TSA or Transportation Security Administration, the federal agency responsible for airport security, started using full-body x-ray scanners from 2009 after a Nigerian tried to blow up a Detroit-bound plane with a bomb that was hidden in the underwear.

This move of TSA has been met with both happiness and concern.

One of the primary concerns about a full-body x-ray scanner is that the radiation from the scanner can cause changes in a person’s DNA which can lead to cancer.

So, this leads us to the question. Is the full-body scanner completely risk-free? The answer is both yes and no.

If you are worried about radiation being emitted from the scanner, then the yes, scanner does emit radiation. But is it safe? Absolutely 100%.

Radiation here refers to ionizing radiation that has energy as well as properties that can damage DNA, which leads to cancer. In high doses, ionizing radiation can even cause burns or kill.

The following article talks about types of scanners and the safety issues associated with it.

Types of full-body scanners

TSA employs two kinds of x-ray scanners:

Millimeter-Wave Scanners:Uses radio waves and does not produce ionizing radiation.
Backscatter X-ray Scanners: Uses low-dose x-ray which produces ionizing radiation.

Not Much Radiation

A study was conducted by researchers (Dr. Rebecca Smith-Bindman and Pratik Mehta from the University of California (San Francisco and Berkley respectively)). The study authors estimated that a human being would be exposed to 0.03 microsieverts to 0.1 microsieverts in a backscatter x-ray scanner.

A standard measurement, microsievert, takes into account the biological effects produced due to radiation. (In the US, “rem” is used. One microsievert = 100 micro-rems.)

According to the authors, human beings are exposed to 2.4 millisieverts of natural background radiation, which is nearly thousands of times more than 0.1 microsieverts produced from a backscatter scanner.

The study authors also made some other remarkable comparisons. A passenger would have to undergo 50 full body scans from a backscatter to be exposed to the same amount of radiation from a dental x-ray, 1,000 scans to equal a chest x-ray and 200,000 scans for exposure equal to one abdomen and pelvis CT scan.

The authors argue that an airline passenger will be exposed to more radiation due to increased radioactivity from space at higher altitudes than a scanner.

By their reckoning, an airline passenger receives less than 1% of the radiation from airport scans while compared to a six-hour flight.

Cancer Risk – Trivial

The researchers used a linear-no threshold model to estimate cancer risk from the ionizing radiation emitted by the backscatter x-ray scanner.

Linear means increasing radiation increases the risk of cancer. No-threshold means any exposure, regardless of the size, can cause cancer.

The linear no-threshold model extrapolates from higher doses. While there is no clarity if the model is a true representative of the low-level radiation risk, it is a widely accepted model and is also the basis for radiological protection standards.

The California researchers applied the model on three sets of fliers – all fliers, frequent fliers, and frequent-flying five-year girls. Five-year-old girls were included because they were sensitive to radiation, the exposure will be limited to body part near-surface like breasts and there were existing models of determining breast cancer risk.

The results showed that the risk was very, very minimal even in the high numbers that were used. According to the authors, the additional causes of risk due to airport scanners were "truly trivial.”

Dissenting Opinion

Not many, however, agree with these findings. Some experts believe that the risk for cancer is higher because the per-scan dose is much higher than imagined.

Dr. David Brenner from Columbia University opines that the use of more than a billion backscatter x-ray scanners could result in the development of more than 100 additional cancers, a number that is not trivial, according to him.

He also opined that while security needs were paramount, the use of millimeter-wave scanners that did not use ionizing radiation was more feasible.

The TSA's stand on this was that having multiple suppliers can leverage competition for procuring systems that offer the best value to the federal government.

More Important Worries

Radiation exposure is a fact, but then it is much less than eating a banana or having a glass of clean drinking water, which has got radium elements in it.

While millimeter-wave scanners do not emit any radiation, backscatter scanners emit very minimal radiation, much less than exposure caused due to flight. It is best left to people to determine whether they want to think about these things or worry about more important things in life.