Kim Dietrich (Courtesy of University of Cincinnati)
A recent study finds removing lead from gasoline and paint 20 years ago could be linked to a drop in national crime rates. But, the story isn't that simple. Host Bruce Gellerman talks with Kim Dietrich, professor of environmental health at the University of Cincinnati College of Medicine, to find out what other factors make certain individuals more likely to commit crimes, and how lead’s involved.
GELLERMAN: Lead is an insidious substance. The human body has no use for the metal. But once inside, it can damage the brain, leading to learning disabilities, impulsive behavior and violence. Now, it seems exposure to lead as a youth can also be linked to crime later in life. A recent study correlated the phase-out of lead in paint and gasoline in the 1970s with crime rates two decades later and found in the words of the researcher Rick Nevins, ‘a stunning fit.’ As the amount of lead in the environment declined, so did the crime rates in nine countries. In fact, Nevins says, the phase out of lead did more to stop violent crime among people who came of age in its demise than any social policy. Kim Dietrich at the University of Cincinnati College of Medicine has also be studying the pernicious effects of lead.
For the past 30 years he’s been following inner-city kids from the time before they were even born until now. Professor Dietrich says the latest findings linking crime and lead are no surprise, but he's got even better evidence.
DIETRICH: Well, even though these ecological studies were generally well done, they’re limited, because they cannot correlate individual lead dose with individual behavior. So, you’re not going to see a one-to-one relationship between lead exposure and engaging in anti-social behavior but the trends are clearly there and the relationships in our particular study in Cincinnati were quite robust.
GELLERMAN: And what did you find?
DIETRICH: What we found was a robust relationship between both exposure to lead in the womb, and during early childhood. And the rate of criminal arrests in these individuals when they were in their early twenties. And this association was strongest for crimes involving violence.
GELLERMAN: So can these numbers help explain the disproportionate numbers of minorities who are incarcerated?
Kim Dietrich (Courtesy of University of Cincinnati)
DIETRICH: It certainly has played a role. Children who are living in our inner cities, who are largely minority, live in—typically live in homes built before 1950—that are in various states of disrepair. And they are exposed to high levels of lead from one principal source—and that’s lead paint residues, which are in their environments in the form of dust in the interior of the homes and as a result of the peeling off, sloughing off the layers of exterior lead paint, there are high concentrations of lead in the soil around their home. So, while in these studies that have associated the decline in crime with the decline in atmospheric lead levels, they focus on the general population. But children growing up in our inner cities are still exposed to high levels of lead and have not benefited as much from the public health efforts to reduce lead in gasoline and in foods and other ambient sources.
GELLERMAN: What about poor nutrition among minorities—does that play a role? Because I know that for example, calcium resembles the lead in terms of the body’s ability to absorb it—
DIETRICH: That’s right and children who have diets that are lower in calcium will absorb more lead than children who children who have calcium-sufficient diets. However, children—whether their diets are sufficient or not, still absorb more lead than adults do because of their physiology. Given the same amount of ingested lead, children will absorb four times or more lead than an adult. But you’re right. Calcium and lead follow the same physiological pathways or stream in our bodies and this results in a cascade of effects in the developing nervous system, resulting in outcomes in the brains ranging from cell death to abnormal branching and establishment of connections of the neurons. So, lead results in this miswired brain that leads to lower intellectual function, learning problems, and academic failure. So children who are frustrated in their learning environments are more likely to turn to anti-social behavior, delinquency, and as adults, crime as an outlet.
GELLERMAN: So if you look at inner cities, if you look at the poor, if you look at their exposure to weapons, you look at their exposure to violence, you look at their exposure to lead, and their poor nutrition. Is this sort of the perfect combination of factors for crime?
DIETRICH: Yes, it's in a sense, the perfect storm. Uh, the environment provides a lot of incentives for crime. The child is in a community where he or she sees violence—the availability of guns, the availability of illicit drugs. So I would say that the inner-city environment provides the weapon, lead pulls the trigger.
GELLERMAN: Would it be an overstatement to say that if we were to reduce lead dramatically from our inner cities, we would see a dramatic drop in violent crime?
DIETRICH: Well, lead does not exist in a vacuum. Lead is contributing to criminal behavior in the context of other social and economic factors that are going on at the same time. But what’s unique about lead is that we don’t have to do complex and politically difficult social engineering, we know how to remove lead from the environment and how to prevent children from being exposed to lead. Engineering lead out of the environment will prove to be a lot easier, and probably cheaper, than removing some of the other factors that contribute to criminal behavior.
GELLERMAN: So if I went to prison, took blood samples of the inmates, would I find that inmates had higher levels of lead in their bodies?
DIETRICH: Not necessarily because if you take one blood lead level from one person at a particular point in time, you can’t tell really if that represents past exposure or only exposure that occurred very recently. Because the half-life of lead in blood is only about a month. So any one blood lead level assessment is not very good generally speaking in terms of determining how much lead they’ve been exposed to in the past.
GELLERMAN: So you feel there’s really a very close causal link between crime and lead?
DIETRICH: I am convinced that we’re seeing that in our own data and sometimes the data speak clearly and I think the data are speaking clearly to us that there is a causal link between early exposure to lead, juvenile delinquency, and crime.
GELLERMAN: Well Professor, thank you very much. I appreciate it.
DIETRICH: You’re very welcome.
GELLERMAN: Kim Dietrich is a professor of environmental health at the University of Cincinnati College of Medicine.
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