Mossman's letter

[BERNARD, L, COHEN]

	The July issue of Health Physics News includes my letter to the

Editor in response to Mossman's Editorial in the June issue which was

posted previously on RADSAFE. It also includes a letter from Mossman

responding to my letter.

	I was told that it is against Editorial rules for me to publish a

response to this last Mossman letter. I therefore give my response below,

referring to the numbering he uses in his letter.



Bernard L. Cohen

Physics Dept.

University of Pittsburgh

Pittsburgh, PA 15260

Tel: (412)624-9245

Fax: (412)624-9163

e-mail: blc@pitt.edu

web site: http://www.phyast.pitt.edu/~blc



Response to Mossman's "Response to Cohen's Letter" in

Health Physics News, July 2003, page 10



1a. "Cohen does not refute Puskin's conclusions"

	----Puskin's conclusion is that my results and his observation are

explained as due to errors in my values of smoking prevalence, S, for each

county; he concludes that my S-values miss a strong negative correlation

between S and radon levels, r. I show that even an infinitely strong (I

called it "perfect") negative correlation does not improve on the paradox

posed by Puskin's observation, and does not explain the huge discrepancy

between my results and the predictions of linear-no threshold theory

(LNT). Why does that not refute Puskin's conclusion?



1b. "Cohen admits he cannot explain Puskin's observation"

	---As I show in 1a above, Puskin's explanation fails. My suggested

explanation is offered in the fourth paragraph of my letter.



2. "Lack of evidence that radon causes cancer in tissues other than lung"

	---I don't know that anyone has looked for such evidence. But, in

any case, I did not claim that radon causes these cancers. I only suggest

that processes by which low level radiation may reduce the risk of lung

cancer may also apply to those cancers. I give examples of such processes.



3a. "inappropriate to interpret Cohen's data to mean that radon reduces

lung cancer"

	---I have never claimed that my data mean that radon reduces lung

cancer; that would be an application of "the ecological fallacy". If LNT

fails, I can't logically interpret my data in quantitative terms. If LNT

is assumed to be correct, its predictions are grossly discrepant with my

data. Putting these two things together, I conclude that LNT fails.



3b. "why does Cohen talk about protective mechanisms"

	---They are a not unreasonable way to explain the data. I cannot

prove that they are the explanation, although Puskin's observation pushes

me toward that idea. All I claim to have proven is that LNT fails.



3c. "Krewski  concludes that none of the analyzed studies reported a

statistically significant negative association"

	---That is very different than saying that they show strong

evidence against a negative association. That is what would be required to

justify Mossman's original statement  "Cohen  and the case-control studies

cannot both be right" (if, as Mossman incorrectly assumes, my data is

interpreted to represent a dose-response relationship).



4. "reward to anyone who could explain Cohen's negative correlation"

	---My reward was for a plausible explanation for the discrepancy

of my data with the strong positive correlation (more accurately "slope"

of lung cancer vs radon) predicted by LNT. That is very different from

reducing the negative slope. In any case, I do not consider an infinitely

strong (perfect) correlation between smoking and radon to be "plausible".

The fact that this perfect negative correlation would eliminate the

negative slope was shown in my 1995 paper in Health Physics. Plausibility

considerations are discussed there, and much more in item #7 on my web

site.





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