Did leaded gasoline and lead-based paint create a crime wave in the last Millennium?
Apparently so, according to a housing and community development researcher.
Childhood lead exposure, including exposure to leaded paint, is strongly linked to changes in violent crime rates during the 20th Century, according to an international consulting firm specializing in both housing and environmental health issues.
While the nation has eliminated lead in gasoline, lead-based paint often found in older homes remains the leading cause of childhood lead poisoning in the U.S.
Lead disclosure laws were enacted because research reveals childhood lead exposure can create learning disabilities, attention deficit disorders, mental retardation, behavioral problems, reduced IQ levels and, in rare cases, death.
Research also shows a strong correlation between low IQs and criminal behavior, according to "Research Links Childhood Lead Exposure to Changes in Violent Crime Rates Throughout the 20th Century".
In his peer-reviewed study, researcher Rick Nevin, vice-president with ICF Consulting's Housing and Community Development Group, found:
- Variations in childhood gasoline lead exposure from 1941 to 1986 explain about 90 percent of the variation in violent crime rates from 1960 to 1998.
- Variations in childhood paint lead exposure from 1879 to 1940 explain 70 percent of the variation in murder rates from 1900 to 1960.
Lag times between lead exposure and variations in crime rates are due to exposed populations reaching the young adult ages (15-25) most associated with violent criminal behavior.
"The association between lead exposure and undesirable social behavior is a sobering new indication of the potential consequences of failing to address the remaining lead exposure hazards for young children," Nevin said.
"Lead paint remains a hazard in more than 57 million pre-1980 homes, including more than 18 million pre-1940 homes that are likely to have high concentrations of lead in paint on a wide variety of surfaces, he added.
Nevin didn't merely compare leaded gasoline and leaded paint use with variations in crime stats, but also factored in other elements closely associated with criminal behavior, including teen and general unemployment, the proportion of the population in the crime-prone years, low economic status, single-parent households and other factors occurring since 1960.
The results included:
- The effect of overall unemployment and the proportion of the population in younger age brackets were found to be insignificant. Childhood lead exposure explained 88 percent of the variation in the overall crime rate, while teen unemployment explained just 2 percent.
- Only childhood lead exposure was found to have any significant effect on changes in the rate of aggravated assault, which accounts for about 60 percent of all violent crime.
- Childhood lead exposure explains 76 percent of the variation in robbery (33 percent of all violent crime) and teen unemployment explains 3 percent.
- An association between crime and economic status or family demographics could partially explain the rise in U.S. crime from 1960 through the 1980s, but demographics and economic status is inconsistent with the decline in crime rates during the 1990s.
Nevin's study also found an association between IQ and unwed births that can be explained by trends in childhood lead exposure.
"The number and percent of children exposed to lead paint hazards will certainly decline over time without any new public policy initiatives, due to the natural rates of demolition and renovation for older housing. In the absence of new policy initiatives to address lead paint hazards, however, a continuing temporal association between lead exposure and crime and unwed pregnancy suggests that lead exposure could still have life-altering consequences for countless Americans born over the next several decades," Nevin wrote.