Recent articles (1-4) have described the dangers to children and adults of secondhand cigarette smoke. However, it is not widely known that cigarette smoke is substantially radioactive. (5-14)
Tobacco plants in the United States are grown in soils and with high-phosphate fertilizers which are naturally contaminated with the alpha-emitting radionuclide polonium-210 (Po-210). (13-14) In addition, evidence exists that other atmospheric radon-222 (Rn-222) daughter products are also incorporated into the plant. (10, 15) The average cigarette contains 0.3 pCi of Po-210, (7) which is melted, vaporized, inhaled, and ultimately deposited along the tracheobronchial epithelial linings of smokers. (16-19).
In 1 year, a smoker of 1 to 2 packs per day will irradiate portions of his or her bronchial epithelium with about 8 to 9 rem. (8,16,18) This dose can be contrasted with that from a standard chest x-ray film of about 0.03 rem. (20) Thus, the average smoker absorbs the equivalent of the dosages from 250 to 300 chest x-ray films per year. Worse, that energy is deposited along the short radiative tracks of the alpha particles emitted, resulting in damage, destruction, mutation, or all of these to adjacent bronchial epithelial cells. (21-24) Studies (7,25,26) have been inconclusive in answering whether cigarette filters are substantially effective in removing radioactive particles from mainstream smoke.
Considering that the average smoker will absorb approximately 80 rem into the lung epithelial lining in about 10 years, cancer can be anticipated as a prominent result of the habit.
Tobacco's radioactive content was first described in the mid-1960's. (8,16-18) Subsequent studies (27,28) suggested lesser dosage rates than those mentioned here. However, these rates were proved to be erroneous. (18,19) Despite initial interest, little has been published on the subject in recent years, and the radioactive risks to children from secondhand smoke remain unknown.
Studies must be undertaken to quantify Po-210 deposition in children of smoking parents. Until then, smokers should be informed that they spend their days in radioactive clouds and that they, their families, and friends are at potential risk from those clouds of smoke.
I have observed that many parents who smoke, on hearing of their unexpectedly large exposure to radiation from smoking, have found the strength and motivation to quit the habit. I hope that as this information becomes more widely known, fewer children will suffer the ill effects of secondhand cigarette smoke and that this potentially clinically significant exposure to radiation will be eliminated.