The backscatter X-ray scanners being used by the Transportation Security Administration (TSA) in airports security checkpoints could represent a risk to health, say researchers.
David Brenner, director of the Center for Radiological Research at Columbia University Medical Center, says that with up to a billion such scans per year, there could be long-term consequences for public health.
"The risks for any individual going through the X-ray backscatter scanners are exceedingly small," he says. "However, if all air travelers are going to be screened this way, then we need to be concerned that some of these billion people may eventually develop cancer as a result of the radiation exposure from the X-ray scanners."
In a separate article in Radiology, David Schauer, executive director of the National Council on Radiation Protection and Measurements (NCRP), argues that the risks are low, compared with others that are accepted every day.
"There is no scientific basis to support the notion that a small risk to an individual changes in any way for that individual as others around him are also exposed to the same source of radiation," he says.
"Critics of security screening acknowledge that doses from backscatter X-ray systems are very low and safe for an individual."
However, Schauer believes there should be strict regulatory control of the backscatter scanners to keep them compliant with the goals of radiation protection - justification (benefits exceed cost or harm), optimization (exposures are kept as low as reasonably achievable) and limitation (individual doses are limited).
"Any decision that alters the radiation exposure situation should do more good than harm," says Schauer. "In other words, people should only be exposed to ionizing radiation for security screening purposes when a threat exists that can be detected and for which appropriate actions can be taken. In addition, exposures must be justified and optimized."
Both scientists agree that the scanners using millimeter wave technology should be considered as a first option, since they are similar in cost and functionality to the backscatter machines, but don't expose passengers to ionizing radiation.
"As someone who travels just occasionally, I would have no hesitation in going through the X-ray backscatter scanner," Dr. Brenner said. "Super frequent fliers or airline personnel, who might go through the machine several hundred times each year, might wish to opt for pat-downs."