Friday, November 26, 2010

They don't care. There's money to be made...

Scientists: TSA X-ray machines almost certainly will Cause Testicle Cancers in Men and Brest Cancer in Women

The TSA has slowly been implementing the use of X-ray scanners in airports (so far, 38 airports have 206 of the machines) in order to see through passengers' clothes and check them for explosive devices. Officials have asserted that the machines are okay to use on the basis of the everyday use of X-rays in medical offices. However, a group of four UCSF professors pinpointed several important differences between the medical X-ray machines and those used in airports. They described the issues in a letter to Dr. John P. Holdren, the assistant to the president for science and technology.
A normal X-ray image is a familiar sight—depending on the exposure, an X-rayed person typically appears only as a skeleton. This is because the X-rays used in those machines penetrate the skin and can only scatter off of the larger molecules in bones.
Unlike a medical X-ray, the TSA X-ray machines are a sci-fi fan's dream: they are lower-energy beams that can only penetrate clothing and the topmost layers of skin. This provides TSA agents with a view that would expose any explosives concealed by clothing. But according to the UCSF professors, the low-energy rays do a "Compton scatter" off tissue layers just under the skin, rather than the bone, exposing some vital areas and leaving the tissues at risk of mutation.
“Compton scattering is a type of scattering that X-rays and gamma rays undergo in matter. The inelastic scattering of photons in matter results in a decrease in energy (increase in wavelength) of an X-ray or gamma ray photon, called the Compton effect. Part of the energy of the X/gamma ray is transferred to a scattering electron, which recoils and is ejected from its atom (which becomes ionized), and the rest of the energy is taken by the scattered, "degraded" photon.”

When an X-ray Compton scatters, it doesn't shift an electron to a higher energy level; instead, it hits the electron hard enough to dislodge it from its atom. The authors note that this process is "likely breaking bonds," which could cause mutations in cells and raise the risk of cancer.
Because the X-rays only make it just under the skin's surface, the total volume of tissue responsible for absorbing the radiation is fairly small. The professors point out that many body parts that are particularly susceptible to cancer are just under the surface, such as breast tissue and testicles. They are also concerned with those over 65, as well as children, being exposed to the X-rays.
The professors pointed to a number of other issues, including the possibility that TSA agents may scan certain areas more slowly (for example, the groin, to prevent another "underwear bomber" incident like the one in December 2009), exposing that area to even more radiation. But the letter never explicitly accuses the machines of being dangerous; rather, the professors encourage Dr. Holdren to pursue testing to make sure that the casual use of these X-rays is safe.


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