Over the weekend, the Washington Post published an article suggesting that much of the decline in crime in the 1990s may have been due to the reduction of childhood lead exposure after the removal of lead from gasoline and house paint.
This is an intriguing hypothesis. There is evidence on an individual level that high exposure to lead is harmful to both IQ and the ability to delay gratification, two traits that could enhance the attractiveness of crime. There is also some suggestive time-series evidence of a relationship: the rise and fall in lead exposure at the national level match the rise and fall in crime. Still, although both Post reporter Shankar Vendantam and the cited economist, Rick Nevin (whom I’d never heard of), appear quite convinced by the time-series data, I am not. When you have a variable like crime that goes up for a long time then goes down for a long time, it is easy to find other variables that share that pattern and appear to have a causal impact, even though the relationship is completely spurious.
About seven years ago, Michael Greenstone and I tried to look into this same issue using airborne lead measures at the local level, as well as other approaches. We ultimately gave up without finding anything. That largely soured me on the lead/crime link.
Recently, however, Jessica Wolpaw Reyes at Amherst has put together what appears to me to be the most persuasive evidence to date in favor of a relationship between lead and crime. Rather than looking at a national time-series, she tries to exploit differences in the rates at which lead was removed from gasoline across states. I haven’t read her paper with the care that a referee would at an academic journal; but, at least superficially, what she is doing looks pretty sensible. She finds that lead has big effects (and, for what it’s worth, she also confirms that, when controlling for lead, the link between abortion and crime is as strong or stronger as in our initial study, which did not control for lead.)
Roger Masters, a professor at Dartmouth, has also been doing interesting research on this subject, although I am also not very familiar with his work.
It will be very interesting to see how this research agenda plays out. If it can be shown here and in other areas that environmental factors have powerful and long-lasting impacts on human behavior, it may dramatically change the way we think about public policy.
15 Comments
Interesting post.
I think it begs the question of what can be done about the effects of lead exposure. Can those who grew up around lead paint, as I did, do anything to overcome its effects (such as the delayed gratification problem, which I have in spades).
— BruceKeenerit would be intriguing to see if there’s a ‘lead map’ for housing in the UK.
Certainly the house I grew up in was public-owned housing, and there was a great effort to strip out the lead in the house, but friends in houses from the same era weren’t so lucky.
I’m especially curious about whether toxic chemicals that are released by flooding will have long-term effects on crime rates.
— angelofthenorthIs there existing scientific evidence that lead in gasoline somehow works its way into children?
— 110philOnly if they inhale.
— egretmanNew York has among the worst lead paint problem of any large city on account of its older housing stock. Yet it’s also had among the biggest declines in crime rates.
— prosaI’m with 110phil- why not simply correlate blood levels of lead and criminal behavior?
— frankendufNow that crime rates are moving back up, should we infer that lead is getting back into the food chain (or air supply)? Or perhaps there are other reasons more in line with what used to be the conventional wisdom?
— pparkmanLead in the plumbing has been cited as a probable cause of the decline and fall of Rome.
Maybe somebody should do a study on those kids who bought the Thomas the Tank Engine toys (made in China with lead paint).
— suntzusjbVery interesting post.
What about birth control pills in the common water supply?
It would be very ironic if some women spend time and energy to reduce hormones in cattle and other farm animals, but then choose a birth control method for themselves that pollutes our environment just as much.
— kahprosa, a main point in the linked article is that the crime decline in NY followed a previous reduction in lead paint.
Sure, not all the lead was removed during that lead reduction. Sure, as a result NY still has a bad lead problem. But hey, there’s still a little crime in NY now and then, too.
— kahMaybe unleaded paint is causing a rise in autism, too.
Or the cause could be the decline in mothers smoking during pregnancy.
Really, though, I think the answer is the microwave oven.
— steveslivafrankenduf: I think that elevated lead levels in the bloodstream permanently cause the IQ problems. However, after exposure is reduced, the blood concentrations fall. Thus, if lead causes an increased propensity for crime, criminals may test at low levels if they are no longer in the high lead environment.
— liberalartsTo pparkman, too many confounding factors exist for one to make a claim that a rise in crime is a reaction to a rise in lead…If we could hold for all other confounding factors, this argument could get much more interesting…
— keeprollin41Counter Factor? Has there been an assessment on the effects of selective breeding (sperm banks and egg donation) on IQ? The impact should be visible as rising national IQs, above the standard distribution beginning around 140. Nothing to do with lead, but maybe we will have smarter criminals.
— billpgI guess there are a couple things to consider, the first being that most urban places that still contain high levels of lead are in poor areas which would automatically drive crime levels up
second, that you have to distinguish between petty crime, white collar, violent …. etc. Most crime happens when the criminal is between 15-25ish, although not sure about white collar crime.
lead exposure at a young age - can cause permanent damage to the nervous system, whether or not lead levels are present in blood later in life… Part of the affects of lead exposure can decrease your ability to make decisions or correct judgements, soooo….. I would be interested in finding out if there is correlation in crime & lead and how someone reacts to a situation… Do they understand crime can have penalties and to what extent? Do they react in a violent or aggressive manner if things don’t go their way? Can lead exposure decrease the amount of time or level of “bull***t” they can handle…which makes them “snap” and commit a violent crime?
also… dont forget about all of the other toxins in the environment…what is their contribution, and can there be multiple attributes to increased violent behavior?
— Susi Rankis