Also in a more physical sense, Nicotine was used as an Insectiside to kill bugs at one point...Its part of the nightshade family.
Health risks include but are not limited to: Increased chance of blood clots, Bronchospasms, muscular twitches and pain, nausea, dry mouth, dirreah, heartburn, joint pain, light headedness, headaches, Sleep disturbances, weird dreams, Dizzyness, Increased/decreased heart rate, Increased Blood Pressure, Tachycardia (heart), Types of heart arithmia, Coronary artery constriction, and insuline resistance.
Meaning you can have blood clots, heart failure, diabetes, blood pressure, increased heart rate...
Addiction. Your brain becomes addicted to it, that is what makes ciggs so addicting. And with any addiction, quitting can cause withdraws or "nic-fits", depression, increase appetite (to substitute smoking when quitting), irritability, nervousness.
I saw on 60 minutes some new type of product called "snus", supposed to help people quit smoking. they say it's less then 50% as bad as smoking cigs, but didn't mention the risks.
I think Ecigs are much better. Water vapor with doses of nicotine that you can gradually lower until you are no longer addicted. It eases withdraw