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When you get X-rays at the dentist's office, the hygienist drapes you in a heavy lead jacket to protect your body from excess radiation. You might wonder, then, as you pass through the new X-ray body scanners at airports, whether you're being put at risk. Then answer? Probably not. It all has to do with dosage.

The TSA's scanners use an imaging system known as backscatter technology, which works by hitting a passenger with low-dose X-ray radiation as they stand between two box detectors. The image is produced on a nearby computer and can reveal weapons and explosives hiding under clothing or stowed away inside a person's body.

The key here is "low-dose." The average radiation exposure, as quoted by the TSA, for each scan is about .15 uSv (a unit of radiation), which is many times less than what you're exposed to at the dentist's office. In fact, according to the American College of Radiology and the American Roentgen Ray Society, an airline passenger flying cross-country is exposed to more naturally-occurring cosmic radiation from the flight than from screening by one of these devices.

Additionally, the National Council on Radiation Protection and Measurement has reported that a traveler would need to experience 2,500 backscatter scans per year to reach what they classify as a Negligible Individual Dose.

It's worth noting that no amount of X-ray exposure is considered beneficial, but to many people, including the TSA, these levels are safe enough. But many pilots, who would go through security hundreds of times a year, aren't convinced. Neither is the Electronic Privacy Information Center (EPIC) in Washington, D.C. “The TSA likes to say it’s only equivalent to two minutes in the air, but scientists believe it’s much more," EPIC staff counsel Ginger McCall told TechNewsDaily earlier this year.

David Brenner, chair of the department of medicine at Columbia University, discussed the topic at the Congressional Biomedical Research Caucus after the TSA began rolling out backscatter technology in airports, and noted that the dosage released through it is indeed small, but “not as small as TSA would have us think.”

“The number given is what the whole body receives on average. However, the whole body isn’t actually receiving the radiation exposure. The skin on the scalp receives 20 times the average dose that is typically quoted by TSA and throughout the industry. It’s still a low-dose, but it’s much more than what’s usually said.”

Radiation acts as a multiplier of natural cancer rates, Brenner said. There are 800,000 cases of basal cell carcinoma diagnosed in the United States each year, which is one of the most common cancers associated with X-ray exposure. Earlier this year, a group of scientists from the University of California sent a letter to the White House Office of Science and Technology noting that, "while the dose would be safe if it were distributed throughout the volume of the whole body, the dose to the skin may be dangerously high."

“The concern is that radiation promotes pre-existing damage,” he said. “Since the cancer rate is so high for basal cell carcinoma, this number could be multiplied further by radiation risks.” Most of the radiation from X-ray backscatter machines hits the top of the head – where 85 percent of this type of cancer forms.

“There is no good reason why [TSA] scans the head and neck, especially since you can’t hide explosives there,” Brenner said.

“The individual risks associated with X-ray backscatter scanners are probably extremely small, but if all 800 million airport annual users are screened via X-ray, then the risk rate is multiplied by a large number – and that implies a potential public health and societal risk,” Brenner added.

The scanners probably won't go away any time soon. In recent months, the TSA has repeatedly argued that more thorough screening methods are necessary at the nation's airports. "We are frequently reminded that our enemy is creative and willing to go to great lengths to evade detection," TSA spokesperson Sari Koshetz told TechNewsDaily. "TSA utilizes the latest intelligence to inform the deployment of new technology and procedures, like the pat down, in order to stay ahead of evolving threats."

So there you go. If you don't fly every few days, the dosage is probably too low to cause damage. If you're exposed to it frequently, even at low doses, scientists can't eliminate the potential for possible injury. We'll leave the decision to you, but be warned: The alternative is a very friendly pat down from security guards.

This article contains information from reports by TechNewsDaily and LiveScience, sister sites of Life's Little Mysteries.