Re: What is Safe

[David W Lee <lee_david_w@lanl.gov>]

Harry's post neglected to state which ICRP document(s) he
was "recollecting" from.  The primary ICRP document that I
am aware of from the 1959 era is ICRP Report No. 1 which was
"adopted" by the ICRP in Sep 1958 and published in 1959. 
This document is the one in which the ICRP changed the maximum
occupational annual dose limit from 15 rem/yr (whole-body) to 5 rem/yr
with the old 5 (N-18) dose bank account and the maximum 3 rem/qtr limit,
etc.  Page 4 of this document CLEARLY indicates that the ICRP, by
this time, had swallowed the LNT hook, line, and sinker; the ICRP
repudiates the possibility of a dose induction threshold for leukemia and
states that "...the most conservative approach would be to assume
that there is no threshold and no recovery"; that the induction of
leukemia is strictly a linear function of dose only without any
threshold.  This document, however, does not state or imply that the
5 rem/yr MPD for a working lifetime equates to risk associated with
hazardous occupations.  It is my understanding that the ICRP did not
explicitly introduce risk into the primary dose limits until ICRP 26/30
which introduced "weighting factors" as the means by which the
long-term risk of the induction of a fatal cancer was expressed. 
This document also CLEARLY indicates that the ICRP was of the conviction
that radiation exposure produced genetic effects in humans, even though
no deleterious genetic effects (as opposed to teratogenic effects) in
human populations have ever been documented (page 5 and page 8). 
This document was also the one which recommended pre-employment medical
exams to include complete blood counts/leukocyte counts as well as
periodic medical exams, despite the fact that any such blood test or
medical exam, as best, can only detect clinically depressed leukocyte
counts directly attributable to ionizing radiation resulting from
whole-body, acute doses of 25 to 50 rads or greater, i.e., such blood
tests were useless then at 5 rem/yr  dose rates and still are. 
Best regards  David


At 02:25 PM 2/11/1999 -0600, you wrote:
>If I remember my studies of radiological history correctly, when
ICRP
>adopted LNT/ 5 rem/yr/ ALARA in 1959 their reasoning was that based
the fact
>that using LNT, 5 rem/yr for a working lifetime equates to risk
associated
>with hazardous occupations.  If that level of risk was
acceptable in other
>occupations, it should be acceptable as a maximum for rad
workers.  However,
>in order to reduce this risk, all radiation doses should be ALARA and
none
>without positive benefit.  Their document also carried a
statement to the
>effect that while risks associated with large does are well
understood, the
>risks of low level doses are not known.  It also states that
LNT/ALARA are
>recommended "for the purposes of radiation
protection."
>
>Harry
>Harold.Reynolds@RFETS.gov
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DAVID W. LEE
Los Alamos National Laboratory
Radiation Protection Services, ESH-12
X-Ray/Source Control Team Leader
PO Box 1663, MS K483
Los Alamos, NM  87545
PH:   (505) 667-8085
FAX:  (505) 667-9726
lee_david_w@lanl.gov