Lead exposure has long been known for its harmful effects on judgment, cognitive function and behavior, but two new studies have revealed that the children exposed to lead early in life may develop criminal behavior in adulthood.
Part of the Cincinnati Lead Study, the two studies revealed that exposure to lead in early childhood can shrink the brain and probably contributes to violent criminal activity in young adulthood.
In the first study led by Kim M. Cecil, an imaging scientist at the University of Cincinnati College of Medicine, the reseachers conducted MRI scans of the brains of 157 people, who were part of the Cincinnati Lead Study since infancy. The researchers collected and studies their blood lead levels every three months until the participants were 5 years old, every six months until they were 6 or 7 years old, and several more times during their teen years. They found that those who had the highest lead exposures as children had significantly smaller brain volumes. They found lead influencing mainly in areas of the brain called the pre-frontal cortex and anterior cingulate cortex, associated with judgment, attention, decision-making, and impulse control.
“The most important message is that lead affects brain volume, independent of demographic and social factors that are often used to explain away poor outcomes. This is independent biological evidence showing that the brain is affected by lead,” Cecil said.
In the second study, researchers led by Kim N. Dietrich, at the University of Cincinnati College of Medicine, followed the same subjects and measured their blood lead exposure against their arrests at age 18 and older.
The researchers found that the chances of committing a violent crime increased by 30 percent with each increase of 5 micrograms per deciliter in the average childhood level of lead in the blood. They concluded that the higher the lead level in the body, the greater the chance a person would commit a crime.
Dietrich said, "We have seen effects of lead below 5 micrograms [per deciliter]." The effects include include attention deficit disorder, hyperactivity, and conduct and cognition disorders. “There are some data that suggest that in fact lead does run in parallel with crime trends over the past several decades. Lower income, inner-city children remain particularly vulnerable to lead exposure,” Dietrich said.
Sponsored by the Public Library of Science, a nonprofit organization founded to provide free and immediate access to peer-reviewed studies, the two studies were published in yesterday's edition online journal PLoS Medicine, a journal published by the Public Library of Science.