Mediator Role of Air Pollution, Heat, and Noise on the Association Between Maternal Residential Proximity to Major Roads and Term Low Birth Weight

Abstract

BACKGROUND: Maternal residential proximity to major roads has been associated to a range of adverse pregnancy outcomes; however, there is no available study investigating mediators of such an association. AIMS: To investigate the association between term low birth weight (LBW) and maternal residential proximity (200m) to major roads and to explore mediating roles of air pollution (PM2.5, PM2.5-10, PM10, PM2.5 absorbance, NO2, NOx), heat, and noise in this association. METHODS: This study was based on 6,487 singleton term births occurred in Barcelona (2001-2005). We assessed individual exposures to air pollution, noise, and heat using respectively temporally-adjusted land use regression models, average of environmental noise levels across 50m and 250m buffers based on the European Noise Directive strategic noise map, and average of satellite-derived land surface temperature in 50m buffer around each residential address. The association between term LBW and proximity to major roads and mediator, we used logistic regressions, adjusted for relevant covariates. We assessed the mediating role of air pollution, heat, and noise exposures by quantifying the change in the OR for the proximity to major roads after including the mediators (one at a time) alongside the indicator of the proximity to major roads in fully-adjusted models. RESULTS: Proximity to major roads and an interquartile-range increase in heat exposure and the third trimester exposure to PM2.5, PM2.5-10, and PM10 were associated with respectively 46%, 22%, 24%, 25%, and 26% increase in term LBW risk. 19.7% and 11.8% of our observed association between residential proximity to major roads and term LBW could be explained byair pollution (PM2.5) and heat exposures respectively. Air pollution (PM2.5) and heat together could explain about one-third of this association. CONCLUSION: Our observed increased risk of term LBW associated with proximity to major roads was partly mediated by air pollution and heat exposures.