The Department of Homeland Security has ordered the TSA to instruct traveling patrons that the naked body scanners do not emit ionizing radiation, or that it’s “millimeter wave technology”, or that emits radiation so low that it has no effect on giving passengers cancer or health problems. Passengers who opt out of a naked body scan have been routinely insulted by TSA bag checkers for being ignorant to assume the equipment emits any radiation at all. However, new scans of the equipment typically used at airports in the USA show radiation at ten times the acceptable limit.

Before we get into the technical details, let’s define several terms. Effects of radiation on human tissue is measured in sieverts (Si). A sievert is the most modern attempt to quantitatively evaluate the biological effects of ionizing radiation, as opposed to the physical aspects, which are characterized by the absorbed dose, measured in gray. In other words, gray measures absorbed radiation which is absorbed into any material whereas the unit sievert specifically measures absorbed radiation which is absorbed by a person. A mathematical algorithm is used to determine factors like what type of radiation, what kind of tissue it is exposed to, how much of that radiation and how much tissue is present, etc. The unit sievert is so small that it is typically measured in multiples of millisieverts (mSv) or microsieverts (μSv).

In the USA, there are set standards of what is considered “acceptable” levels of radiation, based off a risk model that evaluates “background radiation” (radiation that is constantly present in the environment and is emitted from a variety of natural sources like sunlight or cosmic radiation, and artificial sources like a light bulb or a computer monitor) humans are exposed to on a daily basis. In the USA, the maximum allowable or “acceptable” limit of external exposure to radiation is 1 mSv/yr (one millisievert a year).

Other figures you might find interesting about mSv:

A mammogram exposes a person to 3 mSv

A chest CT scan exposes a person to 6-18 mSv

 

 

The TSA employs the use of two primary units for scanning passengers to look for bombs hidden in their underwear or tucked away in their private parts. The units scan past the clothes to reveal what is underneath.

 

Millimeter Wave Unit

TSA claims the millimeter wave technology bounces electromagnetic waves off the body to create a black and white three-dimensional image similar to this one:

The electromagnetic waves are similar to the type of radiation emitted by cell phones. Whether or not cell phone radiation can increase the risk of cancer is still debated today.

 

 

 

Back Scatter Unit

 

The Back Scatter units project X-ray beams over the body to create a reflection of the body displayed on the monitor like this image:

Backscatter technology is based on the X-ray compton scattering effect of X-rays, a form of ionizing radiation. Unlike a traditional X-ray machine which relies on the transmission of X-rays through the object, backscatter X-ray detects the radiation that reflects from the object and forms an image. The backscatter pattern is dependent on the material property, and is good for imaging organic material. In contrast to millimeter wave scanners which create a 3D image, backscatter X-ray scanners will typically only create a 2D image. For airport screening, images are taken from both sides of the human body. Backscatter X-ray was first applied in a commercial low dose personnel scanning system by Dr. Steven W. Smith. Dr. Smith developed the Secure 1000 whole body scanner in 1992 and then sold the device and associated patents to Rapiscan Systems who now manufactures and distributes the device.

According to a draft standard on the United States FDA website, the allowable dose from a scan would be 0.1 μSv, and that report uses a model whereby a 0.01 μSv dose increases an individual’s risk of death by cancer during his or her lifetime by 5×10−10. Since the dose limit is ten times higher than 0.01 μSv, the most conservative model would predict one additional cancer death per 200 million scans. Since the airports in the UK handled 218 million passengers in 2009, if all passengers in the UK were scanned at the maximum dosage, then each year this would produce on average one additional cancer death (since there would be 200 million scans per year that the scanners were in operation), though usually each death would not occur in the same year as the particular scan that caused it, since the cancer may take years to grow. In addition, additional people would be given cancer but would die from other causes. That means all governments deem it okay for people to die of being bathed in ionized radiation to see if they might be “terrorists”.

In a groundbreaking story reported by USA Today, Reuters and Wired, reports radiation from the two primary scanning devices are in fact emitting ionizing radiation ten times the acceptable limit per scan. The USA Today article begins with the following: “The Transportation Security Administration announced Friday that it would retest every full-body X-ray scanner that emits ionizing radiation — 247 machines at 38 airports — after maintenance records on some of the devices showed radiation levels 10 times higher than expected.”

After the results from the contractors went public, TSA quickly went into damage control by blaming the stupidity of their highly trained and qualified contractors not being able to divide, or read simple instructions. The Reuters article explained it this way: “You see, the TSA says the enormous radiation reading came about when technicians, who normally check the output of a machine 10 times in a row, forgot to divide the total output by 10.” They they must be right, I mean look at how difficult and technical this post-scandal, public relations appropriate form looks!

The contractors mysteriously could neither be found for a comment, nor was there any explanation of how the measuring process was conducted. In addition, based on the Rapiscan form above, no proper explanation was offered as to why the TSA insists on re-evaluating readings ten times higher than zero. Rather, the TSA sternly scolded the mystery contractors publicly, kept their identity hidden and were ordered to go back an re-scan all the machines in question, then later claimed on their own website the terrible results was proof the machines are safe!!!

“These reports confirm that each piece of technology reviewed meets all national safety standards. However, during TSA’s review of these reports, inaccuracies were identified in contractor reporting that affected the documentation of some of the test results. These inaccuracies included:

• Lack of notation for the latest calibration date for the machine being tested or the most recent calibration date noted had expired on survey meters
• Information missing regarding warning labels and required labels
• Calculation errors not impacting safety
• Missing survey point readings
• Inconsistent responses to survey questions
• No reading of background radiation noted
• Missing other non-measurement related information

TSA took immediate action to hold contractors accountable, including directing the contractors to re-test each backscatter imaging technology unit, as well as re-testing any other unit with an inaccurate report, by the end of March 2011.”

None of this might have been made public, however, if not for pressure from USA Today and members of Congress. On December 7, 2010 USA Today reported on scanner radiation concerns of both the Centers for Disease Control and Prevention and TSA employees; it had already requested that the TSA release the inspection reports for all its X-ray scanners, which at the time the TSA kept secret because of the embarrassingly high radiation readings. Reps. Ed Markey (D-Mass.), John Dingell (D-Mich.), and Jason Chaffetz (R-Utah) all called for more openness from the TSA regarding the safety of its scanners. Three days later the agency began reviewing its maintenance reports, whereupon it discovered the “alleged errors”. It is now in the process of releasing the results of its review for all 4,500 airport X-ray devices, including the 247 backscatter machines, all of which it is retesting as a result of its findings. It is also, according to USA Today, requiring maintenance contractors to “retrain personnel involved in conducting and overseeing the radiation survey process.”