Scientists Cast Doubt on TSA Tests of Full-Body Scanners
A sign at a Transportation Security Administration (TSA) checkpoint instructs passengers about the use of the full-body scanner at O'Hare International Airport on March 15, 2010 in Chicago, Ill. (Scott Olson/Getty Images)
The Transportation Security Administration says its full-body X-ray scanners are safe and that radiation from a scan is equivalent to what's received in about two minutes of flying. The company that makes them says it's safer than eating a banana [1].
But some scientists with expertise in imaging and cancer say the evidence made public to support those claims is unreliable. And in a new letter [2] sent to White House science adviser John Holdren, they question why the TSA won't make the scanners available for independent testing by outside scientists.
But some scientists with expertise in imaging and cancer say the evidence made public to support those claims is unreliable. And in a new letter [2] sent to White House science adviser John Holdren, they question why the TSA won't make the scanners available for independent testing by outside scientists.
The machines, which are designed to reveal objects hidden under clothing, have the potential to close a significant security gap for the TSA because metal detectors can't find explosives or ceramic knives, which can be just as sharp as the box cutters that hijackers used on 9/11.
They are also important for TSA's public relations battle over the alternative, the "enhanced pat-down," which has bred an epidemic of viral videos: A 6-year-old girl [3] is touched from head to toe. A former Miss USA [4] says she was violated. A software programmer warns a screener, "If you touch my junk [5], I'm going to have you arrested."
After the underwear bomber tried to blow up a Northwest Airlines plane on Christmas Day 2009, the TSA ramped up deployment of full-body scanners and plans to have them at nearly every security line by 2014.
There are two types of body scanners [6]. Millimeter wave machines emit a radio frequency similar to cellphones. Backscatters work like a fast-moving X-ray. In the latter, the rays bounce off the skin and create a fuzzy white image [7] of the passenger's body. Because the beam doesn't go through the body, most of its radiation is received by the skin.
The TSA says the backscatter technology has been evaluated by the Food and Drug Administration [8], the National Institute for Standards and Technology [9] and the Johns Hopkins University Applied Physics Laboratory [10]. Survey teams are using radiation-detecting dosimeters to check the machines at airports. The TSA says the results have all confirmed that the scanners don't pose a significant risk to public health.
According to the agency and many radiation experts, the dose is so low, even for children or cancer patients, that someone would have to pass through the machines more than a thousand times before approaching the annual limit set by radiation safety organizations.
But the letter to the White House science adviser, signed by five professors at University of California, San Francisco, and one at Arizona State University, points out several flaws in the tests. Studies published in scientific journals in the last few months have also cast doubt on the radiation dose and the machines' ability to find explosives.
A number of scientists, including some who believe the radiation is trivial, say more testing should be done given the government's plans to put millions of passengers through the machines. And they have been disturbed by the TSA's reluctance to do so.
"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.
The same group stirred controversy last year when it sent a letter to Holdren [11] arguing that while the overall dose to the body may be low, the TSA hadn't quantified the dose to the skin. Last fall, FDA and TSA officials released a study [12] that estimated the dose to the skin to be twice the dose to the body, though still extremely low.
In the most recent letter sent to Holdren on April 28, the professors note that the Johns Hopkins lab didn't test an actual airport machine. Instead, the tests were done on a model built by the manufacturer, Rapiscan [13], and configured to resemble a system previously tested by the TSA.
The researchers' names have been kept secret, and the report on the tests is so "heavily redacted" that "there is no way to repeat any of these measurements," they wrote.
The physics and medical professors also took issue with the device used to measure the radiation. Although the device, known as an ion chamber, is commonly used to test medical equipment, they argue that the detector gets overwhelmed by the amount of radiation the backscatter deposits in a short time and might not provide accurate readings.
Helen Worth, a spokeswoman for the Johns Hopkins lab, referred questions to the TSA.
Part of the trouble is that there is no ideal device for measuring the radiation dose given by backscatter X-rays, said David Brenner, director of the Columbia University Center for Radiological Research. The machines emit a pencil beam that rapidly moves across and up and down the body, he said.
"We are one of the oldest and biggest radiological research centers in the country, and we find this to be a very hard technical problem," said Brenner, who was not involved with the letter.
Another issue is that there is a lot of uncertainty with the model used to estimate cancer risk from radiation exposure to the skin, said Rebecca Smith-Bindman, a UCSF radiologist who also was not involved in the letter.
Smith-Bindman, who has testified before Congress about excessive radiation from medical scans, studied the TSA reports and said she wasn't concerned about the airport X-rays.
The risks are "truly trivial," she wrote in an article [14] for the Archives of Internal Medicine. A passenger would have to undergo 50 airport scans to reach the level of a dental X-ray, 1,000 for a chest X-ray, and 4,000 for a mammogram.
Though imperfect, the available models predict that the backscatters would lead to only six cancers over the course of a lifetime among the approximately 100 million people who fly every year, Smith-Bindman concluded.
"There's really unnecessary fear related to these scans," she said. "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."
After her article was published, Smith-Bindman was contacted by a TSA public affairs officer. During the conversation, she suggested that she or other outside scientists be allowed to test the machine. The official was shocked by the suggestion and said such access could tip off people who want to avoid detection, Smith-Bindman said.
"It was not appreciating that there's legitimate scientific questions that have to be balanced against the security questions," she said.
The TSA did not respond to ProPublica's questions about why it wouldn't allow outside testing. But at a congressional hearing [15] in March, Robin Kane, assistant administrator for security technology, said doing so would expose a lot of sensitive information the agency wouldn't normally share publicly. The machines had already been tested several times, he said, and if set up securely, the agency would allow more testing.
The available information leaves scientists with little to work with. Peter Rez, the Arizona State physics professor who signed the letter to Holdren, has tried to calculate the radiation by examining the handful of backscatter images that have been released publicly.
The Electronic Privacy Information Center [16], a civil liberties group, sued the Department of Homeland Security, TSA's parent agency, in federal court seeking release of 2,000 backscatter images used in testing. But it has not been successful.
The few images that have been made public do not reveal faces or detailed private features. The TSA says the images Rez used are out of date, but Rez says the current image on TSA's website is unusable.
Using the earlier images, Rez concluded [17] in the Radiation Protection Dosimetry journal that it was highly unlikely the machines could have produced such high-quality images with doses of radiation as low as those described by TSA. He estimated the dose, while still very small, is 45 times higher than the results measured by Johns Hopkins.
Applying Rez's numbers, Brenner wrote a paper [18] for the journal Radiology, estimating that 100 additional cancers would develop for every 1 billion scans.
For Rez, the real danger occurs if the machine stops in the middle of a scan, allowing the beam to focus on a tiny area for several seconds. Given that the backscatter works with a wheel rotating at a high speed, and that the agency plans to use the scanners continuously 365 days a year, mechanical failures are likely, he said.
The TSA says that the scanners have safety systems, such as automatic shutoffs and emergency stop buttons, that will kill the beam in the event of any problem that could result in abnormal radiation. How those fail-safe systems work isn't entirely clear.
When Johns Hopkins researchers visited the Rapiscan facility, the automatic termination appeared to work. But the full results of the shutoff tests are redacted.
What's more, the test system didn't have an emergency stop button.
They are also important for TSA's public relations battle over the alternative, the "enhanced pat-down," which has bred an epidemic of viral videos: A 6-year-old girl [3] is touched from head to toe. A former Miss USA [4] says she was violated. A software programmer warns a screener, "If you touch my junk [5], I'm going to have you arrested."
After the underwear bomber tried to blow up a Northwest Airlines plane on Christmas Day 2009, the TSA ramped up deployment of full-body scanners and plans to have them at nearly every security line by 2014.
There are two types of body scanners [6]. Millimeter wave machines emit a radio frequency similar to cellphones. Backscatters work like a fast-moving X-ray. In the latter, the rays bounce off the skin and create a fuzzy white image [7] of the passenger's body. Because the beam doesn't go through the body, most of its radiation is received by the skin.
The TSA says the backscatter technology has been evaluated by the Food and Drug Administration [8], the National Institute for Standards and Technology [9] and the Johns Hopkins University Applied Physics Laboratory [10]. Survey teams are using radiation-detecting dosimeters to check the machines at airports. The TSA says the results have all confirmed that the scanners don't pose a significant risk to public health.
According to the agency and many radiation experts, the dose is so low, even for children or cancer patients, that someone would have to pass through the machines more than a thousand times before approaching the annual limit set by radiation safety organizations.
But the letter to the White House science adviser, signed by five professors at University of California, San Francisco, and one at Arizona State University, points out several flaws in the tests. Studies published in scientific journals in the last few months have also cast doubt on the radiation dose and the machines' ability to find explosives.
A number of scientists, including some who believe the radiation is trivial, say more testing should be done given the government's plans to put millions of passengers through the machines. And they have been disturbed by the TSA's reluctance to do so.
"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.
The same group stirred controversy last year when it sent a letter to Holdren [11] arguing that while the overall dose to the body may be low, the TSA hadn't quantified the dose to the skin. Last fall, FDA and TSA officials released a study [12] that estimated the dose to the skin to be twice the dose to the body, though still extremely low.
In the most recent letter sent to Holdren on April 28, the professors note that the Johns Hopkins lab didn't test an actual airport machine. Instead, the tests were done on a model built by the manufacturer, Rapiscan [13], and configured to resemble a system previously tested by the TSA.
The researchers' names have been kept secret, and the report on the tests is so "heavily redacted" that "there is no way to repeat any of these measurements," they wrote.
The physics and medical professors also took issue with the device used to measure the radiation. Although the device, known as an ion chamber, is commonly used to test medical equipment, they argue that the detector gets overwhelmed by the amount of radiation the backscatter deposits in a short time and might not provide accurate readings.
Helen Worth, a spokeswoman for the Johns Hopkins lab, referred questions to the TSA.
Part of the trouble is that there is no ideal device for measuring the radiation dose given by backscatter X-rays, said David Brenner, director of the Columbia University Center for Radiological Research. The machines emit a pencil beam that rapidly moves across and up and down the body, he said.
"We are one of the oldest and biggest radiological research centers in the country, and we find this to be a very hard technical problem," said Brenner, who was not involved with the letter.
Another issue is that there is a lot of uncertainty with the model used to estimate cancer risk from radiation exposure to the skin, said Rebecca Smith-Bindman, a UCSF radiologist who also was not involved in the letter.
Smith-Bindman, who has testified before Congress about excessive radiation from medical scans, studied the TSA reports and said she wasn't concerned about the airport X-rays.
The risks are "truly trivial," she wrote in an article [14] for the Archives of Internal Medicine. A passenger would have to undergo 50 airport scans to reach the level of a dental X-ray, 1,000 for a chest X-ray, and 4,000 for a mammogram.
Though imperfect, the available models predict that the backscatters would lead to only six cancers over the course of a lifetime among the approximately 100 million people who fly every year, Smith-Bindman concluded.
"There's really unnecessary fear related to these scans," she said. "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."
After her article was published, Smith-Bindman was contacted by a TSA public affairs officer. During the conversation, she suggested that she or other outside scientists be allowed to test the machine. The official was shocked by the suggestion and said such access could tip off people who want to avoid detection, Smith-Bindman said.
"It was not appreciating that there's legitimate scientific questions that have to be balanced against the security questions," she said.
The TSA did not respond to ProPublica's questions about why it wouldn't allow outside testing. But at a congressional hearing [15] in March, Robin Kane, assistant administrator for security technology, said doing so would expose a lot of sensitive information the agency wouldn't normally share publicly. The machines had already been tested several times, he said, and if set up securely, the agency would allow more testing.
The available information leaves scientists with little to work with. Peter Rez, the Arizona State physics professor who signed the letter to Holdren, has tried to calculate the radiation by examining the handful of backscatter images that have been released publicly.
The Electronic Privacy Information Center [16], a civil liberties group, sued the Department of Homeland Security, TSA's parent agency, in federal court seeking release of 2,000 backscatter images used in testing. But it has not been successful.
The few images that have been made public do not reveal faces or detailed private features. The TSA says the images Rez used are out of date, but Rez says the current image on TSA's website is unusable.
Using the earlier images, Rez concluded [17] in the Radiation Protection Dosimetry journal that it was highly unlikely the machines could have produced such high-quality images with doses of radiation as low as those described by TSA. He estimated the dose, while still very small, is 45 times higher than the results measured by Johns Hopkins.
Applying Rez's numbers, Brenner wrote a paper [18] for the journal Radiology, estimating that 100 additional cancers would develop for every 1 billion scans.
For Rez, the real danger occurs if the machine stops in the middle of a scan, allowing the beam to focus on a tiny area for several seconds. Given that the backscatter works with a wheel rotating at a high speed, and that the agency plans to use the scanners continuously 365 days a year, mechanical failures are likely, he said.
The TSA says that the scanners have safety systems, such as automatic shutoffs and emergency stop buttons, that will kill the beam in the event of any problem that could result in abnormal radiation. How those fail-safe systems work isn't entirely clear.
When Johns Hopkins researchers visited the Rapiscan facility, the automatic termination appeared to work. But the full results of the shutoff tests are redacted.
What's more, the test system didn't have an emergency stop button.
- http://articles.latimes.com/2010/nov/22/business/la-fi-1123-scanner-maker-20101123
- http://www.propublica.org/documents/item/april-2011-letter-to-john-holdren
- http://www.youtube.com/watch?v=-3sH1GaO_nw
- http://www.susiecastillo.net/blog/2011/4/25/my-tsa-pat-down-experience.html
- http://www.youtube.com/watch?v=-UqM56e-kRA
- http://www.tsa.gov/approach/tech/ait/how_it_works.shtm
- http://www.tsa.gov/graphics/images/approach/backscatter_large.jpg
- http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/SecuritySystems/ucm227201.htm#2
- http://www.tsa.gov/assets/pdf/rapiscan_secure_1000.pdf
- http://www.tsa.gov/assets/pdf/jh_apl_v2.pdf
- http://www.whitehouse.gov/sites/default/files/microsites/ostp/ucsf-jph-letter.pdf
- http://www.whitehouse.gov/sites/default/files/microsites/ostp/fda-backscatter-response.pdf
- http://www.rapiscansystems.com/
- http://archinte.ama-assn.org/cgi/content/abstract/archinternmed.2011.105
- http://oversight.house.gov/index.php?option=com_content&view=article&id=1199%3A3-16-11-qtsa-oversight-part-i-whole-body-imagingq&catid=17&Itemid=25
- http://epic.org/privacy/airtravel/backscatter/
- http://rpd.oxfordjournals.org/content/early/2010/11/09/rpd.ncq358
- http://radiology.rsna.org/content/259/1/6.full.pdf+html?sid=0f65bb4b-b6f9-49e5-af10-635cfa700131
- http://www.twitter.com/MichaelGrabell
38 comments
Today, 3:03 p.m.
Today, 3:28 p.m.
Today, 3:42 p.m.
Today, 4:40 p.m.
Such as how poorly they work and unsafe their radiation levels are?
Rev. Ortiz: Last I checked, the Bible had something to say about bearing false witness.
Today, 5:32 p.m.
It seems to me that if Israel rejected this technology for their airports, maybe we should look into their airport security. But then again, we probably do not have ex-government officials sitting on the board to those potential companies like we had with this backscatter manufacturer!
Today, 5:34 p.m.
Today, 5:42 p.m.
The difference in wavelength is so great (three orders of magnitude) that it is not possible to conclude anything about the risks of exposure to millimeter-waves based on what we know about cell phone exposure.
Today, 5:51 p.m.
Everything TSA does at the airport is a waste of their time and your money.
Today, 6:06 p.m.
Today, 6:15 p.m.
Today, 6:20 p.m.
FOLLOW THE MONEY and it always leads back to the crooks, the Dems.
Today, 6:25 p.m.
They used to tell us that the dental xrays were safe too and so are mamograms. But now it turns out that mamograms may actually be causing breast cancers.
Radiation is cumulative. Machines are not always calibrated the same. Governments lie. Sorry but I have been opting for a manual pat down.
Today, 6:46 p.m.
For more info on the accumulative effects of x-rays google “radiation treatment for thymus in the 60’s”
If these machines were truly safe, they would allow them to be tested.
Today, 6:52 p.m.
Next time at an airport watch for employees going to work using their id card to open secure doors. See if a TSA guard is checking their id or preventing four people from entering with one id card.
TSA security is a joke.
Today, 7:01 p.m.
Today, 7:07 p.m.
Today, 7:18 p.m.
To the editor;
Recently the United States suffered yet another attempted act of war from a terrorist acting on the misguided notion of jihad. This fellow evaded airport security, then while seated on the aircraft attempted to detonate a bomb in addition to the fuel tank positioned below him. The jihadist’s failure was a result of a lack of preparation; neither his will nor our efforts to keep him off the plane did anything to ameliorate his plans. This jihadist, like many who have attacked this nation in the past, are men educated in mind and not in morals, and as such are a menace to civil society, and must be stopped at any cost. After thirty years of the free world trying to stop various forms of jihad we are no closer to stopping the next attack because the ideology that creates the next radical Islamic terrorist still exists; so long as it exists we will neither have peace nor security - nothing short of a regional war that redraws the boundaries of countries in the middle east will bring us the opportunity of lasting peace. Nazi Germany and Imperial Japan did not alter their evil plans upon the sight of a TSA agent. That said; a small suggestion.
If an airline operated a system akin to how credit card companies detect fraud, in the atmosphere of airport security, what would that look like? Might a pre-flight approval system consist of various credentials already in a citizens possession; a system for non-citizens would perform the same function of verification with cross referenced forms of identification, the elimination of the option of using cash to purchase a ticket, and the elimination of purchasing a ticket without being pre-qualified to do so in the first place. In addition, the airline would be responsible for all security; remember the $50 Billion per year TSA could not stop this jihadist, and frankly in a world where people willingly swallow prophylactics filled with narcotics to breech our drug laws, the TSA will not stop the next one; an airline that is one hundred percent responsible for the occupants and operation of the aircraft can and will. They will have the ability to reject people who do not meet their flight criteria identity policy in a way that the TSA is forbidden from doing. The profit driven airline can drive the innovation that will be required to detect individuals whose behavior is suspicious even before a ticket is purchased by combing the data points that separate out frequent travelers from those that have never flown, or are traveling in a manner not consistent with past patterns, and thus require more scrutiny at security checkpoints prior to boarding the plane.
It is almost treasonous that after so many kicks to our collective complacency we are still only fighting the last battle, and not the next one. Securing an aircraft is best left up to the airline and the crew of the airplane, and not the federal government. The private airline possesses the incentive to maintain the safety of the airplane that the TSA and the rest of the security apparatus lacks. The federal government lacks the economic incentive to do a quality job, but the private airline is nimble and can evolve the policies and procedures the government is not permitted or politically unable to do. The current setup seems to serve only one purpose - to avoid responsibility for anything at all, in that atmosphere you can bet we are going to lose much more then an airliner in the future. The radical Islamic threat from 1979 to 2010 has grown stronger, and developed a greater reach into the west then our side has developed a defense or plan to defeat; we are fooling ourselves if we think a watch list, that no one even bothers to check, is anything more than a placebo for the cancerous philosophy of radical Islam.
Today, 7:20 p.m.
Today, 7:33 p.m.
Today, 7:34 p.m.
> potential to close a significant security gap for the TSA because metal detectors can’t find explosives or ceramic knives, which can be just as sharp as the box cutters that hijackers used on 9/11.
The hijackers on 9/11 didn’t carry any knives or box cutters aboard. The box cutters were already there. DHS/TSA has done nothing to determine who put them there or prevent cargo/staff from doing it again.
Harassing 100% of airline passengers has done nothing to increase security.
Cancer risk aside, the “we’ll take over an airplane” attack vector is 10 years old an unlikely to be duplicated. Congress has outspent its budget and the US has hit its debt ceiling and STILL the TSA goons fondle toddlers and want to see us naked—while we take billions of dollars of our tax dollars to pay for this Security Theater.
No security here. Nothing to see. Move along now, Sir. I SAID, Move along now sir, or I’ll arrest you. Land of the free.
Mark
Today, 7:35 p.m.
Today, 7:56 p.m.
Consider that the absorption is entirely within an inch of the surface. How does it work? The incoming x-ray photon interacts with an atom in the kid’s testicle, ejecting a high energy electron and producing a “new” photon which heads back to the detectors mounted alongside the x-ray source. That’s the “backscatter” photon.
Meanwhile, the electron, the high energy Compton electron, loses energy by several energetic collisions with the molecules in the cells of the kid’s testicle. That includes DNA molecules.
It’s absolutely the wrong place and the wrong time of life for this to happen. I’m astonished this isn’t be shouted from the rooftops. Where is the data? Where are the studies?
And while I’m on this, where are the studies regarding melanoma production in mice subjected to these very soft x-rays, which are filtered out of dental x-rays to avoid skin damage.
Today, 8:34 p.m.
The may have some crack up their skirts.
Today, 8:47 p.m.
Today, 9:38 p.m.
Any threat is more threat than they have prevented or will likely ever prevent.
Today, 10:16 p.m.
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Drop the political correctness and start profiling passengers now or wait hundreds of passengers are blow out of the sky and then start profiling.
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What about those TSA employees that are standing around that machine for an 8 hour shift (day in, day out)?
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