While I’m wary of monocausal explanations, one case where I’ll make an exception has to do with lead poisoning and crime. As Kevin Drum has pointed out (for a very long time), there is compelling evidence that the surge in crime (e.g., murder rates) in the 1980s through the mid-1990s can be attributed, in considerable part, to lead poisoning. Given what we know about the effects of lead poisoning on everything from impulse control to school performance (and general cognitive performance), it shouldn’t surprise anyone that lead poisoning led (pun intended) to an dramatic increase in criminal activity.

That’s why this portion of an op-ed by one of the doctors who brought Flint’s lead contaminated water to public attention is really striking (boldface mine):

There was a water crisis in Washington in the early 2000s, the kind of public health tragedy that government regulations are meant to protect us from. And it occurred right under the noses of our most powerful institutions. Unless that piece of history becomes more well known, and studied, it will continue to repeat itself.

I hadn’t been schooled in the Washington crisis, either, until my high school friend Elin Betanzo, a drinking-water expert who worked at the Environmental Protection Agency, came to a barbecue at my house and asked me about the water in Flint, where I work as a pediatrician at a children’s public clinic.

“The authorities say the water is fine,” I said to Elin.

That was in August 2015. I’d been hearing about problems with the drinking water in Flint for months. There were reports about its weird color, odor and taste — followed by bacteria and boil-water advisories. But officials kept saying everything was fine. And I believed them. At the clinic, with great confidence I told the parents of my patients that the drinking water was good enough for their kids to drink.

“It’s not fine,” Elin replied with a look of urgency on her face. “When you change the source of water or how it’s treated, it changes the way the water reacts with the pipes. That’s what we learned from the Washington water crisis. There was lead in the Washington tap water and it took years for anyone in charge to recognize it, let alone fix it.”

Lead in the Washington water? I couldn’t believe what I was hearing. “How could something like that take years to address?”

As a pediatrician, I know lead is the worst kind of poison. Permanent. Life-altering. A neurotoxin, lead can have serious consequences on the developing brain. For decades, levels that the lead industry wanted us to believe are O.K. we know now are not. There is no safe level of lead exposure for a child.

“Scientists and activists in D.C. tried to be heard — and were ignored,” Elin said angrily. “Lead was in the D.C. water for years. More lead than you could imagine. More lead than I want to think about.”

That night, I got very little sleep. In bed with my laptop open, I pored over news accounts of the Washington crisis. They were online and easy to find.

I learned that after the water treatment in Washington was changed in 2000, authorities did routine sampling and test results showed high concentrations of lead in the public drinking water. As in Newark and Flint, the public was never notified. Even the city government wasn’t told.

For the next four years, toxic levels of lead flowed freely and in heavy amounts in all four quadrants of the District — from Georgetown and Spring Valley to the farthest reaches of Georgia Avenue and Anacostia. It affected infants, children and adults; rich, poor and gentrified; working, middle and upper class; white and black.

There could be as many as 42,000 children in Washington who were in the womb or under 2 years of age when they were exposed, children who may have experienced inexplicable developmental delays, behavioral problems, low test scores and blunted potential from the impact of lead in their drinking water. Nothing was done for them.

A two year-old child in 2000 would be 21 years old now. Between 2013 and 2019, we’ve seen a massive increase in homicides (113 vs. 171, using August to August year-to-year data–remember that D.C.’s population has grown by around 8% in that time). I can’t help but think that part of the increase could be related to the 2000-2004 lead poisoning. Boring public health stuff matters.