Mother Jones magazine cites “an astonishing body of evidence” of studies showing that higher childhood blood lead levels are consistently associated with higher adult arrest rates for violent crimes, and that “gasoline lead is responsible for a good share of the rise and fall of violent crime over the past half century.”
Murder rates have always been higher in big cities than in towns and small cities. One researcher said it might have a surprising explanation: because big cities have lots of cars in a small area, they also had high densities of atmospheric lead during the postwar era. As lead levels in gasoline decreased, the differences between big and small cities largely went away. The difference in murder rates went away too. Today, homicide rates are similar in cities of all sizes. The gasoline lead story may be the only hypothesis that persuasively explains both the rise of crime in the ’60s and ’70s and its fall beginning in the ’90s. Two other theories—the baby boom demographic bulge and the drug explosion of the ’60s—at least have the potential to explain both, but neither one fully fits the known data.