Civil Liberties

Worried the TSA Body Scanners Will Give You Cancer? Don't.

You'll get more radiation from traveling in an airplane. But there are plenty of other reasons to hate the scanners.

So a terrorist snuck by airport security whilst wearing explosive panties, and now your country has completely freaked out, and airports want to install full-body scanners that use radiation to see your naughty bits.

What's a concerned citizen to do?

Let's put aside the potential civil rights violations at play in such searches (there are many). Let's also forget that TSA agents photographing the naked bodies of Muslims might be -- ya' know -- the tiniest bit offensive, or that scanners have the ability to store and transmit these images.

And let's also put aside the fact that the number of deaths by car accident, murder, and the flu vastly outnumber victims of terrorist attacks. Let's even put aside the fact that former Homeland Security secretary Michael Chertoff is advocating the installation of these scanners while his security consulting agency's clientele includes a company that manufactures the machines.

Finally, forget for the moment the plethora of disasters that await the TSA when their bored employees inevitably circulate the scans of their hotter naked passengers, not to mention the child pornography laws these scans potentially violate.

All of these may be good reasons for to oppose the use of these scanners. But this article is about your health. Specifically, it is about this question: Will these full-body scanners give you cancer?

To start, let's look at what, exactly, we're talking about when it comes to these machines.

According to a 2003 National Council on Radiation Protection and Measurements report, there are two types of x-ray scanning systems currently used for security screening of individuals: backscatter systems and millimeter-wave systems.

In backscatter systems, the x-rays do not penetrate depths much beyond the surface of the skin, so they can detect objects hidden beneath clothing, but not objects inserted into any body cavities. These are the systems currently being used in the United States, by U.S. Customs and Border Protection as well as in many prisons. A typical scan lasts about eight seconds and results in an effective dose of approximately 0.03 microsievert (mSv/ºSv) to the individual -- radiation equivalent to that one receives inside an aircraft flying for two minutes at 30,000 feet, according to the American College of Radiology.

That's very little radiation. In fact, a 2003 report from NCRP estimated that 2,500 scans would be needed from full-body scanners in a year to exceed the suggested amount for a single radiation source.

Dr. James M. Hevezi, a member of the American College of Radiology Board of Chancellors and Chair of the ACR Medical Physics Commission, stressed to me via e-mail that backscatter systems have very low emissions:

The energy of the radiation does not penetrate beyond the skin surface, so it's not like a CT scan that has the radiation going completely through the body and producing an image of internal organs.
This energy only images the surface skin of the scanee [sic] and is very low energy. The radiation level is a 1,000 times lower than medical radiation exposures and much lower than the cosmic radiation the traveler would experience in travelling by air cross-country.

Like backscatter systems, millimeter wave systems fall under the classification of full-body imaging, which give security officers a virtual image of a passenger that highlights potentially dangerous items, but also photographs the passenger's naked body.

Millimeter-Wave Technology

In millimeter wave technology, the machines beam millimeter wave radio frequency (RF) energy over the body's surface at high speed from two antennas simultaneously as they rotate around the body. The energy reflected back from the body or other objects on the body is used to construct a three-dimensional image. The face is blurred for privacy, and the image is displayed on a remote monitor so TSA employees are separated from the passenger and can't place a face to the body's image.

Hevezi claims that these millimeter wave airport scanners do not cause any negative health effects since the waves are like cell phone radio waves that do not interact with cells in the body directly, though he stated that he is unaware of any long-term studies that look at the health effects of the full-body scanners.

"[B]ut, since this is non-ionizing radiation," he says, "there are likely no health effects that can be determined. There are recommended levels of ionizing radiation (x-rays, gamma rays, etc) that we can safely be exposed to, but no recommended levels for these non-ionizing radiation waves."

Hevezi states that negative health effects from low-power scans should be of little concern.

Backscatter Technology

In Backscatter technology, the machines use low-level x-rays to create a two-sided image. TSA is reportedly testing backscatter with an algorithm applied to the entire image to further protect passenger privacy, so scans cannot be stored or transmitted. .

Here is a typical Millimeter-Wave image:

And here is a Backscatter image:

In the wake of the Christmas Day Panty Bomber, TSA wants to install full-body scanners in airports across the country. Presently, these scanners have been deployed in 20 airports, and Newark has become the latest airport to use the technology.

Although the efficiency of these full-body scanners (which cost $170,000 apiece) has been called into question, and some experts claim the machines would not have stopped the underwear bomber, the TSA has ordered $165m-worth of scanners, using both millimeter-wave and x-ray technology, from L-3 Communications.*

According to the 2003 NCRP report, human epidemiological studies suggest equivalent radiation doses as low as 50 microsievert (mSv/ºSv,  a fancy term for "a measure of radiation dose") in one year or as low as 100 mSv over a lifetime (in addition to natural background) may produce an increase risk of deleterious consequences in man, including cancer.

But to determine the risks of cancer for lower doses of radiation (say the stuff emitting from backscatter machines), scientists would need larger studies. For example, if a high-dose radiation study had 500 participants, a low-dose study would need 50,000 participants, and a very-low dose study would need 5 million. Doses that fall below the statistically significant risk are extremely difficult to measure because the signal-to-noise ratio becomes too small. Think of a signal as music and the noise as background noise. The lower the ratio, the louder the background noise. With low-dose radiation experiments, there's too much noise to understand if the radiation is causing effects, or if it s the fault of other variables, or if there are any effects occurring at all. A large study with lots of participants would make the results of the low-dose radiation exposure easier to understand.

However, the report acknowledges there is data for protracted low-dose exposures (such as occupational exposure, or full-body scanners) that suggests an increase in some cancer risks in humans for doses as low as 100 mSv, and more limited data that suggests an increase in risk at doses as low as about 50 mSv (doses still far larger than most people encounter during airport security).

Interestingly, it seems the risk of developing cancer is greater for pilots and flight attendants than for casual flyers. Airline crews suffer higher incidence of leukemia, skin, and breast cancer. However, some studies claim the association may be confounded by differences in reproductive factors or other lifestyle factors.

Meanwhile, the organization Flyers Rights suggests airports use dogs instead of full-body scanners. It may not be a bad idea. When was the last time a German Shepherd took nude photos of tourists?

So by all means, continue to hate on the full-body scanners. Hate them because they violate civil liberties. Hate them because Michael Chertoff is helping to whore them on CNN, while his securing consulting agency represents Rapiscan Systems, a company that makes the scanners, and which just sold TSA 150 machines, paid for with $25 million in American Recovery and Reinvestment Act funds. Hate them because they're an overzealous solution (that may not even work) to a relatively small problem (when one considers millions of people die each year from non-terrorism-related events such as poverty, disease, car accidents, etc.).

But don't hate full-body scanners for giving you cancer. If anything, your flight is exposing you to way, way more radiation, which should also be cause for concern.

*(L-3 Communications representatives were asked to comment on this story, but never replied to the reporter s invitations.