Air Date: Week of May 19, 2000

For the past 30 years, Doctor Herbert Needleman has been researching the effects of lead poisoning in children. Living On Earth’s Diane Toomey spoke with Dr. Needleman about his latest study, in which he looked at the lead levels in the bones of juvenile delinquents and compared the results to levels found in other children.

Transcript

CURWOOD: A new study suggests that millions more U.S. children than previously thought are suffering ill effects from exposure to lead. Researchers at Children's Hospital Medical Center in Cincinnati looked at lead levels in close to 5,000 children over the span of six years. Up until now, a blood lead level of 10 micrograms per deciliter was considered acceptable. Using that standard, one in 20 U.S. children between the ages of one and five is adversely affected by lead. But researchers in the new study found that short-term memory, as well as reading and math ability, were all affected at lead levels as low as 2.5 micrograms. If substantiated, that puts nearly half of young children at risk. This research was recently made public at the Conference of the American Academy of Pediatrics in Boston. Dr. Herbert Needleman of the University of Pittsburgh presented another study at the same conference. His research found apparent links between lead and juvenile court convictions. Living on Earth's science editor Diane Toomey speaks now with Dr. Needleman about these results.

TOOMEY: Dr. Needleman, you published a study a few years ago that found that children with relatively high levels of lead in their bones were twice as likely to be aggressive, engage in antisocial behavior. What's the difference between that previous study and this current work? How does this study push this area of research along?

NEEDLEMAN: In this study we identified young people who had been arrested and adjudicated by the juvenile court as delinquent. And compared their bone lead levels to a control group from similar high schools who had neither been arrested nor adjudicated as delinquent.

TOOMEY: So, what is the difference between the level of lead in the bones of juvenile delinquents, compared to other children?

NEEDLEMAN: In our study, the delinquents had considerably higher levels of lead in their bone. In the male group, the mean blood lead level was 11 parts per million in the delinquents, as opposed to three and a half in the control group. In the females the difference was even greater.

TOOMEY: Statistically speaking, those are very large differences, aren't they?

NEEDLEMAN: They're highly significant statistically.

TOOMEY: Well, why would a child's exposure to lead lead to criminal behavior?

NEEDLEMAN: Well, lead's a brain poison. And one of the places it seems to involve are the pre-frontal lobes of the brain, where impulsivity is regulated, making choices between one option and another. And the lead appears to affect the central nervous system function in those areas.

TOOMEY: So it kind of takes the brakes off of things, so to speak.

NEEDLEMAN: Yeah. We all have hostile impulses, but most of us are able to think it through and say, if I do this, I'm going to get punished. It seems that delinquents have a defect in that area.

TOOMEY: The simplistic way to look at this would be to say that lead poisoning causes crime, but the picture I'm sure is more complicated than that. For instance, I know in some parts of Africa, 90 percent of children suffer from toxic lead levels, but we don't hear a lot about juvenile delinquency in that part of the world. So, does lead cause crime?

NEEDLEMAN: I don't think lead is a single cause for crime. I think it raises the risk for criminal behavior. This is not a new discovery. Randolph Byers at the Boston Children's Hospital, over 60 years ago, was referred two children for violent behavior, and he recognized them as children who had recovered from lead poisoning. And mothers of lead-poisoned children have told me and other pediatricians that their child was once sweet-natured, easy to manage, and after recovering from lead poisoning wouldn't listen to directions, wouldn't sit still, and if frustrated will pick up whatever is at hand to hit somebody. So the clues have been out there that lead affects the nervous system, reduces controls, and increases the rate of antisocial behavior.

TOOMEY: So if high levels of lead don't necessarily cause crime, are we talking about a nature-nurture situation here? Some children maybe have toxic levels of lead in their system, but their environment is such that it doesn't lead to a life of criminal behavior.

NEEDLEMAN: I would say, rather than a nature-nurture problem, it's a multivariate problem. In order to have your ability to control yourself impaired, you probably need a few things. And in children who have a lot of lead, you probably don't need as much of the other risk factors to cross the line and to transcend the boundaries of what's considered legitimate behavior.

TOOMEY: Dr. Needleman, what are the public policy implications for these findings?

NEEDLEMAN: The brain has been neglected in large measure in the study of antisocial behavior. Lead is the best understood neurotoxicant. We know where lead is. We know what it does. I believe we have more information about lead than any other toxicant. And we know how to get rid of it. And in doing so, I think we would reduce the rate of criminal behavior.

TOOMEY: Dr. Needleman, what research do you have upcoming with regard to lead poisoning?

NEEDLEMAN: Mothers of children who recovered report that they don't pay attention, and we have shown, as have many other people, that lead does affect attentional function. It's distractability, impulsivity, which we talked about. But another question is, does it cause attention deficit? That is, does it bring children into the range of diagnosis of this strange disorder? And so, we're doing a case control study of 250 children who have the diagnosis of ADHD, and a suitable group of controls.

TOOMEY: Dr. Herbert Needleman is a professor of psychiatry and pediatrics at the University of Pittsburgh Medical School. Dr. Needleman, thanks for speaking with us today.

NEEDLEMAN: Thank you very much.

CURWOOD: Living on Earth's science editor Diane Toomey, speaking with the University of Pittsburgh researcher Dr. Herbert Needleman.