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New Evidence That Lead Exposure Increases Crime (2017) (brookings.edu)
329 points by anarazel 7 months ago | hide | past | web | favorite | 147 comments

> When lead was removed from gasoline, lead levels in the environment fell, and kids avoided the lead exposure that caused these developmental problems. About 20 years later, when those kids became young adults, crime rates fell. This, proponents say, is what explains the mysterious and persistent decline in crime beginning in the early 1990s.

> It’s an intriguing idea — particularly since we don’t have a better explanation for the big changes in crime rates during this period.

Did not freakanomics come up with a famous (and to me more convincing) argument that it legalized abortion was the reason for the drop in crime? At they very least it dispels the arguments we don't have a better explanation and doesn't even mention it.


One of the interesting things about social science observations is there's a lot of noise.

Both the lead and the abortion hypotheses could be true. In fact they could both be true AND the papers indicating one explanation could conceivably throw out the other explanation. If you're interested in one hypothesis, you might not spend the time going through alternatives as thoroughly as someone investigating the other.

Looking specifically, the studies are always trying to isolate some effect, often using some sort of clever control derived from the proposed mechanism. So in this case there's a paper that points out how lead only goes into the water if the water is acidic, and they look at places with non-acidic water or non-lead pipes to control. For abortion, it's been a while since I read it, but there would be something along the lines of when abortion became widespread in a given community. You'd then look at differences in frequency and think about whether that came out in the crime stats when the kids got older.

The rabbit hole is where you can come up with ever more interesting corollaries and data that support or do not support some hypothesis. You see this across the social sciences all the time. There's also confounding problems, say you know people tend to move to the city when they grow up (I don't know if this is true), then how valid is your birth -> crime data?

Here's a load of random observations I thought up:

- If abortion is the key, why do crime rates keep falling? Why is it not a step effect?

- If it's lead, did crime rates increase 20 years after leaded fuel became a thing?

- What if it's abortion AND lead? There are countries where abortion and lead are timed differently, how about looking at them?

- What if it's neither, but both are caused by some other thing? Say economic development -> both?

>> If it's lead, did crime rates increase 20 years after leaded fuel became a thing?

Yes. The rise and fall of violent crime rates correlate very tightly to the rise and fall of leaded fuel, with a ~20 year gap. You see the same correlations in different countries that had different phase in / phase out times, and different U.S. states that had different timelines. (E.g. if a state phased out leaded gas 5 years earlier than average, their crime wave also started abating 5 years earlier than average)

Source? Crime in general decreased quite a lot after the depression, but the use of leaded gasoline was quite prevalent regardless.

Leaded gasoline was introduced in the 1920s but there weren't that many cars until starting in the late 1950s. (Construction of the interstates started with the Federal Aid Highway Act of 1956.) Then we saw the huge crime wave starting 20 years later, which peaked and started tapering off in 1993, 20 years after the phase out of leaded gasoline began in 1973.

There is also the point that the people who did have cars in the 1920s were the aristocrats, and twenty years after that...

> Then we saw the huge crime wave starting 20 years later, which peaked and started tapering off in 1993...

This seems to correlate fairly well with the government's war on (certain) drugs as well.

It also correlates with population density, public housing, migration, and crack cocaine use.

I highly doubt there's one contributing factor to crime, and I highly doubt it is solely from leaded gasoline.

There are many things that influence crime, the question is how much of the total variance is due to gasoline?

And the answer from this research is quite a lot, because the timing of the rise and fall in crime match the timing of leaded gasoline (with a 20-year lag) across cities, states, and countries.

To say that 'other factors are responsible' would be to posit that there is some other factor that holds both across and within different cultures and countries that perfect accounts for the pattern in crime rates that we see. That seems much harder to believe than simply 'leaded gasoline causes crime', which we both have robust evidence for now, and for which we have a very plausible mechanism of action.

Ok, so I'm not disputing that peope born in the 60s had more lead in their blood than people born in the 80s/90s. Additonally, I'm not disputing that lead causes behavioral and physical problems. It definitely does.

However, I would like to see the specific data that says the following (because I'm not seeing it when I read the article):

"Regardless of the crack epidemic in the 1980s, regardless of the decline in public housing in the 1980s, regardless of the rise of police surveillance technology, we have indisputable evidence that lead in the blood causes an increase in crime locally and nationwide by XMeaningfulPercent".

I'd be surprised if one could ever make such a statement.

The data we currently have shows that someone born in 1960 and committing a crime in 1985 has been exposed to lead, but they also might have been exposed to crack. Additionally, declining government project housing provided strong protection for criminals to hide from police, and the police surveillance technology in 1985 was pitiful compared to the massive levels of surveillance now.

None of these factors exist anymore in 2018. Crime is much lower. How can we say which variable contributed in which amount?

> "Regardless of the crack epidemic in the 1980s, regardless of the decline in public housing in the 1980s, regardless of the rise of police surveillance technology, we have indisputable evidence that lead in the blood causes an increase in crime locally and nationwide by XMeaningfulPercent".

> I'd be surprised if one could ever make such a statement.

"We found some cities where crack got big at different times but lead came at the same time"

"We found some cities where public housing declined at different times but lead came at the same time"

"We found some places where police surveillance..."

This is the aforementioned rabbit hole. People will have studied such evidence to various degrees.

Maybe they liked crack so much because they'd been exposed to so much lead.

But seriously, the point of this article is that studies still find a correlation between lead exposure and crime, after accounting for confounding.

And yet, that's not the same arguing that lead exposure was the only cause of the crime boom.

Your standards are bullshit and you know it. We can't say such statements of indisputable evidence about anything that happens in the world. Should we throw our hands up and just say, well it could be invisible llamas, or tree gnomes, or the boogey man, or should we use the best available evidence to guide future decisions?

From one of the papers cited in the parent article:

"A growing body of evidence in the social and medical sciences traces high crime rates to high rates of lead exposure. Scholars have shown that lead exposure and crime are positively correlated using data on individuals, cities, counties, states, and nations. Reyes (2007) exploits state-specific reductions in lead exposure due to the Clean Air Act to estimate the effect of lead emissions from gasoline on violent crime. She reports that reductions in childhood lead exposure in the 1970s and 1980s accounted for more than half of the violent crime decline of the 1990s.2 Stretesky and Lynch (2001) estimate that, from 1989 to 1991, counties with air lead levels equivalent to .17 μg/m3 had homicide rates four times as high as counties with air lead levels equivalent to 0 μg/m3. Mielke and Zahran (2012) show that air lead and aggravated assault rates were strongly associated in a panel of U.S. cities. Longitudinal studies of individuals document a positive relationship between pre- and post-natal lead exposure and delinquency (Dietrich et al., 2001) and arrests for violent offenses (Wright et al., 2008). Cross-sectional research on individuals (Denno, 1990; Needleman et al., 1996, 2002) and counties (Stretesky and Lynch, 2004), studies using cross-national panel data (Nevin, 2007), and analyses of national time-series (Nevin, 2000) have yielded similar results."

Are each of these going to be able to factor for every possible confounder you can think of? No. But it's not like they aren't controlling for anything. That's the whole gist of the parent article - three studies using three new ways of controlling for other variables. Have you seen multitudes of studies that point to any of those other confounder you mention having better evidence, across time and geography, while controlling for lead and all the other possible confounders? Again, nobody is arguing that there are no other factors. And nobody has a precise answer on just how much, because it's impossible. But all studies point to: very large effects, still happening in some cases, and largely preventable: https://www.dropbox.com/s/07z65p9a5wdppfl/LifeAfterLead_AEJ_...

> Your standards are bullshit and you know it.

Aggressiveness like this will get you banned on HN. Please read https://news.ycombinator.com/newsguidelines.html and follow the rules when posting here.

I mean I'd say that in civil conversation, face to face. Is swearing the problem? I was providing substantive contributions to the conversation, whereas conversant was, in my opinion, doing neither of these:

> Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.

> Please don't post shallow dismissals

But perhaps doing neither of them more "civilly"? I'm genuinely looking for guidance on handling of this thread, not trying to argue. Thanks.

There's no need to say that I have bullshit standards. I literally agreed with you that lead is a contributing factor.

You seem to agree with me that there are other contributing factors.

Now that we're both happy, I will thank you for the work you put into investigating the sources and bid you a very happy, unleaded farewell.

I had too much lead in my coffee this morning

Nobody is stating there is a single factor. But it appears to be the largest that we can plausibly put a finger on. When you see the same correlations across different countries, states, and local jurisdictions that did not have identical drug policies, immigration/migration patterns, policing strategies etc. etc. etc, it becomes convincing. The three studies in this article provide even more evidence, using clever experimental designs to control for as many of these other variables as they can. Did you read the article? Do you have specific comments on how those studies are or are not contributing to our knowledge?

I did indeed read the article and replied to a different commenter below. I don't dispute that lead is a contributing factor.

I think it's impossible to say how much any factor contributes in a quantitative manner. "36% of crimes were committed in high lead areas, whereas 23% of crimes were committed in high crack consumption neighborhoods"?

I think it's all a mish mash of variables and it's best not to pick apart too many strands of data.

One thing we can say for certain is that murders are down 50% since 1980 despite population in the USA doubling. That is an amazing achievement and I highly, highly doubt it was chiefly due to our generation not having lead in their blood.

That’s an extremely strong statement to make without extensive examination of the actual data and studies by people using the actual data. Really, the first thing you try and find is the magnitude of impact which give exactly what you say is impossible to find.

Someone can go do that literature review then.

On an anecdotal basis only, which sounds more plausible, then:

1) Murder rates are 4x lower chielfy/solely because of unleaded gas


2) Murder rates are 4x lower because of quite a few qualitative observations that we think data would confirm each played a role.

It's like saying, "I think murder rates are higher in Norway compared to Sweden not because of some big societal difference between the two countries, but probably because I remember a news story where a depraved lunatic shot 90 kids on an island."

I can’t let this go. It’s nothing like that. Yes, you are just positing opinions as if they’re facts, but that’s not everyone. There has been reviews of the literature. E.g I can’t recall the book off the top of my head but something like out 120 studies on effectiveness of different policing strategies, only ~20% of studies showed statistical significant effects for any given strategy and a fair amount of those failed to replicate. Meanwhile we’ve continually had studies pointing to lead as a significant driver with significant effect sizes. You keep strawmanning this “solely” argument that no one is making while also ignoring the plethora of data pointing to it being a huge driver, and by the far the largest driver with any body of evidence. It’s not like this stuff isn’t being studied, yet I challenge you to find studies that can show anything near the evidence for these other factors.

No one said that lead is the only driver of crime. So lead and economic factors along with other causes can all jointly affect crime ratesand therefore correlate with it.

You see the same things with abortion. The states that phased in legalized abortions had their crime rates dropping before the ones that did. This too is in the freakanomics argument.

Industrialization/deindustrialization or something similar is not a confounding variable?

I like this argument which only looks at very long term statistics. Violent crime has been decreasing since colonial times if not earlier and globally. In this sense, a particular decrease in violent crime doesn't explanation as such (though the long term trend does. Perhaps lead exposure has been decreasing for a long time, perhaps not). Increases in crime, long term, are correlated roughly with veterans returning from war.

See this link for the argument.


Edit: also the original lead argument pretty hinges on a single moment of crime increase. I don't see how more detailed studies of the correlation could be more revealing since reality only provides one instance of a potential to leaded gasoline and reality is going to be noisy.

The author ends his post by stating that the rise of crime from the 60s through the 80s is a major puzzle (to him, in 2010 when he wrote it). I don't see this as an argument against the lead hypothesis in any way.

Re: your second point, one of the three studies in the parent article looks at city level crime in the 1920s/30s using city piping infrastructure (lead vs. iron) for test/control groups. The leaded fuel was a substantial source of increased lead levels but not the only one.

FWIW, it's not just lead in fuel, it's lead in paint (banned in the USA in 1978) that is a source.

My issue was that they stated very adamantly that there was no other explanations, when clearly they are.

Without stating which explanation is correct (which is impossible to prove). We can easily disprove the statement that no other explanations exist though.

Why would you expect a step effect from abortion legalization? It depends upon current criminals dying off or aging out, which happens gradually.

I'm no expert but I would think that if the mechanism is abortion, it's such an important decision that everyone who wants to get one will do so. So then ~20 years later all the aborted criminals vanish from the statistics and stay gone, leaving the other criminals to draw their own stats.

I'm not saying abortion is the ONLY factor, just that if it is, you'd see a step (or sigmoid) in the crime data and then that's it. As in there's a constant density of abortion sensitive criminals until they get aborted.

Similarly if abortion became illegal again, you'd see a step the other way. I'm not familiar with it, but I've heard it's gotten very hard in some places in the US to get an abortion.

Yeah there can be multiple explanations and even "anti-explanations". Things which should lead to increased crime but whose effects were swamped by other things.

Further data supporting your point: http://www.tylervigen.com/spurious-correlations

The abortion hypothesis is a different explanation, but it's not necessarily a better one. The proposed mechanism for abortion is that mothers who will give birth to future criminals are more likely to get abortions than mothers who will not give birth to future criminals, which seems vaguely plausible, but it's a more indirect effect than the known effects of lead exposure on brain development.

The lead mechanism is also easier to validate. Simply correlating the drop in crime with Roe v. Wade plus 20 years isn't enough--you also have to show some evidence which mothers and families demographically tend to produce more criminal children, and that these same mothers and families disproportionately chose abortion in greater rates after Roe v. Wade.

The proposed mechanism for abortion is that mothers who will give birth to future criminals are more likely to get abortions than mothers who will not give birth to future criminals

I don't think that's a correct explanation of their position.

Instead, children born who would have been aborted if it were legally available are more likely to be born into environments that lead to increased propensity to criminal behavior: poverty, no father figure, poor supervision, etc.

This is really one of the fundamental problems with the social sciences. So many studies in the social sciences take some spin on:

- 1) Observe correlation in sample.

- 2) Propose explanation for correlation

- 3) Take new sample.

- 4) See correlation still holds, therefore propose that explanation is the reason.

Of course the thing that should be clear in that process is that the explanation is irrelevant. The explanation could well be 'because 1+1=3.' There's an insufficient amount of attention directed towards falsification, prediction, and experimentation that's more than 'toy studies' or abstractly related. In many cases there are reasons for the lack of these processes (ethical concerns, time constraints, unavailability of an appropriate sample, etc) but those reasons do not change the fact that without these processes, the 'science' provided by the above sort of logic is not science - it's just plain old fashioned speculation in a fancy suit.

Nor is it an incompatible one.

The sprinkler being on may be getting the grass wet. But the sprinkler being on does not mean that it isn't raining.

It could be both, and that's when you have to do things like look at the crime rate in countries that banned leaded gasoline but didn't legalize abortion, or vice versa.

> Did not freakanomics come up with a famous (and to me more convincing) argument that it legalized abortion was the reason for the drop in crime? At they very least it dispels the arguments we don't have a better explanation and doesn't even mention it.

There was a bug in Donohue and Levitt's code which, combined with other factors, makes the effect go away, supposedly: https://www.economist.com/finance-and-economics/2005/12/01/o...

The legalised abortion argument has several holes in it, the big ones being:

- why did the crime rates simultaneously drop in states where abortion was already legal before Roe v Wade?

- why did crime rates have a similar drop in similar time frames in other countries regardless of the legality of abortion?

There is a very strong correlation between the banning of leaded petrol and reduction in crime rates around the world.

We have a good case study since Ireland legalized abortion way later other countries, we only have to wait 20 years and see.

Not only that but Flint, Michigan and some other communities have tons of kids with huge quantities of lead in their blood.

Reuters has been doing incredible investigative journalism: https://www.reuters.com/investigates/special-report/usa-lead...

If memory serves, the Freakonomics analysis looked at that?

A wide variety of factors contributed to the decline in crime. The world is complicated. The interesting thing about the lead theory is that research has found effects far larger than anyone would have expected intuitively.

The abortion theory makes intuitive sense, but as far as I know it hasn't been studied as rigorously.

Kevin Drum discusses this in his piece that popularized the lead-crime hypothesis in 2016[1]. Some of the research[2] into the lead-crime hypothesis was inspired by the abortion-crime hypothesis.

[1] https://www.motherjones.com/environment/2016/02/lead-exposur...

[2] http://www.nber.org/papers/w13097

> Did not freakanomics come up with a famous (and to me more convincing) argument that it legalized abortion was the reason for the drop in crime? At they very least it dispels the arguments we don't have a better explanation and doesn't even mention it.

It isn't a better one than lead. It was one of many correlated events. It was an interesting theory when it came out, but I don't think anyone takes the abortion argument seriously today since both abortion rates and crime rates have fallen together for nearly 40 years. Even when freakonomics came out, I remember my economics professor saying it was used to sell books.

Also, if the freakonomics theory was valid, the legalization and widespread use of birth control ( which prevented far more pregnancies and births ), not abortion, should be getting the credit. You are comparing an ocean ( birth control ) with a small pond ( abortion ).

The abortion theory is pretty much debunked now. That's why you don't hear about it anymore.

It's most likely a confluence of events that has led to drop in crime rates. Birth control, less lead, more TV/internet/etc, longer education period and changes in the law or prosecutions. At the end of the day, nobody really knows what caused the decline in crime for certain. Abortion sells a lot of books and gets a lot of media support/press, but the continuing decline of both abortion rates and crime rates seems to indicate that abortion isn't the cause.

It's not a particularly convincing argument when you look at other countries. The lead hypothesis, on the other hand, holds up remarkably well.

I can't find it now but I read something by a lead researcher that said the abortion effect is real but that the lead one is more predictive.

Russia/Former Soviet Union is an interesting outlier, because abortion has been legal there since at least the 1920s(with an almost 20-year gap imposed by Stalin).

There are other possible contributing factors, such as the decrease in testosterone, or the increase in obesity.

The obesity rate only really accelerated sometime later.

The obesity rate accelerated when the US government started giving nutrition advice based on the diet heart hypothesis (which is wrong) and advised everyone to cut out saturated fat and eat mostly carbohydrates. It's a global experiment that has gone awfully wrong.

Legalizing previously criminal activities does tend to decrease crime, by definition.

My point for the downvoters is that if something like abortion is inherently a crime, and legalizing it greatly increases the incidence of abortions, then it is false to claim the legalization of abortion reduces crime. For example, a large number of people (Catholics) consider abortion to be murder. If true, then the legalization of abortion has caused our murder rates to sky rocket.

And changes in level of enforcement.

Another possibly large factor is that the crack epidemic (and all of its auxiliary crime - property theft, gang violence) started to die down

per-capita violent crime rate was basically flat in the 20 years leading to 1994, so I don't see how it could have been related to that.

We actually have dozens of competing explanations for the crime rate decreases. Everyone and their uncle claims it's because of that thing they talked about all along!

Which is why it's important to look at actual data and try to keep an open mind. This stuff is complicated!

Half of Mexican children suffer from lead poisoning.


And we know there is a lot of violent crime in Mexico

Violent crime is Mexico is rather a consequence of cartel activity. Which has nothing to do with lead.

Or cartel activity has been developed to this level in Mexico, because people are more prone to make such activities there. Which can be caused by lead exposure. So "nothing to do with lead" isn't a strong hypothesis.

No, because people are poor and dealing drugs illegally is a big money maker. There is no need to involve lead to explain typical supply and demand mechanisms.

why is it so easy for you to rule that out? there are cartels in other countries, but mexico's are exceptionally, brutally violent

Suppose lead were to disappear from the earth tomorrow. It seems unlikely that it would have any effect on the Mexican cartel ecosystem.

The ecosystem is driven by demand from the US, and Mexico has the supply. The brutality is a consequence of a power struggle to control those resources.

> It seems unlikely that it would have any effect on the Mexican cartel ecosystem.

How can you on the one hand so easily dismiss the evidence that lead causes violence, which is backed up by rigorous statistical analysis and medical evidence, and on the other hand assert so surely that you know the answer?

If you were consistent, surely you'd apply skepticism to your own explanations as well.

The fact that lead causes violence isn't in question.

Violence is caused by multiple factors. One additional factor is the billions of dollars to be made preparing and running drugs from Mexico to the US.

My assertion is that if lead were removed as a factor, this would not negate the other cause.

But is all that violence actually necessary for cartels to profit? Some of it probably is, but all? There are many organized crime syndicates around the world, and they usually are involved in drug trade - but rarely you do see such open and extreme violence as in Mexico, including mass targeting of civilians (which is usually considered bad for business everywhere).

The war on drugs perpetrated by US forces is brutally violent as well, with cops armed like SWAT forces and forgoing the castle doctrine. This is all a consequence of useless escalation.

One of the most dangerous forms of lead is Tetraethyllead, because of how fat soluble it is. It's been banned in nearly every country in the world because it moves through the environment at an alarming rate. One company in the world still manufactures it, and they're based in the UK[0].

They're entirely aware that they're killing people and have openly said in management meetings that they won't stop manufacturing the product until government regulation forces them to.

Mind you, lead levels don't only increase in the country the chemical is used; it moves through entire ecosystems and across oceans. Lead levels don't fall to below dangerous levels for decades. This isn't just poisoning the people nearby; it's poisoning the entire world in small, insidious ways. And chemical companies are profiting from that. The margin they're selling TEL for would make government contractors cry.

And to top it off, they have virtually no quality program surrounding their products because they don't need one; all of their deals are done with backroom handshakes and agreeing to take the blame if an issue arises. Their company is built around the idea that it actually costs less to just say "Yeah, we're terrible people, fine us" than to actually try and comply with government regulation. They've repeatedly been caught in corruption and environmental probes, and have changed their names in the states and in the UK multiple times. They were literally caught trying to bribe their way into selling TEL in Iran. [1]

[0]: https://www.independent.co.uk/environment/leaded-petrol-alge...

[1]: https://www.sfo.gov.uk/2014/08/04/four-sentenced-role-innosp...

[1]: https://www.sfo.gov.uk/cases/innospec-ltd/

Leaded gasoline is still used in aviation, so in fact it’s not banned in every country of the world but Algeria?

Article is pretty low quality.

Note that most big passenger jets and such use kerosene, which is unleaded. In terms of leaded avgas, it's the smaller planes you've got to worry about.

The small old planes - typically hobbyist classic planes.

This is something to consider if you're buying a house, and are thinking of having kids. I wouldn't do very near to a airport where they fly planes that use leaded gas. The airport near me definitely does.

Is there any data out there to suggest that people living near airports that use leaded gasoline have high levels of lead in their blood?

It may be hard to come by, because 100LL(low lead avgas) is used only in piston engine aircraft and airports where these make the majority of traffic are usually in sparsely populated areas.

In places where airports are close to residences, the houses will typically be older and poorer. Which may mean they have other sources of lead - e.g. old paint.

Counterpoint would be some of the hobbyist airports. Some are in fairly wealthy suburban areas; some even have communities where homes will have hangars as well as garages.

There's a small airfield near here; 20 years ago it was surrounded with orange groves and an old defense contractor plant, and now they're putting in $800,000 McMansions less than 1km away.

There is data that says they have higher levels of lead [1]. About 4% higher than normal in children living within 500 m of a general aviation airport, dropping off with distance to insignificance at around 1000 m.

Note the the linked study did not consider wind patterns. Other studies cited in that one suggest that wind matters a lot, with someone downwind by a given distance getting a higher exposure than someone upwind the same distance.


I just grabbed an article that had a few sources to dig further if someone so chose. I learned about it through working in the industry.

I thought aviation gas was the primary reason that this is still around?

It’s definitely the only reason leaded fuel is still being burned.

No one has been able to find a practical replacement anti-knock compound, and apparently it’s been decided that the safety tradeoff is worth it (slightly poisoning the atmosphere vs. risk of in-flight engine failures).

There are a couple of companies working on a high-octane unleaded aviation fuel. The FAA PAFI program has largely fallen apart (my interpretation of what’s going on), but there seems to be some hope that GAMI’s G100UL (unleaded) may be workable as a drop-in replacement for today’s 100LL (“low lead” or “avgas”) and a lesser chance (again, IMO) of Swift’s fuel being viable.

G100UL is flying in some experimental aircraft today. (These include originally factory-built airplanes/engines converted to experimental use for the purpose of this testing.)

It’s probably 5+ years away in the very best case, as there’s a science/engineering problem to clear, but then an even larger regulatory hurdle remaining to clear, as the majority of avgas sold today is sold for airplanes only certified to run on 100LL, so there’s a certification change needed at some level. If that doesn’t apply to the whole fleet, it’s a logistics nightmare for airport fuel vendors.

Disclaimer: I casually know one of the principals at GAMI and have visited their test lab. I have no financial connection to them, however. I want them (or anyone else with an all-fleet solution) to succeed so that I can stop burning leaded avgas.

Swift also has 94UL which I believe all the Cirrus aircraft are certified for and I imagine most of the other high performance turbos could get an STC for. There's also the mogas STCs if we could drop the stupid ethanol corn subsidy. Personally I'm currently working on an EAB that will run E10 without issue because I'm so sick of the 100LL shit. There's a LOT of lead in 100LL (despite the name) and aircraft operations naturally expose you to a lot of it.

I mentioned Swift as well, but don’t think they have as good a chance to be an all-fleet fuel.

The Cirrus factory turbos are low compression engines (7.5:1). That gives a greater margin against detonation (at the cost of efficiency). That won’t extend to 8.5:1 compression, big-bore engines near as easily, whether turbo or normally aspirated. (This also means that I doubt it will work in the Tornado Alley turbo-normalized Cirrus.)

I too want to get the lead out of my life, especially since my kids fly in the airplane and are going to have exposure to it incidentally, even as I try to minimize it. It may well end being faster to just make more money and switch to Jet-A than to wait for a viable unleaded fuel to take over the market.

AFAIU 94 is about what you get if you remove the lead from 100LL.

Here's a recent article about the PAFI program: https://www.avweb.com/blogs/insider/Unleaded-Avgas-All-on-th...

There's also no one spending money getting replacement engines that don't need lead rated.

Like if you wanted to make a safety tradeoff you'd just ban general aviation (Imagine, they poison everyone a little bit, by taking pretty high personal risks).

That's going to be a no-go with the current wildfire situation, full stop. GA is actually pretty important and the US has enjoyed a lot of benefits from having a strong GA sector. Keep in mind that the US trains the lions share of the world's pilots because in the rest of the world it's either too expensive or too restrictive (many governments don't like the idea of people having access to airplanes). Either way though, I'm going to make you defend the personal risk statement as ground fatalities from GA accidents are exceedingly rare by any reasonable metric.

There is a lot of money going into replacement engines but they're mostly diesel since the most dominant fuel in aviation is Jet-A (essentially diesel/kerosene). These have found some success in Europe where 100LL is much more expensive as the operating costs of the diesels is much greater given their complexity, maintenance needs, and initial acquisition costs.

Indeed. In addition to fire fighting and pilot training, avgas burning aircraft provide critical transport in rural areas and a portion of the crop-dusting fleet is piston-powered.

Many more people are killed by dog bites in America than ground GA fatalities (turbine and piston combined). I’d no sooner make a safety argument to ban dogs than piston airplanes.

I was talking about the people in the plane exposing themselves to risk by flying, not ground fatalities, so uh? I wonder how "high personal risks" would lead to the misunderstanding.

It looks like crashes result in about 300 annual deaths (of people on the planes) and dog bites 20 or 30.

It seems that flying in a small plane is only somewhat more dangerous than driving the similar distance. But driving isn't really safe in the US either.

Personal risks that overwhelmingly affect only the people engaged in the risk are things that most people accept as the participants’ business. Motorcycles, fatty foods, swimming, and many others fit this category.

It didn’t occur to me (or seemingly Wild182) that you were suggesting banning an activity that was risky essentially solely to the participants in that activity. Being worried about ground fatalities of non-participant is something that makes sense, so that was the line of reasoning I thought you were suggesting. It was my mistake.

On a per-mile basis, light aircraft are approximately as safe/dangerous as motorcycles. That’s the “all causes” rate for both. Both activities have means to substantially reduce the risk versus the “all causes”. On a cycle, wear a helmet, drive within your limits, don’t drink and ride. In an airplane, don’t run out of gas, don’t fly into thunderstorms, don’t fly in clouds if you’re not instrument rated and current.

I thought "personal" meant that it only affected the people engaged in the risk, so there you go.

I guess "individual" would follow your understanding somewhat better?

Your words were clear. The mistake was mine.

I misread, making insufficient allowance for the concern to regulate risk taking by others.

The US is one of the safest places in the world to drive, and certainly in the same class as most developed countries. Is it the risk to individuals you object to, or the environmental cost? Which matters more, lead in fuel or the burning of fuel itself? Should we just go ahead and ban all combustion engines? That would at least be fair across the transportation sector.

Microprocessor production is toxic. Should we ban microprocessors? Dry cleaning is notorious. Should we ban dry cleaning? Gasoline is toxic in all forms. Should we ban gasoline? Batteries are almost always toxic. Should we ban batteries? Or maybe we should just let the EPA and similar government bodies regulate this, along with the courts, which means we’re all good today.

So better than chaos is an accomplishment? There are quite a lot of people living in countries with ~½ the road fatalities per mile driven, which is quite the delta.

This is something truly horrible, thanks for sharing it here.

I couldn't find any mention of Iran in the references. Did you mean "Indonesia and Iraq"?

Yes; meant to type Iraq, must have been autocorrected by my phone. I can't edit the comment now unfortunately. Otherwise I'd also clarify that I meant "Banned for automobile use". The remaining use of TEL only accounts for a fraction of what was being pumped into the environment when it was being used by cars.

Centralize gains, distribute losses.

A was very skeptical when I saw the headline. Then I read the article. The evidence coming from these 3 studies looks quite compelling I have to say. Next I googled: “Countries That Still Use Leaded Gasoline”, and I got:

Rank Location 1 Algeria 2 Iraq 3 Yemen 4 Myanmar 5 North Korea 6 Afghanistan

From https://www.worldatlas.com/articles/countries-that-still-use...

Also I found this: https://www.motherjones.com/kevin-drum/2016/12/prediction-te...

Very interesting indeed.

> Rank Location 1 Algeria 2 Iraq 3 Yemen 4 Myanmar 5 North Korea 6 Afghanistan

I am hoping you are not attributing violence and instability in some of these countries to lead based gasoline. Sure, there may be correlation, but these places are centuries old. There are many factors like culture, religiosity, socio-economic status , history, contemporary culture, so on and so forth.

No I’m not. I still find it to be an interesting correlation worthwhile for further examination. Would you rule it out entirely?

Before there were studies like the ones mentioned in the article people wouldn't believe it for cities like Flint in the states neither. I’m still not 100% convinced that there is causation. But if those studies are no fakes and hold up for repetition then I’d argue that there is some truth behind the theory

> Would you rule it out entirely?

Yes, unless you have a secret way of ruling out the other much more likely factors (i.e what GP mentioned).

You could argue that those countries still use leaded gasoline because the political turmoil/violence within them makes folks prefer the cheaper, easier fuel to produce.

Is it cheaper or easier to produce? The industrial process is difficult and hazardous. An alternative anti-knock agent is ethanol, which you can make at home. Originally, leaded gasoline was pushed by GM because they held the patents.

Ethanol production competes with citizens for food (how many of those countries using leaded gas have experienced famines recently?). Adding it to gasoline results in a fuel with ~30% less energy per unit, so you'd have to produce more gasoline to get an equivalent amount of energy.


I've read a study (can't find the link, sorry) comparing the cost of various ways of boosting the octane rating. Of all the alternatives (TEL, aromatics, alcohols, ethers, MMT, etc.) TEL was the cheapest.

I wonder what fraction of TEL consumption worldwide is due to aviation vs. these few remaining countries that use it in motor gasoline?

Can things have multi-factor causes?

It seems plausible that high environmental lead levels contribute (with at least a small effect size) to violence and crime.

If a lead-free environment is already violent and insecure, would you expect adding environmental lead to make it less violent, more violent, or the same?

Since their use of fossil fuels is significantly lower than European countries it's not a direct comparison, but an interesting situation.

Lead affects impulse control and could be a factor in certain civil phenomena. It's easier to whip up a mob when there's a lot of lead poisoning.

That's a stretch. It's just as easy to say that national instability leads to both civil war and lack of modern technology like unleqded gasoline.

Yeah, which is why the data is backed up by multiple panel analyses that actually make the argument for causation. The US data shows that crime rates rose like clockwork approximately ~20 years after leaded gasoline is used en masse, and drops ~20 years after it was banned.

Different states introduced and subsequently banned leaded gasoline on different schedules, so this was a 'natural' experiment, unless you can think of some other causative factor that precisely explains the timing of the rise and fall of crime.

I don't understand this content-free 'correlation does not equal causation' argument.

Sure, in the absence of other evidence and a mechanism of action, we should have healthy skepticism, but it's known how lead affects brain development, particularly how it screws up development of the frontal cortex, lowering both intelligence and social inhibition.

Re natural experiment: what about the water pipes? Were they exchanged as well? I don’t think you can see this as natural experiment unless other factors are equal

TFA discusses a natural experiment with water pipes. Cities near lead production centers tend to have lead pipes, so they compared cities with that characteristic and acidic water (which leaches lead into the water) and such cities without acidic water. The study found a strong effect.

Yeah, which is why the data is backed up by multiple panel analyses that actually make the argument for causation. The US data shows that crime rates rose like clockwork approximately ~20 years after leaded gasoline is used en masse, and drops ~20 years after it was banned.

Did they also account for changes in how crime rates are reported over time?

One would have to account for hundreds of different variables before you could ever conclusively prove a connection between lead and crime.

It would be impossible to 100% conclusively and with absolute precision determine the exact connection between the two. That doesn't mean it's not the best available theory at the moment, that fits the most data. There are international, interstate, and even local level analysis all pointing to the same thing. There are longitudinal studies on children pointing to the same thing. And there are established and direct casual mechanisms in the brain biology that explain it. So what does waving a hand and saying "Nah nah can't prove it" do? By your standards do we have zero knowledge on all sociological matters, since it's impossible to design and implement a perfectly controlled study?

>Did they also account for changes in how crime rates are reported over time?

The Bureau of Justice Statistics conducts a yearly survey asking people about the crimes they were a victim of in the past year regardless if the crimes were reported. The Bureau of Justice survey shows a much more dramatic reduction in crime than if you just look at reported crimes.


>Using the FBI numbers, the violent crime rate fell 48% between 1993 and 2016. Using the BJS data, the rate fell 74% during that span.

Ahh yes, lets forget the fact that the US went into what were at the time actually Stable countries, and blame lead.


It's been done before by people with more credibility than a message board user.

That's an interesting graph. What happened after 1990? Is the period after 1990 considered an outlier or is there another explanation?

Not to mention that a society with more violence/unrest (for whatever reason) may be less likely to have a government with a functioning regulatory system, i.e. unrest may cause gasoline to remain leaded rather than the other way around.

I don't know how much of a well know fact this is here, but lead pipes influence over brain and behaviour has long been considered a possible factor among the ones that caused the fall of the Roman empire.

The effect of lead residuals on brain is pretty well known..

I'd think you'd also need to see the rate of leaded gas burning per area. Fewer people drive cars in some of those countries, and there are fewer cars per square area.

> The evidence coming from these 3 studies looks quite compelling I have to say.

I like the trick to select a control group by acidity in the water.

> Rank Location 1 Algeria 2 Iraq 3 Yemen 4 Myanmar 5 North Korea 6 Afghanistan

So your point is?

Makes sense.

"Lead exposure in childhood linked to lower IQ, lower status jobs, as adults" https://www.sciencedaily.com/releases/2017/03/170328145300.h... Which also correlates with criminality.

I was going to ask why the cited studies apparently didn't consider the phaseout of lead-based paint. But then I realized that the first study relies on data preceding the lead-paint problem, in that lead paint wasn't used as much indoors then, and arguably wasn't in bad shape. The third study just considers lead levels and interventions, and so subjects were exposed to multiple sources.

The second study[0] finds that distance to roads correlates with lead exposure. They do discuss relative contribution from multiple sources: flaking indoor lead-based paint, lead in soil around foundations (from maintenance of outdoor lead-based paint), and roadside lead.

0) https://sci-hub.tw/https://www.nber.org/papers/w23392

And of course, it's the gift that keeps on giving!


This 2016 Mother Jones article is a good treatment of this hypothesis:


I may have missed something but it looks like Europe is not taken into consideration in these studies. For example in France lead in gasoline was not banned until the 90’s, and the violent crime statistics doesn’t look very correlated.

Crime lags around 20 years behind lead levels.

Young people burning cars in Paris suburbs around 2010 may not be technically violent crime but it's pretty weird and special. And also in decline:


I don’t know about this particular study, but much of the strongest evidence for the lead hypothesis comes from comparing when different countries phased in/out lead and how their crime rates were affected.

Does anyone have any resources with concrete numbers about how much lead exposure is too much? I just moved into a new house that has a lead service pipe in from the city, and it concerns me. In addition, the federal action level is 15ppb, and my utility's water report last year had it at 8ppb, which seems kind of close.

I know there's no known level of safe lead exposure, but I don't have a good sense from a cost benefit perspective of how much to do to try to lower my exposure.

Water filters are cheap and effective and make the water taste better anyway. I think most people's exposure is from eating lead paint and breathing fumes and particulates (also from paint -previously from gasoline engines). None the less, the US is visibly decaying enough I always drink filtered water (google "big berkey").

Kevin drum has written a bunch on city lead piping and how it is much less of a problem because the pipes are typically internally coated.

Without wanting to sound too snarky, wasn't this already pretty well-established knowledge? [0]

Imho one of the more infamous and recent examples of human hubris. Who knows what we are downplaying right now, that might end up really messing us up in another couple of decades? Only time will tell.

[0] https://en.wikipedia.org/wiki/Tetraethyllead#Controversy_and...

I thought so, and I wish it were. But look at the threads here, and everyone who feels that they can just say "crack epidemic" and believe it is providing the same insight into the situation as scientific study.

That is poisons people is well-established knowledge. That it affects brain function, as well.

It's the correlation with crime specifically that is the interesting part.

In Elizabethan England, didn’t a lot of women wear lead based makeup? I’d be interested in seeing how that affected crime rates or other metrics, if that data were available.

Could it be that there are other pollutants that could cause similar issues?

Some countries have banned lead even before the US, but crime rates are still growing(Brazil, for instance). Poverty alone does not explain this. There are countries just as poor (or more), with corrupt police forces and that do not have the same issue with violence.

There are probably dozens of factors. Some societal, some environmental. It's not like being exposed to lead makes everybody into a criminal either.

Recent study showing that air pollution can impact intelligence equivalent to the loss of a year of education.


It's very hard to separate the effects of airborne lead from other air pollution, since they tend to exist in the same places.

I wouldn't be surprised if the lead is the cause of both.

A year of education is a useless metric. Staying one more year in college does not make you smarter. Junk article.

> Some countries have banned lead even before the US, but crime rates are still growing(Brazil, for instance).


Kevin Drum is an absolute shill for LCH. There was a study in New Zealand that, if you actually read the paper, unambiguously fails to support the LCH. What was the headline for the article he wrote about it? "New Zealand Study Provides More Support for Lead-Crime Hypothesis"


Maybe it has to do with the drug cartels or being in war zones? I don't think the study was trying to say that lead is the only factor in crime.

"single variable reductions" used to explain complex societal changes are hardly convincing.

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