Answer to Question #11343 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I am 15 weeks pregnant and planning air travel. I am concerned that I may undergo security screening at the time of boarding, and I do not want to be screened with ionizing-type metal detectors. How can I distinguish between ionizing and nonionizing metal detectors at the airport?
I am also concerned about handheld metal detectors. On what principle are they based—ionizing or nonionizing radiation?
What prior safety precautions can I take before security screening?
Thank you for your questions. There are four types of human screening tools currently in use at airports: metal detectors, millimeter scanners, backscatter scanners, and wands.
Metal detectors are the screening units that have been in use for years. They are rectangular units that we walk through. They use magnetic fields, which are nonionizing radiation (unlike x rays), to look only for metal.
Millimeter scanners use a radiofrequency field (also nonionizing). Often they look like a large circular unit you step into and the arms move around you. You are told to take everything out of your pockets for this scan as, in this case, the image coming back to the Transportation Security Administration employees will show anything on the body (not just metal).
Backscatter scanners use low-energy x rays. Often these scanners look like a couple of large boxes that you stand between for the x rays. They do two scans and the radiation dose is about 0.05 microsievert (µSv, a unit of effective radiation dose). For comparison, a flight from New York to Los Angeles would expose a passenger to a radiation dose from cosmic rays of about 40 µSv. So the backscatter scanner delivers a very low dose and is considered safe for pregnant women. In fact, the x rays have such a low energy, it is debatable whether they can even get to the depth of the fetus.
Wands are also like metal detectors. They use magnetic fields to look for objects made of iron, steel, etc., and they are also nonionizing.
It is safe for you to undergo any of these screening options.
Certified Medical Health Physicist