[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: Cohen's ecologic study reanalyses[Scanned]
Dear Prof Cohen,
I sincerely believe that you cannot just look at percentage change per pCi/L concentration for the slopes. If you look at the absolute numbers, there is a difference (ratio) of almost a factor of five between male and female cancer deaths for each average concentration and this ratio is also reflected in the actual (negative) slopes - therefore you get very similar percentages for the slopes (males and females). Since one must assume very similar exposures for males and females, such a large difference in lung response is highly improbable. Additive effects are effectively ruled out. What weird kind of multiplicative effect would one have to postulate for radon (modification of inherent or induced lung cancer propensity) to describe both curves. A possible (some would say probable) explanation is that radon cannot be a significant factor. A perplexing problem.
Chris Hofmeyr
chofmeyr@nnr.co.za
-----Original Message-----
From: BERNARD L COHEN [mailto:blc+@PITT.EDU]
Sent: 19 September 2003 07:28
To: Gary Howard
Cc: RADHEALTH@LIST.UIOWA.EDU; internet RADSAFE;
RADONPROFESSIONALS@LIST.UIOWA.EDU
Subject: Re: Cohen's ecologic study reanalyses[Scanned]
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.
>
>
************************************************************************
You are currently subscribed to the Radsafe mailing list. To unsubscribe,
send an e-mail to Majordomo@list.vanderbilt.edu Put the text "unsubscribe
radsafe" (no quote marks) in the body of the e-mail, with no subject line.
You can view the Radsafe archives at http://www.vanderbilt.edu/radsafe/
************************************************************************
You are currently subscribed to the Radsafe mailing list. To unsubscribe,
send an e-mail to Majordomo@list.vanderbilt.edu Put the text "unsubscribe
radsafe" (no quote marks) in the body of the e-mail, with no subject line.
You can view the Radsafe archives at http://www.vanderbilt.edu/radsafe/