Purpose: Our pilot studies showed that there was a significant relationship between low cord blood levels and scores of neonatal behavioral neurological assessment. The study was further to probe the adverse cognitive effects induced by low-level lead exposure during prenatal and postnatal period.
Method: Totally 362 mothers with their infants located the PRD, Guangdong, China participated in the study during their stay in these center: 141 in the high lead group [umbilical-cord blood lead levels (UCBLLs)≥3.92μg/dl] and 102 in the low lead group (UCBLLs≤1.89μg/dl). The other 137 subjects failed to complete the study for a variety of reasons. Blood Lead levels (BLLs) were measured by atomic absorption spectrophotometry, equipped with a graphite furnace. The developmental functioning of infants and children was assessed with BSID-II. The children's birth outcome and the rest of information were obtained from their medical records or a comprehensive questionnaire from their parents, which contained demographic characteristics, lifestyle, mother's IQ and environmental lead sources, etc.
Results: Of 380, 243 newborns (63.95%) had complete data collection for all variables included at 6, 12, 24 and 36 months of age. The mean UCBLLs for high and low lead group were 5.63±0.32μg/dl and 1.35±0.26μg/dl, respectively. Significant inverse associations have been found between the UCBLLs and the MDI and the PDI. The associations might attenuate over subsequent years. BLLs at 24 months were significantly associated, in an inverse direction, with MDI at 24 and 36 months. The observed trend of cognitive deficit beginning at 6 months of life might persist, and even develop over the coming years. A positive significant effect of home nurture environment was observed on MDI scores at 12, 24, 36 months of age and PDI scores at 24 and 36 months of age.
Conclusion: Our study demonstrates that prenatal and postnatal lead exposure as low as 5μg/dl has an adverse effect on neurodevelopment, best arrested by measuring UCBLLs and BLLs at 24 months of age, and suggest a reference for a blood lead critical value below 5μg/dL. The collective evidence indicate that low lead exposure must be addressed appropriately by health policy makers and argues for an improvement of home nurture environment, i.e., reduce the burden of Pb on children and, strengthen the training of cognitive ability.
Keywords: Cognitive development infants; Prenatal and postnatal lead exposure; Prospective birth study.
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