Can you tell me, how bad is pure tobacco for you?

Very bad: It is not "impurities" in tobacco, or additives or anything else that does most of the damage - it is the tobacco. Doesn't matter if they call it "pure" or "organic" or whatever. It contains nicotine which helps you get addicted to smoking, and the smoke contains "tars" - toxic hydrocarbons, carbon monxide, formaldehyde and other poisonous substances that cause cancer, heart disease ; other ills.