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Bill,
Two different issues are getting mixed up here:
1. Is any reasonable LNT model consistent with the county
radon vs lung cancer data?
2. Has Cohen shown the BIER formula to be wrong, beyond
any reasonable doubt?
The first question does not depend on your understanding of BIER or Cohen's
arguments. It is simply a challenge to take a reasonable risk formula (linear in
with radon) and a reasonable intra or inter - county distribution of values and
make it reproduce the observed data. The data is the data. It is not dependent
on Cohen's assumptions. Some of it was not even collected by him. Nobody is
expecting that you "identify empirical sources of ecologic
bias from aggregate (ecologic) data" but simply to
postulate theses sources, plug them into a spreadsheet, and reproduce the graph.
The second question depends on the nuances of the BIER
formula. If BIER allows a risk formula which is dependent on smoking intensity
to the fifth power, then we need to explore the possibility that the variation
in smoking rate within a county is inversely related to the average radon
concentration of the county.
My comments and questions (and I think most of the
others' comments) deal exclusively with the first question, but the responses
only address the second question. If there is a smoking intensity and duration
model that can explain the county radon vs lung cancer data, then let's see the
model first. Once we are sure that the model COULD explain the data, then
someone should use Guthrie's or other methods to check that the model DOES
explain the data.
Best Regards,
Kai
----- Original Message -----
Sent: Thursday, February 21, 2002 2:18
PM
Subject: Testing the validity of the
LNT
Otto and Bill,
I think what your asking is
that someone explain why a specific relationship was found using a formula
that is not the LNT formula. What type of relationship should be found
using the Cohen derived formula, if his formula is not an LNT formula?
The point I made a couple days ago is that you can only hope to test the LNT
if you factor in smoking duration and intensity in the initial formula since
that is the only way the dose (concentration in this case) - response has a
chance of being linear, if you do not do that you are not testing a LNT
formula.
I have no idea what results Cohen's derived "LNT" formula
should produce. I think what he is seeing is correct for his
formula.
A quote from our previous letter, "Cohen (1999a)
continues to challenge scientists to suggest a plausible explanation to
explain the inverse relationship he notes between mean county residential
radon measurements and mean county lung cancer mortality rates. We will call
this inverse relationship "Cohen's Paradox." Cohen (1999a) states that his
challenge is for someone to suggest a "not implausible model" as a possible
explanation and that the burden of proof will be on him to show that "the
explanation is highly implausible." We maintain that even if additional
plausible models are offered, Cohen will likely not be able to explain his own
paradox. Cohen has not accepted the fact
that it may be impossible to explain Cohen's Paradox in definitive analytical
terms with his existing data because it is not always possible to identify
empirical sources of ecologic bias from aggregate (ecologic) data alone (Field
et al. 1998a)." Ref: http://www.lww.com/health_physics/0017-90789-99ltrs.html
Let's first start with a valid formula that
factors in smoking duration and intensity. As I have suggested perhaps
this information can be obtained using the methods in Gutrie's paper. I
favor thinking about ways to improve the validity of his formula and available
data he has for his analysis rather than trying to explain the fruits of an
unsupportable formula.
Regards, Bill
Field
Information on the Burlington Health Study:
http://www.public-health.uiowa.edu/baecps/
******************************
R.
William Field, Ph.D.
College of Public Health
Research Scientist -
Department of Epidemiology
Adjunct Professor - Department of Occupational
and Environmental Health
Graduate Faculty - College of Public
Health
N222 Oakdale Hall
University of Iowa
Iowa City, Iowa
52242
319-335-4413 (phone)
319-335-4748 (fax)
mailto:bill-field@uiowa.edu
******************************
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