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Re: A question of statistical significance vs operational significance
Maury,
With detailed individual level data, you can account for
the noise through multivariate regression. As with most
case control studies, the largest uncertainty in many of
the case-control studies has been obtaining good
retrospective exposure information. In a case-control
study, unlike an ecologic study, the noise (or random
misclassification) generally makes it more difficult to
find an assocaition if one exists. In an ecologic study
such as Dr. Cohen's random misclassification often
drives the assocaition toward either a positive or
negative assocaition. So when people ask to explain his
findings, it is like asking someone to explain
randomness.
See: http://www.cheec.uiowa.edu/misc/rd_review.pdf
The recent paper we published in the Journal of Exposure
Analysis and Environmental Epidemiology demonstrates how
less sophisticated dosimtery methods for case-control
studies reduce the risk estimtess because of problems
with obtaining an accurate retrospective exposure
assessment. Please remember, the 50% increased risk we
noted for the Iowa Radon Lung Cancer Study was for an
average exposure of 4 pCi/L (EPA action level). We
noted higher risks for higher exposures. These findings
were not dependent on LNTT extrapolations.
SEE:
J Expo Anal Environ Epidemiol 2002 May;12(3):197-203
Residential radon exposure and lung cancer: Variation in
risk estimates using alternative exposure scenarios.
Field RW, Smith BJ, Steck DJ, Lynch CF.
Department of Epidemiology, College of Public Health,
University of Iowa, Iowa City, Iowa, USA.
The most direct way to derive risk estimates for
residential radon progeny exposure is through
epidemiologic studies that examine the association
between residential radon exposure and lung cancer.
However, the National Research Council concluded that
the inconsistency among prior residential radon case-
control studies was largely a consequence of errors in
radon dosimetry. This paper examines the impact of
applying various epidemiologic dosimetry models for
radon exposure assessment using a common data set from
the Iowa Radon Lung Cancer Study (IRLCS). The IRLCS
uniquely combined enhanced dosimetric techniques,
individual mobility assessment, and expert histologic
review to examine the relationship between cumulative
radon exposure, smoking, and lung cancer. The a priori
defined IRLCS radon-exposure model produced higher odds
ratios than those methodologies that did not link the
subject's retrospective mobility with multiple,
spatially diverse radon concentrations. In addition, the
smallest measurement errors were noted for the IRLCS
exposure model. Risk estimates based solely on basement
radon measurements generally exhibited the lowest risk
estimates and the greatest measurement error. The
findings indicate that the power of an epidemiologic
study to detect an excess risk from residential radon
exposure is enhanced by linking spatially disparate
radon concentrations with the subject's retrospective
mobility. DOI: 10.1038/sj/jea/7500215
Regards, Bill Field
>
>
> Bill, thanks for taking the trouble to refer me to relevant data. My
> impressions, however, are that you folks are suggesting with an
> epidemiological risk factor of 0.5, that out of an annual total lung
> cancer
> incidence of 157,400 cases, 18,600 or about 12% are attributable to
> radon. I
> don't believe those radon cases could hope to be distinguished from the
> noise
> or error variance. When thinking about the increasing weight of
> evidence
> favoring beneficial health effects from exposure to low level radiation
> (such
> as household radon), I cannot bring myself to get very concerned about
> the EPA
> radon campaign -- except for some of my darker suspicions which already
> have
> been well-fed over the years by the performance of EPA. I just cannot
> view
> radon as a threat and I suspect it might even be beneficial to us.
> Perhaps my
> ignorance, but time will tell after I'm long gone.
>
> Thanks again for your response to me.
> Sincerely,
> Maury maury@webtexas.com
> ================================
> epirad@mchsi.com wrote:
>
> > Maury,
> >
> > Our direct observations
> > http://www.cheec.uiowa.edu/misc/radon.html are in
> > agreement with the BEIR VI
> > (http://www.epa.gov/iaq/radon/beirvi1.html)projections
> > which estimate that approximately 18,600 lung cancer
> > deaths each year in the United States are associated
> > with prolonged radon progeny exposure.
> >
> > Bill Field
> > > Bill,
> > >
> > > Would you select an objective, reliable measure of the impact of
> > > cancer on human health, e.g., mortality, morbidity, longevity, etc. and
> > > tell me what that observation is today in perhaps the US, or the world,
> > > or Iowa, or whatever? Then, if we could suddenly cause all radon and its
> > >
> > > progeny to disappear completely from the earth while all other
> > > conditions remain unchanged, what do you see in any hard data, or
> > > believe would be the observed effect or change in that selected cancer
> > > measurement in, say, 20 years or so?
> > > Cheers,
> > > Maury Siskel maury@webtexas.com
>
> ------------------
> It is the soldier, not the campus organizer, who has given us the
> freedom to demonstrate. Charles M. Province
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