By now, many of you have experienced the at least one of the two advanced screening devices in major airports across the country. There have been some safety concerns voiced about the "backscatter" machines that use low dose X-rays to penetrate articles of clothing to detect dangerous items. Looks like the Department of Homeland Security is going to fund the National Academy of Science to examine the safety question.
Before I really get into this, I first have to describe the three major screening technologies in use so you understand which one will be studied by the National Academy of Science. Most are already very aware of the basic walk through metal detector (WTMD). This is the basic technology employed at all airports to detect metal objects. Next is the millimeter wave machine. These are being deployed in greater numbers in major airports not only domestically but also internationally. You can see a picture of one at the link. To be overly simplistic this is more like being microwaved than X-rayed. The health risks are minimal for this type of technology and it has never really been associated with cancer. The last technology is an actual X-ray generating device called the backscatter scanner. You can recognize these machines because you are basically walking between two boxes. These are mostly only used in the United States and Europe has banned the use of this technology due to safety concerns.
I will go through either a WTMD or a millimeter wave scanner with no concerns, but I balk at the backscatter machine. I have opted for the pat down on several occasions. The TSA has to date performed the optional pat down with minimal fuss nor is my right to exercise this option ever questioned.
As was recently reported, the TSA has started removing some of the backscatter machines from airports already. The machines aren't being taken out of service, rather, they are being moved to smaller airports with fewer travelers. The time required to screen each individual passenger with the backscatter machine is relatively longer than just walking through a medical detector or even the millimeter wave scanner. This can cause major problems at busy airports as the time to screen each passenger is increased. Even small increases in screening time can lead to long lines and traveler frustration. This is probably the main reason these machines are being moved.
There have been a number of calls for a safety review for the backscatter machines from concerned citizens and academics. The Department of Homeland Security and the TSA have basically issued statements saying that everything is fine, it is a small dose of radiation, and there is no risk of cancer due to even repeated exposure to these machines. The problem with that statement is that in clinical and scientific circles there are major ethical principles about minimizing the amount of radiation people are exposed to and to ensure that there is a medically relevant purpose for any X-ray exposure. Similarly, in a research laboratory setting, scientists are trained with the "ALARA" principle: as low as reasonably allowable. Basically, limit exposure as much as possible as there is no lower limit of safety for radiation. All radiation exposure is bad, and more importantly, cumulative over a certain period of time.
It looks as though the Department of Homeland Security is now asking the National Academy of Science to review the safety of the backscatter machines:
The Department of Homeland Security, Office of Procurement Operations (OPO), Washington, DC intends to award a sole source contract to the National Academy of Sciences pursuant to FAR 6.302-1 to convene a committee to review previous studies as well as current processes used by DHS and equipment manufacturers to estimate radiation exposure resulting from backscatter x-ray advanced imaging technology (AIT) systems used in screening air travelers and provide a report with findings and recommendations on: (1) whether exposures comply with applicable health and safety standards for public and occupational exposures to ionizing radiation, and (2) whether system design (e.g., safety interlocks), operating procedures, and maintenance procedures are appropriate to prevent over exposures of travelers and operators to ionizing radiation. This study will not address legal, cultural, or privacy implications of this technology.Notice the last sentence. This study is solely about the safety issues and not other concerns such as privacy. National Academy of Science studies are usually very open and public, so it should be fairly easy to track this as the study progresses.