The work in this article does show nonlinearity of cell damage from alpha radiation in the dose range studied, but the lowest dose studied (5 percent of all cell nuclei hit) is probably several orders of magnitude above the mean lethal dose for any organism. The researchers need to look at linearity through the dose range where real organisms sustain survivable damage.

Charles Klabunde
Oak Ridge, Tenn.

Over the course of a lifetime, many people receive alpha particle hits to a proportion of their cells similar to that in the study. Although many of these particles would miss nuclei, evidence suggests that they cause damage greater than that predicted by the linear model. –B. Harder This article was biased toward the linear, no-threshold theory on radiation health effects. Especially troubling was the comment that radon is the second leading cause of lung cancer. Studies of homes in China, Japan, and the United States having radon levels up to five times the average indicate that the people in those homes have lower cancer death rates, if they are non-smokers.

Martin Healey
Cobb, Wis.