Is Environmental Contamination Responsible for Violent Crime?

America's Real Criminal Element: Lead
Kevin Drum, Mother Jones, January/February 2013 Issue

Across the US, violent crime peaked in the early 1990s and then began a steady and significant decline. Not unique to a particular city, this declining trend is seen nationwide, including in New York, Dallas, Los Angeles, Washington DC, and Newark.  This article explores the reasons behind this trend, and in the process, researched a myriad of criminology theories: crime goes down when the economy is booming and goes up when it's in a slump; crime drops in big cities are mostly a reflection of the crack epidemic of the '80s finally burning itself out; demographics (as numbers of young men increases, so does crime); prison expansion; guns and gun control; family dynamics; race; parole and probation policies; raw number of police officers; and legalized abortion.

The author found a growing body of research linking lead exposure in small children with complications later in life, including lower IQ, hyperactivity, behavioral problems, learning disabilities, and juvenile delinquency. A large body of evidence suggests that the use -- and discontinuation -- of tetraethyl lead in gasoline may explain as much as 90 percent of the rise and fall of violent crime over the past 50 years. And this relationship seems to hold true for cities of different sizes, both within the US and internationally.

Read the article here.

And several of the cited studies:
How Lead Exposure Relates to Temporal Changes in IQ, Violent Crime, and Unwed Pregnancy
Environmental Policy as Social Policy? The Impact of Childhood Lead Exposure on Crime
Understanding international crime trends: The legacy of preschool lead exposure
The urban rise and fall of air lead (Pb) and the latent surge and retreat of societal violence
Association of Prenatal and Childhood Blood Lead Concentrations with Criminal Arrests in Early Adulthood