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-value 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.