From: sbharris@ix.netcom.com(Steven B. Harris)
Subject: Re: Which is more dangerous: radiation or electricity?
Date: Mon, 01 Dec 1997
Newsgroups: alt.folklore.science,sci.physics,sci.chem,sci.energy,
	sci.space.policy,sci.astro,sci.med

In <65s6mk$73q$1@news.fsu.edu> jac@ibms48.scri.fsu.edu (Jim Carr)
writes:

>>But what
>>if you absorb 300 rads over the course of 30 years?  You'll probably
>>have an increased risk of cancer, but will you die the same death you
>>would have died had you absorbed the radiation in one flash?
>
> Not the same death, but you will have a very high cancer risk.  I
> don't have those numbers handy today, but maybe Dr. Harris has
> them.


   From the Hiroshima data it is assumed that you need something like
20-50 rem (these days you use Sieverts; 1 Sv = 100 rems) to really see
an increase in cancer in the stats (it's not known if there is a
threshhold effect).  Over the remainder of a lifetime for an "average"
adult (40 years) you expect to see something like 10 excess cases of
leukemia per 1000 people at 100 rem.  For all other cancers, maybe 50
per 1000 people at 100 rem.   That gives you a total of 60 deaths/1000
people at 100 rem.  These are cancer rates for single (all at once)
delivery with latencies of 3-5 years for leukemias and several decades
for the solid tumors of organs.

   I'm not completely sure how to scale this up.  There is a pretty
linear increase in solid cancers/dose, but the relationship for
leukemia is quadratic and goes up a bit faster.  Being concervative, we
could guess that 300 rem would give you 180 excess cancer deaths per
1000 people over 40 years.  In other words, this dose has an 18% chance
of giving you a cancer you wouldn't otherwise get, and probably a few
decades down the road, whereas the chance of killing you is a lot
higher if 300 rem is given to you all at once (natural background, for
reference, is about .36 rem per year).  Delivering any radiation dose
in fractons rather than all at once might result in slightly fewer
deaths (due to repair between hits) but probably not that much fewer.
I seem to remember that late cancer risk isn't affected that much by
fractionation.


                                      Steve Harris, M.D.