Re: LNT theories

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

On Wed, 8 Dec 1999, Otto G. Raabe wrote:
> 
> Recognizing these limitations, Cohen has tested the linear model that
> assumes that the occurrence of lung cancer as a result of exposure to radon
> in homes is proportional to the average radon air concentration in these
> homes. He has shown that it is not. His results cannot be discounted as
> caused by the ecological fallacy since, as we can see inductively: if the
> LNT model that he is testing is actually correct, then the distribution of
> the radon levels among the exposed persons at a given average concentration
> would not alter the overall occurrence of lung cancer. On the other hand,
> if the LNT model that he is testing is wrong (as he has shown), then the
> shape of the dose response curve that he has observed is not definitive and
> it becomes apparent that we need to known dose to each person to quantify
> the risk and the shape of the curve. Hence, the downward slope of his dose
> response observation may be an artifact.
> 
> This is my interpretation of Cohen's test of LNT. I hope Dr. Cohen will
> comment.

	--This is correct and is what I have been saying always,although I
do not like the word "artifact". The negative slope in the dependence of
lung cancer rates in U.S. counties on average radon exposure in those
counties is certainly true, but it cannot be
interpreted as a risk to individuals vs their cancer risk if the linear-no
threshold theory fails (as I have shown). To understand this, consider the
situation if there were a sharp threshold for radon-induced lung cancer:
the lung cancer rates in counties would depend on the fraction of the
population exposed above the threshold, which might vary from county to
county in a very different way than the average exposures.
	In summary, my data shows that linear-no threshold theory fails
very badly, grossly exaggerating the risks of low level radiation. (The
last phrase requires more justification, which I can provide if this is an
issue). I have never claimed that my data demonstrate hormesis which would
be the interpretation of a negative slope in risk vs dose to individuals.

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


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