Re: threshold versus collective dose

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

On Fri, 3 Sep 1999, Karam, Andrew wrote:

> With regards to the recent posting by Mr. Hofmeyr, I would like to comment
> only on the idea of collective dose.
> 
> Using the concept of collective dose, I can claim that throwing a 1 gram
> stone at each of a million people will result in crushing one of them to
> death because dropping a 1000 kg rock on one person will crush him/her.  In
> my opinion it is as ludicrous to apply the concept of collective dose in the
> case of trivial exposures to radiation as it is to apply it to trivial
> physical insults such as being struck with a tiny rock.  It makes the math
> easier, but what good is done by having a mathematically simple model that
> is incorrect?  

	-While I agree with the sentiments of this message, the analogy
with the 1000kg rock is really not quite fair.While the rock situation was
always clear, there was originally good reason to believe that a linear-no
threshold behavior was appropriate for radiation. The number of cancer
initiating processes is clearly linearly proportional to dose. It is only
in the last 10 years or so that evidence came to light that biological
defense mechanisms are extremely important in determining risks, and that
these are affected by radiation -- in most cases, they are enhanced by low
level radiation. How "The Establishment" in the Radiation Safety
community, such as NCRP Committee 1-6, can ignore this very large body of
new evidence mystifies me and leaves me badly disheartened. But still, we
should recognize that they originally had good evidence supporting their
position, so the 1000kg rock analogy is unfair to them.



> 
Bernard L. Cohen
Physics Dept.
University of Pittsburgh
Pittsburgh, PA 15260
Tel: (412)624-9245
Fax: (412)624-9163
e-mail: blc+@pitt.edu


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