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« Follow-up on Gerberding's Testimony | Main | Valerie Plame Wilson , Postpartum Depression »

Element 82 and Violence: Evidence for Benefit from Pollution Control

Category: EnvironmentNeurosciencePublic Health
Posted on: October 26, 2007 7:15 AM, by Joseph j7uy5

The Clean Air Act was passed in 1970, and amended in 1977 and 1990.  It has been mildly controversial, but most people supported it then and support it now.  

A retrospective economic analysis done in the early 1990's indicated that the cost of implementation from 1970 to 1990 had been about $523 billion in 1990 dollars.  What did we get for that money?  The same study indicated that the economic benefit had been somewhere between $5.6 to $49.4 trillion, with a mean (among various scenarios) of $22.2 trillion.  Allowing for various uncertainties, it was estimated that the benefit/cost ratio was between 10.7 to 94.5.  That is, each dollar spent resulted in an economic gain of 10 to 94 dollars.  

Not many investments pay off that well.

In addition, the report indicated that the benefit calculations did not include air toxics-related human health effects.


contains_lead.jpg
photo credit: Cindy; Creative Commons license.

One of the important substances that was regulated was the chemical element, lead (element 82).  Lead is very poisonous.  

Indeed, has been noted that there is evidence that lead poisoning is related to the incidence of violent crime.


In a 1996 Pitt study of 301 children, those with the highest concentrations of lead - still below government-recommended safe levels - had tests scores showing more aggression, attentional disorders and delinquency. In 2002, those findings were extended to show that the average bone lead levels in 190 adjudicated delinquents was higher than normal controls. The results indicated that between 18 and 38 percent of all delinquency in Pennsylvania's Allegheny County, which includes Pittsburgh, could be due to lead. Additionally, a number of recent studies have shown a strong relationship between sales of leaded gasoline and rates of violent crime.

Now, that relationship has been explored further, with confirmatory results.  As reported in the New York Times Magazine:

Criminal Element
By JASCHA HOFFMAN
Published: October 21, 2007

Has the Clean Air Act done more to fight crime than any other policy in American history? That is the claim of a new environmental theory of criminal behavior.

In the early 1990s, a surge in the number of teenagers threatened a crime wave of unprecedented proportions. But to the surprise of some experts, crime fell steadily instead. Many explanations have been offered in hindsight, including economic growth, the expansion of police forces, the rise of prison populations and the end of the crack epidemic. But no one knows exactly why crime declined so steeply.

The answer, according to Jessica Wolpaw Reyes, an economist at Amherst College, lies in the cleanup of a toxic chemical that affected nearly everyone in the United States for most of the last century.

Dr. Reyes' work was published in The B.E. [Berkley Electronic] Journal of Economic Analysis & Policy (link, $ for full access.)

Environmental Policy as Social Policy? The Impact of Childhood Lead Exposure on Crime
Jessica Wolpaw Reyes

Childhood lead exposure can lead to psychological traits that are strongly associated with aggressive and criminal behavior. In the late 1970s in the United States, lead was removed from gasoline under the Clean Air Act. I use the state-specific reductions in lead exposure that resulted from this removal to identify the effect of childhood lead exposure on crime rates. The elasticity of violent crime with respect to childhood lead exposure is estimated to be 0.8, and this result is robust to numerous sensitivity tests. Mixed evidence supports an effect of lead exposure on murder rates, and little evidence indicates an effect of lead on property crime. Overall, I find that the reduction in childhood lead exposure in the late 1970s and early 1980s was responsible for significant declines in violent crime in the 1990s and may cause further declines in the future. Moreover, the social value of the reductions in violent crime far exceeds the cost of the removal of lead from gasoline.


Jessica Wolpaw Reyes is not a physician or a toxicologist, but she is good at math.  Her study is based upon a detailed analysis of correlations.  This, in itself, does not prove causation.  However, in combination with the other work on the subject, it is highly suggestive.  From the NYTM article:

No matter how suggestive the economists' data, it takes a doctor to show that some of the people most damaged by lead are out there breaking the law. Herbert Needleman, the University of Pittsburgh psychiatrist and pediatrician whose work helped persuade the government to ban lead in the 1970s, recently studied a sample of juvenile delinquents in Pittsburgh; the group had significantly more lead in their bones than their peers. And lead may not be the only source of damage. The National Children's Study will soon begin to track more than 100,000 children to determine the effects of exposure to common pesticides, among other chemicals.

has been one of the most influential investigators pursuing this line of inquiry.

Naturally, there are skeptics, such as Professor Jeffrey Miron, Senior Lecturer on Economics at Harvard University.  As noted by NYTM:

The magnitude of these claims has been met with a fair amount of skepticism. Jeffrey Miron, a Harvard economist, wonders how lead could have had such a strong effect on violent crime while, according to Reyes, it showed almost no effect on property crimes like theft. He also doubts that the hypothesis could explain the plunge in the U.S. murder rate from the 1930s through the 1950s. "I certainly think it's a reasonable exercise," Miron says. "We just have to be appropriately suspicious of how much you can actually show."

Miron can wonder how lead could affect one type of crime, but not another.  However, from a neuropsychiatric standpoint, it is entirely plausible; it is common to lose inhibitions of one type,but not another.  So much so, that this does not seem like a reasonable point of objection.  The drop in the murder rate I cannot explain, but perhaps the end of Prohibition, or the end of the Great Depression, had something to do with it.  The bigger problem has to do with our inability to perform controlled, prospective experiments in an effort to prove causality.  

In order to prove a causal link, we would need to randomize people, then intentionally expose some of them to lead.  Can't do that, obviously.  This raises a potential problem for policymakers.  In order to get proof, we would have to do a study that would be unethical to do.  Even so, policymakers have to make decisions, even if the data they would like to have is not, and can not be, available.

The urgency of this is lessened somewhat by the fact that no sensible person would ever propose loosening the restrictions on lead pollution.

Well, actually,
in 2006, the Administration wanted to relax the regulation of lead emissions, "given the significantly changed circumstances since lead was listed in 1976."  No.  Nothing has changed.  Lead is still a potent neurotoxin, and it still would be incredibly stupid to spew it into the atmosphere.

In civil (ie. not criminal) matters, one does not need absolute proof in order to take action.  It is sufficient merely to have the preponderance of evidence.   Cripes, even Dick Cheney would take action on a 1% probability.  The probability of a causal association between lead poisoning and violent crime is a lot higher than 1%.  Cheney should be all over this one.


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