More pilots and now a group of university scientists are protesting a TSA security directive that will soon make full body scanners the primary method of passenger screening at airports across the United States.
If my constant haranguing about civil liberties and the spurious science behind full body scanners hasn't swayed you, maybe this warning from four doctors from the University of California - San Francisco (UCSF) that the backscatter technology employed by many full body scanners may be very hazardous to your health will be a bit more convincing.
Unlike other scanners, these new devices operate at relatively low beam energies (28keV). The majority of their energy is delivered to the skin and the underlying tissue. Thus, while the dose would be safe if it were distributed throughout the volume of the entire body, the dose to the skin may be dangerously high.
The X-ray dose from these devices has often been compared in the media to the cosmic ray exposure inherent to airplane travel or that of a chest X-ray. However, this comparison is very misleading: both the air travel cosmic ray exposure and chest Xrays have much higher X-ray energies and the health consequences are appropriately understood in terms of the whole body volume dose. In contrast, these new airport scanners are largely depositing their energy into the skin and immediately adjacent tissue, and since this is such a small fraction of body weight/vol, possibly by one to two orders of magnitude, the real dose to the skin is now high.
In addition, it appears that real independent safety data do not exist. A search, ultimately finding top FDA radiation physics staff, suggests that the relevant radiation quantity, the Flux [photons per unit area and time (because this is a scanning device)] has not been characterized. Instead an indirect test (Air Kerma) was made that emphasized the whole body exposure value, and thus it appears that the danger is low when compared to cosmic rays during airplane travel and a chest X-ray dose.
Check out their full report here.
The question comes down to this: is it better to rush the implementation of these costly machines because they might provide marginal security benefits or should we fully test the health effects and viability of this technology before totally altering our airport security paradigm in America? I think the answer is obviously the latter choice.
And it's not just medical doctors and a small segment of disgruntled pilots that are now protesting full body scanners: US Airways pilots were advised by their union today to avoid backscatter and millimeter wave screenings (after AA's pilot union did the same last week) and Australian pilots are also considering a boycott as full body scanners are rolled out in Australia beginning in early 2011.
These groups echo the concerns expressed by the UCSF doctors over the short and long-term health ramifications of this new scanning technology.
So whether we look at it from a Constitutional angle (full body scanners violate the Fourth Amendment's assurance against unreasonable searches and seizures), a technological angle (full body scanners are untested in an operational setting and may not be able to pick up the very explosive materials that they are purported to protect us against), or a health angle (full body scanners, particularly the backscatter variant, may be critically detrimental even in small doses to your health), we are left with the patently obvious conclusion that it would be prudent to take a step back and examine more closely the TSA's reactionary decision to deploy this new technology before proceeding further.