Dr. Dan KillamFeb 3
Comparing historical hair samples from people from when they were babies to today, a new study finds a nearly 100-fold decrease in lead from samples after the EPA's crackdown on leaded gas. Regulation works and it saves lives!
https://arstechnica.com/science/2026/02/a-century-of-hair-samples-proves-leaded-gas-ban-worked/
Show threadDr. Dan KillamFeb 3
The study from Cerling et al. I saw Thure Cerling talk about his work when I was a grad student, fascinating stuff! https://www.pnas.org/doi/10.1073/pnas.2525498123
Show threadMartin Vermeer FCDFeb 3
@dantheclamman Nothing about environmental lead and crime, which appears to be a thing...
Show threadobscurestarFeb 3
@martinvermeer @dantheclamman Truthfully, this would be very hard data to draw any conclusions from. There are just too many other factors. For instance, the shift from mostly human manufacturing to mostly robotic manufacturing (which began happening at increasing scale post WWII) the stagnation of wages are going to drive crime. Also the CIA selling arms to Iran to buy drugs from Noriega to dump on US streets to increase crime as a way to attack minorities. Too many factors. Hard to isolate.
Show threadwyngmanFeb 3

@obscurestar @martinvermeer @dantheclamman Actually, the lead-crime correlation shows up across all industrialized societies in 20c. That the curves line up despite different countries industrializing and moving to automobiles at different times indicates that lead exposure was a major factor. It was not contained in the US, far from it.

I think the burden of proof is on those who suggest that what we know to be true about lead exposure for individuals and small groups of people somehow doesn't scale to large groups.

Show threadobscurestar
@tasket @martinvermeer @dantheclamman I don't at all doubt that lead, particularly tetraethyl lead isn't toxic and a contaminant on a massive scale (not to mention used for the stupidest pure greed reasons). Even the Romans knew that lead was bad news. Correlation across many industrialized nations can well constitute a smoking gun but correlation is not always causation. Just urging caution with blanket statements.
Feb 3 at 11:47pmWeb
Show threadDr. Dan KillamFeb 4
@obscurestar @tasket @martinvermeer Yes, caution is merited. A recent meta-analysis showed there probably is an association between lead exposure and crime, but the relationship is not cut-and-dry. It explains some of the variance, but there are other contingent factors or "confounders" at play, with kids exposed to high lead and also having greater socioeconomic need showing the biggest negative effect. The review authors point out many studies do not account for that and some other interactive effects. https://pmc.ncbi.nlm.nih.gov/articles/PMC10393136/#sec011
The association between lead exposure and crime: A systematic review

Prior research has demonstrated an association between lead exposure and criminal behavior at the population-level, however studies exploring the effect of lead exposure on criminal behavior at the individual-level have not been reviewed ...

PubMed Central (PMC)