RE: ICRP/NCRP Risk Factor Use

["Fulmer, Philip" <philip.fulmer@cplc.com>]

Mike,

I would tend to think that neither interpretation would be correct.  As
you state in your premise, the risk factor is given in units of fatal
cancers per Sv.   Therefore, the product of the risk factor and the
effective dose is not a probability but is the number of fatal cancers
expected in the population, regardless of its size.  This obviously
presents some logical problems for situations when you have a population
that is not uniformly irradiated or a population with a small number of
people who receive such a high dose that the nonstochastic effects are
predominant.  

So in your example, based on some limiting assumptions I would say that
the interpretation is that in a population with a collective dose of 1
Sv, the expected number (not probability) of fatal cancers is 0.04 or is
much less than 1.  Therefore, we do not expect, though we may not rule
out depending on our philosophy on LNT, any fatal cancers in that
population.  In a population with a collective dose of 100 Sv (again
with some limiting assumptions), we would expect 4 fatal cancers in the
population.

If I'm off base, please let me know.

Philip

____________________
Philip C. Fulmer, PhD, CHP
philip.fulmer@cplc.com

>----------
>From: 	Michael S Ford[SMTP:MFORD@pantex.com]
>Sent: 	Monday, October 26, 1998 4:18 PM
>To: 	Multiple recipients of list
>Subject: 	ICRP/NCRP Risk Factor Use
>
>Question for the group:
>
>Given a risk factor of 4 E-2 fatal cancers per Sv and a collective dose
>of 1 Sv for a particular group, how is the resulting 4 E-2 fatal cancer
>risk interpreted?
>
>4 E-2 fatal cancer risk for each person in the group OR
>4 fatal cancers per 100 persons in the group, 40 per 1000, etc.?
>
>I had read previously -- ICRP and NCRP -- that the fatal cancer risk
>values only applied to populations not to individuals, but ICRP 26
>para 60 talks about *individuals* specifically.
>
>Thanks in advance for any information you may provide!
>v/r
>Michael
>*************************
>Michael S. Ford, CHP
>Radiation Safety Department
>Battelle Pantex
>Amarillo, TX
>806.477.5727 phone
>806.477.4198 fax
>mford@pantex.com
>*************************
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