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 :/
