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May 20, 2014

More useful discussion of the (under-discussed) lead-crime-rate connections

A helpful reader alerted me to this helpful and lengthy new article at the Juvenile Justice Information Exchange headlined "Is Lead Exposure the Secret to the Rapid Rise and Fantastic Fall of the Juvenile Crime Rate?".  Here are excerpts from a piece worthy of a full read (and with lots of helpful links to the research discussed):

For the juvenile justice field, there is no larger question. It’s the elephant in the room, the great mystery, the trend that has changed everything — and seemingly without explanation. Why have juvenile crime rates, once predicted to rise inexorably, instead been falling for two decades? Falling... and falling... and falling.

What if the answer was readily available? What if it mostly boiled down to a single element, hiding in plain sight, and we just refused to notice? Well, compelling evidence suggests that much or most of the fluctuation in juvenile crime rates does boil down to a single element — a chemical element.

The element is lead, and a powerful body of research indicates that the recent declines in juvenile offending rates, like the rise in juvenile crime rates that preceded them, stem in large part from changes in children’s exposure to lead paint and exhaust from leaded gasoline. The idea may sound crazy, “like a bad science fiction plot,” quips Rick Nevin, one of the leading researchers documenting the link between lead exposure and crime. But the data don’t lie and here’s what they say.

For centuries it has been clear that lead is a potent poison. At extreme concentrations, lead poisoning causes anemia, blindness, renal failure, convulsions, abdominal spasms, insomnia, hallucinations, chronic fatigue and, ultimately, death. But only in the past four decades have researchers learned that lead exposure can severely damage the cognitive development of children, even at modest levels that produce no physical symptoms. And only through modern scanning technology have we learned that the lead molecule is perfectly designed to cripple young minds in ways that not only lower IQ, but also damage the very parts of the brain that oversee aggression, self-regulation, attention and impulse control.

As Kim Cecil, director of epidemiology and biostatistics at the University of Cincinnati College of Medicine, recently explained to the Chemical & Engineering News, “These are the parts of the brain that say, ‘Ooh, I’ve learned from before that I shouldn’t steal that, or if I do this, then the consequences are that.’” Even moderate levels of lead in the bloodstream of an infant or toddler significantly increase the odds that he will suffer behavioral disorders in childhood, and will engage in delinquency and criminal behavior later on. (Lead seems to affect boys more than girls.) A study published in 2008 tracked 250 children born in low-income Cincinnati neighborhoods between 1979 and 2004. It found that children with elevated levels of lead exposure (either in utero, or in early childhood) were significantly more likely to be arrested for both violent and nonviolent crimes than children with lower lead exposure. Earlier studies in Philadelphia and Pittsburgh also found a significant correlation between early childhood lead exposure and later conduct problems....

[T]he strength and consistency of the findings linking lead exposure and crime trends, plus the wealth of corroborating evidence from other disciplines (such as brain imaging studies and longitudinal studies of small population samples in selected cities) creates what Kevin Drum, a widely-cited blogger and journalist who has written extensively on the lead-crime connection, calls “an astonishing body of evidence.”...

“We now have studies at the international level, the national level, the state level, the city level, and even the individual level,” writes Drum. “Groups of children have been followed from the womb to adulthood, and higher childhood blood lead levels are consistently associated with higher adult arrest rates for violent crimes. All of these studies tell the same story: Gasoline lead is responsible for a good share of the rise and fall of violent crime over the past half century.”

By this point, readers of this column may be wondering: If the evidence linking lead exposure and crime is so strong, why haven’t we heard more about it? The primary reason is that the research has been largely ignored by academics. In 2008, a 250-page report on U.S. crime trends by the National Academies of Science included only one paragraph about lead exposure, drawing no conclusions. Late last year, a National Academies roundtable on crime trends did hold a session on lead exposure.

But even in that day’s session, the opening presentation — delivered by the renowned British criminologist, David Farrington — did not include a word about lead exposure. His talk on “Individual Differences in Antisocial Behavior, Delinquency, and Crime” discussed unemployment, parenting, poverty, family size, peer influences, substance abuse, and even an individual’s resting heart rate — none of which has seen changes in recent times consistent with the larger rise and fall in crime rates. Farrington said nothing about the introduction and subsequent removal of massive amounts of a toxic substance with a powerful known link to subsequent delinquency and criminality.

Drum suggests that the lack of attention to lead exposure is natural, given that the theory is new and unproven. Indeed, some critics have raised legitimate questions about the research — citing the small number of studies, questioning methodology and suggesting that other factors beyond lead (such as demographics, shifting drug markets and more) may also play an important role in determining crime rates over time....

Another factor behind the inattention to the lead exposure research is that most of the studies thus far have been conducted by economists and public health scholars, not criminologists, and the key papers have been published in environmental journals rather than criminology publications. Nevin also sees an element of self-interest: “Everyone has their own theory that they hold dear about why the crime decline has occurred,” he says. “There are a whole lot of people ... on both sides of the political spectrum who want to claim credit for this and don’t really like hearing about this unrelated powerful force.”...

[T]he lead data suggest that perhaps the most important thing our nation can do to reduce juvenile crime — and also to boost youth success in general — has nothing to do with juvenile courts or corrections systems. Maybe our first priority should be lead abatement — finishing the job by removing the last remnants of our tragic 20th century fetish with this terrible toxin.

 Some recent related posts:

May 20, 2014 at 12:34 PM | Permalink


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I think internet porn and video games such as Xbox and Playstation have had a big role in keeping boys at home and out of trouble for at least the last fifteen years.

Posted by: Jardinero1 | May 20, 2014 1:07:36 PM

We had Atari and Colecovision in the 1980s, though I am sure factors other than lead are parts of the story, too.

Posted by: Doug B. | May 20, 2014 3:33:10 PM

I remember those games and how briefly they held my interest. Today's games are much more immersive and interesting. Video gaming is also much more part of the culture and a means for youth to interact. I do a carpool for my kids various sports teams. I am struck by how many of them spend the weekend and nights, together, playing video games. The thing is, they are together only virtually. They never leave their own houses. This isn't unique to boys. Many girls game together virtually. Anyway, one boy or girl wired in at home is one less boy or girl on the street making trouble.

Posted by: Jardinero1 | May 20, 2014 4:53:25 PM

The bigger the phenomenon, the more factors likely influence it. While I have tried to rbut the lead theory with the far more potent bastardy theory, I can see lead a sa factor among many. Obesity. Too fat to commit street crime. Video addiction as mentioned above. The wealth of the poor who are too lazy to make a small score. Marijuana use. Less alcohol use. More immigrants (lower crime rates to dilute our little savages). The feminization of boys by feminist indoctrination in our schools.

So there is nothing wrong with including lead levels on the list. It is only when it is touted as a single factor or as a predominant factor that I object.


Aside from all that, what do the dropping rates of crime, and the multifoctorial explanations say about the correctness of the view of young criminals by the Supreme Court? I thought they were supposed to be impetuous, immature, unable to control themselves, rather than increasingly law abiding.

Posted by: Supremacy Claus | May 20, 2014 7:03:19 PM

SC - My 2000 study found that unwed teen pregnancy rates have also followed the rise and fall of lead exposure, and my 2007 study included the following observation related to your comment:

"The juvenile arrest rate soared in the 1960s, tracking the surge in gas lead after World War II, despite a large 1960s decline in the percent of children in poverty. That rise in juvenile offending coincided with a 1960s rise in the unwed teen birth rate, and the 1990s decline in juvenile arrests coincided with a falling unwed teen birth rate. Higher offending due to single parents would be consistent with juvenile offending that lagged the unwed birth trend by 12–17 years, as children raised by single mothers became teenagers. The coincident rise and fall of unwed birth rates and juvenile offending is inconsistent with the time-precedence indicator of causation. Nevin (2000) showed age-specific unwed pregnancy rates track USA gas lead trends with time lags consistent with mother’s age and lead exposure in the first year of life. Cross-sectional studies that link criminal offending to single parents could reflect separate effects of preschool lead exposure on different types of impulsive behavior, across family generations.

Social trends cannot explain why the 1990s homicide decline was so pronounced among juvenile offenders, and especially black juveniles, but blood lead trends can. Blood lead prevalence over 30 mcg/dl among white USA children fell from 2% in 1976–1980 to less than 0.5% in 1988–1991, as prevalence over 30 mg/dL among black children plummeted from 12% to below 1%. The white juvenile murder arrest rate then fell from 6.4 to 2.1 from 1993–2003, as the black juvenile rate fell from 58.6 to 9.7. That 83% fall in the black juvenile murder arrest rate occurred with just 36% of black children living in two-parent families in 1993, and in 2003."

Posted by: Rick Nevin | May 20, 2014 10:27:50 PM

Rick: Leave aside foreign low crime rates in high lead level countries, but low bastardy rates (e.g. as China increases its lawyer supply, its crime rate is shooting up). Your correlations are quite robust for the US. Your point is further supported by longitudinal studies of individual birth cohorts in national health surveys. In a simple declarative sentence, can you quantify the strength of the effect. Drops in blood lead levels explain ____% of the drop in crime rates.

Competing with the drop in lead level? Mass incarceration, and the resulting reduction of the fecundity of prisoners, producing fewer offspring because of incarceration. The number of children of high crime risk population also fell during this time. Their potential fathers were in prison. While the pro-life movement gets agitated about white abortions, and they dropped, no one cares about black abortions, and they increased.

This longitudinal study supports Rick's argument. Although by, again, an economist, it employs health survey longitudinal data.

Amherst College and NBER
It is well known that exposure to lead has numerous adverse effects on
behavior and development. Using data on two cohorts of children from
the NLSY, this paper investigates the effect of early childhood lead
exposure on behavior problems from childhood through early adulthood.
I find large negative consequences of early childhood lead exposure, in
the form of an unfolding series of adverse behavioral outcomes: behavior
problems as a child, pregnancy and aggression as a teen, and criminal
behavior as a young adult. At the levels of lead that were the norm in
United States until the late 1980s, estimated elasticities of these
behaviors with respect to lead range between 0.2 and 1.0.

(Once again, this effect shows the lesser impact of the criminal law when compared to technological progress. The $trillion taken by the lawyer profession and its constituencies should be transferred to science and technology, in, yea, industrial planning policy.)

Posted by: Supremacy Claus | May 21, 2014 6:10:18 AM

My best guess is that declines in lead exposure explain at least 90% of the crime decline since the early-1990s, and maybe all of it. With respect to the amazing 83% decline in the black juvenile homicide arrest rate from 1993 to 2003, there is no reason to think that any of that decline was due to family structure because the percent of black children living in two-parent families was the same in 1993 and 2003. None of that decline is explained by race, whether due to abortions by race or some other racial theory, because we are comparing murder arrest rates for black juveniles in both 1993 and in 2003. Non of the ongoing declines in juvenile and young adult arrest rates can be explained by incarceration trends because incarceration rates have fallen by 50% or more for juveniles and ages 18-19 over the past decade.

Posted by: Rick Nevin | May 21, 2014 1:42:13 PM

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