In 1971, the U.S. Centers for Disease Control and Prevention (CDC) investigated lead exposure in El Paso, Texas, and discovered its effects on children’s brain and neural development. Subsequently, a Surgeon General’s report defined a blood lead concentration of 40 ﾵg/dL to be considered evidence suggestive of ‘undue absorption of lead, either past or present,’ and defined ‘lead poisoning,’ as confirmed, on 2 successive determinations, BLLs of 80 ﾵg/dL or more with or without symptoms. The CDC became involved in defining the criteria for interpreting BLLs in children issuing its first statement on ﾓIncreased Lead Absorption and Lead Poisoning in Young Children.