Based on the discussions at the event, it is evident that body scanners can be easily defeated by concealing explosive materials in body cavities, the letter says. There is also little information on the health risks posed by the use of such scanners, according to the letter. The fact that the systems can be configured at any time to record and store images of travelers also raises privacy questions, the letter says.
"The public does not currently understand the inability of these devices to detect the types of explosive materials that could be used or the possible risks to privacy and health," Rotenberg and Nader wrote. "The Department of Homeland Security has made significant mistakes with similar programs in the past," they added, citing as an example the agency's discontinued effort to equip airports with so-called explosive trace portals (ETP), which are designed to detect traces of explosives on travelers' clothing.