RE: Dr. Lubin's response to Cohen's statements

["Hamrick JS (John)" <hamricjs@ucarb.com>]

I believe I have a small contribution to make in this debate - and that is
that the radon-miner studies most likely are seriously flawed because of
underestimations of radon progeny levels and other factors leading to under
reporting of exposures.  I knew some of the people who went into the mines
to make the measurements, and their (unwritten) charge was to keep the mines
operating.  High radon levels could shut down mines.  (this is a sad
commentary, but one that I believe is true).

For other factors that contributed to under reporting of exposures, Dr.
Douglas Chambers of SENES Consultants in Canada has published several
papers.  One of the conclusions of his work is that the exposures from other
mines were frequently unaccounted for, leading to a lower reported exposure.

John Hamrick
Umetco Minerals Corporation

> ----------
> From: 	FIELDRW@aol.com[SMTP:FIELDRW@aol.com]
> Reply To: 	radsafe@romulus.ehs.uiuc.edu
> Sent: 	Friday, March 03, 2000 8:22 AM
> To: 	Multiple recipients of list
> Subject: 	Dr. Lubin's response to Cohen's statements 
> 
> I feel that I must comment on the exchange by Cohen and Klugh.  Dr.
> Cohen's
> suggestion that because I made no attempt to claim his reward, I must have
> accepted the adequacy of his responses to articles by me and others is 
> fatuous.
> It is not that I don't believe Cohen's results -- below 300 Bq/m3, county
> lung
> cancer rates are negatively correlated with "average" county radon
> concentrations --  but that his results have no relevance regarding risk
> to
> individuals.  They neither support nor contradict current risk estimates.
> 
> Thus,
> continuing the exchange was pointless.  Upon re-reading his responses to
> the
> exchange in Health Physics and on this listserve, I can only conclude that
> Dr.
> Cohen has entirely missed the point of my comments and those of others.
> Let's
> try one more time.
> 
> 1.  It is clear that Cohen's ecological analysis is markedly discrepant
> from 
> the
> analytic studies of residential radon exposure and of radon-exposed
> miners, 
> from animal studies and from current dosimetric/biophysical models.  As I 
> made clear in my last letter in Health Physics, Cohen's linear-quadric
> model 
> for lung
> cancer mortality rates and residential radon is not supported by the
> case-control studies or the miner studies.  His model in fact predicts a 
> strong
> protective effect of living in houses with concentrations under about 300 
> Bq/m3
> - this pattern just does not occur in the analytic data.   
> 
> The relevant question then becomes -- how are we to interpret Cohen's
> results 
> in
> light of the findings from the analytic studies?  More importantly, when
> considering whether and to what extent residential radon increases (or in 
> light
> of Cohen's result, decreases) the risk of lung cancer, is it even
> necessary 
> that
> Cohen's results should be "explained"?  The main point of my articles, as
> well
> as articles by Greenland and Robins, Samet et al, Piantadosi, Muirhead et
> al,
> and others, is that the answer is an emphatic no to the latter question.  
> These
> articles show that the methodology of ecological analysis itself has such
> limitations that no meaningful inference from the relationship observed at
> the
> grouped level can be made to the dose-response relationship for
> individuals.
> Thus, Cohen's regression results cannot serve as an evaluator of radon
> effects
> for individuals.  This is why epidemiologists use ecological analyses only
> for
> hypothesis generating and not hypothesis testing.  In the real world of
> epidemiology, in order to have any credence, an association observed at
> the
> ecological level must first be demonstrated using individual-level
> studies.  
> The
> converse is never the case.  One would never consider that results from 
> analytic
> studies needed to be "validated" by ecological analysis; the very notion
> is
> absurd.  Thus, there is little point in trying to identify any specific
> reason
> why Cohen's regression results in a negative trend, since the analytic 
> evidence
> is so strong.  The methodology itself is intrinsically flawed.  Given
> diverse
> results from ecological analyses and from analytic studies, analytic
> studies a
> priori have the greater claim to validity.
> 
> What is the flaw in ecological studies?  Again, many articles have 
> demonstrated
> that the principal source of the problem is that correlations among risk 
> factors
> can occur within counties.  Moreover, the correlations of those risk
> factors 
> may
> vary among the counties.  Therefore, one cannot simply define a model for
> the
> within county correlations, apply it across counties and claim adjustment
> of
> these effects.  This is the central rationale for the proposal by Sheppard
> and
> Prentice to "correct" ecological studies by randomly sampling populations 
> within
> county in order to estimate the joint distribution of risk factors.
> Cohen's
> repeated assertions that the "ecological fallacy" does not apply to him,
> does
> not make it so.  He cannot create models that account for both the risk
> factor
> correlations within county and their variations across counties.  My
> original
> paper in Health Physics shows that the amount of correlation between radon
> 
> level
> and another risk factor can be small indeed, on the order of 0.05.
> 
> 2.  Cohen suggests that his analysis is not confounded because the
> negative
> trend of lung cancer rates and county "mean" radon level is unchanged
> after
> adjusting for hundreds of different factors.  That is not the point at
> all, 
> and
> indeed is irrelevant to the control of within county confounding.  One can
> 
> never
> adjust for factors that operate within county by endlessly adding more and
> 
> more
> county-level information.  His ecological analysis has no more claim to 
> validity
> if he were to add thousands of additional county-level variables.  
> County-level
> factors are not the source of the limitations.
> 
> 3.  While the within county confounding issue is really paramount, it is
> also
> the case that data used in many ecological analyses are often of limited 
> quality
> and difficult to interpret.  Cohen's data are no exception.  Lung cancer
> mortality from death certificates are often misspecified and covariate
> information is of poor quality.  Of particular concern, Cohen uses
> mortality
> rates where the disease-relevant exposure period is at least a decade or
> more
> prior to available radon data.  The county "average" radon concentration
> may
> bear little relationship to the "average" county radon concentration 
> prevailing
> up to 30 years and more prior to the mortality data.  The population
> composition, and risk factors, as well as lung cancer mortality rates,
> have
> changed considerably in recent decades.  (See for example the NCI cancer
> atlas
> for changes in lung cancer mortality, ).  This problem is exacerbated by
> the
> further limitation that average radon level (and other risk factors) for a
> county does not translate into lung cancer-relevant dose, and that the
> correlations among risk factors may vary over time.
> 
> Residential radon studies in general do not suffer from the flaw that
> radon
> measurements post­date the disease occurrence by 10-30 years.  While radon
> measurements are contemporary, in residential studies, interviews provide
> detailed information on residential history, so investigators know
> precisely 
> how
> long subjects were resident in the various houses, and on house
> modifications,
> heating systems, etc.  In the Iowa study, enrollment in the study required
> 
> that
> the subject has lived in the current house for at least the preceding 20 
> years.
> 
> 4.  It must also be pointed out that not all ecological studies agree with
> Cohen's results, and big does not equate with valid.  Many ecological
> studies
> have been published; some show decreasing trend, no trend, or increasing 
> trend.
> In an attempt to circumvent the limitation of mortality data and poor
> exposure
> data, several investigators have used population registry files to create
> lung
> cancer incidence rates for counties.  Analyzing these incidence rates
> together
> with county radon measurements and other information from population-based
> case-control studies, investigators have found patterns of associations
> that
> show increasing risks with radon.  None show decreasing risks.
> 
> This exchange has been going on for nearly a decade.  To paraphrase 
> Piantadosi,
> given results from analytic studies and ecological studies, the former
> must
> carry the greater weight in our considerations.  Thus, the suggestion that
> Cohen's results must be "explained" is misplaced -- the results are 
> irrelevant.
> It is time to move on and address the many important questions that
> remain: 
> what
> are the consequences of exposure measurement error on risk estimates; what
> is 
> a
> realistic level of uncertainty on the risk associated with long-term
> residence
> in houses in the range of 75-200 Bq/m3; are there specific genetic 
> polymorphisms
> that define susceptible sub-populations?
> 
> Jay Lubin 
> 
> Jay Lubin, PhD
> National Cancer Institute
> Biostatistics Branch, EPS/8042
> 6120 Executive Blvd
> Bethesda, MD 20892-7244
> Tel: 301-496-3357
> Fax: 301-402-0081
> Email: lubinj@exchange.nih.gov
> ************************************************************************
> The RADSAFE Frequently Asked Questions list, archives and subscription
> information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
> 
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html