A nationwide research study shows a link between high levels of lead in the air and higher homicide rates. The research study, authored by Colorado State Sociologist Paul Stretesky with Michael Lynch of the University of South Florida, supports other recent research that shows a connection between lead exposure and violent behavior.
The study was published on-line this week on the Journal of the American Medical Association's website and was listed in the "top stories" section of the on-line journal in the Archives of Pediatrics and Adolescent Medicine.
The research, which included data from all 3,111 contiguous counties across the nation, focused on lead levels in the air and sought to determine if there was a connection between these airborne levels and homicide rates.
The study factored out poverty levels, race, other air pollutants, education levels and other considerations in its analysis.
The research showed that in those counties with the highest lead levels, the murder rate was correspondingly high. The incidence of homicide was estimated to be nearly four times higher in the county with the highest air lead level than in the counties with the lowest air lead levels.
Stretesky, an assistant professor in the sociology department at Colorado State, said that the findings demonstrate that airborne lead is another source of lead exposure that can lead to health problems and behavioral issues and may be more problematic than is widely understood.
"The results of our ecological study indicate that these additional environmental pathways may be more ubiquitous than imagined, affecting patterns of serious forms of violence such as homicide," Stretesky wrote in the on-line article. "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, human health and behavior, and crime control."
Stretesky said that the research doesn't directly indicate a causal relationship between high levels of lead in the air and increased homicide rates, but did say that the study is another indication that lead levels seem to predispose exposed individuals toward delinquency and aggression.
The study used 1990 data from the EPA on the estimated concentrations of airborne lead in all 3,111 contiguous counties in the country. The study correlated this data with data from the National Center for Health Statistics mortality files that contain homicide counts for each of the counties in the same year.
While lead exposure has been known to be a health hazard, these effects were widely associated with extreme cases of lead exposure that occurred through occupational exposure or lead paint ingestion.
Numerous studies have documented a strong association between air lead levels and levels of lead in the blood. Prior research shows that 70 percent of small lead particles that are inhaled are absorbed directly into the bloodstream, while larger lead particles may be trapped in mucous and swallowed.
Stretesky said implications of the study highlight the importance of continued national efforts toward reductions in lead pollution.
Last month, the Bush administration announced its plans to leave in place regulations set by the Clinton administration that require more businesses to report releases of lead or lead compounds into the environment. The standards require businesses that release 100 pounds or more of lead per year to report it to the government.
(The previous policy required a report only from businesses that used 10,000 pounds of lead or processed 25,000 pounds of lead compounds each year.)
The EPA has determined that most air lead comes from smelters, battery plants and industrial facilities that process lead.