Use of millimeter waves for airport screening is ramping up, and some will be either concerned, curious, or both, about potential health effects of these full body scanners.

The Transportation Security Administration, TSA, indicates in a simple graphic that radiation from these devices is minimal:

TSA Graphic Indicating Comparitively Low Dose

TSA Graphic Showing Relative Strength of Millimeter Waves

The graphic implies that a millimeter wave machine exposes people to far less radiation than a television set or the sun.  I’m not sure why there’s a radio antenna on a boom-box in the picture, because I’d not expect a boom-box radio to emit much, if any, radiation.

One good place to learn more about the state-of-the-art of millimeter wave scanning  is a 2007 National Academies Press publication, Assessment of Millimeter-Wave and Terahertz Technology for Detection and Identification of Concealed Explosives and Weapons. Among other information, this publication describes differences between active and passive millimeter wave technology. The passive type simply receives millimeter waves emanating from a source, aiming no radiation at the body. On the other hand,

Active imaging systems illuminate the detection space with a beam of millimeterwavelength/terahertz power, either by illumination of the entire space or as a focused beam scanned over the object, with detectors specifically sensitive to the illuminating frequencies. Although millimeter-wavelength/terahertz energy passes through typical clothing materials, this non-ionizing energy penetrates the human body to only about skin depth. Therefore, the potential health effects of this radiation are significantly lower than those from the competitive imaging technology using ionizing x-rays, although the general population may not fully understand this.

This relative comparison of millimeter waves to imaging the body with X-rays, which sounds like a non-starter, does not really say anything  about about the safety of millimeter waves. Penetrating to “about skin depth” sounds innocuous, but we need to know about dose-response, and the like, to get a handle on health effects, if there are any. It should prove illuminating to see which type is being put into service by the Dutch, among others.