Researchers are now reporting that lead exposure in early childhood, even as early as in the womb, can lead to permanent brain damage and may cause criminal behavior. Two separate studies indicate that people with high levels of lead in childhood grew up with not only blocks of missing brain cells, but with a propensity for crime, some violent. As a matter-of-fact, the lead effect is so strong it may account for a large percentage of inner-city area crimes, where old houses are likelier to have lead paint, according to Kim Dietrich of the University of Cincinnati in Ohio. Dietrich led one of the studies in the Public Library of Science journal PLoS Medicine.

"There are some data that suggest that, in fact, lead does run in parallel with crime trends over the past several decades," Dietrich said. In collaboration with colleagues, Dietrich signed up pregnant women who lived in lead-contaminated Cincinnati neighborhoods between 1979 and 1984. Researchers tested the women and their children from birth, continuing to follow the children. Researchers correlated blood-lead level data from 250 of the children to criminal arrest records and found those with high lead levels before birth and during early childhood had higher arrest rates compared to those with lower lead levels. About 55 percent of the now-grown children had at least one arrest, 28 percent involving drugs and 27 percent involving serious motor vehicle violations. "Lower income, inner-city children remain particularly vulnerable to lead exposure," Dietrich said. "Although we've made great strides in reducing lead exposure, our findings send a clear message that further reduction of childhood lead exposure may be an important and achievable way to reduce violent crime," Dietrich added.

Dietrich's colleague, Dr. Kim Cecil of Cincinnati Children's Hospital Medical Center, performed magnetic resonance imaging (MRI) scans on the brains of the volunteers and discovered over one percent of total gray matter in their brains was missing. "The most affected regions included frontal gray matter, specifically the anterior cingulate cortex," Cecil's team wrote in a second study. This region of the brain is responsible for mood regulation and decision-making. The study also found that men were far more affected than women. "Our findings also suggest that this structural change is permanent," they wrote. "Usually the effects of lead poisoning are irreversible," Dietrich said.

Despite the numerous scares involving lead in water, imported toys, and some medications in recent months, Dietrich said that lead paint is the greatest source of poisoning and that the mothers studied probably had lead in their bodies from their own childhoods, exposing their babies in the womb. "Many also grew up in these neighborhoods," Dietrich said.

In a third, unrelated study, a team of University of Pittsburgh researchers showed adults can be inoculated with a second wave of lead as they age. Lisa Morrow and colleagues showed that lead can leach into the blood from bones as people age and lose bone mass. This study is documented in the Archives of Environmental and Occupational Health.