Effect of Timing of Lead Exposure in Early Life on Childhood Neurobehavioral Outcomes

摘要

Background: The impact of lead exposure on neurobehavioral development remains unclear with regard to critical windows of exposure in early life. Aims: The aim of this study was to compare the relative impact of lead exposure at different time periods of early life, childhood and adolescence on measures of behavioral performance. Method: Data from 583 mother-infant pairs with births between 1997 and 2001 in Mexico City was used for this analysis. Prenatal lead exposure was estimated from maternal blood collected at each trimester and from cord blood at delivery. Postnatal exposures were assessed in offspring's blood every 6 months in the first four years post-delivery and at the behavioral tests when children were 6 to 13 years of age. Behavioral outcomes were assessed with Behavioral Assessment System for Children 2, Conners' Rating Scales and Conners' ADHD/DSM-Ⅳ Scales. Linear regression was used to assess the relationships between lead exposures and behavioral outcomes. Results: Cumulative/integrated maternal gestational blood lead measures had mean±SD values of 3.37±1.88 μg/dL. Cord blood lead level was 4.99±3.28μg/dL. Children's cumulative/integrated blood lead level from the first two years was 9.01±5.27μg/dL and from the second two years was 12.06±4.73 μg/dL and was 2.97±2.07 μg/dL at the time of behavioral testing. Cord blood lead was a strong predictor for greater perfectionist behavior. Cumulative blood lead in the 3rd and 4th years post-delivery significantly predicted greater inattention/hyperactivity behavior. Compared to blood lead later in childhood, blood lead prenatally and in the first two years of life had a greater adverse impact on standardized effect estimates of behavioral outcomes. Conclusion: Lead exposures during the prenatal period and in the first two years of life have strong and long-lasting impacts on behavioral problems in childhood/ early adolescence.