Passengers on domestic flights as well as those on international flights heading to the U.S. are concerned about the potential health risks of full body scanners which produce exact anatomical images of the body and can detect objects and substances hidden by clothing. The use of these scanners at airports world-wide is expected to increase in the next few months, especially after the Christmas-day breach in security at Amsterdam’s Schiphol International Airport.

The American College of Radiology (ACR), Transportation Security Administration (TSA), and other professional organizations suggest that there is no reason to worry. ACR reported last week that it “is not aware of any evidence that […] the scanning technologies that the TSA is considering would present significant biological effects for passengers screened.”

The TSA uses two types of scanning systems: “millimeter wave technology” and “backscatter technology.” Millimeter wave technology “beams millimeter wave radio frequency (RF) energy in the advanced imaging spectrum over the body's surface at high speed from two antennas simultaneously as they rotate around the body. The energy reflected back from the body or other objects on the body is used to construct a three-dimensional image. The three-dimensional image, with facial features blurred for privacy, is displayed on a remote monitor for analysis.”

On the other hand, “backscatter technology uses low level X-ray to create a two-sided image,” and the “TSA is testing backscatter with an algorithm applied to the entire image to further protect passenger privacy.”

There are currently 40 millimeter wave technology units in use at 19 airports across the country. Six of them are used as primary screening at six airports and the others are used for secondary (random) screening at 13 airports. TSA has announced that it plans to purchase an additional 150 backscatter units. It is important to note that the use of advanced imaging technology is optional to all passengers at this point, and that passengers that do not want to want to be screened undergo a pat-down procedure.

According to the TSA, both technologies are safe to use on passengers. Backscatter technology uses low level X-ray and a single scan is the equivalent of two minutes of flying on an airplane, while the energy projected by millimeter wave technology is 10,000 times less than a cell phone transmission. The ACR agrees with these conclusions, and suggests that airline passengers flying cross-country are exposed to more radiation from the flight than from screening by one of these devices. Moreover, the National Council on Radiation Protection and Measurement (NCRP) has reported that a traveler would need to experience 100 backscatter scans per year to reach what is called as a Negligible Individual Dose (NID). NID is the “level of average annual excess risk of fatal health effects below which efforts to reduce radiation exposures to the individual are unwarranted.” Therefore, a traveler would require more than 1,000 such scans in a year to reach the effective dose equal to one standard chest x-ray.