Radon - the killer in tobacco
Out of the nearly 4,000 chemicals found in tobacco smoke, only two definite chemical carcinogens have been found - benzopyrine and nitrosamine. However, the most potent carcinogen in tobacco is radiation from the radioactive products of radon. Polonium-210 is the only component of cigarette smoke that has produced cancers by itself in laboratory animals by inhalation - tumors appear at a level five times lower than the dose to a heavy smoker.
Lung cancer rates among men kept climbing from a rarity in 1930 (4/100,000 per year) to the No. 1 cancer killer in 1980 (72/100,000) in spite of an almost 20 percent reduction in smoking. But during the same period, the level of polonium-210 in American tobacco had tripled. This coincided with the increase in the use of phosphate fertilizers by tobacco growers - calcium phosphate ore accumulates uranium and slowly releases radon gas.
As radon decays, its electrically charged daughter products attach themselves to dust particles, which adhere to the sticky hairs on the underside of tobacco leaves. This leaves a deposit of radioactive polonium and lead on the leaves. Then, the intense localized heat in the burning tip of a cigarette volatilizes the radioactive metals. While cigarette filters can trap chemical carcinogens, they are ineffective against radioactive vapors.
The lungs of a chronic smoker end up with a radioactive lining in a concentration much higher than from residential radon. These particles emit radiation. Smoking two packs of cigarettes a day imparts a radiation dose by alpha particles of about 1,300 millirem per year. (IEM) For comparison, the annual radiation dose to the average American from inhaled radon is 200 mrem. However, the radiation dose at the radon "action level" of 4 pCi/L is roughly equivalent to smoking 10 cigarettes a day.
Philip Morris scientists wondered how come that the heavy tobacco users in the Caucasus live remarkably long lives. The local tobacco growers do not use phosphate fertilizers. But the American smoker inhales on average about 0.04 pCi of polonium-210 per cigarette, which disgorges alpha particles. It has a half life of only 138 days, making it thousand times more radioactive than the nuclear fuel used in the Hiroshima bomb.
Polunium-210 is soluble and is circulated through the body to every tissue and cell in levels much higher than from residential radon. The proof is that it can be found in the blood and urine of smokers. The circulating polonium-210 causes genetic damage and early death from diseases reminiscent of early radiological pioneers: liver and bladder cancers, stomach ulcers, leukemias, cirrhosis of liver, and cardiovascular diseases.
The Center for Disease Control concluded "Americans are exposed to far more radiation from tobacco smoke than from any other source." The Surgeon General C. Everett Koop stated that radioactivity, rather than tar, accounts for at least 90% of all smoking-related lung cancers.
Cigarette smoking accounts for 30% of all cancer deaths. Only poor diet rivals tobacco smoke as a cause of cancer in the U.S., causing a comparable number of fatalities each year. However, the National Cancer Institute, with an annual budget of $500 million, has no active funding for research of radiation from smoking or residential radon as a cause of lung cancer, presumably, to protect the public from "undue fears of radiation."
Dr. Gordon Edwards: Estimating Lung Cancers