The impact of traffic-related pollution and temperature on adverse birth outcomes in Madrid. An analysis of time series

Abstract

Preterm birth (< 37 weeks), low birth weight (< 2500 g) and fetal mortality are perinatal morbi-mortality causes impacting public health, society and the economy. Their etiology is multifaceted. There is scientific evidence pointing to environmental variables being risk factors. The purpose of this study was to analyze and quantify the impact on a daily and a weekly basis of PM2.5, NO₂ and O₃ (μg/m³), noise levels (Leq), and temperature (°C) on variables detrimental to health in Madrid from 2001 till 2009. Poisson regression models were prepared from an ecological study of time series, and the results were expressed in terms of the Relative Risk (RR). The environmental variables were included in previously identified explanatory delays. 298,705 births were analyzed: the average weekly prematurity was 7.5, the average low weight 6.9, and the average fetal mortality 3.7. In the case of preterm births, a relation with PM2.5 during the 2nd quarter of pregnancy [RR: 1.026 (1.018-1.034)] and with Leq in the week prior to childbirth [RR: 1.020 (1.012-1.028)] was detected. This impact was also noticeable in the daily results. In addition, heat waves also affect prematurity. With regard to low birth weight, noise levels had an impact throughout the pregnancy and the effect of NO2 during the 2nd quarter thereof. As for fetal mortality, the most significant effects were those of the three analyzed pollutants during the 2nd and 3rd quarters. The gestating population is a group that is particularly vulnerable to the analyzed environmental factors, so it should be taken into account in the existing prevention plans.