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Wednesday, November 24, 2010

Airport Body Scanners: To Fear or Not to Fear?


It's that time of the year again - when Americans brace for the annual air travel melee on the industry's busiest day of the year - the Wednesday before Thanksgiving. New this year is the increased presence of total body scanners - technology developed to detect explosives stashed in the pants of a would-be terrorist - and the backlash of those who question the scanners' safety. How dangerous are the total body scanners, then?
There is disharmony between the government's official position on the scanners and some scientists' beliefs over the potential health hazards involved with a total body scan.
[...].
Both [nr: A backscatter X-ray unit (the gray and blue rectangular booth) or a millimeter wave unit (the gray cylindrical booth with clear windows] units work by firing a beam of radiation at the person being scanned. An image of the radiation that bounces back is created and viewed by a Transportation Safety Administration worker in another room. For both units, the TSA worker in the side room cannot see the person being scanned and workers operating the machine cannot see the images. If a suspicious item appears on the scan, the person then undergoes a thorough pat-down.
[...]

"We know that X-rays can damage DNA in cells, and we know that X-rays can ultimately produce cancer. So the concern is about the possibility of inducing X-ray-induced cancer in one of the individuals who's scanned," Brenner said in the interview.
The TSA says that the amount of radiation a person absorbs during a backscatter X-ray scan is equivalent to the same amount a person is exposed to over a period of two minutes when flying in an airplane at cruise altitude.
CBS medical correspondent Dr. Jennifer Ashton reported that if 1 billion people a year go through an X-ray scanner, 10 additional cancer deaths - a fraction of one percent - would result each year.
[...]
Looking at the images produced by the scanner, Peter Rez of Arizona State Univeristy estimates that the true amount is closer to one one-hundredth or even one fiftieth of a chest X-ray dose. The probability of death, he said, was closer to one in 20 million. While that's still a fraction of a percent, it is a higher risk than the risk of dying from a terrorist attack, which he put at one in 30 million.
[...]
Another group of scientists at the University of California, San Francisco, sent a letter to the President's science and technology adviser arguing that the X-ray scanner poses a greater risk than medical X-rays and the radiation absorbed during a flight. In those two cases, the radiation is distributed evenly throughout the body, the doctors say. The radiation from the scanners, however, is embedded in the skin, resulting in a higher concentration of radiation in a given area.
Questions remain including how the X-ray scanners will affect frequent flyers (including businessmen and flight attendants who could go through security anywhere from 200 to 400 times a year), children, pregnant women and travelers with weakened immune systems. There is also a question of what could happen should a machine get stuck or fail, potentially blasting one point on a person's body with excess X-ray radiation.
The good news about scanners: Millimeter wave scanners, which are also in use at airports around the country, use very far infrared waves, waves at the opposite end of the electromagnetic spectrum from the dangerous ionizing radiation of X-ray waves. X-rays are shorter waves that can penetrate the skin and alter DNA. Millimeter waves, by contrast, are longer waves that penetrate clothes but stop at the skin. The millimeter scan is akin to a heat lamp and is considered to be far safer than X-ray scanners.
[...]
One Congressman, Ron Paul of Texas, is sponsoring legislation to fight the new scanning requirements, arguing that the examinations are a violation of the fourth amendment protecting U.S. citizens from unreasonable search and seizure.
via physicsbuzz.physicscentral.com (follow the link to read full article)
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