Re: Mechanisms are Needed to Explain Cohen's Data

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

On Thu, 10 Jan 2002, Kai Kaletsch wrote:



> > --See Sec.M of my 1995 paper.

>

> All the models in Sec.M deal with a correlation of radon concentration and

> lung cancer. One should correlate radon progeny exposure or lung dose to

> lung cancer. I proposed a mechanism where the correlation between radon and

> radon progeny as well as radon and lung dose is dependent on smoking status.



	--This reopens the old question of whether we should measure radon

gas or radon progeny in homes. There was a general consensus that it

should be radon gas because factors that influence radon progeny also

influence unattached fraction in a way that compensates, so we should not

neasure radon progeny unless we also measure unattached fraction and that

would be a very difficult and expensive proposition.

	Note that your suggestion would also affect every other study that

has ever been done on radon vs lung cancer, including all the case-control

studies.



> Thank you for the specific citation, it sure beats wading through the

> mountain of literature. The latter part of section D deals with smokers who

> have less radon than non-smokers. What my post pointed out is that

> non-smokers will have their radon systematically lowered by the presence of

> smokers. I'm not sure that is treated in section D.



	--Are you suggesting that a treatment is needed for non-smokers

living in houses where there are smokers? That would be very difficult in

any study. In case-control studies, they don't ask whether there are other

people in the house who smoked.



>

> > > 2.    The second mechanism deals with the influence of smoking on the

> > > Equilibrium factor F.

> >

> > --This is effectively a difference in radon exposure for smokers

> > and non-smokers, which is treated in the reference above, Sec D and Table

> > 4.

>

> So, if we found a systematic mechanism, like the filter, that would cut F

> for smokers to 0.5 of that of non-smokers, the best estimate of your value x

> in table 4 would be 0.9 * 0.5 = 0.45. The lowest value listed in the table

> is 0.8. (Looking at the table, it seems to move B in the wrong direction,

> but I am having a bit of trouble getting my head around it.)



	--I could extend the table if you give me reason to believe that

the effort would be worthwhile.



> >  There are competing factors that affect the

> > > Equilibrium factor in smokers' houses (increased ventilation reduces F,

> > > increased aerosol concentrations increase F, air cleaners reduce F .). I

> > > have no idea which one would be dominant

> >

> > --When considering air cleaners, it is vital to include their

> > effect on unattached fraction. Air cleaners can easily reduce the WLM, but

> > they also increase the unattached fraction and the two effects normally

> > cancel each other fairly closely. That is why air cleaning is not

> > generally regarded as a cheap and easy way to solve the radon problem.

>

> I meant the use of filtration units that is causally related to smoking. I

> think in most cases the combination of smoking and filtration will result in

> a higher number of attachment sites than the combination of not smoking and

> no filtration.



	--This depends on the type of filtration. I have tested filtration

and precipitation instruments that drastically reduce the number of

attachment sites.



> I don't see how one can judge the plausibility of the correlation, if one

> does not consider the underlying mechanism. For example, you deal with

> migration in your papers and conclude that it cannot explain the observed

> radon - lung cancer relationship. Would that conclusion still hold if the

> following mechanism was to be confirmed?:

>

> High radon in the interior of the US causes precursor to lung cancer

> conditions in people . These precursor conditions make the dust, pollen and

> cold air of the interior unbearable and these people move to the coast,

> where radon levels are low. There the precursor conditions develop into lung

> cancer.



	--I think most people would consider this to be very highly

implausible



> I would be glad to write a letter to the Editor saying that these 20 or 30

> mechanisms must be disposed.



	--That would be fine with me but they should be problems that do

not apply to case-control studies. Also, I could not respond to 20-30

mechanisms, so I would much prefer if you could specify a few that are

most important in your list.



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