LNT and medical X-rays

[goldinem@SONGS.SCE.COM]

Heard a short news item on the radio this morning that the FDA is going to

consider whether or not to declare medical x-rays as a possible carcinogen.

The news note was very short and didn't explain the reasoning or

justification and certainly didn't delve into the consequences.

Personally, I believe such a designation could scare more people away from

clearly beneficial uses of radiation (simple x-rays) and will serve to

support lawsuits involving trivial exposure levels.  ("Oh Doctor, you

didn't diagnose my cancer, you caused it.  My attorney will be touch.")



I'm not convinced that low doses have a threshold, nor that they are

beneficial simply by stimulating the immune system.  IMHO, it appears that

DNA damage from high LET radiation must be different (multiply damaged

sites) from that caused by oxydative metabolism (refer to Dr. John Ward's

work at UC San Diego).  And if low LET radiation doesn't cause damage any

different than natural processes, how then can low level radiation exposure

stimulate the immune system (see Dan Billen's excellent paper on relative

damage rates)?  The damage must either be different (to cause an effect) or

must be the same and at trivial levels.  If low dose low LET radiation can

stimulate the immune system, why then can it not be responsible for

advancing carcinogenesis but at sufficiently low risk to be unimportant?

If there are competing processes (DNA damage and immune system

enhancement), there is probably even more that we don't yet understand

about the dynamics.  I don't believe epidemiological studies will be able

to answer those questions.



Anyway, those of you with credentials and those in federal government

service should consider weighing in on the FDA proposal.  It's taken

decades to convince many journalists and the public that low radiation

exposures (in the range of diagnostic x-rays) are safe (if nothing else,

consider the public dose limits in Part 20).  Having the Government declare

those same x-rays as carcinogenic will undo what little understanding is

out there.  And it'll be the wrong message and a misdirected focus.



Y'all have a good New Year.



Eric M. Goldin, Ph.D, CHP

<goldinem@songs.sce.com>







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