Answer to Question #9421 Submitted to "Ask the Experts"

Category: Security Screening — Airport Screening

The following question was answered by an expert in the appropriate field:

Q

With all of the recent media and public frenzy about airport x-ray scanners, it would be very helpful to get the facts. How do current "backscatter" x-ray security scanners work? What is the dose from an airport x-ray scanner and how does it compare to background radiation? Does airport scanner radiation penetrate through my entire body like medical x rays? Is there any "real" cancer risk from going through an airport x-ray scanner?

A

Thank you for your questions. Let me take them one at a time.

How do current "backscatter" x-ray security scanners work?
After you step in to the enclosure, an image is formed using low energy x rays (a maximum of 50 keV). These x rays pass through your clothing and are scattered back from your body into radiation detectors on the scanning device.

What is the dose from an airport x-ray scanner and how does it compare to background radiation?
One manufacturer states that the whole-body effective radiation dose to a person being imaged is about 0.05 microsievert. That is a dose per screening in which both the front and back of a person are scanned during a security check. Background radiation dose averages 3,100 microsievert (or 3.1 millisievert) per year and a chest x ray effective radiation dose is about 100 microsievert. So, a backscatter screening results in an effective dose that is about 1,000 times smaller than a chest x ray.

Does airport scanner radiation penetrate through my entire body like medical x rays?
Yes. The x rays produced by the scanner are absorbed throughout the body. The doses are extremely low, with radiation doses higher near the surface of the body (e.g., ribs, skin, etc.). The doses to deeper internal organs (stomach, lungs, liver, etc.) are approximately one-fourth (25 percent) of the average dose to the skin.

Is there any "real" cancer risk from going through an airport x-ray scanner?
It depends on what you mean by "real." Since our lifetime risk of cancer, regardless of radiation exposure, is on the order of 1 in 2 (or about 42 percent of us will get a cancer in our lifetime), then, no, there is negligible risk of cancer. Even so, the risk of cancer from the radiation dose received by an airport x-ray scanner can be calculated. The increased cancer risk has been calculated to be between 1 in 20 million and 1 in 200 million.

Jack L. Glover
X-Ray Physicist

Kelly Classic
Certified Medical Health Physicist

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
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