About 38 million U.S. homes, 40% of the nation's housing, still contain lead-based paint, according to the U.S. Department of Housing and Urban Development. The problem is particularly acute in urban areas, which typically have older housing that has not been renovated.
More recently, parents and authorities have become concerned about increasing levels of lead-based paint in toys imported from China.
Researchers have long known that lead exposure reduces IQ by damaging brain cells in children during their early years.
It is also known that lead increases children's distractibility, impulsiveness and restlessness and shortens their attention span, all factors considered precursors of aggressive or violent behavior.
A landmark 1990 paper by Denno linked lead to increases in criminal behavior, but the children in the study were not tested for lead levels. The diagnoses were based on their physicians' evaluation, Denno said.
The Cincinnati lead study enrolled 376 pregnant women in Cincinnati's inner city between 1979 and 1984, measuring their blood lead levels during pregnancy and the children's levels during their first seven years of life.
In the new study, environmental health researcher Kim N. Dietrich of the University of Cincinnati College of Medicine studied 250 of the original group, correlating their lead levels with adult criminal arrest records from Hamilton County, Ohio.
He and his colleagues found that 55% of the subjects (63% of males) had been arrested and that the average was five arrests between the ages of 18 and 24.
The higher the blood lead level at any time in childhood, the greater the likelihood of arrests. "The strongest association was with violent criminal activity -- murder, rape, domestic violence, assault, robbery and possession of weapons," Dietrich said.
Blood lead levels in the children ranged from 4 to 37 micrograms per deciliter.
The researchers found, for example, that every 5-microgram-per-deciliter increase in blood lead levels at age 6 was accompanied by a 50% increase in the incidence of violent crime later in life. Confirming previous findings, the effect of lead was strongest in males, who had an arrest rate 4 1/2 times that of females.
In a related study, spectroscopist Kim M. Cecil of Cincinnati Children's Hospital Medical Center and her colleagues examined a "representative sample" of 157 members of the same group using whole-brain MRI scans. They found that those with the highest blood levels of lead during childhood had the smallest brain volume.
On average, the brains of those in the study were about 1.2% smaller than normal. The most affected regions of the brain were those regulating decision making, impulse control, attention, error detection, task completion and reward-based decision making.
"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" in life, Cecil said. "This is independent biological evidence showing that the brain is affected by lead."
--
thomas.maugh@latimes.com
marla.cone@latimes.com
