RE: ICRP/NCRP Risk Factor Use

[per.hall@mep.ki.se (Per Hall)]

Dear Mike and Philip
I thought that the excess cancer death of 4% / Sv should be interpreted as
a lifetime excess increase of 4 percent.  If 1000 individuals are exposed
to a collective dose of 1 Sv and life time cancer risk is approximately
30%.  Lets assume that half of those patients die, this will give 150
deaths due to cancer and an excess of 6 (150*0,04) deaths caused by
ionizing radiation.
It is obvious that the 4%/Sv is a very rough and uncertain estimate as
underlined by both of you.
Regards, Per


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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Best regards,

Per Hall, MD, PhD                          Tel: +46 8 728 6152
Dept. of Medical Epidemiology        Fax: +46 8 314957
Karolinska Institute                          e-mail: per.hall@mep.ki.se

PO Box 281
SE-171 77 Stockholm
Sweden


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