If you flew on a plane this year, you were probably asked by an agent at airport security to assume the position — hands up, feet apart. Across the country, the U.S. government has installed full-body scanners, which are designed to generate detailed, three-dimensional contours of the body, so that security agents can more easily spot any weapons, from ceramic knives to explosives, that may be hiding under clothing and would be missed by metal detectors. Sounds like a good idea, but the problem lies in how the machines do their duty.
There are two types of scanners: millimeter-wave scanners, which use electromagnetic waves to generate images and are not thought to pose any health concerns; and backscatter X-ray scanners, which use carcinogenic radiation similar to that emitted by medical X-rays. In November, the European Commission banned backscatter machines from all airports in member countries for reasons of health and safety, but they’re still in use in the U.S.
Studies on the health effects of X-ray scanner exposure are confusing at best. The absolute amount of radiation emitted by a single scan is less than that of a medical X-ray, and even less than the amount a passenger would be exposed to from cosmic rays on a cross-country flight, according to the Transportation Security Administration (TSA), but the long-term risk of cumulative exposure from repeated trips through the scanner isn’t known. The government assures travelers that the machines are safe, but if you’re concerned, you can ask the TSA agent whether the scanner uses X-rays, and if it does, opt for a physical pat-down instead.
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