Kicking. Squealing.
A lot has been made of Kevin Drum’s article on lead exposure and crime. Much has also been made of research showing that boys and girls are entering puberty at earlier ages.
The usual caveats apply, but there is a connection between lead exposure and delayed puberty, and it would be interesting to investigate how much of a factor the decrease in environmental lead has led to the decrease in age at puberty onset. It could be entirely possible, probable in fact, that the lead exposure vector runs in the opposite direction of the other common explanations for earlier puberty – other chemicals in the environment, absent fathers, urbanism, obesity/diet, and stress.
The National Institutes of Health conducted research on over 700 girls:
The researchers analyzed data on blood drawn from more than 700 girls ages 6 to 11. They found that girls with elevated levels of lead (at or above five micrograms of lead per deciliter of blood) were 75 percent less likely than girls with low levels of lead to have key adolescent hormones at levels that are associated with the beginning of puberty. In girls with elevated levels of both lead and cadmium, this pattern was even more pronounced.
A write up of research published in the journal Pediatrics discusses a link between lead exposure in Russian boys and delayed puberty onset:
In the current study, researchers followed more than 400 boys between the ages of 8 and 9 years over the course of three years. At the start of the study, over one quarter (28%) of the boys had levels of lead that were half of the threshold indicated by the CDC, or 5 micrograms/dL. By the time they had reached the age of 12 years, 90% of them had at least one developmental sign (i.e., changes in voice, body hair) indicating that they were entering puberty. However, boys who had elevated levels of lead were less likely to display these signs, with delays averaging 6 to 8 months. [emphasis added]
There has been an uptick in recent years of research of the link between lead and puberty: girls in South Africa, boys and girls in Egypt, white, black, and Hispanic American girls, and in Swiss female mice. As always, this is a nature/nurture issue. Puberty timing is 50-80% heritable.
The relationship between delayed puberty and elevated lead levels seems pretty well established to me. Lead and crime? Well, definite maybe. The problem is all the confounding variables. Nonetheless, lead is a persistent element, both in the body and in the environment (half-life in humans is approximately 32 years), and it has so many toxicities, that it probably makes sense to get rid of as much of it as possible. If that reduces crime, wonderful. But even if it doesn’t, it’s still a good thing to do.
The crime/lead story seems to be another instance of the establishment building elaborate theories to explain away black crime. In the 40s and 50s, blacks moved into northern industrial cities, but crime didn’t spike as much because of forced segregation and more, uh, assertive policing by the white population. After desegregation and the adoption of Malcolm X style racial grievance politics within the black community, these northern cities were ripe for the violent predations of their black populations.
I live in a midwest industrial city with a large black population. When I drive down Martin Luther King Blvd, I see shops with bars over the windows and big, heavy steal rolling doors that go up at noon and down again just before dark. Gas stations and mini-marts with thick bullet proof glass and little sliding trays used to complete your transactions. Presumably, fifty years ago these shops (or the ones that existed in their place) wouldn’t have had these precautions. They would have been soft targets with more available wealth. I stick-up mans wet dreams, right? These cities had much larger white populations then, people less aware of and worried about black criminality. Fast forward to today. De facto segregation has been established, the shops are armored up (or don’t exist), people (especially white people) know where not to be in any given city. So, being a criminal is just harder today than it was in the 60s. This all seems pretty obvious…