An Effect of Household Environment and Nitrogen Dioxide Pollution on Congenital Malformations

Abstract

Background: Nitrogen Dioxide (NO2) is a product of fuel combustion originating mainly from industry and transportation. Studies suggest an association between NO2 and congenital malformations (CM). We investigated an independent effect of NO2 on CM by adjusting to individual factors and household environment in Bedouin-Arab pregnant women in southern Israel. This population is characterised by high rates of CMs, frequent consanguineous marriages, paternal smoking, temporary housing and usage of open fire for heat cooking. Methods: We enrolled 1050 women during their admission to the delivery room (2012-2013). Information on pregnancy and risk factors was collected from a hospital registry and an interview. Ambient measurements of 24-hour average NO2 and temperature were obtained from 5 local monitors and assigned to each woman, based on a distance from the closest monitor and limited to women residing within 20km. Exposure was estimated as an average value of NO2 for the first trimester. Log-binomial regression was used for adjustment. As a sensitivity analysis, Generalized Estimating Equations were employed on NO2 daily measurements adjusted to distance from a monitor. Results: Median value of daily NO2 measured in the area was 6.3 ppb (inter-quartile range: 4.3-8.7). CM was diagnosed in 8.1% (85) of offspring. Based on multivariate analysis, maternal NO2 exposure during the 1st trimester was borderline associated with CM (RR=1.50, 95%CI: 0.97-2.32, p=0.066), also confirmed by sensitivity analyses. Mothers to offspring with CM, were more likely to use open fire for cooking (RR=2.70, 95%CI: 1.22-6.11, p=0.013). Maternal age and consanguineous marriages rate was similar between mothers to newborns with and without CM (28±6 years and 47.6% in the whole study population). Conclusions: NO2 exposure in early pregnancy was borderline associated with CM in Bedouin-Arab population. Household factors had a greater impact on CM elevated rates compared to ambient exposure.