Identifying periods of heightened susceptibility to lead exposure in relation to behavioral problems

Background Lead exposure is associated with behavioral problems in children, but the age(s) of greatest susceptibility to low-level lead exposure is unknown. Objective We evaluated the association of repeated blood lead concentrations with parent-reported behaviors to identify periods of heightened susceptibility during infancy and childhood (HOME Study; Cincinnati, OH; 2003-2006; n = 244). Methods We quantified lead in whole blood samples (ages 1, 2, 3, 4, 5, and 8 years) and assessed behavior using the Behavioral Assessment System for Children-2 (BASC-2; ages 2, 3, 4, 5, and 8 years). We used multiple informant models and modified Poisson regression to estimate covariate-adjusted associations of ln-transformed blood lead concentrations with continuous BASC-2 T-scores and the relative risk of behavior scores classified as at-risk or clinically significant, respectively. Results We observed trends indicating that higher blood lead concentrations at all ages were adversely associated with scores on behavioral scales. On the Externalizing Problems and Adaptive Skills scales, these associations were strongest for blood lead concentrations at age 8 years (beta = 3.1-point; 95% CI = 0.7, 5.4 and beta = -2.2-point; 95% CI = -4.9, 0.5, respectively) compared with other ages. Overall, higher blood lead concentrations were associated with elevated risk of behavior scores classified as at-risk or clinically significant on the Adaptive Skills, Behavioral Symptom Index, and Externalizing Problems scales. Significance Contemporary levels of lead exposure during the first 8 years of life were associated with ADHD-related behaviors, specifically aggression, hyperactivity, and conduct problems. Impact statement Our results highlight the importance of primary lead prevention across childhood.