Here’s a Lead-Crime Study That’s Not About Crime

Today brings to my attention a new lead-crime study. What makes it interesting is that (a) it’s not about lead and crime, and (b) its results are basically negative, which makes me pretty happy.

So what is it about? Previous studies have demonstrated that shooting ranges contain a lot of lead dust and that this produces high blood lead levels in people who shoot frequently. A team of South African researchers took this a step further and measured the BLLs of shooters at several ranges in Gauteng and compared them to BLLs of archers at nearby archery ranges. Then they checked to see if there was any correlation not with crime, but with levels of aggression.

Now, this is a bit sketchy right from the start since there’s no way of knowing if shooters and archers have similar personalities in the absence of lead. The archers, for example, turn out to be substantially more educated, which could account for any differences all by itself. But let’s put that aside. The study finds that shooters have an average BLL of 8.5 μl/dl while archers have an average BLL of 2.7—a sizeable difference, though neither score is wildly high. Here are the basic results for aggression:

The authors measure aggression using the Buss-Perry Aggression Questionnaire, which is a widely-used survey instrument with 29 items. You can take it here if you’re curious about it. It’s worth noting that I filled out the survey and scored 56. The average for men is around 70-80. So we’re talking about pretty modest aggressiveness scores here for both the shooters and the archers.

That said, the authors claim that the difference between 54.7 and 47.3 is statistically significant. However, on a normalized basis it’s the difference between 16 percent and 22 percent, where the average is about 40 percent. It’s a very small difference in practical terms. Here’s what the paper says:

All factors were weakly yet positively correlated with BLLs. However, only anger was significantly correlated. In the regression analyses, the findings show that hostility scores were significantly elevated if lead exposure levels were 10 μg/dL. However, the associations with the other sub-scales (Physical aggression, Verbal aggression, and Anger) were not statistically significant in this study. Aggression and anti-social behavior in adolescence and children have been associated with elevated lead levels and lead exposure early in childhood. Ecological studies have pointed to an association between early childhood exposure and crime rates. Therefore, despite the findings from this study, the relationship between lead exposure and aggressive behavior in adults should be studied further.

This is what we should expect. Lead exposure is dangerous for infants and toddlers, but at moderate levels has little effect on adults. Anything below 10 μg/dl shouldn’t produce much difference, and in this study it didn’t. Hostility was somewhat elevated above 10 μg/dl, and that was about it.

Given the limitations of this study, it’s not clear to me that its results are especially meaningful in any case. For what it’s worth, though, its conclusions are consistent with both the lead-crime theory and the Atrios Corollary—namely that if lead exposure leads to higher crime rates, it should also lead to higher levels of aggression and general assholishness. Anecdotally, this corollary seems to be true, but as with the main hypothesis you only see an effect on people who were exposed to lead at a young age. There’s not much effect from adult exposure at moderate levels.