May 29, 2001 -- Exposure to lead is known to cause learning problems in children, and many health officials feel the government and industries should do more to remove it from our environment. Now, a new study finds there may be yet another reason to "get the lead out."
The study suggests that lead exposure may make people more prone to engage in violent behavior -- even homicide. The findings appear in the May issue of the Archives of Pediatric and Adolescent Medicine.
Researchers Paul B. Stretesky, PhD, a sociologist at Colorado State University in Fort Collins, Colo., and Michael J. Lynch, PhD, a criminologist at the University of South Florida in Tampa, looked at levels of lead in the air in over 3,000 counties in the contiguous U.S. They found that counties with the highest levels of lead in the air had a murder rate four times higher than areas with the least lead in the air.
"This is another study that falls in line with the rest of the research that's says lead is bad," Stretesky tells WebMD. Exactly how lead may affect behavior is not understood, but lead is known to be toxic to the brain, he says.
Previous research has suggested that children exposed to lead have significantly greater odds of developing delinquent behavior. One study compared 216 youths convicted in the Juvenile Court of Allegheny County, Penn., and 201 nondelinquents from high schools in Pittsburgh. Delinquent youths had significantly higher concentrations of lead in their bones, compared to the nondelinquent teens.
"There is increasingly compelling evidence that there is a link to behavioral problems and aggressive behavior, in particular among children exposed to lead," says Bruce Lanphear, MD, associate professor of pediatrics at Children's Hospital Medical Center in Cincinnati.
The link with crime is a little more recent, he says. "But the combined and cumulative evidence of all studies really begins to raise some important questions," Lanphear tells WebMD.
"The best we can say is that lead is a neurotoxin, but we don't know how it's causing aggressive or delinquent behavior, but there seems to be an association, that although not definitive is compelling enough not to be disregarded," he says.
The effect seems to cut across different social strata and ethnic groups.
"The message is that we really need to push for more aggressive regulations to prevent childhood lead exposure from substandard housing and to demand standards from the Environmental Protection Agency to adequately protect children," says Lanphear.
"The association [between lead exposure and violence] is still in its infancy in terms of research," says James R. Campbell, MD, MPH, associate professor of pediatrics at the University of Rochester (N.Y.). "It may be true, but more work needs to be done."
However "if it's true," he says, "it definitely points to an impetus for doing more things to get rid of lead."
Lead is associated with decrease in IQ levels and/or learning disability among children, he says
In addition, studies in rodents have shown that lead may decrease bone density. Low bone density is risk factor for developing the osteoporosis later in life.
How do children get exposed to lead?
"We still see lead in older homes built before 1960 where lead-based paint was used," he tells WebMD. When these homes are in poor condition and the paint is deteriorating, a child often eats paint chips off the floor. Even harder to spot, "deteriorated paint becomes part of the dust in the home and young children play on floor and then stick their hands in their mouth," he says.
Lead is widespread in the environment, and people absorb lead from a variety of sources every day. Although lead has been used in numerous consumer products, the most important sources of lead exposure to the general population include soil and dust, drinking water (from corrosion of plumbing systems), lead-based paint, occupational exposure, or hobbies,
So what's a parent to do?
"Part of the scary thing is that if your child has lead exposure, there will not be any overt, obvious symptoms that will prompt a parent to say 'let's have this looked at,' " says Campbell. Children who are exposed to lead may be more irritable, move around more, or have stomach pain, but these behaviors/symptoms still fall within the range of what is considered normal, he explains.
The general approach is to have children tested at ages 1 or 2, particularly those children living in older homes, he says. Blood lead levels are the principle indicator of lead exposure.
"If blood lead levels are above 10 mcg per deciliter of blood, some interventions should be done to find the source of lead and do something about it," he says.