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RE: Field's comments on Cohen's Observation
Dr. Bill Field wrote:
-----Original Message-----
From: epirad@mchsi.com [mailto:epirad@mchsi.com]
Sent: Monday, June 16, 2003 9:06 AM
To: BERNARD L COHEN
Cc: radsafe@list.vanderbilt.edu
Subject: Re: Cohen's Observation
Dr. Cohen,
<snip>
The reason I enter this debate is not about ego, but rather because so many
people including knowledgeable HPs and Physicists misinterpret your findings
to indicate prolonged residential radon exposure does not cause lung cancer
(eventhough the vast majority of case-control studies indicate it does). You
have stated yourself ecologic studies can not assess risk. This needs to be
stated by you more often. While ecologic studies can not assess causality,
analytic epidemiology studies (such as case-control studies) do have the
ability to establish causality.
If you would have found a positive ecologic association between radon and lung
cancer and used that to state this proves the LNT is valid, I would be just a
fervent in my opposition in you using it to test the LNT because of the
limitations of the ecologic design. This debate has not been about the
validity of the LNT, this debate has been about the limitations of ecologic
studies. You state the limitations inherent in ecologic studies do not exist
if you use an ecologic design to test the LNT, no knowledgeable epidemiologist
would agree with such a contention.
The validity of the LNT should be tested, but not by such a weak tool as an
ecologic study.
I am sure there are many other areas we do agree on, but the proper use of an
ecologic study is not one of them.
Regards, Bill Field
====================
Dr. Cohen has always clearly stated the conclusion that he believes his analysis of the county data supports and should not be responsible for mis-interpretations or mis-representation of those conclusions.
>From LNT, it follows as the night the day that radiologically-induced cancer incidence (and cancer mortality, given reasonably uniform standards of treatment) is a linear function of person-rem exposure. As such, an ecologic study is adequate to test the LNT, assuming dependence and confounding issues can be handled.
To even suggest that Dr. Cohen might have tried to prove the validity of LNT using his or any other data set misunderstands the nature of the scientific method, at least in the Popperian formulation. Nature whispers yes and shouts NO. An experiment whose results conform to the predictions of a theory does not "prove" validity of the theory. It may gives us a warmer feeling about the theory. Many confirmatory experiments may lead us to believe to a high level of confidence that the theory is true, but they do not "prove" its truth. "Proof" is a concept that lives in Mathematics not in Science.
On the other hand, a theory may make predictions that are falsifiable, in the sense that we can design and perform an experiment whose outcome is capable of contradicting the predictions of the theory. If we were perform the experiment and the results indeed contradict the predictions of the theory, then we need a new theory. To many, including me, Cohen's dataset and his analysis look very much like such an experiment.
Finally, "knowledgeable epidemiologists" believe a number of weird things, case in point being Rothman's assertion a while back that epidemiologists didn't need to bother with the Universal Null Hypothesis in their consideration of whether their data said something meaningful or was simply a reflection of random variation.
Best regards.
Jim Dukelow
Pacific Northwest National Laboratory
Richland, WA
jim.dukelow@pnl.gov
These comments are mine and have not been reviewed and/or approved by my management or by the U.S. Department of Energy.
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