The Clean Air Act was passed in 1970, and amended in 1977
It has been mildly controversial, but most people supported
it then and support it now.
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.
One of the important substances that
regulated was the chemical element, href="http://en.wikipedia.org/wiki/Lead">lead
(element 82). href="http://www.med.umich.edu/1libr/yourchild/leadpois.htm">Lead
is very poisonous.
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:
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
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.
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.
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.
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
of lead emissions, “given the significantly changed
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.