Re: Mechanisms are Needed to Explain Cohen's Data

[Kai Kaletsch <info@eic.nu>]

----- Original Message -----

From: "Ted Rockwell" <tedrock@cpcug.org>

To: "Kai Kaletsch" <info@eic.nu>; "RadSafe" <radsafe@list.vanderbilt.edu>

Sent: Wednesday, January 09, 2002 10:35 AM

Subject: RE: Mechanisms are Needed to Explain Cohen's Data





> > The point is that the mechanism is all-important.

>

> Of course, it's always nice to really understand the mechanism.  But the

> whole practice of medicine involves having little understanding of

> mechanisms, but having to go on and make decisions anyway.

>

> Cohen is not working with a computer model which he then has to try to fit

> to a larger population.  He measured the population itself, albeit with

> averages.  His is a picture of what happens to real people in their homes.

> Other data is valid to the extent it agrees with the real picture he

> measured.  It does not depend on understanding the mechanisms.

>

> TR



Nobody is arguing about the "picture": Counties in the US with high radon

levels in the living areas of houses have lower lung cancer mortality than

counties with low levels of radon.



Based on this "picture", an insurance company would be justified to offer

lower premiums to people living in counties (not houses) with high radon

levels. However, taking pictures is photography. Science deals with

explaining the pictures.



Dr. Cohen has tested various mechanisms and rejected them and has offered

the breakdown of LNT as the most likely mechanism. To me, the breakdown of

LNT is not an unlikely scenario. I am not aware of a single data point that

supports LNT at the low levels of Dr. Cohen's studies. Furthermore, the

cellular mechanism of cancer induction, which was first used to justify LNT,

is now known to be not valid.



Over the last 10 years or so, I do not recall a single person saying that

they believed that LNT was the absolute truth. What people are saying are

things like: "LNT has not been conclusively proven to be incorrect.",

"Better safe than sorry.", "LNT is a good operational model.",.



Some reluctance to throw out LNT is understandable. After all, you don't

want to change the regulatory regime every time a new data point comes

along. This has nothing to do with science, but is a result of the fact

that, in radiation protection, practical issues ($$$) are linked to the

science. This problem is not helped at all by the fact that most people

publishing papers in the field of health physics feel compelled to make some

sort statement indicating that dose limits should be raised or lowered

because for their findings or that we should build more or fewer nuclear

power plants.



To overcome this reluctance, alternative mechanisms should be proposed to

explain Dr. Cohen's data and they should be systematically tested (and

eliminated?).



The other thing that should be pointed out is that the generic truisms about

ecological studies, that are often given w.r.t. Dr. Cohen's data, may or may

not be relevant to his test of LNT. However, they offer no explanation of

the data. The ecological fallacy comes into play when one tries to use

county data to make conclusions about individuals. It is irrelevant to

explaining the original county data. Specific mechanisms are needed.



Kai Kaletsch

http://www.eic.nu





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