When I first read this story, I thought to myself, This is why you shouldn't believe everything you read on the internet. But I checked the source and did some research. I think they may be onto something here.
Alex Knapp, a science writer for Forbes magazine has written an article showing a strong parallel between the rising exposure to lead in America to the crime boom of the 60s and 70s. On the face of it, this makes sense. Lead is well known as a factor in brain damage and impairment. Most of us think of paint chips as a major source of lead. I still remember those Ad Council commercials from the 70s where some government official warns parents against letting kids eat paint chips (maybe he should have suggested Cheetos?).
Lead was removed from paint by the early 70s, but the highest exposure to the public actually came from leaded gas. As unleaded gas grew in use and leaded gas was fazed out, crime began to drop.
Credit for the seemingly unexplained drop in crime over the past two decades was quickly grabbed by politicians who embraced get tough policies on criminals. But maybe it was just a matter of getting the lead out...of gas!
Check Alex's article at this link: How Lead Caused America's Violent Crime Epidemic
Click here for another great article on the criminal mind by Adrian Raine, discussing factors that influence criminal behavior, including the decline in leaded gas, from the Wall Street Journal: The Criminal Mind