Abstract
BackgroundInconsistent results continue to be reported from studies linking low-level prenatal lead exposure and child development. Because of limited earlier epidemiological studies with birth cohort follow up design, it still remains inconclusive that either the associations of cord blood level of toxic, and essential elements, and postnatal raising environment on neurodevelopment of children remains constant throughout childhood or change over time.AimsThis study aims to investigate the influence of in utero toxic [lead (Pb) and arsenic (As)] and essential elements [zinc (Zn)] levels on neurodevelopment of 36 months children in Chitwan valley, Nepal taking the postnatal environment into account.Study Designs and SubjectsIn this birth cohort study, participants (N=100 mother-infants’ pairs) were recruited in Chitwan district, Nepal. We measured Pb, As and Zn concentrations in cord blood. Postnatal raising environment (i.e., Home score or home environment hereafter) was evaluated using Home Observation for Measurement of Environment (HOME) scale. Neurodevelopment of children at 36 months of age (n=70) were assessed using Bayley Scale of Infant Development, Second Edition (BSID II). Multivariate regression was performed (n=70) to see the association of in utero toxic and essential elements level and home environment with neurodevelopment score adjusted for covariates.ResultsCord blood levels of Pb, As and Zn were not associated with any BSID II cluster scores of 36 months children. The children with relatively superior HOME score and concurrent nutritional status (weight at 36 months) showed better cognitive development (i.e., MDI scores) and motor functions than their counterparts, respectively.ConclusionIn this general population in Nepal, prenatal Pb, As and Zn levels are not important determinants of the neurodevelopment of 36- month-old children while a consistent beneficial effect of a stimulating home environment on neurodevelopmental indicators is continued.
Highlights
The detrimental effects of in utero toxic elements exposure with later neurodevelopment have been well established at higher exposure levels [1,2,3]
Cord blood levels of Pb, As and Zn were not associated with any BSID II cluster scores of 36 months children
Further investigation about the shape of the dose-effect relationship between lead exposure and neurodevelopment at quite low levels will be helpful to understand the controversies that continue to exist. It remains inconclusive in lower exposure levels whether the associations between cord blood levels of toxic elements or neurodevelopment of children remains persistent throughout childhood or changes over time
Summary
The detrimental effects of in utero toxic elements exposure with later neurodevelopment have been well established at higher exposure levels [1,2,3]. Results from earlier cohort studies indicated that if the prenatal exposure level is high, an inverse association between in utero exposure of Pb and neurodevelopmental indicators continues to exist from birth to 3 years consistently [1,2,3]. We have recently reported the inverse association of in utero toxic elements exposure (e.g., Pb mean 20.6 μg/L and As 1.33 μg/L) with neurodevelopment of infants [9] but could not detect such an association at 6 [10] and 24 months [11] It is not clear whether these associations remain constant throughout childhood or change (i.e., re-emerge as delayed onset) by the time of 36 months. Because of limited earlier epidemiological studies with birth cohort follow up design, it still remains inconclusive that either the associations of cord blood level of toxic, and essential elements, and postnatal raising environment on neurodevelopment of children remains constant throughout childhood or change over time
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