Dietrich and colleagues signed up pregnant women living in Cincinnati neighborhoods ridden with lead-contaminated housing between 1979 and 1984. They tested the women and then their children from birth and have been watching the children as they grew up.

Those with high lead levels before birth and during early childhood had higher rates of arrest than 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 serious motor vehicle violations.

They found more than 1 percent of total gray matter in the brain 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 is responsible for mood regulation and decision-making.

Men were far more affected than women.