Senators seek more study of whole body x-ray airport scanner safety

Three U.S. senators have joined the debate over the safety of x-ray based whole-body airport scanners, asking federal officials to review scanner health effects on travelers and airport and airline personnel.

In an Aug. 5 letter to Janet Napolitano, secretary of Homeland Security, and John S. Pistole, administrator of the Transportation Security Administration (TSA), the senators note public concerns about the safety of the scanners and asked to be provided all government-commissioned evaluations of the health effects of radiation emitted by this technology.

The letter was signed by Sens. Susan Collins (R-ME), ranking member of the Senate Homeland Security Committee, Tom Coburn (R-OK), and Richard Burr (R-NC).

“To address the continuing concerns surrounding the use of these machines, we request that you have the (Homeland Security) department’s chief medical officer, working with independent experts, conduct a review of the health effects of their use for travelers, TSA employees, and airport and airline personnel,” they said.

The letter comes as the TSA is moving ahead with purchases of backscatter and millimeter wave scanners for installation in the nation’s airports. According to a July 26 report in The New York Times, the TSA had purchased 250 of the backscatter x-ray units and was on track to have both the x-ray and an alternative millimeter wave scan technology installed at 2200 checkpoints in 450 commercial airports in the U.S. within two years.

“The issue of radiation associated with the backscatter x-ray (advanced imaging technology) machines has not been adequately addressed by TSA,” the letter said. It called the article in The New York Times “only the most recent in a number of media reports on concerns over the radiation emitted by backscatter x-ray (advanced imaging technology) machines.”

The Department of Homeland Security has received the letter and will be responding to the senators, said Greg Soulet, a TSA spokesman.

Issues raised in the letter dovetail with some of those raised by critics of the scanner program, among them Leon Kaufman, Ph.D., a retired physicist and professor emeritus at the University of California, San Francisco, who complained that the TSA and scanner advocates have never adequately explained the methodology behind their dose calculations. In a Feb. 9 article for Diagnostic Imaging, Kaufman noted radiation risks and asked whether the TSA x-ray scanner program amounted to a “a great public health experiment.”

Among the difficulties in evaluating the health effects of backscatter x-rays is that the individual risk may be negligible, but on a public health basis, there could be could be cases of cancer associated with their use.

David J. Brenner, Ph.D., director of Columbia University’s Center for Radiological Research, has also voiced caution about x-raying millions of air travelers. He was a member of the government committee that set the safety guidelines for the x-ray scanners in 2003.

When that report was issued, the anticipation was that the x-ray scanners would be secondary devices, reserved for those who were suspicious, or perhaps used on a random basis, instead of being used on all travelers, Brenner said.

The individual risk is very small. But if you multiply this risk by the number of people going through scanners, you are likely to have health consequences, although it is very difficult to determine exactly what those consequences are, he said.

“The classic problem in low-dose radiological epidemiology is that 20% of us die of cancer,” Brenner said. “You’re looking at a tiny increase and it’s difficult to determine.” In a sense, the “great public health experiment” is already under way, he said.

If there is a risk from the x-ray scanners, it can be balanced against the risk of an undetected bomb blowing up an airliner. But if there’s another technology, such as the millimeter wave scanner, that achieves the same goal with no bioeffects, using that instead could improve the risk/benefit balance, Brenner said. (A theoretical bioeffect from millimeter waves was suggested by Los Alamos researchers, but disputed by Brenner.)

As for the x-ray scanners, the greatest risk is probably from skin exposure, an issue raised in an April 6 letter from four UCSF scientists to Dr. John P. Holdren, an assistant to President Obama for science and technology.

“These are very low-energy x-rays, so they go a few millimeters through the skin. That’s the only real concern,” Brenner said. “Basal cell carcinoma is promoted quite efficiently by radiation, so the worry about skin is right on. Most are on the head and neck. You could avoid exposing the head and neck because the scan is done with a pencil beam. If you didn’t scan the head and neck, the risk would go down markedly.”