One type relies on radio waves, another uses low level X-rays,,
FRIDAY, Jan. 8 (HealthDay News) -- Since the thwarted Christmas day terrorist attack on an airline flight approaching Detroit, officials have announced plans to increase the use of fully body scans at U.S. airports, leaving some travelers wondering about the health effects of these devices.
Will this effort to detect smuggled explosives and weapons expose passengers to excess levels of radiation? Experts say no.
Two types of scans -- millimeter wave scanners and backscatter scanners -- are being used in the United States.
Millimeter wave scanners, which use radio waves, have no proven adverse health effects and don't expose passengers to any X-rays, but they haven't been widely studied. Backscatter scanners use extremely low levels of X-rays.
"A passenger would need to be scanned using a backscatter scanner, from both the front and the back, about 200,000 times to receive the amount of radiation equal to one typical CT scan," said Dr. Andrew J. Einstein, director of cardiac CT research at Columbia University Medical Center in New York City.
"Another way to look at this is that if you were scanned with a backscatter scanner every day of your life, you would still only receive a tenth of the dose of a typical CT scan," he said.
By comparison, the amount of radiation from a backscatter scanner is equivalent to about 10 minutes of natural background radiation in the United States, Einstein said. "I believe that the general public has nothing to worry about in terms of the radiation from airline scanning," he added.
For moms-to-be, no evidence supports an increased risk of miscarriage or fetal abnormalities from these scanners, Einstein added.
"A pregnant woman will receive much more radiation from cosmic rays she is exposed to while flying than from passing through a scanner in the airport," he said.
The extent of penetration from backscatter systems is pretty shallow, explained another expert, David A. Schauer, executive director of the National Council on Radiation Protection and Measurements. "With backscatter systems, the X-rays do not penetrate to depths much beyond the surface of the individual, so they are useful for imaging objects hidden under clothing, but are not useful for detecting objects hidden in body cavities."
Richard Morin, a medical physicist at the Mayo Clinic, said the real issue for passengers might be privacy, not safety.
"From a radiation standpoint there has been no evidence that there is really any untoward effect from the use of this device [backscatter scanner], so I would not be concerned about it from a radiation dose standpoint -- the issues of personal privacy are a different thing," he said.
The health effects of the more common millimeter-wave scanners are largely unknown, and at least one expert believes a safety study is warranted.
"I am very interested in performing a National Council on Radiation Protection and Measurements study on the use of millimeter-wave security screening systems," said Thomas S. Tenforde, council president.
"I think it would be helpful to convene an expert panel to prepare a concise summary of the health and safety issues associated with the use of this type of security screening system," he said.
Forty millimeter-wave scanners are operating at 19 airports, according to the U.S. Transportation Safety Administration (TSA), which says the machines produce 10,000 times less energy than a cell phone. "We, and all objects around us, generate millimeter wave energy, and we are exposed to it every single day," the agency reported.
The TSA also plans to buy 150 backscatter scanners.
Passengers, meanwhile, have the right to refuse a full body scan. But if they do so, they will be patted-down by a TSA agent, the agency says.
For more information on airport scanners, visit the U.S. Transportation Safety Administration.
SOURCES: David A. Schauer, Sc.D., executive director, and Thomas S. Tenforde, Ph.D., president, National Council on Radiation Protection and Measurements, Bethesda, Md.; Richard Morin, Ph.D., medical physicist, Mayo Clinic, Jacksonville, Fla; Andrew J. Einstein, M.D., Ph.D.,director, cardiac CT research, Columbia University Medical Center, New York City
All rights reserved