Prof. John Sedat On DHS’ X-ray Scanners: ‘Society Will Pay A Huge Price In CANCER Because Of This’

Rez says the name that Homeland Security has picked for its border scanners–“Low Energy Drive Through Portal Non-Intrusive Inspection Systems”–is highly misleading. “To call anything based on high energy X-rays ‘low energy’ is worse than 1984 doublespeak” because radiation emitted by the scanners “goes right through the person” sitting in a vehicle, he says. (High energy X-rays can penetrate not only human flesh, but steel plates that are multiple centimeters thick.)

For its part, Homeland Security says the dose is safe and based on commonly accepted government standards (PDF) established by the National Council on Radiation Protection and Measurement, which would permit 2,500 scans a year for each person. CBP’s specifications also require the manufacturer to “perform an evaluation of the potential effect of radiation exposure on public safety on the proposed system.” In addition, a CBP representative told CNET that the machines are currently only used in secondary inspections (most people go through just the primary inspection).

But Homeland Security did not respond, citing insufficient time, to a list of questions that CNET posed on Wednesday evening asking about independent testing that has been performed on the scanners that would measure the actual dose of radiation emitted. In the case of its airport scanners, Homeland Security’s Transportation Security Administration initially promised to conduct such an analysis, but then backtracked, prompting criticism last fall from Sen. Susan Collins, a Maine Republican.

The dispute about radiation during border scans generally parallels the one about airport X-ray scanners, with Homeland Security saying they’re safe, and researchers raising concerns that no independent testing has been done. A letter (PDF) that UCSF’s Sedat and others sent the Department of Health and Human Services last year says that independent tests have not “been adequately performed for X-ray scanners, leaving us in a situation where a major untested technology is being used on a large segment of our population, and where any damage may not be apparent immediately, or recognized to be caused by the extra radiation exposure–an unprecedented state of affairs.”

And the privacy concerns, too, are similar. Homeland Security’s TSA says it “takes all measures to ensure passenger privacy” at airports. Its new “advanced imaging” millimeter wave machines at airports, which don’t use ionizing radiation, do not display body outlines.

“They’re potentially the same kind of images as people in airports,” Ginger McCall, director of EPIC’s open government program, says of the border scanners. They’re also “capturing images of people essentially naked,” she says.

The origin of the scanners can be traced back to a not-so-obvious source: President Obama’s signature American Recovery and Reinvestment Act of 2009, better known as the stimulus bill. That awarded a $27.3 million contract to American Science and Engineering, or AS&E, to build 35 scanners, according to a description at Recovery.gov. Soon afterward, X-ray scanners appeared at the San Ysidro, Calif., checkpoint, sometimes called the world’s busiest land crossing; other locations listed in the specification include El Paso, Texas, Columbus, N.M., and Nogales, Ariz.

Now Homeland Security wants more. The U.S. government convened a “pre-solicitation conference” in Washington, D.C., on November 29, 2011, according to a public procurement document. Another document says “Customs and Border Protection is very appreciative of all the responses received” and plans to publish a formal request for proposals for the next purchase on February 1.

AS&E, a publicly-traded company based in Billerica, Mass., boasts on its Web site that its Z Portal vehicle screening system can conduct “imaging from three sides simultaneously,” and that “one scan is equivalent to flying one minute at altitude on an airplane.”

Sedat, the biophysicist, says that the estimates of X-ray radiation dosage from AS&E and CBP are likely to be in error by several orders of magnitude because of the equipment they’re using. He says: “If you have a laser pointer that you use for slides, it’s a very bright beam. It’s very hard to measure because it overwhelms a normal detector. You’ll saturate the detector and you’ll get the wrong answer. It could well come up with zero, or close to zero. And that’s not right. It’s not designed for handling that. The same is true for the ionization chambers they’re using (as detectors).”

Rez, the physics professor, says the problem with X-ray scanners is that as the resolution increases, the corresponding dose leaps upward as well–and that AS&E’s resolution has increased to approximately 5 millimeters. Another problem, he says, is failures: because the scan is conducted by having the vehicle move, if it stops in mid-scan, the radiation concentrated on one place would be above acceptable limits. “The energies are about three times the average energy in CT,” he says, meaning an X-ray computed tomography scan.

A paper that (PDF) Rez and two-co-authors published in the journal Radiation Protection Dosimetry concludes that “serious consideration should be given to the possibility of unintended and unnecessary doses to passengers due to malfunctioning equipment.”