Airport full-body scanners pose little risk to human health, according to an analysis by medical experts published Monday.
But the report, published in the Archives of Internal Medicine, appears unlikely to end all debate over the controversial devices. For one thing, the report didn't rate the health risks as zero. Also, easing concern about radiation levels doesn't assuage another worry: that the detailed full-body scans are an invasion of traveler privacy.
"The radiation doses emitted by the scans are extremely small; the scans deliver an amount of radiation equivalent to 3 to 9 minutes of the radiation received through normal daily living," wrote Pratik Mehta of the University of California, Berkeley and Rebecca Smith-Bindman, a medical doctor at the University of California, San Francisco in the new report.
Still, the researchers say, their models showed that even such small doses of radiation can be expected to result in some additional instances of cancer –perhaps 6 instances over the lifetimes of 100 million people who travel. For context, that's far fewer than the cancers they expect linked to excess radiation caused by flying at high altitudes, and an almost imperceptible fraction of cancers expected in that population overall, from any causes.
"In medicine, we try to balance risks and benefits of everything we do, and thus while the risks are indeed exceedingly small, the scanners should not be deployed unless they provide benefit – improved national security and safety," Dr. Mehta and Dr. Smith-Bindman write. That question "is outside the scope of our expertise."
They said passengers should not fear to go through the scanners for health reasons.
The analysis comes as radiation is in the news for several reasons:
- Post-earthquake problems at Japan's Fukushima Daiichi nuclear facility have resulted in front-page headlines about measuring trace amounts of wind-borne radiation as far away as Massachusetts.
- The airport body scanners themselves may be emitting several times more radiation than initially realized, according to news reports this month. The Association for Airline Passenger Rights has asked the Transportation Security Administration (TSA) to halt using the machines until retesting has been completed.
- Debate continues over possible health effects from increasingly ubiquitous wireless communications including cellphones.
The radiation questions regarding body scanners focus on one type of machines the TSA uses, so-called backscatter X-ray scanners.
The other type, which also generates a detailed outline of the body for the purpose of identifying potential contraband items, are called millimeter-wave scanners. These emit low-energy waves with a fraction of the energy of a cell phone. Medical scientists do not consider the millimeter-wave machines a health risk.
Some researchers, even while acknowledging that the backscatter machines have few health risks, recommend greater use of the millimeter-wave scanners instead.