Re: If you do Science, use the Scientific Method!

[Peter.Thomas@health.gov.au]

I probably shouldn't be doing this but ...



Fritz Seiler wrote ...





[snip]



 The discussion on RADSAFE, on the other hand, is an endless series of

variations on the Radon/Lung cancer theme.  I must say that I am slowly

getting tired of a scientifically totally aimless technical debate about

epidemiology in the presence of confounders etc.  I have now several times

asked the people involved to state clearly just what they are really doing

in a scientific sense.



  So here I go again, and to make it easier I propose

the following alternatives 1) The aim is to determine the risk of lung

cancer for Americans that are exposed to various levels of Radon and its

daughters, taking into account that a third of these people smoke at 

various

levels; or 2) The aim is to determine the purely academic risk coefficient

for lung cancer due to an exposure to Radon and its daughters alone.  I do

not believe that all of the members of the discussions have stated clearly

what the scientific goal of their study is.



[snip]

I think that nearly everybody (and especially Bernie Cohen) would agree 

that

Cohen's ecological study is NOT about determining the risk of lung cancer

due to radon.  It is a simple fact that the risk to an individual cannot 

be

determined in such a study.



What I understand Bernie to be saying he is doing in the study is to test 

the

Linear No-Threshold (LNT) hypothesis by assuming its truth (which allows

the use of aggregate data by virtue of its linearity) and then 

demonstrating

that this doesn't reflect reality.



Lubin, Field and others (in my understanding) maintain that Cohen's result

is the product of "cross-level bias" (I admit I don't really understand 

what

that is, I am not trained in epidemiology and have only been trying to

make sense of the debate as a part-time out-of-hours exercise in the 

recent

past) and confounding factors.



Bernie appears to me to maintain that he performs extensive analysis

of confounding and that he can find no plausible confounding to explain

his result.  My reading of Lubin's paper (J. Radiol. Prot. 22, 141 2002)

is that he thinks only a very weak correlation between smoking and

radon (as one example) is required to explain the result.  Hence the

endless arguement over confounding etc.



Finally, Field and others maintain that among the better ways to determine

the risk of lung cancer due to low radon levels for individuals is via a 

case-control

study and the results of such studies (on the whole) show a positive (i.e.

cancer causing) effect that is broadly consistent with a downward

extrapolation of studies of miners exposed to high radon levels (albeit

with error bars that include no effect).



My A$0.02 (which rounds up to A$0.05 unless transacted electronically)



Peter Thomas

Medical Physics Section

ARPANSA



The ideas expressed above are my own and do not necessarily reflect

those of ARPANSA etc.



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