Controversy has arisen again about whether holding a cell phone next to the head for too many minutes a day threatens the brain with electromagnetic radiation. The preponderance of evidence continues to indicate there is no threat. Many people do not realize, however, that we are increasingly surrounded by technologies that emit radiation in the same radiofrequency portion of the electromagnetic spectrum: WiFi routers, Bluetooth transmitters and more.

As the graphic above shows, the radiation emitted in this region is nonionizing: it may heat molecules in the body but does not ionize them (that is, set electrons free). Ionizing radiation, which can tear molecules apart and therefore potentially damage DNA—is the greater worry.

— Mark Fischetti

Graphic courtesy of Jerrold Bushberg. Reproduced with permission from The Essential Physics of Medical Imaging, 3rd edition, by Jerrold Bushberg et al. © Lippincott Williams & Wilkins, 2012.