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9
Summary of Responses to CDC's Questions
CDC asked the National Research Council
subcommittee the following six questions regarding the HTDS, the
Draft Final Report and related materials and events:
. Has the analysis been earned out appropriately and
completely?
. Are the presentation and the discussion of results
complete?
.
Are the conclusions reasonable?
· Was the material accurate and appropriate in providing
guidance to the public in understanding the study findings?
. If these messages about findings need to be amended,
how should the revised messages best be communicated to the
public?
. With regard to release of future study reports, how can
CDC improve the public communication process?
This chapter presents the subcomittee's answers to
those specific questions.
137
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Review of the HTDS Draft Final Report
HAS THE ANALYSIS BEEN CARRIED OUT APPROPRIATELY AND
COMPLETELY?
The quality of the data used in the analysis is as
important as the analysis itself. Our overall assessment is that the
epidemiologic design was of excellent quality. The sample was
based on an almost complete census of eligible subjects born in the
selected years and geographic regions. Efforts to solicit study
participation were thorough and appeared comparable for those
with high and low doses; as a result, they achieved similar
participation rates across the dose range. The HTDS was
successful in obtaining subjects willing to participate, and it
essentially met its goals with regard to sample size and thyroid-
dose distribution.
Care was taken to maintain blinding wherever possible
In the study to minimize the potential for selection bias,
interviewer-induced response bias, and clinical-examination bias.
The clinical examinations and laboratory studies were performed
with modern methods of detecting and defining thyroid disease,
although more quality-assurance procedures with regard to the
cytopathology data would have been desirable. In short, the
epidemiology and clinical parts of the HTDS were designed and
conducted with great care. The study appears to compare
extremely well with other epidemiologic studies in those respects.
The subcommittee believes that the methodology used
by the HEDR project to estimate thyroid doses and their
uncertainties is structurally sound. The HEDR models have been
subjected to numerous reviews, and the various codes have been
tested by the HEDR project staff independently of the developers
to ensure correct implementation. The dose assessment has been
found, on the whole, to be reasonably sound for the estimation of
thyroid doses for representative, hypothetical individuals.
However, errors have been found, and doubts have been raised
about the validity of the results for particular environmental
conditions and for the estimation of thyroid doses for specific
individuals.
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Summary of Responses to CDC's Questions
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Although there are some fairly minor errors in the
mode! calculations (use of sagebrush measurements to estimate
pasture grass concentrations, use of wet rather than dry grass
weights, and possible failure to consider wet deposition on pasture
grass), the dose estimates for the period 1944-1947, the period of
greatest exposure, appear reasonable. There might have been some
underestimation of doses for later years, as pointed out by
Hermann and Hermann (1996) and Hoffman and others (1999~.
However, those possible errors would have relatively modest
impact because the later doses were much smaller than those in
1944-1947 and the study children were older in the later period;
other studies have shown that the thyroid is much more sensitive to
cancer induction in early childhood than in later childhood and
adolescence.
There is reason to believe that the dose uncertainties
that the HEDR project estimated and that the HTDS study used are
underestimates of the total uncertainty. Some sources of
uncertainty in the 13~] pathway to humans probably were not
included, such as cow-feeding practices and commercial milk-
distnbution patterns. But, owing to the scattered nature of the
information on uncertainties, as opposed to its being summarized
in one source, the subcommittee could not be sure about the
uncertainties. In addition, uncertainties in the residential histories,
lifestyle, and, especially, milk-drinking habits of the children were
not accounted for.
One major component
of the determination of
individual 13~{ exposures was the milk-drinking habits of the study
subjects. Although an attempt was made to interview a parent or
surrogate to obtain recollections of the milk consumption of each
subject in childhood, it was possible to do so for only 62% of the
subjects; in the other cases, default assumptions were used in
calculating thyroid dose. The defaults that the CIDER mode} used
proved to be considerable overestimates of the average doses
derived from the reported milk consumption and source in the
interviews. The potential impact of the discrepancy between
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Review of the HTDS Draft Final Report
reported and imputed milk consumption on the dose-response
analyses needs to be evaluated further.
The basic objective of the statistical analysis was to
determine whether there was a cause-effect relationship between
the occurrence of various thyroid diseases and the magnitude of
exposure to 13~{ released from Hanford in the period in question.
That was appropriately addressed by modeling the relationship
between dose and the probability of occurrence of a thyroid
disease. The HTDS also considered a reasonable set of potential
confounding variables for thyroid disease.
However, there was overreliance on the maximum-
likelihood fitting of the linear dose-response model; for several of
the important outcome variables (such as thyroid carcinoma), the
mode] failed to converge. When the linear model as described
failed to converge, an analysis could have been conducted with
four or five dose groups and the average value of dose in each
category could have been used as the predictor variable. That
would probably have resulted in successful convergence of the
mode! and retained reasonable power to detect an effect.
Dose-response analyses with stratification on geostrata
are needed because the HTDS tabulations showed that rates of
several types of thyroid disease tended to be higher in areas with
low fallout. That means that the geostratum differences would
induce a negative association between I'll and thyroid-disease
rates and might have masked a positive association between
thyroid dose and disease.
The HTDS investigators took care to examine the
results for study participants who proved never to have been in the
dosimetry area during the time of ]3~] exposure (the out-of-area
participants). They performed sensitivity analyses to determine the
impact of possible dose misestimation for those subjects and found
it to be small. However, the HTDS investigators made no attempt
to mode! the out-of-area doses for persons who were included in
the main analyses. That is, if a person was in the dose-assessment
area for only part of the time when there were IT releases, they
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Summary of Responses to CDC's Questions
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calculated his or her dose only for the time that he or she was in
the dosimetry area. They implicitly assumed that the dose was zero
for any time when the person did not reside in the area. No attempt
was made to conduct a sensitivity analysis to evaluate how that
assumption could have affected the results. Their approach to this
issue could have led to attenuated or biased results in that it
potentially estimated total fallout doses for some people but only
partial doses for others.
The HTDS investigators performed an adjusted
comparison of the number of thyroid cancers found in the study
versus the number that would be expected in the general US
population (without radiation exposure) and found no difference.
But there was a great deal of uncertainty in the comparison
because the degree to which thyroid screening alters the number of
thyroid cancers found is not well known. The subcommittee
believes that the HTDS emphasis on analyses of subjects in the
study rather than on comparisons with the general population is
appropriate.
There are sizable
uncertainties in the doses
reconstructed for individuals because of residential and, especially,
dietary histories and because of the imprecision related to the
source term, meteorologic conditions, pasture deposition, milk ]3~],
source of milk, and iodine metabolism needs to be taken into
account. it seems clear that analyses need to address the
uncertainties explicitly, and the confidence intervals and the
strength of the conclusions have to reflect them.
ARE THE PRESENTATION AND THE DISCUSSION OF RESULTS
COMPLETE?
One of the difficulties that the subcommittee
encountered while reviewing the work of the HTDS is that the
method that was used to calculate the doses is not clearly descnbed
in the documents that it was given. That information presumably is
scattered in the large number of documents that were prepared by
the HEDR project and the HTDS in the course of their work. it
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Review of the HTDS Draft Final Report
would be helpful to have access to a single document in which the
HEDR work is summarized, the results provided to the HTDS are
clearly described (with their strengths and weaknesses), and the
ways in which the HTDS made use of the HEDR results to
estimate individual thyroid doses are described in detail.
It is unclear to the subcommittee how the uncertainties
in the thyroid doses were estimated by the HTDS and the degree to
which they might have been underestimated. In part, the lack of
clarity reflects the lack of a single source that describes the dose
modeling, including the coefficients and the uncertainty factors.
There is a need to address explicitly the magnitude of the
uncertainties associated with residential and dietary histories.
There is a substantial description of how the dosimetry-related data
were collected from people but relatively little information on how
they were used. The input into the CIDER program is described as
"scenarios", but these are not explicitly described, in particular
how the scenarios were constructed from the data. There are a
number of references to the use of default values in the CIDER
program, but there is no discussion of which parameters used
default values or of the degree to which default values changed as
life circumstances changed for a given person (for example, if a
person moved from a farm to a city).
A tabular presentation of the pathways to diagnosis
would help the reader to assess how the final diagnoses were
assigned. Assignments were made in more than one way for each
of the clinical outcomes. A table for each diagnosis with a list of
the methods of diagnosis and the number of times each was used
should be included in the full report, and these data should be
looked at for indications of unsuspected ascertainment bias.
Dosimetry-error issues apparently were not fully treated
in the analysis of the study power. The same issue is raised by the
results, in particular, ignoring dosimetry error could lead to
unrealistically narrow estimates of the confidence limits that
should be applied to the estimated parameter values. It is unlikely
that the estimated dose-response relationships would change in an
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Summary of Responses to CDC's Questions
143
important way, but confidence intervals that take dosimetry error
into account would provide further information about the
uncertainty of risk estimates.
Some results were presented in an abstract, rather
uninformative manner. For example, there was a scatterplot of
individual thyroid doses on a logarithmic scale, but no table of the
frequency distribution of doses, which would have meant more to
readers. Similarly, one expects to see in radiation-epidemiology
reports tables that show observed and expected numbers of disease
outcomes in, say, four or five dose groups. Such key tables were
notably absent from the HTDS Draft Final Report.
A description of the estimated dose distribution
(distribution of median doses for the individuals in the study)
according to such important categories as geostratum, year of birth,
and amount of milk consumption in childhood would be helpful,
especially in interpreting the finding that the least exposed
geostratum appeared to have the highest rates of many of the
thyroid diseases or abnormalities.
it was not very clear from the report how confounders
of the dose-response relationship were treated, and results adjusted
for possible confounders were rarely given. The HTDS
investigators conducted analyses of the various thyroid-disease end
points to evaluate a number of possible risk factors for
confounding effects or effect modification, but they presented no
tables to show a summary of the results of these analyses for any
of the disease end points. Of particular value would be a
presentation of results stratified by sex, age at initial exposure,
magnitude of NTS and global fallout, and history of substantial
medical radiation exposure. A tabulation of the number of study
participants who were out of the dosimetry area for part of the
exposure period is also needed.
it has been suggested that the investigators should have
given more attention to comparing the rates of thyroid disease that
they found with the rates in other, unexposed populations.
However, comparisons with an external, general population are
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Review of the HTDS Draft Final Report
fraught with problems in that people living in various geographic
areas vary in their risk of thyroid diseases because of dietary and
other factors and the rates of detected disease depend heavily on
the frequency and sensitivity of thyroid examinations in the
population. Those circumstances produce screening effects that
cannot be readily disentangled so as to permit meaningful
comparisons with rates from other geographic regions that did not
have comparable screening. Therefore, the subcommittee believes
that the HTDS investigators nghtly chose to emphasize the internal
comparisons rather than general population comparisons.
The discussion of the results was seriously incomplete
in that it said little about whether the confidence intervals were
wide enough to be compatible with those of other, parallel studies.
Most important, there was no adequate discussion of how
dosimetric uncertainties might have affected the confidence
intervals and the statistical power of the study.
In the statistical-power analyses, it was assumed that
the dose uncertainties were all of the "Berkson type"-a type of
measurement error that does not affect statistical power. However,
if a substantial, fraction of the variability of the HEDR individual
dose estimates actually is due to non-Berkson error or to
multiplicative errors, or if there is a substantial additional
component of error due to uncertainties in milk consumption,
lifestyle, and residential history, the power or tne study might nave
been reduced below a point that would normally be considered
acceptable. Furthermore, the apparent heterogeneity among
geostrata might also have reduced statistical power. In contrast, if
the doses were systematically underestimated, as has been alleged
by others, that might tend to increase the statistical power of the
study.
ARE THE CONCLUSIONS REASONABLE?
Our overall assessment is that the design and execution
of the epidemiologic-clinical study was appropriate to the task. The
sample was based on an almost complete census of eligible
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subjects born in selected years in what are believed to be the high-
dose regions and inclusion of subjects born in the same years and
living in regions where the doses from Hanford releases were
lower. Efforts to elicit study participation were thorough and
appeared comparable for those with high and low doses. Care was
taken to avoid methodologic study biases. The clinical
examinations and laboratory studies used the best modern methods
of detecting and defining thyroid disease. Overall, the authors
deserve high marks for the carefully conducted and documented
epidemiologic and clinical work they performed.
To the degree that the dose is underestimated, the
imputed risk estimates will be too large; but systematic, across-the-
board dose underestimation does not alter the statistical
significance of dose-response trends. Hence, in this study in
which, as it turned out, the primary issue became whether there is
any association between IT exposure and thyroid diseases-the
impact of possible close underestimation might not change the
study conclusions appreciably, except for two caveats. First, if
there was an across-the-board underestimation of doses, the true
statistical power of the study would have been greater than one
would estimate it to be, given the reported dose distribution; the
negative results would be more persuasive than they are. Second, if
the doses were underestimated more for some study subjects than
for others, this would, in effect, act as another source of
measurement error that would tend to cancel out the gain in
statistical power achieved by having generally higher doses.
Therefore, a simple generalization about the effects of dose
underestimation cannot be given.
If the doses were systematically overestimated, the
statistical power of the study would be less than claimed.
in both versions of the analysis of mortality
data whether data are arrayed by year of birth or year of
death-SMRs for perinatal conditions and congenital anomalies in
the period before the Hanford releases (that is, before 1945) are
increased about as much as the SMRs in the period when exposure
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Review of the HTDS Draft Final Report
occurred. That constitutes evidence that exposure to ]3~{ iS
probably not responsible for the increased mortality from thyroid
disease in the Hanford study group, although some further analysis
is recommended.
The confidence intervals for the risk of thyroid cancer
in this study and the Utah NTS study overlap to some degree.
Moreover, on the basis of the considerations above, it is evident
that the confidence intervals for the HTDS in fact depend on
dosimetry-error assumptions; measurement errors in the dosimetry
of the type that would attenuate the dose-response association,
which we believe to be present, would cause the confidence
intervals for the HTDS to be appreciably wicler than the ones based
on the information in the Draft Final Report.
Uncertainties in the magnitude of individual thyroid
dose estimates and the relatively small sample in this study limit
the generality of the conclusions that one can draw from the study
regarding the magnitude of thyroid-cancer risk to other populations
exposed to similar doses from }3~. Data on thyroid-cancer risk are
awaited from the large number of thyroid cancers observed in
children exposed to high doses from the Chernobyl accident.
The statistical power of the HTDS to detect dose-
response relationships might have been overestimated because
effects of the types of dosimetry error that would attenuate the
associations were ignored. The evidence of heterogeneity of many
of the thyroid diseases or abnormalities among geoskata also
suggests that the power of the study was weakened by geographic
variations in unmeasured or unknown confounders that affected the
outcomes. Such reductions of statistical power lower our appraisal
of the study in relation to other studies and of the use of this
study's results for making predictions about disease risk in other
populations exposed to id at low doses and at low dose rates.
The results of the HTDS are fundamentally important to
the population living around Hanford. The study examined a
substantial fraction of the highly exposed population and failed to
find direct evidence of an effect of Hanford exposure on thyroid
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disease risk, nor was there evidence of abnormally high rates of
thyroid disease in the Hanford "downwinder" sample as a whole. It
is very likely that no other reasonable study of this population
could have found such effects-not only for technical reasons
(such as difficulties in reconstructing doses), but because factors
other than the Hanford releases appear to be more important in
determining the amount of thyroid disease in the population. The
fact that the two counties believed to have the least exposure
tended to show higher rates of thyroid disease than the most
exposed counties bears witness to that. Considerations of basic
factors, such as the prevailing wind direction and distance from the
Hanford site, indicate that those two counties should have had
less~3~T exposure than the other counties in the study, but their
disease rates were higher. That implies that there was not a strong
association between ]3~} exposure and thyroid disease.
Nevertheless, neither this evidence nor the negative dose-response
results rule out the possibility of a weak association.
We have already noted that the HTDS design and
conduct were as good as they could have been, given the size and
distribution of the population at risk and the long time between
exposure and the study. The thorough examination of the highest-
risk group-the youngest children living in the highest-dose
regions failed to find an increased incidence of thyroid cancer,
the hallmark effect of high thyroid doses from 13~. Even if some of
the factors that affected the distribution of dose (for example, milk
consumption) were poorly measured, they were as well measured
in this study as is possible 40-50 years after the fact.
In evaluating the HTDS, it is useful to distinguish what
the subcommittee regards as two aims of the study. The first was
the determination of whether patterns of thyroid morbidity among
those in the study region during the fallout period correspond to
likely patterns of exposure in the HTDS study sample irrespective
of specific estimated doses, the likely patterns of exposure being
based principally on location of residence during early childhood
(distance down wind) and milk-drinking habits. This study, by
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virtue of its size and how well contact and screening were
completed, appears to have had the ability to address that aim
effectively, although the presentation of results could be improved.
The second aim was to use assigned HEDR doses to estimate dose-
response relationships. Many of the caveats discussed in this report
about the effect of uncertainties in doses on the power of the study,
confidence intervals for the estimated dose-response relationships,
and the correspondence of the HTDS results with those of other
studies are related to the second aim. The HTDS might have
substantially overestimated its ability to assess a dose-response
relationship, because of unallowed-for uncertainties, both
systematic and random, in the HEDR doses.
The absence of a thyroid-cancer risk above expectation,
is based on a comparison of rates between high- and low-dose
regions and a dose-response analysis that used dose-reconstruction
methods and found no increased risk but did have wide
uncertainties in the reconstructed-dose estimates and hence in the
estimated risk coefficients. From those observations, one can only
state that at face value the HTDS was negative. If an exposure of a
population to 13~{ radiation of magnitude similar to that estimated
in the HTDS were to occur elsewhere, one cannot predict with
confidence whether an increase in risk would be seen. The small
number of thyroid-cancer cases and the wide uncertainties in
individual doses afford little confidence in the risk estimates
derivable from this study.
At the time of the initial release of the Draft Final
Report, the HTDS investigators indicated that residents of
downwind areas should fee} relief that their proximity to the
Hanford nuclear site did not result in increased risk of any thyroid
morbidity. Such statements are, according to the arguments above,
reasonable in specific instances. For example, a healthy 55-year-
old former resident of the area near the Hanford site (say, Benton
County) who remembers drinking a large amount of milk as a child
can take comfort in learning that there is no evidence that his or
her risk of thyroid morbidity is higher than that of other subjects in
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the general HTDS study area. The HTDS, in fact, appears to be
definitive on that point for most of the outcomes considered.
In contrast, for good reasons discussed above, the
HTDS was not designed to compare thyroid morbidity rates among
the entire population downwind from Hanford with those among
populations living elsewhere. At the various public-comment
meetings people who lived in down-wind areas stated that they
_ . ~ . . .
and their families experienced more thyroid disease than would
have been expected in the population at large. They could be right,
and their disease might have been the result of unusual fallout or
ingestion patterns. However, thyroid disease tends to run in
families, and the particular occurrences could be related to genetic
factors in the families, chance occurrences, or even mistaken
diagnoses. The small number of thyroid cancers detected in the
HTDS was in line with the background rates initially estimated for
the study, but the presence of screening effects makes it impossible
to compare this intensively screened sample with any other similar
population. Other thyroid conditions were much more commonly
detected in the sample, but again no comparison group has
undergone similar degrees of thyroid screening. The lack of
evidence of a dose-response relationship for any of these
conditions suggests-but does not prove that the overall risks
were unaffected by Hanford releases. The evidence does not rule
out (although it provides no support for) a weak association that
could affect, for example, those already susceptible to thyroid
disease because of predisposing genetic factors.
Thyroid cancer is not a common disease, and it would
be reasonable in future epidemiology surveys to identify,
document, and investigate clusters by using molecular-biology
probes to characterize genetic polymorphisms that could make
people more sensitive to ionizing radiation or to look for oncogene
prevalence in affected groups. These methods are developing
rapidly, and it is likely that they will play a role in future
environmental-epidemiology studies.
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WAS THE MATERIAL ACCURATE AND APPROPRIATE IN PROVIDING
GUIDANCE TO THE PUBLIC IN UNDERSTANDING THE STUDY
FINDINGS?
For the most part, the written messages in the Draft
Final Report, those about the report in public documents, and the
messages given orally by the HTDS investigators at the media and
public briefings were accurate, but they were sometimes
inappropriate and misleading because they included statements that
were too positive, definite, and strongly worded, given the
uncertainties that applied to the study. In addition, the uncertainties
related to the study were not discussed and should have been.
Clearly, those problems contributed to the public upset that
resulted from the release of the Draft Final Report.
However, the problems related to the report's release
should not overshadow the attempts made over the years to inform
and involve members of the public about the study. They were
valuable and generally done well. Such information channels as
newsletters, background fact sheets, and a Web site were good
ways of trying to reach members of the public directly with
information about the study, and they augmented the information
in the mass media. The subcommittee recommends that similar
public communication efforts be continued regarding this report
and others by CDC. Keeping the study process and activities as
"transparent" as possible for the public is valuable and should not
be abandoned because of the problems encountered with the
release of the Draft Final Report of this study.
IF THESE MESSAGES NEED TO BE AMENDED, HOW SHOULD THE
REVISED MESSAGES BEST BE COMMUNICATED TO THE PUBLIC?
Some of the overly positive messages given out at the
January briefing have already been softened through CDC efforts
during public meetings in Spokane and Seattle in May 1999.
Handouts, a summary of the findings, and other written materials
prepared by CDC also have conveyed similar information and
made more of an effort to explain that no epidemiologic study can
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determine "whether an individual person's thyroid disease is or is
not caused by Hanford radiation exposure" (Cary, 1999~.
Despite substantial attempts to publicize the May 1999
meetings, including paid advertising, they were not well attended
by the public. So the "softer" CDC message was not delivered
widely, although at least one newspaper did run a story about the
new CDC approach. Several factors can account for the low
attendance at the two meetings, including the period that had
elapsed between the January release of the report and early May,
the perception that no new information would be gained at these
meetings, and the greater distance of the two meeting sites from
Hanford, compared to Richiand, the site of the January briefing.
Another interpretation might be that both the HTDS and CDC have
lost some credibility on this issue and that people chose not to
listen to what they had to say. All those factors and others might
have been operating, but the last one should have serious
consideration and study before release of the final report. If
credibility has been lost, plans must be developed to try to restore
it to some degree, particularly for the release of the final report.
Given all the communication problems that resulted
from the release of the Draft Final Report, the subcommittee
recommends that another detailed communication plan be
developed for release of the final report. To the greatest extent
possible, those working on the plan should brainstorm about
unexpected situations like those which affected the release of the
draft report and devise plans to handle them more effectively. it is
imperative that messages from the final report take into account the
venous audiences being addressed and show concern and
sensitivity for the thyroid-health issues that people perceive as
affecting them. Any changes made to the Draft Final Report must
be clearly outlined and explained, including why they were made,
what group suggested that they be made, and what impact they
have had on the results of the HTDS. Every reasonable effort must
be made to present the filet picture of the study results, including
all the uncertainties and other problems.
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CDC and the RIDS personnel should work together on
the wording of the messages for the public about the final findings
of study. Academic freedom is of great concern in letting
researchers give their interpretations of the findings, but that does
not mean that alternative interpretations of the data by other
groups, such as CDC, should not be offered. It would be better to
reach a consensus; if it cannot be done, showing differing
interpretations is preferable to having one side dominate the other
to the point that a government agency overrides the predominant
point of view of the principal investigators, or vice versa. Such
advice goes against some risk-communication dogma that states
that the message should be kept simple and that all parties involved
should show a united front. Sometimes that works, but often when
members of the public are actively engaged in and educated about
an issue, such a simple approach backfires, as it did with the
release of the Draft Final Report.
A plan to brief the active citizen groups should be
developed so that they have enough information to be able to
respond to media inquiries about the report. A much simpler
briefing structure should be devised to make the information
available quickly to as many people as possible. In addition, an
embargoed release of the report to journalists should be arranged
so that they have a few days to read through it and develop
informed questions before the briefing. Many government agencies
and scientific organizations do that routinely and get much better,
informed coverage because of it.
As for details, the executive summary of the final report
should be edited carefully to eliminate unnecessary technical
jargon and complexity, which made it difficult for even educated
readers to understand portions of the Draft Final Report. All
written press releases, handouts, and other materials should be
dated and numbered for easy reference; that was not always done
with the material for the draft report. And all briefings should be
videotaped and transcribed for future reference by CDC, the HTDS
investigators, and others.
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Little information has been available about the quality
of communication to people who participated in the HTDS. A
random sample of those people should be surveyed about their
responses to the communication efforts carried out in connection
with the draft report to seek ways to improve communication with
them about the final report. The study participants seem to be an
overlooked group; they need to be brought more into the
communication loop.
WITH REGARD TO RELEASE OF FUTURE STUDY REPORTS, HOW
CAN CDC IMPROVE THE PUBLIC-COMMUNICATION PROCESS?
Attempts to establish and maintain an information
blackout before release of the Draft Final Report ran counter to the
previous spirit of information-sharing with citizen groups in the
region. The blackout, although somewhat understandable and
probably policy-driven, led to ill feelings among citizens who had
worked closely with the HTDS and CDC, and it led to a leaked
report. Trying to maintain such a blackout dunng multiple
briefings particularly in Washington, DC-is something that
CDC should reconsider when a controversial report of great public
interest is involved. If nothing else, the subcommittee recommends
that the briefing structure be simplified and that citizens who have
participated in the advisory process all along be given higher
priority in the briefing structure.
Multiple conference-call briefings, which are relatively
inexpensive, appear to be ineffective. None of those who
participated in them and provided information for the present
report liked them. They have many disadvantages, and the
subcommittee suggests that different ways be devised to brief
groups at different locations. Briefings by satellite, although
expensive, might pay off in the long run in more effective
communication. Other possible uses of advanced communication
technology, such as the World Wide Web, also should be
considered. A lower-technology way to brief groups in different
areas is to have simultaneous briefings led by different people
.
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Review of the HTDS Draft Final Report
involved in the study. That method has its problems, but they seem
less serious than those posed by conference-call briefings.
Many of the suggestions made for handling the final
HTDS report can also be applied to fixture CDC reports and need
not be restated here. However, the subcommittee feels that it would
be helpful for the CDC to ask a group of about a dozen people to
come together during a 1- or 2-day workshop to discuss how the
agency can improve its public-communication process and the
release of future reports.
Some of the people invited to such a workshop should
be experts in risk communication, but there also should be a wider
representation, including journalists, outside scientists who have
worked on CDC studies, and members of citizen groups who have
served on CDC advisory boards. Given careful planning, perhaps
with a few case studies distributed to participants in advance, such
a workshop might help CDC to avoid some of the pitfalls that
occurred with the release of the HTDS Draft Final Report.
One point for such a group to consider is the
advisability of publicly releasing draft reports before external peer
review and, if such a release is required by law or contract, how to
do so effectively. Although circumstances in this particular
situation might have forced the HTDS investigators and CDC to
release a draft report to the public and the media, it is problematic
to have preliminary information conveyed to the public if external
peer review could suggest important changes in the final report. If
substantial changes are made, what will the public think about the
study and the investigators? That their initial results were not
scientifically valid? That they raced to release information that was
politically favorable to the government and not to citizens in the
region? This is not a criticism of the actions that occurred, but a
call to think about these issues more carefully, not only for this
project, but also for others. Release of draft scientific studies,
although it potentially serves the information needs of the public,
also has the potential to cause confusion and to undermine the
credibility of researchers and government agencies. Of course,
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155
keeping information from the public can do the same thing, so this
is not an easy issue to deal with. It should, however, be carefully
considered not only by CDC, but also by other government
agencies, Congress, the National Academy of Sciences and
National Research Council, and the scientific community as a
whole. Science journalists, too, might need to re-evaluate how to
apply their own guidelines that advocate writing primarily from
peer-reviewed studies and reports as they are faced with more and
more cases in which government agencies and others announce the
results of unreviewed draft reports at news conferences.
Representative terms from entire chapter:
thyroid disease
