VOA标准英语2010年-Body Scanners, Touted as Effective Too

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Public opinion polls suggest most Americans favor full body scanners as a way to protect against terror attacks on commercial airliners¹. The benefits of scanners are being debated in a number of countries. Some groups have raised privacy issues.  But many people believe the machines could also contain health risks. As Vidushi Sinha reports, the scanners release small amounts of radiation, which over time, some scientists say, could increase the risk of cancer.

If the alleged² bomber³ on a Christmas Day flight to the United States had gone through a full body scanner, his explosives might have been detected and an attempted bombing foiled much earlier.

The United States in addition to Britain, the Netherlands, France and Italy have announced plans to install body scanners at airports.

Using x-rays bounced off the body, the machines generate anatomically correct images and can detect items hidden in clothing.

Aside from concerns over privacy, there's a growing discussion about a possible risk of cancer from radiation emitted by the scanners. 

But according to experts, the risk is small.  The radiation from so called backscatter  technology is 2,000 times less than a chest x-ray and 200,000 times less than a CAT scan. 

"Total exposure time is about 8 to 15 seconds, and the radiation dose levels are quite small because the x-rays used here do not penetrate⁴ the body," Mahadevappa Mahesh explained. "It is very low dose therefore it's just reflecting back, and the scattered⁵ radiation coming from the body is actually captured by a detector⁶ and you get the image."

The alleged Christmas day bomber, Umar Farouk Abdulmutallab, flew through Amsterdam and Lagos, Nigeria's commercial capital.

Media reports say Nigeria had already received body scanners from the United States, but did not use one on the alleged bomber. 

Some experts say these expensive machines will be difficult for many African and poor countries to purchase and install.

Even if developed countries donate the scanners, there still could be health issues. 

The risk of radiation exposure could be greater in developing countries where maintenance might be spottier, some say. 

"As we do in any of these scanners in hospitals, where we do periodic checks to make sure that radiation levels are as specified⁷ and within the acceptable limits, that is important there is always a possiblity that something can go wrong in the scanners and that can emit more radiation and to avoid this it has to be checked periodically," Mahesh said.

Though many experts believe that radiation exposure from full-body scans will not pose a risk of cancer, some urge caution.

"Children in general are more sensitive than adults to radiation.  And the developing embryo⁸ and fetus⁹ in pregnancy¹⁰ are the most sensitive of all," said Dr. David Brenner of Columbia University Medical Center in New York.

Experts say more study is needed.