TPM Reader TT chimes in on the safety issue. Before getting to TT's comments, let me say that despite the fact that there are no levels of ra
I just wanted to weigh in on several points on the new TSA scanners and procedures as a scientist and as someone that frequently works on homeland security topics. First, as any scientist can attest, that one of the major training messages in radiation safety courses is to always minimize the dose of ionizing radiation. There is NO safe level of ionizing radiation (there are three major types of ionizing radiation: alpha particles [helium nucleus], beta particles [electrons], and gamma rays [short wave, high energy electromagnetic waves]). Nada. Zip. None. Argonne National Lab did studies in the 1950s-1960s on many generations of beagle dogs to determine if there was a safe, minimum exposure level. The theory was that radiation exposure was like chemical exposure in that at some point the dose is so low that no damage occurs. The evidence proved otherwise. Also, the damage from ionizing radiation is cumulative, so frequent or repeated exposures have much longer lasting effects. The US and other governments have set some standards to limit radiation exposure for workplace and health safety, but there is no lower threshold dose that does no damage.
The TSA pulls a couple intellectual "sleights of hand" in its discussion of these machines. First, the TSA website compares the dose of radiation received from the machines to the radiation from cell phones (I will note this comparison is for the millimeter wave machines, not the back scatter variety). This is not a good comparison and may lead to confusion about the two different types of machines being used. Cell phones emit radio waves. Radio waves, while electromagnetic waves like gamma radiation, are much longer and of significantly lower energy, and, thus are not ionizing radiation. That is, they do not have the ability to damage DNA and to cause cancer. I can put a flask of cells next to a radio wave emitter and the cells will grow just fine and not accumulate any additional mutations from that exposure. Second, the TSA often compares the radiation from the back scatter machines to chest X-rays or cosmic radiation. These are much higher energy and typically pass through the body, so the dose is more diffuse and over a much larger part of your body. The back scatter radiation from the scanners is lower energy, but still ionizing, so the exposure is concentrated within a small amount of your body (the top layers of skin). This could potentially increase the effective exposure by 10-100-fold over what the TSA is saying. This second point is the one that the UCSF letter discusses in much greater detail.
The TSA also admits that the ionizing radiation penetrates through 1/10 of an inch of the skin. While that might not sound like much to many lay folks, that is actually quite significant. There is A LOT going on in your skin at 1/10 of an inch. To expose that layer of skin to increased ionizing radiation will lead to increased damage and the potential for mutations and ultimately cancer. It would take years to figure this out and maybe that is what the TSA/DHS is hoping for...the fog of epidemiology to hide the true health impacts. Look how long it took for the risks of smoking cigarettes, with a clear danger, to become well accepted with tons of independent data confirming the point.
The FDA response to the UCSF letter basically says, "the machines are below the threshold of an arbitrary dose limit we developed with the help of the manufacturers of these machines."
Source:
http://www.talkingpointsmemo.com/archives/2010/11/the_safety_question_pt2.php
So as the FDA says, we can trust the manufacturer. After all they do not have a vested interest or anything....