Re: Question on low-dose rad effects

["Ron L. Kathren" <rkathren@tricity.wsu.edu>]

Bernie --

We asked that question many times; in theory, it would seem, that a larger
animal with more irradiated cells would be a larger risk, assuming the risk
per unit dose was constant (in other words, the risk per energy deposition
per unit mass).  To test this hypothesis, when i was Director of the USTUR
(please note I retired July 7) I asked my colleague Barry Jacobson, to look
at  data that were available through the National Radiobiology Archives,
specifically examining lung cancer in dogs given Pu intratracheally under
controlled conditions and to evaluate whether  the larger dogs who
presumably had larger lungs and hence more cells had a higher incidence of
lung cancer for a given dose.  The results were inconclusive  -  we could
not prove or disprove the hypothesis.  But I believe that further study is
warranted  -- there should be enough good dog data available to come with a
meaningful conclusion.

Ron Kathren
-----Original Message-----
From: Bernard L Cohen <blc+@pitt.edu>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Date: Friday, October 22, 1999 7:45 AM
Subject: Re: Question on low-dose rad effects


> An extension of the question asked here is why does a 25 gram
>mouse have the same risk as a 100,000 gram person for a given energy
>deposit per gram? I would bet that elephants also have similar risk.
>
>Bernard L. Cohen
>Physics Dept.
>University of Pittsburgh
>Pittsburgh, PA 15260
>Tel: (412)624-9245
>Fax: (412)624-9163
>e-mail: blc+@pitt.edu
>
>
>On Thu, 21 Oct 1999, Jerry Cohen wrote:
>
> Dear Radsafers,
>      Perhaps someone could enlighten me on something that has puzzled me
for
> a long time. Why is the degree of harm, detriment, etc. from low-level
> radiation  expressed in terms of rad, rem, sieverts, etc. which are
> functions of absorbed energy per unit mass (i.e. ergs/gm)?
>  Isn't the probability of a mutation, or other adverse effect a direct
> function of the total number of ionizing events occuring in the vicinity
of
> suseptible DNA molecules and isn't that ,in turn, a function only of total
> absorbed energy?
>      For example, consider two individuals of the same age, sex, and
general
> state of health with the only difference between the two being that one
> weighs twice as much as the other.  Given that both recieve a radiation
dose
> of say 1.0 rem, have they both experienced an equal degree of harm? Due to
> his/her larger mass, the heavier individual gets twice as many ionizing
> events occuring near twice as many DNA molecules any one of which might
> result in an adverse mutation.  Why doesn't the individual with twice the
> mass, get twice the risk???     Jerry Cohen
> jjcohen@prodigy.net
>
>
>
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