Ronald Herberman, director of the University of Pittsburgh Cancer Institute, shocked just about all law-abiding scientists (abiding by laws of physics, that is) with his warning last week to his faculty and staff that cell phones might pose a cancer risk.

This is troublesome because this time a really smart person is saying it, not just another nutcase.

The basics still ring true, and Herberman admitted as much: There's no convincing evidence that cell phone radiation causes cancer. Nor is there plausible biological or physical reasoning for why it would cause cancer.

Herberman said his warning is based on early, unpublished data from a 13-country study on cell phone use. Scientists tend to be wary of preliminary results, and many are scratching their heads over why Herberman would make such a stern and public warning now.

Herberman countered that until there's definitive proof that cell phones are harmless, users should practice some caution.

Play it safe Herberman's recommendations to minimize exposure are a godsend, but not for the reasons he intended. Limit conversations to a few minutes? Yes, particularly when it's about some stupid shoe sale you need to tell everyone about. Avoid cell phone use in buses and trains to limit second-hand exposure? Yes, particularly when I'm trying to sleep.

Limit use in cars, because high speeds force the phone to maximize power to find relay stations? Yes, yes: Let's shorten the bumper sticker reading "Shut up and drive" to just "shut up." This will definitely save lives as fewer chatty drivers means fewer deadly traffic accidents.

If only Crazy Frong ringtone caused cancer.

Yet how cautious must we be? Devra Lee Davis, Herberman's colleague, told the Associated Press, "The question is do you want to play Russian roulette with your brain."

Sounds frightening, but Russian roulette is played with one bullet in a six-shooter. Cell phone Russian roulette has perhaps one bullet in a gun that can hold several million.

Einstein and cell phones far from a scientific-illiterate technophobe, Herberman is author or co-author of over 700 peer-reviewed cancer articles dating back to the 1960s. He's smarter than me and likely you.

Yet Einstein, in a way, disproved the notion that cell phone radiation causes cancer. It's called the photoelectric effect: Light is composed of photons which, when above a threshold energy, can dislodge electrons from atoms for example, break chemical bonds in DNA and cause cancerous mutations.

That threshold energy is near the ultraviolet part of the electromagnetic spectrum, thousands of times more energetic than cell phone radio waves. UV, X-rays and gamma rays cause cancer. These photons are like golf balls, whereas radio photons are like cotton balls. You can throw millions of cotton balls against a window; it just won't break.

Heated arguments and hoaxes despite myriad studies showing no increased cancer risk from up to 20 years of cell phone use, some scientists continue to probe as they should, given the omnipresence of cell phones.

One alternate theory is that heat generated by cell phones can cook brain cells. This notion inspired a well-known hoax a decade ago, a demonstration of how two cell phones could cook an egg in 65 minutes. The lark seemed plausible and was illustrated in a series of stills on the Internet.

Then Cardo Systems, a provider of Bluetooth headsets, made videos of cells phones teaming up in groups of threes or fours to pop popcorn. Kernels are digitally removed from the video as popped popcorn is dropped onto the table. This publicity stunt proved successful enough to convince many of the power of cell phone radiation.

One problem with the heat theory is that the sun can heat your head far more efficiently than a cell phone. And your body does a rather decent job at regulating heat, anyway.

Cancer calling each type of living tissue absorbs radiation at a different frequency. So it is plausible that cell phone radiation bypasses the skin and skull and is absorbed selectively by brain tissue.

But scientists see only marginal evidence for changes at the cellular level induced by cell phone radiation in Petri dishes, fruit flies and mice. Similarly in human studies, such as the 13-country study Herberman was privy to, called INTERPHONE, there is at best only an inkling of evidence that cell phones might cause cancer if you use them long enough, for 30 or more years.

If there's a cancer association, it might be from the stress of being plugged in to a cell phone 24/7. We need to relax.

No one seems to mention how many lives are saved by cell phones. Police and emergency crews are informed of trouble nearly instantly now. Banning the technology would be shortsighted.

But seeing how millions of people still smoke and have unprotected sex, despite warnings, Herberman's message likely won't make a dent in changing behavior.