Although the radiation levels scans emit are considered extremely low, if you still feel uncomfortable, know that you have the right to other search methods.

New scanners at the airport will leave you with nothing to hide.

RODALE NEWS, EMMAUS, PA—In response to a failed Christmas-day attempt to blow up a plane over Detroit, the U.S. Transportation Security Administration (TSA) is moving forward with plans to place 150 more full-body scanning machines in U.S. airports in the coming months. The machines will allow security workers to virtually undress passengers, checking to make sure they aren't hiding any metallic or nonmetallic weapons, drugs, or explosives. The announcement is getting mixed responses, including criticism from privacy-rights activists, support from security experts, and questions from passengers concerned about their health. The words "body scan" are causing some worry among health-conscious air travelers, partly because last month the journal Archives of Internal Medicine published studies estimating that the radiation levels from medical CT scans cause more than 20,000 new cancers a year. (Currently, about 70 million scans a year are performed in the U.S., compared to just 3 million in 1980.) However, before you worry yourself sick over exposure, it's important to understand the radiation dose of these machines, and also your rights as a U.S. citizen in line at a security checkpoint.

THE DETAILS: There are two types of body scanners being put into place. Millimeter-wave imaging-technology units do not produce ionizing radiation, the kind we're exposed to when we get X-rays, or, in much higher doses, when we have CT scans. Currently, there are 40 millimeter-wave scanning machines already in use in 19 U.S. airports. They are used as either the primary screening machines that passengers walk through, or more commonly, for secondary or random screenings. The other type of body scanning that has been tested by TSA uses backscatter technology, which does produce small amounts of ionizing radiation by using extremely weak X-rays. After testing them in a pilot program, the administration has 150 of these machines on order, and they will be deployed to U.S. airports in the coming months.

WHAT IT MEANS: The first step is to put the radiation exposure in perspective. According to TSA, the amount of radiation you're exposed to during a two-second millimeter-wave scan exposes you to radio-wave radiation that is 10,000 times less powerful than radiation levels that pulse from a cellphone. A backscatter scan exposes you to the same amount of radiation you would experience during two minutes of a cross-country or ocean plane flight, thanks to cosmic radiation in the atmosphere. According to the National Council on Radiation Protection and Measurement (NCRP), a traveler subjected to at least 2,500 backscatter scans a year would barely reach the Negligible Individual Dose. In same report, NCRP found that a traveler subjected to at least 2,500 backscatter scans per year would barely reach the Negligible Individual Dose.