Did taking lead out of petrol help cut crime a generation later?
After decades of rising crime, rates across the industrialised world fell sharply from the 1990s. One striking explanation points to a change made twenty years earlier: removing lead from petrol. Children spared the metal's damage to developing brains, the argument runs, grew into less impulsive, less aggressive adults.
Lead has long been valued for being soft, workable, corrosion-resistant and useful as a radiation shield. Yet it harms many organs, especially the brain, and concern about even low exposures began in the 1970s; scientists now agree that no level in the blood is safe. Medical studies link it to impulsive behaviour, social aggression and a higher chance of attention deficit hyperactivity disorder, traits that can shape job performance, substance use and brushes with the law.
Researchers noticed that American anti-lead rules, tightened by the Environmental Protection Agency from the 1970s onward, took effect unevenly across the country, and that crime later fell unevenly too. In 2007 Jessica Wolpaw Reyes of Amherst College estimated that phasing lead out of gasoline accounted for roughly a 56 percent fall in violent crime between 1992 and 2002, while cautioning that the murder results were fragile. Anna Aizer and Janet Currie reported in May 2017 that Rhode Island boys exposed to more lead as children were far likelier to be suspended from school or held in juvenile detention. The journalist Kevin Drum popularised the idea in Mother Jones in 2013.
Globally, a California State University study cited by the United Nations in 2011 credited the end of leaded petrol with $2.4 trillion in yearly benefits, 1.2 million fewer premature deaths and 58 million fewer crimes. The Partnership for Clean Fuels and Vehicles, working with oil companies, governments and civil groups, led that phase-out. In 2022 Anthony Higney, Nick Hanley and Mirko Moro published the first meta-analysis, pooling 24 studies and finding substantial evidence tying lead to greater risk of crime, particularly violence.
Proof is hard, though. Correlation is not causation, and lead exposure tracks poverty, weaker schools, poor nutrition and thin medical care. The economists Steven Levitt and John Donohue credit other forces, including more police, larger prison populations and the waning crack cocaine epidemic. Most scholars see a mix of causes, with lead as one candidate among several.
Source: Lead–crime hypothesis
