Lead has many known neurological effects on the brain (regarding the development of the brain and nervous system) that lead to many deleterious health outcomes and negative outcomes in general. Including (but not limited to) lower IQ, higher rates of crime, higher blood pressure and higher rates of kidney damage, which have permanent, persistent effects (Stewart et al, 2007). Chronic lead exposure, too, can “also lead to decreased fertility, cataracts, nerve disorders, muscle and joint pain, and memory or concentration problems” (Sanders et al, 2009). Lead exposure in vitro, in infancy, and in childhood can also lead to “neuronal death” (Lidsky and Schneider, 2003). While epigenetic inheritance also plays a part (Sen et al, 2015). How do blacks and whites differ in exposure to lead? How much is the difference between the two races in America, and how much would it contribute to crime? On the other hand, China has high rates of lead exposure, but lower rates of crime, so how does this relationship play out with the lead-crime relationship overall? Are the Chinese an outlier or is there something else going on?
The effects of lead on the brain are well known, and numerous amounts of effort have been put into lowering levels of lead in America (Gould, 2009). Higher exposure to lead is also found in poorer, lower class communities (Hood, 2005). So since higher levels of lead exposure are found more often in lower-class communities, then blacks should have higher blood-lead levels than whites. This is what we find.
Blacks had a 27 percent higher concentration of lead in their tibia, while having significantly higher levels of blood lead, “likely because of sustained higher ongoing lead exposure over the decades” (Theppeang et al, 2008). Other data—coming out of Detroit—shows the same relationships (Haar et al, 1979; Talbot, Murphy, and Kuller, 1982; Lead poisoning in children under 6 jumped 28% in Detroit in 2016; also see Maqsood, Stanbury, and Miller, 2017) while lead levels in the water contribute to high levels of blood-lead in Flint, Michigan (Hanna-Attisha et al, 2016; Laidlaw et al, 2016). Cassidy-Bushrow et al (2017) also show that “The disproportionate burden of lead exposure is vertically transmitted (i.e., mother-to-child) to African-American children before they are born and persists into early childhood.”
Children exposed to lead have lower brain volumes as children, specifically in the ventrolateral prefrontal cortex, which is the same region of the brain that is impaired in antisocial and psychotic persons (Cecil et al, 2008). The community that was tested was well within the ‘safe’ range set by the CDC (Raine, 2014: 224), though the CDC says that there is no safe level of lead exposure. There is a large body of studies which show that there is no safe level of lead exposure (Needleman and Landrigan, 2004; Canfield, Jusko, and Kordas, 2005; Barret, 2008; Rossi, 2008; Abelsohn and Sanborn, 2010; Betts, 2012; Flora, Gupta, and Tiwari, 2012; Gidlow, 2015; Lanphear, 2015; Wani, Ara, and Usmani, 2015; Council on Environmental Health, 2016; Hanna-Attisha et al, 2016; Vorvolakos, Aresniou, and Samakouri, 2016; Lanphear, 2017). So the data is clear that there is absolutely no safe level of lead exposure, and even small effects can lead to deleterious outcomes.
Further, one brain study of 532 men who worked in a lead plant showed that those who had higher levels of lead in their bones had smaller brains, even after controlling for confounds like age and education (Stewart et al, 2008). Raine (2014: 224) writes:
The fact that the frontal cortex was particularly reduced is very interesting, given that this brain region is involved in violence. This lead effect was equivalent to five years of premature aging of the brain.
So we have good data that the parts of the brain that relate to violent tendencies are reduced in people exposed to more lead had the same smaller parts of the brain, indicating a relationship. But what about antisocial disorders? Are people with higher levels of lead in their blood more likely to be antisocial?
Needleman et al (1996) show that boys who had higher levels of lead in their blood had higher teacher ratings of aggressive and delinquent behavior, along with higher self-reported ratings of aggressive behavior. Even high blood-lead levels later in life is related to crime. One study in Yugoslavia showed that blood lead levels at age three had a stronger relationship with destructive behavior than did prenatal blood lead levels (Wasserman et al, 2008); with this same relationship being seen in America with high blood lead levels correlating with antisocial and aggressive behavior at age 7 and not age 2 (Chen et al 2007).
Nevin (2007) showed a strong relationship between preschool lead exposure and subsequent increases in criminal cases in America, Canada, Britain, France, Australia, Finland, West Germany, and New Zealand. Reyes (2007) also shows that crime increased quicker in states that saw a subsequent large decrease in lead levels, while variations in lead levels within cities correlating with variations in crime rates (Mielke and Zahran, 2012). Nevin (2000) showed a strong relationship between environmental lead levels from 1941 to 1986 and corresponding changes to violent crime twenty-three years later in the United States. Raine (2014: 226) writes (emphasis mine):
So, young children who are most vulnerable to lead absorption go on twenty-three years later to perpetrate adult violence. As lead levels rose throughout the 1950s, 1960s, and 1970s, so too did violence correspondingly rise in the 1970s, 1980s and 1990s. When lead levels fell in the late 1970s and early 1980s, so too did violence fall in the 1990s and the first decade of the twenty-first century. Changes in lead levels explained a full 91 percent of the variance in violent offending—an extremely strong relationship.
From international to national to state to city levels, the lead levels and violence curves match up almost exactly.
But does lead have a causal effect on crime? Due to the deleterious effects it has on the developing brain and nervous system, we should expect to find a relationship, and this relationship should become stronger with higher doses of lead. Fortunately, I am aware of one analysis, a sample that’s 90 percent black, which shows that with every 5 microgram increase in prenatal blood-lead levels, that there was a 40 percent higher risk of arrest (Wright et al, 2008). This makes sense with the deleterious developmental effects of lead; we are aware of how and why people with high levels of lead in their blood show similar brain scans/brain volume in certain parts of the brain in comparison to antisocial/violent people. So this is yet more suggestive evidence for a causal relationship.
Jennifer Doleac discusses three studies that show that blood-lead levels in America need to be addressed, since they are related strongly to negative health outcomes.Aizer and Curry (2017) show that “A one-unit increase in lead increased the probability of suspension from school by 6.4-9.3 percent and the probability of detention by 27-74 percent, though the latter applies only to boys.” They also show that children who live nearer to roads have higher blood-lead levels, since the soil near highways was contaminated decades ago with leaded gasoline. Fiegenbaum and Muller (2016) show that cities’ use of lead pipes increased murder rates between the years o921 and 1936. Finally, Billings and Schnepnel (2017: 4) show that their “results suggest that the effects of high levels of [lead] exposure on antisocial behavior can largely be reversed by intervention—children who test twice over the alert threshold exhibit similar outcomes as children with lower levels of [lead] exposure (BLL<5μg/dL).”
A relationship with lead exposure in vitro and arrests at adulthood. The sample was 90 percent black, with numerous controls. They found that prenatal and post-natal blood-lead exposure was associated with higher arrest rates, along with higher arrest rates for violent acts (Wright et al, 2008). To be specific, for every 5 microgram increase in prenatal blood-lead levels, there was a 40 percent greater risk for arrest. This is direct causal evidence for the lead-causes-crime hypothesis.
One study showed that in post-Katrina New Orleans, decreasing lead levels in the soil caused a subsequent decrease in blood lead levels in children (Mielke, Gonzales, and Powell, 2017). Sean Last argues that, while he believes that lead does contribute to crime, that the racial gaps have closed in the recent decades, therefore blood-lead levels cannot be a source of some of the variance in crime between blacks and whites, and even cites the CDC ‘lowering its “safe” values’ for lead, even though there is no such thing as a safe level of lead exposure (references cited above). White, Bonilha, and Ellis Jr., (2015) also show that minorities—blacks in particular—have higher rates of lead in their blood. Either way, Last seems to downplay large differences in lead exposure between whites and blacks at young ages, even though that’s when critical development of the mind/brain and other important functioning occurs. There is no safe level of lead exposure—pre- or post-natal—nor are there safe levels at adulthood. Even a small difference in blood lead levels would have some pretty large effects on criminal behavior.
Sean Last also writes that “Black children had a mean BLL which was 1 ug/dl higher than White children and that this BLL gap shrank to 0.9 ug/dl in samples taken between 2003 and 2006, and to 0.5 ug/dl in samples taken between 2007 and 2010.” Though, still, there are problems here too: “After adjustment, a 1 microgram per deciliter increase in average childhood blood lead level significantly predicts 0.06 (95% confidence interval [CI] = 0.01, 0.12) and 0.09 (95% CI = 0.03, 0.16) SD increases and a 0.37 (95% CI = 0.11, 0.64) point increase in adolescent impulsivity, anxiety or depression, and body mass index, respectively, following ordinary least squares regression. Results following matching and instrumental variable strategies are very similar” (Winter and Sampson, 2017).
Naysayers may point to China and how they have higher levels of blood-lead levels than America (two times higher), but lower rates of crime, some of the lowest in the world. The Hunan province in China has considerably lowered blood-lead levels in recent years, but they are still higher than developed countries (Qiu et al, 2015). One study even shows ridiculously high levels of lead in Chinese children “Results showed that mean blood lead level was 88.3 micro g/L for 3 – 5 year old children living in the cities in China and mean blood lead level of boys (91.1 micro g/L) was higher than that of girls (87.3 micro g/L). Twenty-nine point nine one per cent of the children’s blood lead level exceeded 100 micro g/L” (Qi et al, 2002), while Li et al (2014) found similar levels. Shanghai also has higher levels of blood lead than the rest of the developed world (Cao et al, 2014). Blood lead levels are also higher in Taizhou, China compared to other parts of the country—and the world (Gao et al, 2017). But blood lead levels are decreasing with time, but still higher than other developed countries (He, Wang, and Zhang, 2009).
Furthermore, Chinese women, compared to American women, had two times higher BLL (Wang et al, 2015). With transgenerational epigenetic inheritance playing a part in the inheritance of methylation DNA passed from mother to daughter then to grandchildren (Sen et al, 2015), this is a public health threat to Chinese women and their children. So just by going off of this data, the claim that China is a safe country should be called into question.
Reality seems to tell a different story. It seems that the true crime rate in China is covered up, especially the murder rate:
In Guangzhou, Dr Bakken’s research team found that 97.5 per cent of crime was not reported in the official statistics.
Of 2.5 million cases of crime, in 2015 the police commissioner reported 59,985 — exactly 15 less than his ‘target’ of 60,000, down from 90,000 at the start of his tenure in 2012.
The murder rate in China is around 10,000 per year according to official statistics, 25 per cent less than the rate in Australia per capita.
“I have the internal numbers from the beginning of the millennium, and in 2002 there were 52,500 murders in China,” he said.
Instead of 25 per cent less murder than Australia, Dr Bakken said the real figure was closer to 400 per cent more.”
Guangzhou, for instance, doesn’t keep data for crime committed by migrants, who commit 80 percent of the crime in this province. Out of 2.5 million crimes committed in Guangzhou, only 5,985 crimes were reported in their official statistics, which was 15 crimes away from their target of 6000. Weird… Either way, China doesn’t have a similar murder rate to Switzerland:
The murder rate in China does not equal that of Switzerland, as the Global Times claimed in 2015. It’s higher than anywhere in Europe and similar to that of the US.
China also ranks highly on the corruption index, higher than the US, which is more evidence indicative of a covered up crime rate. So this is good evidence that, contrary to the claims of people who would attempt to downplay the lead-crime relationship, that these effects are real and that they do matter in regard to crime and murder.
So it’s clear that we can’t trust the official Chinese crime stats since there much of their crime is not reported. Why should we trust crime stats from a corrupt government? The evidence is clear that China has a higher crime—and murder rate—than is seen on the Chinese books.
Lastly, effects of epigenetics can and do have a lasting effect on even the grandchildren of mothers exposed to lead while pregnant (Senut et al, 2012; Sen et al, 2015). Sen et al (2015) showed lead exposure during pregnancy affected the DNA methylation status of the fetal germ cells, which then lead to altered DNA methylation on dried blood spots in the grandchildren of the mother exposed to lead while pregnant.—though it’s indirect evidence. If this is true and holds in larger samples, then this could be big for criminological theory and could be a cause for higher rates of black crime (note: I am not claiming that lead exposure could account for all, or even most of the racial crime disparity. It does account for some, as can be seen by the data compiled here).
In conclusion, the relationship between lead exposure and crime is robust and replicated across many countries and cultures. No safe level of blood lead exists, even so-called trace amounts can have horrible developmental and life outcomes, which include higher rates of criminal activity. There is a clear relationship between lead increases/decreases in populations—even within cities—that then predict crime rates. Some may point to the Chinese as evidence against a strong relationship, though there is strong evidence that the Chinese do not report anywhere near all of their crime data. Epigenetic inheritance, too, can play a role here mostly regarding blacks since they’re more likely to be exposed to high levels of lead in the womb, their infancy, and childhood. This could also exacerbate crime rates, too. The evidence is clear that lead exposure leads to increased criminal activity, and that there is a strong relationship between blood lead levels and crime.
I think the evidence certainly points that way, but to nit-pick, wright et al., 2008 doesn’t provide “direct causal evidence” but rather indirect causal evidence, as it’s still a correlation, just over time periods. If x at time A is correlated with behaviour at time A+1 then it’s only really quasi causal evidence. I might have read it wrong though.
It’s weird to see an hereditarian claiming “it’s just a correlation”, wish to see that more often.
Thomas, you’re right, I’ll edit that. Though the claim becomes very strong since every 5 microgram increase in the womb predicts arrest rates. And remember that most of the hereditarian paradigm is built on mountains of correlations. With the other data on decreasing the lead supply leading to subsequent decreases in crime, that’s even more strong evidence.
TheBoredMan, I agree. Because hereditarians champion correlations as if they are causation; post hoc, ergo propter hoc.
what does “X causes Y” mean really?
rr might do a post on this. it may have many legitimate senses. not just one.
the billiards model isn’t subtle enough for all phenomena.
i swing my arm. the cue stick moves. the cue ball moves. the 3 ball falls in the pocket.
in The Critique of Pure Reason kant claimed that the idea of “cause and effect” was merely the human mind’s projecting “if…then” onto phenomena. things-in-themselves may have no cause and effect. so far as science is possible, phenomena must conform to laws of thought.
That X preceded Y. But I agree with you; what does it truly mean? Do mental events have causes?
There are no psychophsyical laws.
The Interaction Principle: Some mental events causally interact with some physical events
The Cause-Law Principle: Events related as cause and effect are covered by strict laws
The Anomalism Principle: There are no strict laws on the basis of which mental events can predict, explain, or be predicted or explained by other events
i think you meant “Y ALWAYS follows X”. the ALWAYS is the important part. why can’t it be 80% of the time?
my point is it’s not fair to criticize those who confuse correlation with causation unless one is clear in his own mind what he means by cause and effect.
maybe rr is just a late bloomer. there was another italian american on lion’s blog from the nyc area who claimed she retook the SAT and scored hundreds higher. but she was a she and claimed to be half irish.
rr might retake some IQ tests and find out he’s much smarter relative to his age group than he was. this might change his mind about IQ tests.
It’d take a lot to change my mind on IQ, but taking a test and scoring well surely is not one of them.
“””IQ and lead exposure”””
– How exactly does lead exposure influence IQ?
– MCV is used to look for the role of subtest g-loadings as a moderator of effect size.
– 16 studies are meta-analyzed.
– Aggregate vector correlation is 0.10 indicating no clear moderation from g.
– All study variation is due to sampling error.
That doesn’t contribute much as IQ is merely another correlate of crime rather than criminal behavior itself.
Likewise, the paper thats that a casual scenario to mental abilities in the abstract is consistent with the data.
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