The new generation of full-body airport security scanners emits too little radiation to pose a serious risk to passengers, according to a study published this week in the Archives of Internal Medicine.
The scanners, which debuted last year to objections sparked by their revealing images, were also criticized by those who feared they delivered a risky dose of radiation.
“Based on what is known about the scanners, passengers should not fear going through the scans for health reasons, as the risks are truly trivial,” the report says.
Two hundred and forty-seven of the 486 scanners deployed by the Transportation Security Administration thus far are “backscatter” models that use radiation to detect potentially threatening objects. The remaining new machines emit energy waves that the study equates to the strength of a cellphone.
“This study reinforces what other independent testing has shown: that all passengers can rest assured the technology used to protect them when they fly is also safe for their health,” said Nicholas Kimball, a TSA spokesman.
The report was done by two doctors — Rebecca Smith-Bindman and Pratik Mehta — at the University of California in San Francisco.
“The doses of ionizing radiation emitted by these backscatter X-ray scans is exceedingly low — so low that it is really now known whether there is any potential for causing harm,” they said.
They compared the dose from scanner exposure to the amount of natural radiation a passenger experiences during one to three minutes of flight time.
“The suggestions that individuals who may be particularly vulnerable to radiation effects may want to avoid the scans are unwarranted concerns; the flights themselves may expose them to a small increased exposure to ionizing radiation, but the scans will further increase that exposure by only a small amount,” the study says.
Radiation exposure increases in flight because commercial flights at cruising altitude are closer to the sun. Using a six-hour flight as an example, Smith-Bindman and Mehta said that passing through a backscatter machine would increase the overall radiation exposure by 1 percent.
They estimated that 50 backscatter scans equaled the exposure from a dental X-ray, 1,000 scans compared with a chest X-ray and 4,000 scans were like a mammogram.
The report projects that of 100 million annual passengers, six might develop cancer as a result of the backscatter. Of 1 million passengers who fly more than 10 trips of six hours or longer per week, four might get cancer from backscatter exposure.
“We try to balance risks and benefits of everything we do,” the authors wrote, “and thus while the risks are indeed exceedingly small, the scanners should not be deployed unless they provide benefit — improved national security and safety — and consideration of these issues is outside the scope of our expertise.”
The TSA has responded to privacy issues raised by the scanners by testing new software that presents its images as gray, cookie-cutter outlines of the human form. Silhouettes appear on a screen about the size of a laptop computer that is attached to the scanning booth. The original concept sent the more revealing full-figure image to a private screening room manned by a TSA staff member.