Mother Jones: America's Real Criminal Element: Lead

It turns out that lead is very highly correlated with crime rates.

http://www.motherjones.com/environment/2013/01/lead-crime-link-gasoline

And lead is still used in gasoline in many places. Leaded gasoline is still for sale in the UK for use in classic cars, and aviation gas worldwide:

http://www.scientificamerican.com/article.cfm?id=lead-in-aviation-fuel

And to think I used to play with lead fishing lures as a kid :/