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Re: Radon and Smoking (individual vs aggregate)
The problem is in how scientists handle theories and their tests
of them. No theory takes into account every possible variation in
circumstances. A basic theory takes into account the most important
things, and the other factors are treated as "perturbations" or
corrections to the basic theory. That is how I have managed my study. If
you have a specific criticism of any of my work, I would be happy to
address it; the best way to start is if you criticize something in my
paper on treatment of confounding factors in an ecological study. Much
better still, give a specific example of something that could nullify my
results -- your example need not be true, but it must not be highly
implausible.
On Mon, 18 Feb 2002, Field, R. William wrote:
> Dr. Cohen wrote earlier this morning, "If you don't understand that the
> BEIR Reports use a liinear relationship between lung cancer and radiation
> exposure, there is no point in discussing these matters with you. What do
> you think the LNT debate is all about?"
>
>
>
> Dr. Cohen,
>
> I agree, it makes little sense to continue when we are in disagreement over
> basic facts about BEIR VI. However, rather than conveying my
> interpretation of BEIR VI, let me quote:
>
> "Miner data clearly indicate that the relationship of lung-cancer
> occurrence in a person, to cumulative exposure, is not simply linear, and
> that the joint relationship of radon and smoking is not additive" (Page 376
> BEIR VI).
>
> Relative risks for cumulative radon exposure and lung cancer have
> dependencies on other factors other then smoking and radon. There are
> vectors of covariates that affect background lung cancer rates and other
> vectors that modify the exposure response relationship.
>
> Let's take just one example, if you hope to test the LNT theory using an
> ecologic study, you must know the joint distribution of radon exposure and
> smoking in EACH county (Guthrie's paper I faxed you goes into detail on how
> to possibly get at this information). Nonetheless, you state by using
> "rigorous mathematics" in your 1995 paper you prove you can test the LNT
> theory using an ecologic study. You may have used math, but you needed an
> assumption that all smokers have the same smoking duration and intensity to
> obtain the Cohen derived formula. This faulty assumption invalidates your
> derived equation. This faulty assumption can not be later verified or
> treated by after the fact stratifications using more averaged smoking data
> especially without knowing the joint distribution of the covariates. In
> fact, you have even previously stated, your analysis only, "crudely
> introduces the pack-year concept." Dr. Gilbert has already provided
> evidence that your results are confounded by smoking, because other smoking
> related cancers are also negatively associated with your county radon data
> (Perhaps Jim has a mechanism that shows alpha irradiation to the lung
> decreases the cancer rates in other organs - if so please share it). So
> when you say, the LNT fails, what you are really proving is that the Cohen
> derived LNT formula that used faulty assumptions failed. While I am not a
> loyal LNT supporter, I find myself in agreement with Dr. Piantadosi who
> said in 1994, your findings do, "more to discredit the analysis than the
> theory." I would not expect you to be able to explain your inverse
> findings by using your "treatments" as you call, since the Cohen derived
> formula used to test the LNT suffers from faulty assumptions.
>
> Regards, Bill Field
>
>
>
>
> --------------------------------------------------------------------
>
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