The full-body scanners in use at 78 U.S. airports can detect small amounts of contraband and hidden weapons, all while producing controversial images of travelers.
Federal officials say the “good catches” — small amounts of marijuana wrapped in baggies, ceramic knives concealed in shirt pockets — have gone unnoticed amid criticism that erupted over the ghostly X-rays and “enhanced” pat-downs.
But researchers and security experts question the technology’s ability to detect chemical explosives that are odorless, far smaller than previous incarnations and easily molded to fool machines and screeners.
Government testing has raised concerns about the effectiveness of full-body scanners.
By New Year’s Day, about 500 machines will be in use across the country. By the end of next year, 1,000 X-ray machines will be operational.
Following the United States’ lead, several nations have begun to test or install full-body scanners, including Australia, Canada, France, Germany, Japan, Russia and Britain. U.S. officials have also considered whether the machines could be used to enhance security at passenger rail stations.
Federal officials say the scanners represent the best technology that has passed both lab and field tests. But as with reading an X-ray, training is the most important factor in making sure that Transportation Security Administration officers can spot potentially dangerous items on passengers.
“The bottom line is that we are now able to detect all types of the most dangerous weapons — nonmetallic explosive devices,” said TSA spokesman Nicholas Kimball. “Even in small amounts, it can be picked up.”
Two types of scanning machines — backscatter and millimeter wave — have been installed at airports since 2007. Both produce the full-body images that attracted controversy. They work by bouncing X-rays or radio waves off skin or concealed objects. (Denver International Airport uses the millimeter-wave scanners.)
A recent paper published in the Journal of Transportation Security by two former University of California-San Francisco physicists said that images produced by the backscatter scanners would probably fail to show a large pancake-shaped object taped to the abdomen because it would be “easily confused with normal anatomy.”
As a result, a third of a kilo of PETN, a type of malleable explosive that could be discovered by a pat-down, would be missed, the scientists said.
To address the litany of security and privacy concerns over the full-body scanners, federal officials are testing several new technologies that will probably make their way into airports in the coming months.
