Association Between Exposure to Metal Mixtures, Dietary Patterns, and Growth of Infants and Children

Objectives: This dissertation aimed to examine the influence of exposure to metal mixtures on growth-related outcomes in early life. Further, since evidence is limited with respect to the potential mediating role of exposure to metals in the relationship between dietary patterns and growth of children, we also evaluated such associations in this dissertation. Methods: In analyses of data from the Bangladesh Environmental Research in Children’s Health Cohort (BIRCH), we assessed the effects of exposure to seventeen metals, as measured in toenails, on growth of children aged 5-7 years by implementing principal component analyses (PCA), weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR). Using the same data source, we further evaluated the potential mediating role of metal exposures in the association between dietary patterns and growth of Bangladeshi children. In analyses using the United States (U.S.) National Children’s Study (NCS), we performed PCA, WQS, ad BKMR to analyze 1st trimester blood concentrations of five metals and 3rd trimester urinary concentrations of twelve metals in relation to birth outcomes. Results: Analyses using BIRCH data suggested inverse joint effects of metal mixtures on growth-related outcomes; cadmium, uranium, and arsenic were identified as important metals driving these associations. In addition, copper and selenium were positively associated with growth of children. Four dietary patterns (varied diet, traditional diet, sweet and water diet, and protein diet) were identified and all of which showed positive impacts on growth of children. The positive associations of the varied diet with growth-related outcomes were significantly mediated by greater toenail selenium concentration. Analyses using NCS data found positive trends between exposure to 3rd trimester urinary metal mixtures and birth length and head circumference; arsenic was identified as the primary metal driving these associations. We also found negative joint effects of 1st trimester blood metal mixtures on birthweight and ponderal index. Couclusions: This dissertation work identified certain metals that may have detrimental or positive impacts on growth of infants and children with consideration of co-exposure patterns. We also identified certain dietary patterns that could be beneficial to children in Bangladesh regarding their linear growth.