The link between exposure to lead and children’s cognitive problems was implied in the earliest medical reports of frank lead poisoning of young children in Australia in the 1800s (Lin-Fu 1992). Children with acute severe toxicity of lead (Pb) are now rarely seen in the United States. However, millions of children may have subclinical neurobehavioral disorders associated with chronic low-level exposure to lead, representing a major public health concern (Bellinger 2008a). Lead is a nonessential metal that is recognized as a source of toxic exposure, with the developing nervous system particularly vulnerable. Because of this, U.S. regulations limiting the lead content of gasoline and household paint have led to a gradual reduction of the average blood lead concentration of Americans over the last three decades. Average blood lead levels of children in the United States dropped an estimated 78% from 1976 to 1991 (Brody et al. 1994; Caldwell et al. 2009). Despite these reductions in exposure to lead, new advances in research techniques have documented harmful consequences associated with lower blood lead levels. This raises the possibility that there is no threshold for occurrence of lead-induced toxicity. Bellinger (2008a) refers to “the silent pandemic of neurodevelopmental disorders resulting from children’s continuing exposure to low levels of lead.” The developing brain may be more sensitive to exposure to lead than the adult. Since the pioneering work of Needleman and colleagues (1979), a large scientific literature has documented the deleterious effects of pre- and neonatal exposure to lead. Decrements in IQ scores have proven to be among the most sensitive and consistent consequences of a child’s exposure to lead, but other cognitive and behavioral changes have been described as well, including attention-deficit hyperactivity disorder (ADHD). Among the important current sources of children’s exposure to lead is household dust (Dixon et al. 2009) the lead content in old water pipes, batteries, and from contamination by numerous industrial processes. Pre and postnatal exposure to cigarette smoke is a cofactor with lead exposure in children’s conduct disorders (Braun et al. 2008). Diagnosis of lead-induced disorders involves the determination of exposure to lead and the atomic absorption assay of lead in whole blood.
Children's mental health and collective violence: a binational study on the United States-Mexico border
