Cigarette smoke contains over 70 known carcinogens (cancer-causing chemicals). You can find a list of these carcinogens and other tobacco toxins here:
I’d like to draw your attention to some of these, in particular:
(1) AFLATOXIN B-1, produced by several species of the fungus, Aspergillus, is one of the most potent carcinogens known to man, and it causes mutations in DNA that lead to cancer. It is found in cigarettes.
(2) Nitrosamines, well studied powerful cancer-causing chemicals, which include the substance, NNN, among others. These are some of the well known carcinogens in tobacco and tobacco smoke.
(3) Polycyclic aromatic hydrocarbons (PAHs), which include benzo(a)pyrene, the first carcinogenic chemical ever to be discovered. Numerous other powerful PAH carcinogens are found in tobacco smoke.
(4) Carcinogenic heavy metals and radioactive elements, including cadmium, arsenic, nickel, chromium, lead, as well as the radioactive elements, Uranium-235, Uranium-238 and Polonium-210.
And there are other carcinogens in tobacco and tobacco smoke, so take your pick- they are among the most carcinogenic and mutagenic chemicals known to humanity. And if you think you can avoid them by chewing tobacco products rather than by smoking them, you’re wrong- many of them are present in tobacco whether it is smoked or not.
The Great Tobacco Plague 