A new study that suggests a correlation between airborne lead levels and the murder rate.
The research showed that in counties across the United States with the highest airborne lead levels, the murder rate was correspondingly high.
It said that the murder rate was four time higher in the counties with the highest lead levels than in counties with the lowest.
Among the counties where the trend was most evident: Baltimore, Dallas, San Francisco and Cheboygan in Michigan.
The study was co-authored by Colorado State University assistant professor Paul Stretesky, a sociologist, and Michael Lynch, a criminology professor at the University of South Florida, Tampa. It was published Tuesday in the online edition of the Journal of the American Medical Association.
No Direct Causal Relationship
The research does not show a direct causal relationship between airborne lead levels and higher homicide rates, but could mean that people exposed to higher lead levels are predisposed toward violent behavior, the authors said.
“If the association uncovered in this analysis is truly reflective of a causal relationship, these findings may have important policy implications that link the need for continued efforts toward lead abatement,” the article reads.
The research studied 1990 data from all 3,111 U.S. counties except Alaska and Hawaii, comparing the murder rate with the Environmental Protection Agency’s estimates of air concentrations of lead and blood levels of lead. It factored out other things like poverty levels, race, other pollutants, and education levels.
Two previous studies concluded that there was a correlation between lead poisoning and delinquency. The latest research focuses exclusively on the murder rate.
Stretesky acknowledged that more work needs to be done to establish a direct link between lead levels and the homicide rate.
“I think at this point it’s pretty much speculative and we need to do more research,” Stretesky said.