There are over 4000 ingredients in smoking tobacco. Some are preservatives, others are designed to make tobacco more addictive, while some chemicals simply enhance the flavor. There are also a host of substances designed solely to mask the side effects associated with cigarette smoking, including respiratory difficulty and heart palpitations.
Nicotine
Perhaps the best-known ingredient in smoking tobacco is nicotine, which occurs naturally in the tobacco leaf. The nicotine molecule is a stimulant and appetite suppressant. Somewhat paradoxically, it also makes habitual smokers feel calm and relaxed. While neither cancer-causing nor even particularly toxic in relatively small quantities, nicotine is highly addictive.
Flavoring Agents
Tobacco, an organization that provides information to help smokers quit, lists honey, vanilla and caramel among the additives in smoking tobacco. These ingredients have no effect on the physical sensation of smoking, but do enhance the flavor of the tobacco. While food ingredients in smoking tobacco are considered safe, studies have never been done to determine whether the compounds produced when these ingredients burn have toxic side effects.
Cyanide
Both cyanide and hydrogen cyanide are added to smoking tobacco. Cyanide is a highly poisonous salt, and hydrogen cyanide is perhaps better known as the poisonous compound used in gas chamber executions. Both prevent the body's cells from being able to use food as fuel.
Organic Poisons
Benzene, acetone, and formaldehyde are toxic compounds in smoking tobacco. Formaldehyde is used to embalm dead bodies, while benzene is carcinogenic. Smoking tobacco often contains dichlorodiphenyltrichloroethane (DDT), an insecticide that was banned in the United States in the 1960's. DDT has since been banned worldwide, with the exception of limited use in malaria-ridden countries. No significant studies on the chronic effects of DDT inhalation---nor the inhalation of its combustion products---have been done, so it's difficult to anticipate what the long term ramifications of regular exposure might be.
Inorganic Poisons
Other poisons that can be found in smoking tobacco include sulfuric acid, used in car batteries, the poisonous element arsenic, cadmium and chromium, both metal elements that can lead to poisoning in high doses, and the radioactive element, polonium.
