Lead Exposure and Behavior among Young Children in Chennai, India

BACKGROUND Lead exposure has long been associated with deficits in IQ among children. However, few studies have assessed the impact of lead on specific domains of behavior and cognition. OBJECTIVE We evaluated the associations between lead and different domains of neurobehavior and their relative sensitivity to lead. METHODS We determined blood lead levels using a LeadCare instrument in 756 children 3-7 years of age attending pre- and elementary schools in Chennai, India. Anxiety, social problems, inattention, hyperactivity, and attention deficit hyperactivity disorder (ADHD), as well as executive function were assessed in children by their schoolteachers using Conners' Teacher Rating Scales-39, Conners' ADHD/Diagnostic and Statistical Manual for Mental Disorders, 4th Edition Scales (CADS), and the Behavior Rating Inventory of Executive Function questionnaires, with higher scores denoting worse behavior. Analyses were carried out using multivariate generalized estimating equations with comparisons of outcome Z-scores to assess the relative strengths of the associations between log-blood lead and the different domains of behavior. RESULTS Mean blood lead level was 11.4 +/- 5.3 microg/dL. Blood lead was associated with higher anxiety (beta = 0.27, p = 0.01), social problems (beta = 0.20, p = 0.02), and higher scores in the ADHD index (beta = 0.17; p = 0.05). The effect estimate was highest for global executive function (beta = 0.42; p< 0.001). CONCLUSIONS Higher blood lead levels in this population of young children is associated with increased risk of neurobehavioral deficits and ADHD, with executive function and attention being particularly vulnerable domains to the effects of lead.