Assessment of individual and mixture effects of element exposure measured in umbilical cord blood on birth weight in Bangladesh

Low birth weight is a leading cause of childhood morbidity and mortality globally, especially in low- and middle-income countries. Individual trace element exposure during pregnancy is associated with birth weight; however, information on potential mixture effects of multiple-elements exposure on birth weight are limited. In this study, we assessed the effects of single element and element mixtures on birth weight among 745 mother-infant pairs from a prospective birth cohort established in Bangladesh from 2008 to 2011. Using inductively coupled plasma mass spectrometry, we measured 56 elements in cord blood collected at delivery. Multivariate linear regression was used to evaluate the individual effect of element exposure on birth weight. Then, we also applied regression model based on categorical variables according the interquartile range (IQR) and restricted cubic spline to explore potential non-linear associations. Bayesian kernel machine regression (BKMR) and weighted quantile sum (WQS) regression were used to assess the mixture effects on birth weight. We found significant negative associations between exposure to lithium (Li), manganese (Mn), cobalt (Co), copper (Cu), yttrium (Y), and erbium (Er) and birth weight, while the concentration of selenium (Se) was positively associated with birth weight. Li was identified as the most important predictor of birth weight by WQS regression and cumulative exposure to element mixtures (Li, Mn, Cu, Co, Y, and Er) was associated with decreased birth weight, birth weight decreasing by 64.73 g with per each unit increment of the element risk score (ERS) based on WQS. Interestingly, the presence of Se during pregnancy may attenuate the risk of low birth weight by its main protective and antagonistic effects against toxic elements.