Kevin Drum and the lead-crime connection

 

My favorite blogger, Kevin Drum, died recently from multiple myeloma. I started following Kevin when he blogged as “calpundit,” and through all his various iterations. I found his comments thoughtful, often provocative and grounded in data and evidence.

One of the most remarkable stories that Kevin blogged about was the connection between leaded gasoline and crime. He eventually summarized his findings in a Mother Jones article (link at the end):

“The biggest source of lead in the postwar era, it turns out, wasn’t paint. It was leaded gasoline. And if you chart the rise and fall of atmospheric lead caused by the rise and fall of leaded gasoline consumption, you get a pretty simple upside-down U: Lead emissions from tailpipes rose steadily from the early ’40s through the early ’70s, nearly quadrupling over that period. Then, as unleaded gasoline began to replace leaded gasoline, emissions plummeted.

“Intriguingly, violent crime rates followed the same upside-down U pattern. The only thing different was the time period: Crime rates rose dramatically in the ’60s through the ’80s, and then began dropping steadily starting in the early ’90s. The two curves looked eerily identical, but were offset by about 20 years.”

Indeed, a 2000 study found that lead emissions from automobiles explained 90% of the variation in violent crime in the US. And there’s more:

“During the ’70s and ’80s, the introduction of the catalytic converter, combined with increasingly stringent Environmental Protection Agency rules, steadily reduced the amount of leaded gasoline used in America, but Reyes discovered that this reduction wasn’t uniform. In fact, use of leaded gasoline varied widely among states . . . . If childhood lead exposure really did produce criminal behavior in adults, you’d expect that in states where consumption of leaded gasoline declined slowly, crime would decline slowly too. Conversely, in states where it declined quickly, crime would decline quickly.”

What about the rest of the world?

“ . . . lead data and crime data for Australia . . .  found a close match. Ditto for Canada. And Great Britain and Finland and France and Italy and New Zealand and West Germany. Every time, the two curves fit each other astonishingly well.”

No exceptions have been found. But correlation isn’t causation. How, exactly, does environmental lead drive crime? By poisoning brain development.

“Neurological research is demonstrating that lead’s effects are even more appalling, more permanent, and appear at far lower levels than we ever thought. For starters, it turns out that childhood lead exposure at nearly any level can seriously and permanently reduce IQ. Blood lead levels are measured in micrograms per deciliter, and levels once believed safe—65 μg/dL, then 25, then 15, then 10—are now known to cause serious damage. The EPA now says flatly that there is “no demonstrated safe concentration of lead in blood,” and it turns out that even levels under 10 μg/dL can reduce IQ by as much as seven points. An estimated 2.5 percent of children nationwide have lead levels above 5 μg/dL.”

And elevated lead exposure has negative effects on behavior:

“ . . . even moderately high levels of lead exposure are associated with aggressivity, impulsivity, ADHD, and lower IQ. And right there, you’ve practically defined the profile of a violent young offender.”

Drum is quick to point out that not every child with high lead levels grows up to be a criminal and lead levels don’t explain *all* crime.

“But there were plenty of kids already on the margin, and millions of those kids were pushed over the edge from being merely slow or disruptive to becoming part of a nationwide epidemic of violent crime. Once you understand that, it all becomes blindingly obvious. Of course massive lead exposure among children of the postwar era led to larger numbers of violent criminals in the ’60s and beyond. And of course when that lead was removed in the ’70s and ’80s, the children of that generation lost those artificially heightened violent tendencies.”

Much more at the link.

Drum wasn’t the only one to make the lead-crime connection, but he did much to promote the hypothesis. For that alone, he left the world a better place.

https://www.motherjones.com/environment/2016/02/lead-exposure-gasoline-crime-increase-children-health/