Crime is down because of less lead?

[wgbgator]

Seems crazy, but somewhat persuasive too.

http://www.motherjones.com/kevin-drum/2013/01/lead-crime-connection

I've written several posts recently about the idea that America's great crime epidemic, which started in the 60s and peaked in the early 90s, was caused in large part by lead emissions from automobiles. Long story short, we all bought lots of cars after World War II and filled them up with leaded gasoline. This lead was spewed out of tailpipes and ingested by small children, and when those children grew up they were more prone to committing violent crimes than normal children. Then, starting in the mid-70s, we all began switching to unleaded gasoline. Our kids were no longer made artificially violent by lead poisoning, and when they grew up in the mid-90s they committed fewer violent crimes. This trend continued for two decades, and it's one of the reasons that violent crime rates have dropped by half over the past 20 years and by more than that in our biggest cities. It's one of the great underreported stories of our time: big cities today are as safe as they were 50 years ago.

That's the short version of the story. The long version of the story is on the cover of the current issue of Mother Jones, and today it's available online for the first time. Click here to read it. The chart on the right illustrates the basic data that inspired the lead hypothesis: it shows lead emissions starting in 1935 overlaid with the violent crime rate 23 years later. The two curves match almost perfectly.

[Dreamliner]

Lead must be up in Chicago then.

[mdgator05]

There is a lot of good work that has been done on this issue, including some pretty solid predictive models around the world of when the dramatic dropoff in crime would occur.

A good example of the need for a solid environmental program and the existence of the tragedy of the commons, where people were victims of violent crime at a higher rate due to a decision that was individually rational but socially irrational.

[Dreamliner]

This is good news on another front. If it really turns out to be the environment, then we no longer have to bother with quaint terms like 'right and wrong' and 'good and evil.'

[wgbgator]

Lead must be up in Chicago then.

Eh, not really. Chicago fits the downward trend too.

1974: 970 murders
2012: 506 Murders (up from 2011's 435, the lowest # in decades)

[Dreamliner]

Eh, not really. Chicago fits the downward trend too.

1974: 970 murders
2012: 506 Murders (up from 2011's 435, the lowest # in decades)

Yep, lead is up this year. It's the environment, stupid.

[mdgator05]

Yep, lead is up this year. It's the environment, stupid.


Lead exposure is an issue amongst children. That is why there is about a 20-25 year lag. It is unlikely that lead exposure is up this year. In fact, we are probably reaching the point where crime declines will slow somewhat, as the lead exposure in childhood for young adults has pretty much cratered to very low levels. We might get some slight continued declines due to the fact that crime likely has an autoregressive component, but we are likely to see more random movements in crime than we have experienced over the last 20 years due to the fact that lead levels had really cratered by the mid 1980s.

http://www.motherjones.com/files/Lead_Crime_325.gif

As for getting rid of the whole correlation does not equal causation counterpoint, the author effectively dealt with that:

Not only does lead promote apoptosis, or cell death, in the brain, but the element is also chemically similar to calcium. When it settles in cerebral tissue, it prevents calcium ions from doing their job, something that causes physical damage to the developing brain that persists into adulthood.

Only in the last few years have we begun to understand exactly what effects this has. A team of researchers at the University of Cincinnati has been following a group of 300 children for more than 30 years and recently performed a series of MRI scans that highlighted the neurological differences between subjects who had high and low exposure to lead during early childhood.

One set of scans found that lead exposure is linked to production of the brain's white matter—primarily a substance called myelin, which forms an insulating sheath around the connections between neurons. Lead exposure degrades both the formation and structure of myelin, and when this happens, says Kim Dietrich, one of the leaders of the imaging studies, "neurons are not communicating effectively." Put simply, the network connections within the brain become both slower and less coordinated.

A second study found that high exposure to lead during childhood was linked to a permanent loss of gray matter in the prefrontal cortex—a part of the brain associated with aggression control as well as what psychologists call "executive functions": emotional regulation, impulse control, attention, verbal reasoning, and mental flexibility. One way to understand this, says Kim Cecil, another member of the Cincinnati team, is that lead affects precisely the areas of the brain "that make us most human."

[Dreamliner]

It's also unlikely that lead was ever making us violent. Seriously, there is a poster on Too Hot who earnestly believes that fake blueberries are killing us.

[mdgator05]

It's also unlikely that lead was ever making us violent. Seriously, there is a poster on Too Hot who earnestly believes that fake blueberries are killing us.

Except for the fact that science has determined that lead exposure in childhood makes individual people more violent and the aggregate exposure rates seem to match up very closely with aggregate violence rates, a result that has been replicated across a wide variety of cultures, including our own.

If you are going to challenge pretty well established science, it helps to have something to work with beyond not wanting something to be true.

[Dreamliner]

Except for the fact that science has determined that lead exposure in childhood makes individual people more violent and the aggregate exposure rates seem to match up very closely with aggregate violence rates, a result that has been replicated across a wide variety of cultures, including our own.

If you are going to challenge pretty well established science, it helps to have something to work with beyond not wanting something to be true.

So, did we get bored with all the other factors that may occasion violence ? Is lead exposure sexier ? It certainly sounds more insidious.

My advice would be to wait for critiques of this study to roll in. Also, factor in new and exciting theories such as the addition of flouride to water supplies over the last few decades. You know, the Nazis used it on the Jews as a tranquilizer.

[mdgator05]

So, did we get bored with all the other factors that may occasion violence ? Is lead exposure sexier ? It certainly sounds more insidious.

My advice would be to wait for critiques of this study to roll in. Also, factor in new and exciting theories such as the addition of flouride to water supplies over the last few decades. You know, the Nazis used it on the Jews as a tranquilizer.

The examination of a major factor in violence does not prevent the examination of other factors. But lead exposure has been researched for quite some time, leading to plenty of time for critiques to examine this issue. Here is an article from 2007 outlining the research done by an economist on lead exposure and violent crime across 9 different countries.

http://www.washingtonpost.com/wp-dyn/content/article/2007/07/07/AR2007070701073.html

Nevin says his data not only explain the decline in crime in the 1990s, but the rise in crime in the 1980s and other fluctuations going back a century. His data from multiple countries, which have different abortion rates, police strategies, demographics and economic conditions, indicate that lead is the only explanation that can account for international trends.

Because the countries phased out lead at different points, they provide a rigorous test: In each instance, the violent crime rate tracks lead poisoning levels two decades earlier.

"It is startling how much mileage has been given to the theory that abortion in the early 1970s was responsible for the decline in crime" in the 1990s, Nevin said. "But they legalized abortion in Britain, and the violent crime in Britain soared in the 1990s. The difference is our gasoline lead levels peaked in the early '70s and started falling in the late '70s, and fell very sharply through the early 1980s and was virtually eliminated by 1986 or '87. In Britain and most of Europe, they did not have meaningful constraints [on leaded gasoline] until the mid-1980s and even early 1990s," he said. "This is the reason you are seeing the crime rate soar in Mexico and Latin America, but [it] has fallen in the United States."

The centerpiece of Nevin's research is an analysis of crime rates and lead poisoning levels across a century. The United States has had two spikes of lead poisoning: one at the turn of the 20th century, linked to lead in household paint, and one after World War II, when the use of leaded gasoline increased sharply. Both times, the violent crime rate went up and down in concert, with the violent crime peaks coming two decades after the lead poisoning peaks.

I have hit the four paragraph limit, but continue reading on the second page for a variety of other research projects that have examined this issue. The first shows that counties with higher lead exposure amongst children have 4x higher murder rates, controlling for socio-economic factors. Other studies show that violent criminals have much higher rates of lead exposure than the general population. As pointed out by the Johns Hopkins Prof, none of this stuff is seen as that controversial right now in scientific communities.

[Dreamliner]

Hmm, lead must be up (or flouride or abortions or violent video game sales up) in a number of US cities not cooperating with the trends.

[mdgator05]

Hmm, lead must be up (or flouride or abortions or violent video game sales up) in a number of US cities not cooperating with the trends.

As stated in the article I just posted, lead exposure cratered in the US in the mid 1980s. Applying the 20-25 year lag, you see that crime rates due to lead exposure in the US should have cratered about 2005-2010. Now we are likely seeing a return to a more random walk sort of time series, in which random effects increase and decrease crime in different locations. So while overall violent crime is still declining, a normally distributed change from a previous point will result in a greater number of local increases.

[Dreamliner]

As stated in the article I just posted, lead exposure cratered in the US in the mid 1980s. Applying the 20-25 year lag, you see that crime rates due to lead exposure in the US should have cratered about 2005-2010. Now we are likely seeing a return to a more random walk sort of time series, in which random effects increase and decrease crime in different locations. So while overall violent crime is still declining, a normally distributed change from a previous point will result in a greater number of local increases.

And as I just stated, some cities are defying the trends. This is a confounder that has to be accounted for. And I doubt that these studies have controlled for 'social factors' at least as likely to contribute to fluctuations in crime.

[oragator1]

And when did the baby boomers go through their peak crime years? I think you will see another correlation not dissimilar from the lead chart.
I have no problem with lead being looked at, it's interesting and probably has some merit, I just think the chart is a bit simplistic for something that probably has dozens of contributing factors.

[mdgator05]

And as I just stated, some cities are defying the trends. This is a confounder that has to be accounted for. And I doubt that these studies have controlled for 'social factors' at least as likely to contribute to fluctuations in crime.

You don't seem to understand what is going on with this research. Again, crime due to lead exposure should have cratered between 2005-2010. So any variation now is unlikely to be due to lead exposure issues. Now we are likely looking at a random walk, since lead exposure has worked its way out of the environment for the most part in most of the US.

BTW, that isn't a "confounder." A confounding variable would be a variable that correlates with both the independent and dependent variable. You did not suggest a confounding variable nor provide any evidence of this confound.

These studies have controlled for a huge number of socio-economic factors or, in the case of Nevin, used an international dataset that allowed for the controlling of these variables through differences in countries. For example, it allows the author to rule out abortion because it was made legal earlier in Britain, but the increase in violent crime occurred in the 1990s, which coincides with the fact that British lead levels didn't start dropping until later than in the US.

[mdgator05]

And when did the baby boomers go through their peak crime years? I think you will see another correlation not dissimilar from the lead chart.
I have no problem with lead being looked at, it's interesting and probably has some merit, I just think the chart is a bit simplistic for something that probably has dozens of contributing factors.

It is possible that demographic issues was a secondary causal factor, but it is unlikely a primary cause as this relationship has been shown internationally at different points in time, which would not coincide with the Baby Boomer demographic change.

[oragator1]

It is possible that demographic issues was a secondary causal factor, but it is unlikely a primary cause as this relationship has been shown internationally at different points in time, which would not coincide with the Baby Boomer demographic change.

Do you have any charts on other countries, I would be interested in seein them.

[Dreamliner]

You don't seem to understand what is going on with this research. Again, crime due to lead exposure should have cratered between 2005-2010. So any variation now is unlikely to be due to lead exposure issues. Now we are likely looking at a random walk, since lead exposure has worked its way out of the environment for the most part in most of the US.

BTW, that isn't a "confounder." A confounding variable would be a variable that correlates with both the independent and dependent variable. You did not suggest a confounding variable nor provide any evidence of this confound.

These studies have controlled for a huge number of socio-economic factors or, in the case of Nevin, used an international dataset that allowed for the controlling of these variables through differences in countries. For example, it allows the author to rule out abortion because it was made legal earlier in Britain, but the increase in violent crime occurred in the 1990s, which coincides with the fact that British lead levels didn't start dropping until later than in the US.

You don't seem to want to acknowledge that a number of cities are simply not cooperating with your convenient hypothesis. There are cities where crime is, in fact, soaring and not rebounding to a 'normal walk', as you put it.

Now, lead exposure might be *a* factor in crime, but how much of a factor ? On the other hand, even studies showing lead exposure affecting IQ have been called into question.

I agree with oragator. This is far too simplistic. I could just as easily argue that government policy has exacerbated crime rather than ameliorate it.

[oragator1]

By the way, one other point on violent crime, it's been generally dropping for 450 years:

http://madeinamericathebook.files.wordpress.com/2010/05/violence-stylized2.png?w=430&h=295

[oragator1]

One other point on demographics, here is an article that shows a strong correlation over the long term, including now.

http://kondratiefflongwave.com/kondratieff-cycle-wave/violent-crime/

[mdgator05]

You don't seem to want to acknowledge that a number of cities are simply not cooperating with your convenient hypothesis. There are cities where crime is, in fact, soaring and not rebounding to a 'normal walk', as you put it.

Now, lead exposure might be *a* factor in crime, but how much of a factor ? On the other hand, even studies showing lead exposure affecting IQ have been called into question.

I agree with oragator. This is far too simplistic. I could just as easily argue that government policy has exacerbated crime rather than ameliorate it.

Really? Soaring? That is a very subjective term. By that standard, it is "plummeting" in other places. Again, we aren't talking about crime stats in the last two years. We are talking about the trend that started in the mid-1990s and ran for about 15 years. How many places can you find with a higher violent crime rate now than in the late 1980s or early 1990s? You mentioned Chicago, because their crime rate went up in one year, but it was already demonstrated that it had spent the time window in question declining.

BTW, a series of several thousand random walks are going to contain some with a large increase if the random walk is defined by a normal curve with a reasonable sized variance.

[mdgator05]

One other point on demographics, here is an article that shows a strong correlation over the long term, including now.

http://kondratiefflongwave.com/kondratieff-cycle-wave/violent-crime/

Per capita rates for younger people has also shown a massive decline in the same period. If the explanation was primarily demographic, the per capita rates should remain fairly constant. They have not, and have much more closely matched the graph I posted earlier. The per capita rates amongst older juveniles (ages 15-17) and young adults (18-24) dropped off in the mid 90s rapidly (as the lead exposure research would predict). Contrary to the predictions of a demographic based model, which would predict no trend in the per capita violent crime rates.

http://johnjayresearch.org/wp-content/uploads/2012/04/databit2012_06.pdf

[oragator1]

Per capita rates for younger people has also shown a massive decline in the same period. If the explanation was primarily demographic, the per capita rates should remain fairly constant. They have not, and have much more closely matched the graph I posted earlier. The per capita rates amongst older juveniles (ages 15-17) and young adults (18-24) dropped off in the mid 90s rapidly (as the lead exposure research would predict). Contrary to the predictions of a demographic based model, which would predict no trend in the per capita violent crime rates.

http://johnjayresearch.org/wp-content/uploads/2012/04/databit2012_06.pdf

I never said it was primarily demographic, as I said in my first post there are many causal factors. I was providing the article to show that there is evidence to support a number of things. Additionally, if your graph was wholly accurate for the claim, crime should have dropped to where it was before the lead gas boom. But it has almost leveled with a much slower rate of decline, though the lead graph says it should continue to fall. My other post was to show is part of a much longer term trend of lowering crime rates with no simple or singular explanation.
Again, I have no problem saying lead is a contributing factor, it very well my be. But even the chart itself shows that it isn't a straight relationship, and if it isn't on the back side (i.e. recent years), there is legitimate reason to doubt a straight correlation on the front as well.

[Row6]

Interesting theory. I'm hoping jdrgator is back soon to comment.

[corpgator]

As for getting rid of the whole correlation does not equal causation counterpoint, the author effectively dealt with that:

Such an abused quote. The real quote is correlation does not prove causation. It is a great argument for it, though, and should definitely cause follow up studies to confirm.

[northgagator]

Md and Wg,

Was there any mention in the research of the reduction or the elimination of lead from paint?
I am referring to the many children of early and mid 20th century who were subjected to long period of exposure to lead paint.

[Row6]

Md and Wg,

Was there any mention in the research of the reduction or the elimination of lead from paint?
I am referring to the many children of early and mid 20th century who were subjected to long period of exposure to lead paint.

Main source cited is exhaust fumes. Lead paint is harmless unless one eats chips or breaths in dust caused by it's removal.

[HALLGATOR]

Main source cited is exhaust fumes. Lead paint is harmless unless one eats chips or breaths in dust caused by it's removal.

Wonder how much lead paint was used on cribs before they found out it was so toxic?

[northgagator]

Main source cited is exhaust fumes. Lead paint is harmless unless one eats chips or breaths in dust caused by it's removal.

Rowe, eating the chips or flakes was a big problem. Especially in the older or substandard housing. The old lead paint would chip or flake off the walls and wood trim and become tempting snacks for toddlers and even the older kids.

[Row6]

Wonder how much lead paint was used on cribs before they found out it was so toxic?

Almost all of it since manufactured products were probably oil based.

[Row6]

Rowe, eating the chips or flakes was a big problem. Especially in the older or substandard housing. The old lead paint would chip or flake off the walls and wood trim and become tempting snacks for toddlers and even the older kids.

I agree though the inhalation of exhaust fumes affected more people. I didn't mean to belittle the seriousness of lead in paint. I have trained in lead paint removal, a federal requirement for anyone involved in remodeling or demolition of homes built before 1978. This requirement does not apply to commercial remodeling or demolition.

[Minister_of_Information]

Agree with Row, leaded gasoline was a much larger environmental issue than paint.

[MichaelJoeWilliamson]

Interesting viewpoint on the matter found here; (http://justoneminute.typepad.com/)

That said, the intellectual ball has advanced and Kevin has interesting points about both abatement possibilities (lead dust doesn't just walk away) and the non-embrace of this theory amongst the criminologist community.

However, on that latter point this struck me as strangely unreflective:

My own sense is that interest groups probably play a crucial role [in ignoring the lead-crime connection]: Political conservatives want to blame the social upheaval of the '60s for the rise in crime that followed. Police unions have reasons for crediting its decline to an increase in the number of cops. Prison guards like the idea that increased incarceration is the answer. Drug warriors want the story to be about drug policy. If the actual answer turns out to be lead poisoning, they all lose a big pillar of support for their pet issue. And while lead abatement could be big business for contractors and builders, for some reason their trade groups have never taken it seriously.

Hmm. And why have liberals progressives, the people of science, not been trumpeting these discoveries? A plausible intrepretation of these results is that America has a generation of lead-poisoned, brain-damaged urban blacks who are old enough to be less violent but still afflicted with reduced IQ and reduced impulse control. Is that where MSNBC wants to go? Is there a prominent Democrat who wants to stand up and tell us that one of the pillars of the Democratic Party is disproportionately brain-damaged, through no fault of their own? I don't think so.

And heaven help any Republican who suggests we need to spend billions getting the lead out of our inner cities so we can stop damaging the brains of the urban poor. Science notwithstanding, it sounds racist. Maybe Mayor Bloomberg could have pulled it off, but he is leaving.

[wargunfan]

Now that the lead menace has been eliminated are we down to the baseline evil of people in the US? By the standard of lead exhaust effects the Chinese will be the most violent people on earth starting in about 15-20 years (they mostly rode bicycles until about 10-15 years ago).

[northgagator]

Agree with Row, leaded gasoline was a much larger environmental issue than paint.

Oh I not debating how nasty led in auto/truck exhaust versus paint. I know the breathing lead into your lungs is worst than eating lead tainted paint chips.

I was wondering if getting lead out of paint was considered as a factor. I do know that there is a history of lead impacting a civilization/culture. The ancient Romans encountered issues with the use of lead plumbing, wine/food jugs, and table ware tainted with lead. http://www.nytimes.com/1983/03/17/us/roman-empire-s-fall-is-linked-with-gout-and-lead-poisoning.html

[mdgator05]

Interesting viewpoint on the matter found here; (http://justoneminute.typepad.com/)

The original article was from Mother Jones, a major liberal publication, similar to National Review or Weekly Standard on the left. So I am not sure how the left hasn't been promoting this theory. This sounds like another desperate attempt to shoehorn blame for anything possible towards minorities and "the left." So in reality, not very interesting and pretty regular stuff from much of the right.

[MichaelJoeWilliamson]

The original article was from Mother Jones, a major liberal publication, similar to National Review or Weekly Standard on the left. So I am not sure how the left hasn't been promoting this theory. This sounds like another desperate attempt to shoehorn blame for anything possible towards minorities and "the left." So in reality, not very interesting and pretty regular stuff from much of the right.

I think you misunderstood the guy's point. You might want to re-read it.

[mdgator05]

I think you misunderstood the guy's point. You might want to re-read it.

So the point wasn't:

Hmm. And why have liberals progressives, the people of science, not been trumpeting these discoveries? A plausible intrepretation of these results is that America has a generation of lead-poisoned, brain-damaged urban blacks who are old enough to be less violent but still afflicted with reduced IQ and reduced impulse control. Is that where MSNBC wants to go? Is there a prominent Democrat who wants to stand up and tell us that one of the pillars of the Democratic Party is disproportionately brain-damaged, through no fault of their own? I don't think so.

Blaming the liberals ("the people of science") for not spreading this theory while we read an article on it from Mother Jones and declaring that the reason it hasn't spread is because liberals don't want to talk about "Brain-damaged urban blacks" is complete garbage and race baiting.

[wgbgator]

That's pretty absurd on multiple counts, first that it was only blacks that were more violent from lead and cmmiting crimes, second that criminals (who typically have their voting rights removed) are a big core reliable voting support for progressives, and three that there aren't liberals entertaining the idea that lead might account for some of these things.

[Lawdog88]

By the way, one other point on violent crime, it's been generally dropping for 450 years:

http://madeinamericathebook.files.wordpress.com/2010/05/violence-stylized2.png?w=430&h=295



So . . . I guess there is an upside to increased CO2 in the air ?

Finally. A correlation.

[wargunfan]

So . . . I guess there is an upside to increased CO2 in the air ?

Finally. A correlation.

Apparently the high levels of CO2 in the atmosphere have a calming effect. That's nice. :laugh:

[MichaelJoeWilliamson]

So the point wasn't:



Blaming the liberals ("the people of science") for not spreading this theory while we read an article on it from Mother Jones and declaring that the reason it hasn't spread is because liberals don't want to talk about "Brain-damaged urban blacks" is complete garbage and race baiting.

I think he also took conservatives to task for their point of view on the matter? So, nice convenient editing on your part.

Keep it up and you might land a job with CNN or the NYT.

[MichaelJoeWilliamson]

By the way, one other point on violent crime, it's been generally dropping for 450 years:

http://madeinamericathebook.files.wordpress.com/2010/05/violence-stylized2.png?w=430&h=295

There is a theory that the rise of capitalism is the single most important impact on human to human violence. The theory is that as commerce has increased violence has decreased.

"Make money, not war."

http://reason.com/blog/2009/08/24/the-slow-death-of-violence

http://greatergood.berkeley.edu/article/item/why_is_there_peace

[mdgator05]

I think he also took conservatives to task for their point of view on the matter? So, nice convenient editing on your part.

Keep it up and you might land a job with CNN or the NYT.

Yah he blamed them in a way that he could still blame liberals indirectly ("It sounds racist.") It is just more of the victimhood complex on the right. "I can't say Black people are brain damaged without being called a racist. I would totally help those brain damaged black people if those dirty liberals would stop calling us racists."

As I said, more of the same from the right. Inability to take any actual blame. Race baiting. Ridiculous attempts to blame everything on liberals. Unfortunately, at this point, in many on the right, this has become so ingrained in their sense of identity that they don't seem to even realize how ridiculous it sounds. You just posted an article in response to a thread started with a Mother Jones article on this science blaming liberals for this science not becoming more known. And for some reason, you fail to see why that is completely ridiculous.

[MichaelJoeWilliamson]

Yah he blamed them in a way that he could still blame liberals indirectly ("It sounds racist.") It is just more of the victimhood complex on the right. "I can't say Black people are brain damaged without being called a racist. I would totally help those brain damaged black people if those dirty liberals would stop calling us racists."

That was one of his points about conservatives. In fairness, he said the same thing about liberals avoiding the issue for the same reason. And it was only one of at least two points he made about conservatives

Whatever floats your boat.

[MichaelJoeWilliamson]

From Reason Magazine (http://reason.com/blog/2013/01/04/leading-poisoning-causes-crime)

In addition, even as exposure to tetra-ethyl lead rose, average American IQ scores have been increasing at the rate of about 3 points per decade for nearly a century, up about 22 points since 1932 [PDF]. This increase is the well-known Flynn Effect, named after the New Zealand researcher, James Flynn, who first identified the steady rise in average IQ scores. Note that average IQ scores have been increasing ever since tetra-ethyl lead was first added to gasoline in the mid-1920s.

The good news is that the percentage of kids diagnosed with learning disabilities has fallen by 19 percent since 2001, although the absolute number of learning disabled students remains about the same. Part of the happy decline can be attributed, as the National Center for Learning Disabilities notes to the...

...Change in federal funding formula (beginning in 2000) no longer rewards high rates of special education identification in local districts combined with stagnant federal funding levels.

Interestingly, in a 2012 working paper Nevin argues that the increase in IQs in the early part of the 20th century resulted from lessened exposure to lead paint and that increases in the average IQ scores slowed down as tetra-ethyl lead exposure from gasoline rose. Perhaps Nevin would argue that the increase in the U.S murder rate from 1.2 per 100,000 in 1900 to 9.7 per 100,000 in 1933 can be attributed to rising lead paint exposure?

Drum is right that exposure to lead increases the chances that a person will suffer the sorts of neurological damage that lowers their intelligence and lower intelligence is well-known to correlate with increased criminality. Reducing such exposures has no doubt contributed to our happily falling crime rates. But it is likely that other factors including more policing, more incarceration, less crack, increased concealed carry, and other such efforts to control crime have contributed as well.