I really haven't talked much (at all) about the "safety" concerns over the TSA's X-ray scanner devices, because a lot of it did seem like overreactions from people who didn't really know what they were talking about. However, there does appear to be increasingly credible claims from scientists that, at the very least, what the government is saying about these machines is not at all accurate. Keith Dawson
points us to a blog post by Molecular Biologist Jason Bell, reviewing the literature on these devices
and comparing it to questions sent by a group of scientists at UCSF, and suggesting (at best) that the government is being misleading in its claims about the safety of the devices. Here's just a snippet:
With respect to errors in the safety reports and/or misleading information about them, the statement that one scan is equivalent to 2-3 minutes of your flight is VERY misleading. Most cosmic radiation is composed of high energy particles that passes right through our body and the plane itself without being absorbed. The spectrum that is dangerous is known as ionizing radiation and most of that is absorbed by the hull of the airplane. So relating non-absorbing cosmic radiation to tissue absorbing man-made radiation is simply misleading and wrong. Of course these are related and there is over-lap, but we have to compare apples to apples.
Furthermore, when making this comparison, the TSA and FDA are calculating that the dose is absorbed throughout the body. According the simulations performed by NIST, the relative absorption of the radiation is ~20-35-fold higher in the skin, breast, testes and thymus than the brain, or 7-12-fold higher than bone marrow. So a total body dose is misleading, because there is differential absorption in some tissues. Of particular concern is radiation exposure to the testes, which could result in infertility or birth defects, and breasts for women who might carry a BRCA1 or BRCA2 mutation.
The report also notes that while the UCSF team was made up of well-known and well-respected scientists, the TSA's response included no author credits, and there's no indication that it was written by any actual doctors or scientists. I'm still not convinced the medical concerns are that big of a deal (well, perhaps for TSA agents stationed near the devices...), but it is a bit troubling that the TSA isn't being particularly forthcoming on this stuff.