Background and Objective:
Prior research has demonstrated an association between lead exposure and criminal behavior at the population-level, however studies exploring the effect of lead exposure on criminal behavior at the individual-level have not been reviewed systematically. The intent of this study is to complete a systematic review of all studies assessing individual-level exposures to lead and the outcomes of crime and antisocial behavior traits.

Methods:
We included peer reviewed studies that were published prior to August 2022 and were classified as cohort, cross-sectional, or case-control. Studies measuring the outcomes of crime, delinquency, violence, or aggression were included. The following databases were searched using a standardized search strategy: ProQuest Environmental Science Database, PubMed, ToxNet and the Public Affairs Information Service (PAIS).

Results:
Seventeen manuscripts met our inclusion criteria. Blood lead was measured in 14 studies, bone lead in 3 studies, and dentine lead levels in 1 study. This systematic review identified a consistent and statistically significant association between exposure to lead in the prenatal and 5 - 6 y period and later delinquent and criminal behavior, with increasing blood lead concentrations in childhood prospectively associated with later arrests and convictions in six studies.

Conclusion:
There is limited data at the individual level on the effects of prenatal or childhood lead exposure and later criminal behavior and more evidence is necessary to evaluate the magnitude of the associations seen in this review. Our review, in conjunction with the available biological evidence, suggests that an excess risk for criminal behavior in adulthood exists when an individual is exposed to lead in utero or in the early years of childhood.