Lead has well-documented effects on the brain and there is no safe level of exposure. Some research suggests lead may be linked to criminal behavior but that association may be explained by low socio-economic status, which is associated with both lead exposure and criminal behavior.
‘The level of lead in the blood may be similar across various socio-economical backgrounds, and it need not be the only factor that can influence criminal behavior.
This study removed low socio-economic status as a factor because high blood lead levels were observed among children from all socio-economic groups in New Zealand.
Around 553 individuals from New Zealand born between 1972-1973 who were followed up to age 38.
Blood lead levels measured at age 11 (exposure) showed cumulative criminal conviction, self-reported criminal offending, recidivism, and violence up to age 38 (outcomes).
This is an observational study. Researchers were not intervening for purposes of the study and they cannot control the natural differences that could explain the study findings.
Authors of the study were Amber L. Beckley, Ph.D., of Duke University, Durham, North Carolina, and coauthors
The results indicated that childhood lead exposure was weakly associated with conviction and self-reported criminal offending up to age 38; lead exposure was not associated with recidivism or violence.
The limitation of the study was that childhood blood lead levels were measured only one time at age 11.
The study concludes that there is no clear association between higher childhood blood lead levels and a greater risk for criminal behavior (a dose-response relationship) in settings where blood lead levels are similar across low and high socio-economic status.