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I agree, exposure to lead, particularly from gasoline, was a huge factor in violent crime.

It probably also explains the "weird spike" in violence from the 60's to the 80's mentioned at the end of the article, as more and more people started driving and cities converted to car-centric.

The phrasing makes it seems the scientists dismiss unleaded fuel for "possibly had some effect" while their phone theory accounts for "19 to 29 percent". I got good feelings from the theory that unleaded fuel prevented brain damage and reversed climb of violence and Thomas Midgley, credited with both leaded fuel and CFC crisises was strangled by one of his inventions before he could harm Earth a third time.

The whole world went from leaded to unleaded fuel around the same time. During that time in Poland, where I live, crime, if anything, went up. Someone should do a study across all countries where the data is obtainable to confirm/refute the lead hypothesis.

You absorb the lead when you are a child. It's biggest effect is in young adult years. I'd expect at least a 10 year delay from "reduction of atmospheric lead" to "reduced crime rates".