The body imaging X-ray machines (also known as backscatter machines) introduced last fall in airport security screenings quickly captured the public’s ire. While concerns have focused more on privacy, parents and frequent travelers have also raised questions about the amount of radiation they emit.
In the April issue of Radiology, two experts weigh in on the issue. David J. Brenner, director of the Center for Radiological Research at Columbia University Medical Center, notes that the individual risk of developing cancer from a round trip through the scanners is miniscule — about one in 10 million. But he expresses concern from a public health standpoint, wondering if it’s appropriate to expose any Americans to even a tiny risk, especially as radiation exposure is cumulative.
Similarly, David A. Schauer, executive director of the National Council on Radiation Protection and Measurements (NCRP), urges the government to ensure that the devices are tightly regulated and maintained for maximum public safety. “When a government concludes that security screening of people with backscatter X-rays is justified, then regulatory control should be implemented,” he writes.
Still, both experts emphasize that the machines need not cause alarm for all but the most frequent travelers — those who take hundreds of flights per year. It may be helpful for the average consumer to think about the machines in relation to those they’ve been exposed to in a doctor’s office setting. Like medical X-rays, backscatters use ionizing radiation to construct an image of the body. Ionizing radiation, unlike the non-ionizing kind emitted by cell phones and other wireless devices, has enough energy to break DNA and chemical bonds in the body.
“Backscatter X-rays have so low an energy that, if operated properly, they don’t penetrate the body — they only look at things on the surface. [Unlike medical X-rays], they don’t see bones,” says Dr. David Carpenter, director of the Institute for Health and the Environment at the University at Albany—SUNY.
In fact, the American College of Radiology noted, “A traveler would require more than 1,000 such scans in a year to reach the effective dose equal to one standard chest X-ray.” The NCRP concluded that it would take 100 trips through the device in a year’s time to accumulate what would be considered a “Negligible Individual Dose” of radiation.
Travelers should also take note that two different kinds of full-body scanners have been introduced in the security changes. The other kind, millimeter wave scanners, uses radio waves, not ionizing radiation, to form an image. Both Brenner and Schauer suggested that an eventual solution may be the broader implementation of these safer alternatives.
The bottom line? If faced with a choice, opt for the millimeter wave machine, but you needn’t endure a pat-down in the name of health.