Cancer risk in relation to radioactivity in tobacco.

Leaf tobacco contains minute amounts of lead 210 (210Pb) and polonium 210 (210Po), both of which are radioactive carcinogens and both of which can be found in smoke from burning tobacco. Tobacco smoke also contains carcinogens that are nonradioactive. People who inhale tobacco smoke are exposed to higher concentrations of radioactivity than nonsmokers. Deposits of 210Pb and alpha particle-emitting 210Po form in the lungs of smokers, generating localized radiation doses far greater than the radiation exposures humans experience from natural sources. This radiation exposure, delivered to sensitive tissues for long periods of time, may induce cancer both alone and synergistically with nonradioactive carcinogens. This article explores the relationship between the radioactive and nonradioactive carcinogens in leaf tobacco and tobacco smoke and the risk of cancer in those who inhale tobacco smoke.