Some atomic radiation is made up of particles that are weightless and travel very fast, such as high-energy photons or gamma rays. Similar high-energy photons can be generated by man, without using a radioactive source, and these are usually called X rays. Perhaps your doctor or dentist has taken an X ray of you. Both X rays and gamma rays could be compared to high-velocity rifle bullets.

A small dose of radiation might be much more dangerous to one person than to another. A child with severe allergies might be three or four times as likely to get cancer as would a normal child. Perhaps a third child was exposed to radiation when his mother was x-rayed while pregnant with him. This child’s risk of getting leukemia would be 50 percent higher than that of the normal child. But what would happen if the child with allergies had been exposed to those X rays in the womb? His cancer risk would now be, not three or four times, or even six or eight times as high, but fifty times as high as that of the normal child!

“Extra” Radiation

Most people today receive “extra” radiation in addition to what they get from the normal radioactive background. In the United States the average yearly dose of radiation is nearly doubled because of these extra sources, mostly in the form of medical X rays. Could that chest X ray you got last month give you leukemia five years from now? Possibly, but before you panic, remember that all medical procedures​—even taking an aspirin—​entail some risk. If the benefits of an X ray outweigh the slightly increased cancer risk, then your doctor may advise an X ray with good reason.

Keep track of your X rays and don’t ask your doctor for X rays he doesn’t think you need. When given an X ray, ask for proper shielding.