Benzene

This particular chemical is found in extremely high doses in cigarettes. In fact, there is a higher percentage of Benzene in a cigarette than any other chemical we'll be mentioning in this post. Considering it is otherwise found in pesticides and gasoline, cigarette smoking accounts for half of all human exposure to this hazardous chemical. 

Not enough to scare you off nicotine just yet? Well, how about the fact that benzene also used in making dyes and synthetic rubber.