ICRP and LNT

[rkathren@tricity.WSU.edu (Ron L. Kathren)]

It was not the ICRP that brought the LNT to the fore in 1959.  Actually, as
was pointed out in "Pathway to a Paradigm:  The Linear Nonthreshold
Dose-Response Model in Historical Context" (Health Phys 70:621-636, 1996)
the watershed was actually NCRP Report 17 published in 1954.  This was
followed by UNSCEAR who gave some credence to the LNT in their 1958 report.
The following year the NAS/NRC put forth the applicability of the LNT.
Implicit in all of these reports was the understanding that the LNT provided
an upper limit estimate of risk.  The 1955 and 1958 ICRP recommendations did
not really make a statement about the LNT.  Indeed, the discussion of
leukemia in radiologists implied that there was a threshold, while noting
that the most conservative aspproach would be to assume no threshold and no
recovery.  This was as close to the LNT as they got.  However, the revision
to the 1958 recommendations, published in ICRP Publication 6 (1959) did
state that any dose MAY carry some risk (the operative word is 'may') and
assumed what was basically the LNT for protection purposes, also
recommendation that doses be kept "as low as practicable".  ICRP further
noted that while the dose rate independent LNT had been 'generally accepted'
for genetic mutations, new data suggested a dose rate effect.  Reading ICRP
6 leaves no doubt that genetic mutations and possible somatic effects
(leukemia and life shortening were specifically called out) were the
drivers, not solid tumor carcinogenesis.

Boy, would I like to revise and expand the "Pathway"!!!!!

Ron Kathren



  01:58 PM 2/16/99 -0600, Reynolds, Harold wrote:
>I agree completely with Al Tschaeche's post on ICRP.  What I don't agree
>with is other posts (which I somehow lost) stating that ICRP had CLEARLY
>bought into LNT by 1959.  When they use statements such as "conservative",
>" effects of low doses are not known" and "for the purposes of radiation
>protection",  I take that to mean that they were saying (to paraphrase) that
>in the absence of evidence either way we should use the most conservative
>assumption (LNT) for the purpose of protecting the workers, the public and
>the environment. To my thinking, that does not indicate CLEARLY buying into
>LNT as a fact.  If they had had the information we have now, I wonder if
>they would have taken a different tact?  I wonder what the authors of that
>original position think about the extremes to which it has been taken.  Is
>my logic flawed -am I using selective reading to come to an interpretation
>that agrees with me just as the proponents of LNT use the reverse reading?
>Are we all just seeing what we want to see?
>
>Harry
>Harold.Reynolds@RFETS.gov
>303.966.2708
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