Lead Exposure Linked to Antisocial Behavior
CINCINNATI, Ohio, March 1, 2002 (ENS) - Exposure to lead in childhood could lead to antisocial or even criminal behavior in adults, a new study suggests. The first comprehensive lead study to track children over a period of time found that both prenatal and postnatal exposure to lead were associated with antisocial behavior in children and adolescents.
"It appears that the neurodevelopmental effects of this avoidable environmental diseases of childhood may not be limited to declines in IQ or academic abilities," said Dr. Kim Dietrich, associate director of Cincinnati Children's Environmental Health Center and the lead author of the study.
Researchers at the Environmental Health Center at Cincinnati Children's Hospital Medical Center, in collaboration with University of Cincinnati researchers, followed inner city adolescents recruited into the study before birth between 1979 and 1985. Mothers known to be addicted to drugs or alcohol, diabetic, or those with proven neurological disorders, psychoses or mental retardation were excluded from the study.
Between 1997 and 1999, 195 of these adolescents received follow up exams. Ninety-two percent were African American and 53 percent were male.
Blood lead levels were taken from mothers during pregnancy and from children every three months between birth and age six, covering the time period when most developmental growth involving the brain occurs.
Researchers asked the adolescents and their parents or legal guardians to document antisocial or delinquent behavior. This method of self reporting has been proved to be more valid than official records, which reflect only a small portion of antisocial acts actually committed, the researchers explained.
"Self reported acts of delinquent behavior were common," said Dietrich. "Adolescents with the highest blood lead concentrations when they were first graders reported, on average, 4.5 more delinquent acts in the previous 12 months compared to children with the lowest blood lead concentrations as first graders."
Delinquency was defined as behaviors in violation of legal statutes involving some risk of arrest, including offenses against property or persons, or other illegal activities such as driving without a license and disorderly conduct.
The researchers found that exposure to lead was associated with antisocial behavior, even after adjusting for other factors that could lead to similar behavior. These included quality of home environment, low birth weight, parental intelligence and social class.
To their surprise, the researchers found no gender differences in antisocial behavior. Girls were just as likely as boys to be violent and to be institutionalized for their behavior.
While lead could be interfering with the usual gender differences seen in behavior, it is more likely that gender is becoming less a predictor of behavior in inner city populations, said Dr. Dietrich, professor of Environmental Health and Pediatrics at the University of Cincinnati.
The study, which appears in the journal "Neurotoxicology and Teratology," supports previous work at the University of Pittsburgh that suggested that children exposed to lead have significantly greater odds of developing delinquent behavior.
University of Pittsburgh researcher Dr. Herbert Needleman, professor of child psychiatry and pediatrics, examined the bone lead levels of 216 youths convicted in a juvenile court and 201 non-delinquent controls from high schools in Pittsburgh.
"Of all the causes of juvenile delinquency, lead exposure is perhaps the most preventable," said Needleman. "These results should be a call to action for legislators to protect our children by requiring landlords to not simply disclose known instances of lead paint in their properties, but to remove it."
These reports join a growing body of evidence linking lead to health, cognitive and behavioral problems in children. In the U.S., almost a million children under the age of six suffer from lead poisoning.
Lead exposure can cause permanent damage to the brain and other organs. Research shows that children with elevated blood lead levels are seven times more likely to drop out of school and twice as likely to lose a few years in language acquisition.
Prior studies by Needleman linking lead exposure to lower IQ scores, short attention spans and poor language skills helped prompt nationwide government bans on lead from paint, gasoline and food and beverage cans.
But there are still a number of ways in which children, and adults, may be exposed to lead. Most children who suffer from lead poisoning are exposed to invisible lead dust that is released when older paint is peeling, damaged or disturbed, or by eating chips of lead paint.
Drinking water that comes from lead pipes or lead soldered fittings can expose children to lead, as can breathing air contaminated by the lead smelting, refining and manufacturing industries.
Tobacco smoke contains some lead, and hobbies that use lead, such as leaded glass ceramics, can cause environmental exposures. Eating contaminated food grown on soil containing lead or food covered with lead containing dust is another source of exposure.
Problems from lead exposure are not limited to children. A study by researchers at Johns Hopkins School of Hygiene and Public Health, found that lead exposure on the job can cause progressive declines in memory and learning abilities nearly two decades later.
Another study, from Case Western Reserve University and University Hospitals of Cleveland, Ohio, demonstrated that people who have worked in jobs with high levels of lead exposure are up to 3.4 times more likely to develop Alzheimer's disease
"Although lead has long been known to be toxic - and is believed to have affected the brains of some of the rulers of the Roman Empire, thereby causing its downfall - its long term damages are difficult to measure," said Elisabeth Koss, PhD, lead author of the study. "The extent of its negative effects have been largely overlooked."
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