Lead and crime

We recently received a letter from the City of East Providence water utilities division asking us to check whether our service line contains lead. Since our house was built in 1935, this was a reasonable possibility. In the event, our line is galvanized iron or steel, not lead. But this ongoing effort to purge lead plumbing reminded me again of the impact of environmental lead on public health, including crime.

I’ve been following the gasoline lead-crime story for years, ever since Kevin Drum started writing about it on his blog and then in Mother Jones magazine. The upshot of a lot of research is that gasoline lead may explain as much as 90% of the rise and fall of violent crime over the past half century, not only in the US but around the world. If you haven’t followed the story, there’s a link at the bottom. Here are some of the nut grafs in the article.

Lead is well-known to be a neurotoxin, especially in children. Lead poisoning can cause behavior problems, learning disabilities, lower IQ, hyperactivity and aggression. All of these can contribute to school drop-out rates, school suspensions and delinquency.

“But we now know that lead’s effects go far beyond just IQ. Not only does lead promote apoptosis, or cell death, in the brain, but the element is also chemically similar to calcium. When it settles in cerebral tissue, it prevents calcium ions from doing their job, something that causes physical damage to the developing brain that persists into adulthood.”

Mapping the rise and fall of violent crime in the US yields a curve that looks remarkably similar to the rise and fall of leaded gasoline, just offset by a couple of decades:

“ . . . if you add a lag time of 23 years, lead emissions from automobiles explain 90 percent of the variation in violent crime in America. 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.”
Of course, correlation isn’t causation. But the correlation runs deeper than that:

“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.”

And so it does. And the correlation runs deeper still:

“Tulane University researcher Howard Mielke published a paper with demographer Sammy Zahran on the correlation of lead and crime at the city level. They studied six US cities that had both good crime data and good lead data going back to the ’50s, and they found a good fit in every single one. In fact, Mielke has even studied lead concentrations at the neighborhood level in New Orleans and shared his maps with the local police. “When they overlay them with crime maps,” he told me, “they realize they match up.””

And still deeper:

“Meanwhile, Nevin had kept busy as well, and in 2007 he published a new paper looking at crime trends around the world. This way, he could make sure the close match he’d found between the lead curve and the crime curve wasn’t just a coincidence. Sure, maybe the real culprit in the United States was something else happening at the exact same time, but what are the odds of that same something happening at several different times in several different countries?

“Nevin collected lead data and crime data for Australia and 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. When I spoke to Nevin about this, I asked him if he had ever found a country that didn’t fit the theory. “No,” he replied. “Not one.”

Read the article. Of course, the claim isn’t that *all* violent crime is caused by gasoline lead. Violent crime is as old as the story of Cain and Abel. But the possible causes of the sudden uptick and abrupt decline in violent crime from the ‘60s to the ‘90s have been thoroughly researched, and none of the alternative hypotheses fit the data as well as the lead-crime hypothesis.

the link between gasoline lead and crime