I UNHID STATES EIWIEQNMimm FECWM^TTO
WASHINGTON D.C. 2M60
Miy 22, 1992
OIUCEOF
THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
EPA-SAB-RAC-LTR-92-010
Honorable William K. Meilly
Administrator
U.S. Environmental Protection Agency
401 M Street S.W.
Washington, D.C. 20460
SUBJECT: Review of the draft revised Homebuyer's and Seller's GuMe to
Radon
Dear Mr. Rally:
In its January 10, 1992 memorandum to the Science Advisory Board, the Office of
Radiation Program asked the Radiation Advisoiy Committee to "review the scientific basis
of the real estate testing protocol options" proposed in its December 23, 1991'draft revised
document, Homebuyer's and Seller *$ Gwde to Radon, In addition to the Guide, an Appendix
on non-interference controls (methods to discourage tampering), options for real estate testing
protocol, and a national profile of the real estate testing protocol options were transmitted
with the memorandum. At the Committee's pubEe meeting February 10-12, 1992, staff of
the Office of Radiation Programs (01P) briefed the Committee on the scientific basis for the
Guide and distributed an analysis of misclassification results by season for single short-term
measurements,
The Committee believes mat all radon remediation decisions should be based on
estimated exposure to individuals. Therefore, the Committee has for some time
recommended a year-long integrated radon concentration measurement, taken in the lowest
lived-in space, because this measurement most accurately reflects the annual average radon
concentration in a home (exposure also depends on the time an individual spends in a
particular area). However, the Committee realizes that the best option is not currently the
most realistic option for real estate transactions where decisions may be made in matters of
days or weeks.
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The Agency's analysis recognizes that, in comparison to long-term tests, short-term
tests for radon will greatly increase the numbers of false negatives and false positives relative
to the EPA recommended action level of 4 pCi/L. The problem of false indicators is greatest
near the action level. False negatives will result in failure to mitigate where mitigation is
desirable, whereas false positives will result in homes being mitigated even though the annual
average radon concentration is already below EPA's recommended 4 pCi/L action guideline,
However, in proposing real estate test protocols, the Agency must also consider a number of
practical concerns that are not strictly part of the science. For example, deliberate tampering
with the test devices or otherwise interfering with the test will render it invalid. A testing
protocol that is too complicated or costly wiE discourage testing. In addition, in warm
weather, home sellers without air conditioning arc unlikely to comply with requests to close
up their houses for several days,
Overall, the Committee recommends that the Agency develop real estate testing
protocols that are consistent with the recommendations in the Citizen's Guide to Radon, but
because the home-owner and home-seller have different motivations M radon testing, the real
estate testing protocols should not be constrained by those adopted for the Citizen's Guide.
Where the protocols differ from those in the Citizen's Guide, the Agency should provide the
public an explanation for this difference.
In reviewing the proposed protocols (Attachment 2), the Committee considered that
radon concentrations in homes vary with location within the home; with heating, ventilating,
and air conditioning use patterns of the occupants; and over time. Radon concentrations vary
with time of day, with weather, and by season. Radon measurement methods vary in their
precision, ability to provide an integrated sample over time, susceptibility to tampering, and
time periods for which they may be usefully deployed. The Committee also considered
statistical analyses presented by the Agency at the February 10-12 meeting (Attachment 3)
that address the percentage of false negatives and false positives under a variety of
circumstances. In some cases, the Committee found that the data and analyses made
available to it were insufficient to make decisions about the protocols and the Committee's
recommendations therefore include the professional judgement of the Committee,
The Committee considered five protocols proposed by the Agency (Attachment 2).
Options A and D consist of two simultaneous short-term tests; for Option A these tests are
made in the lowest area that could be lived in (lowest "livable") and for Option D the tests
are made in the lowest area the buyer plans, to live in. Option E combines Option A plus
Option D. Options B and C each consist of a single short-term test if the result is below 4
Pci/L with follow-up testing only if the first test result is above 4 pCi/L; for Option B the
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test is made in the lowest area that could be Eved in and. for Option C the test is made in the
lowest area the buyer plans to live in.
Options A and D, and likewise options B and C, differ in the location at which
measurements will be made should the buyer decide to utilize a presently un-used basement
as part of the living space of the home. The buyer's desire may not be known, or a potential
buyer might change his or her plans. Because Options A and B measure radon
concentrations in the lowest area that could be lived in, they are essentially independent of
the buyer's intentions but such measurements are likely to overestimate annual average radon
exposures if these areas are infrequently used. If the testing protocol requires that
measurements be made in the lowest livable area (Options A and B), and this area is not
occupied by the buyer, then the possibility of false positive results increases, so that a
significant number of such homes may be mitigated even though the annual average radon
concentration to which the occupants are exposed is in fact below EPA's recommended 4
pCi/L action guideline. Taken together, ORP's "Msclassification of Results By Season for
Single Short-Term Measurement Analysis," and the graphs in "Attachment A: Options for
Real Estate Testing Protocol" show that, on a national average, 65% false positives could
occur and that for 41 % of the false positives the annual average radon concentrations is
estimated to be less than 2 pCi/L.
Testing in the lowest livable area does minimize the number of false negative test
results. Also the radon concentrations in the basement may be more precisely measured
because the concentration is higher and more stable than on the first floor, but the Committee
does not believe these footers provide an overall advantage if the concentration measured is
not the average concentration to which the home occupants are exposed.
Options B and C assume that annual average radon concentrations can be estimated,
and thus potential mitigation decisions can be made, on the basis of a single short-term
measurement if the first test result fell below 4 pG/L. Option E, which requires two
simultaneous tests on both the first floor and the basement, appears unnecessarily complex
and more expensive than the others. The separate values that will be obtained for basement
and first floor may provide opportunity for dispute between the potential buyer and the
seller, and averaging all measurements might be misleading.
Two simultaneous tests run side-by-side would improve the precision of the
measurement, applicable to the time period of the measurement Two sequential tests
improve the accuracy of estimating an annual average concentration by increasing the time
period over which measurement is made. In the real estate transaction context, however, the
sequential tests would usually be made close together in time during the same season of the
year; therefore, the resulting improvement in accuracy would likely be small. The material
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presented to the Committee did not provide a conclusive basis for choosing between
simultaneous and sequential testing. The Committee was not able to quantitatively compare
the precision and accuracy of these alternative measurement techniques. Committee
members were concerned that if tests ire done sequentially, a high initial test result might
encourage—or be perceived as encouraging-interference with the second test, but this
problem could be avoided by not reporting the data until both tests have been made.
Recommendations
Encourage longer testf whenever possible. Short-term testing is, by its very nature,
subject to considerable uncertainty if used to represent long-term average exposures, even
when done with great precision. Both false positive and false negative results will occur at a
higher frequency than for long-term tests properly performed. The Homebuyer's and Setter's
Guide needs to make these facts abundantly clear to aE parties involved in real estate
transactions, and that with a short-term test a seller may weE incur remediation costs that
could have been avoided if a reliable long-term test were performed. Likewise, a buyer
cannot be assured purchase of a home that is below the EPA guideline annual average radon
concentration, especially if the reported short-term test results are near this action level (4
pCi/L),
If short-term testing is chosen. In the situation of real estate transactions as described
to the Committee, when there may not be time for a long-term test, the Committee
recommends the following:
a) Conduct short-term testing at the lowest level of the home that is finished in a
manner suitable for occupancy, whether or not the seller lives in that area.
This strategy would provide the buyer with the option of using that area as
part of the livable area of the house with the knowledge that it had been tested
for radon. Short-term testing is not recommended in unfinished areas that are
currently not suitable for sustained occupancy. Thus testing, and possible
resulting mitigation, would not be required for areas that will not be used
without renovation. If the buyer elects to finish or renovate the area for
occupancy, then it should be his or her responsibility to test to determine the
need for mitigation before remodeling. Testing will also be appropriate
subsequent to remodeling to ensure that none of the changes resulted in
increased radon levels.
b) Two measurements should be conducted if passive short-term integrating
monitors are used. A single measurement is not sufficient, and should be
discouraged. Simultaneous measurements would improve the precision of the
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measurement. Sequential measurements should likely give a better
representation of the seasonal average. Measurements over a sufficient time
period should be required to minimize the effects of the daily and day-to-day
variations io, radon concentrations. Each measurement should span at least two
days with an appropriate device or preferably longer. Time periods longer
than two days are likely to provide better estimates of the annual average
concentrations, but the Committee was not able to quantify this expected
improvement from the data provided.
c) A non-passive continuous radon monitor could also be used, with data
collection over a time period sufficient to minimize the effects of the daily and
day-to-day variations in radon concentrations. Again, the time period should
be at least two days and preferable longer.
d) Employ methods to reduce or eEmlnate inadvertent or deliberate interference
with the measurement devices(s) or violation of closed house conditions to
ensure the integrity of the results,
e) The revised Homebuyer's and Setter's CMdz to Radon should very carefully
portray 4 pCi/L as the recommended EPA action level for an annual average
concentration and that a 4 pCi/L short-term test result does not necessarily
translate to an annual average concentration of this magnitude.
Alternative Approaches. The Committee recommends that the Guide address, as
another option, long-term testing of the home after the sale has been completed. Although
many buyers and sellers wish to finalize commitments at the time of the sale and not have
the process continue following transfer of title, the significant advantages of having the time
to do more accurate long-term testing may be an overriding consideration in some
transactions. Possible methods of implementation of such post-sale testing include the
establishment of an escrow account which could be used to pay for any necessary mitigation
costs or be returned to the original seller depending on the long-term test result* Another
possibility would be a home warranty or "radon insurance" type arrangement, where the
long-term testing and any resulting mitigation would be conducted after the sale of the home
and at no further monetary expense to the homebuyer. To the extent that it can, the Agency
should encourage such approaches as a means of providing long-term and therefore more
scientifically defensible means of testing radon concentrations in houses,
Research Recommendation. The Committee believes that, as the Agency revises and
improves its recommendations regarding radon testing methodologies, it should conduct
studies directed toward improving the analysis of both the precision and accuracy of the
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various measurement methods, testing protocols, and interpretive procedures. These efforts
should include more data on day-to-day and season-to-season variability for a variety of
radon concentrations. It is also important to investigate how increasing integration time
improves the accuracy of short-term test results in comparison to estimating the annual
average radon concentration. Such research should include various testing techniques and a
wide spectrum of houses and testing variables. The Committee is aware of at least two
recent studies-conducted in Florida and in New Jersey—whose results appear to pertain to
some of these questions,
We appreciate having been given the opportunity to conduct this particular review,
We request that the Agency respond formally to the scientific advice provided herein,
particularly in regard to the Committee's concern that short-term testing may not provide an
adequate estimate of the long-term concentrations.
Sincerely,
Dr/Raymond C. Ixjehrr^hlir Dr. Oddvar F. Nygaaffl,
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U.S. ENVIRONMENTAL MO1ECI1ON AGENCY
SGEEfCE ADVISORY BOARD
RADIAHON ADVISORY COMMITTEE
Roster
CHAIRMAN
Dr. QddvarF. Nygaard, Division of Biochemical Oncology, Department of Radiology,
University Hospitals of Cleveland, Cleveland, OH
MEMBERS
Dr. Stephen L. Brown, ENSR Consulting & Engineering,- Alameda, CA
Dr. Kelly H. Clifton, Department of Human Oncology and Radiology, University of
Wisconsin Clinical Cancer Center Madison, WI
Dr. James E. Martin, University of Michigan, School of Public Health, Ann Arbor, MI
Dr. Genevieve M. Maianoski, The Johns Hopkins University, 'School of Hygiene and
Public Health, Baltimore, MD
Dr. H. Robert Meyer, C.N.S.I., Harrisburg, PA
Dr. Richard G. Sextro, Building Ventilation and Indoor Air Quality Program, Lawrence
Berkeley Laboratory, Berkeley, CA
Mr. Paul G. Voilleque, MJP Risk Assessment, Inc., Idaho Falls, ID
Dr. James E. Watson, Jr., Department of Environmental Sciences and Engineering,
University of North Carolina, Chapel Hill, NC
SOOBMCB ADVISORY BOARD STAFF
Mrs. Kathleen W. Conway, Designated Federal Official, Science Advisory Board (A-101F),
U.S. Environmental Protection Agency, Washington, DC
Mrs, Dorothy M. Clark, Staff Secretary, Science Advisory Board (A-101F), U.S.
Environmental Protection Agency, Washington, DC
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REAL ESTATE TESTING PROTOCOL OPTIONS
National Profile
NOTE: A single short-term test
rtiuld be used In options A, D,
until.
PROTECTIVENESS
ACCURACY
(bused on 4 pCi/L action level)
OTHER
Testing Option A:
Two simultaneous short-term
tests in lower area that could be
lived in (liveable).
True positives - 5.0%
• False negatives -13%
Number of homes fixed -142%
- "Unnecessary" mitigations - 83,
million homes
- Fixers without beisefils - 3.4 M
homes (mostly with basements)
Provides quick results
• Applies to any potential
homebuycr, regardless of living
patterns
Consistent with testing and
fixing before the transaction
Testing OpHon B:
One short-term lesl followed \>y
a confirmatory short-term test in
lowest area that could be lived in
(liveable).
> True positives - 5.1%
- False negatives -1.2%
• Number of homes fixed -13.9%
•Unnecessary* mitigations - 8.0
M homes
Fixers without benefits - 3.2 M
homes (mostly with basements)
Two-step process more time
consuming
• Applies to any potential
homebuycr regardless of living
patterns
• Consistent with testing and
fixing before the transaction
i
o
en
c
w
Testing OiXion C:
One short-term test fallowed by
a confirmatory short-term test in
lowest area the buyer plans to
live in (living or liveable).
True positives - 4.7%
False negatives * 1.6%
Number of homes luted - 93%
"Unnecessary mitigations* -
4.1M homes
Fiiefs without benefits - 0,9
thousand homes (mostly with
basements)
Consistent with Draft "Citizen's
Guide"
• Two-step testing process, more
time-consuming.
• Testing or fixing would be
contingent on buyer's
preference for lowest living
area {implies watting until time
of transaction)
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Enclosure 3
C-Z£3
MISCLASSmCATION RESULTS BY SEASON TOR SINGLE SHORT-TERM 'MEASUREMENT ANALYSIS
OPTION
Lowest Livable
Level
Winter
2 Day Charcoal
60-90 Day AID
Summer
2 Day Charcoal
60-90 Day AID
Lowest Llvcd-In
Level
Winter
2 Day Charcoal
60-90 Day AID
Surcirma-
2 Day Charcoal
60-90 Day AID
Correct
Cltssifl cations
1S,S%
914%
92,6%
SS
95,6%
910%
Error Rate
is*
6,6%
7.4%
9.3%
8.1% •
4.4%
5.0%
Ftbe(-)
(over 3i! horns
testing)
0.8%
2.0%
2J%
1.1*
23%
Faiss(-)
(over all true
positives)
105%
17.6%
27.0%
14.9%
203%
39,1%
473%
(over all horns
testing)
13.7%
llJft
4.6%
4.6%
S.4%
\M
(over ill
positive tests)
67.5%
46.0%
50.0%
52.4%
25.0%
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This report has been written as a part of the activities of the Science Advisory Board, a
public advisory group providing extramural scientific information and advice to the
Administrator and other officials of the Environmental Protection Agency. The Board is
structured to provide balanced, expert assessment of scientific matters related to problems
facing the Agency. This report has not been reviewed for approval by the Agency and,
hence, the contents of this report do not necessarily represent the views and policies of the
Environmental Protection Agency, nor of other agencies in the Executive Branch of the
Federal government, nor does mention of trade names or commercial products constitute a
recommendation for use.
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