Through a scanner, weakly

The recent flap over possible danger from airport body scanners - like the ongoing concern about cell phone radiation - demonstrates that for most Americans, radiation is scary, and that's all you need to know.

The appropriate meansurement for X-rays' impact on people is the amount of energy the rays contain. The unit used is the millirem, or mrem. According to international standards, 5,000 mrem per year is the maximum dose permitted for those who work with or around radioactive material. For the rest of us, the average yearly exposure is 620 mrem - most from outer space (from the sun, black holes, and supernovae) - and about 10 percent from medical procedures and other earthly causes.

Radiation exposure from airport full-body scanners is incredibly weak: about 0.01 mrem. After all, unlike medical X-rays, the scanners don't needd to look into your body - just through your clothes. By contrast, at 0.5 mrem, a dental X-ray is 50 times more powerful.

Here are some other figures, from data in the latest Newsweek magazine: 40 mrem for a mammogram, 50 mrem a year if you live in Denver, and 200 mrem a year from radon in the average home. It takes 100,000 mrem to get radiation sickness.

Worry about displaying your imperfections in an airport scanner if you must, but don't sweat the X-rays.