Date of Award

May 2014

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Public Health

First Advisor

Jeanne B. Hewitt

Committee Members

David H. Petering, Michael J. Carvan III, Nancy Frank, Alan J. Horowitz

Keywords

Built Environment, Criteria Air Pollutants, Cumulative Traffic Density, Low Birth Weight, Neighborhood Stress Index, Preterm Birth

Abstract

Between 2005 and 2010, infants born to non-Hispanic black mothers experienced a 3-fold elevated risk of infant mortality compared to those born to white and Hispanic mothers. Preterm birth (PTB) and low birth weight (LBW) are strong predictors of infant mortality. To our knowledge, this is the first study of Wisconsin births to evaluate the effect of social and environmental factors on risk of PTB and LBW. We hypothesize that the observed racial inequalities in PTB and LBW are related to traffic density and air pollution. The Milwaukee INFANTS Study used 2005-2010 electronic birth record data (N = 85,045) geocoded to the 2010 Census block level based on maternal residence. Cumulative traffic density and interpolated criteria air pollutant data were used to estimate fetal exposures. Multi-level logistic regression analysis (SAS 9.4) with a multiple imputation step to handle missing data (< 4.7%) was used to examine the effect of traffic density and air pollution on risk of PTB and LBW. We adjusted for established risk factors and a census tract level composite measure of neighborhood stress consisting of low income and lack of access to full grocery stores and transportation. In multivariable models, Milwaukee County (2005-2010) experienced a 1.9-fold increased

prevalence of preterm birth (PTB) and a 2.5-fold increased prevalence of low birth weight (LBW) among infants of non-Hispanic black women, compared to infants of non-Hispanic white women. Risk of PTB and LBW differed considerably by location, as well. In unadjusted models, traffic density demonstrated a linear increase in risk across all birth outcomes (p < 0.0001). Second trimester exposure to PM2.5 was associated with an increased risk of preterm birth, and additionally, across the entire pregnancy for LBW and LBW at term. In the full model, the Neighborhood Stress Index showed a 29% increased risk for PTB, a 44% increased risk for LBW, and a 51% increased risk of LBW at term. These preliminary findings warrant further research in which exposure measures more closely approximate biological uptake of toxicants from mobile and stationary sources. Program planning and policy development are discussed.

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