Aviation securityScientists continue to raise doubts about safety of full body scanners

The controversy over the Transportation Security Administration’s (TSA) body scanners lingers on as scientists continue to question the safety of these devices, which expose thousands of people to trace amounts of radiation every day.

TSA officials maintain that their full body x-ray scanners are safe as they only expose individuals to negligible amounts of radiation, the equivalent of two minutes of flying. But despite these assurances, a group of five scientists recently sent an open letter to John Holdren, the White House Science advisor, questioning these assertions.

The scientists – who are professors at University of California, San Francisco (UCSF) and Arizona State University – argue that the tests used to validate TSA’s claims contain critical flaws, lack transparency, and have not been independently verified.

“There’s no real data on these machines, and in fact, the best guess of the dose is much, much higher than certainly what the public thinks,” said John Sedat, a professor emeritus in biochemistry and biophysics at UCSF and the primary author of the letter.

In the letter, the scientists note that the test results that the TSA cites come from a Johns Hopkins University lab which did not have access to the actual x-ray machine used at airports. Instead researchers were only able to observe as Rapiscan, the machine’s manufacturer, ran their own tests on a mock up model built using spare parts and configured to resemble the TSA machines.

In addition, the Johns Hopkins lab report was so “heavily redacted” that “there is no way to repeat any of these measurements.”

To bolster its case, TSA argues that the backscatter technology used in some of its body scanners has been evaluated by the Food and Drug Administration, the National Institute for Standards and Technology, and the John Hopkins University Applied Physics Laboratory.

TSA also says that it has deployed survey teams with radiation detectors at airports to check the machines. According to TSA, the results indicate that the body scanners do not pose a significant risk to public health.

Many scientists and radiation experts agree with TSA’s conclusions that the doses are so low that individuals would have to pass through the machines at least a thousand times before the exposure levels could be harmful.

But Professor Sedat and his team argue that “It is still unclear how much damage to cells occurs with low dose X-rays.” In particular, they worry that “potential X-ray damage, primarily to skin cells and adjacent tissues, would lead to a ‘damage response’ by the cells.”

A fellow UCSF faculty member, Rebecca Smith-Bindman, a radiologist, disagrees with Sedat’s medical findings, but still has qualms with how TSA is operating their machines.

In an article for the Archives of Internal Medicine, Smith-Bindman writes that the risks of airport body scanners are “truly trivial.” As an example, she says a passenger would have to undergo fifty airport scans to reach the level of a dental X-ray, 1,000 for a chest X-ray, and 4,000 for a mammogram.

She concludes, “There’s really unnecessary fear related to these scans.”

But what concerns Smith-Bindman is the lack of regulation and transparency regarding these machines.

“What I’m not as comfortable with is that there has not been access to these machines. They are not being tested on the same regulatory basis that we see on medical equipment,” she said.

Smith-Bindman’s request that she or a team of outside researchers test the machine was rebuffed by a TSA public affairs officer who said that allowing outsiders to have access to the machine could compromise national security.

Before the House Committee on Oversight and Government, Robin Kane, TSA’s assistant administrator for security technology, reiterated the agency’s insistence on keeping third-party researchers from testing the body scanners because if it did, it would expose sensitive information that the agency does not normally share with the public.

But Kane said that if the tests were set up in a secure manner, the agency would allow more testing.

In the meantime, the controversy will likely continue until proper tests can be run by medical researchers that will give undisputable scientific evidence to settle this debate once and for all.