Smoking: Is Polonium the Villain?

One of the biggest mysteries in the relationship between cigarette smoking and the increase in lung cancer has always been: How does smoking actually cause the cancer? Last week two Harvard researchers suggested a possible explanation: radioactivity.

At the Harvard School of Public Health, Dr. Edward P. Radford Jr. and Dr. Vilma R. Hunt worked with polonium,* one of the rarest of the naturally occurring elements and until recently one of the hardest to detect. Many radioactive elements are found in tobacco leaves, as in all vegetation; they occur naturally and have nothing to do with man-made fallout, and they have been exonerated as causes of lung cancer. Polonium is different, the Harvard researchers reported in Science, because it vaporizes at a mere 500° C., far below the 800° temperature of a burning cigarette tip.

Experiments with machine-smoked cigarettes showed that polonium attaches itself to smoke particles and may also pass into the lungs with the inhaled smoke in the form of gas. The amount of polonium in tobacco, as in a tossed green salad, would be negligible if, like the salad, it passed quickly through the system. But the polonium-bearing smoke appears to get trapped in the tissues and crevices of the airways, say Drs. Radford and Hunt. Because of this trapping, they suggest, polonium builds up to concentrations that are high enough so that its radioactivity could begin the process that leads ultimately to lung cancer.