Re: Cohen's ecological data: a test of LNT?

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

On Tue, 14 Mar 2000, Ken Mossman wrote:
>  
> It remains unclear to me how Cohen’s ecological data can be used to test LNT
> (or any other predictive theory).

	--That is explained in detail in my 1995 paper in Health Physics.
Briefly, LNT (for individuals) is used to derive mathematically a
relationship between county lung cancer rates and average radon exposures
in those counties. Data are provided for these, and these data show that
the predicted relationship is not fulfilled.

>  Cohen states that case-control studies“ investigate th
>  causal relationship between radon exposure and lung cancer,
> whereas our work has the much more limited objective of testing the linear
> no-threshold theory” (Health Physics, Volume 72(4), page 625, April 1997).
> It is absurd to suggest that testing the LNT theory is not a test of a
> causal relationship. The LNT theory, in this context, only has meaning if
> radiation causes cancer. If Cohen’s work does not test for a causal
> relationship, how can his data be a test for LNT (or any other predictive
> theory)?    
> 
	--LNT is a *special case* of a causal relationship. It is clearly
possible to have a causal relationship without having a linear-no
threshold (LNY) relationship. For example, there could be a quadratic, a
threshold, etc. My study tests LNT as a special case of the causal
relationship; it finds that LNT fails that test, grossly exaggerating the
risk of low level radiation. That is as far as I can interpret the data.

>Cohen goes on to say  “We haev never claimed  that low level exposure to
>radon 
> is protective against lung cancer” (Health Physics, Volume 72(4), page 625,
> April 1997). If the data refute LNT then what do the data support if not
> hormesis (as suggested by the strong negative correlation for radon
> concentrations <150 Bqm-3)? Cohen cannot have it both ways.
>
	--I fail to follow the logic here. I am not able to use my data to
determine the dose-response relationship for individuals. To do so would
fall into the trap of "the ecological fallacy". All my data do show is
that LNT (for individuals) grossly exaggerates the risk from low level
radiation. That conclusion avoids "the ecological fallacy". Why is it
"having it both ways" to conclude that LNT is wrong, but my data cannot
determine what is right?

> Cohen quotes Richard Feynman in support of his test of LNT. According to
> Feynman “we look for a new law by the following process: first we guess at
> it. Then we compute the consequences of the guess to see what would be
> implied if this law we guessed is right. Then we compare the result of the
> computation with observation to see if it works. If it disagrees with
> experiment [the law] is wrong. In that simple statement is the key to
> science. It does not make any difference how beautiful your guess is. It
> does not make any difference how smart you are, who made the guess, or what
> his name is-if it disagrees with experiment it is wrong. That is all there
> is to it.” (Health Physics, Volume 72(4), page 624, April 1997). Implied in
> Feynman’s statement is that the data provide a bona fide test of the theory.
> If the data are erroneous (e.g., use of faulty data analysis, use of
> inappropriate statistical tests, use of inappropriate experimental methods)
> then the data do not provide a test of the theory even though the data, on
> its face, might suggest the theory is wrong. 
> 
	--Obviously if the data or the analyses are faulty, any
conclusions from them are unreliable. Therefore the discussion should be
about what might be wrong with the data or the analyses. I have been
searching for possible problems for many years without finding anything,
and that is why I am offering rewards for help in this search.
> 
Bernard L. Cohen
Physics Dept.
University of Pittsburgh
Pittsburgh, PA 15260
Tel: (412)624-9245
Fax: (412)624-9163
e-mail: blc+@pitt.edu


************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html