eBay x-ray tubes & justified fears (fwd)

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---------- Forwarded message ----------
Date: Sat, 4 Aug 2007 09:51:43 -0700 (PDT)
From: William Beaty <billb@xxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: eBay x-ray tubes & justified fears


> From: resonance <resonance@xxxxxxxxxxxx>
> If you think the word idiot is too strong, please consider the fact this
> moron was attempting to run a 120 kV X-ray tube out in the open air with
> virtually no shielding of any type.

Um...  In hospitals they aim those at people.  They did it to me, yet I'm
still alive.

:)

High-voltage hobbyists will notice many tempting x-ray tubes being
constantly listed on eBay.  I'd always assumed that they were lethal.
But I've recently been wondering about the genuine danger of common
sources of ionizing radiation, versus the hysterical overreaction typical
of Americans.  Ra-dee-ation!  "Any risk is too much risk?"  Yeah, right.
But specifically, if the radiation burns weren't an issue, perhaps the
cancer risk isn't as high as I've always imagined.  How much of our
opinion of x-ray tubes is based on reality?

For example, if you stand outside in unshielded sunlight for a couple of
hours, you receive a serious radiation burn, with skin peeling and falling
off.  Yet the cancer risk is quite small, and people in tropical countries
even ignore the problem entirely.  The effect might be mostly limited to
the outer 1mm layers.  But make no mistake, it's a genuine radiation burn.

If you take a geiger counter along on a cross-country airline flight, be
prepared for a surprise.  It starts clicking within seconds of takeoff.
At cruising altitude it roars: ten or twenty counts per second ( and
supposedly much higher during solar flares.)  But we aren't terrified of
air travel because of this.  Should we be?

If you look up the ratings for modern dental x-ray equipment, and
calculate the exposure needed for the mildest of x-ray burns, guess what
the exposure time is.  Seven thousand hours.  You'll heal too fast. You
can't get an x-ray burn from a dental unit; increased cancer risk is the
only danger, and it's the dental techs using the equipment every day who
should worry.  (And how does the risk compare with other real-world
acceptable risks, such as cancer from peanut butter, or the risk from
solar UV in outdoor employment?)

The USA is weird about x-ray tubes, but I'm starting to get skeptical
about the justification.  At the science museum in Paris, "Palais de
Decouvertes," there's an exhibit case with an unshielded Crookes-era x-ray
tube, a fluorescent plate, and a sample object.  Press the button, and you
see the green glowing image; bright enough that it's easily seen in a well
lit museum. The tube is behind the fluorescent plate, so the x-rays are
aimed at your face!  Maybe the cancer risk ridiculously insignificant.
Or is that museum exhibit a clear danger to the public?

Another example.  I was talking about "shoe fitting" x-ray machines from
the 1950s, and one local guy mentioned that he'd played with one of these
as a kid, and exposed himself for at least tens of hours.  He lived in a
boring small town.  The shoe store next to the movie theater had one of
those fluoroscopes.  Every weekend he and friends would stare at the live
moving x-ray images of their feet for minutes at a time until the salesman
chased them out.  So why isn't he dead?

Another one: a guy at work got a CAT scan, then went home and took out his
geiger counter.  He said that it sensed his body from many feet away, and
fairly roared when the GM probe was held against his chest.  How could
anyone survive such exposure?  Perhaps "roaring geiger counter" isn't a
very good test of cancer risk.

So here's the important questions:

  If intensity is below the threshold for x-ray burns, then what is
  the cancer risk from common x-ray sources?  Specifically, how does it
  compare with cancer risk of ionizing radiation which EASILY causes
  radiation burns: the risk of going outside in the sun?  Or how dangerous
  is an x-ray tube when compared with the risk of working outdoors, or of
  living in a tropical country and getting huge amounts of hard UV
  exposure every day?

  Also:  intensity being equal, (or if accumulated exposure is equal,) how
  much worse are x-ray frequencies when compared with solar UV?  I
  realize that UV produces surface cancers which are easily noticed,
  while x-rays cause hidden damage deep inside.  But ignoring that fear,
  how much worse for cancer risk is a dental x-ray tube when compared
  with a very dim UV sunlamp which cannot produce a sunburn?  Tens of
  times worse?  Thousands?  Or much less?  In other words, is our fear of
  low-power x-ray tubes justified?


And finally:

Just this year a research group discovered that x-ray cancer is not equal
for all humans.  The risk depends on genetics.  (This is contrary to what
everyone has always assumed.)  In a study of patients exposed to a dose of
head x-rays in the 1950s, the incidence of cancer was concentrated in
certain families.  Note that this was a major dose, one intended to kill
ringworm infections, and which caused hair to fall out.  People from
certain families got brain cancer.

  http://www.sciencenews.org/articles/20070519/toc.asp
  http://www.bioone.org/perlserv/?request=get-document&doi=10.1667%2FRR3329

This resembles the "moon children" problem, xeroderma pigmentosa, where
certain people who lack a DNA repair molecule will immediately acquire
skin cancer if they ever go outdoors in the sun.

Odd thought: perhaps humans are immune to x-rays, but people with a
certain genetic defect cannot tolerate even a small exposure, and this
population has biased our stats.

Odder thought: for Hiroshima-scale radiation exposure, I wonder if some
rare people never aquired radiation sickness.  Imagine if some "human
cockroaches" exist who would easily survive a nuke war.



(((((((((((((((((( ( (  (   (    (O)    )   )  ) ) )))))))))))))))))))
William J. Beaty                            SCIENCE HOBBYIST website
billb at amasci com                         http://amasci.com
EE/programmer/sci-exhibits   amateur science, hobby projects, sci fair
Seattle, WA  425-222-5066    unusual phenomena, tesla coils, weird sci