According 'Science of total enviroment' magazine and a reasearch that starts from 2007 at Rome and Tarantas the Air we breath contains quantities of Drugs like Cocaine and Cannabis etc,

According results areas with High Usage have bigger density.

what that means,
if they modify a model that connects usage and merchandise with the 'spread in air', they might locate areas easier,
People might get used to Drugs with not even know them if they live near such areas,

just like pathetic smoking, when you sit next to a smoker.