Lead & crimeDecrease in lead exposure in early childhood likely responsible for drop in crime rate

Published 5 July 2017

Exposure to lead in the preschool years significantly increases the chance that children will be suspended or incarcerated during their school careers, according to new research. Conversely, a drop in exposure leads to less antisocial behavior and thus may well be a significant factor behind the drop in crime over the past few decades.

Exposure to lead in the preschool years significantly increases the chance that children will be suspended or incarcerated during their school careers, according to research at Princeton Universityand Brown University. Conversely, a drop in exposure leads to less antisocial behavior and thus may well be a significant factor behind the drop in crime over the past few decades.

Given that children who are suspended or incarcerated are more likely to be involved in crime as adults, the finding supports the hypothesis that falling crime rates over the past few decades were caused largely by a sharp decline in childhood lead exposure. Lead was banned from house paint in 1976, and leaded gasoline was phased out between 1979 and 1986.

Princeton says that people exposed to lead as young children (from 0 to 6 years old) are more likely to exhibit poor thinking skills and impulse control, to have trouble paying attention, and to behave aggressively. These traits can lead to antisocial or criminal behavior in adults. Studies seeking links between adult crime and early childhood lead exposure have suggested that the drop in lead exposure could explain up to 90 percent of the sharp downward trend in U.S. crime that started in the mid-1990s.

But other explanations have also been proposed. For example, said Princeton’s Janet Currie — the Henry Putnam Professor of Economics and Public Affairs — falling crime rates have been tied to increased availability of abortions, improved policing, the growth of the prison population, and the waning of the crack-cocaine epidemic. Because these phenomena all occurred around the same time, it can be hard to distinguish their effects from one another. The researchers sought to find lead exposure’s effect on school disciplinary problems and juvenile incarceration, which could shed light on whether the decrease in lead exposure was in fact a contributing factor to the decline in the crime rate.

Currie and Anna Aizer, a professor of economics and public policy at Brown who did postdoctoral work at Princeton’s Center for Health and Wellbeing (CHW), based their study on data covering about 120,000 children born in Rhode Island. The study appeared as a working paper on the National Bureau of Economic Research website.