Re: unuseful dental x-ray

["Dr. Marvin Goldman" <mgoldman@ucdavis.edu>]

>Steven Rima wrote:
>>
>>      Franz et al,
>>
>>      The point I was trying to make was one of credibility (ours!) and
>>      risks. I think we as a profession have a real credibility problem when
>>      we (at least the majority of us) tell people that 5 or 10 mrem is not
>>      harmful, and we (at least the majority of us) advocate a de minimus
>>      value of 50 to 100 mrem per year as being "below regulatory concern."
>>      At the same time we then talk about applying the ALARA concept to 5
>>      mrem and even talk about it being an illegal x-ray! (I would not
>>      expect any member of the public to trust a health physicist telling
>>      them that low level radiation is not really dangerous while that same
>>      HP refused a 5 mrem dental x-ray.) We can't have it both ways,
>>      folks!!!
>
>Amen.  After all of the discussion about the effects of low levels of
>ionizing radiation, ethics, etc.,etc. on radsafe, I would hope that most
>radsafers now have a healthy skepticism about the linear hypothesis as
>the basis for estimating real radiation effects at low doses.  True, the
>regulators still use the recommendations of the NCRP and ICRP as the
>basis for their regulations, but that doesn't say that those
>recommendations are in any way representations of reality.  I, for one
>would have no compunction about telling a patient, or anyone, that a
>dose of 5, 10, 100 or even higher millirem is nothing to be concerned
>about and carries no measurable risk.
>
>I think we have gotten ourselves into an impossible situation by our
>slavish adherance to the ALARA idea, just because a bunch of old men are
>afraid they might be wrong.  I still want data that demonstrate low
>doses are really harmful to humans before I will budge an inch from the
>idea that a little radiation is good for you!  Or, at least, is not
>harmful.
>
>I refuse to go along with the fiction that, just because you can't see
>or measure "it", doesn't mean "it" is not there.  I demand hard evidence
>before I will NOT do something just because someone is afraid it might
>be harmful.  And yes, that means I need bodies in the street before I
>will agree that low levels of ionizing radiation ARE harmful.  So far, I
>haven't seen any and I have seen a lot of evidence that says low levels
>either have zero effect or are beneficial and may even be essential to
>life as we know it.
>
>Now, all of this diatribe only applies to ionizing radiation about whose
>effects we know a lot.  It does not apply to any other insult that may
>be hazardous.  So, please don't try to feather me with the tobacco, or
>any other brush.  We are only talking about ionizing radiation here.  Oh
>well, you all know that I think this already, but maybe, there are some
>new radsafers who haven't heard it.  Onward and upward to the beneficial
>uses of radiation.
>
>Al Tschaeche antatnsu@pacbell.net

1.	 Since I was at my dentist today, I repeated this story to him and
asked if insurance companies really require radiographic documentation.
Answer was no.  Documentation was requested only in cases of payment for
one therapy strategy vs another which had a different cost.  But never on
whether dentures were needed for someone gumming their way through life.
Usually a letter is the only documentation needed.  He never heard of
requiring an x-ray to document an adental mouth.  I'd never permit it if I
was the patient!  Not because of radiation risk, but because of common
sense.

2.	The ranting on low level risks seems never to abate.  We all know
that the science of molecular biology still has given us no direct proof of
cancer risk (and it's only cancer risk in this debate), even though some
induced genetic and molecular markers in today's literature may be steps on
the way to a full understanding of all the mechanistic pathways and steps
from dose absorption to cancer manifestation.  Nor can anyone with any
understanding of epidemiology expect that epidemioogical approach can ever
show the risk from millirem sized doses even if the ICRP coefficients are
correct.   When it come to a religious belief level of discourse, rather
than objectiviely  interpreting a science data set, we all lose
credibility.

	The absence of "bodies in the street" proves nothing when dealing
with minute probabilistic risks.  For what it's worth, I have no problem
with the linear, no-threshold hypothesis as a model for regulatory policy.
I do have a problem with those who selectively plot data points along a
straight line and insist that it confirms the linear proportional risk
coefficient down to the last photon.  Counting "hypothetical bodies" at
microSv exposures is a way to play with collective doses, but it's not real
nor realistic.  Biology  just does not work that way, and in due course the
window of insight will open.  Sadly, support for the research to speed up
the opening of that window is limited, so we may have to be patient.  Until
then, I for one am satisfied with the conservative LNT philosophy, but not
the further subfractionation of the limits to ridiculous  operational micro
compartments.  As for the "true risk", to me at this time, the universal
curve of risk still looks sigmoid, with the region from about 0.1-0.2 Sv to
1-3 Sv appearing to be fairly linear.  Period!

	I realize that each of us has an opinion, that most are not ready
to change their opinion, and that  if the data were really there, this
issue might actually be settled, (if an issue can be said to ever be truly
settled).  It's not a matter of being an "old man worried that he might be
wrong", but whether the cold scientific data are tight enough.  To which
this old scientist says the data are good, but still not tight enough. I'd
welcome seeing an increase in the research dollars rather than substituting
an increase in reactive decibels.  But then I'm only one voice.

Marvin Goldman
mgoldman@ucdavis.edu