Re: Radon and Lung Cancer: What the studies really say.

[BERNARD L COHEN <blc+@PITT.EDU>]

On Fri, 20 Jun 2003 epirad@mchsi.com wrote:



>    We repeated the

> regression of lung cancer mortality rates on these adjusted smoking

> percentages.  The resulting R2 values indicate that S explains only 23.7% of

> the variation in lung cancer mortality rates among females and 34.5% among

> males.



	--The problem here is that you do not understand the meaning of

R-squared. It's affected by all the small random fluctuations in smoking

and lung cancer rates; this was explained in my paper in Health Physics

72:489-490;1997. A much more meaningful test of the ability of our smoking

prevalences, S, to explain lung cancer rates is to do the same regression

you do, fitting the data to

		m = P + Q S

where P and Q are fitting parameters, and observe the standard deviations

in the two terms. From Table 2 in Item #15 on my web site (the factor 100

in Column 3 should be deleted)

	P = -9.7 +/-2.1     and   Q S(average) = 60 +/- 4

Thus the second (smoking)term is completely dominant, with negligible

uncertainty. (The minus sign for the first term would suggest that with no

smoking, there would be negative lung cancers)



	--One of the three methods I use for determining S-values is to

derive them from the lung cancer data for counties of similar radon

levels. Surely you can't claim that these do not explain the lung cancer

vs smoking relationship, as they are derived from it. Using those S-values

gives only a slightly higher R-squared, 41% vs 35%, and

performs well in the above test

	P = -10 +/-2        and   Q S(average) = 66 +/- 2

It gives very similar results to those obtained from my principal set of

S-values, that is essentially the same discrepancy with LNT



> 	The poor predictive power of S is due, in part, to a failure to allow

> for the effects of smoking intensity and duration.

>  Cohen’s failure to

> incorporate intensity and duration in his analysis naturally leads to a smoking

> variable which accounts for fewer lung cancer deaths.



	My not using smoking intensity in my original work was due to the

fact that I was using the BEIR-IV theory which does not include intensity

of smoking. Two of my three methods for deriving S-values do incorporate

implicit weighting for intensity of smoking -- deriving S-values from lung

cancer rates, and from cigarette sales tax.

	However I do give an elaborate treatment of intensity of smoking

in Health Physics 78:522-527;2000, summarized in Sec. 4.4 of Item #7 on my

web site. It shows that this can do little to resolve the discrepancy with

LNT.



> Puskin's finding further supports that you smoking rates do a poor job of

> predicting lung cancers in counties since your inverse assocaition was found

> for other smoking related cancers which are not related to radon exposure.



	--This is thoroughly refuted in Item #15 on my web site. Can you

say how you find that it is not conclusive.



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