Full-body scanners not a health risk
A new study concludes that there is “no significant threat” from backscatter X-ray scanners; even though they use ionizing radiation, which is known to cause cancer, the doses are so low — less than 1 percent of the additional radiation a person gets from flying in an airplane in the first place, and about the same received through 3 to 9 minutes of daily life on the ground — that only a handful of cancer cases are likely to result directly from scanner use
Full-body scanners, especially those using X-rays, have aroused health concerns among passengers. According to an article published online Monday in the Archives of Internal Medicine, however, there is “no significant threat” from backscatter X-ray scanners. Even though they use ionizing radiation, which is known to cause cancer, the doses are so low — less than 1 percent of the additional radiation a person gets from flying in an airplane in the first place, and about the same received through 3 to 9 minutes of daily life on the ground — that only a handful of cancer cases are likely to result directly from scanner use.
“If individuals feel vulnerable and are worried about the radiation emitted by the scans, they might reconsider flying altogether since most of the small, but real, radiation risk they will receive will come from the flight and not from the exceedingly small exposures from the scans,” wrote the authors, Pratik Mehta of UC Berkeley and Dr. Rebecca Smith-Bindman of UC San Francisco.
The Los Angeles Times reports that Mehta and Smith-Bindman calculated the risks this way:
- All fliers: Among the estimated 100 million passengers who take 750 million plane rides per year, exposure to backscatter scans will produce six additional cancers over the lifetime of the individuals. To put that in context, the authors projected that forty million cancers would develop among this population anyway, without the scanner exposure.
- Frequent fliers: Among the one million frequent fliers who take ten 6-hour plane trips per week for a year, there would be four additional cancers. About 400,000 cancers would occur in those fliers anyway.
- Frequent fliers who are 5-year-old girls: The authors looked at 5-year-old girls because children are known to be more sensitive to radiation risk, and because studying girls allowed them to use existing models to look at breast cancer risk. There would be one additional case of breast cancer for every two million girls who travel one round trip per week, the authors estimated. Two hundred and fifty thousand breast cancers would be expected to occur in these girls over the course of their lifetimes.
- Mehta and Smith-Bindman also calculated that one would need to undergo fifty airport backscatter scans to equal the exposure from a dental X-ray; 1,000 to equal the exposure from a chest radiograph; 4,000 to equal a mammogram, and 200,000 to equal a CT scan.
- Still, they wrote, the TSA should reverse its stand and approve independent testing of the devices that would ensure they function properly and are used correctly. There are 486 of such scanners in use in 78 U.S. airports. By the end of 2011, there will be around 1,000.
