Odp: Iowa radon vs lung cancer study - response to Cohen

["Jan Skowronek" <brxjs@gig.katowice.pl>]

In my opinion your discussion is interesting for radsafers. Please use this
forum to exchange yours opinions too.

Jan Skowronek
Central Mining Institute
Laboratory of Radiometry
plac Gwarków 1
PL40-166 Katowice, Poland
tel:+48-32-2592382
fax:+48-32-2596533
e-mail: brxjs@gig.katowice.pl


-----Wiadomość oryginalna-----
Od: EPIRAD@aol.com <EPIRAD@aol.com>
Do: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Data: 27 czerwca 2000 06:27
Temat: Iowa radon vs lung cancer study - response to Cohen


>
>Radsafers,
>
>With hesitation, I am writing a limited response to Dr. Cohen's recent
>posting concerning the Iowa Radon Lung Cancer Study.  I have been answering
>Dr. Cohen's questions about the Iowa Radon Lung Cancer Study via direct
>email.  I would have preferred to continue the direct email approach to
>scientific dialogue.  Obviously, I do not feel the listserv is a scientific
>forum and scientific correspondences are better left to
letters-to-the-editor
>or direct correspondence.  I therefore urge Dr. Cohen to either write a
>letter-to-the-editor of the AJE if he thinks his comments have any
scientific
>merit or continue his direct dialogue with me.  At the risk of setting off
a
>cascade of emails, I will respond briefly to Dr. Cohen's comments.  These
are
>my views and may or may not represent the views of all the authors of the
>Iowa Radon Lung Cancer Study.  Any formal journal responses will represent
>the views of the authors.  That is why I would have preferred addressing
>these issues (along with the other authors) in detail in a scientific
arena.
>However, I felt Dr. Cohen's public criticisms on the listserv compelled me
to
>respond on the listserv.  In the end, Dr. Cohen and I will likely have to
>agree to disagree on many of these points as we have so many times before.
>
>It is of note that the Iowa Radon Lung Cancer Study has published numerous
>exposure related method's papers including:
>
>Field RW. Steck DJ. Lynch CF. Brus CP. Neuberger JS. Kross BC. Residential
>radon-222 exposure and lung cancer: exposure assessment methodology.
Journal
>of Exposure Analysis & Environmental Epidemiology. 6(2):181-95, 1996
Apr-Jun.
>
>Fisher EL. Field RW. Smith BJ. Lynch CF. Steck DJ. Neuberger JS. Spatial
>variation of residential radon concentrations: the Iowa Radon Lung Cancer
>Study. Health Physics. 75(5):506-13, 1998 Nov.
>
>Field RW. Smith BJ. Brus CP. Lynch CF. Neuberger JS. Steck DJ.
Retrospective
>temporal and spatial mobility of adult Iowa women. Risk Analysis.
>18(5):575-84, 1998 Oct.
>
>Steck DJ. Field RW. Lynch CF. Exposure to atmospheric radon. Environmental
>Health Perspectives. 107(2):123-7, 1999 Feb.
>
>None of these methodologic papers received any criticisms on Radsafe.  Nor,
>were letters written to the editor of the journal, where they were
published,
>criticizing the methodology.  The first criticisms of our methodology, by
Mr.
>Fumento and Dr. Cohen, arose only after we published our study findings.
>Responses to Mr. Fumento's criticisms and ad hominem attack are detailed
>elsewhere: http://www.cheec.uiowa.edu/misc/radon.html .     Short responses
>to Dr. Cohen's comments follow:
>
>----------------------------------------
>Dr. Cohen states, "The principal reason why the Iowa study is claimed to be
>better than previous studies is that they did a more elaborate job of
>estimating radon exposure doses, by considering exposures outside the home
>and time spent in various places inside and outside the home.  I view these
>improvements as relatively unimportant because of the other much larger
>uncertainties in radon exposures".
>
>
>Field:  The importance of accounting for mobility is obvious by examining
the
>impact on risk estimates if the mobility is not accounted for (see Figure
in
>AJE paper).  Health Physicists know the importance of both concentration
and
>time in exposure assessment.  If you do not account for where the time is
>spent, you are left with assessing risk based solely on concentration as
>previous residential radon studies have done.  Dr. Cohen may view these
>improvements as relatively unimportant, but he has no data to support such
a
>claim.
>
>The other reason the Iowa Study obtained better exposure estimates is
>completely ignored by Cohen.  Previous residential studies that did not
have
>the minimum residency requirement of 20 years had to impute a sizable
portion
>of missing data for the previous 20 years prior to lung cancer or prior to
>enrollment.  This decreased the power of previous residential radon
studies.
>The importance of the minimum 20-year residency is detailed in the AJE
paper.
>
>
>---------------------------------------------------------------------------
---
>--------------
>Dr. Cohen states, "For one example, they consider only exposures 5-19 years
>prior to cancer diagnosis, neglecting earlier exposures; among the Japanese
>A-bomb survivors, the majority of lung cancer deaths occurred more than 20
>years after exposure, and according to the BEIR-VI models, the same should
be
>true of lung cancers induced by radon."
>
>Field: I would suggest that Dr. Cohen review BEIR IV to look at the
temporal
>weighting factors derived from miners.  The Iowa Study was the only
>residential radon study, other than the study performed in Finland, which
did
>not have to impute missing radon data for the prior 20 years.  In fact, a
>large proportion of Iowa Subjects lived in the study home for periods
>exceeding 30 years.  See AJE paper for details.
>
>---------------------------------------------------------------------------
---
>--------------
>Dr. Cohen states: "Moreover, the procedures they use to take into
>consideration the time spent in various places introduces a whole new set
of
>uncertainties derived from problems in remembering and reporting habits
from
>5-19 years earlier."
>
>Field: The retrospective dose assessment methodology was very detailed.
The
>assessment methodology was reviewed by at least two reviewers for the
>American Journal of Epidemiology and several reviewers from the Journal,
Risk
>Analysis.  The methodology describing the retrospective mobility assessment
>is available for review in the journal.  The stable time periods in the
>subjects' life were anchored by life events.  For example, women know when
>they were married, when they were working, when they had children, etc.
>These life events were used to frame the time periods.  Please see the
paper
>describing this methodology for more details.  Nonetheless, greater
>uncertainty in retrospective mobility is attributable by assuming a
constant
>home occupancy such as 75%.
>
>For more details:
>
>Field RW. Smith BJ. Brus CP. Lynch CF. Neuberger JS. Steck DJ.
Retrospective
>temporal and spatial mobility of adult Iowa women. Risk Analysis.
>18(5):575-84, 1998 Oct.
>
>---------------------------------------------------------------------------
---
>--------------
>Dr. Cohen states, "Are these memories unbiased by more recent times when
the
>cases
> were sickly while the controls were healthy?"
>
>Field: The memories are anchored by life events.  There is greater bias by
>assuming cases and controls both spent 75% time in their home.
>---------------------------------------------------------------------------
---
>--------------
>Dr. Cohen states: "Does the interviewer treat cases and controls without
>being biased by the fact that the former are sick and dying while the
latter
>are healthy?"
>
>Field: The interviewer was blinded to case/control status.  However, in
some
>instances, it was obvious the case was sick.  However, there were also
>controls that appeared ill.  What biases does Dr. Cohen feel may be
>introduced?  Remember, the major questionnaires were mailed to the
>participants and filled out by the participants prior to the on-site visit.
>---------------------------------------------------------------------------
---
>--------------
>Dr. Cohen states, "There are also uncertainties in that radon levels in a
>particular house may have changed over time. For example, a crack may have
>developed (or conversely, have become sealed) in the basement floor,
causing
>the radon level to be different 15 years ago than it was in the recent
>measurement. Similar problems can arise from
>changes in ventilation; do window opening habits and use of air
>conditioning remain unchanged over 20 years, let alone between hot and
>cool Summers?"
>
>Field:  This is more of a problem for studies that go back and assess the
>radon concentrations in previous homes.  Obviously, the new owners may have
>different behaviors as far as opening windows etc. than did the subject.
>Also, when someone new moves into a home, they are more apt to make
>structural changes than people who have lived in their homes for over 20
>years.  Also, remember - the most important predictive factor for radon in
>the home is source strength - source strength remains stable over time.
>
>We excluded cases and controls that mitigated their home for radon.  We
also
>looked at changes that may have affected radon concentrations over time.
The
>major changes that occurred that may have affected the radon concentrations
>was the switch over in the 1960s and early 70's to central and window air
>conditioning.  The window opening behavior of the subjects was stable over
>the years.  We did note a higher degree of difference in repeated year
>measurements for the homes after the subject had passed away.  The COV for
>repeated second year measurements is reported in the AJE paper.
>
>We also placed glass-based retrospective radon detectors at each study
home.
>These will provide additional data to assess the retrospective radon
progeny
>exposure.  These findings were not included within the main Iowa Study
>Findings (gas measurement paper) paper.  For more information on the
>methodology see:
>
>Field RW. Steck DJ. Parkhurst MA. Mahaffey JA. Alavanja MC. Intercomparison
>of retrospective radon detectors. Environmental Health Perspectives.
>107(11):905-10, 1999 Nov.
>
>------------------------------------------------------------
>Dr. Cohen States: "For these reasons, I do not accept the claim that this
>study is far superior to the others. Uncertainties in radon exposures are
>important factors in all of them."
>
>Field:  As reasonable people sometimes have to do, we apparently will have
to
>agree to disagree on this topic.
>
>----------------------------------------------------------
>
>Dr. Cohen States:  "The aspect of this study that bothers me most is that
the
> corrections for time spent in various places makes a very large difference
> in the results, greatly enhancing their conclusion that radon exposure is
> important, in spite of the fact that the average percentage of time spent
> in various places is essentially the same for cases and controls: for
> cases vs controls, average percent of time spent in the home is 73.2 vs
> 72.1, in another building is 14.2 vs 14.4, outside is 7.6 vs 8.5, and away
> is 5.0 vs 5.0. While I can understand that mathematically it is possible
> that  correcting for where each individual spends her time can make a big
> difference from considering onle the averages, it seems very
> difficult to see how the effect can be so systematic as to grossly affect
> the results. It seems to me that the authors owe us some explanation to
> help us understand such a seemingly improbable situation."
>
>Field: As I have pointed out before in my discussions with Dr. Cohen, you
can
>not always look at summary data findings and be able to explain the details
>of the individual data linkages between radon concentrations and
>retrospective mobility.   We were limited in some discussions in the AJE
>paper since we had already slightly exceeded our space limit in the AJE
>paper.  We have almost completed a paper that examines the a priori risk
>assessment model used by the Iowa Study versus alternative scenarios that
did
>not include consideration of where the time was spent by the subject.  The
>paper in the works contains a more detailed discussion than what is
included
>in the AJE paper.
>---------------------------------------------------------------------------
---
>-------------
>
>Dr. Cohen states. "Another problem that bothers me is that there is no
>consideration given to geography, which is a potential confounding factor
>very closely  correlated with radon levels. Controls are chosen randomly
from
>the entire  state of Iowa, where average radon levels in different counties
>varies by  a factor of 3, from 1.7 to 5.0 pCi/L. Cases come largely from
>areas where  there is a high prevalence of smoking, which might easily have
>different  average radon levels than the controls. It seems important to me
>that  information be given at least on what counties the cases and controls
>come from."
>
>Field:  Dr. Cohen, I understand your focus on average county radon
>concentrations given your previous research.   However, the range of radon
>concentrations within a county is much greater than the range between
>counties.  We did not use mean county radon concentrations to assess radon
>exposure, we used individual data for each subject.  In fact, in a
>preliminary analysis we have found that mean county radon concentrations
are
>a poor predictor of both individual radon exposures and home radon
>concentrations in Iowa.
>
>Some studies have suggested that radon concentrations may be lower in urban
>areas.  The prevalence of smoking is higher in urban areas.   In fact, Dr.
>Cohen's ecologic data shows an inverse relationship between smoking
>prevalence (based on tobacco sales tax in a county) and radon
concentrations.
>  If smoking is indeed related to radon concentrations, it would likely
>minimize finding any association between radon exposure and lung cancer.
>
> If some factor that caused lung cancer (confounder) was co-correlated with
>geography, it likely would be associated with urban/rural status.  However,
>urban/rural status was not found to be a significant factor in our
analyses.
>
>------------------------------------------------------------------
>
>Dr. Cohen States:  "The cases are nearly all smokers while the controls are
>nearly all  non-smokers. There are many differences in life styles of
smokers
>and  non-smokers that can affect radon exposures. Some attention should be
> given to these. Also there is a substantial difference in educational
> attainment between cases and controls which could be a source of trouble.
>
>This is one example of socioeconomic variations which can be important
both
>in disease vulnerability and in radon exposures, but essentially no
attention
>is given to socioeconomic factors other than education."
>
>Field:  The inclusion criteria of 20 years in the current home provided a
>match that made the educational status and socioeconomic status between the
>cases and controls much closer than previous residential epidemiologic
>studies.    In addition, the analyses were adjusted for education.  I would
>like to know what data Dr. Cohen is using to demonstrate these other
>unidentified socioeconomic factors were not adjusted for as part of the
>adjustments we made for smoking, education and age.
>
>---------------------------------------------------------------------------
---
>------------
> Dr. Cohen States: "The  basis for a case-control study is that cases and
>controls are matched in  every way except for having contracted the
disease.
>Any deviation from  this would seem to be an issue for concern."
>
>Field:  This is an erroneous statement.  What Dr. Cohen describes here is
>overmatching.
>
>Dr. Cohen says in a case-control study the cases and controls are matched
"in
>every way except for having contracted the disease".  Dr. Cohen, I
>respectfully request a reference for this statement.  For example, if your
>statement was true, we should have matched the cases and controls by radon
>concentration, mobility, shoe size, eye color, favorite ice cream flavor,
>etc.
>---------------------------------------------------------------------------
---
>--------------
>
>Dr. Cohen,
>
>I would be glad to continue the dialogue with you or others to further
>discuss some of these points via direct email to
mailto:bill-field@uiowa.edu.
> As I indicated above, we are still working on several other papers using
>Iowa Radon Lung Cancer Study data including analyses using the glass-based
>retrospective radon progeny detectors.   These papers will provide
additional
>information about the study and furether address some of your questions.
>
>Regards, Bill Field
>
>
>To Radsafers:
>
>I appreciate the kind words many members of the silent majority of Radsafe
>have conveyed to me directly concerning the Iowa Radon Lung Cancer Study.
It
>is nice to know you are out there.  I know some members of the Radsafe
>community will attack this post.  I understand that they want to put their
>spin on things.  I know of no other epidemiologist that would take the time
>to respond to postings on this listserv (Believe me - I wish there were).
>Sometimes, I wonder why I do.  It must be that I worked as a Health
Physicist
>prior to working as an environmental epidemiologist.  I welcome the
dialogue
>and have never been one to shy from scientific discussions.  However, if
you
>are going to criticize the posting, please read the main paper and
referenced
>papers first.  If you have comments about the posting, I humbly request
that
>you email me directly.  As you can understand, I really am limited in the
>amount of time I have for public posting since each public post creates a
>cascade of questions via private emails.
>
>
>Sincerely, Bill Field
>
>
>
>
>R. William Field, Ph.D.
>College of Public Health
>Department of Epidemiology
>Department of Occupational and Environmental 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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