Friday, November 6, 2009

Response to: “Oops: Backscatter X-ray machines tear apart DNA"

This article has been receiving quite a bit of attention and it’s leading people to believe the Backscatter Advanced Imaging Technology (AIT) used by TSA emits terahertz radiation. Recent studies are showing that terahertz radiation may “unzip double-stranded DNA, creating bubbles in the double strand that could significantly interfere with processes such as gene expression and DNA replication.”

(I know… who knew that your DNA could be unzipped? Hey buddy, your barn door’s open!!!)

I forwarded the article around to a few subject matter experts here at TSA and was provided with some interesting information:

“TSA has not tested nor procured any terahertz AIT systems.”

That sentence should sum it up for most of our readers, but for those who like to get into the weeds, here is some more interesting information that was given to me from the fine folks at the Office of Security Technology (OST):

The Transportation Security Administration (TSA) has assessed multiple types of AIT systems including X-ray backscatter and millimeter wave. Both offer safe and effective whole body screening for weapons and explosives concealed on a person’s body. Backscatter X-ray technology uses X-rays that penetrate clothing, but not skin, to create an image. Millimeter wave technology uses sensors to collect millimeter wave energy to measure the difference in radiated energy relative to each object against a common background (the human body produces these signatures in typical screening applications) to construct a composite image.

Backscatter - Relies on a narrow, low intensity X-ray beam scanned over the body’s surface at high speed that is reflected back from the body and other objects placed or carried on the body, where it is converted into a computer image of the subject and displayed on a remote monitor. For comparison purposes, the X-ray dose received from the backscatter system is equivalent to the radiation received in two minutes of airplane flight at altitude (0.003* millirem by backscatter (2 scans) compared to .0552 millirem for two minutes of flight). Newer technologies require less scanning time, reducing individual X-ray exposure to .002 millirem for the entire process. The backscatter AIT meets and exceeds the American National Standards Institute (ANSI) standard for personnel security screening systems using X-rays.

Millimeter Wave - Uses non-ionizing radio frequency energy in the millimeter wave spectrum to generate an image based on the energy reflected from the body. The frequency range for millimeter wave technology exists in the range between 30-300 gigahertz. The three-dimensional image of the body is displayed on a remote monitor for analysis. The energy projected by the system is 10,000 times less than a cell phone transmission (.00000597 mW/cm2 for millimeter wave technology compared to 37.5 mW/cm2 for a cellphone).

Other Safety Information

“TSA security screening technologies are required to meet consensus standards, such as those issued by the American National Standards Institute (ANSI), as well as regulatory requirements such as those issued by the Food and Drug Administration (FDA). Our systems are independently tested as well by such laboratories as Johns Hopkins Applied Physics Laboratory (APL) and the National Institute for Standards and Technology (NIST) and FDA. We also apply an aggressive maintenance program to ensure that these systems continue to meet these performance standards. Additionally, TSA Occupational Safety Health and Environment (OSHE) is an active participant in our project integrated project teams. TSA OSHE assists in the development and validation of technology safety requirements. We also conduct safety evaluations as part of our laboratory, TSA Systems Integration Facility (TSIF), operational and site acceptance testing procedures.”

TSA tells its employees, namely Transportation Security Officers (TSOs), about the safety of advanced imaging technology machines, including the radiation exposure, during training on the equipment. In addition, TSA’s Office of Occupational Safety Health and Environment has individuals who work directly with TSOs to communicate safety information about operating the equipment. Information is available to TSOs through the OSHE Web site and employees can contact members of OSHE directly with questions.

*.04 was posted in error. The corrrect number was added. 0.003 millirem. Edited on 1/5/10


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