.10), and urban areas (OR=1.01); PB in urban areas [27-28 weeks (OR = 1.04), 29-33 weeks (OR = 1.02), and 34-36 weeks (OR = 1.01)]; SGA in rural [3rd and 5th percentiles (OR=1.06 and OR=1.07, respectively)], and in urban areas for all percentiles [3rd and 5th (OR=1.01), 10th (OR=1.02)]. Currently, we are assessing the contribution of other industrial emissions on ABOs. Conclusions: Ambient air nitrogen dioxide levels were associated with increased risk of adverse birth outcomes between 1% and 7%, mainly impacting PB (27-28 weeks) in urban areas, and LBW and SGA in rural areas.