g UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
v WASHINGTON, D.C. 20460
EPA-SAB -RAC-S 9 -01 7
25 » 1989 Tur AQ
Honorable William K, Reilly
Administrator
U. S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
SUBJECTS Science Advisory Board Review of the Radon
Measurement Proficiency Program
Dear Mr. Reilly:
On September 23, 1987 the Director of the Office of
Radiation Programs revested that the Science Advisory Board
review the Radon Measurement Proficiency Program* The request was
referred to the Radiation Advisory Committee which formed the
Radon Measurement Subcommittee to conduct the review. The
Subcommittee held two open meetings. The first was held at the
Eastern Environmental Radiation Facility in Montgomery, Alabama
where the Radon Measurement Proficiency Program is housed on
January 26-27, 1988 and the second was held February 16-17, 1988
at Region I Headquarters in Boston, The Subcommittee also held a
writing session July 7, 1988 in Boston.
The Subcommittee addressed performance standards,
statistical methods, standard measurement protocols,
participant's procedures, blind tests of passive devices,
consensus standards and voluntary accreditation, and user fees,
The Subcommittee's recommendations include:
o development of separate objectives for devices or
methods used for screening, diagnostic measurements,
and exposure evaluations,
o consideration of different testing protocols for
passive devices and active measurements,
o design of the testing program to obtain independent
measurements from each device of method to be tested,
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r—
o
testing should be done blind, wherever practicable as
in the instance of passive measmfeaes.t.devices».and
strongly urgess the assignment of a full-tine
statistician to the program at least until it is well
established.
These and other recommendations are described in greater
detail in the attached report which was approved by the Executive
committee January 31, 1989,
The Science Advisory Board was pleased to participate in
this review and appreciates the opportunity to be briefed on the
activities of the Radon Measurement Proficiency Program. We
request that the Agency consider the advice contained here and
respond in writing to our recommendations.
Sincerely,
Raym
Executive Committee
William J. Setat|lr Chairman
wadi a
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J *
SCIENCE ADVISORY BOAMD
RADIATION ADVISORY COMMITTEE
RADON MEASUREMENT SUBCOMMITTEE
REVIEW
OF THE
OFFICE OF RADIATION PROGRAM'S
RADON MEASUREMENT PROFICIENCY PROGRAM
JANUARY 1989
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NOTICE
*
This report, has been written as 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 a balanced expert assessment of the
scientific issues related to problems facing the Agency, This
report has not been reviewed for approval by the agency and,
hence, the contents of the report do not necessarily represent
the views and policies of the Environmental Protection Agency,
nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
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U, S, ENVIRONMENTAL PROTECTION AGEKCY
SCIENCE ADVISORY BOARD
RADIATION ADVISORY COMMITTEE
RADON MEASUREMENT SUBCOMMITTEE
ROSTER
CBAIRMAM
Dr, Keith J, Schiager, 100 Orson-Spencer Hall, University of
Utah, Salt Lake City, Utah 843,12
MEMBERS/CONSULTANTS
Dr. Andreas George, Aerosols studies Division, Environmental
Measurements Laboratory, U,S, Department of Energy,
376 Hudson Street, New York, NY 10014
Dr, John Barley, Box M268, Hoboken, Hew Jersey 07030
Dr, Nan Laird, Department of Biostatistics, Harvard School of
Public Health, 677 Huntington Avenue, Boston, MA 02115
EXECUTIVE SECRETARY
Mrs, Kathleen W. Conway, Deputy Directorf Science Advisory Board/
A-101F, U.S. Environmental Protection Agency, 401 M street,
S.W., Washington, DC 20460
STAFF SECRETARY
Mrs. Dorothy M* Clark, Secretary, Science! Advisory Board, A-101F,
U.S. Environmental Protection Agency, 401 M Street, S.W.,
Washington, DC 20460
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TABLE OP COm|ai.TS
1.0 INTRODUCTION 1
2.0 SOMMABY OF RECOMMENDATIONS 2
2,1 Performance Standards 2
2,3 Statistical Methods 2
2,3 Standard Measurement Protocols 3
2.4 Participants1 Procedures 3
2.5 Blind Tests of Passive Devices 3
2.6 Testing of Active Devices and
Operators 3
2,7 consensus Standards and Voluntary
Accreditation 3
2,8 Adequate Program Support 4
3,0 DEVELOPMENT OF THE RADON MEASUREMENTS
PROFICIENCY PROGRAM (RMPP) 5
4.0 PROFICIENCY TESTING OBJECTIVES 7
4.1 Performance Standards 7
4.2 Statistical Methods 9
5,0 PROFICIENCY TESTING PROCEDURES 10
5.1 Standard Measurement Protocols 10
5.2 Participants' Procedures 11
5.3 Blind Tests of Passive Devices 11
5,4 Testing of Active Devices and
Operators 12
5,5 Radon Concentration standard 13
6.0 LONG-TERM PLANNING FOR THE RMPP 14
6.1 Consensus standards and Voluntary
Accreditation 14
6,2 Financial Support Needed for Adequate
Program 14
APPENDIX A - QUESTIONS SUBMITTED TO THE SAB
BY THE EPA
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ABSTRACT
The Radon Measurement Proficiency Program (RHPP) of the
Environmental Protection Agency's Office of Radiation Programs
was reviewed by the Science Advisory Board's Radiation Advisory
Committee (SAB/RAC). The SMPP was established in 1986 to provide
states and homeowners with some assurance that individuals and
organizations making radon measurements were, in fact, competent
to do so.
The SAB/RAC"s recommendations include: definition of
separate objectives for screening, diagnostic, and exposure
measurementsi the need for independent exposures when testing
devices submitted by participants! improved statistical support
for the program? blind testing for passive devices, and
consideration of establishing consensus standards, voluntary
accreditation, and user fees.
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1* 0 INTRODUCTION
Upon receiving a request from the Director of the Office of
Radiation Programs (ORP) the Science Advisory Board's Radiation
Advisory Committee formed a Radon Measurements Subcommittee to
review the Radon Measurements Proficiency Program (RMPP)» The
Subcommittee held a public meeting at the Eastern Environmental
Radiation Facility (EERF) of the EPA in Montgomery, Alabama on
January 26-27, 1988, The ESRP staff briefed the Subcommittee on
the RMPP and provided a detailed tour of the facilities used for
the RMPP and other programs conducted at th& EERF. On February
16-17, 1988 the Subcommittee met at EPA*s Region I Headquarters in
Boston, Massachusetts, Staff from the -National Bureau of
Standards (NBS) described the structure and functions of the NBS-
sponsored National Voluntary Laboratory Accreditation Program.
The Subcommittee met again in Boston on July 7, 1988, to
complete the writing of the report,
The Subcommittee considered the eight questions initially
posed by the EPA, as well as oral and written comments from
members of the public. The Subcommittee was pleased with the
open nature of the discussions with the EPA staff, and encouraged
by the fact that several of its recommendations have been adopted
and put into effect during round 5 of the proficiency testing,
even before this report was completed.
This report includes a brief summary Of the Subcommittee^
recommendations, a short history of the development of the RMPP,
followed by a discussion of the major topics considered by the
Subcommittee«
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2.0 SUMMARY OF RECQMMEMPaTIOHS
2.1 Performance Standards
The EPA may need to define separate objectives for devices
or methods used only for screening measurement and those that are
to be used for diagnostic purposes or exposure evaluations.
Different testing protocols should also be considered for
different categories of measurements, e.g. passive devices versus
active measurements, since a single measurement by one
measurement technique may carry greater significance than a
single measurement by another technique.
For passive devices used only for screening measurements, a
total uncertainty of a factor of 2 from the Jcnown test value at
the 90% confidence level is recommended. (See Sec, 4.1)
For passive devices used for doslmetry purposes, i.e. for
determining long-term average concentrations of radon or radon
progeny, a total uncertainty of 25% at the 90% confidence level
is recommended, (see Section 4.1)
For active devices used for screening, diagnostic or
dosimetric purposes, a total uncertainty of 25% at the 30%
confidence level is recommended, (see Section 4.1}
The EPA should design the testing program to obtain several
in
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2.3, Standard Measurement Protocols
f
The EPA should require that the information provided to the
client by the measurement company before and after the
measurement include clear statements of the purpose and proper
interpretation of the measurement. (See Section 5.1)
2 , 4 Participants f Procedures
Detailed procedures for exposing, evaluating (counting) and
calibrating each passive measurement device, as veil as the
methods used for calculating the radon concentration, should be
submitted with the application for admission to the proficiency
testing program, (See Section S.2)
For active measuring devices, the application should include
performance characteristics, calibration data, qualifications of
existing operators and details of the training program for future
or unia0jitj.fj.e5i operators, (See Section 5.2)
2,5 Blind Tests of passive Devices
The technical advantages of blind testing are sufficient
that the EPA is encouraged to adopt this system as soon as
feasible. (See Section 5.3)
2,6 Testing of Active Devices and Operators
The accepted use of grab sampling should be made conditional
on the use of good procedures by a qualified operator, (see
Section 5,4)
Active devices admitted to the RHP Program should be
certified as to their original calibration and continued
maintenance of that calibration. (See Section 5.4)
The qualification and/or training of the operators of active
devices must be retested or reviewed periodically* (See Section
5,4)
2.7 Consensus standards and voluntary Accreditation
The Subcommittee recommends that serious consideration be
given to establishing consensus standards and voluntary
accreditation procedures »
EPA should solicit the advice of various organizations that
establish consensus standards and voluntary accreditation
programs and should work toward converting the RMPP to such a
voluntary program as expeditiouely as possible.
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2*8 Adequate Program Support
r
The Subcommittee notes that a successful program will
require ade
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3.0 BEVBIOPMENT OF THE B&DQN MEASUREMENTS PROFICIENCY PROGRAM
EPA established the STOP in response to specific needs and
urgent requests far help from private laboratories and state
agencies* Concern, and even fear, among residents in areas where
high indoor radon concentrations had been found, and widespread
media coverage, led to numerous requests for radon measurements,
One of the immediate effects of the rapidly increasing demand for
radon measurements was the sudden appearance of numerous
individuals or companies offering radon measurements for a fee.
Since many of these individuals and companies had no previous
experience and no apparent qualifications related to indoor radon
measurements or evaluations, state agencies became rightly
concerned. The HIPP was established by the EPA as a prompt and
effective response to the growing problem,
The EPA contacted companies already involved in radon
measurements and encouraged them to participate in voluntary
proficiency testing. During these initial phases of the program,
it was necessary and normal to assist inexperienced companies
with measurement equipment and methods in order to assure the
development and availability of radon measurement capabilities to
meet the needs of the public. Companies who were able to
demonstrate adequate proficiency were listed in a "proficiency
report" distributed by the EPA to state agencies. For companies
providing radon measurement services, listing in the EPA's
proficiency report has become a de facto license to do business.
When the 1MPP was first initiated in early 1986 , the EPA
facilities were not adequate to conduct the program* The EPA
received assistance from the Environmental Measurements
Laboratory (EML) of the Department of Energy (DOE) in New ¥ork
City, where the first three rounds of proficiency testing were
conducted. The program was originally designed as a single test
process that would be repeated every three _ months with results
reported after each round of testing. Round one, conducted at
EML in April 1986, result in 35 participants listed," 85 were
listed after round three in November 1986, Recognizing the need
for larger and more versatile facilities for radon measurements
calibration and testing, the EPA built a new radon chamber at its
Eastern Environmental Radiation Facility (EEHFJ in Montgomery,
Alabama. Round 4 of the FMPP was conducted in the new chamber.
Round 5 was conducted during the summer of 1988.
Until the Subcommittee's review, EPA conducted all of the
proficiency testing in a batch mode. For logistical reasons,
all participants were required to submit devices or equipment for
testing within the same limited time interval, and all devices
were exposed to the same test atmosphere. T?he scheduling of
groups of similar devices for simultaneous testing has been
necessary to accommodate all participants with the existing
facilities and personnel.
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Calibration and testing of radon and radon progeny
measurement*devices and instruments requires a large-volume test
chamber containing very well-known radon and progeny
concentrations, chambers in which appropriate concentrations of
radon and other atmospheric constituents can be established and
maintained for extended periods of time exist in only a few
locations in the country, Even the few existing chambers were
not designed for testing of large numbers and varieties of
instruments and devices. In addition to the limited number of
test chambers, the very nature of the measurements restricts the
number of tests that can be accommodated in a single chamber. To
minimize uncertainties in the determination of the true average
radon concentration to which a device is exposed., it is desirable
to maintain a nearly constant radon concentration during the
testing period. The most commonly used radon measurement devices
are passive devices such as charcoal canisters and alpha track
detectors. Since most of the passive measurement devices require
exposure times of several days, it is preferable for most
applications to change the test atmosphere no more often than
weeKly,
The older of the two radon chambers at the EERF is quite
small (3,6 cubic meters) and access to the test atmosphere is by
means of only a few ports and a small panel* Air flows through
the chamber in a single pass, with radon being injected into the
incoming air and the outlet being exhausted to the outdoor
atmosphere. The new chamber has a volume of 42 cubic meters and
the air is recirculatad. Operators may walk into the new chamber
to install or exchange devices, an
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accumulated activity. The temperature and humidity of the
atmosphere in each chamber can. also be controlled, as can the
concentration of small airborne aerosols, i.e. condensation
nuclei.
4.0 PROFICIENCY TESTING OBJECTIVES
4,1 Performance standards
In order to demonstrate proficiency in making radon
measurements, participants and measurement devices must be tested
against an appropriate performance standard. The test procedure
must be appropriate to ascertain that the measurement device or
method does, in fact, meet the performance standard. The
following two questions posed by the EPA relate directly to the
performance standard and the means for demonstrating measurement
proficiency,
1PA Question li "The sample design was selected to insure
that a measurement company could, within 80 percent confidence,
identify a radon level as being greater than 4 pCi/L when in fact
the true level is 8 pCi/L» with a single measurement in a house.
Is the sample design now in use sufficient to meet SMPP program
objectives?
EPA Question 2i "EPA presently evaluates all devices by the
same measurement criteria, i.e. four measurement results must be
within 25 percent of the known chamber levels, EPA is
considering changing this criteria (sic) to obtain better
confidence in companies* abilities. Are the criteria outlined in
the BMPP Background Document scientifically sound?**
The Subcommittee agrees that, at concentrations of the same
order of magnitude as the EPA's present radon concentration
guideline (Rcc), a screening measurenent made with a passive
device solely to determine whether follow-up measurements are
warranted should produce a result within a factor of 2 of the
known test value almost all (e.g. 90%) of the time. Although a
possible error of a factor of 2 may appear to be excessively
large, the Subcommittee believes this degree of uncertainty is
acceptable for screeninet measurements because? (1) the
measurement protocol inherently introduces bias on the high side
of the true annual average concentration by more than a factor of
2, and (2) greater precision is unnecessary and could result
in increased costs to homeowners. Since many decisions regarding
radon mitigation may be based on a very small number of
measurements, the total uncertainty accepted in the measurement
should include the uncertainties of both bias and precision.
Since it is possible, under the revised procedures adopted
for round five, to deliver independent exposures to four devices
within a short time, this should be adopted as the minimum number
of measurements used for determining the acceptability of
performance. As discussed in Sec. 4.2f the acceptance criteria
originally proposed by the EPA, as well as those recommended by
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the Subcommittee, are based on statistical assumptions that
include independence of test measurements. As additional
facilities become available, this minimum number of samples could
be increased.
The Subcommittee strongly recommends against stating the
1MPP objectives in terms of the RCG for lifetime exposure,
i.e. 4 pCi/L, since the value becomes easily misinterpreted in
the context of the EPA's screening measurement protocol because
conditions in the house are selected deliberately to maximize the
radon concentration measured. Too much emphasis has been given
to this numerical value already and it is, unfortunately, being
interpreted as a hard and fast line between "safe" and "unsafe".
The 1FA should make a deliberate effort to discourage this
regulatory attitude toward radon measurements and mitigation,
To remain listed as proficient in measurements, a company
should be required to repeat its performance testing
periodically since performance may change over time due to factors
such as aging or new equipment, changes in operators and
analysts, etc. The exact interval for retesting should be
developed by the EPA, staff on the basis of cumulative performance
data and availability of facilities. The Subcommittee recommends
that participants that are new to the program be retested within
a year after first being listed as proficient. The retesting
interval could be increased after a participant has demonstrated
competence two or three times. In fact, the retesting interval
could easily be determined by the cumulative performance over the
past two or three tests on the basis of total error (accuracy
plus precision).
The Subcommittee considers that separate objectives, and
testing protocols may be appropriate for different types and
conditions of measurements. Because of the much greater cost,
sampling devices and methods that require an operator should
produce measurements of much better quality than can be obtained
by passive devices. Also, measurements made to determine the
need for, and/or extent of, mitigation activities should, because
of the potential cost to the homeowner, be of higher quality
than screening measurements made simply to determine if further
assessment is necessary. For passive devices that may be
distributed in various ways and returned by mail, the emphasis
should be placed on the consistency of instructions to the user,
handling, processing and reporting procedures. For active
devices that require an operator, both the adequacy of the device
and the competence of the operator should be evaluated.
Passive devices used for dosimetry, i.e. for determining
long-term average concentrations, should produce results that are
within 25 percent of the known test value at least 90 percent of
the time. This level of uncertainty is achievable with devices
currently available and should be required to assure homeowners
that mitigation costs are truly justified.
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The EPA should separate education and calibration assistance
from proficiency testing because the support activities
appropriate to the first two activities are not appropriate to e
objective testing program* A company, or individual operator,
should be allowed to participate in the RMPP only after
demonstrating understanding of the devices or methods intended
for use. and after some type of calibration has been performed.
Because of the lack of commercial calibration facilities EPA may
wish to continue to allow its chambers to be used for
calibrations, but this function should not be conducted
simultaneously with that of proficiency testing,
4*2 statistical Methods
The current EPA testing procedure, as stated in the program
reports ana as presented to the Subcommittee, requires that the
average of four measurements fall within 251 of the test chamber
value. The Subcommittee learned, however, that all four
measurements were normally made simultaneously in the same
atmosphere. Beyond the faot that the test measurements could not
be considered to be independent, thus invalidating the
statistical assumptions on which proficiency was based, the
Subcommittee was concerned that the procedure allowed too many
opportunities for unscrupulous participants to obtain the results
by means other than actual measurement.
The current performance criteria do not talce into account
uncertainties in both precision and accuracy in determining
proficiency. Changes to the procedures initially proposed by the
EPA would require a larger number of measurements and would
consider both precision and accuracy, but the measurements would
still not be independent and, consequently, the evaluation of
accuracy and precision would be incorrect. The dilemma lies
primarily in the batch mode of operation and in the small number
of truly independent measurements that can be made at any one
time.
Until additional testing facilities are available, the
Subcommittee recommends that the 1PA test fewer devices, if
necessary, but assure that tests are independent, i.e., at
different concentrations. Analysis of the results in previous
rounds which examine the within-round and between-round
variability within companies may help to answer questions about
sample sizes.
The statistical methods initially proposed for the EPA's
testing program are inappropriate in view of the physical and
economic constraints on the SERF testing facility. Developing a
set of statistical performance criteria and methods for running a
proficiency program requires commitment from professional
personnel with statistical expertise who can interact closely
with the EEAfs laboratory staff. Close interaction is necessary
to ensure that the statistician clearly understands the
objectives of the program and the limitations of the testing
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environment. Likewise, the laboratory staff needs input from
statisticians as to the appropriateness of the procedures front a
statistical point of view, The Subcommittee strongly recommends
that a statistician be assigned on a full-time, on-site basis
until the program is well established.
All of the performance criteria discussed above are based on
independent test measurements. To ensure this, the measurements
should be made of different chamber atmospheres, either at
different times in the same chamber or in different chambers.
The range of radon concentrations should represent values of most
interest but varied unpredictably, an
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that indicates only whether further measurements are desirable,
but gives no indication of actual annual exposure.
*
5.2 Participants' Procedures
EPA Question 6: "Within the parameters of the EPA
measurement protocols the RMP strives to follow each company's
standard operating procedures for testing, EPA does not set the
exposure period, the sampling period or the counting procedures.
Accommodating the large variety of standard operating procedures
causes logistical and operational problems during performance
test. Is this a reasonable and meritorious approach or should
EPA set standard RMP test procedures?"
The EPA should assure that a participating company cannot
claim that it failed a proficiency test because the test was not
conducted in accordance with the company's normal operating
procedure. To do this, the EPA should determine the minimum cumulative
exposure claimed to be detectable by the company, or the maximum
exposure time required for correct response, and assure that
tests are within these criteria. As long as the total exposure
of the device, i.e. picocurie-days per liter, exceeds the minimum
claimed to be detectable by the participant, and the decay or loss
of radon from a charcoal canister does not exceed the
normal amount, the participant's criteria will be satisfied.
The procedures for exposing, evaluating (counting) and
calibrating each passive measurement device, as well as the
methods used for calculating the concentration, should be
submitted with the application for admission to the proficiency
program. The EPA should evaluate and approved the procedures
before devices may be submitted for testing.
For active measurement devices, the application should include
performance characteristics and calibration data. The
qualifications of existing operators, and the training program
for future or unidentified operators, should be included with the
applications for active devices.
5.3. Blind Tests of Passive Devices
EPA Question 5: "Participants in the RMP include analysis
laboratories and distributors, i.e. middlemen operating between
homeowners and analysis companies. EPA intends to evaluate
distributors' performance in conjunction with, but different
from, the current chamber test process. For example, we are
proposing distributors undergo a yearly double blind test once
they have established themselves with a participating analysis
laboratory. We would not require these companies to participate
in further laboratory performance tests. This would minimize the
impact on these smaller companies and allow for more rigorous
testing of true laboratories. Is this reasonable?"
The blind test would be extremely valuable for monitoring
the performance of companies that distribute passive devices by
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mail or over the counter at retail outlets. It should be noted
that these blind tests are also valuable in assessing performance
of the primary measurement laboratories. However, some
situations cannot be monitored effectively by this technique,
e.g. companies that deliver passive devices directly to the home,
Because radon decays over time, there is also a time constraint
for receiving a passive device at a distant location, sending it
to the EERF for exposure, returning it to the surrogate homeowner
and then mailing it back to the company who may also have to mail
it to an analytical laboratory*
The advantages of blind testing are sufficient that EPA is
encouraged to adopt this system as soon as feasible. The
advantages of blind testing includet (1) the participant does
not know that the device is being tested, nor the exposure, (2)
the handling and reporting procedures are tested, as well as
the measurement itself, and (3) the procedures of the distributor
are tested as well as those of the processing laboratory, The
exposures of the passive devices could be carried out throughout
the year, allowing for a better distribution of effort with time.
5.4 Testing of Active Devices and Operators
SPA Question Ss "Currently, EPA supports the usage of grab
sampling as a screening measurement method by the inclusion of
the method in EPA measurement protocols and in the RHP* Given
the controversy in the scientific community surrounding its
reliability as a screening measurement, should the RHP continue
to categorize grab sampling as a screening method or should we,
for example, establish a new category for diagnostic methods?11
While grab sampling is more appropriate for diagnostic and
remediation purposes, it can be used as a valid screening method
particularly when prompt results are required. In spite of sane
controversy over its reliability, grab sampling is just one of
several short-term measurement techniques, which include
screening measurements of only a week or two with passive
devices. The advantages of on-site grab samples by a qualified
operator are that results and interrelations can be available
immediately without waiting for mail deliveries. The accepted use
of grab sampling should be Made conditional on the use of good
procedures for sampling, counting and calculation by a qualified
operator, since the method can be very easily abused.
Active monitoring devices for grab, continuous and
integrating sampling are used widely for both screening and
diagnostic purposes. Because these instruments are larger in
siie and in many cases require a trained operator for deployment
in the field, they require test criteria different from those
required by passive devices. The outcome of the measurement
depends largely on the individual operator and on the
original calibration of the instrument with sources procured from
the NBS or from a laboratory which, in turn, was cross calibrated
.with an NB5 radon and radon progeny reference atmosphere,
Submission of one instrument of one type to the EPA HMPP does
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not guarantee that all others of the same type will perform
satisfactorily. Several things can go wrong in the field
requiring specialized training for problem recognition. The
qualifications of the operators of active devices must be
reviewed periodically by EPA to ascertain the reliability of the
measurement results. Commercial devices admitted to the program
should be certified as to their original calibration and
procedural steps that will be taken by the operator to maintain
their original calibration.
The criteria should require the operator to maintain
documented quality control and measurement procedures for each
type of instrument. Air leakage around a filter and improper
counter efficiency are the most common areas where problems may
occur. The operator should be able to recognize them and take
proper action to correct them. The participant should submit
sampling procedures with a check list of operational procedures
to be followed before and after exposure. In summary, good
procedures for calibration, sample counting, calculation and
the qualifications of the operator must be the basis for
accepting a company into the RMPP.
EPA Question 3: "Some measurement devices can make Multiple
measurements in a 24-hour period while others can make a maximum
of two a day. Requiring the same number of samples for all types
of devices creates logistical and financial problems for EPA and
companies. Can any alternatives be recommended?"
Active devices the logistical problems of requiring multiple
measurements for devices that require manual reading and
resetting may be alleviated by applying testing procedures and
criteria different from those used for passive detectors.
Instruments and procedures for diagnostic purposes and exposure
measurements may require more restrictive criteria than those
required for screening measurements.
5.5 Radon Concentration Standard
EPA Question 7s "in the absence of a NBS radon standard, EPA
bases their radon chamber calibration procedure on radon values
established through national and international intercomparison
tests. Does this approach sufficiently substantiate the accuracy
of our chamber levels?"
The EERP uses both intercomparison tests and its own
laboratory standard for determining radon concentrations and
should continue to do so. It is generally accepted within the
scientific community that a valid laboratory standard for radon can
be prepared from an NBS radium solution primary standard.
Careful handling,, including opening the NBS vial, dilution and
preparing aliguots can give results that are accurate to within
one percent. Subsequent transfer of the radon gas to a
scintillation cell or ion chamber can be done within
approximately the same uncertainty. The accuracy requirements
for radon exposure chamber calibration are of the order of five
13
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percent, so a competent laboratory can calibrate its chamber in a
manner acceptable to users.
f
A potential source of error in the standard method of
calibrating scintillation cells from a standard radium solution
is in the transfer of moisture to the cells as a result of bubbling
air through the solution. Condensation in the cellst even when
so slight as to go unnoticed, can lead to substantial loss of
detection efficiency. One technique for preventing condensation
is simply to assure that the radon extraction operation is
performed in a room that is substantially cooler than the room in
which the cells will be stored for radon progeny ingrowth and
subsequently counted. Cooling of the bubbler flask in a
refrigerator prior to use may serve the same purpose. Such
precautions should be explicitly included in the calibration
procedure.
6.0 LONG-TERM PLANNING FOR THE RMPP
6.1 Consensus Standards and Voluntary Accreditation
Because of the recognized voluntary nature of the RMPP, the
Subcommittee recommends that serious consideration be given to
establishing consensus standards and voluntary accreditation
procedures. This approach would utilize a broad range of
existing expertise in measurement technology and in statistical
analysis through the participation of other agencies and industry
representatives. This approach has been used successfully for
many years by ANSI, ASME, ASTM, etc. It might be possible to
establish a program under, or comparable to, the National
Voluntary Laboratory Accreditation Program sponsored by the NBS.
6.2 Financial Support Needed for Adequate Program
The Subcommittee anticipates a continuing and increasing
demand for indoor radon measurements and the concomitant
requirements for calibration and testing, and encourages the EPA
to act now to assure the availability of the necessary facilities
and programs. It is essential that adequate funding be provided
for the RMPP without depleting support for other important EPA
radon programs. The Subcommittee strongly urges the SPA to
investigate all avenues to support the Radon Measurements
Proficiency Programs. One possibility is through user fees* It
should be noted the latter regard that industry presentatives
present at the meeting urged the use of such fees particularly
if it would help maintain the announced testing schedule. They
noted that the delay of several months in starting round 5 has
been damaging to companies who have invested in equipment but are
not able to conduct business until they are included on the KMPP
listing.
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