SHOCKER: Der Spiegel: Thirty years after the Chernobyl disaster, it has become clear that radioactivity might be less harmful than originally thought. Some researchers even believe it may be beneficial in small doses.

The official message remains unyielding: The iron-clad rule is that radioactivity can be dangerous, even in small doses. There is no threshold for harmlessness. Even a single damaged cell could eventually become a tumor.

That standard measure of risk largely comes from a study launched in 1950, after the atomic bombs dropped on Hiroshima and Nagasaki. That year, a study of 86,000 survivors began, and is ongoing today. It demonstrated that the risk of cancer rises along with the radiation dosage.

Statistically, though, the effect of radiation only becomes apparent at a relatively high dosage — at about 100 millisieverts, as the unit biologists use to measure the effects of radiation on the body is called. That is 50 times as much as a person receives each year in Germany from natural background radiation. . . .

Some researchers believe that even the fundamental assumptions behind the calculations are wrong. One of them is Reinhard Wetzker. He leads the Institute of Molecular Cell Biology at the University of Jena. “The traditional risk model cannot be upheld,” he says. “It doesn’t take into account that the cells can deal very well with low dosages of radiation.”

People have been talking about radiation hormesis for a long time. But it complicates a simple story — radiation is bad! — and thinking about it might not produce the proper political views.