Re: Re[2]: Nonlinear alphas

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

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, 1 Aug 1996 te_hui@ccmail.pnl.gov wrote:

>      Correct me if I am wrong, but if the probability of not killing a cell 
>      is p, then it would be difficult to convince me that the probability 
>      of N alpha not killing the cell is N x p.  Shouldn't the probability 
>      of surviving the alpha hits goes down instead of up?

----The N multiplies the quantity (p x q), which is the probability of a 
single alpha particle not killing the cell and causing a cancer. 
Normally, p is very close to 1.000 (or all our cells would be dead and we 
would be dead) and q is very much smaller than 1.0 (same reason). I 
concede that if these conditions were not fulfilled, my treatment would 
have problems. 

>      
>      Edmond Hui
>      PNNL
> 
> 
> ______________________________ Reply Separator _________________________________
> Subject: Re: Nonlinear alphas
> Author:  blc+@pitt.edu at -SMTPlink
> Date:    8/1/96 9:30 AM
> 
> 
>         If the principal mechanism for cell killing is passage of a
> single alpha particle, the probability for a cell to be killed must be 
> linearly proportional to dose. If a single alpha particle has a
> probability of not killing a cell = p and a probability of causing a cancer 
> if the cell is not killed =q, the probability of it causing a cancer is
> p x q. Then the probability of N alpha particles causing a cancer is 
> N x p x q, which is proportional to N, and therefore linearly 
> proportional to dose.
>      
> 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, 1 Aug 1996, David Scherer wrote:
>      
> > 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
> >
> > >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.
> > >Dave Scherer
> > >scherer@uiuc.edu
> > >
> >