There is a good-news-bad-news rhythm to the introduction of any pervasive new technology. With cellular telephones, for instance, the good news came with the explosive growth of the industry itself, which by November 1992 had recorded its 10 millionth customer. Three months later came the bad news: David Reynard, bereaved husband, appeared on "Larry King Live" with the remarkable accusation that cell-phone use had caused the brain tumor that killed his wife. Reynard, not surprisingly, was suing the cell-phone companies he held responsible. With that single anecdotal incident, Reynard set in motion a health scare that continues to play in the press and our societal subconscious to this day. If history is any indication, it will continue indefinitely. I can make this prediction free of concern about whether cell-phone use is truly carcinogenic. If it's not, in fact, our anxiety-and the amount of press that fuels this anxiety-is likely to last considerably longer. Such is the nature of fear and the nature of science, and the inability of the latter to dispel the former.

The noteworthy aspect of fear is that its shelf life is considerably longer when the object of fear is a threshold phenomenon-invisible, at the limits of detection, if not simply a figment of the imagination. This preternatural quality is crucial because both science and the human intellect have evolved to handle the material world with relative ease. After all, when automobiles kill tens of thousands of Americans each year, the mechanism of our demise is relatively obvious, as it is with guns. Anxiety is not the issue. Caution is. If science manages to unambiguously identify the agent of an illness, as happened with the AIDS virus, the shadow of impending doom is dispelled by the light of knowledge, and the medical research establishment marches off to deal with it. The rest of us, or most of us, alter our behavior accordingly and the prophylactic industry flourishes. But we don't, by and large, panic.