(AFP) – May 28, 2008

WASHINGTON (AFP) — In a study spanning a generation, a team of US researchers has linked exposure to lead in the womb and early childhood to a higher rate of criminal behavior among adults.

The researchers from the University of Cincinnati measured the blood lead concentrations in pregnant women living in poor urban areas known to have lead-contaminated housing, between 1979 and 1984.

They then measured the lead levels in the blood of their children, from birth until the age of six-and-a-half.

Years later, when the children in the observation group were between the ages of 19 and 24, the researchers studied the arrest records of 250 of them.

More than half of them -- 55 percent -- had been arrested at least once, and young men were nearly five times more likely to be arrested than young women, the study said.

Previous studies indicate that the developing male central nervous system is "more vulnerable than females' to environmental insults leading to later behavioral problems," according to the researchers' report.

"We identified a total of 800 arrests within the sample," the report said.

"The rate ratio (a basic measure of association) for total arrests increased for each five micrograms per deciliter increment in blood lead concentration," the study said, leading the researchers to conclude that "prenatal and childhood blood lead concentrations were predictors of adult arrests."

The higher the prenatal level of lead in the blood and the blood lead level at age six, the greater the number of arrests.

Furthermore, the higher the average childhood blood lead level, the greater the incidence of arrests for violent crime.

"Childhood lead exposure seems to place individuals at risk for multiple underlying neurobehavioral deficits associated with a higher probability of later criminal behavior," the researchers said.

A study published last year showed that crime rates dropped in nine countries after lead -- a heavy toxic metal that can damage the brain -- was phased out of petrol and paint in the 1970s.

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