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RADON'S DANGEROUS DAUGHTERS

The specific alpha-emitter in tobacco smoke is polonium 210, a naturally occurring product—or "daughter"—of the decay of radium 226, which is, itself, a natural radioisotope. Polonium 210 was first isolated in cigarette smoke, in minute but significant amounts, by Dr. Edward P. Radford (professor of environmental epidemiology at the University of Pittsburgh and chairman of the prestigious Biological Effects of Ionizing Radiation—BEIR—Committee of the National Academy of Sciences) and Dr. Vilma Hunt (now a senior official in the Environmental Protection Agency).

In 1965, Radford and Hunt—along with several other researchers—published a report in the New England Journal of Medicine that related their findings of significant concentrations of polonium 210 in smokers' bronchial tissues. The article suggested that the cumulative dose of alpha radiation from years of smoking and inhaling polonium 210 might well be a key factor in the development of lung cancer.

Other scientists criticized the Radford-Hunt hypothesis, largely because they believed it unlikely that a relatively shortlived isotope such as polonium 210 (with a half-life of only 138 days) could expose lung tissue to enough radiation to cause cancer before its water-soluble particles were washed out of the lungs.

Further research was carried out in 1974-75 by Dr. Edward Martell, a radiochemist with the National Center for Atmospheric Research in Boulder, Colorado and the author of more than 75 scientific research papers. He discovered that the tiny leaf hairs on tobacco, called trichomes, attract high levels of lead 210 . . . another decay "daughter" of radium 226, which—unlike polonium 210—is carried into the lungs in insoluble smoke particles, and remains there for a 22-year halflife. In related experiments, Martell also found a rather startling match between the areas in which polonium 210 accumulates in the body and the sites of the major illnesses most often linked to smoking.

SOME DISTURBING CONCLUSIONS

The findings of Martell's study—and of some related research—were published in a 1975 American Scientist article entitled "Tobacco Radioactivity and Cancer in Smokers". The conclusions reached in that report included the following points

[1] The unusually high levels of lead 210 found in tobacco trichomes (and in the smoke) result from heavy applications of phosphate fertilizers used in commercial tobacco farming. Those chemical preparations contain significant quantities of radium 226 and of its nine primary decay products.

[2] When tobacco is smoked, the insoluble lead 210 particles accumulate in the lungs. . . and as they decay into polonium 210, the small cell populations around the radioactive particles are subjected to "hits" of alpha radiation that are hundreds of times greater than naturally occurring background radiation levels.

[3] If the polonium 210 particles were highly radioactive—or "hot"—they'd kill lung cells immediately. But since they're merely "warm" isotopes, they kill only a few healthy cells and damage others . . . by altering their genetic coding (while still leaving them able to reproduce). Over succeeding cell generations, however, those that contain alpha-altered DNA material become cancerous as a result of receiving further alpha hits.

[4] Unexpectedly large amounts of 210 particles are found in smokers' lung tumors.

[5] Unexpectedly high levels of the 210's are also found in lymph nodes adjacent to the sites of smokers' secondary cancers, because some of the insoluble particles are picked up by the lymph system and circulated through the body . . . collecting in lymph nodes and irradiating nearby organs.

[6] Finally, those fatty arterial deposits that characterize atherosclerosis show "anomalously high concentrations of alpha activity" . . . suggesting a possible explanation for the high rate of early coronaries among cigarette smokers.

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