COMMUNICATING EFFECTIVELY ABOUT RISK MAGNITUDES,
PHASE TWO •
Location on the Page,
Units of Exposure Magnitude,
Simultaneous Presentation of Two Hazards,
and Other Hypotheses
Neil D. Weinstein, Peter M. Sandman,
and Paul Miller
Rutgers, The State University of New Jersey
September, 1991
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COMMUNICATING EFFECTIVELY ABOUT RISK MAGNITUDES,
PHASE TWO
Location on the Page,
Units of Exposure Magnitude,
Simultaneous Presentation of Two Hazards,
and Other Hypotheses
Neil D. Weinstein, Peter M. Sandman,
and Paul Miller
Rutgers, The State University of New Jersey
September, 1991
The research described in this document has been funded by the United
States Environmental Protection Agency under Cooperative Agreement
CR-814506. It has been subject to the Agency's peer and administrative
review, and it has been approved for publication as an EPA document,
#230-09-91-003. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
This document can be ordered from the Environmental Communication
Research Program, Cook College, Rutgers University, P.O. Box 231, New
Brunswick, NJ 08903.
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ACKNOWLEDGEMENTS
This research was conducted as part of a Cooperative Agreement between the
Environmental Communication Research Program of Cook College, Rutgers University,
and the Office of Policy, Planning and Evaluation of the U.S. Environmental Protection
Agency.
Ln addition to funding the research, Ann Fisher of OPPE worked closely with the
researchers on formulating hypotheses and a research plan. Dr. Fisher also offered
comments on the report itself after her return to academia, as did Frederick W. Allen
and Lynn Luderer of OPPE. It would be hard to find three project officers as
committed, congenial, and substantively helpful as Ann, Deny, and Lynn.
Anne Ingegno and Ann Marie Atwell of ECRP provided their usual superb level
of administrative support for the project
We are indebted as well to the Rutgers University undergraduates who recruited
subjects by telephone and managed the mailing of research materials and the collecting
of response questionnaires, and to the hundreds of New Jersey homeowners who
contributed their time.
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CONTENTS
BOTTOM LINE CONCLUSIONS AND RECOMMENDATIONS FOR
PRACTITIONERS 1
EXECUTIVE SUMMARY 9
CHAPTER ONE: INTRODUCTION 17.
The Research Problem 17
Summary of Phase One 18
1. The value of the research design
2. The effect of an action standard
3. The effect of the standard-only condition
4. The effect of advice
5. The effect of risk probability data or probability
data plus comparisons to smoking
6. The effect of risk comparisons and a graphical
presentation
7. The effect of providing maximum information
8. Responsiveness to risk magnitude information
Hypotheses for Phase Two 27
Experiment I
Experiment n
Experiment HI
CHAPTER TWO: METHODS ~ 31
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Overall Research Plan 31
Sample
Risk communication brochures
Feedback questionnaire
Recruitment procedure
Experiment I Methods 36
Design
Subjects
Formats
Procedure
Experiment II Methods 37
Design
Subjects
Formats
Procedure
Experiment HI Methods 42
Design
Subjects
Formats
Feedback questionnaire
Procedure
CHAPTER THREE: RESULTS 49
Demographic Characteristics 50
Distributions of demographic variables
Relationships between demographic variables and response
variables
Audience Evaluation 52
Brochure difficulty
Helpfulness of information
Amount of information in brochure
Uncertainty in understanding of risk
Format Effects on Risk Perception Variables: Experiment I ~ 56
Full design analysis
Analysis for high-exposure subjects
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Format Effects on Risk Perception Variables: Experiment II 63
Test of the locational hypothesis
Test of the test magnitude hypothesis
Test of the risk hypothesis
Comparison of the locational and risk effects
Comparison of the test magnitude and risk effects
Accuracy of illness probability estimates
Acceptable exposure level
Format Effects on Risk Perception Variables: Experiment in 72
Effects of joint versus separate presentation of hazards
Effects of hazard differences
Retest of the locational hypothesis
Retest .of the risk hypothesis
Comparison of the locational and risk effects
Accuracy of illness probability estimates
Effects of perceived hazard characteristics
CHAPTER FOUR: DISCUSSION 87
Dependent Variables 87
Findings 88
1. The risk magnitude effect
2. The effect of a risk ladder
3. The effect of location on the risk ladder
4. The effect of test magnitude
5. The effect of hazard differences
6. The effect of simultaneous presentation
7. Three other findings
Format Findings, Risk Communication Criteria, and Ethics 97
Next Steps 99.
REFERENCES 103
APPENDIX A: Experiment I Brochures, Formats, and Questionnaires 105
APPENDIX B: Experiment n Brochures, Formats, and Questionnaires 117
APPENDIX C: Experiment III Brochures, Formats, and Questionnaires 133
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TABLES
Table 1 Experiment n Format Conditions 38
Table 2 Experiment II Formats 39
Table 3 Experiment HI Format Conditions 43
Table 4 Experiment III Formats 44
Table 5 Distributions of Demographic Variables 51
Table 6 Significance and Direction of Associations Between
Demographic Variables and Response Measures 53-54
Table 7 Audience Evaluation Variables 55
Table 8 Experiment I Analysis of Covariance of Response Measures
by Format and Hypothetical Exposure Level 57
Table 9 Experiment I Least-Squares Adjusted Means and Standard
Deviations by Format and Hypothetical Exposure Level 5S-59
Table 10 Experiment I Analysis of Covariance of Response Measures
by Format and Hypothetical Exposure Level (High Hazard
Levels Only) 64
Table 11 Experiment II Analysis of Covariance of Format Effects 65-66
Table 12 Experiment n Least-Squares Adjusted Means and Standard
Deviations by Format 67-68
Table 13 Experiment ffl Analysis of Covariance of Format Effects 75
Table 14 Experiment HI Least-Squares Adjusted Means and Standard
Deviations by Format 76
Table 15 Experiment III Radon and Asbestos Ratings on Five
Characteristics 83
Table 16 Experiment HI Correlations of Hazard Ratings with Response
Measures 84
FIGURES
Figure 1 Experiment I Effects on Perceived Threat of Adding a
Ladder of Exposure Levels to a Standard 60
Figure 2 Experiment II Effects of Location, Test Magnitude, and
Risk on Perceived Illness Probability 62
Figure 3 Experiment n Effects of Location, Test Magnitude, and
Risk on Perceived Threat 73
Figure 4 Experiment n Effects of Location, Test Magnitude, and
Risk on Mitigation Intentions 74
Figure 5 Experiment in Effects of Location, Risk, and Joint
Presentation on Perceived Threat 78
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Figure 6 Experiment EQ Effects of Location, Risk, and Joint
Presentation on Mitigation Intentions 79
Figure 7 Experiment III Effects of Location, Risk, and Joint
presentation on Perceived Illness Probability 80
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Communicating Effectively about Risk Magnitudes:
Bottom Line Conclusions and Recommendations for Practitioners
This is a brief summary of key conclusions and recommendations from the
research so far. For a longer summary of the Phase Two research, see the Executive
Summary or Chapter Four. For a longer summary of the Phase One research, see
Chapter One of the Phase Two report or the Executive Summary of the Phase One
report.
Probably the most important thing to say about the conclusions and recommenda-
tions that will follow is that they are preliminary. The effects we have found are often
small, taking a careful study with a big sample to find. They are based on people's
reactions to hypothetical exposure data; we do not know if people respond similarly to
real exposure data. And they are based on just one or two studies; experienced social
scientists know not to rely too heavily on a finding until it has turned up in several
different studies using several different methodologies. In addition, participants in this
research were much better educated than the general population. Finally, the research
design confronted people with personal choices about an individually remediable
pollutant in their homes; ^ public risk controversy might have generated very different
responses.
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Practitioners cannot usually wait for definitive results, of course. Since you have a
job to do, a risk to describe, you are better off following the advice below than ignoring it.
But see it as tentative.
It is worth emphasizing that this research effort focuses on ways of explaining risk
magnitudes more effectively - that is, ways to help people understand the size of their
risk. A more controversial class of risk communication strategies attempt to influence
risk responses by manipulating emotions or behavior rather than through improved
understanding (examples include dramatic fear appeals, social pressure, rewards for
compliance, etc.). These non-cognitive approaches can be very effective - but many
scientists object to them.
Five Factors that Affect Risk Response
Data about the Actual Risk. With everything else held constant, subjects
responded with higher perceived threat when the data they were given (risk
. probabilities plus comparisons to smoking) told them the actual risk was higher.
In the Phase Two research, a ten-times-higher risk affected risk perceptions but
not mitigation intentions; a 24-times-higher risk affected both.
This is an encouraging bottom-line conclusion: Telling people the size of the
risk they face does help encourage an appropriate response. But substantial
differences in actual risk yield relatively modest differences in perceived risk and
action intentions. The Phase One research showed that the effect of data about
the risk can easily be swamped by other factors, such as an action standard or a
risk ladder.
2. An Action Standard. The Phase One research found that formats that
.included an action standard were superior to formats without an action standard in
helping people respond in proportion to the actual risk. That is, the relationship
between actual risk and perceived risk, and between actual risk and mitigation
intentions, was stronger with an action standard than without. The effect of
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providing an action standard, in fact, was stronger than the effect of providing data
about the risk.
The standard was especially powerful in helping people distinguish levels
above the standard from those below the standard - so powerful that it sometimes
created an artificial discontinuity in risk perceptions at the standard. It also helped
people distinguish levels just below the standard from those far below the stan-
dard. On the other hand, an action standard did not help people make the
distinction between levels just above the standard from those far above the
standard.
Practitioners should always provide a standard when one exists, accompa-
nied where appropriate by warnings that risks just below the standard are nearly
as risky as those just above, and that risks far above the standard are much more
risky than those just above. (An action standard without additional risk information
is useful when an apathetic response is anticipated and the goaJ is to provoke
more risk aversion. See Number Four below.)
3. Advice. People said they felt less uncertainty and had a better understand-
ing of their risk when advice was provided. More importantly, people in the Phase
One study often said they would mitigate at levels below the standard, but those
receiving action advice showed this tendency least. That is, adding advice to the
standard made people less likely to "overreact" vis-a-vis the standard, more likely
to accept the recommendation not to take action at low levels. Advice was not
similarly useful at high levels; it did not increase the probability that those above
the recommended action level would plan to act (most already said they planned
to act).
Providing explicit advice is thus especially useful for panic prevention, to
deter overreaction at low risk levels. Its value for increasing remedial action at
high levels (beyond what would be expected with a standard alone) has not been
demonstrated.
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4. A risk ladder. People felt more at risk when presented simply with a
suggested "action level" at which mitigation is recommended than when presented
with such a standard located midway up a risk ladder. In the Phase One re-
search, the ladder included mortality data and risk comparisons; in Phase Two it
did not. In both studies, the context that the ladder provided - the information
that levels higher than one's own are not rare - appeared to reassure subjects
and reduce their perception of risk. In Phase Two, the presence or absence of a
risk ladder, even without any additional information, had an effect on perceived
risk equal to a several-fold difference in actual risk.
If the communicator's goal is maximum risk aversion - that is, if the hazard
is serious and the audience is inclined toward apathy - a standard without
additional information is ideal; its very ambiguity generates the desired risk-averse
response. If panic fe a problem and the goal, is to provide reassuring context, on
the other hand, a risk ladder is worth adding.
5. Location on the Risk Ladder. By displacing the risk ladder, the Phase Two
research located the same hypothetical reading with the same risk information
either one-quarter of the way up the ladder or three-quarters of the way up the
ladder. The resulting locationai effect significantly affected perceived risk in two
experiments, and mitigation intentions in one. This locationai effect was roughly
equivalent in size to the effect of an order of magnitude of actual risk. Risk
information developed to guide laypeople is often arrayed on a risk ladder, and the
structure of the ladder may be determined more or less arbitrarily. How low
should the ladder begin? How high should it rise? Should the scale be linear or
logarithmic? The answers .to these questions are not obvious. What is clear from
the data is that people's risk perceptions can be substantially altered - whether
intentionally or arbitrarily - by cos .r-tructing the ladder so that their risk appears low
or high on the page.
It may be impossible to construct a risk ladder that makes optimal use of
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the locations! effect for all risk levels included on the ladder. For helping people
distinguish between high and low levels of a particular risk, X, the most effective
ladder would be truncated at both ends, so that high levels of X appeared at the
top of the ladder and low levels of X at the bottom. For helping people see that X
is actually less serious than Y, on the other hand, the ideal ladder would be
extended upward, so that all levels of X clustered near the bottom of the ladder.
The best ladder to help people see that X is actually more serious than Z would be
extended downward, clustering all the levels of X near the top. A "universal
ladder* incorporating all three risks would extend both upward and downward, and
would cluster all the levels of X near the middle. These three extended ladders
would all be improvements on the original truncated ladder in encouraging an
appropriate response to between-hazard risk differences - but they would all be •
worse than the original in encouraging people to discriminate within-hazard risk
differences.
Six Factors that May Not Significantly Affect Risk Response
Risk Comparisons. In the Phase One research, the use of risk compari-
sons to cigarette smoking had two effects: it made people feel the brochure was
more helpful and they understood their risk better, and on some measures it made
them less risk-averse (for example, the comparisons raised the highest level
people would find acceptable). However, the comparisons had no effect on
people's ability to distinguish high risks from low risks: no effect on the accuracy
of illness probability estimates or on the relationship between actual risk and
perceived risk or mitigation intentions. In other words, the impact of risk probabili-
ty data was not improved by the inclusion of comparisons to smoking risks.
Risk comparisons may of course prove more helpful in ways not examined
in this research - different comparisons, different situations - but the research so
far provides little guidance on how to deploy risk comparisons usefully.
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2. Graphical Presentation. A bar graph showing risk probabilities at different
exposure levels functioned in the Phase One research exactly like risk compari-
sons. It improved people's ratings of the helpfulness of the brochure and their
certainty about their risk, and made them somewhat less risk-averse. However,
there were no significant differences between graphical and strictly quantitative
presentations of risk data in the extent to which people distinguished high levels
from low levels or radon from asbestos. Graphical display, in other words, did nol
strengthen the relationship between the actual risk and people's responses to that
risk.
It is of course possible that different graphical devices would show a greatei
impact on risk response.
3. Test Magnitude. The Phase Two research tested the hypothesis that
people respond to risk data in terms of the magnitude of the test numbers them-
selves, quite apart from the risk represented by those numbers. By expressing
asbestos risk alternatively in fibers per liter and in fibers per cubic foot, a 30-fold
difference in test magnitude was achieved without any difference in risk (as
presented in terms of probabilities plus smoking comparisons). No significant
effects of the test magnitude manipulation were found.
This somewhat surprising finding is reassuring. Concentration levels for
radon in water, for example, are typically much greater than for radon in air,
although the waterborne risk is usually lower. It is encouraging that homeowners
are apparently able to disregard the misleading test magnitude cue, at least when
mortality information and smoking comparisons are also provided.
4. Hazard Differences. The Phase Two research found no differences be-
tween radon and asbestos in the composite threat perception index or in mitiga-
tion intentions, when risk level and location w.n the page were held constant. The
three hazard attributes on which radon and asbestos were perceived differently -
difficulty of reducing the risk, unfamiliarity, and natural/man-made - were not
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significantly correlated with risk response. By contrast, the two attributes on which
radon and asbestos were ripj perceived differently - dread and lethality -were
significantly correlated with perceived risk. Thus, although radon and asbestos
are perceived differently with respect to some hazard characteristics, these are not
the characteristics that are tied to perceived riskiness.
A different pair of hazards - radon and nuclear waste, perhaps - that
differed in dread or perceived lethality would be expected to differ in perceived risk
as well.
5. Simultaneous Presentation. The final factor tested in the Phase Two
research was the possibility that the simultaneous presentation of asbestos and
radon risks on the same ladder might help subjects understand that the asbestos
risk was less serious than the radon risk. This hypothesis was rejected. There •
were no significant differences between the joint and separate presentations for
either radon or asbestos.
Of course it is possible that a different use of simultaneous presentations
might help owners take note of risk differences - for example, presentations that
included the different action levels for the two hazards, or presentations that
directed readers' attention to the differences more forcefully or interactively.
6. Information Overload. One of the formats tested in Phase One presented
more information than any other (risk probability data, risk comparisons, an action
standard, advice, verbal labels, a risk ladder). Yet it scored as well as or better
than the other formats on almost all measures of communication success, includ-
ing people's certainty about the risk and their evaluations of the amount of
information provided and the helpfulness of the brochure.
"Information overload" may be an issue for still more complex presentations
of risk information, or for audiences that are less interested or less educated. But
no evidence of overload has been found for the formats tested so far. For most
uses, in fact, this "maximum information" condition is probably optimal. The likely
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exceptions would be cases where no action standard exists or where apathy is a
major problem and the communicator wishes to encourage maximum risk aver-
sion.
The Bottom Line
In general: Don't worry about information overload. Always include an action
standard if one exists. Except where maximum risk aversion is your goal, always include
risk probability data (if they are available), an appropriately constructed risk ladder, and
advice for different levels:
If you are worried about apathy and want to encourage maximum risk aversion:
Give people a standard and no other risk information.
If you are worried about panic and want to encourage minimum risk aversion:
Give people advice for different levels, specifying at what levels you recommend action
and at what levels you recommend doing nothing. Include a risk ladder that extends to
levels higher than those your audience will experience.
If you are trying to help people distinguish high from low levels of a single hazard:
Construct a risk ladder with the high levels at the top and the low levels at the bottom.
If you are trying to help people distinguish between hazards or understand that all
levels of a particular hazard are relatively high or low in risk: Construct a ladder that is
extended upward or downward, so that the hazard you want to depict as low has all its
levels near the bottom of the ladder, and the hazard you want to depict as high has all its
levels near the top.
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EXECUTIVE SUMMARY
It is difficult to convey information to citizens about the magnitudes of risks to which
they are exposed. As many discouraged policy-makers have discovered, citizens often
ignore information designed to alert them to significant and remediable risks, and thus fail
to take appropriate action. Yet these same citizens may insist on remedial action with
respect to other risks that are too improbable or too irremediable to merit the attention
they receive.
Studies have identified many factors other than risk magnitudes that influence how
the public responds to particular risks. Much less research has attempted to determine how
to explain the magnitudes of risks, and thus to improve the correlation between risk and
response.
To fill this important gap in our knowledge, the Environmental Communication
Research Program at Cook College, Rutgers University and the U.S. Environmental
Protection Agency undertook the research reported here. This is the second phase of an
on-going research effort. The report of the Phase One research was published in Septem-
ber 1989 (Communicating Effectively about Risk Magnitudes, by Neil D. Weinstein, Peter
M. Sandman, and Nancy E. Roberts), and is available from either the Environmental
Communication Research Program or the U.S. Environmental Protection Agency.1
The Overarching question examined by the present research is the extent to which
different ways of presenting risk data can help individuals perceive their risk accurately and
respond appropriately. Each subject received one hypothetical home test result for either
asbestos or radon contamination (in one condition subjects received both an asbestos and a
radon reading). The experimental manipulation was a one-page explanation of the dose-
copies, write or call either: Environmental Communication Research Program,
P.O. Box 231, Cook College, Rutgers University, New Brunswick, NJ uC903, (908) 932-
8795; or Office of Policy, Planning and Evaluation, U.S. Environmental Protection
Agency, PM-220, Washington, DC 20460, (202) 382-6995.
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risk relationship included as part of a four-page information brochure provided by the
researchers. Subjects used this information to assess the risk associated with their assigned
test result; their answers to questions about the risk constituted the measure of the impact
of the experimental treatment
Three experiments were conducted, all using randomly selected central New Jersey
homeowners who had not in fact tested their homes for the hazards in question The three
studies are referred to throughout this report as Experiments I, II, and in respectively. A
total of 1,418 subjects provided usable data, each for one experiment only.
Five measures of risk perception were used. The most sensitive of these was the
composite index of threat perception, comprising four items that were strongly intercorrel-
ated': perceived likelihood of harmful effects, perceived seriousness, concern, and fear. A
single question about mitigation intentions was treated as a second dependent variable, in
order to have a behavioral measure. The third dependent variable was subjects' estimates
of illness probability. Except in the first experiment, the experimental manipulations
provided explicit data on illness probability; this item was therefore conceptualized more as
a comprehension item than as a risk perception item. The last two dependent variables
were judgments of mitigation difficulty and choices of the highest asbestos or radon level'
subjects would find acceptable (that is, would choose not to mitigate). None of the
experimental manipulations addressed these two issues directly; accordingly, no impact was
predicted.
The findings are discussed below in terms of the first two dependent variables, the
composite index of threat perception and mitigation intentions. In general, effects on the
composite index were stronger than effects on the single-item measure of mitigation
intentions, though both were usually in the same direction. This is probably attributable to
the greater sensitivity of the composite index, rather than to any difference in how percep-
tions and intentions are affected by the experimental variables.
Six different factors were examined (in one or more of the three experiments) to
determine their impact on subjects' risk perception: actual risk probability, the presence of
a risk ladder, location on the risk ladder, units of exposure magnitude, differences between
two hazards, and simultaneous presentation of two hazards. Care was taken to make sure
each factor was varied separately, with the others tightly controlled. Effects were found for
the first three factors, but not for the second three. The results will be discussed in the
order in which the factors are listed. Three additional findings are mentioned briefly at the
end.
1. The risk magnitude effect. Both Experiment II and Experiment III included a
test of the impact of actual risk on subjects' risk perceptions (risk was explained in terms of
expected mortality and comparisons to smoking). In Experiment II, a 10-fold increase in
risk significantly increased the composite index of perceived threat, but had no significant
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effect on mitigation intentions. In Experiment III, a 24-fold increase in risk significantly
increased both the composite index and mitigation intentions.
The finding that risk affects risk perception is not surprising. On the contrary, it
would be shocking if risk variations of an order of magnitude or more were invisible to
subjects instructed to make judgments about the extent of their risk. This is especially the
case in the relatively serious range of hypothetical risks to which subjects were assigned (3
and 30 deaths per thousand in Experiment n, 5 and 120 deaths per thousand in Experiment
Comparable differences in deaths per billion might well have had negligible effects.
The finding of a significant risk effect should not be interpreted as meaning that
subjects had a thorough understanding of the risk data presented to them - much less that
they were prepared to act on that understanding. The only dependent variable with a "right
answer" was illness probability estimates. Subjects in all conditions tended to underestimate
their risk, and those in the high risk conditions underestimated it the most. That is, illness
probability estimates did increase as actual risk (that is, actual illness probability) increased,
but the gap of unrealistic optimism also increased with increasing risk.
2. The effect of a risk ladder. Experiment I tested the hypothesis that subjects
would perceive their risk to be greater when presented simply with a suggested "action
level" at which mitigation is recommended than when presented with such a standard
located midway up a risk ladder. Even though the ladder did not include risk data, the
context it provided — the information that levels higher than one's own are not rare - was
expected to reassure subjects and thus reduce their perception of risk.
The hypothesis was confirmed, albeit weakly, for the composite index of perceived
threat, but not for mitigation intentions.
The finding that a risk ladder reduces perceptions of threat helps explain the Phase
One finding that subjects were most risk-averse when presented simply with a standard (as
opposed to other treatments that provided risk data, risk comparisons, advice, etc.).
Apparently, people presented simply with two pieces of information, the recommended
action standard and their own reading, are likely to interpret this information in alarming
ways. The mere addition of a risk ladder tells them nothing about death rates at the differ-
ent levels, or even about the frequency with which these levels are encountered. But the
range of levels included on the ladder at least suggests the range of levels that experts must
expect people to encounter. This contextual information appears to reassure subjects
somewhat, especially when their readings are above the action standard.
The size of the risk ladder effect cannot be compared directly with the size of the
risk effect, since they were studied in different experiments. But indirect companion is
possible. Averaged across all hypothetical test results, the addition of a risk ladder
decreased the composite threat perception index by 0.86 units on a 19-unit scale (4.5% of
the total scale range); above the standard, where the reassuring effect was stronger, the
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decrease averaged 1.23 units (6.5%). In Experiment II, the effect of a 10-fold increase in
risk was 1.78 units (9.4%); in Experiment III, a 24-fold increase in risk yielded an average
increase in perceived threat of 3.69 units (19.4%). The presence or absence of a risk ladder
thus has an effect on perceived risk equal to a several-fold difference in actual risk.
The effect is large enough to be of practical value. If the communicator's goal is
maximum risk aversion — that is, if the hazard is serious and the audience is inclined
toward apathy — a standard without additional information is ideal; its very ambiguity
generates the desired risk-averse response. If panic is a problem and the goal is to provide
reassuring context, on the other hand, a risk ladder is worth adding.
3. The effect of location on the risk ladder. The locational hypothesis was intro-
duced at the end of the Phase One research to account for that study's finding that many
formats were able to help subjects distinguish the risk of high versus low levels of asbestos
or radon, but no format successfully helped subjects distinguish the risk of asbestos from the
risk of radon. The risk associated with a particular level of asbestos or radon, it was noted,
was proportional to that level's location on the risk ladder (higher risks were higher on the
ladder), while the difference in risk between asbestos and radon was not reflected in their
respective ladders. If subjects were responding to location on the ladder rather than to risk
information, therefore, their risk perceptions would be sensitive to within-hazard differences
but not to between-hazard differences - exactly what the Phase One data had shown.
The locational hypothesis was tested in Experiments II and III. By displacing the
risk ladder, the same hypothetical reading with the same risk information was located either
one-quarter of the way up the ladder or three-quarters of the way up the ladder. Both
experiments found a significant locational effect on the composite index of perceived threat.
In Experiment H, a displacement of half a page led to a 1.49-unit effect on the 19-unit
threat perception index (7.8% of the total scale range), while a 10-fold difference in actual
risk produced an effect of 1.78 units (9.4%). In Experiment HI, a displacement of half a
page yielded a difference of 2.70 units (14.2%) in the composite index of perceived risk,
while a 24-fold risk difference added another 3.69 units (19.4%). The findings with respect
to mitigation intentions were less compelling. In Experiment HI, the effect on mitigation
intentions was statistically significant, but in Experiment II it was too small to achieve
statistical significance. This is probably a result of the insensitivity of the single-item
measure of mitigation intentions, not an indication that location on the risk ladder affects
perceptions more than intended behavior.
The effect of location on risk perception is a sizable effect and an important finding.
Risk information developed to guide laypeople is often arrayed on a risk ladder, and the
structure of the ladder may be determined more or less arbitrarily. How low should the
ladder begin? How high should it rise? Should the scale be linear or logarithmic? TL-e
answers to these questions are not obvious. They depend not just on the seriousness of the
risk and the anticipated apathy or panic of the audience, but also on the actual range of
levels that are typically encountered and on the ethical values of those constructing the
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ladder. What is clear from the data is that people's risk perceptions can be meaningfully
altered — whether intentionally or arbitrarily — by constructing the ladder so that their risk
appears low or high on the page.
4. The effect of test magnitude. In the Phase One research, radon exposures were
expressed in picoCuries per liter, while asbestos exposures were in fibers per liter. The risk
associated with a level of radon with the same numerical test magnitude was substantially
higher than the risk associated with that level of asbestos; that is, X pCi/1 of radon
constitutes a greater risk than X f/1 of asbestos. This suggested another possible explana-
tion for the difference between within-hazard effects and between-hazard effects found in
Phase One. Perhaps subjects responded appropriately to differences in level within a
hazard because the test numbers themselves varied with the risk, while failing to respond to
between-hazard risk differences because the numbers were not substantially different.
This hypothesis was tested in Experiment II. By expressing asbestos risk alternatively
in fibers per liter and in fibers per cubic foot, a 30-fold difference in test magnitude was
achieved without any difference in risk.
No significant effects were found. In fact, the composite index of perceived threat
and the measure of mitigation intentions were actually somewhat lower — though not
significantly so - in the High Test Magnitude condition than in the Base condition. This
somewhat surprising finding is reassuring. Concentration levels for radon in water, for
example, are typically higher than for radon in air, although the waterborne risk is usually
lower. It is encouraging that homeowners are apparently able to disregard the misleading
test magnitude cue, at least when mortality information and smoking comparisons are also
provided.
5. The effect of hazard differences. A third possible explanation was also consid-
ered for the Phase One rinding that subjects were more sensitive to within-ha-'-ard risk
differences than to between-hazard risk differences. Perhaps there were particular
characteristics of the two hazards, asbestos and radon, that made the former more alarming
to subjects than the latter, thus tending to cancel out the effects of the fact that the latter
was the greater risk (at the levels specified).
Experiment HI tested for risk perception differences between radon and asbestos.
To help account for any differences that might emerge, Experiment HI also added measures
of five hazard characteristics: difficulty of reducing the risk, dread, lethality, unfamiliarity,
and the natural/man-made distinction.
. Surprisingly, no differences were found between radon and asbestos in the composite
threat perception index or in mitigation intentions, when risk level and location on the page
were held constant Of the five hazard characteristics measured, three - difficulty of
reducing the risk, unfamiliarity, and natural/man-made - showed significant differences
between radon and asbestos; radon was seen as easier to mitigate, less familiar, and less
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14
man-made than asbestos. None of these three hazard characteristics showed significant
correlations with the dependent variables. By contrast, the other two characteristics -
dread and lethality - were significantly correlated with perceived risk, but did not signifi-
cantly distinguish radon from asbestos. Thus, although radon and asbestos are perceived
differently with respect to some hazard characteristics, these are not the characteristics that
are tied to perceived riskiness. Two different hazards - radon and nuclear waste, perhaps
- that differed in dread or perceived lethality would be expected to differ in perceived risk
as well.
6. The effect of simultaneous presentation. The final factor tested in the Phase Two
research was the possibility that the simultaneous presentation of asbestos and radon risks
on two parallel ladders — in effect, on the same ladder — might help subjects understand
that the asbestos risk was less serious than the radon risk. This was tested in Experiment
III, and the hypothesis was rejected. There were no significant differences between the
joint and separate presentations for either radon or asbestos. Of course it is possible that a
different use of simultaneous presentations might help owners take note of risk differences
- for example, presentations that included the different action levels for the two hazards, or
presentations that directed readers' attention to the differences more forcefully or interac-
tively.
It should be noted that the simultaneous presentation hypothesis was very narrowly
framed in the present study. That is, location on the risk ladder was held constant.
Whether the two hazards were presented simultaneously or separately, the asbestos risk was
always one-quarter of the way up the ladder, and the radon risk was always three-quarters
of the way up the ladder. In many practical applications, by contrast, presenting two
hazards simultaneously would mean extending the risk ladder upwards and downwards to
encompass the range of risks entailed by the two different hazards. Since the normal range
of asbestos hazards is lower in risk than the normal range of radon hazards, a joint
presentation as opposed to separate presentations would tend to move asbestos readings
farther down on.the page and radon readings farther up. The locational effect would thus
decrease asbestos risk perceptions and increase radon risk perceptions - even if there were
no added effect of simultaneity.
To put this point another way, the findings that have been discussed so far strongly
support the locational explanation for the Phase One result that subjects are much better
able to distinguish within-hazard risk differences than between-hazard risk differences, at
least insofar as asbestos and radon are concerned. Phase One subjects had trouble
recognizing that radon was a more serious risk than asbestos,, the Phase Two results
strongly suggest, not because they were misled by differences between the two hazards or by
similarities in the numerical size of the test numbers, but because radon and asbestos were
each presented on a separate risk ladder that encompassed a limited range of risks. On a
"composite" risk ladder that ran from the lowest level of the asbestos ladder to the highest
level of the radon ladder, the findings suggest, asbestos risk perceptions would be dimin-
ished and radon risk perceptions would be augmented.
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15
It may be productive to envision a "composite" risk ladder embracing a still wider
range of hazards - one that can cover highly unlikely risks (pedestrian is struck by light-
ning) at the bottom of the ladder and highly likely ones (smoker gets lung cancer) at the
top. If such a ladder can be devised in a way that is comprehensible to laypeople (it would
have to be logarithmic, certainly), it should excel at helping people perceive between-hazard
differences. But within-hazard differences would be compressed into a small portion of this
expanded ladder. Inevitably, therefore, the composite ladder would be much less successful
than narrower single-hazard ladders at pointing to within-hazard differences.
7. Three other findings. Three other findings of interest concern demographics,
estimates of illness probability, and maximum acceptable levels.
• Older subjects tended to be less risk-averse than younger subjects; less educated
subjects tended to be less risk-averse than more educated subjects; men tended to be
less risk-averse than women. However, none of the associations between a demo-
graphic variable and a risk perception variable was significant for all three experi-
ments.
• As mentioned earlier, subjects were consistently low in their estimates of illness
probability, even though the information called for in the questionnaires was
provided in the brochures. Although risk probability estimates increased as the
actual risk increased, so did the extent of the underestimation.
• Subjects' judgments of the highest exposure level they would consider acceptable
varied depending on the options provided; when responses were converted Into a
simple 1-12 scale independent of the options provided, no significant differences
were found. This suggests that subjects did not choose a particular level of risk in
response to the question, but rather selected a choice that was a few responses away
from the first option, zero. In essence, they chose a location, not a risk. Subjects'
highest acceptable levels were usually significantly lower than the EPA action guide-
lines provided.
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CHAPTER ONE
INTRODUCTION
The Research Problem
There is considerable agreement about the difficulty of conveying information to the
public about the magnitudes of risks. As many policy-makers have noted in discour-
agement, citizens often ignore information designed to alert them to significant risks, and •
thus fail to take appropriate individual action; yet these same citizens may insist that
government or industry take inappropriate remedial action for other risks that are too small
to merit the attention they receive. Even within the realm of individually mitigable risks,
studies of the public response to radon, for example, have shown a less-than-ideal relation-
ship between the individual's test result and his or her response. Furthermore, the response
to risk data about one hazard is often very different from the response to data about a dif-
ferent hazard. Some hazards seem to provoke great anxiety in the public, while others -
even given test results that indicate a comparable risk — elicit much less concern.
A substantial research literature has identified many of the factors other than risk
magnitudes that seem to determine how the public responds to particular risks. But much
less research has sought the best ways of explaining risk magnitudes, with the goal of
improving the correlation between risk and response.2 Until the research whose second
2For an excellent introduction to the relevant issues, see National Research Council,
Improving risk communication. Washington, DC: National Academy Press, 1989 (see
especially Appendix C, by B. Fischhoff). A brief review of empirical risk communication
17
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stage is reported here, there has been relatively little empirical data to support claims that
one approach works better than another.3
It is worth emphasizing that this research effort focuses on ways of explaining risk
magnitudes more effectively - that is, ways to help people understand the size of their risk.
A more controversial class of risk communication strategies attempt to influence risk
responses by manipulating emotions or behavior rather than through improved understand-
ing; examples include dramatic fear appeals, social pressure, rewards for compliance, etc.
These non-cognitive approaches can be very effective - but many scientists object to them,
believing that risk is a technical problem that should be explained in technical (though in
understandable and perhaps simplified) terms. The research whose second phase is
reported here represents one of the most sustained efforts to date to find out how far
cognitive approaches can bring us: how much risk responses can be shaped by effectively •
presented data alone.
Summary of Phase One4
The research conducted in the first funding period raised issues explained further in
the Phase Two research. Before detailing the Phase Two hypotheses, methods, and
studies can be found in Rohrmann, 1990.
3Although the research literature on this issue is limited, research by Smith, Des-
vousges, and colleagues deals usefully with the relatively effectiveness of different
formats for explaining radon risks. See for example: Smith, V.K., Desvousges, W.H.,
Fisher, A., and Johnson, F.R. (1987). Communicating radon risk effectively: A mid-
course evaluation. Washington, DC: Office of Policy, Planning, and Evaluation, U.S.
Environmental Protection Agency (EPA-230-07-87-029).
4A complete report on the Phase One findings was published in September 1989.
For copies, write or call either: Environmental Communication Research Program, P.O.
Box 231, Cook College, Rutgers University, New Brunswick, NJ 08903, (908) 932-8795;
or Office of Policy, Planning and Evaluation, U.S. Environmental Protection Agency,
PM-220, Washington, DC 20460, (202) 382-6995. Weinstein, N., Sandman, P., and
Roberts, N., Communicating Effectively about Risk Magnitudes.
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19
findings, a brief summary of Phase One findings and conclusions is appropriate.
The Phase One research examined a variety of promising risk presentation formats
and tested their success in communicating about two different hazards, geological radon and
asbestos. These two hazards have several common properties: They confront individual
homeowners rather than being community-wide problems; tests can be carried out (and
must then be communicated) to indicate the seriousness of the risk; and individual-level
mitigation is possible. Among the other hazards that fall into this important category are
lead contamination from water pipes within the home, contamination of home wells by toxic
chemicals in groundwater, and emissions from urea-formaldehyde foam used as insulation.
Successful communication about this class of hazards is particularly important
because it can increase the likelihood that people take actions to reduce health risks when
such actions are appropriate, and can decrease the likelihood of excessive worry and
unneeded action when risk levels are low. Different communication strategies may be
appropriate for hazards that do not permit individuals to assess their own risk and make
their own decisions about mitigation.
Seven formats were evaluated, as follows:
Fl. Risk Probabilities. Information about expected lifetime mortality (deaths per
thousand people) at various levels of exposure.
F2. Risk Probabilities and Comparisons. Fl with comparisons to smoking risks
added.
F3. Graphic Probabilities. Fl displayed in histogram form.
F4. Standard. Information about the recommended action level only.
F5. Standard + Risk Probabilities and Comparisons. F4 + F2.
F6. Standard + Advice. F4 with detailed action advice and verbal labels for four
ranges of exposure levels.
F7. Standard 4- Advice + Risk Probabilities and Comparisons. F6 + F2.
For reasons that will become clear later in this summary, it is important to note that
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five of the seven formats visually displayed exposure levels in the form of a vertical ladder
(Fl, F2, and F5 through F7); in F3 the horizontal axis represented radon exposure and
histogram bars indicating risk rose from this axis. Only F4 had no visual representation of
exposure levels.
Also important to understanding these results is the fact that the recommended
action level for radon represents approximately a 25-fold greater risk than the action level
used for asbestos.
Subjects were New Jersey homeowners who had in fact not tested their homes for
the hazard in question (either radon or asbestos). Each subject was asked to assume that
he or she had tested and obtained a specified reading (in picoCuries per liter for radon anc
in fibers per liter for asbestos). Four readings were used for each hazard, one well below
the recommended action level, one slightly below the level, one slightly above the level, anc
one well above the level. (The risk associated with each specified radon reading was
roughly 25 times the risk associated with the comparable asbestos reading.) Each subject
also received a four-page brochure discussing the hazard in question. The first three pages
were constant across conditions; the fourth page consisted of the experimental manipula-
tion. Each subject received one hypothetical reading for either radon or asbestos and one
brochure explaining the hazard and its risk.
Subjects then responded to an evaluation questionnaire. Dimensions covered
included: audience evaluation of the brochures, perceived risk seriousness, likelihood of
illness, concern, fear, mitigation difficulty, intentions to take action, maximum acceptable
exposure levels, and numerical estimates of illness probability. Responses to the risk
seriousness, illness likelihood, concern, and fear questions were highly correlated with one
another and were therefore combined to form a single measure of "perceived threat."
The experimental design thus comprised seven presentation formats, four exposure
levels, and two hazards — a total of 56 cells. The final sample consisted of 1,948 subjects,
an average of 35 subjects per cell.
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21
The discussion that follows summarizes the major findings from Phase One and their
implications.
1. The value of the research design. The experimental design using hypothetical
exposures proved to be a very efficient, cost-effective, and flexible way to investigate format
effects on risk perception and behavioral intentions. It would have been extremely difficult
and costly to find subjects who had actually tested for the hazards in question, yet had not
had access to extensive information from other sources (confounding any possible study
results). Moreover, supplying such subjects with suboptimal information would have posed
substantial ethical problems. Subjects found the experimental task interesting and compre-
hensible. Their responses suggest that they took the task seriously, and meaningful
differences were found in their responses to the seven formats. Ultimately, it will be
important to field test key findings obtained by this methodology, to identify any differences
that may exist between responses in the hypothetical testing situation and responses in a
real testing situation. But we now have in hand a methodology and a frame suitable for
testing increasingly sophisticated hypotheses about the effects of risk presentation formats.
2. The effect of an action standard. Formats F4 through F7 included an action
standard - a level (midway between the second and the third exposure levels) below which
mitigation was not recommended, and above which it was. Formats Fl through F3 did not.
One important goal for communicating risk magnitudes is to have people with low readings
see their threat as smaller and less often undertake remedial action than people with high
readings. The formats with an action standard were superior to the formats without an
action standard according to this goal.
The presence of a standard not surprisingly increased the likelihood that subjects'
action intentions matched the action recommendations; in other words, subjects were more
likely to plan to mitigate at levels above the action standard and to plan not to mitigate at
levels below the standard if they were told what the standard was. Though obvious, this is
not a trivial finding; it shows that explicit action standards significantly affect individual
action plans, and thus can contribute meaningfully to public health.
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However, the presence of a standard also created an artificial discontinuity in hazard
responses as one goes from just below the standard to just above the standard. This
discontinuity or "step" exaggerated the minimal increase in actual risk between the second
specified exposure level and the third. This effect, too, is not surprising; many commenta-
tors have complained about the public's tendency to dichotomize around a standard,
perceiving levels just below the standard as safe and those just above as risky. The disconti-
nuity found was, if anything, smaller than might have been expected.5
(Responses to an action standard are presumably influenced by people's beliefs
about government regulation and regulatory standards, especially whether they are likely to
be too lax or too tight. Among those who take a standard literally, the greater the trust in
the standard, the greater the expected discontinuity in risk response above versus below the
standard.)
More surprisingly, F4 through F7 did a better job than Fl through F3 of helping
subjects distinguish between very low and moderately low readings. That is, the presence of
a standard helped subjects understand that levels just below the standard were appreciably
more risky than levels far below the standard. A similarly improved differentiation between
high and very high levels was not found; the action standard did not affect the difference
between reactions to high and reactions to very high test results.
3. The effect of the standard-only condition. Although four formats (F4 through
F7) included an action standard, only F4 provided the standard without any additional
information - that is, without a risk ladder, without risk probabilities or risk comparisons,
and without advice and verbal labels keyed to various levels.
This condition stood out from the others in many ways. Most importantly, it led to
the highest perceptions of threat and the greatest, intentions to mitigate (especially at levels
below the standard). It also produced the most risk-averse responses on several other
5Studies of actual radon mitigation suggest that an action guideline or standard may
lead to an artificial step in risk perceptions but not in behavior. See Doyle et al.T 1991,
and Weinstein and Sandman, 1991.
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outcome measures. These findings strongly suggest that an action standard without
additional risk information is useful when an apathetic response is anticipated and the goal
is to provoke more risk aversion (so long as the overresponse is not excessive). Where
panic and overreaction are likely responses, on the other hand, a standard-only communica-
tion should be avoided.
The differences obtained between format F4 and formats F5 through F7 were
greater than can be explained by the risk probability information (F5 and F7), risk compari-
sons (F5 and F7), or advice (F6 and F7) that these other formats contained. The authors
speculated that the uniquely risk-averse responses to F4 might have resulted from the fact
that F4 lacked the risk ladder present in F5 through F7. In the absence of a ladder,
subjects had no way of telling what range of test results is "typical"; they might therefore
have reacted as though the finding of any amount of radon or asbestos were a serious
problem. In contrast, subjects who had a ladder and a low test result could see that their
exposure level was low on the page, a reassuring observation. Even if their level was above
the standard, the presence of still higher rungs on the ladder may have been reassuring.
Individuals with results on the very top rung of the ladder might have become more
frightened than subjects with no ladder at all. (This was not tested; the highest hypothetical
level used was still well below the top of the ladder.) For everyone else, however, an
exposure ladder appeared to be reassuring, and the absence of a ladder in format F4
appeared to lead to increased risk aversion.
4. The effect of advice. Two formats (F6 and F7) went beyond the dichotomy
created by the standard to provide verbal labels and action advice at different levels.
Although people in this study tended to be more risk-averse than the action recommenda-
tions (they often said they would mitigate at levels below the standard), those receiving
action advice showed this tendency least. That is, they were the most likely to accept the
recommendation not to take action at low levels, the least likely to "overreact" vis-a-vis the
standard. Subjects also reported less uncertainty and better understanding of their risk
when advice was provided.
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It is not surprising that the presence of more graduated and detailed advice than a
simple standard increased the likelihood that subjects would act in ways consistent with
what was advised. However, the effect was not true for all risk levels. Subjects receiving
formats F6 and F7 were less risk-averse at low levels than subjects receiving format F4
(standard-only), but they were not more risk-averse at high levels. Providing explicit advice
is thus especially useful for panic prevention, to deter overreaction at low risk levels. Its
value for increasing remedial action at high levels (beyond what would be expected with a
standard alone) has not been demonstrated.
5. The effect of risk probability data or probability data plus comparisons to
smoking. Risk probability information was provided in formats Fl, F2, F3, F5, and F7; it
was accompanied by comparisons to smoking in F2, F5, and F7. Subjects receiving these
formats did a better job of estimating illness probabilities at their levels than subjects
receiving no risk probability information. This shows that the risk probability information
was not totally ignored or totally incomprehensible. But the improvement in illness
probability estimates was not matched by any change in perceived threat or mitigation
plans. Analysis of F4 versus F5 and F6 versus F7, for example, shows that the addition of
risk probability data (plus comparisons) did not lead to a further differentiation between
high and low risks beyond that produced by the standard alone (F4) or the standard plus
advice (F6).
In short, people seemed somewhat able to understand risk probability information -
that is, to respond to risk probability questions in a way that was systematically related to
the information provided — but no format was found that helped them integrate this
information into their views of the seriousness of the threat or the need for action. When a
standard was provided, furthermore, the effect of the standard seemed to vitiate the much
weaker effect of the risk probability information.
6. The ef^.ct of risk comparisons and a graphical presentation. Format F2 added
comparisons to smoking to the risk probability information in format Fl; format F3
displayed the information from Fl in the form of a histogram. Both comparisons to
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25
smoking and graphical display improved subjects' ratings of the helpfulness of the brochure
and their certainty about their risk. On two of the four measures of risk aversion, risk
comparisons and graphical display also had the effect of making subjects less risk-averse;
for example, when they were asked what levels they would find personally acceptable,
higher responses were given by subjects receiving formats F2 and F3 than by subjects
receiving format Fl.
However, there were no significant differences between F2 and Fl or between F3
and Fl in the extent to which subjects distinguished high levels from low levels or radon
from asbestos. That is, comparisons and graphical display had no effect on the accuracy of
illness probability estimates, or on the variation in threat perceptions or action plans with
level or with hazard. Comparisons and graphical display, in short, helped subjects feel that
they understood their risk better, and made them less risk-averse, but did not in fact
strengthen the relationship between the actual risk and subjects' responses to that risk. It is
of course possible that different comparisons or different graphical devices would show a
greater impact on risk response.
7. The effect of providing maximum information. Format F7 presented more
information than any other (i.e., risk probability data, risk comparisons, an action standard,
advice, and verbal labels). Except for the histogram in format F3, F7 had everything that
any other format had. Yet it scored as well as or better than the other formats on almost
all measures of communication success, including subjects' evaluations of the helpfulness of
the brochure and their certainty about the risk. We found no evidence that subjects were
confused by "information overload" in format F7.
Of course, format F7 is not an option if the communicator is not prepared to provide
an explicit standard and action advice. And it is probably not advisable in cases where
apathy is a major problem and the communicator wishes to encourage maximum risk
aversion in the audienc^. (The decision to "encourage" this or any particular response in an
audience raises values issues as well as empirical ones, of course.) For most other purpos-
es, however, F7 was the format of choice among the seven tested.
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8. Responsiveness to risk magnitude information. None of the formats tested
succeeded in giving subjects an accurate sense of the magnitude of their risk. All seven
formats did a fair job of producing threat perceptions and action plans that varied with the
level of radon or asbestos (F4 through F7 did best), but none of them was really able to
produce threat perceptions and action plans that were appropriately different for radon
than for asbestos. Yet the level of risk for each radon reading was roughly 25 times the
risk for the comparable asbestos reading. That is, the lowest radon reading was 25 times as
risky as the lowest asbestos reading, and the highest radon reading was also 25 times as
risky as the highest asbestos reading. None of the formats tested did an adequate job (and
none did appreciably better than the others) in helping subjects recognize this major
berween-hazard difference.
It is not surprising that formats F4 and F6 failed in this regard. They provided an
action standard that ignored the difference between radon and asbestos and no risk
probability information to point out that difference. Thus, F4 and F6 suggested implicitly
that radon and asbestos risks are about equal. It is somewhat more surprising that the risk
probability information in F5 and F7 did little to overcome the misleading impression
created by the standard. But it is believable that an action standard is a stronger cue than
risk data.
What is most surprising is the fact that, for most outcome variables, even formats Fl
through F3 — formats with risk probability information and no action standard - produced
no greater differences between the two hazards than the other formats. Of the seven
formats tested, formats Fl through F3 would be expected to yield the greatest realization
that radon is more hazardous than asbestos at the same exposure level. (Formats explicitly
pointing out the difference between radon and asbestos or offering a different action
guideline for the two hazards were not tested.) In fact Fl through F3 did produce slightly
more awareness of the radon-asbestos distinction in estimates of illness probability, but not
in threat perceptions or action plans.
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Hypotheses for Phase Two
Phase Two was designed to resolve some of the issues raised by the Phase One
results.
Experiment I. The first new experiment was suggested by an unexpected Phase One
observation. As noted earlier, reactions to the standard-only format stood out in the Phase
One findings. On a variety of measures (perceptions of threat, intentions to mitigate, levels
judged personally acceptable, etc.) the standard-only condition produced the most risk-
averse response. The authors hypothesized that the strongly risk-averse response to the
standard-only format might result from the fact that it was the only condition that did not
contain a ladder or other visual representation of exposure levels. In the absence of a
ladder, people lacked "locationaT information about how many rungs above or below the
standard their level was. In the other formats, by contrast, the risk ladder provided cues
about the range of risks that might be expected from radon or asbestos, cues that may have
reassured subjects about their assigned levels. Such locational cues may be extremely
important in determining people's responses to risk magnitude information.
The validity of this speculation could not be tested in Phase One because there were
several differences between the standard-only condition and the other formats (including
the presence or absence of risk probability information, risk comparisons, and explicit
action advice). Experiment I was therefore designed to test the idea that simply adding an
exposure ladder to the standard-only format would affect perceived risk and related
variables in the direction of reduced risk aversion. (For figures showing the Experiment I
formats, see Appendix A.)
The standard-only format was replicated from Phase One, but this time it was
compared to a new format that had not been tested previously. The new format contained
a ladder of possible test results (but no information on the risk associated with those
results) together with the information about the standard.
Experiment II. The second experiment explored two hypotheses developed to
explain some perplexing Phase One results, together with a third, more conventional
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hypothesis. (For figures showing all Experiment II formats, see Appendix B.)
The Locational Hypothesis. The first idea to be tested had been labeled the
"locationaT hypothesis in Phase One. The focus in Phase One was on the information
provided in the final page of the test brochure: a dichotomous government standard,
mortality information for different exposure levels, comparisons to smoking risks, mitigation
advice for different levels, etc. Except for the standard-only condition and one graphic
display condition, all the formats included an "exposure ladder" on which the information to
be provided in that treatment was arrayed. In all these cases, subjects assigned a low
hypothetical test result found their result low on the exposure ladder and, hence, low on the
page; those assigned a result near the standard found it in the middle of the page; those
assigned a high result found it near the top of the page.
Perhaps the most important finding in Phase One was the failure of any of the seven
formats to help subjects sufficiently appreciate that the lowest radon reading was 25 times
as risky as the lowest asbestos reading, and the highest radon reading was 25 times as risky
as the highest asbestos reading. Though several formats proved useful in producing
appropriate differences in response across the four levels for each hazard, no format was
efficacious in producing appropriate differences in response between the two hazards. In
other words, where risk was proportional to location (within hazards), several formats
worked well; where risk was not proportional to location (between hazards), no format
worked well.
"Why were all formats able to produce a level effect while no format was able to
produce an appropriately large hazard effect?" the Phase One report asked. It answered
with the hypothesis that "people were responding to the position of their test result on the
exposure level ladder in the brochure":
This "locational hypothesis" asserts that the within-hazard variations with test result
were chiefly a product of the placement of the level on the page, a purely arbitrary
"locational" factor, and not an appreciation of the magnitude of the risk. The
locational hypothesis neatly accounts for the failure to achieve an appropriate
response to the difference between the two hazards. There were no locational
differences between radon and asbestos; a particular level of radon (in picoCuries
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29
per liter) was located at about the same point on the risk ladder as the comparable
level of asbestos (in fibers per liter), even though the radon exposure represented a
25-fold higher risk. Thus the study's success in achieving a level effect and its failure
to achieve a hazard effect can both be explained by the locational hypothesis.
The locational hypothesis suggests that changing the vertical position at which a
given test result appears on the exposure ladder (i.e., low, middle, or high on the page)
should affect perceptions of risk, even though the actual level of risk is held constant
The Test Magnitude Hypothesis. A second possible explanation for the Phase One
failure to find an adequate hazard effect focuses on the magnitude of the numbers in which
the radon and asbestos tests were expressed. The four hypothetical test results for radon
(in pCi/1) and for asbestos (in f/1) were chosen in Phase One to be roughly the same size
numbers (rather than the same size risks), arrayed around the action guidelines of 4 pCi/1
for radon and 3 f/1 for asbestos. The levels used for radon were 0.8, 3.5, 4.5, and 24 pCi/%
while the levels used for asbestos were 0.8, 2.5, 3.5, and 24 f/L If Phase One subjects
responded to neither locational cues nor risk information, but rather to the size of the raw
numbers they were given to indicate their test result, their responses to radon and asbestos
would be very similar. This "test magnitude11 hypothesis, in other words, can also account
for the Phase One findings.
This second hypothesis suggests that the magnitude of the numbers on the exposure
scale affects perceived risk. For example, if an asbestos exposure level of 15 f/1 were
converted into a level of 450 f/cubic foot, then it would be perceived as more risky simply
because of the larger numerical value, even though the objective risk remained constant.
The Risk Hypothesis. For contrast with the hypothesized locational and test
magnitude effects, the second experiment also considered a more obvious notion, that
increasing the objective risk level would result in an increase in the perceived risk, even
when the position of the test result on the page and the magnitude of the test numbers
were both held constant Experiment n was designed to permit comparisons of the size of
the locational effect, the test magnitude effect, and the risk effect
Experiment IH. The third experiment explored two new hypotheses and retested two
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old hypotheses from Experiment II. (For figures showing all Experiment III formats, see
Appendix C.) The first new hypothesis was the idea that simultaneous presentation of
exposure and risk information for two hazards (radon and asbestos) on the same risk ladder
would result in greater appreciation of the difference in risk between the two hazards than
separate presentation of the information. At the levels commonly encountered, radon
represents a considerably greater risk than asbestos, a fact that the public has not generally
appreciated. Perhaps showing the two hazards and their associated risks together on the
same page might drive home the point, leading to increased perceptions of risk for radon
and decreased perceptions of risk for asbestos (vis-a-vis the separate presentation of the
two hazards).
The second new hypothesis concerned the presence of a "hazard" effect independent
of risk — the idea that radon and asbestos, because of their different histories and charac-.
teristics, might produce differences in perceived risk even when the actual risk, test
magnitude, and position on the page were held constant. In the expectation that such a
hazard effect would emerge, questionnaire items on various hazard characteristics (dread,
lethality, naturalness, etc.) were added to the study so that the ability of these charac-
teristics to explain hazard effects could be assessed.
The third and fourth hypotheses for Experiment III were retests of the locational
and risk effects.
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CHAPTER TWO
METHODS
Overall Research Plan
The general research paradigm replicated that of Phase One. That is, subjects were
asked to assume a particular hypothetical home test result for either radon or asbestos, to
read a brochure about the radon or asbestos hazard, and then to complete a series of
questions dealing with their assessment of the risk represented by their assigned level. Both
the assigned test result and the format of the interpretive brochure were systematically
varied, and the results were analyzed in terms of the effects of different format characteris-
tics on perceptions of risk. The Phase Two experiments differed from those in Phase One
in that they utilized new formats in order to test the hypotheses described in the Introduc-
tion.
Because of the possibility that some study participants would already know about the
recommended 4 pCi/1 action guideline for radon — and that this knowledge would affect
their responses to their hypothetical radon test result — most of the Phase Two research
made use of the asbestos hazard instead. This was especially important because the
formats tested in Experiments n and III of Phase Two did not include an action guideline.
Materials and procedures that were common to all three Phase Two experiments are
described here. The specific variations used for each of the separate experiments will be
discussed in detail in the methods section for each experiment
31
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32
Sample. As in Phase One, randomly selected central New Jersey homeowners were
recruited as volunteers. The specific population of interest was all homeowners listed in
the New Brunswick, New Jersey telephone directory. This directory includes many
adjoining communities in Middlesex County, New Jersey, varying widely in ethnic, income,
and educational characteristics. The research was limited to homeowners because it was
thought that questions concerning the need for home mitigation would be less hypothetical
for this group than for apartment dwellers or renters.
Risk communication brochures. Four-page brochures presenting information from
government publications about the nature of the risk from asbestos or from radon were
prepared. The first three pages of each brochure, containing general information about the
hazard, were the same across all conditions; for Experiment III the length was cut to two
pages (see Appendices). The final page, referring to the size of the risk for different
exposure levels, was the format being tested, and differed according to experimental
condition. The simplest format, referred to as the "standard-only" format, only described
the level at which government agencies recommended mitigation. All the other formats
contained a vertical ladder representing different hazard exposure levels. Experimental
variations included the risk levels represented, the degree to which the ladder extended
downward or upward beyond the levels assigned to subjects, and the units in which
exposures on the ladder were expressed.
Although there is an EPA recommended action level for radon (4 picoCuries per
liter), there is none for asbestos. Previous research (Phase One) had created an asbestos
"action level" based on EPA guidelines for schools, and this guideline was used for Experi-
ment I in Phase Two as well In the other two Phase Two studies, however, no recom-
mended action levels were specified; the focus was on examining how homeowners interpret
or use risk data.
Feedback questionnaire. Subjects also received an evaluation questionnaire (see
Appendices), adopted with little modification from the Phase One questionnaire. It
addressed three response dimensions, as follows:
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33
Demographics. To measure demographic variables, questions were asked about age,
sex, and educational level.
Audience Evaluations. Four questions were used to obtain the subjects' evaluations
of the risk communication brochure. The first item assessed the difficulty of the brochure.
Choices ranged from 1 = very difficult to 4 = very easy. The second item asked subjects to
rate how helpful the brochure was in understanding the hazard, with values ranging from 1
= didn't help to 4 = very helpful. Subjects were also asked to rate how much information
was included in the brochure (1 = much too little to 5 = much too much). Finally, subjects
were asked how confident they were that they understood the risk from the hazard after
reading the brochure. Choices ranged from 1 = uncertain to 4 = very certain. For the
most part, there was no reason to expect that the format variations tested in the present
experiments would affect audience evaluation, but these variables were included in case of
unanticipated effects. Subjects' evaluations of the difficulty and helpfulness of materials are
not of course reliable measures of how well they were actually able to use the materials.
Risk Responses, The key questionnaire items were of course the risk-related
response measures. A total of eight questions were asked that bore on various aspects of
subjects' perceptions of the risk. A ninth item was a composite index of perceived threat
created from four of the eight questions (numbers 5-8 below).
(1) Mitigation Difficulty. The perceived difficulty of mitigation was measured with a
single 4-point scale, ranging from 1 = very easy to 4 = very difficult. (The wording
of the question was changed in Experiment III.) The experimental conditions did
not vary in the information they provided about mitigation difficulty, and this
question was included mainly to check for the possibility that effects on perceived
risk would also affect perceptions of mitigation difficulty. Perceptions of mitigation
difficulty also provide background for understanding mitigation decisions. No effects
of format differences on ratings of mitigation difficulty were found in any experi-
ment Therefore, although this variable will be included in the tables, it will not be
discussed in the text
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34
(2) Acceptable Exposure Levels. Subjects were asked at what level of exposure in their
main living area they would feel satisfied, so that they would not spend more money
trying to get the level even lower. If a particular way of presenting information
increases perceptions of risk, it might also lead people to request a lower level.
Twelve choices were provided. When the test result was expressed in fibers per liter,
the choices ranged from 0 f/1 to 350 f/1. When the test result was expressed in
fibers per deciliter, the choices ranged from 0 f/dl to 350 f/dl. When the test result
was expressed in fibers per cubic feet, the choices ranged from 0 f/cu. ft to 10,500
f/cu. ft. This variable was not included in Experiment III.
(3) Illness Probabilities. One question was asked about the potential for illness from the
subjects' hypothetical test result levels. In Experiment I, where no probability
information was included, this question shows how people infer risk from a standard
or a standard plus ladder. In Experiments II and DI, where probability information
was incorporated into the formats, this question was conceptualized as a measure of
comprehension rather than as a measure of perceived risk. In Experiments I and 13,
a 9-point scale was used, with alternate points labeled: "no chance," "1 in 1000," "1 in
100," "1 in 10," and "certain." (Hypothetical risks lower than 1 in 1000 were not used
in the study.) Percentage equivalents were also given. The response scale for illness
probabilities was simplified in Experiment HI. All choices were given in deaths per
thousand and all the points were labelled. Thirteen choices were given, and the
correct responses (5 in 1000 for low-risk subjects and 120 or 125 in 1000 for high-risk
subjects) were among these choices.6
Subjects in Experiment II were often inaccurate in choosing the illness probability
posed by their hypothetical test result, but it was unclear whether they had difficulty
determining the correct probability from the information provided or had difficulty
finding that probability on the feedback question. The revisions to the scale in Experi-
ment HI made the correct interpretation much easier to determine. In the revised
response scale, all choices were in deaths per 1000 because the last brochure page gave
the risk in this unit Also, the correct answer was one of the labeled responses, so that
interpolating to find the right answer - as had been necessary in Experiment II - was no
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35
Errors were measured by the number of steps between a subject's response
and the correct answer, with all steps being given equal weight. In other words, the
answers to this question were analyzed as if the scales had equal intervals (1 to 9 in
Experiments I and II; 1 to 13 in Experiment III) rather than in terms of the actual
probabilities listed. If the numerical probabilities had been used instead, the size of
each subject's error would depend not only on the number of steps away from the
correct answer but on the portion of the scale where the correct answer lay, since
the difference in probability between adjacent steps grows larger as one moves
toward higher probabilities.
(4) Mitigation Intentions. Subjects were asked how likely they would be to spend S1000
in order to reduce their level of asbestos or radon close to zero. The choices ranged
from 1 = deGnitely would take action, to 5 = definitely would not. This is the
closest the study design could come to studying actual behavior.
(5) Perceived Likelihood. A 7-point scale assessed subjects' perception of the Likelihood
of harmful effects from their hypothetical test results. The scale values ranged from
1 = no chance to 7 = certain.
(6) Perceived Seriousness. A 6-point scale assessed perceived seriousness, with values
ranging from 1 = no risk to 6 = very serious risk.
(7) Concern. Concern was measured using a 5-point scale ranging from 1 = not at all
concerned to 5 = extremely concerned.
(8) Fear. Fear was measured using a 5-point scale ranging from 1 = not at all fright-
ened to 5 = extremely frightened.
(9) Composite Index, of Perceived Threat. The four items pertaining to perceived Likeli-
hood, perceived seriousness, concern, and fear were added together to form a
composite index of perceived threat (range = 4-23). This was done in both the
Phase One and the Phase Two research to develop a more sensitive and r liable
longer required.
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36
response measure, and because these four variables were highly inter-correlated
(with inter-item correlations ranging from .57 to .76), suggesting they tapped the
same general dimension. (Other items that might have been included in the index
variable, such as illness probability estimates or mitigation intentions, had somewhat
lower correlations with items 5-8.) Internal consistency as assessed by coefficient
alpha was .84 for the composite index.
Recruitment procedure. As in the Phase One research, potential subjects were
recruited by telephone, with numbers selected randomly from directory listings. They were
screened to ensure that they were 18 or older, were homeowners, and had not tested their
homes previously for radon or asbestos. (Those who had tested for radon were included in
the sample but were assigned only to asbestos conditions.) Recruiters alternatively asked to
speak with male and female residents to balance the sex of subjects.
A total of 8,024 potential subjects were reached by telephone and asked to partici-
pate in one of the three experiments. Of these, 2,431 (30.3%) agreed and were sent
questionnaires and test materials. Of those who agreed, 1,418 (58.3%) actually returned
their completed questionnaires. At least two follow-up telephone calls were made to
encourage cooperation by people who had agreed to take part
Experiment I Methods
Appendix A shows the brochures, formats, and questionnaires for Experiment I.
Design. The design of the first experiment was a 2 x 4 (format x level) between-
subjects design. The four hypothetical test result levels were the same as in Phase One
(0.8, 2.5, 3.5, and 24.0 f/1), as was the asbestos action standard of 3.0 f/I.7 As in Phase
7No standard or guideline for home asbestos currently exists. The 3.0 f/1 level used
here is derived from a U.S. Environmental Protection Agency standard that does exist
for schools. The weekly acceptable school exposure is the product of the .1 f/'cubic
centimeter maximum acceptable exposure level and the assumed school exposure
duration of 40 hours per week. Home effects are typically based on an assumed
exposure of 126 hours per week (18 hours per day). Converting the maximum accept-
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37
One, the test result levels were symmetric about the action guideline, with two near it (one
slightly below and one slightly above) and two far away (one well below and one well
above).
Subjects. Subjects were 435 homeowners recruited from Middlesex County. Of
2,295 potential subjects reached by telephone, 706 (30.8%) agreed to participate in the
study. Of those who agreed, 60.2% returned a completed questionnaire.
Formats. The standard-only format was unchanged from Phase One. It stated that
"A home level of 3 f/1 or above corresponds to the risk at which EPA requires action in
schools and public buildings." No other information about the risk of different levels was
provided. The new standard 4-ladder format added an exposure ladder. The exposures on
the ladder ranged from .1 f/1 at the bottom to 100 f/1 at the top. The suggested action
level of 3.0 f/1 was at the middle of the scale and was identified by a large arrow containing
the text: "A home level of 3 f/1 or above corresponds to the risk at which EPA requires
action in schools and public buildings."
Procedure. Homeowners who agreed to participate were randomly assigned to one
of the eight format x level conditions and mailed the appropriate test brochure format,
"imaginary" test result level, and feedback questionnaire.
Experiment II Methods
Appendix B contains the brochures, formats, and questionnaires used in Experiment
II. Tables 1 and 2 compare the four Experiment n formats on a single page.
Design. The second experiment used a single-factor between-subjects design with
four levels of the treatment condition (format). Each format included an exposure ladder
with risk information (extra cancer deaths per 1000 people exposed) and smoking compari-
sons at several points along the ladder.
able school exposure to an equal home exposure yields an "acceptable" home level of
about 3 f/1.
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TABLE 1
Experiment II Format Conditions
Format
Base
Displaced
High Test
Magnitude
Test Result
Magnitude
15
15
450
Test Result
Units
fibers/liter
fibers/liter
fibers/cubic ft
Objective
Risk
(deaths/1000)
3.0
3.0
3.0
Location
on Page
Low
High
Low
High Risk
15
fibers/deciliter 30.0
Low
38
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TABLE 2
Experiment II Formats
(X indicates position of test result on exposure ladder)
Base
15
Displ
15
- X
aced High
Magn1
- X
450
Test High
tude
-
- X 15
Risk
-
- X
fibers/liter fibers/liter fibers/cubic ft fibers/deciliter
39
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40
Four versions were used. (1) For the "Base" scale, asbestos exposure levels were
expressed in terms of fibers/liter. (2) The "Displaced" scale used the Base scale ladder
shifted upwards, so that the same test result would appear higher on the page by about half
the length of the scale. (3) The "High Test Magnitude11 scale was identical to the Base
scale except that exposure levels were expressed in terms of fibers per cubic foot. With this
change in units, the labels on the exposure scale were 30 times larger than when the labels
were expressed in fibers per liter, though the risk was unchanged. (4) The "High Risk"
scale, finally, used the same numbers to describe exposure levels as the Base scale, but with
units of fibers per deciliter. Thus, the risk at each level (in deaths per 1000 and in smoking
comparisons) was ten times greater than the comparable risk on the Base scale.
Subjects in the first three conditions (who received the Base, Displaced, or High Test
Magnitude formats) were assigned a hypothetical test result equivalent to a cancer risk of.
3.0 deaths per 1000 persons. Subjects in the fourth condition (who received the High Risk
format) were assigned a test result equivalent to a risk level of 30 deaths per 1000 - ten
times the risk in the first three conditions.
Three key comparisons were planned to analyze the effects of the experimental
variations:
• Base versus Displaced - the effects of location (a variation of half the length of the
ladder).
• Base versus High Test Magnitude — the effects of the size of the numbers in which
the test result was expressed (a 30-fold difference).
• Base versus High Risk - the effects of actual risk (a 10-fold difference).
Two additional comparisons compared the sizes of the preceding effects:
• Displaced versus High Risk — the relative effects of a half-page displacement of the
risk scale as compared to a 10-fold variation in risk.
• High Test Magnitude versus High Risk — the relative effects of a 30-fold variation in
test numbers as compared to a 10-fold variation in risk.
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41
Care was taken to hold as many features of the formats as possible constant, while
manipulating only the position (Base or Displaced), numerical magnitude (Base or High
Test Magnitude) or risk level (Base or High Risk) of the test result. (See Table 1, p. 38.)
Subjects. Subjects were 449 homeowners recruited from Middlesex County. A total
of 2,488 persons were reached by telephone and were qualified; of these, 753 (30.3%)
agreed to participate in the study. Of those who agreed, 59.6% returned a completed
questionnaire.
Formats. The test of the locational hypothesis depends on the Base scale and the
Displaced scale; location on the page was varied, while units of exposure magnitude and
actual risk were held constant The Displaced scale used the same units as the Base scale
(f/1), but was shifted so that the test result of 15.0 f/1 appeared about three quarters of the
way up the page, compared to only one-quarter of the way up the page on the Base scale..
Because the Displaced scale was shifted upwards, the range of values shown on the
exposure ladder was different The Base scale exposure levels ranged from 3.5 to 1500 f/1,
while the Displaced scale had exposure levels ranging from .15 to 75 f/1. At any particular
height on the page, the risk on the Base scale was about 23 times the risk on the Displaced
scale. If a locational effect exists, subjects should have seen their risk as greater in the
Displaced condition than in the Base condition because their level appeared higher on the
page.
The test of the test magnitude hypothesis used the Base scale and the High Test
Magnitude scale. The two were identical in that the hypothetical test result was in the
same relative position (one-quarter of the way up the page) and represented the same
cancer risk (3.0 deaths per 1000). But the units on the exposure ladder were changed from
fibers/liter in the Base scale to fibers/cubic foot in the High Test Magnitude scale.
Because a cubic foot is about 30 times the volume of a liter, the corresponding exposure
ladder numbers were 30 times larger than those on the Base scale. The numeric labels on
the exposure ladder in the High Test Magnitude condition ranged from 105 to 45,000, while
on the Base scale they ranged from 3.5 to 1500. The assigned hypothetical level in the
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42
High Test Magnitude condition was 450 fibers/cubic foot, compared to 15 fibers/liter in the
Base condition. If a test magnitude effect exists, participants should have rated the same
actual exposure as riskier in the High Test Magnitude condition than in the Base condition.
The fourth condition, High Risk, served as a benchmark for assessing the size of the
locational and test magnitude effects. In addition, it provided an important test of the
extent to which subjects are responsive to objective risk data when such cues as the position
on the page and the numerical size of the test result are held constant. The High Risk
condition had only one change from the Base condition. The exposure ladder was ex-
pressed in fibers/deciliter rather than fibers/liter. Since the numbers were the same as in
the Base condition, the risk magnitudes were ten times as great Thus, the fourth condition
used a hypothetical test result of 15.0 f/dl — ten times the exposure level (and risk) of the
other three conditions. The position of this test result on a ladder ranging from 3.5 to 1500
f/dl was the same as the position of the Base scale reading of 15.0 f/1 on a ladder ranging
from 3.5 to 1500 f/1. If subjects responded appropriately to risk level, they should have
rated the risk as significantly higher in the High Risk condition than in the Base condition,
despite the absence of locational or numerical cues to the difference in risk.
Procedure. Participants were randomly assigned to one of the four format conditions
and mailed the appropriate test brochure format, an "imaginary11 asbestos test result, and a
feedback questionnaire.
Experiment III Methods
Appendix C contains the brochures, formats, and questionnaires used in Experiment
in. Tables 3 and 4 compare all five formats on a single page.
Design. The third experiment used a single-factor between-subjects design with five
levels of the treatment condition (format).
The first condition (Joint) presented radon and asbestos exposures and risk informa-
tion on the same page. The risk levels employed for the two hazards were different. The
asbestos test result assigned to all subjects in this condition was 25 f/1, equivalent to a risk
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TABLE 3
Experiment III Format Conditions
Format
Joint
Joint
Base Radon
Base
Asbestos
High Risk
Asbestos
Displaced
Asbestos
Hazard Test
Result
Magnitude
Asbestos 25
Radon 25
Radon 25
Asbestos 25
Asbestos 60
Asbestos 25
Test Result
Units
fibers/liter
picoCuries/
liter
picoCuries/
liter
fibers/liter
fibers/
deciliter
fibers/1 iter
Objective
Risk
(deaths/1000)
5
125
125
5
120
5
Location
on Page
Low
High
High
Low
High
High
43
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TABLE 4
Experiment III Formats
(X indicates position of test result on exposure ladder)
Joint Base Base High Risk Displaced
Radon Asbestos Asbestos Asbestos
Asbe<
25
;tos Rac
25
- X
ion Rac
- X 25
-
Ion Asbe<
- X
25
>tos Asbes
60
- X
;tos Asbe;
- X 25
-
;tos
- X
-
fibers/ picoCuries
liter liter
picoCuries/ fibers/
liter liter
fibers/ fibers/
deciliter liter
44
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45
of 5 deaths per 1000, while the radon test result was 25 pCi/1, equivalent to a risk of 125
deaths per 1000. The full range of the risks shown on the page extended from a minimum
of 1.5 deaths per 1000 to a maximum of 400 deaths per 1000. On this scale, the asbestos
test result appeared about one-fourth of the way up the ladder, while the radon test result
appeared about three-fourths of the way up the ladder. Thus, a physical distance between
the results of about half the length of the scale represented a 25-fold difference in risk.8
The second and third conditions'(called Base Radon and Base Asbestos, respective-
ly) were simply separate presentations of the same information presented jointly in the
Joint format. The Base Radon format presented the radon information, while the Base
Asbestos format had the asbestos informatiorL Location, test magnitude, and risk were all
unchanged from the simultaneous presentation condition.
The fourth condition (High Risk Asbestos) presented the asbestos hazard only, but •
with a risk level roughly equal to the radon risk in the Joint and Base Radon formats. The
scale for the High Risk Asbestos condition was manipulated so that the asbestos test result
appeared in the same location as the radon test result in the Joint and Base Radon
conditions, roughly three-quarters of the way up the page. The labels on the asbestos
exposure ladder in this format had the same numerical values as the labels on the asbestos
ladders in the Joint and Base Asbestos formats, but the unit of exposure was fibers/deciliter
instead of fibers/liter. This meant that the risks in the High Risk Asbestos format were ten
times higher than the corresponding risks in the Joint and Base Asbestos formats. The
hypothetical test result used in this condition was 60 f/dl. This yielded a risk level of 120
deaths per 1000, essentially the same as the radon risk in the Joint and Base Radon
formats.
Finally, the fifth condition (Displaced Asbestos) was a vertically shifted version of
the Base Asbestos scale. The scale was displaced so that the low asbestos risk of 5 deaths
8The Joint format was created in two forms, with radon levels first in one version and
asbestos levels first in the other. This variation had no effects on responses and will not
be discussed further.
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46
per 1000 associated with the 25 f/1 test result would appear physically on the scale in the
same position as the high radon and high asbestos test results, about three-fourths of the
way up the page.
Four comparisons were of primary interest, as follows.
• Comparison of the Joint, Base Radon, and Base Asbestos formats. This comparison
tests the first new hypothesis - that a simultaneous asbestos/radon risk ladder yields
stronger between-hazard differences than separate risk ladders for each hazard.
• Comparison of the Base Radon and High Risk Asbestos formats. This comparison
tests the second new hypothesis — that people respond differently to radon than to
asbestos even when risk and location on the page are held constant.9
• Comparison of the Base Asbestos and Displaced Asbestos formats. This comparison
retests the locational hypothesis — that when risk, test magnitude, and hazard (in this
case, asbestos) are held constant, people respond to locational cues about the
seriousness of the risk.
Comparison of the High Risk Asbestos and Displaced Asbestos formats. This compari-
son retests the risk hypothesis - that when location and hazard (asbestos) are held
constant, people respond to data about the size of the risk.10
As in Experiment n, care was taken to hold as many features of the formats constant
as possible. The features that were systematically varied are displayed in Table 3, p. 43.
Subjects. Subjects were 534 homeowners recruited from Middlesex County. A total
of 3,241 potential subjects were contacted; of these, 972 (30.0%) agreed to participate in
*Test magnitude varied between the two conditions, but only by a factor of 2.4.
Inasmuch as a much larger variation in test magnitude produced no effects in Experi-
ment n, the third experiment was interpreted as if test magnitude also had been held
constant.
10Once again test magnitude varied only by a factor of 2.4, and was considered
invariant. See the previous footnote.
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47
the study. Of those who agreed, 54.9% returned a completed questionnaire.11
Formats. The formats were as described above.
Feedback questionnaire. The feedback questionnaire from Experiments I and n was
modified somewhat. (See Appendix C for a copy of the Experiment III questionnaire.)
Several less crucial items were deleted or revised12 to accommodate five scales derived
from the work of Slovic, Fischhoff, and Lichtenstein (1985). These 7-point rating scales
assessed hazard dimensions that might account for differences in perceived risk between
asbestos and radon.
• Mitigation difficulty. The Slovic et al. version of the mitigation difficulty question
replaced the one used in previous studies. Choices ranged from 1 = very easy to
reduce to 7 = very difficult to reduce.
• Dread. This question assessed the degree to which people dread the negative health
consequences associated with radon or asbestos exposure. Choices ranged from 1 =
calm reaction to 7 = dread risk.
• Lethality. Subjects were asked how Likely they thought it was that illness resulting
from radon or asbestos exposure would be fatal. Choices ranged from 1 = certain
not to be fatal to 7 = certain to be fatal.
• Unfamiliarity. Subjects were asked whether radon or asbestos was a familiar risk or
a novel risk. Choices ranged from 1 = old to 7 = new.
uThe completion rate was somewhat lower than it had been in Experiments I and n.
Because of the extra effort required to read two brochures and complete two question-
naires in the Joint presentation condition, it appeared possible that the decline in the
completion rate was due to this condition. A breakdown of the Experiment III data
showed, however, that the return rate for the Joint condition was only marginally lower
than for the jeparate presentation conditions (513% and 55.9%, respectively).
12For example, two of the four original evaluation measures - amount of information
and uncertainty - were dropped.
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48
Natwalty occurring (vs. man-made). Choices ranged from 1 = all man-made to 7 =
all natural.
Procedure. Participants were randomly assigned to one of the five format conditions
and mailed the appropriate test brochure format, an "imaginary" radon or asbestos test
result (or both), and a feedback questionnaire.
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CHAPTER THREE
RESULTS
Results are presented in five parts. First, distributions of the demographic variables
and their associations with risk perception measures are given. Second, responses on the
audience evaluation variables are summarized. In the final three parts, the results of
principal interest, the analyses of treatment effects, are described separately for each
experiment.
The criterion level for statistical significance was set at .05 for all tests. The sample
sizes for the experiments were large enough" to permit adequate sensitivity. The statistical
power to detect the conventional "medium" effect size of a Vz standard deviation difference
between two means was .90 to .95 for most tests. The power to detect a "large" effect size
of a full standard deviation difference between two means was .99 or higher for most tests.
In other words, the experiments were quite sensitive to effects of meaningful sizes.13
Five risk perception measures were considered. The first and most sensitive was the
composite measure of perceived threat, the sum of four separate questions. The four other
risk-related variables were: intentions to mitigate; estimates of the numerical probability of
illness from the subjects' hypothetical test results; the perceived difficulty of mitigation; and
13See J. Cohen, Statistical power analysis for the behavioral sciences. 2nd ed.
Hillsdale, NJ: Lawrence Erlbaum, 1988.
49
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50
the highest exposure level at which subjects would feel satisfied. The last two questions
were not asked in Experiment III, leaving only three dependent variables.
Demographic Characteristics
Distributions of demographic variables. A total of 8,024 potential subjects were
contacted; of these, 2,431 agreed to participate and 1,418 completed and returned usable
questionnaires. Table 5 shows that the distributions of the three demographic variables
included in these experiments — age, education, and sex — were consistent across studies.
• Age. The mean age of subjects in Experiments I, n, and III ranged from 43.78 to
44.60 years.
• Educational level Subjects were quite well educated. Over 70% of the subjects
reported their educational levels as "some college" or higher, and more than 15% of
the total sample reported having a graduate degree.
• Sex, Women comprised roughly 52% of the sample.
Comparisons with 1980 census data for the municipalities from which the Phase Two
samples were drawn indicate that study participants were substantially better educated than
non-participants; 76.2% of subjects had some education beyond high school, compared to
27.0% of the census population. On age and sex, on the other hand, the sample and the
census population were well matched; 24.7% of subjects and 24.3% of the census popula-
tion were over 55, while 48.2% of subjects and 49.4% of the census population were male.
Relationships between demographic variables and response variables. The associa-
tions between the demographic variables and the perceived risk measures were tested by
regression analyses in which age, education, and sex were each examined separately and
treated as continuous variables. If the associations proved significant, the demographic
variables were included later as covariates when tests of format effects on the perceived
risk measures were carried out This use of covariates removes bias caused by random
differences in the distribution of demographic variables across conditions and improves the
sensitivity of the tests of treatment effects.
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TABLE 5
Distributions of Demographic Variables
Aqe
Under 20
20 - 29
30 - 39
40 - 49
50 - 59
60 - 69
70 - 79
80 - 89
Mean
SO
N
Educational Level
Some elementary school
Finished elementary school
Some high school
Finished high school
Some college
Finished 2-year college
Finished 4-year college
Some graduate study
Graduate degree
S.ex
Men
Women
I
Percent
1.7
10.7
29.4
27.7
14.1
11.7
4.6
0.0
44.04
13.25
407
Percent
0.0
0.7
2.2
23.7
21.0
6.3
23.7
6.1
16.3
Percent
50.1
49.9
Experiment
II
Percent
1.8
11.8
29.0
26.0
15.8
14.0
1.3
0.5
43.78
12.90
395
Percent
0.0
0.3
2.3
19.5
16.8
8.0
23.3
8.8
21.1
Percent
46.4
53.6
III
Percent
1.6
13.1
29.8
19.3
19.1
12.5
4.4
0.2
44.60
13.82
497
Percent
0.2
0.2
2.4
20.0
18.8
9.2
24.0
10.6
14.6
Percent
48.1
51.9
51
-------
52
None of the associations between a demographic variable and a response measure
was significant across all three experiments. Because the relationships between demograph-
ic variables and risk response variables were generally small and sometimes contradictory,
no effort was made to interpret these findings substantively. Table 6 summarizes the tests
of these associations and shows the direction of all relationships that proved significant (16
out of 39 tests).
Audience Evaluation
As expected, no significant format effects on perceived difficulty, helpfulness,
amount of information, or uncertainty were found in the three experiments, other than
would be expected by chance given the number of tests conducted. Consequently, Table 7
presents means and standard deviations on the audience evaluation questions for ail three
experiments but does not break down the results by format.
Brochure difficulty. Subjects found all the test brochures easy to read. The mean
difficulty ratings ranged from 3.51 to 3.54 across experiments. The value 3 represented
"fairly easy to understand" and the value 4 represented 'Very easy to understand."
Helpfulness of information. Subjects also found the brochures helpful. The mean
helpfulness ratings ranged from 3.19 to 3.51. The value 3 represented "moderately helpful
in understanding my test result" while the value 4 represented "very helpful in under-
standing my test result"
Amount of information in brochure. Subjects rated the amount of information
provided to be "about right" Mean ratings were 2.81 in Experiment I and 2.88 in Experi-
ment n on the five-point scale. The value 3 represented the choice "about right." Values
under 3 indicated insufficient information.
Uncertainty in understanding of risk. Subjects felt they had a good understanding of
the risk at their hypothetical test level. The mean rating for Experiment I was 1.86 on the
four-point scale. The mean rating for Experiment II was 1.68. The value 1 indicated "very
good understanding" and the value 2 indicated "good understanding."
-------
TABLE 6
Significance and Direction of Associations Between
Demographic Variables and Response Measures
Response Measure
Perceived Mitigation
Threat Intentions
Covariate
F/(df)
Direction F/(df) Direction
Illness
Probability
F/(df) Direction
Experiment I
Age
Educational
Level
Sex
5.86*
(1,358)
0.01
(1,358)
13.79**
(1,358)
4.82*
(1,395)
4.33* +
(1,395)
+ 0.01
(1,395)
2.02
(1,327)
2.23
(1,327)
7.45** +
(1,327)
Experiment II
Age
Educational
Level
Sex
4.45*
(1,355)
0.01
(1,355)
5.70*
(1,355)
14.83***
(1,360)
0.23
(1,360)
+ 3.90* +
(1,360)
0.56
(1,386)
1.69
(1,386)
1.04
(1,386)
Experiment III
Age
Educational
Level •
Sex
1.97
(1,562)
2.62
(1,562)
0.02
(1,562)
2.38
(1,576)
9.85** +
(1,576)
1.45
(1,576)
6.94**
(1,586)
26.23*** +
(1,586)
1.06
(1,586)
53
-------
Response Measure
Mitigation
Difficulty
Acceptable
Exposure Level
Covariate
F/(df) Direction F/(df) Direction
Experiment I
Age
Educational
Level
Sex
10.82**
(1,386)
3.66
(1,386)
0.10
(1,386)
2.24
(1,382)
0.95
(1,382)
5.72*
(1,382)
Age
Educational
Level
Sex
a < .05
a < .01
*** £ < .001
*
**
Experiment II
0.27
(1,352)
0.30
(1,352)
0.03
(1,352)
8.05**
(1,327)
0.25
(1,327)
4.70*
(1.327)
Mitigation difficulty and maximum acceptable exposure
level were not included in Experiment III.
A "+" indicates that as the covariate increases so does the response
measure. A "-" indicates an inverse relationship.
54
-------
TABLE 7
Audience Evaluation Variables
(Means and Standard Deviations)
Variable
Difficulty
Helpfulness
Mean
SD
N
Mean
SD
N
I
3.51
0.57
410
3.19
0.87
397
Experiment
II
3.54
0.53
399
3.51
0.67
386
III
3.54
0.56
593
3.46
0.68
578
Amount of Information
Uncertainty
Mean
SD
N
in Understanding
Mean
SD
N
2.81
0.54
395
Risk
1.86
0.78
411
2.88
0.42
390
1.68
0.63
400
-
-
The last two items were not asked in Experiment III,
55
-------
56
Format Effects on Risk Perception Variables: Experiment I
Experiment I examined the effects of the standard-only and standard + ladder formats
with four hypothetical asbestos levels. (See Appendix A for the two formats.) It was
hypothesized that the addition of a risk ladder would significantly reduce the perceived risk,
particularly at the two hypothetical asbestos levels above the guideline of 3.0 f/1. Analyses
of response measures were conducted using a 2 x 4 (format x level) design with appropriate
demographic variables as covariates. Results for the full design are presented first,
followed by a separate analysis for the high hazard levels (3.5 f/1 and 24.0 f/1).
Full design analysis. Results of the analysis for the five response variables are given
in Table 8.14 Table 9 presents means and standard deviations. The least-squares means
were adjusted for the particular covariates (age, educational level, and/or sex) that had
proved to be related to the response measure in question. Four risk perception variables.
showed significant relationships to the assigned asbestos level, but only one of the four (the
composite measure of perceived threat) showed a significant relationship to the format
manipulation. (The level x format interactions were all nonsignificant.)
• Composite measure of perceived threat. There was a strong effect of asbestos level on
the perceived threat, F(3,359) = 52.77, £ < .0001. The higher the hypothetical
asbestos level, the higher the composite risk index. The effect of format was also
significant, F(l,359) = 3.89, £ = .05. The mean composite risk rating for the stan-
dard-only format was 1432, compared to 13.46 for the standard + ladder format. The
format x level interaction was not significant, F(3,359) = 0.80, NS, indicating that the
effect of format was roughly consistent across assigned asbestos levels. These results
are apparent in Figure 1, which shows the relationship between the perceived threat
14As noted earlier, mitigation difficulty showed no significant effects in any experi-
ment; it is included in the tables but not discussed in the text.
-------
TABLE 8
Experiment I Analysis of Covariance of Response Measures
by Format and Hypothetical Exposure Level
Source
Format
Level
Format
Level
Source
Format
Level
Format
x Level
Perceived Threat Index
F/(df) Significance
Level
3.89 *
(1,359) (p * .05)
52.77 ****
(3,359)
x < 1 NS
(3,359) .
Mitigation Difficulty
F/(df) Significance
Level
< 1 NS
(1,396)
< 1 NS
(3,396)
2.12 NS
(3,396)
Response Measure
Mitigation Intentions
F/(df) Significance
Level
< 1 NS
(1,396)
20.97 ***
(3,396)
< 1 NS
(3,396)
Response Measure
Illness Probability
F/(df) Significance
Level
< 1 NS
(1,332)
27.98 ***
(3,332)
1.18 NS
(3,332)
Acceptable Exposure Level
fibers/liter8 1-12 scale
F/(df) Significance
Level
< 1 NS
(1,396)
4.79 **
(3,396)
< 1 NS
(3,396)
F/(df) Signif.
Level
< 1 NS
2.62 *
< 1 NS
Note: The demographic variables that proved significant in Table 6 were used in
these analyses as covariates.
"Calculations were based on log-transformed values.
NS £ > .05. * £ < .05. " 2 < .01. *" 2 < .001.
2 < .0001.
57
-------
TABLE 9
Experiment I Least-Squares Adjusted Means and Standard Deviations
by Format and Hypothetical Exposure Level
Format
Standard-Only
Standard+Ladder
Asbestos
Level
0.
2.
3.
24
8 f/1
Mean
SO
N
5 f/1
Mean
SD
N
5 f/1
Mean.
SO
N
.0 f/1
Mean
SD
N
Perceived Mitig. Illness
Threat Intentions Prob.
10.94
3.70
40
12.93
3.70
53
14.60
3.69
45
18.43
3.69
41
3.24
1.97
45
3.82
2.20
58
4.17
1.12
49
4.30
1.04
45
3.40
2.00
36
4.80
1.98
50
5.49
2.06
41
6.56
2.01
37
Perceived Mitig. Illness
Threat Intentions Prob.
10.18
3.69
46
13.10
3.69
50
13.34
3.69
48
17.23
3.69
46
3.06
1.14
51
3.83
1.11
55
3.97
1.10
54
4.43
1.12
49
3.58
2.01
45
4.91
1.89
49
4. -65
1.99
44
6.27
1.94
39
Format Means
Mean
SD
N
14.32
3.71
179
3.88
1.12
197
5.06
2.05
164
13.46
3.69
190
3.82
1.16
209
4.85
2.00
177
58
-------
Format
Standard-Only
Asbestos
Level
0.
2.
3.
24
8 f/1
Mean
SD
N
5 f/1
Mean
SD
N
5 f/1
Mean
SD
N
.0 f/1
Mean
SD
N
Mitigation
Difficulty
2.11
0.71
45
1.99
0.68
58
1.98
0.69
50
1.94
0.70
40
Acceptable3
Exposure Level
0.62
2.61
45
0.58
2.69
58
0.84
3.19
51
0.84
1.13
45
Standard+Ladder
Mitigation
Difficulty
1.85
0.70
51
1.86
0.70
55
2.11
0.69
52
2.14
0.70
48
Acceptable3
Exposure Level
0.61
2.22
51
0.64
2.80
55
0.61
2.83
52
1.05
3.32
48
Format Means
Mean
SD
N
2.01
0.70
199
0.71
3.30
197
2.00
0.71
208
0.78
2.75
206
'Analyses performed on log-transformed data.
logarithms.
Tables give inverse of mean of
59
-------
Figure 1
Experiment I
Effects on Perceived Threat of Adding a
Ladder of Exposure Levels to a Standard
"O 1=
o p
20 r
18-
16-
14-
w o
o ^ c
o 121
0) O)
Q- C
O
10-
0.
Risk (deaths per 1000)
10
k- Standard
-"- Standard
ladder
Standard
Phase I
60
-------
61
and asbestos level (expressed as mortality rates) for the standard-only and the stan-
dard + ladder formats.15
Mitigation intentions. There was a significant effect of asbestos level on intentions to
mitigate, F(3,396) = 20.97, p, < .001. At the high hypothetical asbestos level,
subjects experienced greater intentions to mitigate. The effect of format was not
significant, F( 1,396) = 0.31, NS, nor was there a significant format x level interac-
tion, F(3,396) = 0-57, NS.
Illness probability. The effect of asbestos level on the perceived likelihood of illness
was significant, F(3,332) = 27.98, £ < .001. At the high hypothetical asbestos level,
the perceived probability of illness resulting from exposure was higher than at the
low hypothetical asbestos level. The effect of format was not significant, F( 1,332) =
0.92, NS, nor was the format x level interaction significant, F(3,332)= 1.18, NS. As
Figure 2 shows, although level had a significant effect on illness probability esti-
mates, the effect was smaller than the tenfold increase in actual risk. Subjects in the
low-risk conditions estimated illness probability fairly accurately; those in the high-
risk conditions estimated too low.
Acceptable exposure level The mean of the maximum acceptable level was under 2
f/1 for all groups, well below the EPA guideline specified. Neither the effect of
format, F(l,396) = 0.06, NS, nor the format x level interaction, F(3,396)= 0.21, NS,
was significant. However, the hypothetical asbestos level did have a significant effect
on the highest level subjects would accept, F(3,396) = 2.62, £ = .05. Though the
15As seen in Figure 1, above the standard, perceptions of threat in the present
research were lower than the perceptions of threat of subjects who had been assigned to
the same format condition and asbestos levels in the Phase One research. The sharp
"step increase" above the standard present in Phase One was not apparent in this new
experiment. Further analysis showed a significant step in Phase One for the standard-
only condition, but not for the condition that included a standard plus risk probability
data and comparisons to smoking. In Phase Two, by contrast, no step was found for
either the standard-only or the standard + ladder condition. These differences have no
obvious explanations.
-------
Figure 2
Experiment II
Effects of Location, Test Magnitude, and Risk
Magnitude on Perceived Illness Probability
£ 9 . (D
!5
a
"o 7 (1 in 10)
a.
V)
a 5 (1 in 100)
c
•a
-------
63
differences were small, subjects assigned the high hypothetical asbestos level consid-
ered a higher level to be acceptable.
Analysis for high-exposure subjects. Responses for test result levels exceeding the
3.0 f/1 guideline were of particular interest because of the expectation that the greatest
effect of a ladder might be to calm people who were slightly or moderately above the
standard (see the Phase One data in Figure 1 (p. 60), indicating a sharp "step increase" in
perceived threat above the standard). For this reason, 2x2 (format x level) analyses were
conducted for the five response measures using only the 3.5 and 24.0 f/1 asbestos levels.
The results of the analyses of covariance are summarized in Table 10.
The results are not very different from those for the overall sample. The effect of
an exposure ladder on perceived threat was stronger in Table 10 than in Table 8, but the
format effects on the other four response variables were still nonsignificant.
In summary, the first experiment found that the addition of an exposure ladder had a
modest effect on the perceived threat, but no effect on mitigation intentions, estimates of
illness probability, estimates of mitigation difficulty, or acceptable exposure levels. Subjects
in the standard*ladder condition, in short, did see the asbestos risk as somewhat less
threatening than subjects in the standard-only condition, but the effect was small and was
significant only with the most reliable response measure. The effect on perceived threat
was somewhat stronger at high hypothetical asbestos levels than at lower levels, but the
format x level interaction was not statistically significant.
Format Effects on Risk Perception Variables: Experiment II
Because Experiment II focused on three primary hypotheses (concerning the effects
of location, the effects of test magnitude, and the effects of actual differences in risk) and
two secondary hypotheses (comparing the first two effects with the third), the results were
analyzed by means of planned comparisons, using Bonferroni's technique. Table 11
summarizes the results of these comparisons for the five response measures, and Table 12
presents least-squares adjusted means and standard deviations.
-------
TABLE 10
Experiment I Analysis of Covariance of Response Measures
by Format and Hypothetical Exposure Level
(High Hazard Levels Only)
Response Measure
Source
Format
Level
Format x
Level
Source
Format
Level
Format x
Level
Perceived Threat Index
F/(df) Significance
Level
5.75 *
(1,174) (p = .02)
54.98 ****
(1,174)
< 1 NS
(1,174)
Mitigation
F/(df)
2.25
(1,191)
< 1
(1,191)
< 1
(1,191)
Mitigation Intentions 111
F/(df) Signifi
Level
0.08 NS
(M91)
4.46 *
(1,191)
1.42 NS
(1,191)
Response
Difficulty
Significance
Level
NS
NS
NS
ness Probability
cance F/(df) Significance
Level
3
(1,
18
(1,
<
(1,
Measure
Acceptabl
F/(df)
< 1
(1,191)
< 1
(1,191)
< 1
(1,191)
.24 NS
156)
.28 ***
156)
1 NS
156)
e Exposure Level
Significance
Level
NS
NS
NS
Note: The demographic variables that proved significant in Table 6 were used in
these analyses as covariates.
NS £ > .05.
< .05.
a < .01.
a < .001.
< .0001.
64
-------
TABLE 11
Experiment II Analysis of Covariance of Format Effects
Comparison
Response Measures
Perceived Threat Mitigation
Index Intentions
F (df)/
Significance
F (df)/
Significance
Illness
Probability
Fldf)/
Significance
Overall Format Effect
F(3,356)-12.15 F(3,387)=5.19 F(3,368)=17.62
**** ** ****
Primary Hypotheses
Locational Effect:
Base vs. Displaced
**
NS
NS
Test Magnitude Effect:
Base vs. High Test Mag,
NS
NS
NS
High Risk Effect:
Base vs. High Risk
**
NS
***
Secondary Hypotheses
High Risk vs. Displaced
NS
NS
***
High Risk vs. High Test ***
Mag.
***
***
65
-------
Response Measures
Comparison
Mitigation
Difficulty
F (df)/
Significance
Acceptable Exposure Level
fibers/liter3 1-12 scale
F (df)/
Significance
F (df)/
Sianificance
Overall Format Effect
F(3,395)-0.98 F(3,384)«28.73 F(3,384)-.83
NS **** NS
Primary Hypotheses
Locational Effect:
Base vs. Displaced
NS
NS
NS
Test Magnitude Effect:
Base vs. High Test Mag,
NS
NS
NS
High Risk Effect;
Base vs. High Risk
NS
***
NS
Secondary Hypotheses
High Risk vs. Displaced
NS
***
NS
High Risk vs. High Test NS
Mag.
***
NS
Note: The demographic variables that proved significant in Table 6 were used in
these analyses as covariates. Comparisons of pairs of conditions were
conducted by use of Bonferroni's technique, with a significance criterion
that controlled for the three post-hoc tests of primary importance.
"Calculations were carried out on log-transformed values (with responses of 0
fibers receded as 0.075) because of the skewed distribution of responses and
non-1inear scale.
NS p_ > .05.
< .05.
< .01.
2 < .001.
< '.0001.
66
-------
TABLE 12
Experiment II Least-Squares Adjusted means
and Standard Deviations by Format
Response Measure
Format
Base
Mean
SD
N
Displaced
Mean
SD
N
Perceived
Threat
11.46
3.46
90
12.95
3.42
94
Mitigation
Intentions
3.57
1.19
98
3.68
1.21
101
Illness
Probability
3.63
1.53
92
3.89
1.56
95
High Test Magnitude
Mean 10.58 3.29 3.67
SD 3.43 1.19 1.53
N 93 99 93
High Risk
Mean 13.24 3.95 5.08
SD 3.43. 1.17 1.53
N 85 95 92
67
-------
Response Measure
Mitigation Acceptable Exposure Level
Format Difficulty fibers/liter3 1-12 scale
Base
Displ
High
High
Mean
SD
N
aced
Mean
SD
N
Test Magnitude
Mean
SD
N
Risk
Mean
SD
N
1
0
2
0
2
0
2
0
.93
.71
91
.04
.72
96
.08
.68
99
.04
.69
93
0.
8.
0.
5.
0.
8.
5.
6.
67b
33
90
51b
47
90
70C
33
86
j
Old
11
91
3
2
3
2
'
3
2
3
2
.90
.81
90
.62
.26
90
.92
.88
86
.67
.48
91
aCalculations were performed on log-transformed data. The value listed for each
condition is the inverse of the mean of the logarithm.
Response choices in units of f/1.
Response choices in units of f/cubic ft.
dResponse choices in units of f/dl.
68
-------
69
See Appendix B for the formats being compared, or Table 2 (p. 39), which shows
them schematically on the same page.
Test of the locational hypothesis. The Base and Displaced conditions differed only
in the placement of the test result on the page. A location high on the page increased
perceptions of threat above those elicited by the Base condition (12.95 vs. 11.46, £ < .01).
The effect of displacement on mitigation intentions, however, was not significant, though in
the same direction. This is probably attributable to the greater sensitivity of the composite
index, rather than to any difference in how perceptions and intentions are affected by
location on the risk ladder. As expected, given the equal risks in these two conditions,
illness probability ratings were not affected by displacement, nor were maximum acceptable
exposure levels.
Test of the test magnitude hypothesis. There were no significant differences between
the Base condition and the High Test Magnitude condition. Increasing the numerical size
of the test result by a factor of 30 made no difference, suggesting that subjects responded to
the risk information they had been given. This somewhat surprising finding is reassuring.
Concentration levels for radon in water, for. example, are typically higher than for radon in
air, although the waterborne risk is usually lower. It is encouraging that homeowners are
apparently able to disregard the misleading test magnitude cue, at least when mortality
information and smoking comparisons are also provided.
Test of the risk hypothesis. The High Risk condition was rated higher on the
perceived threat index than the Base condition (13.24 vs. 11.46, £ < .01), but these
conditions were not significantly different in mitigation intentions or maximum acceptable
exposure levels (measured on an equal-interval scale). As might be expected from the 10-
fold greater risk that was involved, illness probability estimates were significantly greater in
the High Risk condition (5.08 vs. 3.63, p. < .001).
Comparison of the locational and risk effects. There were no significant differences
in perceived threat or mitigation intentions between the Displaced and High-Risk condi-
tions. A 10-fold increase in risk was roughly equivalent to a displacement of half a page.
-------
70
Illness probability estimates were significantly higher in the High Risk condition (3.89 vs.
5.09, £ < .001).
Comparison of the test magnitude and risk effects. The High Risk condition was
associated with greater perceived threat than the High Test Magnitude condition (13.24 vs.
10.58, £ < .001), with greater interest in mitigation (3.95 vs. 3.25, jj < .001) and with
greater illness probability estimates (5.08 vs 3.67, £ < .001).
Accuracy of illness probability estimates. Since a correct answer to the question
about illness probabilities was provided in the brochures, the data were analyzed in terms
of the size of the discrepancy between subjects' choices and the illness probability indicated
by the brochure. For the Base, Displaced, and High Test Magnitude conditions, the
asbestos level assigned to subjects was equivalent to a risk of 3 deaths per 1000. The
closest choice on the logarithmic response scale was point "4," the point intermediate
between 1 in 1,000 (coded as "3") and 1 in 100 (coded as "5"). The assigned level in the
High Risk condition was equivalent to a "6" on this scale (3 in 100), intermediate between 1
in 100 (coded as "5") and 1 in 10 (coded as "7").
It is clear from Figure 2 (p. 62) that all the means tended to be low. The High Risk
mean was substantially below the correct answer (rj < .0001), and the Base and High Test
Magnitude results were also significantly below the correct answer (r/s < .05). The
difference in errors among conditions was also significant, F(3,368) = 4.60, £ < .005,
reflecting the greater underestimation of risk in the High Risk condition. Although risk
probability estimates increased as the actual risk increased, in other words, so did the extent
of the underestimation. This difference was not due to any difference in the difficulty of
finding a risk number near the test result on the brochure format page or finding the same
risk number in the illness probability question on the questionnaire; for all conditions, the
test result was one of the labeled points on the exposure ladder and the associated
mortality risk was given in the next column, while the correct answer on the questionnaire
required interpolation.
Acceptable exposure level. As seen in Table 12, the maximum level that subjects
-------
71
found acceptable was considerably less than that to which they were assigned. When
expressed in common units of f/1, the between-condition choices were significantly different,
F(3,384)= 6.91.J2 < .0001, reflecting the fact that the acceptable level in the High Risk
condition was greater than in the other conditions (g < .001). The remaining conditions
did not differ significantly.
Recall, however, that because several different units had been used, the question-
naire response options were not identical across conditions. For example, the High Risk
choices were expressed in f/dl instead of f/1. If the data are analyzed in terms of a simple
l-to-12 scale, referring to the 12 choices given but ignoring the labels that accompanied
each choice, the means do not vary significantly among the four format conditions, ranging
only from 3.62 (Displaced) to 3.92 (High Test Magnitude). These results suggest that in
choosing a maximum acceptable level, subjects picked a choice that was a few responses
away from the first option, zero, rather than seeking a particular level of risk. It is
interesting that the maximum acceptable level in the High Test Magnitude condition, where
choices were given in fibers per cubic feet (mean of 3.92, where 4 = 240 f/cu. ft.) was
nearly the same as the acceptable level in the Base condition, where the response options
reflected identical concentrations, but expressed in fibers per liter (mean of 3.90, where 4 =
8 f/1). This is further evidence that subjects were able to discount the numerical size of
their test result in making judgments about the risk.
To summarize Experiment n, variations in mortality statistics and smoking compari-
sons — that is, variations in actual risk — affected the composite index of perceived threat
and mitigation intentions. Illness probability estimates were also affected, but not as much
as they should have been to reflect the 10-fold risk difference between the Base and High
Risk conditions. The effects of risk variations on maximum acceptable exposure levels were
difficult to interpret because of differences among the response scales used in the four
conditions.
In contrast to the risk effect, vertical displacement had a significant effect only on
perceived threat, the most sensitive of the risk perception measures. The data thus show
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72
that subjects were responsive to risk information and somewhat affected by location.
The size of the test numbers had no effect according to any criterion. The data thus
provide no support whatsoever for a test magnitude effect. In fact, although the differences
were not significant, the High Test Magnitude format showed less risk aversion than the
Base format on several measures.
Figures 2, 3, and 4 show the results for the first three response variables in the form
of bar graphs, with confidence limits (twice the standard error of the mean) represented by
brackets at the tops of the bars. Although the between-format differences in mitigation
intentions were smaller and less significant than in the case of the composite threat
variable, the pattern of means, visible from Figures 3 and 4, is very similar for the two
variables.
Format Effects on Risk Perception Variables: Experiment III
Experiment III explored two new questions: the effects on perceived risk of simulta-
neously receiving both asbestos and radon risk information, as opposed to receiving the
identical information on only one hazard; and the effects on perceived risk of differences in
the hazard itself, independent of location, units of exposure magnitude, or risk level. In
addition, Experiment HI sought to replicate the locational and risk effects observed in
Experiment H.
A total of six presentation formats were used. See Appendix C for samples of the
six formats, or Table 4 (p. 44), which shows them schematically on the same page. Five
planned comparisons were analyzed. Table 13 summarizes the comparisons between condi-
tions.16'17 Table 14 presents the least-squares adjusted means and standard deviations.
16Only three response measures were used in Experiment III. Perceived mitigation
difficulty and maximum acceptable exposure level were dropped from the feedback
instrument.
17Tests of differences among means were conducted with Bonferroni's technique,
controlling for the five post-hoc tests of interest.
-------
Figure 3
Experiment II
Effects of Location, Test Magnitude,
Risk on Perceived Threat
ana
Base
Displaced
Experimental
High Test
Condition
High Risk
15 fibers/liter
3 deaths/1000
1 cigarette/day
low on poge
15 fibers/liter
3 deaths/1000
1 cigarette/day
high on page
450 fibers/cu ft
3 deaths/1000
1 cigarette/day
low on poge
15 fibers/deciliter
30 deaths/1000
1/2 pack/day
low on page
73
-------
Figure 4
Experiment II
Effects of Location, Test Magnitude, and
Risk Magnitude on Mitigation Intentions
definitely
would act
Mitigation ,
Intentions
definitely
would
not act
Base
Displaced High Test
Experimental Condition
15 fibers/liter
3 deaths/1000
1 cigarette/day
low on page
15 fibers/liter
3 deaths/1000
1 cigarette/day
high on page
450 fibers/cu ft
3 deaths/1000
1 cigarette/day
low on page
High Risk
15 fibers/deciliter
30 deaths/1000
1/2 pack/day
low on page
74
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TABLE 13
Experiment III Analysis of Covariance of Format Effects
Comparison
Response Measures
Perceived Threat Mitigation
Index Intentions
F (df)/
Significance
Illness
Probability
F (df)/
Significance
Significance
Overall Format Effect
F(5,573)=52.95 F(5,586)=16.79
**** ****
F(5,521)=32.15
****
Joint versus Separate
Presentations
Joint Asbestos
vs. Base Asbestos
Joint Radon
vs. Base Radon
NS
NS
NS
NS
NS
NS
Hazard Effect
Base Radon NS
vs. High Risk Asbestos
NS
NS
Locational Effect
Base Asbestos
vs. Displaced Asbestos
***
**
NS
Risk Effect
High Risk Asbestos
vs. Displaced Asbestos
***
**
***
Note: The demographic variables that proved significant in Table 6 were used
in these analyses as covariates. Comparisons between pairs of condi-
tions were conducted '..Uh Bonferroni's technique, controlling for the
five post-hoc tests of interest.
NS
> .05.
< .05.
< .01.
2 < .001.
2 < .0001
75
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TABLE 14
Experiment III Least-Squares Adjusted Means
and Standard Deviations by Format
Response Measure
Format
Joint Asbestos
Mean
SO
N
Joint Radon
Mean
SO
N
Perceived
Threat
12.43
3.71
96
16.83
3.71
93
Mitigation
Intentions
3.47
1.07
95
4.30
1.06
92
Illness
Probabil ity
6.39
2.43
87
10.14
2.44
82
Base Asbestos
Mean
SO
N
Base Radon
Mean
SD
N
High Risk Asbestos
Mean
SD
N
Displaced Asbestos
Mean
SD
N
11.58
3.71
96
17.56
3.71
96
17.97
3.72
105
14.28
3.71
93
3.32
1.11
102
4.19
1.08
96
4.22
1.04
108
3.79
1.08
96
6.19
2.50
100
10.15
2.40
79
10.53
2.45
96
6.82
2.37
90
76
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77
Figures 5, 6, and 7 compare the Experiment III formats on perceived threat, mitigation
intentions, and illness probability estimates.
Effects of joint versus separate presentation of hazards. No significant differences
were found for either radon or asbestos between the effects of presenting the two hazards
together and the effects of presenting them separately. (Recall that risk data on the two
hazards were provided, but not recommended action levels.) This was true for all three
response measures (the threat perception index, mitigation intentions, and illness probabili-
ty estimates). The hypothesis that information on one hazard would provide a context or
contrast that would influence perceptions of the risk from the other hazard was not
supported. (Of course it is possible that a different use of simultaneous presentations might
help owners take note of risk differences - for example, presentations that included the
different action levels for the two hazards, or presentations that directed readers' attention
to the differences more forcefully or interactively.)
Effects of hazard differences. There were no significant differences in subjects'
responses to radon and asbestos (holding location and risk constant, and test magnitude
nearly constant) on any of the three outcome measures. There may of course be significant
hazard differences for other hazards, but responses to radon and asbestos risks were not
affected by the identity of the hazard.
Retest of the locational hypothesis. Two of the Experiment III formats utilized the
same asbestos exposure level, expressed in the same units, varying only in the position on
the page. This retest of the locational hypothesis yielded similar but stronger results than
in Experiment IL For the threat perception index, the difference between the mean for the
Base Asbestos condition (11.58) and the mean for the Displaced Asbestos condition (14.28)
was significant at £ < .001, compared to a .01 confidence limit in Experiment II. In
addition, the effect of location on mitigation intentions, not statistically significant in
Experiment II, was large enough to achieve statistical significance in Experiment m (3.32
vs. 3.79, j2 < .01). These effects confirm the previous finding that a half-page vertical
displacement does indeed affect risk perceptions.
-------
Figure 5
Experiment III
Effects of Location, Risk, and Simultaneous
Presentation on Perceived Threat
Joint Base Separate Displaced High Risk/
Base Displaced
Experimental Condition
Joint Base
Separate
Base
Joint Base Asbestos: Joint presentation. 25 f/l, 5 deaths/1000, low on page.
Separate Base Asbestos: Separate presentation. 25 f/l. 5 deaths/1000, low on page.
Displaced Asbestos: Separate presentation. 25 f/l. 5 deaths/1000, high on page.
High Risk/Displaced Asbestos: Separate presentation, 60 f/dl, 120 deaths/1000, high on page.
Joint Base Radon: Simultaneous presentation. 25 pCt/l. 125 deaths/IOOO, high on page.
Separate Base Radon: Separate presentation. 25 pCI/l. 125 deaths/1000, high on page.
78
-------
definitely 5
would act
Mitigation
Intention
definitely
would !
not act
Figure 6
Experiment III
Effects of Location, Risk, and Joint
Presentation on Mitigation Intentions
Joint Base
Separate
Base
Displaced
High Risk/
Displaced
Joint Base
Separate
Base
Experimental Condition
Joint Base Asbestos: Simultaneous presentation, 25 f/l, 5 deaths/1000, low on page.
.Separate Base Asbestos: Separate presentation, 25 f/l, 5 deaths/1000, low on page.
Displaced Asbestos: Separate presentation, 25 f/l, 5 deaths/1000, high on page.
High Risk/Displaced Asbestos: Separate presentation, 60 f/dl, 120 deaths/1000, high on page.
Joint Base Radon: Simultaneous presentation, 25 pCt/l, 125 deaths/1000, high on page.
Separate Base Radon: Separate presentation, 25 pCi/l, 125 deaths/1000, high on page.
79
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13 (250 in 1000)
•=11 (80 in 1000)
O
_Q
2 9 (20 in 1000)
d.
8 7 (5 in 1000)
c
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81
As in Experiment n, no difference was expected between the illness probability
estimates of subjects in the Base Asbestos and Displaced Asbestos conditions, and none was
found.
Retest of the risk hypothesis. The High Risk Asbestos condition (with the test result
high on the page) yielded a significantly higher index of perceived threat than the Displaced
Asbestos condition (where the result was also high on the page) (17.97 vs. 14.28, £ < .001).
Similarly, the High Risk Asbestos condition yielded significantly greater intentions to
mitigate than the Displaced Asbestos condition (4.22 vs. 3.79, £ < .01). A similar differ-
ence was found for illness probability estimates (10.53 vs. 6.82, £ < .001). For all three
response measures, in short, the risk hypothesis was reconfirmed.
Taken together, Experiments II and III show that risk statistics (deaths per thousand)
plus smoking comparisons have an effect on risk perceptions regardless of whether the
location on the page is high or low.
Comparison of the locational and risk effects. In contrast to Experiment n, the
locational and risk effects could not be directly compared. Focusing on the most reliable
variable, the index of threat perceptions, however, one can see from Table 14 that the
effect of a half-page displacement was about 2.7 points on the scale, and that a further 24-
fold increase in risk added another 3.7 points. This is consistent with the Experiment II
conclusion that, in terms of impact on perceived risk, a half-page displacement was roughly
equal to a 10-fold change in actual risk.
Accuracy of illness probability estimates. The correct illness probability estimates,
treating the choices as a l-to-13 scale, were "7" for low-risk subjects and "12" for subjects in
the High Risk Asbestos and all radon conditions. As suggested by Figure 7, all the means
of subjects' ratings were underestimates, and except for the Displaced Asbestos condition,
all were significantly less than the correct choice, r/s < .05.
The errors were significantly different among conditions, F(5,525) = 5.83, £ < .0001.
The errors were especially large in the high-risk conditions, with rr°.an errors of 1.46 to 2.11
scale divisions. These results parallel those of Experiment II. Illness probability estimates
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82
increased significantly with increases in actual risk, but nearly all estimates were low, and
the si2e of the errors was greatest when the risk was highest.
Effects of perceived hazard characteristics. Experiment III included five measures of
hazard attributes whose effects on risk perceptions have been studied (Slovic, Fischhoff, &
Lichtenstein, 1985). These measures were included to help shed light on the hypothesized
hazard effect. As has already been reported, no such hazard effect emerged. That is, when
location on the page, test magnitude, and objective risk were all held constant, subjects did
not respond differently to asbestos than to radon on the three risk perception response
variables (the composite index of perceived threat, mitigation intentions, and estimates of
illness probability).
Nonetheless, subjects did perceive differences between radon and asbestos for three
of the five hazard characteristics. (The data used for this comparison come from the Base
Radon format and the High Risk Asbestos format. Both of these have the same location
on the page, the same test values, and the same risk information. Any differences found
are thus attributable to hazard alone.) Table 15 presents these comparisons. No significant
differences between radon and asbestos were found for dread, F(l,206) = 1.93, NS, or for
lethality, F( 1,205) = 2.28, NS. But significant differences were found between the two
hazards in subjects' judgments about the difficulty of mitigation, F( 1,206) = 13.61, D. < .001,
about unfamiliarity, F(l,205) = 9.22, £ < .01, and about naturalness, F( 1,206) = 110.70, £
< .0001. Subjects rated asbestos as being significantly more difficult to mitigate, older
(more familiar), and more a man-made hazard than radoru
Additional calculations examined the correlations between the five hazard attributes
and the three measures of perceived risk. Table 16 summarizes these analyses.18 Only
dread and lethality were significantly correlated with the response measures, with stronger
correlations for lethality. All significant correlations were in the expected direction; that is,
"Correlations were calculated separately for each hazard and then "averaged" using
Fisher's i-to-Z transformation.
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TABLE 15
Experiment III Radon and Asbestos Ratings on Five Characteristics
(Means, Standard Deviations, and Significance Tests)3
Hazard Characteristic
Difficulty of
Hazard Reduction
Mean
SD
N
Dread of Hazard
Consequences
Mean
SD
N
Hazard Lethality
Mean
SD
N
Unfamil iarity
Mean
SD
N
Natural Hazard
(vs. Man-Made)
Mean
SD
N
Format
Separate
Base Radon
3.23
1.46
99
3.55
1.64
99
5.69
1.25
98
3.97
2.05
98
5.85
1.51
99
Significance
High Risk F Significance
Asbestos Level
4.04 13.61 ***
1.64
109
3.87 1.93 NS
1.73
109
5.42 2.28 NS
1.34
109
3.15 9.22 **
1.85
109
2.39 110.70 ****
1.33
109
3Data from Base Radon scale and High Risk Asbestos scale.
NS 2 > .05. * a < .05. p_ < .01. *" fi < .001.
p_ < .0001
83
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TABLE 16
Experiment III Correlations of Hazard Ratings with Response Measures8
Hazard Characteristic
Difficulty of
Hazard Reduction
Correlation
Significance
N
Dread of Hazard
Consequences
Correlation
Significance
N
Hazard Lethality
Correlation
Significance
N
Unfamiliarity
Correlation
Significance
N
Natural Hazard
(vs. Man-Made)
Correlation
Significance
N
Perceived
Index
-0.09
NS
208
0.20
**
208
0.45
****
207
0.01
NS
207
0.08
NS
208
Response Measure
Threat Mitigation
Intentions
-0.12
NS
206
0.20
**
206
0.22
**
205
0.02
NS
205
0.06
NS
206
Illness
Probabil ity
-0.02
NS
179
0.10
NS
179
0.31
***
179
-0.02
NS
178
0.01
NS
179
aData from Base Radon scale and High-Risk Asbestos scale.
NS £ > .05. 2 < -05. fi < .01. *" p_ < .001,
< .0001
84
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85
higher ratings on dread and lethality were associated with higher ratings on the perceived
risk variables. These results replicate Slovic et al.'s (1985) finding that the dimension they
label dread (which includes ratings of both dread and lethality) influences risk perceptions,
but the dimension they label unfamiliarity does not. Variations in perceptions of lethality
affected illness probability estimates even though the information brochure provided explicit
data about illness probabilities.
The within-hazard and between-hazard results are entirely consistent. The three
hazard attributes that distinguished radon from asbestos were not correlated with risk
perceptions within a hazard condition; this is consistent with the absence of differences in
perceived riskiness between radon and asbestos. The two hazard attributes that were
correlated with risk perceptions within a hazard condition — dread and lethality — did not
lead to between-hazard differences in perceived risk because radon and asbestos were rated
the same on these two dimensions. Thus, although radon and asbestos are perceived
differently with respect to some hazard characteristics, these are not the characteristics that
are tied to perceived riskiness.
In summary, Experiment III found no evidence of any impact on risk perceptions of
joint versus separate presentations of radon and asbestos.19 Nor was there any evidence of
a hazard effect for these two substances. That is, when risk and location on the page were
held constant, subjects' risk perceptions for radon were not significantly different from their
risk perceptions for asbestos.20
As in Experiment n, a substantial risk effect was found. Subjects responded to
19This finding might be very different if other hazards were being compared. Radon
and asbestos are similar on many key dimensions, yielding no hazard effect in this
experiment. Perhaps with hazards that were more dissimilar - radon and nuclear waste,
for example — a joint presentation might yield risk perceptions that were different from
those generated by separate presentations.
^Of course a different finding might well result from the choice of hazards that differ
from each other more on those hazard characteristics that significantly affect risk
perception.
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86
higher levels of asbestos with higher risk perceptions, even when location on the page was
held constant
Again replicating the Experiment II findings, a significant locational effect also
emerged for the composite risk index and for mitigation intentions. When actual risk was
held constant, subjects responded to location on the page with significant alterations in risk
perception. The locational effect from a half-page displacement was about three-quarters
of the effect of a 24-fold difference in risk.
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CHAPTER FOUR
DISCUSSION
The overarching question examined by this research is the extent to which different
ways of presenting risk data - in this case, data about asbestos or radon — can help
individuals perceive their risk accurately and respond appropriately.
Dependent Variables
Five dependent variables were used. The most sensitive of these was the composite
index of threat perception, comprising four items that were strongly intercorrelated:
perceived likelihood of harmful effects, perceived seriousness, concern, and fear. The
composite index consistently showed the strongest relationships with experimental manipu-
lations; in no case did any manipulation achieve a higher level of significance for one of the
other dependent variables than for the composite index. This is not surprising. Not only
did the index have the reliability provided by four intercorrelated items; they were also the
items (perceived likelihood, perceived seriousness, emotional arousal) most likely to be
affected by variations in risk explanation.
A single question about mitigation intentions was treated as a second dependent
variable, in order to have a behavioral measure. It was expected that relationships with this
item would be weaker than with the composite threat perception index, not just because it
was a single itun but for two other reasons as well. First, behavioral measures are typically
87
-------
more resistant to influence than measures of attitudes or emotions. Second, this particular
behavioral measure was doubly contingent, twice-removed from subjects' real world: It
asked subjects to judge their own anticipated behavior (as opposed to measuring behavior
itself), and it did so under hypothetical assumptions.
The third dependent variable was subjects' estimates of illness probability. Except in
the first experiment, the experimental manipulations provided explicit data on illness
probability; this item was therefore conceptualized more as a comprehension check than as
a measure of risk perception. Estimates of illness probability should have been affected by
actual risk (since the illness probability information provided in the experimental manipula-
tions varied with the risk), but there was little reason to expect a significant effect from the
other treatments.
The last two dependent variables were judgments of mitigation difficulty and choices
of the highest asbestos or radon level subjects would find acceptable (that is, the highest
level at which they would choose not to mitigate). None of the experimental manipulations
addressed these two issues directly, and no impact was therefore predicted. They were
included in Experiments I and n to find out whether any of the experimental manipulations
would influence them indirectly, but were dropped from Experiment III to make room for
items on hazard differences.
The findings are discussed below in terms of the first two dependent variables, the
composite index of threat perception and mitigation intentions. The other three dependent
variables are discussed only when a significant relationship was found.
Findings
Six different factors were examined (in one or more of three experiments) to
determine their impact on subjects' risk perception: actual risk, the presence of a risk
ladder, location on the risk ladder, units of exposure magnitude, differences between two
hazards, and simultaneous presentation of two hazards. Care was taken to make sure each
factor was varied separately, with the others tightly controlled.
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89
Effects were found for the first three factors, but not for the second three. The
results will be discussed in the order in which the factors are listed. Three additional
findings are mentioned briefly at the end of the section.
1. The risk magnitude effect. Both Experiment II and Experiment III included a
test of the impact of actual risk on subjects' risk perceptions (risk was explained in terms of
excess cancer deaths and comparisons to smoking). In Experiment II, a 10-fold increase in
risk significantly increased the composite index of perceived threat. The effect on mitiga-
tion intentions was in the same direction, but did not meet the .05 significance criterion. In
Experiment III, a 24-fold increase in risk significantly increased both the composite index
and mitigation intentions. As predicted, estimates of illness probability were also increased
by actual risk in both experiments.
The finding that risk affects risk perception is not surprising. On the contrary, it
would be shocking if risk variations of an order of magnitude or more were invisible to
subjects instructed to make judgments about the extent of their risk. This is especially the
case in the relatively serious range of hypothetical risks to which subjects were assigned (3
and 30 deaths per thousand in Experiment H, 5 and 120 deaths per thousand in Experiment
HI). Comparable differences in deaths per billion might well have had negligible effects.
The finding of a significant risk effect should not be interpreted as meaning that
subjects had a thorough understanding of the risk data presented to them - much less that
they would act on that understanding. The only dependent variable with a "right answer"
was illness probability estimates. Subjects in all conditions tended to underestimate their
risk, and those in the high risk conditions underestimated it the most. That is, illness
probability estimates did increase as actual risk (that is, actual illness probability) increased,
but the gap of unrealistic optimism also increased with increasing risk.
2. The effect of a risk ladder. Experiment I tested the hypothesis that subjects
would perceive their risk to be greater when presented simply with a suggested "action
level" at which mitigation is recommended than when presented with such a standard
located midway up a risk ladder. Even though the ladder did not include risk data, the
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90
context it provided - the information that levels higher than one's own are not rare - was
expected to reassure subjects and thus reduce their perception of risk.
The hypothesis was confirmed, albeit weakly, for the composite index of perceived
threat, but not for mitigation intentions.
The finding that a risk ladder somewhat reduces risk aversion helps explain the
Phase One rinding that subjects were most risk-averse when presented simply with a
standard (as opposed to other treatments that provided risk data, risk comparisons, advice,
etc.). Apparently, people presented simply with two pieces of information, the recommend-
ed action standard and their own reading, are likely to interpret this information in
alarming ways. If their reading is above the standard, they have no way of knowing "how
far" above the standard it is or "how far" above the standard people's readings typically
range; even if their reading is below the standard, they seem to derive little reassurance
from that fact in the absence of some information on the range of possible readings.
The mere addition of a risk ladder tells them nothing about death rates at the differ-
ent levels, or even about the frequency with which these levels are encountered. But the
range of levels included on the ladder at least suggests the range of levels that experts must
expect people to encounter. This contextual information appears to reassure subjects
whether their assigned readings are above or below the action standard. It seems likely
that subjects assigned a level at or near the top of the ladder would be alarmed rather than
reassured by the ladder. This was not tested. All subjects in Experiment I learned from
the ladder that things could be worse, and they tended to find this additional context
reassuring.
The Phase One research found a sharp "step increase" in perceived threat above the
standard for subjects receiving the standard-only condition. (Subjects tended toward risk
aversion in this treatment regardless of their assigned level, but those assigned a level
above the standard were even more risk-averse.) 1 nis led to the hypothesis that the
reassuring effect of the risk ladder should be greatest for subjects with levels above the
standard (but not right at the top of the ladder). As expected, the effect of the manipula-
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91
tion on the composite index of perceived threat was stronger for levels above the standard.
But the difference was not sufficient to yield a significant format x level interaction, and
even for levels above the standard there was no significant effect of the risk ladder on
mitigation intentions.
The size of the risk ladder effect cannot be compared directly with the size of the
risk effect, since they were studied in different experiments. But indirect comparison is
possible. Averaged across all readings, the addition of a risk ladder decreased the compos-
ite threat perception index by 0.86 units on a 19-unit scale (4.5% of the total scale range);
above the standard, the decrease averaged 1.23 units (6.5%). In Experiment II, the effect
of a 10-fold difference in risk was 1.78 units (9.4%); in Experiment III, a 24-fold difference
in risk yielded an average difference in perceived threat of 3.69 units (19.4%). Even above
the standard, then, the presence or absence of a risk ladder had less effect on perceived
risk than one order of magnitude in actual risk.
Still, the effect was large enough to be of practical value. If the communicator's goal
is maximum risk aversion - that is, if the hazard is serious and the audience is inclined
toward apathy — a standard without additional information is ideal; its very ambiguity
generates the desired risk-averse response. If panic is a problem and the goal is to provide
reassuring context, on the other hand, a risk ladder is worth adding. Note that no addition-
al information is required to add a ladder. Even when data are unavailable on deaths per
thousand or on the distribution of readings, a risk ladder can always be added to an action
standard when a less risk-averse response is desired.
3. The effect of location on the risk ladder. The locational hypothesis was intro-
duced at the end of Phase One to account for that study's finding that many formats were
able to help subjects distinguish the effects of high versus low levels of asbestos or radon,
but no format successfully helped subjects distinguish the effects of asbestos from the effects
of radon. The risk associated with a particular level of asbestos or radon, it was noted, was
proportional to that level's location on the risk ladder (higher risks were higher on the
ladder), while the difference in risk between asbestos and radon was not reflected in their
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92
respective ladders. If subjects were responding to location on the ladder rather than to risk
information, therefore, their risk perceptions would be sensitive to within-hazard differences
but not to between-hazard differences - exactly what the Phase One data had shown.
The locational hypothesis was tested in Experiments II and IE. By displacing the
risk ladder, the same hypothetical reading with the same risk information was located either
one-quarter of the way up the ladder or three-quarters of the way up the ladder. Both
experiments found a significant locational effect on the composite index of perceived threat.
In Experiment n, a displacement of half a page led to a 1.49-unit effect on the 19-unit
threat perception index (7.8% of the total scale range), while a 10-fold difference in actual
risk produced an effect of 1.78 units (9.4%). (This small difference between the two effects
was not statistically significant.) In Experiment III, a displacement of half a page yielded a
difference of 2.70 units (14.2%) in the composite index of perceived risk, while a 24-fold
risk difference added another 3.69 units (19.4%). The findings with respect to mitigation
intentions were less compelling. In Experiment III, the effect on mitigation intentions was
statistically significant, but in Experiment II it was too small to achieve statistical signifi-
cance. This failure to find a mitigation effect in Experiment II is probably a result of the
insensitivity of the single-item measure of mitigation intentions, not an indication that
location on the risk ladder affects perceptions more than intended behavior.
The effect of location on risk perception is a sizable effect and an important finding.
(It is not really a surprising rinding, however. Virtually every primer on graphical presenta-
tion of data stresses that graphs can be truncated, extended, or displaced in order to
exaggerate or minimize the effect displayed. See for example Huff, 1954.) Risk informa-
tion developed to guide laypeople is often arrayed on a risk ladder, and the structure of the
ladder is frequently determined more or less arbitrarily. How low should the ladder begin?
How high should it rise? Should the scale be linear or logarithmic? The answers to these
questions are not obvious. They depend not just on the seriousness of the risk and the
anticipated apathy or panic of the audience, but also on the actual range of levels that are
typically encountered and on the ethical values of those constructing the ladder. What is
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93
clear from the data is that people's risk perceptions can be meaningfully altered - whether
intentionally or arbitrarily - by constructing the ladder so that their risk appears low or
high on the page.
4. The effect of test magnitude. In the Phase One research, radon exposures were
expressed in picoCuries per liter, while asbestos exposures were in fibers per liter. The risk
associated with a level of radon with the same numerical exposure magnitude was substan-
tially higher than the risk associated with that level of asbestos; that is, X pCi/1 of radon
constitutes a greater risk than X f/1 of asbestos. This suggested another possible explana-
tion for the Phase One finding about within-hazard versus between-hazard differences.
Perhaps subjects responded appropriately to differences in level within a hazard because
the exposure numbers themselves varied with the risk, while failing to respond to between-
hazard risk differences because the numbers were not substantially different.
This hypothesis was tested in Experiment II. By expressing asbestos risk alternatively
in fibers per liter and in fibers per cubic foot, a 30-fold difference in test magnitude was
achieved without any difference in risk.
No significant effects were found. In fact, the composite index of perceived threat
and the measure of mitigation intentions were actually somewhat lower — though not
significantly so — in the High Test Magnitude condition than in the Base condition. The
evidence is convincing that the numerical magnitude of test numbers does not influence
perceived risk.21
This somewhat surprising finding is reassuring. Concentration levels for radon in
water, for example, are typically higher than for radon in air, although the waterborne risk
is usually lower. It is encouraging that homeowners are apparently able to disregard the
21This finding may not be applicable in cases where the actual risk is lower and the
numbers used are higher and less familiar. Some risk communication practitioners claim
that audiences can be more concerned about nne part per billion than one part per
million, mistakenly interpreting the larger denominator as a larger risk. No research has
compared the risk perception effects of, say, risk probabilities of one-in-a-million versus
one-in-a-billion versus one-thousand-in-a-balion.
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94
misleading test magnitude cue, at least when mortality information and smoking compari-
sons are also provided. A study to determine whether subjects can appropriately rank the
risks from air and water radon readings would be a useful follow-up.
5. The effect of hazard differences. A third possible explanation was also consid-
ered for the Phase One finding that subjects were more sensitive to within-hazard risk
differences than to between-hazard risk differences. Perhaps there were particular
characteristics of the two hazards, asbestos and radon, that made the former more alarming
to subjects than the latter, thus tending to cancel out the effects of the fact that the latter
was the greater risk (at the levels specified). It is not speculation, but established fact, that
some hazards tend to generate more public concern, risk aversion, and perceived high risk
than other risks; a substantial psychometric research literature has explored both the
differences in risk perception among particular hazards and the hazard characteristics that.
account for those differences (see for example Slovic, Fischhoff, and Lichtenstein, 1985).
Experiment in tested for risk perception differences between radon and asbestos. In
anticipation of finding some differences, Experiment En also added measures of five hazard
characteristics: difficulty of reducing the risk, dread, lethality, unfamiliarity, and the
natural/man-made distinction.
Surprisingly, no differences were found between radon and asbestos in the composite
threat perception index or in mitigation intentions, when risk level and location on the page
were held constant. Of the five hazard characteristics measured, three — difficulty of
reducing the risk, unfamiliarity, and natural/man-made — showed significant differences
between radon and asbestos; radon was seen as easier to mitigate, less familiar, and less
man-made than asbestos. None of these three hazard characteristics was significantly
correlated with the dependent variables. By contrast, the two characteristics — dread and
lethality — that were significantly correlated with perceived risk did not significantly distin-
guish radon from asbestos.
These results are internally consistent, and consistent with the findings in Slovic,
Fischhoff, and Lichtenstein, 1985. Radon and asbestos, apparently, do not differ substan-
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95
tially in those hazard characteristics that affect risk perception. For two other hazards that
did differ substantially in the hazard characteristics that affect risk perception, a significant
hazard effect on risk perception would be expected. Radon and nuclear waste, for example,
probably differ in the amount of dread they trigger; dread, in turn, significantly affects risk
perception, both in the present study and in the literature. Holding actual risk, location on
the page, and other factors constant, one would expect to find a difference in perceived risk
between radon and nuclear waste facilities.
6. The effect of simultaneous presentation. The final factor tested in the Phase Two
research was the possibility that the simultaneous presentation of asbestos and radon risks
on two parallel ladders — in effect, on the same ladder — might help subjects understand
that the asbestos risk was much less serious than the radon risk. This was tested in
Experiment Ed, and the hypothesis was rejected. There were no significant differences
between the joint and separate presentations for either radon or asbestos. Of course it is
possible that a different use of simultaneous presentations might help owners take note of
risk differences - for example, presentations that included the different action levels for the
two hazards, or presentations that directed readers' attention to the differences more
forcefully or interactively.
As the previous section detailed, subjects' risk perceptions of radon and asbestos
were not significantly different Perhaps for two hazards that did vary in perceived risk -
radon and nuclear waste, for example — simultaneous presentation might have an impact
(as opposed to separate presentations). This remains to be tested.
It should be noted that the simultaneous presentation hypothesis was very narrowly
framed in the present study. That is, location on the risk ladder was held constant; whether
the two hazards were presented simultaneously or separately, the asbestos risk was always
one-quarter of the way up the ladder, and the radon risk was always three-quarters of the
way up the ladder. In many practical applications, by.contrast, presenting two hazards
simultaneously would mean extending the risk ladder upwards and downwards to encompass
the range of risks entailed by the two different hazards. Since the normal range of asbestos
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96
hazards is lower in risk than the normal range of radon hazards, a joint presentation as
opposed to separate presentations would tend to move asbestos readings further down on
the page and radon readings further up. The locational effect would thus yield decreased
asbestos risk perceptions and increased radon risk perceptions - even if there were no
added effect of simultaneity.
To put this another way, the findings that have been discussed so far strongly support
the locational explanation for the Phase One result that subjects are much better able to
distinguish within-hazard risk differences than between-hazard risk differences, at least
insofar as asbestos and radon are concerned. Phase One subjects had trouble recognizing
that radon was a more serious risk than asbestos, the Phase Two results strongly suggest,
not because they were misled by differences between the two hazards or by similarities in
the numerical values of the test numbers, but because radon and asbestos were each
presented on a separate risk ladder that encompassed a limited range of risks. On a
"composite" risk ladder that ran from the lowest level of the asbestos ladder to the highest
level of the radon ladder, the findings suggest, asbestos risk perceptions would be dimin-
ished and radon risk perceptions would be augmented.
It may be productive to envision a "composite" risk ladder embracing a still wider
range of hazards — one that can cover very low probability risks (pedestrian is hit by
lightning) at the bottom of the ladder and very high probability risks (smoker gets lung
cancer) at the top. If such a ladder can be devised in a way that is comprehensible to lay-
people (it would have to be logarithmic, certainly), it should excel at helping people
perceive between-hazard differences. But within-hazard differences are typically much
smaller; they would be compressed into a small portion of this expanded ladder. Inevitably,
therefore, the composite ladder would be much less successful than narrower single-hazard
ladders at pointing to within-hazard differences.
7. Three other findings. Three other findings of interest concern demographics,
estimates of illness probability, and maximum acceptable levels.
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97
• Older subjects tended to be less risk-averse than younger subjects; less educated
subjects tended to be less risk-averse than more educated subjects; men tended to be
less risk-averse than women. However, none of the associations between a demo-
graphic variable and a risk perception variable was significant for all three experi-
ments.
• As mentioned earlier, subjects were consistently low in their estimates of illness
probability, even though the information called for in the questionnaires was
provided in the brochures. Although risk probability estimates increased as the
actual risk increased, so did the extent of the underestimation.
• Subjects' judgments of the highest exposure level they would consider acceptable
varied depending on the options provided; when responses were convened into a
simple 1-12 scale independent of the options provided, no significant differences •
were found. This suggests that subjects did not choose a particular level of risk in
response to the question, but rather selected a choice that was a few responses away
from the first option, zero. In essence, they chose a location, not a risk. The highest
acceptable levels were usually significantly lower than the action guideline provided.
Format Findings, Risk Communication Criteria, and Ethics
To determine how to use findings such as those discussed here, it is necessary first to
establish criteria for successful risk communication. As was noted at the start of this report,
the entire focus of this research has been on ways of explaining risk magnitudes more effec-
tively — that is, ways to help people understand the size of their risk. The research whose
second phase is reported here represents the most sustained effort to date to find out how
far cognitive explanation can bring us: how much risk response can be shaped by effectively
presented data alone.
The dependent variable that proved most sensitive throughout 'he study, the
composite index of perceived threat, was an amalgam of cognitive factors (perceived
seriousness, perceived likelihood) and affective ones (concern, fear) - but the manipula-
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98
tions tested were exclusively cognitive. A more controversial class of risk communication
strategies involves efforts to influence risk responses through appeals to emotion or direct
manipulations of behavior: dramatic fear appeals, social pressure, rewards for compliance,
etc. Considerable research demonstrates that these non-cognitive approaches can be very
effective - but they raise serious ethical dilemmas for many risk communicators.
Some would object on ethical grounds even to the manipulations studied here. Of the
three factors that proved to have impacts in this study — risk itself, the presence of a risk
ladder, and location on the ladder - only the first is unexceptionable. To include or
exclude a risk ladder in order to diminish or exacerbate people's concerns, or to extend or
truncate or displace the ladder for the same reason, is in the judgment of some observers to
leave the domain of risk education and enter that of risk propaganda. Of course one must
either include or exclude a ladder, and if there is a ladder the end points must be set
somehow. But some would prefer to make these decisions without considering the (now
readily predictable) impact of such decisions on the risk judgments of the audience.
For those who do not find these ethical issues troublesome, practical problems
remain. To determine whether one wishes to dampen or augment an audience's level of
risk perception, one must have some expectations about what level of risk perception is
likely to be encountered, and some beliefs about what level is appropriate. Some hazards
are underestimated or overestimated by nearly everyone, so the task is to alert or to
reassure across-the-board. The absence of a risk ladder appears to alert across-the-board;
its presence appears to reassure. For other risks, however, the task may be to alert those
who are particularly inclined toward apathy and to reassure those who are particularly
inclined toward panic. Nothing in the Phase Two research suggests an approach that
discriminates among audiences in this way.
Most commonly, risk communicators seek a strategy that will tend to alert those who
are being exposed to relatively high levels of the hazard in question, while reassuring those
whose exposure is relatively low. Certainly for a hazard like radon or asbestos, the ideal
communication approach would generate increased perceptions of threat and increased
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99
intentions to mitigate among those whose readings were high and decreased perceived
threat and intentions to mitigate among those whose reading were low. The Phase One
research found that an action guideline could accomplish this goal. The Phase Two
research suggests that another promising approach is to truncate the risk ladder at both
ends. A radon ladder that runs from 2 to 40 pCi/1, for example, should be simultaneously
more calming to a homeowner with a 2.5 pCi/1 reading and more alarming to a homeowner
with 35 pCi/1 than one that runs from 0.2 to 400.
But to focus on one hazard at a time misses the key finding of the Phase One
research. Several communication formats do a fairly decent job of helping people distin-
guish 2.5 pCi/1 of radon from 35 pCi/1 of radon (though some formats do better than
others). The more intractable problem is to help people distinguish 2.5 pCi/1 of radon
from the much less serious risk of 2.5 f/1 of asbestos. The locational effect can be har-
nessed to this task as well. By extending the risk ladder in both directions, so that it runs
down to the lower levels of asbestos risks and up to the higher levels of radon risks, the
communicator can assure that all but the highest asbestos risks wih1 be near the bottom of
the ladder (and therefore a source of calm), while all but the lowest radon risks will be
near the top (and therefore a source of alarm).
The problem here is obvious. The strategy that helps people see the difference
between radon and asbestos obscures the difference between high and low levels of one
hazard. The strategy that helps people see the difference between high and low levels
obscures the difference between radon and asbestos. There may of course be a strategy
that accomplishes both, but it has yet to be found. To select among the strategies that have
been found, one must know what one wants to accomplish, and must accept that other goals
may be disadvantaged in the process.
Next Steps
What have we learned from the first two phases that guides us in trying to explain
risk magnitudes? We have learned that the task is not impossible. When risk magnitude
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100
data are presented, higher risks do generate higher perceived threat and mitigation
intentions than lower risks. We have also identified four factors other than risk magnitude
data that significantly affect risk perception: action standards and explicit advice (from
Phase One), the presence of a risk ladder and location on the ladder (from Phase Two).
Finally, we have learned that all of these effects are relatively small; studying them reliably
requires sizable samples of study participants and sensitive response measures.
Several questions remain unanswered. The role of risk comparisons was explored in
the first budget period; the results suggested that comparisons to smoking risk had only
modest benefits. Considerable anecdotal evidence about the utility of risk comparisons
suggests that this question should be investigated further, this time perhaps without the
presence of a risk ladder and certainly without the presence of a standard.
Another variable not explored in this research so far is the use of graphic represen-
tations of probability or concentration data. The first EPA Citizen's Guide to Radon made
considerable — and controversial — use of matrix of faces and crosses to show mortality
probabilities. A more recent EPA report, Hazardous Substances in Our Environment: A
Citizen's Guide to Understanding Health Risks and Reducing Exposure (EPA 230/
0990081), used a similar matrix. One published study (Kaplan, Hammel, and Schimmel,
1985) suggests that this graphic approach may help to lower anxiety about low-probability
risks. It is not at all clear what the effects of such graphical approaches are with larger
probabilities.
In addition to exploring these issues, it would be useful to determine the effective-
ness of a "maximum impact" treatment that takes advantage of what has been learned so far
about standards, advice, risk ladders, etc.
Considerable emphasis has been put in this discussion section on the likelihood that
very different strategies may be required for helping people see that a small risk is small
than for helping people see that a large risk is large. (Advice, for example, appears to be
much better at the former than the latter.) Moreover, the policy implications of these two
types of risk communication are very different. In the past several years, for example, the
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101
Environmental Protection Agency has devoted considerable effort to exploring the discrep-
ancies between expert and public assessments of risk and to developing policies that take
cognizance of these different assessments. The need to become more skilled at explaining
serious risks is grounded in public health and similar concerns; lives are at stake when an
agency tries to warn people about serious risks. When people persist in worrying dispropor-
tionately about minuscule risks, on the other hand, the costs range from unnecessary anxiety
to misused environmental protection dollars, from public policy gridlock to reduced agency
credibility.
The Phase One and Phase Two research focused on two hazards, radon and
asbestos. At the levels used in the research, both pose relatively serious risks. Radon and
asbestos are not identical hazards, of course. But on the variables that best predict whether
a hazard will provoke underreaction or overreaction from the public — dread, control, trust,
fairness, etc. - they are similar. (As noted earlier, significant risk perception differences .
between the two hazards were not found.) In the language of "hazard versus outrage"
(Sandman, Klotz, and Weinstein, 1987), the research so far has focused on risks that were
moderate to high in hazard and low in outrage. Future research should look explicitly at a
high-hazard, low-outrage risk to which the public typically underresponds and a low-hazard,
high-outrage risk to which the public typically overresponds - for example, radon and low-
level radioactive waste facilities.
Finally, it must not be forgotten that all the research so far has made use of
hypothetical "assigned" exposure levels. The efficiency and ethical preferability of this
method are clear. But the time is approaching when the findings from this research must
be confirmed with citizens' actual exposure levels.
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REFERENCES
Doyle, J., McClelland, G., Schultze, W., Elliott, S., and Russell, G. (1991). Protective
responses to household risk: A case study of radon mitigation. Risk analysis. II: 1,
121-134.
Huff, D. (1954). How to lie with statistics. New York: Norton.
Kaplan, R., Harnmel, B., & Schimmel, L (1985). Patient information processing and the .
decision to accept treatment. Journal of social behavior and personality, 1. 113-120.
National Research Council (1989). Improving risk communication. Washington, DC-
National Academy Press.
Rohrmann, B. (1990). Analyzing and evaluating the effectiveness of risk communication
programs. Studies on risk communication (Volume 17). Julich, Germany: Pro-
grammgruppe Mensch-Umwelt-Technik (Mut) Des Forschungszentrums Julich.
Sandman, P., Klotz, M., & Weinstein, N. (1987). Public response to the risk from geologi-
cal radon. Journal of Communication. 37. 93-108.
Slovic, P., Fischhoff, B., & Lichtenstein, S. (1985). Characteristics of perceived risk. In J.
Kasperson, C. Hohenemser, & R. Kates (Eds.), Perilous progress: Managing the
hazards of technology (pp. 99-123). Boulder, CO: Westview.
Smith, V.K., Desvousges, W.H., Fisher, A., amd Johnson, F.R. (1987). Communicating
radon risk effectively: A mid-course evaluation. Washington, DC: Office of Policy,
Planning, and Evaluation, U.S. Environmental Protection Agency (EPA-230-07-87-
029).
103
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Weinstein, N., and Sandman, P. (1991). Predicting homeowner mitigation responses to
radon test data. Unpublished manuscript (available from the Environmental
Communication Research Program, Cook College, Rutgers University, New Bruns-
wick, NJ 08903).
Weinstein, N., Sandman, P., and Roberts, N. (1989). Communicating Effectively about Risk
Magnitudes. New Brunswick, NJ: Environmental Communication Research Pro-
gram, Cook College, Rutgers University.
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APPENDIX A
EXPERIMENT I BROCHURES, FORMATS, AND QUESTIONNAIRES
Experiment I had two conditions, standard-only and standard-Madder, for asbestos only.
The Appendix includes the full three-page standard-only brochure with the format on the
third page, followed by the last two pages of the four-page standard*ladder brochure with
the format on the fourth page (the first two pages were identical). The cover letter and
questionnaire are at the end of the Appendix.
105
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EXPERIMENT I
STANDARD - ONLY BROCHURE
Test Brochure*
4/&8
BASIC ASBESTOS INFORMATION
WHAT IS ASBESTOS?
Asbestos is a mineral fiber found in rocks. There are several
kinds of asbestos fibers, all of which are fire-resistant and not easily
destroyed by natural processes. Because of its desirable qualities,
asbestos has been used in a wide variety of products including
appliances, ceilings, wall and pipe coverings, floor tiles, and some
roofing materials.
WHY THE CONCERN ABOUT ASBESTOS?
Although asbestos has many benefits for humans, it is also a
very dangerous mineral. Breathing airborne asbestos fibers has
been shown to cause: (1) Asbestosis • a serious lung disease which
can lead to disability and death; (2) Lung cancer - a disease that is
incurable and almost always fatal; and (3) Mesothelioma - cancer of
the lining of the lungs or abdominal cavities. The greater the
exposure to asbestos, the more likely it is that one of these serious
diseases will develop. Workers who handle or come into contact
with asbestos on a daily basis are open to the greatest health risks.
There is no level of exposure to asbestos fibers that is
completely safe. The greater the concentration of asbestos, the
greater the risk.
HOW DOES ASBESTOS AFFECT US?
The danger arises when asbestos fibers are released from the
product or material. These fibers are so small that they cannot be
seen. They can float in the air for a long time and can pass through
the filters of normal vacuum cleaners and get back into the air.
Once inhaled, asbestos fibers can become lodged in tissue for a long
time. After many years cancer or asbestosis can develop.
Cigarette smoking and asbestos together are especially
hazardous. Exposure to asbestos plus smoking gives an even greater
risk: of lung cancer than adding the risk from smoking alone to the
risk from exposure to asbestos alone.
Asbestos found in "friable" materials is most dangerous. Friable
materials are materials that can be crumbled, pulverized, or reduced
to powder by hand pressure. Asbestos insulation sprayed on a
ceiling is an example of a friable material. In contrast, vinyl
1 Because this is an experimental brochure, please check with other authorities
before taking any action in your home.
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asbestos floor tile is not usually friable. The asbestos fibers are
firmly bound or sealed into the tile and can be released into the air
only if the tile is cut, ground, or sanded.
WHERE IS ASBESTOS LIKELY TO BE FOUND IN THE HOME?
There are several areas in the home where asbestos problems
are most likely to arise. These include:
* Wall construction material and pipe"insulation,
especially those dating between 1920 and 1972.
(This includes materials found in and behind plaster
or wallboard and in paper tape.)
* Friable ceilings in buildings built or remodeled
between 1945 and 1978.
* Material found in stoves and furnaces such as
insulation and millboard and door gaskets.
Other asbestos-containing products that you may find in the home
include:
* Patching compounds and textured paints. (Since
the use of asbestos was banned in 1975, you are
most likely to find it when sanding or scraping old
or damaged material in older houses.)
* Vinyl floor tiles and flooring.
* Roofing, shingles, and siding.
* Appliances with asbestos-containing parts or
components, su'ch as toasters, broilers, slow cookers,
dishwashers, refrigerators, ovens, ranges, clothes
dryers, electric blankets, and popcorn poppers.
(Unless broken or misused, most appliances with
asbestos are safe. There has been a general decline
in the use of asbestos in these appliances during
recent years. If asbestos is still used, it is in parts
which will probably not release fibers during use.)
Having significant amounts of asbestos in the home is not rare. Many
old homes in New Jersey could create health problems for residents
because of materials that may release asbestos fibers into the air.
HOW CAN I TELL IF I HAVE ASBESTOS IN MY HOME?
The manufacturer of a product may be able to tell you, based on
the model number and age of the product, whether or not it contains
asbestos. People who have frequently worked with asbestos (such as
plumbers, or building or heating contractors) can often tell you
whether or not material contains asbestos by looking at it.
Problems may occur in the home where asbestos-containing
materials are worn, damaged, or exposed to the air. If you have
-------
wail, you should have the material analyzed to determine if it
contains asbestos. Laboratory analyses range from about $20 to S40
per sample. Several samples may be required to gain an accurate
determination of asbestos content.
If you suspect that you have a problem, you may also want to
have an air sample taken to measure the amount of asbestos fibers
circulating inside your h6me. To collect the sample, a laboratory
wii! .send a technician to your home. A pump is used to draw air
from the room into a filter that will trap the asbestos. An
electron microscope is used to count the number of fibers trapped
in the filter. It takes about six hours to collect the sample and '
costs between SlOO and $400, depending on the laboratory and
technique used. The results of the test can be reported in units
of "fibers per liter of air," abbreviated as f/1. This unit tells
how much asbestos there is in one liter of air.
WHAT SHOULD I DO IF I HAVE AN ASBESTOS PROBLEM?
If you discover that you have an asbestos problem, the best
thing to do is to contact a contractor who has experience in the
proper procedures for repairing and removing asbestos. There are
special guidelines for handling asbestos-containing materials. You
should avoid drilling, scraping, sanding, brushing, sweeping or
vacuuming asbestos materials. This will disturb tiny asbestos
fibers, make them airborne, and increase the risk of breathing
them. It is highly recommended that you hire an experienced
contractor or get professional advice if you are thinking of doing
the work yourself. A contractor will seal off the contaminated
area from the rest of the house and workers will use protective
clothing and a special respirator while they are handling the
asbestos. Using improper techniques can make an existing problem
much worse by contaminating the entire house. For more information
about identifying, testing, handling, and fixing asbestos problems
call the New Jersey Department of Health toll-free at
1-800-624-2376.
INTERPRETING YOUR TEST RESULT:
The U.S. Environmental Protection Agency has evaluated
the risk from asbestos. The following statement about the EPA
regulation for schools and public buildings can help you
interpret your own (imaginary) asbestos test result:
A home level of 3 f/l or above corresponds
to the risk at which EPA requires action
in schools and public buildings.
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STANDARD - LADDER BRCCH'Jr^
{La s c Two Paces)
-a':l.;. c- shouic have the material anaivzeci to determine if it contains
.i.^ev.os. Lcooratory analyses range from about S20 to $40 per sample.
Several samples mav ne required :o gain an accurate determination of
.iioestcs content.
I: you suspect that you have a problem, you may also want to have an
a>r sample taken to measure the amount of asbestos fibers circulating
ins-ce you: home. To collect the sample, a laboratory will send a
'.ech.p.icar. :o vour home. A pump is used to draw air from the room into a
:':iter that will :rap the asbestos. An electron microscope is used to
count the number of fibers trapped in the filter. It takes about six
hours to collect the sample and costs between $100 and S400, depending on
the laboratory and technique used. The results of the test can be
reported in units of "fibers per liter of air," abbreviated as f/1. This
unit tells how much asbestos there is in one liter of air.
WHAT SHOULD I DO IF I RAVE AN ASBESTOS PROBLEM?
If you discover that you have an asbestos problem, the best thing to
do is to contact a contractor who has experience in the proper procedures
for repairing and removing asbestos. There are special guidelines for
handling asbestos-containing materials. You should avoid drilling,
scraping" sanding, brushing, sweeping or vacuuming asbestos materials.
Tnis will disturb tiny asbestos fibers, make them airborne, and increase
the risk of breathing them. It is highly recommended that you hire an
experienced contractor or get professional advice if you are thinking of
doing the work yourself. A contractor will seal off the contaminated
arealrom the rest of the house and workers will use protective clothing
and a special respirator while they are handling the asbestos. Using
improper techniques can make an existing problem much worse by
contaminating the entire house. For more information about identifying,
testing handling, and fixing asbestos problems call the N. J.
Deoartment of Health toll-free at 1-800-624-2376.
INTERPRETING YOUR TEST RESULT:
Using the imaginary test result we have given you, look
down the column on the next page headed "Asbestos Level," and
find the level nearest to your test result. The U. S.
Environmental Protection Agency has evaluated the risk from
asbestos and has issued a regulation for schools and public
buildings that can help you interpret your asbestos test
result. The arrow to the right of the column gives information
about this EPA action guideline.
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INTERPRETING YOUR TEST RESULT:
Asbestos
Level '
a/i)
U 100 -4
U 50 -J
— 20
L
U 10 -4
r
3 -J
2 -4
.5
A home level of 3 f/l or oboye corresponds
to the risk at whid\ EPA_ requires action
in schools and public buildings.
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RUTGERS
COOK College • Deoo'tme'-.t of Hurr^an Ecology
°O 3ox 231 • r^ew Brunswick • New jersey C3903 • 2C1- v32.9-.S2
Dear New Jersey Resident:
Thank you for talking with us on the phone and for agreeing to take
part in our project. At Rutgers we are developing different information
brochures for people who test their homes for asbestos. The feedback
questionnaire you return will show us whether the brochure we sent you is
helpful.
There are no right or wrong answers. We need to get your reactions
and your opinions to evaluate the brochure. All your answers are kept
confidential. The code number on the feedback questionnaire is only used
to show us which questionnaires have been returned, so we don't call and
remind people who have ?lready trailed back their answers.
DIRECTIONS
Pretend that you have just had your house tested for asbestos.
The testing company tells you that you have a reading of
fibers per liter on your first floor and you are
trying to decide whether you should do anything about it. Read
the "Test Brochure" to help you interpret your imaginary test
result and then fill out the questionnaire. FEEL FREE TO REFER
TO THE BROCHURE WHEN ANSWERING THE FEEDBACK QUESTIONS. When
you have finished, mail the questionnaire back to us in the
envelope that we have provided. The Test Brochure is yours to
keep.
THANK YOU VERY MUCH FOR YOUR HELP.
Sincerely,
Neil D. Weinstein, Professor
Peter M. Sandman, Professor
Paul M. Miller, Project Director
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FEEDBACK QUESTIONNAIRE
we appreciate your help in filling out this questionnaire because this is
ine only way we can find out 'whether the brochure has been successful in
explaining your risk. Feel free to look back at the brochure 'when
answering the questions.
******************************************************
Your imaginary asbestos
test result on your
main floor is:
fibers/liter (f/1)
Use this level when answering questions
about how serious a problem you have.
******************************************************
Overall, how would you rate the brochure we sent you?
answer in each row.)
(Please circle one
very difficult
to understand
fairly difficult
to understand
fairly easy
to understand
very easy
to understand
didn't help
rre understand
r.ty test result
a little
helpful for
unders-canding
my test result
moderately
helpful for
understanding
my test result
very helpful
for understandinc
my test result
much too
little
information
too little
information
about right
too much
information
much too
much
information
4. Did the brochure give you a good understanding of the risk from your
asbestos level?
( ] I have a very good understanding of the risk
[ ] I have a fairly good understanding of the risk
[ ] I feel fairly uncertain about the risk
( ] I feel very uncertain about the risk
5. Hew would you describe the danger from your (imaginary) asbestos
level?
( ] no danger
[ ] very slight danger
[ ] slight danger
[ ] moderate danger
[ ] serious danger
[ ] very serious danger
989
-------
ISPLACED CONDITION
INTERPRETING YOUR TEST RESULT:
Asbestos
level
(171)
Extra
Cancer
Deaths
(Out of 1000
People)
Comparison to
Smoking Risk
75
35
15
7.5
3.5
1.5
.75
.35
.15
15 in 1000
7 in 1000
3 in 1000
1.5 in 1000
Jin 1000
.3 in 1000
.15 in 1000
.07 in 1000
.03 in 1000
6 cigarettes/day
cigarette/ day
0
1/4 cigarette/day
1/10 cigarene/day
1/100 cigarette/day
-------
FORMAT PAGE
HIGH TEST CONDITION
INTERPRETING YOUR TEST RESULT:
Asbestos
level
(f/cubic foot)
Extra
Cancer
Deaths
(Out of 1000
People)
Comparison to
Smoking Risk
— 45,000
— 22,500
— 10,500
— 4,500
2.250
1,050
450
225
105
300 in 1000
150 in 1000
70 in 1000
30 in 1000
15 in 1000
7 in 1000
3 in 1000
1.5 in 1000
.7 in 1000
6 packs/ day
1/2 packs/day
6 cigarettes/day
cigarette/ day
D
1/4 cigarette/ day
-------
5ASE AND DISPLACED CONDITIONS
THE STATE UNIVERSITY OF NEW jERS
RUTGERS
COOK College • Deoartment of Human Ecology
PO Box 231 • New Brunswick • New jersey 08903 • 201 932-9155
Dear New Jersey Resident:
Thank you for talking with us on the phone and for agreeing to
take part in our project. At Rutgers we are developing different
information brochures for people who test their homes for asbestos.
The feedback questionnaire you return will show us whether the
brochure we sent you is helpful.
There are no right or wrong answers. We need to get your
reactions and your opinions to evaluate the brochure. All your
answers are kept confidential. The code number on the feedback
questionnaire is only used to show us which questionnaires have been
returned, so we don't call and remind people who have already mailed
back their answers.
DIRECTIONS
Pretend that you have just had your house tested for asbestos.
The testing company tells you that you have a reading of
fibers per liter on your first floor and you are trying
to decide whether you should do anything about it. Read the
"Test Brochure" to help you interpret your imaginary test result
and then fill out the questionnaire. FEEL FREE TO REFER TO THE
BROCHURE WHEN ANSWERING THE FEEDBACK QUESTIONS. When you have
finished, mail the questionnaire back to us in the envelope that
we have provided. The Test Brochure is yours to keep.
THANK YOU VERY MUCH FOR YOUR HELP.
Sincerely,
7k!Uh
Neil D. Weinstein, Professor
Peter M. Sandman, Professor
Paul M. Miller, Project Director
-------
FEEDBACK QUESTIONNAIRE
We appreciate your help in filling out this questionnaire because this is
the only way we can find out whether the brochure has been successful in
explaining your risk. Feel free to look back at the brochure when
answering the questions.
******************************************************
Your imaginary asbestos
test result on your
floor is:
fibers per liter
(f/ 1)
Use this level when answering questions
about how serious a problem you have.
******************************************************
Overall, how would you rate the brochure we sent you?
answer in each row.)
(Please circle one
1. very 'difficult
to understand
fairly difficult
to understand
fairly easy
to understand
very easy
to understand
didr t help
me understand
my test result
a little
helpful for
understanding
my test result
moderately
helpful for
understanding
my test result
very helpful
for understanding
my test result
much too
little
information
too little
information
about right
too much
information
much too
much
information
4. Did the brochure give you a good understanding of the risk from your
asbestos level?
[ ] I have a very good understanding of the risk
[ ] I have a fairly good understanding of the risk
r ] I feel fairly uncertain about the risk
f ] I feel very uncertain about the risk
5. How
level?
would you describe the danger fron your (imaginary) asbestos
[ ] no danger
( ] very slight danger
[ ] slight danger
[ ] moderate danger
[ ] serious danger
[ ] very serious danger
989
-------
ontinued to live in the here with your test result arc didn't
do anything about the asbestos, what do you think are the chances that
you would eventually have sore illness due to asbestos? (Even though
you rray feel uncertain, please circle an answer to tell us what
irpression you got from the brochure.)
.10 very unlikely moderate luety very certain
chance unlikely chance likely to happen
Hew do you think you would feel if your own hone actually had the asbestos
level found by the imaginary test? (Please-circle one answer in each
row.)
7. not at all slightly concerned very extremely
concerned concerned concerned concerned
3. not at all slightly frightened very extremely
frightened frightened frightened frightened
9. What is your impression of how difficult it is to reduce the asbestos
level if houses have a problem?
[ ] very difficult
[ ] fairly difficult
[ ] fairly easy
[ ] very easy
10. Let's say that reducing your asbestos level close to zero would cost a
thousand dollars ($1000). Given what you have learned aocut the size
of your present risk, do you think you would decide to carry out
asbestos reduction measures?
[ ] definitely would take measures to reduce the asbestos level
[ ] probably would take measures
[ ] cannot decide what to do
[ ] probably would NOT take measure
[ ] definitely would NOT take .measures
11. If you continued to live in the home with your test result and didn't
do anything about the asbestos, what do you think are the odds that
you would eventually have some illness due to asbestos? (Please put a
check in the box that comes closest to your opinion.)
c ] c ] M c ] c i c i c i c ] t J c i
no chance 1 chance 1 chance 1 chance certain no
in 1,000 in 100 ' in 10 (100X) idea
(0.1X) OX) (10X)
-------
12. At what asbestos level (in your main living area) do you think you
would feel satisfied, so that you vrould not spend more money trying to
get the level even lower?
[ ] NO asbestos
[ ] .15 fibers/liter
[ ] .35 fibers/liter
[ ] .75 fibers/liter
[ ] 1.5 fibers/liter
[ ] 3.5 fibers/liter
[ ] 7.5 fibers/liter
[ ] 15 fibers/liter
[ ] 35 fibers/liter
[ ] 75 fibers/liter
[ ] 150 fibers/liter
[ ] 350 fibers/liter
For classification purposes, please tell us:
a. Your sex: [ ] male [ ] female
b. Your age:
c. How much school have you completed?
[ ] some elementary school
[ ] finished elementary school
[ ] some high school
[ ] finished high school
[ ] some college
[ ] finished 2-year college
[ ] finished 4-year college
[ ] some graduate study
[ ] graduate degree
d. Prior to receiving our brochure, how much had you read about asbestos:
[ ] very little [ ] moderate amount (at least one
[ ] small amount information booklet or a
magazine article)
[ ] a lot
e. Have you tested your own house, condoninium or apartment for asbestos:
[ 1 no
[ ] yes
f. Have you heard of any government standard or "action level" for
asbestos in homes:
[ 1 no
[ ] yes > What do you think is the government action level:
Level is: [ ] don't know
THMJK TOO FOR TOOR TIME AND HELP!
If you want a copy of some of the other brochures we're testing/ please
fill out the mailing label and include it in the envelope when you mail
back the questionnaire.
-------
HIGH RISK CONDITION PAGE
12. At what asbestos level (in your main living area) do you think you
would feel satisfied, so that you would not spend more money trying to
get the level even lower?
[ ] NO asbestos
[ ] .15 fibers/deciliter
f ] .35 fibers/deciliter
[ ] .75 fibers/deciliter
[ ] 1.5 fibers/deciliter
[ ] 3.5 fibers/deciliter
] 7.5 fibers/deciliter
15 fibers/deciliter
35 fibers/deciliter
75 fibers/deciliter
150 fibers/deciliter
[ ] 350 fibers/deciliter
[ ]
[ ]
[ ]
For classification purposes, please tell us:
a. Your sex: [ ] male [ ] female
b. Your age:
c. How much school have you completed?
[ ] some elementary school-
[ ] finished elementary school
[ ] some high school
( ] finished high school
[ ] some college
[ ] finished 2-year college
[ ] finished 4-year college
[ ] some graduate study
[ ] graduate degree
Prior to receiving our brochure, how much had you read about asbestos:
[ ] very little [ ] moderate amount (at least one
[ ] small amount information booklet or a
magazine article)
[ ] a lot
Have you tested your own house, cordominium or apartment for asbestos:
[ ] no
[ ] yes
f. Have you heard of any government standard or "action level" for
asbestos in hones:
[ ] no
[ ] yes > What do you think is the government action level:
Level is: [ ] don't know
THANK YOU FOR TOOK TIME AND HELP!
If you want a copy of seme of the other brochures we're testing, please
fill out the mailing label and include it in the envelope when you mail
back the questionnaire.
-------
N P
12. At what asbestos level (in your main living area) do you think you
would feel satisfied, so that you would not spend more money trying to
get the level even lower?
[ ] NO asbestos [ ]
[ ] 4.5 fibers/cubic ft [ ]
[ ] 10.5 fibers/cubic ft [ ]
[ ] 22.5 fibers/cubic ft [ ]
[ ] 45.0 fibers/cubic ft [ ]
[ ] 105 fibers/cubic ft [ ]
225 fibers/cubic ft
450 fibers/cubic ft
1050 fibers/cubic ft
2250 fibers/cubic ft
4500 fibers/cubic'ft
10500 fibers/cubic ft
For classification purposes, please tell us:
a. Your sex: [ ] male [ ] female
b. Your age:
c. How much school have you completed?
[ ] sore elementary school
[ ] finished elementary school
[ ] some high school
[ ] finished high school
[ ] some college
[ ] finished 2-year college
[ ] finished 4-year college
[ ] some graduate study
[ ] graduate degree
Prior to receiving our brochure, how much had you read about asbestos:
[ ] very little [ ] moderate amount (at least one
[ ] small amount information booklet or a
magazine article)
[ ] a lot
Have you tested your own house, condominium or apartment for asbestos:
C ] no
[ ] yes
f. Have you heard of any government standard or "action level" for
asbestos in hones:
C ] no
[ ] yes > What do you think is the government action level:
Level is: [ ] don't know
TOU FOR TODR TIME AND HELP!
If you want a copy of some of the other brochures we're testing/ please
fill out the mailing label and include it in the envelope when you mail
bade the questionnaire.
-------
APPENDIX C
EXPERIMENT III BROCHURES, FORMATS, AND QUESTIONNAIRES
Experiment III had five conditions: Joint Radon and Asbestos, Base Radon, Base Asbestos,
High Risk Asbestos, and Displaced Asbestos. The Appendix begins with the two two-page
brochures that were used, one for radon and one for asbestos (subjects in the Joint
condition received both brochures). There are six format pages: two versions of the Joint
format page (one with asbestos first and one with radon first), followed by the Base Radon,
Base Asbestos, High Risk Asbestos, and Displaced Asbestos format pages, in that order.
Next comes the six-page response questionnaire used for the Joint condition (a one-page
cover letter, two pages on radon, two pages on asbestos, and one page of demographic
items). The other four conditions used the same, questionnaire, but with either the two
radon pages or the two asbestos pages omitted. The alternative cover letters used for the
Base Radon condition and the various asbestos conditions are provided at the end of the
Appendix.
133
-------
Experinent HI Paccn Brocnure
Test Brochure*
4/90
BASIC RADON INFORMATION
WHAT IS RADON?
Radon is a radioactive gas that occurs in nature. It has no color, odor, or taste.
Radon comes from the natural breakdown (radioactive decay) of the uranium present in
rocks and soil. This is not an unusual situation; rocks and soil often contain small amounts
of uranium. Radon can move through the soil into the open air.
WHY THE CONCERN ABOUT RADON?
Exposure to elevated levels of radon increases the risk of lung cancer. Radon is
not known to cause any other health problem, except lung cancer. Not everyone exposed to
elevated levels of radon will develop lung cancer. Still, in some houses the level of risk is
very high. Studies suggest that between 5,000 and 30,000 lung cancer deaths a year in the
United States are caused by radon.
The time between the exposure and the onset of the disease may be many years.
There are no symptoms or early-warning signs to tell you that you have a high radon level
in your home.
The risk increases as the level of radon and the length of exposure increase.
Therefore,' exposure to a low level for a long time may present a greater chance of cancer
than exposure to a higher level for a short time.
HOW DOES RADON AFFECT US?
Radon naturally breaks down and forms decay products that cling to dust and
other particles in the air. As we breathe, these particles can become trapped in our lungs
with the radon decay products still attached. As these trapped radon products decay
further, they release small bursts of radiation that can damage lung tissue and lead to lung
cancer.
HOW DOES RADON ENTER A HOME?
Outdoors, radon from the soil mixes with the rest of the air. This mixing dilutes
the radon, producing concentrations that are usually quite low. Inside an enclosed space
there is usually less fresh air to dilute the radon. Therefore, radon inside a home can
accumulate, and sometimes it reaches dangerous levels. Homes that are airtight hold radon
longer and prevent fresh outside air from entering the home. On the other hand, keeping
windows open and ventilating will usually lower the concentration of radon in the air inside
the home.
Radon can seep into a home through any opening in the walls or floor of the
foundation, openings around pipes, sump pump holes, and unpaved crawl spaces. Radon
can also enter the water of private wells and be released into a home when the water is
used. This is not usually a problem with public water supplies, because the radon would
probably be released into the outside air during treatment before the water ever reached
the home.
* Because this is an experimental brochure, please check with other authorities before taking any action in your
home.
-------
HOW IS RADON DETECTED?
Since you cannot see or smell radon, special equipment is needed to detect it.
The devices that may be used to determine if your home has high radon levels include the
alpha-track detector, the charcoal canister, and others. The first two devices are very
simple to use. They involve removing the seal or top of a small canister and placing the
canister on a shelf or table in the area you want to test. By removing the seal a special
material is exposed which will register the amount of radon in the air. After the prescribed
amount of time (several days to several months) you simply replace the top of the canister
and mail it to the laboratory for analysis. Typical costs range from S12 to S50 per test.
Because radon levels in a home often vary from day to day, measurements over a brief time
period give only a rough indication of the situation.
If your home was tested with a charcoal or alpha-track detector, the results will
probably be reported in units of "picocuries per liter of air," abbreviated as pCi/1. This unit
tells how much radon there is in one liter of air.
IS IT DANGEROUS IF I FIND I HAVE HIGH LEVELS?
Radon is a serious risk. There is no level of exposure to radon in the home that
experts can agree is completely safe. The chances of suffering harm from elevated radon
levels are much greater than the chances of suffering harm from most other pollution
problems. As Consumer Reports has stated, "While there are uncertainties in pinpointing
low-level radon risks, there is no doubt that the risks of radon vastly exceed the risks from
aflatoxin, PCBs, nuclear wastes, and virtually all other environmental hazards" (July 1987, p.
442). The disease caused by radon, lung cancer, is incurable and almost always fatal. For
these reasons it is important to identify radon problems and take steps to reduce your
exposure before any illness occurs.
CAN I DO ANYTHING IF I HAVE HIGH RADON LEVELS AT HOME?
Even very high radon concentrations can be lowered. On a short-term basis, just
keeping windows open will usually substantially lower the radon level. But this is too
expensive to continue during the heating season. Other, more permanent methods are
described in a booklet entitled "Radon Reduction Methods: A Homeowner's Guide" that is
available from the New Jersey Department of Environmental Protection radon information
line, 1-800-648-0394.
INTERPRETING YOUR TEST RESULT:
Use the chart on the last page of this brochure to interpret the imaginary
test result we gave you. First, look down the left-hand column headed "Radon
Level," and find the number nearest to your radon test result.
Next, move toward the right to the middle column headed "Extra Cancer
Deaths." The number in this column tells you how many people are expected to
die of cancer because of radon out of every 1000 people who live in a home with
the same radon level as yours.
Finally, move over to the right-hand column entitled "Comparison to
Smoking Risk." It tells you how many cigarettes a day a person would have to
smoke to have the same cancer risk as living with your radon level.
-------
zxoeriment
Test Brochure*
4/90
BASIC ASBESTOS INFORMATION
WHAT IS ASBESTOS?
Asbestos is a mineral fiber found in rocks. There are several kinds of asbestos
fibers, all of which are fire-resistant and not easily destroyed by natural processes. Because
of its desirable, qualities, asbestos has been used in a wide variety of products including
appliances, ceilings, wall and pipe coverings, floor tiles, and some roofing materials.
WHY THE CONCERN ABOUT ASBESTOS?
Although asbestos has many benefits for humans, it is also a very dangerous
mineral. Breathing airborne asbestos fibers has been shown to cause: (1) Asbestosis - a
serious lung disease which can lead to disability and death; (2) Lung cancer - a disease that
is incurable and almost always fatal; and (3) Mesothelioma - cancer of the lining of the
lungs or abdominal cavities. The greater the exposure to asbestos, the more likely it is that
one of these serious diseases will develop. Workers who handle or come into contact with
asbestos on a daily basis are open to the greatest health risks.
There is no level of exposure to asbestos fibers that is completely safe. The
greater the concentration of asbestos, and the longer the exposure, the greater the risk.
HOW DOES ASBESTOS AFFECT US?
The danger arises when the asbestos fibers are released from the product or
material. These fibers are so small that they cannot be seen. They can float in the air for
a long time and can pass through the filters of normal vacuum cleaners and get back into
the air. Once inhaled, asbestos fibers can become lodged in tissue for a long time. After
many years cancer or asbestosis can develop. Cigarette smoking combined with asbestos
exposure is especially hazardous.
Asbestos found in "friable" materials is most dangerous. Friable materials are
materials that can be crumbled, pulverized, or reduced to powder by hand pressure.
Asbestos insulation sprayed on a ceiling is an example of a friable material. In contrast,
vinyl asbestos floor tile is not usually friable. The asbestos fibers are firmly bound or
sealed into the die and can be released into the air only if the tile is cut, ground, or sanded.
WHERE IS ASBESTOS LIKELY TO BE FOUND IN THE HOME?
There are several areas in the home where asbestos problems are most likely to
arise. These include:
* Wall construction material and pipe insulation, especially those dating between
' 1920 and 1972.
* Friable ceilings in buildings built or remodeled between 1945 and 1978.
* Material found in stoves and furnaces such as insulation and door gaskets.
• Because this is an experimental brochure, please check with other authorities before taking any action in your
home.
-------
Other asbestos-containing products that you may find in the home include:
* Patching compounds and textured paints (applied prior to 1975).
* Vinyl floor tiles and flooring.
* Roofing, shingles, and siding.
* Appliances with asbestos-containing parts or components, such as toasters, broilers,
slow cookers, dishwashers, refrigerators, ovens, ranges, and clothes dryers.
Having significant amounts of asbestos in the home is not rare. Many old homes in
New Jersey could create health problems for residents because of materials that may
release asbestos fibers into the air.
HOW CAN I TELL IF I HAVE ASBESTOS IN MY HOME?
People who have worked frequently with asbestos (such as plumbers, and building
or heating contractors) can often tell you whether or not material contains asbestos by
looking at it.
If you suspect that you have a problem, you may also want to 'have an air sample
taken to measure the number of asbestos fibers circulating inside your home. To collect
the sample, a laboratory will send a technician to your home. A pump is used to draw air
from the room into a filter that will trap the asbestos. An electron microscope is used to
count the sample. The test costs between S100 and $400, depending upon the laboratory
technique used. The results of the test can be reported in units of "fibers per deciliter of
air," abbreviated as f/dl. This unit tells how much asbestos there is in one deciliter (one-
tenth of a liter) of air.
WHAT SHOULD I DO IF I HAVE AN ASBESTOS PROBLEM?
If you discover that you have an asbestos problem, the best thing to do is to
contact a contractor who has experience in the proper procedures for repairing and
removing asbestos. There are special guidelines for handling asbestos-containing materials.
It is highly recommended that you hire an experienced contractor or get professional advice
if you are thinking of doing the work yourself. Using improper techniques can make an
existing problem much worse by contaminating the entire house. For more information
about identifying, testing, handling, and fixing asbestos problems call the N.J. Department
of Health-toll-free at 1-800-624-2376.
INTERPRETING YOUR TEST RESULT:
Use the chart on the last page of this brochure to Interpret the imaginary test
result we gave you. First, look down the left-hand column headed "Asbestos
Level," and find the number nearest to your asbestos test result.
Next, move toward the right to the middle column headed "Extra Cancer
Deaths." The number In this column tells you how many people are expected to
die of cancer because or asbestos out of every 1000 people who live in a home
with the same asbestos level as yours.
Finally, move over to the right-hand column entitled "Comparison to Smoking
Risk." It tells you how many cigarettes a day a person would have to smoke to
have the same cancer risk as living with your asbestos level.
-------
Experiment III Joint Format (two versions)
INTERPRETING YOUR TEST RESULT:
As be .si os
level
(fibers/
liter)
— 2000
— 1000 —
— 500 —
— 250 -
20
— 60 —
— 15 —
0
v>
Radon
level
(pdl :
liter). .
80
- 40 —
- 20 ' —
— 10 —
- 2.5 —
12'
— , ,6 —
''** * •*"* "
3
. . • :"' :. ;';'.":','; v,'i-;--v'"-
Extra
Cancer
Deaths
(out of 1000
people)
400 in 1000
200 in 1000 -
100 in 1000 —
- 50 in 1000 -
— ^> r • i r\r\f\ —
/J 11) IUUU
12 in 1000 ~
6i n i nno
- 3 in 1000 • —
1 S in 1000
Comparison to
Smoking Risk
H^md^wtB^B
MI
8 packs/ day
— _
^^
m . -
2 packs/ day
n ii n ii nim fin ii
UUUUUUuuuu
10 cigarettes/ day
— —
flfln
2 1/2 cigarettes/ day
_» __
0
1/2 cigarette/ day
-------
A2
INTERPRETING YOUR TEST RESULT:
1
Radon.
level
(pCi/
liter)
so ";—
40 —
-^ s\.
20 —
:,^i$;:vr
"5. —
-
2.5 —
1.2, —
.6: -
1-Sftil—
Asbestos
level
(fibers/
liter)
- 2000 —
- 1000 —
— 500
— 250 ~
- 120 ~
~ 60 —
- 30 —
- 15 —
- 8 —
Extra
.Cancer
Deaths
(out of 1000
people)
- 400 in 1000 —
200 in 1000 -
__ i r\/*\ • 1 f\f\f\ -
100 m 1000
50 in 1000 -
25 in 1000 —
12 in 1000 —
- 6 in 1000 —
- 3 in 1000 -
1.5 in 1000 -
Comparison to
Smoking Risk
"fTWTfth'
8 packs/ day
m
1 I 1
2 packs/ day
— —
- mmmi -
10 cigarettes/ day
— —
ODD
2 1/2 cigarettes/ day
— —
D
1/2 cigarette/ day
-------
, txperiment II! 3ase Radon i-orrr.at
INTERPRETING YOUR TEST RESULT:
Radon
level
(pCi/
liter)
Extra
Cancer
Deaths
(out of 1000
people)
Comparison to
Smoking Risk
— 80
40
— 20
— 10
— 2.5
.6
.3
400 in 1000
200 in 1000
100 in 1000
50 in 1000
25 in 1000
12 in 1000
6 in 1000
3 in 1000
1.5 in 1000
8 packs/day
2 packs/ day
10 cigarettes/day
0
2 1/2 cigarettes/day
D
1/2 cigarette/day
-------
Exoenrrent III Sase Asoestos Format
INTERPRETING YOUR TEST RESULT:
Asbestos
level
(fibers/
liter)
Extra
Cancer
Deaths
(out of 1000
people)
Comparison to
Smoking Risk
— 2000
1000
500
— 250
120
60
— 30
— 15
400 in 1000
200 in 1000
100 in 1000
50 in 1000
25 in 1000
12 in 1000
6 in 1000
3 in 1000
1.5 in 1000
8 packs/ day
2 packs/ day
10 cigarettes/day
0
2 1/2 cigarettes/day
D
1/2 cigarette/day
-------
D
HIGH RISK ASBESTOS FORMAT PAGE
INTERPRETING YOUR TEST RESULT:
Asbestos
level
(fibers/
deciliter)
Extra
Cancer
Deaths
(out of 1000
people)
Comparison to
Smoking Risk
200
100
50
25
12
— 1.5
— .8
400 in 1000
200 in 1000
100 in 1000
50 in 1000
25 in 1000
12 in 1000
6 in 1000
Sin 1000
1.5 in 1000
8 packs/ day
2 packs/ day
10 cigarettes/day
n
2 1/2 cigarettes/ day
D
1/2 cigarette/day
-------
EXPERIMENT in
DISPLACED ASBESTOS FORMAT PAGE
INTERPRETING YOUR TEST RESULT:
Asbestos
level
(fibers/
liter)
— 60 -
- 30 -
— 15 -
— 8 -
— 4 —
_ ~) ~~~
— 1 -
_ .5 —
_ .3 —
Extra
Cancer
Deaths
(out of 1000
people)
— 12 in 1000 —
— 6 in 1000 —
— 3 in 1000 —
— 1.5 in 1000 -
— / ,8 in 1000 —
— .4 in 1000 —
— .2 in 1000 -
— ,1 in 1000 -
— .05. in 1000 -
Comparison to
Smoking Risk
— —
Bin
2 1/2 cigarettes/ day
_ __
D
1/2 cigarette/ day
_ —
B
1/8 cigarette/ day
— • —
_
1/30 cigarette/ day
-------
Feedback Questionnaire
RUTGERS
Cook College • Deoa.'tment of Human Ecology
PO 3cx 23' • New Brunswick • New jersey 03903 • 201 932-?'53
Dear New Jersey Resident:
Thank you for talking with us on the phone and for agreeing to
take part in our project. At Rutgers we are developing different
Information brochures for people who test their homes for radon or
asbestos. The feedback questionnaire you return will show us whether
the brochures we sent you are helpful.
There are no right or wrong answers. We need to get your
reactions and your opinions to evaluate the brochures. All your
answers are kept confidential. The code number on the feedback
questionnaire is only used to show us which questionnaires have been
returned, so we don't call and remind people who have already mailed
back their answers.
DIRECTIONS
Pretend that you have just had your house tested for asbestos and
radon. The testing company tells you that you have the following
readings on your first floor and you are trying to decide whether
you should do anything about it.
asbestos _ fibers per liter
radon _ picocuries per liter
Read the "Test Brochures" to help you interpret your
imaginary test results and then fill out the questionnaire.
FEEL FREE TO REFER TO THE BROCHURES WHEN ANSWERING THE
FEEDBACK QUESTIONS. When you have finished, mail the
questionnaire back to us in the envelope that we have
provided. The Test Brochures are yours to keep.
THANK YOU VERY MUCH FOR YOUR HELP.
Sincerely,
Neil D. Weinstein, Professor
Peter M. Sandman, Professor
Paul M. Miller, Project Director
-------
?J\DON FEEDBACK ^JESTICN^'AIRE
THEOUESTIONS ON THIS PAGE ARE FOR RADON,
FEEDBACK QUESTIONNAIRE
******************************************************
* *
* Your imaginary radon *
* test result on your *
* main floor is: *
* • *
* picocuries/liter (pCi/1) *
* *
* Use this level when answering questions *
* about how serious a problem you have. *
* *
******************************************************
Overall, how would you rate the information about radon we sent you?
(Please circle one answer in each row.)
1. very difficult fairly difficult fairly easy very easy
to understand to understand to understand to understand
2. didn't help me a little moderately very helpful
understand my helpful for helpful for for understanding
test result understanding understanding my test result
my test result my test result
3. How would you describe the danger from your (imaginary) radon
level? (Please check one box to indicate your feelings.)
[ ] no danger
[ ] very slight danger
[ ] slight danger
[ j moderate danger
[ ] serious danger
[ ] very serious danger
4. How likely do you think it is that continued exposure to your
imaginary radon level would eventually have harmful effects?
(Even though you may feel uncertain, please circle an answer to
tell us what impression you got from the information we sent you.)
no very unlikely inoderate likely very certain
chance unlikely chance /likely to happen
How do you think you would feel if your own home actually had the
radon level found by the imaginary test? (Please circle one answer
in each row.)
.5. not at all slightly moderately very extremely
concerned concerned concerned concerned concerned
6. not at all slightly moderately very extremely
frightened frightened frightened frightened frightened
-------
THE QUESTIONS ON THIS PAGE ARE FOR RADON.
let's say that reducing your imaginary radon level close to zero
would cost a thousand dollars ($1000) . Given what you have learned
about the size of the risk, do you think .you would decide to carry
out radon reduction measures?
r ] definitely would reduce the level
[ ] probably would reduce the level
cannot decide what to do
probably would NOT reduce the level
definitely would NOT reduce the level
If someone lived in the home with your imaginary test result and did
nothing about the radon, what do you think are the chances that
s/he would eventually have some illness due to radon? (Please
check the box that comes closest to your opinion.)
[ ] no
[ ] • 1
1" ] . 2
i i . 5
[ ] 1
[ ] 2
[ ] 5
chance
chance
chance
chance
chance
chances
chances
in
in
in
in
in
in
1,
1,
1,
1,
1,
1,
000
000
000
000
000
000
[ ] 10
[ ] 20
[ ] 40
[ ] 80
[ ] 120
[ 1 250
[ ] don
chances
chances
chances
chances
chances
chances
't know
in
in
in
in
in
in
1,
1,
1,
1,
1,
1,
000
000
000
000
000
000
For questions 9-13 below please check the box that best indicates your
'impression about radon. For.example, in the sample item below, if your
impression was that radon was very often found in homes, but not
always, then you would check the box shown below.
Sample Question: How frequently is radon found in homes?
never [ ] [ ] [ ] [ ] [ ] |j(] [ ] always
9. How easily can radon levels be reduced?
very easy
to reduce [ ] [ ] [ ] [ ]
very difficult
[ ] [ ] to reduce
10.
Is radon a risk that people can think about reasonably calmly,
or is it one that people have great dread for--on the level of a
gut reaction?
calm
reaction [ ]
C 1 [ ] -C ]
[
C
dread
[ ] risk
11. If someone became sick because of radon, how likely is it that
the illness would be fatal?
'certain not
to be fatal [ ]
certain
[ ] to be fatal
12
[ ] [ ] [ ] C ] C 1
Is radon a risk that is new and novel or old and familiar?
old [ ] [ ] [ ] [ ] [ ] [ ] [ ] new
13. To what extent are the risks from radon the result of natural
processes, or are the risks man-made?
all man-made [ ] [ ] [ ] [ ] [ ] [ ] [ ] all natural
-------
THE QUESTIONS ON THIS PAGE ARE FOR ASBESTOS.
FEEDBACK QUESTIONNAIRE
******************************************************
* ' *
* Your imaginary asbestos *
* test result on your *
* main floor is: *
* *
* fibers/liter (f/1) *
* *
* Use this level when answering questions *
* about how serious a problem you have. *
* *
Overall, how would you rate the information about asbestos We sent
you? (Please circle one answer in each row.)
1. very difficult fairly difficult fairly easy very easy
to understand to understand to understand to understand
2. didn't help me a little moderately very helpful
understand my helpful for helpful for for understanding
test result understanding understanding my test result
my test result my test result
3. How would you describe the danger from your (imaginary) asbestos
level? (Please check one box to indicate your feelings.)
[ ] no danger
[ ] very slight danger
[ ] slight danger
[ ] moderate danger
[ ] serious danger
[ ] very serious danger
4. How likely do you think it is that continued exposure to your
imaginary asbestos level would eventually have harmful effects?
(Even though you may feel uncertain, please circle an answer to
tell us what impression you got from the information we sent you.)
no very unlikely moderate likely very certain
chance unlikely chance likely to happen
How do you think you would feel if your own home actually had the
asbestos level found by the imaginary test? (Please circle one answer
in each row. )
5. not at all slightly moderately very extremely
concerned concerned concerned concerned concerned
6. not at all slightly moderately very extremely
frightened frightened frightened frightened frightened
(Over)
-------
THE QUESTIONS ON THIS PAGE ARE FOR AS3ESTCS.
Le-.'j say tr.at reducing your imaginary asbestos level close ~z cerr
would cost a thousand dollars ($1000). Given what you have learned
about the size of the risk, do you think you would decide to carr^
out asbestos reduction measures?
definitely would reduce the level
probably would reduce the level
cannot decide what to do
probably would NOT reduce the level
definitely would NOT reduce the level
8. If someone lived in the home with your imaginary test result and did
nothing about the asbestos, what do you think are the chances that
s/he would eventually have some illness due to asbestos? (Please
check the box that comes cl'osest to your opinion.)
[ ] no chance
[ ] .1 chance
( ] .2 chance
r ] .5 chance
f 1 chance
in 1,000
in 1,000
in 1,000
in 1,000
2 chances in 1,000
5 chances in 1,000
[ ] 10 chances in 1,000
[ ] 20 chances in 1,000
[ ] 40 chances in 1,000
[ ] 80 chances in 1,000
[ J 120 chances in 1,000
[ ] 250 chances in 1,000
[ ] don't know
For questions 9-13 below please check the box that best indicates your
impression about asbestos. For example, in the sample item below, if
your impression was that asbestos was very often found in homes, but hot
always, then you would check the box shown below.
Sample Question: How frequently is asbestos found in homes?
never [ ] [ ] [ ] [ ] [ ] [J(] [ ] always
9. How easily can asbestos levels be reduced?
very easy
to reduce [ ]
C ] [ 1 [ ] [ ] [ J
very difficult
[ ] to reduce
10.
Is asbestos a risk that people can think about reasonably calmly,
or' is it one that people have great dread for—on the level of a
gut reaction?
calm
reaction [ ]
[ ] [ ]
] [ ]
[ J
dread
[ ] risk
11
If someone became sick because of asbestos, how likely is it that
the illness would be fatal?
certain not
to be fatal [ ]
certain
[ ] to be fatal
12
13
Is asbestos a risk that is new and novel or old and familiar?
old [ ] [ ] [ ] [ ] [ ] [ ] [ ] new
To what extent are the risks from asbestos the result of natural
processes, or are the risks man-made?
all man-made [ ] [ ] [ ] [ ] [ ] [ ] [ ] all natural
-------
Fcr classification purposes, please tell us:
a. Your sex: [ ] male [ ]• female
b. Your age:
c. How much school have you completed?
[ ] some elementary school [ ] finished 2-year college
[ ] finished elementary school [ ] finished 4-year college
( ] some high school [ ] some graduate study
[ ] finished high school [ ] graduate degree
[ ] some college
d. Have you tested your own house for either of these hazards:
Asbestos [ ] no [ ] yes
Radon [ ] no [ ] yes
e. Have you heard of any government standard or "action level" for
asbestos in'homes?
[ ] no
[ ] yes > What do you think is the government action level?
Level is: [ ] don't know
f. Have you heard of any government standard or "action level" for
radon in homes?
[ 1 no
[ ] yes > What do you think is the government action level?
Level is: [ ] don''t know
THANK YOU FOR YOUR TIME AND HELP! If you want a copy of some of the
other brochures we're testing/ please fill out the mailing label and
include it in the envelope when you mail back the questionnaire.
Cond.
-------
Cover Page for nacon Questionnaire
:"£ STATE UNIVERSE O? NEW jEPSc -'
RUTGERS
COOK Ccnege • Deoartmen of H^nco Ecoicg,
PO Box 231 • New Brunswick • New jersey 05903 • 201 v32-yi53
Dear New Jersey Resident:
Thank you for talking with us on the phone and for agreeing to
take part in our project. At Rutgers we are developing different
information brochures for people who test their hones for radon. The
feedback questionnaire you return will show us whether the brochure
we sent you is helpful.
There are no right or wrong answers. We need to get your
reactions and your . opinions to evaluate the brochure. All your
answers are kept confidential. The code number on the feedback
questionnaire is only used to show us which questionnaires have been
returned, so we don't call and remind people who have already mailed
back their answers.
DIRECTIONS
Pretend that you have just had your house tested for radon. The
testing company tells you that you have a reading of
__ picocuries per liter on your first floor and you are
trying to decide whether you should do anything about it. Read
the "Test Brochure" to help you interpret your imaginary test
result and then fill out the questionnaire. FEEL FREE TO REFER
TO THE BROCHURE WHEN ANSWERING THE FEEDBACK QUESTIONS. When you
have finished, mail the questionnaire back to us in the envelope
i
that we have provided. The Test Brochure is yours to keep.
THANK YOU VERY MUCH FOR YOUR HELP.
Neil D. Weinstein, Professor
Peter M. Sandman, Professor
Paul M. Miller, Project Director
-------
Cover °age for Asoest:s Questionnaire
•~E 5'ATE 'J'NiVE^S^v .jr N=vV jE'
-------
If you continued to live in the here with your test result arc iiir.'t
do anything about the asbestos, what do you think are the chances that
you would eventually have some illness due to asbestos? (Even though
you may feel uncertain, please circle an answer to tell us what
impression you got from the brochure.)
no very unlikely moderate likely very certain
chance unlikely chance likely to haopen
How do you think you would feel if your own home actually had the asbestos
level found by the imaginary test? (Please circle one answer in each
row.)
7. not at all slightly concerned very extreirely
concerned concerned concerned concerned
8. not at all slightly frightened very extremely
frightened frightened frightened frightened
9. What is your impression of how difficult it is to reduce the asbestos
level if houses have a problem?
[ ] very difficult
[ ] fairly difficult
[ ] fairly easy
[ ] very easy
10. Let's say that reducing your asbestos level close to zero would cost a
thousand dollars ($1000). Given what you have learned about the size
of your present risk, do you think you would decide to carry out
asbestos reduction measures?
[ ] definitely would take measures to reduce the asbestos level
[ ] probably would take measures
[ ] cannot decide what to do
[ ] probably would NOT take measure
[ ] definitely would NOT take measures
11. If you continued to live in the home with your test result and didn't
do anything about the asbestos, what do you think are the odds that
you would eventually have some illness due to asbestos? (Please put a
check in the box that comes closest to your opinion.)
[ ] C 1 C ] 'M C ] t ] t 1 C ] C ] t )
no chance 1 chance 1 chance 1 chance certain no
in 1,000 in 100 in 10 (100T.) idea
(O.U) (1%) (10%)
-------
12. At what asbestos level (in your main living area) do you think you
would feel satisfied, so that you would not spend more money trying to
aet the level even lover?
[ ] 5 fibers/1
[ ] 6 fibers/1
[ ] 7 fibers/1
[ ] 8 fibers/1
[ ] 10 fibers/1
[ ] 20 fibers/1
] NO asbestos
] 0.5 fibers/1
] 1 fiber/1
j .2 fibers/1
1 3 fibers/1
] 4 fibers/1
For classification purposes, please tell us:
a. Your sex: [ ] male [ ] female
b. Your age:
c. How much school have you completed?
r ] some elementary school
] finished elementary school
] some high school
] finished high school
] some college
[ ] finished 2-year college
[ ] finished 4-year college
[ ] sore graduate study
[ ] graduate degree
d. Prior to receiving our brochure, how much had you read about asbestos:
f ] very little [ ] moderate amount (at least one
[ ] small amount information booklet or a
magazine article)
[ ] a lot
e. Have you tested your own house, condominium or apartment for asbestos:
[ ] no -• •
f ] yes
f. Have you heard of any government standard or "action level" for
asbestos in hones:
[ ] no
[ j yes > what do you think is the government action level:
Level is: [ ] don't know
THANK YOU FOR YOUR TIME AND HELP!
If you want a copy of sane of the other brochures we're testing, please
fill out the mailing label and include it in the envelope when you mail
back the questionnaire.
-------
APPENDIX B
EXPERIMENT II BROCHURES, FORMATS, AND QUESTIONNAIRES
Experiment II had four conditions for asbestos only — Base, Displaced, High Test Magni-
tude, and High Risk. The Appendix begins with the complete four-page brochure for the-
High Risk condition, with the format on the fourth page, followed by the Base, Displaced,
and High Test Magnitude format pages. (The first three pages were identical for all
conditions.) One question on the response questionnaire varied depending on the condi-
tion. The Appendix therefore includes one complete four-page cover letter and question-
naire (used for the Base and Displaced conditions), followed by the two variations of one
page used for the High Risk and High Test Magnitude conditions.
117
-------
COMPLETE BROCHURE
HIGH RISK CONDITION
Test Brochure*
2/90
BASIC ASBESTOS INFORMATION
WHAT IS ASBESTOS?
Asbestos is a mineral fiber found in rocks. There are several
kinds of asbestos fibers, all of which arc fire resistant and not easily
destroyed by natural processes. Because of its desirable qualities,
asbestos has been used in a wide variety of products including
appliances, ceilings, wall and pipe coverings, floor riles, and some
roofing materials.
IS ASBESTOS DANGEROUS?
Although asbestos has many benefits for humans, it is also a very
dangerous mineral. Breathing airborne asbestos fibers has been shown
to cause: (1) Asbestosis - a serious lung disease which can lead to
disability and death; (2) Lung cancer - a disease that is incurable and
almost always fatal; and (3) Mesothelioma - cancer of the lining of the
lung or abdominal cavities. The greater the exposure to asbestos, the
more likely it is that one of these serious diseases will develop.
Workers who handle or come into contact with asbestos on a daily
basis are open to the greatest health risks.
There is no level of exposure to asbestos fibers that is completely
safe. The greater the concentration of asbestos, the greater the risk.
HOW DOES ASBESTOS AFFECT US?
The danger arises when asbestos fibers are released from the product
or material. These fibers are so small that they cannot be seen. They
can float in the air for a long time and can pass through the filters of
normal vacuum cleaners and get back into the air. Once inhaled,
asbestos fibers can become lodged in tissue for a long time. After many
years cancer or asbestosis can develop.
Cigarette smoking and asbestos together are especially hazardous.
Exposure to asbestos plus smoking gives an even greater risk of lung
cancer than adding the risk from smoking alone to the risk from
exposure to asbestos alone.
Asbestos found in "friable" materials is most dangerous.
Friable materials are materials that can be crumbled, pulverized,
* Because ihis is an experimental brochure, please check with
oihcr authorities before taking any actions in your home.
-------
or reduced to powder by hand pressure. Asbestos insulation sprayed on a
ceiling is an example of a friable material. In contrast, vinyl asbestos floor
tile is not usually fr.able. The asbestos fibers are firmly bound or sealed
into the tile and can be released into the air only if the die is cut, ground, or
sanded.
WHERE IS ASBESTOS LIKELY TO BE FOUND IN THE HOME?
There are several areas in the home where asbestos problems are most
likely io arise. These include:
* Wall construction materials and pipe insulation, especially those
dating between 1920 and 1972. (This includes materials found in
and behind plaster or wallboard and in paper tape.)
* Friable ceilings in buildings built or remodeled between 1945
and 1978.
* Material found on stoves and furnaces such as insulation and
millboard and door gaskets.
Other asbestos-containing products that you may find in the home include:
* Patching compounds and textured paints. (Since the use of
asbestos in these products was banned in 1975, you are most
likely to find it when sanding or scraping old or damaged
material in older houses.)
* Vinyl floor tiles and flooring.
* Roofing, shingles, and siding.
* Appliances with asbestos-containing parts or components, such
as toasters, broilers, slow cookers, dishwashers, refrigerators,
ovens, ranges, clothes dryers, electric blankets, and popcorn
poppers. (Unless broken or misused, most appliances with
asbestos are safe. There has been a general decline in the use of
asbestos in these appliances during recent years. If asbestos is still
used, it is in pans which will probably not release fibers during use.)
Having significant amounts of asbestos in the home is not rare. Many old
homes in New Jersey could create health problems for residents because of
materials that may release asbestos fibers into the air.
HOW CAN I TELL IF I HAVE ASBESTOS IN MY HOME?
The manufacturer of a product may be able to tell you, based on the
model number and age of the product, whether or not it contains asbestos.
People who have frequently worked with asbestos (such as plumbers, or
building or heating contractors) can often tell you whether or not material
contains asbestos by looking at it
Problems may occur in the home where asbestos-containing materials
are worn, damaged, or exposed to the air. If you have ceiling or wall
material that is crumbling, or you are preparing a major renovation which
will expose material contained behind a wall, you should havethe material
-------
analyzed to determine if it contains asbestos. Laboratory analyses range from
about S20 to S40 per sample. Several samples may be required to gain an
accurate determination of asbestos content
If you suspect that you.have a problem, you may also want to have an air
sample taken to measure the amount of asbestos fibers circulating inside your
home. To collect the sample, a laboratory will send a technician to your home.
A pump is used to draw air from the room into a filter that will trap the
asbestos. An electron microscope is used to count the number of fibers crapped
in the filter. It takes about six hours to collect the sample and costs between
SI00 and $400, depending on the laboratory and technique used. The results of
the test can be reported in units of "fibers per deciliter of air" (one deciliter is
one-tenth of a liter), abbreviated as f/dl. This unit tells how much asbestos
there is in one deciliter of air.
WHAT SHOULD I DO IF I HAVE AN ASBESTOS PROBLEM?
If you discover that you have an asbestos problem, the best thing to do is to
contact a contractor who has experience in the proper procedures for repairing
and removing asbestos. There are special guidelines for handling
asbestos-containing materials. You should avoid drilling, scraping, sanding,
brushing, sweeping or vacuuming asbestos materials. This will disturb tiny
asbestos fibers, make them airborne, and increase the risk of breathing them. It
is highly recommended that you hire an experienced contractor or get
professional advice if you are thinking of doing the work yourself. A
contractor will seal off the contaminated area from the rest of the house and
workers will use protective clothing and a special respirator while they are
handling the asbestos. Using improper techniques can make an existing prob-
lem much worse by contaminating the entire house. For more information
about identifying, testing, handling, and fixing asbestos problems call the
N. J. Department of Health toll-free at 1-800 624-2376.
INTERPRETING YOUR TEST RESULT:
Use the three columns on the next page to interpret the
imaginary test result we gave you. First, look down the column on
the left, headed "Asbestos Level," and find the number nearest to
your test result.
Next, move to the middle column, the one with the heading
"Extra Cancer Deaths." The number in this column tells you how
many people are expected to get cancer out of every 1000 people
who live in a home with the same asbestos level as yours.
Finally, move over to the right hand column, the one titled
"Comparison to Smoking Risk." It tells you how many cigarettes a
day a person would have to smoke to have the same cancer risk
as living with your asbestos level.
-------
INTERPRETING YOUR TEST RESULT:
Asbestos
level
(f/dl)
Extra
Cancer
Deaths
(Out of 1000
People)
Comparison to
Smoking Risk
— 1500
750
350
150
75
35
15
7.5
3.5
Over 700 in 1000
Over 700 in 1000
700 in 1000
300 in 1000
150 in 1000
70 in 1000
30 in 1000
15 in 1000
7 in 1000
6 packs/ day
1/2 pack/ day
3 cigarettes/ day
-------
INTERPRETING YOUR TEST RESULT:
Asbestos
level
071)
Extra
Cancer
Deaths
(Out of 1000
People)
Comparison to
Smoking Risk
— 1500
750
350
150
15
35
15
7.5
3.5
300 in 1000
150 in 1000
70 in 1000
30 in 1000
15 in 1000
7 in 1000
Sin 1000
1.5 in 1000
.7 in 1000
6 packs/ day
1 1/2 packs/ day
6 cigarettes/day
1 cigarette/day
D
1/4 cigarette/day
------- |