TSA and X-ray Physics
(Originally posted on November 29, 2010 by Dr. Bill)
The biggest travel days of the entire year are upon us, and the hottest subject of media attention is the controversial airport security screening practices that are being carried out by the Transportation Security Authority (TSA).
Anyone traveling by commercial airlines flying out of most airports is faced with the choice of two screening procedures. They can either submit to full body X-ray imaging, showing the individuals anatomy in intimate detail, or they can “opt out” and thus have to submit to a very personal “pat down” which includes the manual exploration of everything including breasts and genitalia.
Many people take exception to the idea of both practices as being an extreme invasion of privacy and a health hazard. Others justify the procedures as necessary to protect the public from terror threats.
Others express concerns over the dangers of radiation exposure, and consequent cancer risk caused by the screening machines. This charge is summarily dismissed by TSA officials who claim that their screening machines create minimal or “low level” radiation exposure. They go on to claim it causes little if any public risk. They say that the X-ray exposure is comparable to that which passengers are exposed to in an hour or so when flying, and that is supposed to make it acceptable.
Nowhere in this debate have I heard any discussion of the physics of X-rays and how it effects the human body. As a chiropractor with extensive education and experience in the use and effects of X-ray, I can assure you that they are indeed dangerous. I take exception to the TSA’s claim that the ‘low level” of X-rays generated by their machines are not in any way harmful.
My opinion is based on my knowledge of the physics of x-rays. There are three factors involved in the production of x-rays. They are miliamperage, kilovoltage, and time.
Milliamperage is the measure of the actual amount of X-rays produced.
Kilovoltage is the measure of the electrical power propelling the X-rays.
Time is the duration of X-ray production or exposure.
The characteristics of the image produced by X-rays are dependent upon the combination of the above factors adjusted to produce the desired quality of image.
The cleanest X-rays are produced by a combination of low milliamperage or a small amount of X-rays, powered by high kilovoltage for the least amount of time, dependent upon the thickness or density of the subject to be imaged. This is known as a high Kvp, low Mas technique.
This is the kind of x-ray technique chiropractors use to get finely detailed images of the spine for bio-mechanical analysis. The benefit to the patient is a minimal amount of time exposure to a minimal amount of ionizing radiation.
X-rays penetrating human tissue under high power for a short duration of time are the least damaging. The image produced in this manner comes from a small amount , but high percentage of the X-rays produced, reaching the imaging material. This minimizes what is known as scatter radiation.
Scatter radiation does not penetrate the tissue, but is absorbed by it , damaging it, effecting it’s cellular structure and DNA. This causes it’s carcinogenic effect.
X-ray images such as those produced by the airport screening machines can only be produced by a low kilovoltage (power), high milliamperage (a lot of X-rays), and a long exposure time.
The length of exposure time is the major factor in determining how much damaging radiation a person is subjected to. The other factor is that the minimal penetration by Xrays necessary to produce the detailed full body image coincidentally produce a maximal amount of scatter radiation, due to the fact that a relatively few of the X-rays pass through the body and most are absorbed and are therefore damaging.
A properly exposed spinal X-ray is taken in a fraction of a second. The X-ray beam is collimated or limited to expose only the part to be imaged.
The airport screening X-rays expose the whole body for as much as 30 or more seconds. That is an unacceptable amount of radiation to expose people to. Read more about the damaging effects of X-rays, in an article, Protect Your DNA from CT Scans and X-rays, by Robert Klein published in the August 2010 issue of Life Extension.
In summary, it is the multiple levels of X-ray penetration of body parts that produce the intimately detailed full body image. This can only be done by a long “dirty” exposure to damaging radiation.
It is important to note that x-ray exposure is cumulative, making it a real health liability to frequent flyers and airline personnel. However the health liability to the occasional flyer should not be overlooked and must be considered in the context of other sources of radiation exposure, such as medical X-rays and CAT scans.