Two Types of Airport Body Scanners Exist
The U.S. Transportation Security Administration started using advanced imaging technology as an extra security precaution in 2007, expanding it to a primary measure in early 2010 after the unsuccessful attempt by a passenger to blow up a plane with explosive powder.
Backscatter technology can detect objects that regular X-ray scanners and metal detectors can't pick up very well, like ceramic knives, drugs and liquid explosives. Backscatter X-ray scanners emit low doses of radiation to the whole body. The backscatter X-ray scanner sees through clothes and is capable of producing photo-quality views of its subject. Their use in airports started in 2007.
Another type of airport scanner, which uses millimeter wave technology, does not emit ionizing radiation and has no proven health effects. Both Brenner and Schauer agree these types of airport scanner are ideal. However, U.S. airports use a mix of both scanner types, with the only alternative being the controversial full-body pat-down.
Radiation Doses from Airport Body Scanners Minimal?
Schauer, executive director of the National Council on Radiation Protection and Measurements, contends that adding up trivial risks over large populations or time periods produces a distorted image of risk. In many cases, he noted in his paper, the collective dose increases with the number of people exposed, but the benefits and risks to each person remain constant.
"The risk of health effects from backscatter X-ray systems ... is very small as long as their use is justified, optimized and complies with applicable dose limits," Schauer said. "When these fundamental radiation protection objectives are achieved, the benefit of exposing people to X-rays exceeds any risk."
The makers of the backscatter scanners, Rapiscan Systems, have said that the backscatter scanners emit a dose of radiation equivalent to 1/1000 of a dental X-ray. According to the Health Physics Society (HPS), a person undergoing a backscatter scan receives approximately 0.005 millirems (mrem, a unit of absorbed radiation). American Science and Engineering, Inc., actually puts that number slightly higher, in the area of .009 mrem. According to U.S. regulatory agencies, 1 mrem per year is a negligible dose of radiation, and 25 mrem per year from a single source is the upper limit of safe radiation exposure. Using the HPS numbers, it would take 200 backscatter scans in a year to reach a negligible dose -- 1 mrem -- of radiation.However, Brenner noted that scientists have not been able to independently measure radiation doses from backscatter scanners because they have not been granted access to backscatter scanners to verify the manufacturer's stated doses.
"The individual risks are obviously extremely small," said Brenner, director of the Center for Radiological Research at Columbia University in New York City. "A good analogy ... is that it's like a lottery. You buy a ticket, and the chances of winning are minuscule -- but that doesn't mean no one will win the lottery."
"So we won't know who it is who gets these radiation-induced cancer," Brenner added, "but it's going to be someone."
Brenner is concerned about the overall safety picture when you look at it from a larger, public health perspective, in which a billion travelers are scanned in the U.S. each year.
“In the present context, if a billion X-ray backscatter scans were performed each year,” writes Brenner, “one might anticipate 100 cancers each year resulting from this activity.”
FDA Says Airport Body Scanners Safe
According to the FDA, which regulates X-ray devices, “There is no need to limit the number of individuals screened or, in most cases, the number of screenings an individual can have in a year.”
Health Expert Weighs in on Airport Body Scanners
Brenner said he would not hesitate to go through a backscatter scanner on an occasional basis, but he would avoid the process if he were a frequent flyer or an airline employee, who might have to pass through the system several hundred times a year.
Brenner also points to a heightened risk of cancer among children, which he says is five to 10 times higher than the risk to middle-age adults. Flight personnel, who pass through scanners hundreds of times each year, could also be at greater risk than the average traveler.
But all things considered, Brenner said, he'd rather be screened with the no-radiation millimeter wave scanners, whose cost and effectiveness are similar.
"To me, it's a no-brainer to use a technology with no X-rays," Brenner said. "If you can use millimeter wave scanners ... you surely should."
- April 2011, Radiology;
- David Brenner, Ph.D., D.Sc., director, Center for Radiological Research, Columbia University, College of Physicians and Surgeons, New York City;
- David A. Schauer, Sc.D., executive director, National Council on Radiation Protection and Measurements, Bethesda, Md.;
Meta: Recent studies regarding the safety of airport body scanners are saying that use of these radiation machines pose little long-term health dangers, however, there is disagreement from health experts regarding the overall public safety of airport body scanners lingers due to the collective cancer risks because of the sheer mass of travelers who pass through airport body scanners every year.