You're a little off on the nicotine, just a little.Nicotine by itself, is as safe as caffeine. It makes you smarter, but it is addictive. Just like caffeine. Cigarettes are bad from the smoke, combustion, and particulate matter.
"Nicotine is a dangerous and highly addictive chemical. It can cause an increase in blood pressure, heart rate, flow of blood to the heart and a narrowing of the arteries (vessels that carry blood). Nicotine may also contribute to the hardening of the arterial walls, which in turn, may lead to a heart attack." Johns Hopkins