Case-Control Radon Studies in the U.S.

["R. William Field" <bill-field@uiowa.edu>]

Radsafers, 

The BEIR Comm. did note that ecologic studies have indicated a possible
effect of radon exposure for several types of non-lung cancers.  However,
they did not use ecologic studies to bolster their findings regarding the
association between radon and lung cancer.  The pooled studies they were
talking about were case control occupational miner studies.

Over 20 ecologic studies have been published concerning radon and lung
cancer since 1981.  I was a co-author on an ecologic study a while back
that found an association between radon and lung cancer in Iowa (Health
Physics 66(3):263-269;1994).  (Remember, Iowa has the highest mean radon
concentrations of any state in the nation.)  These ecologic studies are
merely hypothesis generating and have severe inherent limitations.  In the
ecologic study we published, we clearly state the limitations inherent in
that type of study.  Case Control studies are analytical epidemiologic
studies, while ecologic studies are merely hypotheses generating.  

We are currently performing a case-control study in Iowa examining the
relationship between residential radon exposure and lung cancer.  The study
is funded by the National Institutes of Environmental Health Sciences.
The methodology for the study is published in the Journal of Exposure
Analysis and Environmental Epidemiology 6(2) 181-195, 1996.  

There are 2 other case-control studies examining the relationship between
residential radon exposure and lung cancer underway in the United States.
A study in Missouri funded by the National Cancer Institute and a joint
study in Utah/Connecticut funded by the National Institutes of
Environmental Health Sciences. Other case control studies are underway in
Europe (Ardennes-Eifel Study), Germany, Sweden, England and France.  Not
all case-control studies are designed the same way.  For example, some
measure radon in just one area of the home, while other have multiple
measurements per home and link the measurements to the mobility of the
subjects.  The validity of each study design must be evaluated when
determining the credibility of the findings.  Sample size is not always the
most important factor.  A case-control study with 400 cases and controls
with good exposure data may have more power to detect an association (if
one exists) than a study of 3000 controls and cases with poor exposure data.  

The process of pooling all these studies worldwide is already underway.
But, because of differences in the study designs of the case-control
studies, the pooling can not utilize the most complex dose assessments of
some of the studies.  Therefore, some of the individual studies with the
more advanced dose assessments techniques may be more powerful than the
huge pooled study.

If anyone is interested in more information about the Iowa Radon Lung
Cancer Study, please contact me directly.

Regards, Bill Field
Bill-field@uiowa.edu

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R. William Field, Ph.D.
Division of Epidemiology
Department of Preventive Medicine
  and Environmental Health
N222 Oakdale Hall
University of Iowa
Iowa City, Iowa 52242
319-335-4413 (phone)
319-335-4747 (fax)
mailto:bill-field@uiowa.edu
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