March 17, 2011
Safety Concerns Over Airport Security Scanners
(Ivanhoe Newswire) -- The government's efforts to keep the airways safe by subjecting travelers to more scrutiny are facing their biggest backlash since the attacks of Sept. 11, 2001 "“ even as recent terror attempts indicate that air travel remains a prime target for groups linked to al-Qaeda. The Transportation Security Administration (TSA) has now begun to implement whole-body imaging scanners as a primary screening measure on travelers passing through airport security checkpoints.
One type of scanner employs millimeter wave technology, which delivers no ionizing radiation. However, the second type of scanner at this time deployed at airports uses backscatter X-rays that expose the individual being screened to exceptionally low levels of ionizing radiation.
In the foremost article, David J. Brenner, Ph.D., D.Sc., director of the Center for Radiological Research at Columbia University Medical Center in New York, N.Y., proposes that from a public health policy perspective, given that up to one billion such scans per year are now possible in the U.S, we should be apprehensive about the long-term consequences of an extremely large number of people being exposed to a potential radiation-induced cancer risk, no matter how slight.
"The risks for any individual going through the X-ray backscatter scanners are exceedingly small," which Dr. Brenner was quoted as saying. "However, if all air travelers are going to be screened this way, then we need to be concerned that some of these billion people may eventually develop cancer as a result of the radiation exposure from the X-ray scanners."
In the subsequent article, David A. Schauer, Sc.D., C.H.P., executive director of the National Council on Radiation Protection and Measurements (NCRP), argues that the summation of negligible average risks over large populations or time periods into a single value produces a distorted image of risk that is out of perspective with risks accepted every day, both voluntarily and involuntarily.
"There is no scientific basis to support the notion that a small risk to an individual changes in any way for that individual as others around him are also exposed to the same source of radiation," Schauer was quoted as saying.
"Critics of security screening acknowledge that doses from backscatter X-ray systems are very low and safe for an individual."
Dr. Schauer advocates strict regulatory control of the backscatter scanners in order to ensure that their use is consistent with the goals and objectives of radiation protection, which include justification (benefits exceed cost or harm), optimization (exposures are kept as low as reasonably achievable) and limitation (individual doses are limited).
"Any decision that alters the radiation exposure situation should do more good than harm," Dr. Schauer said. "In other words, people should only be exposed to ionizing radiation for security screening purposes when a threat exists that can be detected and for which appropriate actions can be taken. In addition, exposures must be justified and optimized."
Both Dr. Brenner and Dr. Schauer concur that the scanners with millimeter wave technology should be considered as a utmost option, since they are comparable in cost as well as functionality to the backscatter machines, but do not expose the passenger to ionizing radiation. Conversely, they also say that the average traveler should not be exceedingly concerned about being screened with the backscatter scanners.
"As someone who travels just occasionally, I would have no hesitation in going through the X-ray backscatter scanner," Dr. Brenner concludes. "Super frequent fliers or airline personnel, who might go through the machine several hundred times each year, might wish to opt for pat-downs. The more scans you have, the more your risks may go up "“ but the individual risks are always going to be very, very small."
NCRP has recommended that backscatter X-ray systems adhere to an effective dose of 0.1 microsieverts (ÃµSv) or less of ionizing radiation per scan, which roughly equates to the radiation exposure each passenger receives in under two minutes on the plane while flying at 30,000 feet. The average person in the U.S. receives an effective dose of about 3 millisieverts (3,000 ÃµSv) per year from naturally occurring radioactive materials and cosmic radiation from outer space.
SOURCE: Radiology, March 16, 2011