Here's some recently published facts about leads toxicity in children from the American Academy of Pediatrics
http://pediatrics.aappublications.org/cgi/content/full/116/4/1036
"the Academy's new policy statement confirms that no one any longer believes that 10 ug/dL protects lead-exposed children from harm, or that there is any "safe" level of lead exposure for children. The federal government itself came to this conclusion in 2002: "there is no apparent threshold below which adverse effects of lead do not occur," said the Centers for Disease Control and Prevention (CDC) "
"The main effect of lead is to impair cognition, which is usually measured (after age 5) by an IQ test. Any amount of lead reduces a child's IQ to some degree."
"For children with more than 10 ug/dL of lead in their blood, each additional 10 ug/dL of lead reduces IQ another 2 to 3 points. However, two recent studies have shown that the first 10 ug/dL increase is the most damaging, reducing a child's IQ by "more than 7 points"
"The new policy statement acknowledges that toxic lead is associated with aggressive behavior and delinquency in children"
"Other aspects of brain or nerve function [besides IQ], especially behavior, also may be affected. Teachers reported that students with elevated tooth lead concentrations were more inattentive, hyperactive, disorganized, and less able to follow directions. Additional follow-up of some of those children showed higher rates of failure to graduate from high school, reading disabilities, and greater absenteeism in the final year of high school. Elevated bone lead concentrations are associated with increased attentional dysfunction, aggression, and delinquency. In children followed from infancy with blood lead measurements, self-reported delinquent behavior at 15 to 17 years of age increased with both prenatal and postnatal lead exposure, and bone lead, thought to represent cumulative dose, is higher in adjudicated delinquents. These data imply that the effects of lead exposure are long lasting and perhaps permanent."
"This is another important point in the Academy's most recent policy statement: it reviews evidence showing that harm from lead is irreversible. Physicians used to think (or at least hope) that ending toxic exposure would allow a child to recover lost brain function. That possibility now seems very unlikely."