Re: Cohen's ecologic study reanalyses

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

	There was a serious typo in the message below that I sent

yesterday. The correction is shown by ****



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



On Thu, 18 Sep 2003, BERNARD L COHEN wrote:



>

> On Tue, 16 Sep 2003, Gary Howard wrote:

> >

> > What are your thoughts on this recent paper?

> >

> > Health Physics, Volume 85, Issue 4

> >

> > EPIDEMIOLOGICAL ASSOCIATIONS AMONG LUNG CANCER, RADON EXPOSURE AND

> > ELEVATION ABOVE SEA LEVEL—A REASSESSMENT OF COHEN'S COUNTY LEVEL RADON

> > STUDY

> >

> > Wesley R. Van Pelt*

>

> 	--I am preparing a letter to the Editor on this. Part of my first

> draft follows:

>

> The title of Wes Van Pelt's recent paper (Van Pelt 2003) calls it "a

> reassessment of Cohen's county level radon study. The purpose of this

> letter is to show that it is something less than that.

> 	My studies of the relationship between lung cancer rates and

> average radon levels in homes for 1600 U.S. counties (Cohen 1995, 2000a)

> with elaborate treatments of smoking behaviors (Cohen 1995, 1998, 2000b)

> was designed and presented as a test of the linear-no threshold theory

> (LNT) of radiation induced cancer. The key quantity in my analyses is the

> slope, B, of the best fit to the data. In units of percent change in lung

> cancer rate per pCi/L (37 Bq/m3) of radon, LNT predicts B = +7.3, whereas

> fitting the data gives B = -7.3 (0.6) for males and B = -8.3 (0.8) for

> females, discrepant with the LNT prediction by mopre than 20 standard

> deviations.

> 	My studies include elaborate treatments of potential confounding

> factors (CF) that might explain these discrepancies. I introduced a method

> of stratification for obtaining a value of B free of confounding by a

> given CF and showed that combinations of CF are not much more effective

> than the single most important CF in affecting the results, including a

> recent advanced treatment (Cohen 2004).

> 	Van Pelt has now discovered a new CF, altitude (elevation above

> sea level) which can do more to make the value of B less negative than any

> of the hundreds of CF previously considered. In particular, by use of

> stratification on altitude, he finds B = -3.3 for males and B = -4.3 for

> females. Moreover, he offers a mechanism involving changes in oxygen

> concentration that can explain the behavior he hypothesizes.

> 	While Van Pelt's observation is certainly interesting, it does

> little to affect the conclusions of my papers. In the first place, his

> results can reduce the discrepancy in B-values with the LNT prediction, B

> = +7.3, by only 27% for males (from [7.3 +7.3] to [7.3 + 3.3]) and by only

> 26% for females (from [7.3 + 8.3] to [7.3 + 4.3], which is still a long

> way from resolving the discrepancy.

> 	In the second place, the stratification method provides only an

> upper limit on how important a CF may be. For example, since radon levels

> are strongly correlated with *****altitude****, two alternative views are

> suggested:

> A.	The negative correlation between lung cancer and radon might be

> partially caused by a negative correlation between lung cancer and

> altitude, as Van Pelt proposes; or

> B.	 The negative correlation between lung cancer and altitude might

> be explained by the negative correlation between lung cancer and radon, in

> which case altitude is not an effective CF.

> I see no reason to prefer alternative A over alternative B.

>

>

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