X-rays come in many flavors from hard to soft with hard being the most penetrating.  All x-rays are ionizing radiation this means the x-ray photons break DNA, chemical bonds by dislodging electrons and generate destructive free radicals.   Backscatter x-ray uses the Compton Effect to reflect or scatter x-rays back to detectors.  Writers for DHS assume incorrectly that x-rays don't pass through the body because detectors are not placed opposite the person.

FIG. 1  Back-Scatter x-ray Compton Effect

Fig. 2 below is a graph of x-ray absorption or attenuation rates for breast/testicle tissue for various x-ray energies.  Soft tissue readily absorbs soft x-rays used in back scatter systems. The same tissue is relatively transparent to medical imaging x-rays 80-120Kv and hard x-rays. 

Fig. 2 NIST Breast/ Testicular tissue x-ray absorption rates

Backscatter x-ray systems use a complex mechanical assembly to sweep an intense pencil beam of x-rays head to toe.

Fig. 3 Basic Back Scatter Assembly

The x-rays leave a trail of damaged DNA and cells from head to toe. Most x-ray are absorbed by the body tissue a small fraction is back-scattered or reflected like a window back to special detectors.  The twelve year old fuzzy public images below reveal a great deal.  

FIG. 4 Back-Scatter x-ray (complements of AS&E)

If you inspect the lower leg and arms of the man shown you will see "bone shadows".  This is a result of the x-rays penetrating the skin and being absorbed by the underlying bones, the same shadow is seen on the top of the head showing the skull.  Fewer x-rays are being "back scattered" from the bone making this region dark in the image.  Clearly the x-rays penetrate the skin and reach bones and deeper radio sensitive tissues such as ovary, testicles. thyroid, breast and eyes.

All of the press releases and DHS official statements that the x-rays are safe, insignificant, don't penetrate the skin don't agree with physics 102.  The general use of ionizing radiation for general security screening is dangerous to public health.

New forward scatter systems being installed generate high resolution images like the one below, we are told is not very penetrating.  And the dose is only 15 minutes in a plane.  What do you think?? 

Fig 5. Forward Scatter x-ray "Total Recall" security system.

Are you the one in twenty that has BRCA1 gene DNA repair issue making you more prone to cancer?

Jeff Buske CTO Rocky Flats Gear Inventor, electrical engineer, defender of privacy and DNA.