The European Commission decided in November to ban airport body scanning X-ray backscatter machines after studies found a small number of cancer cases linked to use of the devices. The decision affects all airports in Europe, with an exception for U.K. airports that will be allowed to test them, but not deploy them permanently. According to the European Commission, "only security scanners which do not use X-ray technology are added to the list of authorized methods for passenger screening at EU airports." The commission does approve of full non-X-ray body scanners (radio wave scanners are among those used in the U.S.) when operated under specific guidelines and restrictions. In the U.S., the TSA uses more than 250 backscatter machines at the nation's 100 busiest airports and is unmoved by Europe's position. The degree of cancer risk varies somewhat depending on the source ... as does the degree of usefulness of the machines themselves.
According to the U.S. Food and Drug Administration, backscatter machines bring a cancer risk of one in 400 million. Research reported by PBS Newshour/ProPublica states that the risk of developing cancer from the machines is "anywhere from six to 100" passengers per year. In a detailed paper submitted to the White House, University of California researchers said that because backscatter X-ray energy is absorbed mainly by the skin and underlying tissue, the skin dosage may be dangerously high in localized areas. The TSA says the amount of radiation emitted by a backscatter machine is similar to three minutes at altitude in a jetliner. For that risk, the TSA says use of the machines has since 2010 identified more than 300 illegal items and potentially dangerous items on the bodies of passengers at airports in the U.S. In January of 2011, a security expert said that in studies, participants asked to sneak explosives past backscatter machines "did it with such ease" that "there is no case for scanners." The director of the Center for Radiological Research at Columbia University Medical Center told TIME magazine that backscatter machines are "equally effective" and "cost about the same" as machines that use less destructive millimeter waves. The TSA uses both. As for the legality of their use, in the U.S. a Court of Appeals was not moved by statutory or constitutional arguments challenging use of the scanners, but agreed that "the TSA has not justified its failure to issue notice and solicit comments." (PDF)