The relationship between lead exposure and homicide

Context:

Previous studies have suggested that excessive lead exposure is related to aggressive and violent behavior.

Objective:

To evaluate the association between estimated air lead concentrations and homicide rates.

Design:

Cross-sectional ecological study.

Setting:

All counties in the contiguous 48 states of the United States.

Exposure Measure:

Estimated air lead concentrations and blood lead levels.

Main Outcome Measure:

The homicide rate in each county.

Results:

Negative binomial regression was used to examine the relationship between air lead concentrations and the incidence of homicide across counties in the United States (N = 3111). After adjusting for sociologic confounding factors and 9 measures of air pollution, the only indicator of air pollution found to be associated with homicide rates was air lead concentration. Across all counties, estimated air lead concentrations ranged from 0 to 0.17 μg/m³. The adjusted results suggest that the difference between the highest and lowest level of estimated air lead is associated with a homicide incidence rate ratio of 4.12 (95% confidence interval, 1.02-16.61).

Conclusion:

The results of this study support recent findings that there is an association between lead exposure and violent behavior.