Nonlinear alphas

[David Scherer <scherer@uiuc.edu>]

OK, it wasn't my last try.  Melissa is back in town and she tells me that
the problem is using the word *From* as the first word in a paragraph.  She
says *To* will give similar results.  Thought you all might like to know.

Dave

>
>Based on <From> the conversation on radsafe it would appear that many of
the studies that refute the linear model involve alpha exposure.  If these
studies are replicated, then carcinogenic response to alpha radiation would
be nonlinear.  Does that imply that response to low LET radiation is also
nonlinear?
>
>Basically, I'm questioning the practice of combining radiation doses via
the dose equivalent, H=DQN, for cancer risks.  Perhaps low LET radiation is
linear and high LETradiation is not.  Wasn't the original idea for the rem
based on cell survival curves at relatively high doses/dose rates?  Maybe
this simple relation breaks down for cancer induction.
>
>B. Cohen pointed out that LNT for radon exposure is based on linear
extrapolation from miner studies, regardless whether the biological insult
is cell killing or something else.  I was simply suggesting one possible
mechanism that could result in a difference from low LET radiation and
result in different dose-response curves for the two types of radiation.  If
there is substantial cell killing with alpha radiation at low doses, but not
with low LET radiation at low doses, there could be two competing outcomes
for alpha radiation, one carcinogenic and one not.  (As I said before, dead
cells do not become cancer.)  The combined response might be non-linear.  If
there is litle or no cell killing with low LET, cancer induction might be
linear.
>
>Neither of these points was intended to be a serious proposal based on a
literature review or original research.  (After all, this is the talk radio
of HP.)  Rather, it is a simple suggestion to provoke discussion.  I expect
that some of the people who developed the concept of dose equivalent could
comment on whether there is a solid basis in the case of cancer induction or
whether it was just a simplifying assumption that somehow got etched in
stone.  I could probably consult a textbook, but it's more fun to get the
personal perspectives through this interactive medium.
>
>Regards,
>Dave Scherer
>scherer@uiuc.edu
>