There was a very interesting article[1] recently about the epidemiological link between leaded gasoline and crime.
[1] - http://www.motherjones.com/environment/2013/01/lead-crime-li...
[1] - http://www.motherjones.com/environment/2013/01/lead-crime-li...
The economist clearly doesn't agree with you, here's what they said about lead:
Jessica Wolpaw Reyes, an American researcher, has argued that the cognitive effects of exposure to lead were a primary determinant of violent crime, and unleaded petrol is to thank for the improvement. But the causal link is far from proven.
http://www.motherjones.com/environment/2013/01/lead-crime-li...