Re: Fw: Question on low-dose rad effects

[Bernard L Cohen <blc+@pitt.edu>]

	This problem goes much further. The cancer risk per rad is about
the same for a 30 gram mouse as for a 70,000 gram man, and I would bet it
isn't much different for an elephant.The answer must be that initiating
events are not controlling, as might be expected from the fact that we get 
far more single strand and double strand DNA breaks from chemical and
thermal processes than we do from any reasonable radiation exposure. The
controlling factor must be biological defense mechanisms.

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, 12 Oct 2000, Jerry Cohen wrote:

> 
> 
> 
> 
>      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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