March 28th, 2011
06:47 PM ET
If you’ve traveled through an airport lately, you’ve probably seen one of the new full body X-ray machines called a backscatter, a type of imaging technology used by the Transportation Security Administration to identify concealed items.
A special article published Monday in the Archives of Internal Medicine says “passengers should not fear.” The device, which raised concerns among some because it uses small doses of ionizing radiation, a known carcinogen, poses “no significant threat” even to frequent fliers, the authors say.
Researchers at the University of California San Francisco estimated the cancer risks associated with exposure to the backscatter and found that the scan, which takes only a few seconds, contributes less than 1% of the radiation dose a flier would receive from cosmic rays during the actual flight.
They also estimated that for every 100 million passengers who flew on seven one-way flights (just over three round trips) per year, six extra cancers were detected over the course of a lifetime. For every 1 million frequent fliers – defined in this study as those who took 10 trips per week for a year where each trip lasted at least six hours – four additional cancers were detected.
“A lot of people are fearful of radiation, and I think they need to be conscious that all radiation is not the same,” says study author Dr. Rebecca Smith-Bindman, a California radiologist. “I don't think the risk is worth us worrying about because it is so low.”
According to the TSA, 486 advanced imaging technology machines are being used at 78 airports nationwide. The agency says the devices are safe and meet national health and safety standards for all passengers, including children, pregnant women, and individuals with medical implants.
Still there are some who are cautious. “I think one of the main issues with this paper is that it took doses direct from the manufacturers data, but in other recent publications doses were estimated based on the actual x-ray backscatter images that the machine produces and were higher,” says David Brenner, director of the Center for Radiological Research at the Columbia University Medical Center.
He published an article in April in the journal Radiology, and also found the radiation exposure to be small, but says even though the cancer risk is low, it is possible. “The bottom line is that both my paper and this suggest that there will be some cancers produced in the long run from mass screening with X-rays,” he says. "The analogy I usually give is with someone buying a lottery ticket. Your individual chance of winning is extremely small, but we do know that some people will indeed win."
“There is considerable uncertainty about just how many cancers that will be.”
Passengers should keep in mind they don’t have to face the risk if they don’t want to. TSA press officer, Kristin Lee, notes that the technology is optional for all passengers, and that those who do not wish to go through the backscatter screening will receive an alternative screening, including a pat-down. Find out what experts do when they go to the airport later this week in the Empowered Patient column.
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