Lead Neurotoxicity and Disorders of Learning

Preventable and treatable causes of disorders of learning caused by lead exposure can be recognized by heightened awareness of this potential hazard. The Centers for Disease Control using data from many studies of neurobehavioral effects of lead in children and animals, has redefined the lead exposure threshold for clinical and social intervention from 25 micrograms/dL to 10 micrograms/dL. This article reviews the pertinent studies that provide evidence of the effects of lead exposure on development of the nervous system, effects on neural structures involved in memory and learning, and the impact of early lead encephalopathy on adolescent and adult learning skills and cognitive performance. Physicians, teachers, and child care personnel are responsible for identifying children with behavioral signs of subclinical lead intoxication as early as possible. Screening programs and preventive strategies, such as the multitier Centers for Disease Control approach referred to in this article, are necessary. It is no longer reasonable to assume that lead-exposure children not demonstrating severe encephalopathy will recover completely, without residual brain damage after removal from exposure. Sufficient evidence now exists to clearly demonstrate measurable effects of low levels of lead body burden on behavioral and intellectual performance, resulting in learning disorders.