Did removing lead from petrol spark a decline in crime?

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Many Western nations have experienced significant declines in crime in recent decades, but could the removal of lead from petrol explain that?

Working away in his laboratory in 1921, Thomas Midgley wanted to fuel a brighter tomorrow. He created tetraethyl lead – a compound that would make car engines more efficient than ever.

But did the lead that we added to our petrol do something so much worse? Was it the cause of a decades-long crime wave that is only now abating as the poisonous element is removed from our environment?

For most of the 20th Century crime rose and rose and rose. Every time a new home secretary took office in the UK – or their equivalents in justice and interior ministries elsewhere – officials would show them graphs and mumble apologetically that there was nothing they could do to stop crime rising.

Then, about 20 years ago, the trend reversed – and all the broad measures of key crimes have been falling ever since.

Offending has fallen in nations whose governments have implemented completely different policies to their neighbours.

If your nation locks up more criminals than the average, crime has fallen. If it locks up fewer… crime has fallen. Nobody seems to know for sure why.

But there are some people that believe the removal of lead from petrol was a key factor.

Lead can be absorbed into bones, teeth and blood. It causes kidney damage, inhibits body growth, causes abdominal pain, anaemia and can damage the nervous system. More than a century ago, a royal commission recommended to British ministers that women shouldn't work in lead-related industry because of damage to their reproductive organs.

By the 1970s, studies showed that children could even be poisoned by chewing fingernails harbouring tiny flecks of old leaded paint from their homes and schools.

Studies have shown that exposure to lead during pregnancy reduces the head circumference of infants. In children and adults, it causes headaches, inhibits IQ and can lead to aggressive or dysfunctional behaviour.

If you want to understand the causes of crime – and be tough on them – you need to start with lead, says Dr Bernard Gesch, a physiologist at Oxford University who has studied the effect of diet and other environmental factors on criminals.

"Lead is a very potent neurotoxin," says Gesch. "It has a range of effects on the brain that have been demonstrated through hundreds of different biological studies. Lead alters the formation of the brain. It reduces the grey matter in areas responsible for things such as impulse control and executive functioning – meaning thinking and planning."

In other words – lead poisoning leads to bad decisions. The lead theorists say the poison has a time-lag effect which could not be understood until recently.

In the early 1990s, economist and housing consultant Rick Nevin was pondering whether it would be worth the US spending vast sums cleaning leaded paint out of old housing in American cities. By then, everyone knew that lead did bad stuff to the brain and took years to leave the body.

And that got Nevin thinking. Would the accumulation of lead over time play a role in behaviour that would ultimately become criminal? Nevin calculated the rise and fall of the presence of lead from petrol and he compared that curve to the modern history of violent crime. What he came up with was rather startling.

When the amount of lead in the environment increased, Nevin showed a corresponding rise in violent crime two decades later. And when the amount of lead in the environment fell, violent crime also tracked down – again about 20 years later.

Was this a one-off, freak statistical result? Where was the proof that lead had actually caused crime?

Fourteen years ago, Prof Jessica Wolpaw-Reyes, an economist at Amherst College Massachusetts, was pregnant and doing what many expectant mothers do – learning about the risks to her unborn child's health. She started to read up on lead in the environment and, like Nevin before her, began pondering its link to crime.

"Everyone was trying to understand why crime was going down," she recalls. "So I wanted to test if there was a causal link between lead and violent crime and the way I did that was to look at the removal of leaded petrol from US states in the 1970s, to see if that could be linked to patterns of crime reduction in the 1990s."

Wolpaw-Reyes gathered lead data from each state, including figures for gasoline sales. She plotted the crime rates in each area and then used common statistical techniques to exclude other factors that could cause crime. Her results backed the lead-crime hypothesis.

"There is a substantial causal relationship," she says. "I can see it in the state-to-state variations. States that experienced particularly early or particularly sharp declines in lead experienced particularly early or particularly sharp declines in violent crime 20 years later."

She says her research also established different levels of crime in states with high and low lead rates.

Nevin's original research pointed to lead poisoning in childhood increasing the likelihood of offending by the time someone had reached their teens or early twenties. Wolpaw-Reyes' data appeared to show that anti-pollution legislation in the US then reversed that trend on a state-by-state basis.

Written By: Dominic Casciani
continue to source article at bbc.com

34 COMMENTS

  1. Did a decline in pirates cause global warming?

    BTW if you read Freakonomics, the author lays out a causal relationship with the 1990′s drop in crime and the Roe v. Wade case which was adjudicated in 1973. (I know, idiosynchratic to the US…)

    His data points to the cohort of aborted children NOT turning 21 in 1994 being absent from the crime stats and attributes the sharp decline to the court case.

    • In reply to #1 by crookedshoes:

      Did a decline in pirates cause global warming?

      BTW if you read Freakonomics, the author lays out a causal relationship with the 1990′s drop in crime and the Roe v. Wade case which was adjudicated in 1973. (I know, idiosynchratic to the US…)

      His data points to the cohort of aborted children NOT…

      Regarding Freakonomics, from Pinker:

      To begin with, the freakonomics theory assumes that women were just as likely to have conceived unwanted children before and after 1973, and that the only difference was whether the children were born. But once abortion was legalized, couples may have treated it as a backup method of birth control and may have engaged in more unprotected sex. If the women conceived more unwanted children in the first place, the option of aborting more of them could leave the proportion of unwanted children the same. In fact, the proportion of unwanted children could even have increased if women were emboldened by the abortion option to have more unprotected sex in the heat of the moment, but then procrastinated or had second thoughts once they were pregnant.

      That may help explain why in the years since 1973 the proportion of children born to women in the most vulnerable categories—poor, single, teenage, and African American—did not decrease, as the freakonomics theory would predict. It increased, and by a lot.150 What about differences among individual women within a crime-prone population? Here the freakonomics theory would seem to get things backwards. Among women who are accidentally pregnant and unprepared to raise a child, the ones who terminate their pregnancies are likely to be forward-thinking, realistic, and disciplined, whereas the ones who carry the child to term are more likely to be fatalistic, disorganized, or immaturely focused on the thought of a cute baby rather than an unruly adolescent. Several studies have borne this out.

      Young pregnant women who opt for abortions get better grades, are less likely to be on welfare, and are more likely to finish school than their counterparts who have miscarriages or carry their pregnancies to term. The availability of abortion thus may have led to a generation that is more prone to crime because it weeded out just the children who, whether through genes or environment, were most likely to exercise maturity and self-control.

      Also, the freakonomists’ theory about the psychological causes of crime comes right out of “Gee, Officer Krupke,” when a gang member says of his parents, “They didn’t wanna have me, but somehow I was had. Leapin’ lizards! That’s why I’m so bad!” And it is about as plausible. Though unwanted children may grow up to commit more crimes, it is more likely that women in crime-prone environments have more unwanted children than that unwantedness causes criminal behavior directly. In studies that pit the effects of parenting against the effects of the children’s peer environment, holding genes constant, the peer environment almost always wins.152 Finally, if easy abortion after 1973 sculpted a more crime-averse generation, the crime decline should have begun with the youngest group and then crept up the age brackets as they got older. The sixteen-year-olds of 1993, for example (who were born in 1977, when abortions were in full swing), should have committed fewer crimes than the sixteen-year-olds of 1983 (who were born in 1967, when abortion was illegal). By similar logic, the twenty-two-year-olds of 1993 should have remained violent, because they were born in pre-Roe 1971. Only in the late 1990s, when the first post-Roe generation reached their twenties, should the twenty-something age bracket have become less violent. In fact, the opposite happened. When the first post-Roe generation came of age in the late 1980s and early 1990s, they did not tug the homicide statistics downward; they indulged in an unprecedented spree of mayhem. The crime decline began when the older cohorts, born well before Roe, laid down their guns and knives, and from them the lower homicide rates trickled down the age scale.153

      Pinker, Steven (2011-10-04). The Better Angels of Our Nature: Why Violence Has Declined (p. 121). Penguin Group. Kindle Edition.

      • In reply to #5 by Red Dog:

        . . Among women who are accidentally pregnant and unprepared to raise a child, the ones who terminate their pregnancies are likely to be forward-thinking, realistic, and disciplined, whereas the ones who carry the child to term are more likely to be fatalistic, disorganized, or immaturely focused on the thought of a cute baby rather than an unruly adolescent. Several studies have borne this out.

        I had a suspicion that the conclusions drawn in “Freakonomics” may not be correct though I couldn’t call to mind the Pinker quote. It looks as if lead removal could take a higher place on the list of possible causes of a reduction in crime.

        Getting people to accept the fact that crime has lessened over the last couple of decades is a big hurdle as well. Statistics are showing us that this is the case but the public perception is one of ever increasing crime. I like to blame the popular media for this misconception.

      • Red Dog,
        Cool stuff from Pinker. I want you to know that I was not citing the freakonomics conclusion because i necessarily agree with it, but rather using it to illustrate (along with the pirates and global warming) that many many conclusions can come from data and correlation and causation are sometimes a far far cry from one another…. I guess I was firing off the thought before it gelled, but my theme (restated) would be that “there is a tremendous amount of noise in this data set”.

        I also tried (perhaps poorly) to include that global crime is the theme in the lead data and Roe v. Wade (of course) only would pertain to the US.

        Anyway, I like what Pinker contributes to the conversation, and I like that you are well read enough to proffer it in this conversation!

        In reply to #5 by Red Dog:

        In reply to #1 by crookedshoes:

        Did a decline in pirates cause global warming?

        BTW if you read Freakonomics, the author lays out a causal relationship with the 1990′s drop in crime and the Roe v. Wade case which was adjudicated in 1973. (I know, idiosynchratic to the US…)

        His data points to th…

        • In reply to #10 by crookedshoes:

          I also tried (perhaps poorly) to include that global crime is the theme in the lead data and Roe v. Wade (of course) only would pertain to the US.

          Generally, judicial attitudes to abortion changed in Australia around the same time, so you could tip us in to that too.

        • In reply to #10 by crookedshoes:

          Red Dog,
          Cool stuff from Pinker. I want you to know that I was not citing the freakonomics conclusion because i necessarily agree with it, but rather using it to illustrate (along with the pirates and global warming) that many many conclusions can come from data and correlation and causation are so…

          Yeah Red Dog got there first but I would say Pinkers book is the best I have read on this subject given how thorough he is with discussing all reasons for declines in violence.
          The data points to a long term historical decline in violence that has been going on for millennia. The general trend is downward but it can rise for a while and then continue the downwards trajectory. That seems to be the case with violence rising in the west from the sixties to the nineties and then declining again.

    • In reply to #1 by crookedshoes:

      Did a decline in pirates cause global warming?

      BTW if you read Freakonomics, the author lays out a causal relationship with the 1990′s drop in crime and the Roe v. Wade case which was adjudicated in 1973. (I know, idiosynchratic to the US…)

      His data points to the cohort of aborted children NOT turning 21…

      This Freakonomic claim about legalized abortion leading to a drop in crime was a fun read and good television but has been widely debunked. The number of children born to women in vulnerable categories (poor, single, etc) actually greatly increased after the 1973 abortion decision so the figures do not stack up. (google page 119 of Steven Pinker’s “Better Angels of our Nature” for details). But one bad theory does not mean all theories are bad and this lead based theory is yet to be disproved. One hole in this theory might be Japan which did not have a crime surge linked to lead in petrol and this would have to be explained to keep this Lead->Crime theory alive.

      • I know. That was the point of my post. I was trying (badly) to insinuate just how much noise there is in this data. I posted (in # 10) an epilogue to my initial post that tried (unsuccessfully?) to explain.

        ANyway, thanks for raising it to my attention and opening dialogue, data sets like these are extraordinarily “malleable” and most conclusions that researcher reach seem to be the ones they were trying to reach before the data set was analyzed. In short, GIGO.

        In reply to #28 by Catfish:

        In reply to #1 by crookedshoes:

        Did a decline in pirates cause global warming?

        BTW if you read Freakonomics, the author lays out a causal relationship with the 1990′s drop in crime and the Roe v. Wade case which was adjudicated in 1973. (I know, idiosynchratic to the US…)

        His data points to th…

  2. This is the kind of correlation for which it is nearly impossible to objectively establish a genuine causal relation. So many things are correlated but have nothing to do with one another. Following that line of reasoning, one could correlate the rising diversity of types and brands of chocolate treats in food markets with the rise of autism in developed nations.

    It’s like that “wheat causes obesity” theory by that quack Dr. William Davis. The same way obesity cannot be ascribed to a single cause, there are many factors involved in criminality: poverty, education, social adaptation, etc… The idea of linking crime to one single cause, this “magic bullet” concept to such a complex, multi-faceted problem is ludicrous IMO.

    • In reply to #2 by NearlyNakedApe:

      but there is a strong correlation on a state by state basis each with similar time-based trending. that is indeed strong evidence worthy of deep consideration

      This is the kind of correlation for which it is nearly impossible to objectively establish a genuine causal relation. So many things are correlated but have nothing to do with one another. Following that line of reasoning, one could correlate the rising diversity of types and brands of chocolate tre…

    • In reply to #2 by NearlyNakedApe:

      This is the kind of correlation for which it is nearly impossible to objectively establish a genuine causal relation.

      Well, yes. But, that is actually true for practically all correlations within societies. You can never control all variables as one can in a laboratory.

    • In reply to #2 by NearlyNakedApe:

      This is the kind of correlation for which it is nearly impossible to objectively establish a genuine causal relation. So many things are correlated but have nothing to do with one another. Following that line of reasoning, one could correlate the rising diversity of types and brands of chocolate tre…

      Your ‘wheat causes obesity’ quack story made me wonder if we could just as easily ascribe the drop in crime to the rise in obesity. Criminals may simply be too fat to chase victims, fit in through doors, get into cars they have jacked etc. But I fear the police and their donut diets may well cancel out that effect (or possibly not now I think of it, police obesity will make it harder for them to catch criminals, and possibly too lazy to fill in forms, thus reducing reported crime. There could be something to this after all.

    • In reply to #2 by NearlyNakedApe:

      This is the kind of correlation for which it is nearly impossible to objectively establish a genuine causal relation. So many things are correlated but have nothing to do with one another. Following that line of reasoning, one could correlate the rising diversity of types and brands of chocolate tre…

      http://i.imgur.com/MNpBhvg.jpg

      That is a graph of Chicago murders per 100,000 people, 1870 to the present. Notice how murders begin trending upward in 1943, peaked and then began trending back down in 1996. If we buy the 20 year latency period of increased violent crime as a result of increased environmental lead, the murder rate pretty closely tracks the rise and fall of leaded gasoline. Leaded gasoline came about in the 1920s, the dangers of which were highly publicized in the 1970s, was banned for sale in the 1980s, but you could still use it on the road until the 1990s.

      Lead obviously isn’t going to explain all of it. But it is interesting.

  3. There is some evidence that lead poisoning helped to deaden the brains of the aristocracy and bring down the Roman Empire!

    http://corrosion-doctors.org/Elements-Toxic/Lead-history.htm

    For winemakers in the Roman Empire, nothing but lead would do. When boiling crushed grapes, Roman vintners insisted on using lead pots or lead-lined copper kettles. “For, in the boiling,” wrote Roman winemaker Columella, “brazen vessels throw off copper rust which has a disagreeable flavor.” Lead’s sweet overtones, by contrast, were thought to add complementary flavors to wine and to food as well. (reference) The metal enhanced one-fifth of the 450 recipes in the Roman Apician Cookbook, a collection of first through fifth century recipes attributed to gastrophiles associated with Apicius, the famous Roman gourmet. From the Middle Ages on, people put lead acetate or “sugar of lead” into wine and other foods to make them sweeter. Lead touched many areas of Roman life. It made up pipes and dishes, cosmetics and coins, and paints. Eventually, as a host of mysterious maladies became more common, some Romans began to suspect a connection between the metal and these illnesses. But the culture’s habits never changed, and some historians believe that many among the Roman aristocracy suffered from lead poisoning.

    Julius Caesar, for example, managed to father only one child, even though he enjoyed women as much as he enjoyed wine. His successor, Caesar Augustus, was reported to be completely sterile. Some scholars suggest that lead could have been the culprit for the condition of both men and a contributing factor to the fall of the Roman Empire.

    “Lead poisoning denial” in Roman culture?????

  4. Perhaps it just a spurious correlation, though I think it’s an interesting idea. When I think of the decline of the Roman Empire I’ll have an image of those lead-lined pots from now on.

    The film ” Freakonomics” was repeated on tv over Easter. I really liked the solution reached in that production as well. I liked to think of all those unborn miscreants being responsible for a lowering of crime rates across the globe.

    I hope the effects of leaded petrol are looked into over the next few years. It would be marvellous to discover that removing lead had an unplanned effect on human behaviour.

    • In reply to #4 by Nitya:

      I hope the effects of leaded petrol are looked into over the next few years. It would be marvellous to discover that removing lead had an unplanned effect on human behaviour.

      Couldn’t help but correct

      I hope the effects of leaded petrol are looked into over the next few years. It would be marvellous to discover that adding lead had an unplanned effect on human behaviour.

      • In reply to #25 by alaskansee:

        Couldn’t help but correct

        I hope the effects of leaded petrol are looked into over the next few years. It would be marvellous to discover that adding lead had an unplanned effect on human behaviour.

        I thought it did have a spectacular effect on numerous boy-racers and senile boy racers. (Some like Jeremy Clarkson still haven’t got over it!! ) ☺

  5. Perhaps an increase in marijuana sparked a decrease in crime…or more omnipotent CCTV cameras in the streets – but un leaded petrol ? Whatever….its hardly white leaded face paint ! Crime has moved covertly into the corporate backrooms of the merchant banking and finance sectors…..

    • In reply to #6 by Light Wave:

      Perhaps an increase in marijuana sparked a decrease in crime…or more omnipotent CCTV cameras in the streets – but un leaded petrol ? Whatever….its hardly white leaded face paint ! Crime has moved covertly into the corporate backrooms of the merchant banking and finance sectors…..

      Ha ha! Ain’t that the truth?

  6. This is what Pinker has said so far (from his twitter on his web site): sapinker An FAQ: Did removing lead from gasoline cause the great crime decline? My answer: Maybe somewhat, but maybe not.
    11 hours 24 min ago.
    sapinker An earlier & more skeptical view of the lead-crime hypothesis: “Lead Poisoning and the Great 1960s Freakout”:
    11 hours 23 min ago.

  7. Speaking as a teacher of teenagers, so an insider (but a biased insider), I’d like to add “medicated teenagers” to the list of noise in this data set.

    For the past x number of years, we’ve taken our “incorrigible” teens (especially boys), labelled them as ADD, ADHD (or my favorite) ODD, and medicated the hell out of them from age 6 (7?)…. If that doesn’t zombify you by your adult years, what does?

    Also, we’ve done this with absolutely ZERO study (at least initially) on the long term effects of children taking amphetamine (the typical chemical solution to these issues). But, what if, after 15 years of medication, you are “different”?

    BTW, ODD is oppositional defiance disorder (not making this up). A kid with this is quite a handful. Of course we used to just call it “bad parenting”, but now the kid gets a classification and entitlement to their poor behavior. I have taught several of these “students” and it is very trying.

  8. And how can we explain the rise of criminality in Latin America, notably in Brazil? We do not have leaded fuels since the early 90′s, in fact, we never had a “heavy petrol fueled society” on twentieth century for economical reasons (cars were and still are somewhat expensive to any citizen have their ride) and because we use ethanol as fuel too, since the Second Oil Shock.

    Using the same logic, we have exactly the opposite result than Europe and North America on the last two decades.

    • i would say due in significant part to brazil’s numerous favela ghettos filled with many hundreds of thousands of poor that stretch for as far as the eye can see.. i have seen wide open spaces of land completely covered with them and the violent crimes associated with them are famous

      In reply to #18 by giovani.milchareck:

      And how can we explain the rise of criminality in Latin America, notably in Brazil? We do not have leaded fuels since the early 90′s, in fact, we never had a “heavy petrol fueled society” on twentieth century for economical reasons (cars were and still are somewhat expensive to any citizen have thei…

  9. When I first saw this article I had the same knee jerk reaction as most others have here. Clearly they are misusing statistics in order to find the correlation they want to see. Correlation is not the same as causality, in other words. I have not read the original study so I can’t say how scientific it is, but one part of the article really got my intention. She claims that you can observe this correlation between different states. This is really interesting. Of course there might be a range of underlying variables, but it sort of makes this claim at least a little more probable. An alarm bell though, is that the female researcher does not seem very interested in investigating alternative explanations. Serious scientists usually go to great lengths to point out possible alternative explanations and the limits of their studies.

    • In reply to #22 by Nunbeliever:

      When I first saw this article I had the same knee jerk reaction as most others have here. Clearly they are misusing statistics in order to find the correlation they want to see. Correlation is not the same as causality, in other words. I have not read the original study so I can’t say how scientific…

      The graph looked very convincing……I mean the dips and peaks coincided….?

  10. It’s a demographics response.

    Same thing is the explanation for the collapse of civilisation in the Islamic world playing out at present. Basically there’s a surge in young men with few opportunities for meaningful work, combined with relatively limited access to females in a very narrow reproductive age range. (Lack of employment prospects is known to be one of the least sexually attractive qualities in young men. Plus young women tend to be monopolised by older and much wealthier serial monogomists in many Islamic societies where wealth is extremely stratified.)

    Opportunistic and impulsive crime is pretty much entirely done by young males in this narrow age range. Same for other species of chimps.

    Eventually they get a girlfriend, no longer live with their mums, and become more or less socialised by the time some of them are ready to join the army, police, banks, or to run for political office. From then on their crimes become less overt, though possibly of greater negative impact.

    Crime rates can only grow in a community if that narrow age range cohort is also growing. Otherwise crime rates plummet as increasing numbers of formerly youthful offenders become too old and lazy to be that stupid.

    Demographics mitigating against this population bulge have multiple sources: decline in fertility beginning in the early 1960s as general response to the cholesterol / fat theory of heart attacks (fertility impact most likely attributable to reduced dietary fat combined with increased wheat starch and sugar consumption), along with either post-natal abortions via lead toxicity in infants, or pre-natal abortions as in abortion legislation.

    Example might be the rapid appearance of vandalism and littering at public facilities that suddenly appeared throughout the world in the late 1960’s through late 1970s. (Blamed on hippies and men wearing long hair.) But probably was a result of returned WW2 service people settling down and having kids all around the same time. Older parents having kids being delayed by military service. So there was something of a boom in the age range of 15 to 25 year olds approximately from 1965 to 1975.

    Putnam has linked this stuff with the introduction of television viewing – the crime boom closely associated with the collapse in civil institutions that occurred in most nations following commencement of TV broadcasting. Though at different times throughout the world.
    There’s also the contribution from unstable welfare policy. E.g. Net incentives for having dependent children, financial advantages of family breakup etc.

    Japan was exempt from a lot of this. Possibly because so many youths were employed in actually making TVs in the 1960s and 70s, instead of watching them. Plus there may have been less of a demographic surge owing to relatively few WW2 servicemen surviving to return home and reproduce.

  11. Where is the epidemiology? This looks tragically undercooked. So many alternative mechanisms and no work done to eliminate them.

    My favourite two mechanisms for the rise and fall of crime-

    Mad Men. The advent of a consumer society driven by the promotion, through advertising, of jealousy and dissatisfaction.

    Chinese made stuff. Everything becoming much more affordable.

  12. I watched an interesting TV documentary last night about psychopaths and what profession might harbour the non jailed ones in our society….. bankers were high on the spectrum….ruthless, risk takers, greedy and focussed on one goal – regardless of the harm to others……Interesting when you consider crime is not committed by only poor people on the streets – which is what police statistics like these are designed to make you think…….but crime is covertly operating among the psychopaths at the top level of our society….

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