Why Lead Exposure Is to Blame for Violent Crime

A couple weeks ago, I noted a new UPenn study claiming increased cell phone use was to thank for the mid-1990s crime drop. The idea seemed on par with the much-ballyhooed, Malcolm Gladwell-endorsed “broken windows” theory: admittedly correlated with concurrent decreases in criminal activity, but not sufficient to fully explain them. In the current issue of Mother Jones, Kevin Drum argues persuasively that a new (but old) culprit better helps explain urban crime in the second half of the 20th century: lead. When lead gasoline emissions rose in the 40, 50s, crime in the 60s, 70s, and 80s followed near-identical spikes. “Toddlers who ingested high levels of lead in the ’40s and ’50s really were more likely to become violent criminals in the ’60s, ’70s, and ’80s,” Drum writes. Which also helps explain the boom in urban crime: during the lead bonanza, murder rates were higher in cities than elsewhere, most likely because city centers contained more cars. Now that lead emissions aren’t what they use to be, following the 1996 ban on leaded gasoline, per capita murder rates are no higher in cities than anywhere else.

So why is lead to blame?

High exposure to lead during childhood [is] linked to a permanent loss of gray matter in the prefrontal cortex—a part of the brain associated with aggression control as well as what psychologists call “executive functions”: emotional regulation, impulse control, attention, verbal reasoning, and mental flexibility.

Hence the violence. Though the problem isn’t as bad as it used to be, it’s still serious in urban environments, and Drum makes the case that $20 billion in lead removal, from soil and lead-painted windows, would generate $200 billion in savings from reduced crime and increased productivity.

So this is the choice before us: We can either attack crime at its root by getting rid of the remaining lead in our environment, or we can continue our current policy of waiting 20 years and then locking up all the lead-poisoned kids who have turned into criminals.

[Mother Jones]