Associations between maternal residential proximity to hazardous waste sites and adverse birth outcomes in North Carolina

Abstract

BACKGROUND AND AIM: Human health effects of hazardous waste sites (HWS) are a topic of scientific and public concern. We conducted a retrospective cohort study to investigate relationships between residential proximity to HWS in North Carolina (NC) and two adverse birth outcomes that have previously been shown to be associated with pollution and other environmental exposures: preterm birth (PTB, 37 weeks completed gestation) and term low birth weight (LBW). METHODS: We developed a comprehensive geodatabase of all HWS in NC including toxic industrial sites, superfund sites, and landfills. Using birth certificates, we assembled a cohort of 1,597,635 births in NC from 2003-2015, and geocoded the maternal residential address provided on the birth certificate. PTB (N=170,406) and LBW (N=42,368) were ascertained from the birth certificate. We used log-binomial regression models to estimate adjusted risk ratios (aRR) and 95% confidence intervals (CI) for associations between exposure to HWS (defined as maternal residence within one mile of HWS) and each outcome individually, adjusting for maternal age, maternal smoking, maternal Medicaid status, and maternal education. RESULTS:We observed weak associations between residential proximity to HWS and both PTB [aRR(95% CI): 1.06(1.04,1.07)] and LBW [1.09(1.07,1.12)]. Secondary analyses examining exposure to different types and characteristics of HWS found higher risk of LBW among births exposed to toxic industrial sites [1.09(1.06,1.12)] and superfund sites [1.14(1.08,1.21)], compared to births exposed to landfills [0.95(0.87,1.04)]. Additionally, risk of LBW was slightly greater among births exposed to HWS emitting toxins into water [1.13(1.08,1.21)], compared to HWS with either land emissions [1.09(1.06,1.12)] or air emissions [1.10(1.07,1.13)]. CONCLUSIONS:This study contributes to the growing body of evidence regarding potential reproductive health effects of HWS. We explored heterogeneity in the associations between maternal residential proximity to HWS and adverse birth outcomes by differentiating between different types of HWS and including information about the specific characteristics of each HWS. KEYWORDS: hazardous waste sites, adverse birth outcomes, preterm birth, low birth weight, GIS