Monday, December 6, 2010

Backscatter, Melanoma, and The Academy

The NAS had written a report on backscatter which was long and in places tedious to the extreme. A more succinct paper is in a letter by a few physicians and scientists at UCSF which was sent to the White House and appears on its Web Site. Strange that this has not gotten much attention but seems to stay on the site.

The letter states in part:

The physics of these X-rays is very telling: the X-rays are Compton-Scattering off outer molecule bonding electrons and thus inelastic (likely breaking bonds).

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.

This is what we said a year ago. The comparison to flying in an aircraft is nonsense. X rays have unique photon frequencies matched to bond lengths of certain control elements of melanocytes.

They continue:

Our colleagues at UCSF, dermatologists and cancer experts, raise specific important concerns:

• A) The large population of older travelers, >65 years of age, is particularly at risk from the mutagenic effects of the X-rays based on the known biology of melanocyte aging.

Yes, that is what we said a year ago! Specifically demethylation of control pathways in melanocyte control.

Then they state:

Moreover, there are a number of ‘red flags’ related to the hardware itself. Because this device can scan a human in a few seconds, the X-ray beam is very intense. Any glitch in power at any point in the hardware (or more importantly in software) that stops the device could cause an intense radiation dose to a single spot on the skin. 

This is the problem, the scanners are flying spot scanners using low power x rays which can accumulate and the systems seem prone to failure.

They conclude:

In summary we urge you to empower an impartial panel of experts to reevaluate the potential health issues we have raised before there are irrevocable long-term consequences to the health of our country. These negative effects may on balance far outweigh the potential benefit of increased detection of terrorists.

However if it is another NAS study it would be worthless. It must be an in vivo study where the pathways are studied as well!

Of course the FDA responded to assure the White House that there is no such problem. This is the FDA folks, that means pure unmitigated politics.

The FDA states in its letter:

However, the concern that “the dose to the skin may be dangerously high” is not supported. The recommended limit for annual dose to the skin for the general public is 50,000 μSv9. The dose to the skin from one screening would be approximately 0.56 μSv10 when the effective dose for that same screening would be 0.25 μSv11. Therefore the dose to skin for the example screening is at least 89,000 times lower than the annual limit.

The data they rely upon is:

NCRP report no. 116 Limitation of exposure to ionizing radiation (1993), page 56

This 1993 report is two decades old and fails to deal with pathway damage, it was not known then! That is the issue. And that is the issue that FDA grossly neglects. The letter concludes:

In summary, the potential health risks from a full-body screening with a general-use x-ray security system are miniscule. Several groups of recognized experts have been assembled and have analyzed the radiation safety issues associated with this technology. These experts have published recommendations, commentaries, technical reports, and an American national radiation safety standard as a result of their analyses.

This is in my opinion the height of arrogance. What tests are done. I have been on these panels and staff, often Government controlled, write the report sections, and the battles over words can often be intense but are won by who controls the report. The UCSF people have a clear and well founded concern that is dealt with by the equivalent of a clinical study. That is supposed to be the FDA's duty but alas with the current administration there is no such professionalism in my opinion.

For example from the FDA's site:

In 42 minutes of ordinary living, a person receives more radiation from naturally occurring sources than from screening with any general-use x-ray security system. 

This is a simple example of the ignorance and arrogance of Government workers in my opinion. They are comparing apples and oranges. Cosmic rays are not x rays and especially x rays of specific wavelengths and scattering in a Compton mode will cause specific bond breaks that start a process in certain people that may very well lead to cancer. Thus if such be the case, then perhaps it would be worth a study. Comparing Hiroshima survivors again and again is not comparing this global petri dish experiment that TSA has set itself upon.