WEDNESDAY, May 28, 2008 (HealthDay News) -- Children who are exposed to lead at a young age are more likely to be arrested later in life.
A study in the May 27 issue of PLoS Medicine is the first empirical evidence that elevated blood lead levels, both in the pregnant mother and in the child, are associated with criminal behavior in young adulthood.
"I never would have thought that we would be seeing these effects into the later 20s," said study co-author Kim Dietrich, a professor of environmental health at the University of Cincinnati. "I'm actually quite astounded and quite worried about this. Although lead levels have been going down in this country, a large proportion of the population now in their 20s and 30s had blood levels in this neurotoxic range."
Childhood lead exposure has been linked with anti-social behavior, lower IQ, attention deficits, hyperactivity and weak executive control functions, all of which are risk factors for future delinquent behavior (attention-deficit hyperactivity disorder, in particular, is a risk factor for adult criminal behavior). Studies have also related sales of leaded gasoline or high atmospheric lead levels with criminal behavior.
Although use has been curtailed recently, in the past lead was widely used in paint, solder for water pipes and gasoline. The U.S. government banned lead paint and solder in 1978 and 1986, respectively. By 1996, leaded gasoline had been phased out. These efforts resulted in a dramatic decrease in the number of U.S. children with blood lead levels considered "of concern" (from 13.5 million in 1978 to 310,000 in 2002).
But many older buildings, especially those in poor, inner-city neighborhoods, still have lead paint on the walls and windowsills. Earlier this year, the U.S. government issued new rules designed to protect children from exposure to lead-based paint during repairs and renovations to homes and buildings. The new rules will take effect in 2010.
Dietrich's paper is part of a larger study initiated in 1979 to study the effects of both prenatal and early childhood lead exposure on the growth and development of children. Pregnant women recruited into the study lived in areas of Cincinnati with a high concentration of older, lead-contaminated housing.
For the current report, researchers looked at maternal blood lead concentrations during pregnancy as well as concentrations in 250 children at regular intervals until they were almost 7. Arrest and incarceration information taken from county records years later was correlated with those blood lead levels.
Arrest rates were higher as blood lead concentrations went up. The association between high blood lead levels and violent crimes was even stronger. Any 5 micrograms per deciliter elevation in blood lead levels increased the rate of arrest for violent offenses by more than 25 percent, Dietrich said.
This was true even after adjusting for a multitude of other factors.
"In essence, we stripped away the variants that could be accounted for by early home environment -- their health at birth, mother's ingestion of drug and alcohol during pregnancy, their own ingestion of drugs postnatally and as adolescents and as young adults," Dietrich explained.
A companion paper in the same issue of the journal found that, based on MRI data, exposure to lead during childhood was associated with reductions in gray matter volume in the brain in adulthood. The reductions were related to specific regions, including those responsible for executive function, mood regulation and decision-making. The reductions were more striking in males than females.
"This is shedding new light that no dose is safe for lead," said Kim Cecil, co-author of the companion paper and an associate professor of radiology, pediatrics and neuroscience at the University of Cincinnati College of Medicine and Cincinnati Children's Hospital.
And while lead has been largely removed from the landscapes of developed countries, the same is not necessarily true in other parts of the world, Cecil pointed out.
Even in the United States, more could be done, Dietrich said.
"The Office of Management and Budget estimated that nearly 60 percent of children on Medicaid are not being screened [for lead exposure], as they should be," he said. "And a recent study in Michigan found that 40 percent of children with blood levels in the neurotoxic range were never followed up."
The U.S. Environmental Protection Agency has more on lead.