!PA-680/4-75-002b
1AY 1975
Environmental Monitoring Series
ENVIRONMENTAL RADIOACTIVITY LABORATORY
INTERCOMPARISON STUDIES PROGRAM
1975
^eo "X
NATIONAL ENVIRONMENTAL RESEARQH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
US ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Develop-
ment, U. S. Environmental Protection Agency, have been
grouped into five series. These five broad categories
were established to facilitate further development and
application of environmental technology. Elimination of
traditional grouping was consciously planned to foster
technology transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL MONI-
TORING series. This series describes research conducted
to develop new or improved methods and instrumentation
for the identification and quantification of environ-
mental pollutants at the lowest conceivable significant
concentrations. It also includes studies to determine
the ambient concentrations of pollutants in the environ-
ment and/or the variance of pollutants as a function of
time or meteorological factors.
EPA REVIEW NOTICE
This report has been reviewed by the National Environ-
mental Research Center-Las Vegas, EPA, and approved for
publication. Approval does not signify that the contents
necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorse-
ment or recommendation of use.
Document is available to the public for sale through
the National Technical Information Service, Springfield,
Virginia 22161.
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EPA-680/4-75-002b
May 1975
ENVIRONMENTAL RADIOACTIVITY
LABORATORY INTERCOMPARISON STUDIES PROGRAM
1975
by
Quality Assurance Branch
Technical Support Laboratory
National Environmental Research Center
Las Vegas, Nevada
ROAP Number 21BEK
Program Element 1HA327
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
IT;
U. 5 ~:
ED«SQ$,
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PREFACE
Quality assurance is an integral part of any viable environmental
monitoring activity. The primary goals of the U.S. Environmental Pro-
tection Agency's (EPA) quality assurance program are to improve and
document the credibility of environmental measurements. To achieve
these goals, quality assurance is needed in nearly all segments of
monitoring activities and should cover personnel, methods selection,
equipment, and data handling procedures.
Five major functions, each essential to an effective quality
assurance effort, comprise EPA's quality assurance program.
• Promulgation of standardized methods of
measurement
• Distribution of standard reference materials
• Issuance of guidelines and procedures
• Training and technical assistance
• Evaluation and certification of monitoring
activities
This manual has been prepared to assist laboratories involved with
environmental radiation measurements in developing and maintaining a
quality control program and documenting the precision and accuracy of
their data. All EPA monitoring programs are requested to make use of
this document in planning their own radiation measurements and in
assisting the States in carrying out radiation monitoring activities.
Comments concerning the utility of this document, along with any
suggestions for possible changes and revisions, are welcomed. Questions
on matters related to quality assurance of environmental measurements
in various fields should be directed to the following person(s):
Air Pollution
Mr. Thomas Clark
Methods Standardization and Performance Evaluation Branch
Quality Assurance and Environmental Monitoring Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
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Water
Mr. John Winter, Chief
Quality Assurance and Laboratory Evaluation Branch
Methods Development and Quality Assurance
Research Laboratory
National Environmental Research Center
Cincinnati , Ohio 45268
Pesticides
Mr. Jack Thompson, Chief
Chemistry Branch
Pesticides and Toxic Substances Effects Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
Radiation
Mr. Arthur N. Jarvis, Chief
Quality Assurance Branch
Technical Support Laboratory
National Environmental Research Center
Las Vegas, Nevada 89114
Periodically, manuals and documents will be issued which provide
guidelines to be followed in all phases of monitoring activities. Use
of these guidelines throughout the Agency will enable a uniform
approach to be established within EPA which ultimately can be imple-
mented at the State level. This should permit a significant improve-
ment in the validity and reliability of environmental data collected
throughout the Nation.
The implementation of a total and meaningful national environment-
al quality assurance effort cannot succeed without the full support of
all monitoring programs. Your cooperation is appreciated.
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CONTENTS
Page
Preface ii
The Laboratory Intercomparison Studies Program 1
Types of Environmental Samples Distributed 3
Analysis of Data 7
Participation in the Laboratory Intercomparison
Studies Program 14
Statistical Calculations 15
Tables
1. Summary of Cross-Check Programs 5
2. Cross-Check Sample Distribution Schedule 6
3. Laboratory Precision: One Standard Deviation
Values for Various Analyses 9
4. Sample Analysis and Report of Participant's Data ... 10
Figures
1. Results Reporting Form 8
2. Control Chart 12
IV
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THE LABORATORY INTERCOMPARISON STUDIES PROGRAM
Environmental measurements of radiation are made daily by many
Federal, State, local, and private agencies. The data from these
measurements are used for a wide variety of purposes including assess-
ment of health effects, the establishment of standards and guides, and
for enforcement activities. It is therefore imperative that the pre-
cision and accuracy of the data be assured in order that policy de-
cisions concerning environmental quality are based on valid and com-
parable data of known reliability.
In order to attain this goal, an Agency-wide quality assurance
program has been implemented within the U.S. Environmental Protection
Agency (EPA). In the area of radiation, quality control responsi-
bilities have been assigned to the Quality Assurance Branch at the
EPA's National Environmental Research Center-Las Vegas which carries
out a program designed to encourage the development and implementation
of quality control procedures for sample collection, laboratory
analysis, and data handling and reporting.
A major objective of this program is to assist laboratories in-
volved in environmental radiation measurements to develop and maintain
both an intralaboratory and an inter!aboratory quality control program.
In part, this is accomplished through an extensive laboratory inter-
comparison study ("cross-check") program involving environmental media
(milk, water, air, food, soil, and gases) and a variety of radio-
nuclides with activities at or near environmental levels.
Simulated environmental samples, containing known amounts of one
or more radionuclides, are prepared and routinely distributed to all
laboratories upon request. These laboratories perform the required
analyses and return their data to the Quality Assurance Branch for
statistical analysis and comparison with a known value and analytical
1
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values obtained by other participating laboratories. A report and a
control chart are returned to each participant. The program thus
enables each laboratory to document the precision and accuracy of its
radiation data, identify instrumental and procedural problems, and to
compare its performance with that of other laboratories.
Each laboratory making environmental measurements for radiation
should have an internal quality control program in operation to insure
that all instrumentation is calibrated and functioning, and that
analytical procedures are being carried out properly. Such a program
includes continual monitoring of instrumentation, the plotting of
instrument control charts, frequent analysis of replicate samples to
check precision, and the regular measurement of samples to which known
amounts of activity have been added to check the accuracy of systems.
Participation in a laboratory intercomparison does not automati-
cally assure the precision and accuracy of a laboratory's data and
should not be considered as a substitute for a continuous quality con-
trol program within a laboratory. Intercomparison data may be useful
for documenting precision and accuracy and helping to indicate instru-
mental or procedural problems. Participation in intercomparison
studies is useful in augmenting a laboratory's quality control program
and serves as a check on its internal quality control program.
You are encouraged to have your laboratory participate in the
cross-check program of the Quality Assurance Branch of the NERC-LV's
Technical Support Laboratory, or to expand its participation if you
wish to do so.
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TYPES OF ENVIRONMENTAL SAMPLES DISTRIBUTED
The current laboratory intercomparison studies program covers the
analysis of a variety of media containing various levels of radio-
activity. These include:
Milk: Four-liter milk samples containing potassium, strontium-89,
strontium-90, iodine-131, cesium-137, and barium-140 are
distributed on a bimonthly basis.
Water: Water containing several different mixtures of radioactive
materials is included in the cross-check program.
• Four-liter samples for the analysis of gross alpha and
gross beta activity are sent to participating labora-
tories bimonthly.
• Four-liter samples containing chromium-51, zinc-65,
cobalt-60, ruthenium-106, cesium-134, and cesium-137
are distributed bimonthly for analysis of gamma
emitters.
• Sixty-mi 11iliter samples for tritium analysis are dis-
tributed on a bimonthly basis.
• Four-liter water samples containing plutonium-239 are
shipped to laboratories during February and August of
each year.
• Four-liter samples of well water containing radium-226
are distributed in January, May, July, and November.
Air: Air filters, with optional two-inch or four-inch diameters,
are sent out on a quarterly basis for gross alpha, gross
beta, plutonium-239, cesium-137, and strontium-90 analysis.
-------
Soil: Hundred-gram soil samples, containing plutonium-239, will
be distributed twice each year.
Food: Three 4-liter food slurries containing strontium-89,
strontium-90, iodine-131, cesium-137, barium-140, and
potassium are sent to participants quarterly.
Urine: Urine samples (60-ml) containing tritium are shipped on a
quarterly basis.
Gases: Cylinders of air, containing krypton-85, are distributed
twice each year.
Sample size, approximate activity levels, type of analysis, and
other pertinent information concerning the cross-check samples are
summarized in Table 1. The distribution schedule is outlined in
Table 2.
A laboratory may participate in any one or all of the studies
described.
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ANALYSIS OF DATA
Each participating laboratory is expected to carry out three inde-
pendent determinations for each radionuclide included in a particular
cross-check study and to report its results on a form (Figure 1) pro-
vided with the sample.
Upon receipt of the reports from all participating laboratories,
the data are transferred to punch cards for computer analysis. As
indicated in the sample calculations, this analysis includes determi-
nation of the laboratory standard deviation, calculation of the nor-
malized range, normalized deviation, sample standard deviation, and
the grand average of all laboratories. The analytical precision values,
used as a basis for judging laboratory performance for specific nuclides,
are summarized in Table 3.
A report is generated containing data reported by participating
laboratories, listed according to their identity code, along with the
results of the analysis (Table 4). In addition, a control chart is
generated and reproduced for each radionuclide included in the sample
(Figure 2). The control charts are updated each time a laboratory par-
ticipates in a particular cross-check study, thus giving each laboratory
a continuous record of its performance.
A letter giving the known value for each radionuclide is mailed
to participants approximately two weeks after the report due date.
This is followed by a complete report which includes a copy of the,
computer printout and control chart.
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tf .,,.
U>Sl ENVIRONMENTAL PROTECTION AGENCY
I NATIONAL ENVIRONMENTAL RESEARCH CENTER
LAS VEGAS, NEVADA
QUALITY ASSURANCE BRANCH
Tritium in Urine
Cross-check Program
Laboratory ID
Contact Person
Collection Date 9-20-74 0400 hours PST
Analysis #1
Analysis #2
Analysis #3
NOTE: All results are in pCi/1 with background subtracted.
Total activity is less than 3500 pCi/1 3H.
Please send your results no later than October 18, 1974 to:
U.S. Environmental Protection Agency
National Environmental Research Center
Quality Assurance Branch (TSQ)
P.O. Box 15027
Las Vegas, NV 89114
Data not received by this date will not be included in the final report.
NOTE: Please do not report more or less
than three results per isotope.
Figure 1. Results Reporting Form
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Table 4. SAMPLE ANALYSIS AND REPORT OF PARTICIPANT'S DATA
NERC-LV TRITIUM IN URINE CROSSCHECK PROGRAM SEPTEMBER 1974
09/20/74 SAMPLE - A 3H
KNOWN-VALUE =
EXPECTED LABORATORY PRECISION (IS, 1 DETERMINATION) =
LAB
AN
CF
CF
CF
CM
CM
CM
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D
D
D
J
J
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P
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RESULT
NO DATA
3269
3522
3632
3261
3373
3362
NO DATA
3060
3060
3240
3255
3247
3294
NO DATA
3240
3340
3190
EXPERIMENTAL RNG ANLY
SIGMA (R + SR)
PROVIDED
186.1 .60
61.7 .19
PROVIDED
103.9 .30
25.1 .08
PROVIDED
76.4 .25
AVERAGE
3474
3332
3120
3265
3257
3273
357
PCI/L
PCI/L
NORMALIZED DEVIATION
(GRAND-AVG) (KNOWN)
.9
.2
-.1
-.2
1.0
.3
-.7
-.0
-.1
EXPERIMENTAL SIGMA (ALL LABS) =
149
GRAND AVERAGE =
3290
10
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Explanation of terms in Table 4:
Title:
Column 1:
Column 2:
Column 3:
Columns 4
and 5:
Column 6:
Column 7:
Column 8:
Bottom of
Chart:
Program name, sample collection date, sample code
letter, analysis type, known concentration of radio-
nuclide, expected standard deviation of analysis -
single determination.
Laboratory identification code (A, B, C, etc.).
Laboratory results (0-25 results listed down column).
Is (standard deviation) of the experimental results.
Normalized range value in "mean range + standard error
of the range" (R + OR) units for comparability. (See
Statistical Techniques for Quality Control of Environ-
mental Eadioassay., AQCS Report Stat-1, November 1964,
pages 4-8.) (S^ = OR for printing purposes.)
Average value.
Normalized deviation from the grand average value of
all laboratories expressed in ay\ units.
Normalized deviation from the known value expressed in
a|v| units.
Is experimental error of all laboratories, and the
grand average of all laboratories.
11
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NERC-LV TRITIUM IN URINE CROSSCHECK PROGRAM
LAB D 3H
NORMALIZED DEVIATION FROM KNOWN
1973
1974
C9
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J FMAMJJAS ONDJ FMAMJ JA SOND
1973
NORMALIZED RANGE
1974
R+3
R+2
R+1
1+0
n
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1 . i
CL
WL
J FMAMJJASONDJ FMAMJJASOND
Fiqure 2. Control Chart
-------
Explanation of terms used in the control chart (Figure 2).
Title: Name of program, laboratory code letter, and type
of analysis.
Upper Graph: "Normalized deviation from known versus the month
of analysis." [The 95.0% (y ± 2aw) and the 99.7%
(y ± SOM) confidence levels were chosen as the
warning levels and control limits respectively.]
Lower Graph: "Normalized range values (R + op) versus the
month of analysis." [The 97.5% (R + 2aR) and
^100% (R + SCJR) confidence levels were chosen as
the warning levels and control limits respec-
tively.]
13
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PARTICIPATION IN THE LABORATORY INTERCOMPARISON STUDIES PROGRAM
Any laboratory involved in, or concerned with, environmental
radiation monitoring and surveillance, is eligible to participate in
any one or all of the cross-checks described. Moreover, dependent upon
personnel available and their workload, a laboratory may elect to re-
ceive samples on a less frequent basis than indicated on the distribu-
tion schedule (Table 2).
To become a participant in the laboratory intercomparison studies
program, complete one of the forms included at the end of this publica-
tion and return to:
U.S. Environmental Protection Agency
National Environmental Research Center
Quality Assurance Branch (TSQ)
P.O. Box 15027
Las Vegas, NV 89114
Should the laboratory require additional types of cross-check
samples at some later date, a second form indicating the samples
desired should be submitted.
14
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STATISTICAL CALCULATIONS
To illustrate the computations performed by the computer, example
calculations are given using data for three actual samples analyzed at
one laboratory (Laboratory D, see Table 4).
The experimental data are listed and the mean, range, and the
experimental sigma are computed. These statistics provide measures of
the central tendency and dispersion of the data.
The normalized range is computed by first finding the mean range,
R, the control limit, CL, and the standard error of the range, OR.
The normalized range measures the dispersion of the data (precision)
in such a form that control charts may be used. Control charts allow
one to readily compare past analytical performance with present per-
formance. In the example, the normalized range equals 0.3 R which
falls inside the upper warning level, R + 2a^. The precision of the
results is acceptable.
The normalized deviation is calculated by computing the deviation
and the standard error of the mean, am. The normalized deviation
allows one to readily measure central tendency (accuracy) through the
use of control charts. Trends in analytical accuracy can be determined
in this manner. For this example, the normalized deviation is -0.7
which falls within the upper and lower warning levels. The accuracy of
the data is acceptable.
Finally, the experimental error of all laboratories, the grand
average, and the normalized deviation from the grand average are cal-
culated in order to ascertain the performance of all the laboratories
as a group. Any bias in methodology or instrumentation may be found
from these results.
15
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EXAMPLE CALCULATIONS (Laboratory D Data, see Table 4)
Experimental data:
Known value = y = 3273 pCi 3H/liter urine on September 24, 1974
Expected laboratory precision = a = 357 pCi/liter
Laboratory Sample Result
D xj 3060 pCi/liter
D x2 3060 pCi/liter
D x3 3240 pCi/liter
Mean = x
N
? Xi
x = ~ = ^O = 3120 pCi/liter
11 O
where N = number of results
Range = r
r = [maximum result - minimum result)
= |3240 - 3060| = 180 pCi/liter
16
-------
Experimental sigma = s
s =
(3060)2 + (3060)2 + (3240)2 _ (3060 + 3060 + 3240)*
O
= 103.9 pCi/llter
Normalized range = wR +
Mean range = R
R = d2a where d2 = 1.693 for N = 3*
= (1.693)(357)
= 604.4 pCi /liter
Control 1 imit = CL
CL = R + 3a
R
where D4 = 2.575 for N = 3*
= (2.575)(604.4)
= 1556 pCi/liter
Standard error of the range = OR
OR = 1/3 (R + 3aR - R)
= 1/3 (D4R - R)
= 1/3 (1556 - 604.4)
= 317.2 pCi/liter
* Rosenstein, M., and A. S. Goldin, Statistical Techniques for Quality
Control of Environmental Radioassay, AQCS Report Stat-1, U.S. Depart-
ment of Health, Education and Welfare, PHS, Nov 1964
17
-------
wR
= 1R
= 1R +
- wR
CTR
for r > R
wR + XCTR = wR + OCR
= wR
H R
_Rj
" 180
604.4J
= 0.30 R
for r < R
since 180 < 604.4
Normalized deviation of the mean from the known value = ND
Deviation of mean from the known value = D
D = x - y
= 3120 - 3273
= - 153 pCi/liter
Standard error of the mean = am
°m = 7T
357
= 206.1 pCi/liter
ND =
- 153
206,1
= - 0.7
18
-------
Experimental sigma (all laboratories) =
st
162639133 -
14
= 149 pCi/liter
Grand average = GA
N
x<
N
49345
15
= 3290 pCi/liter
Normalized deviation from the grand average = ND'
Deviation of the mean from the grand average = D'
D' = x - GA
= 3120 - 3290
= - 170 pCi/liter
ND' = ?!
°m
- 170
" 206.1
= - 0.3
19
-------
-------
SUBJECT: Participation in Intercomparison Studies Program
TO: U.S. Environmental Protection Agency
National Environmental Research Center
Quality Assurance Branch (TSQ)
P.O. Box 15027
Las Vegas, NV 89114
Please include our laboratory in the cross-check studies we have
indicated below. All samples are to be shipped to:
Contact Person
Title
Laboratory
Address
AEC License
and/or
State License
Type(s)
Number(s)
NOTE: When requesting participation in a study containing either
nuclear byproducts or special nuclear materials, a copy of
the AEC license(s) must accompany the request.
If your laboratory prefers participation other than the pub-
lished frequency, please indicate months samples are desired,
FREQUENCY
SAMPLE TYPES
Milk: Sr, Y
Water:
Gross a, B
Y
SH
239pu
226Ra
>-
i
1C
h-
:z
o
s:
s
[j
n
n
n
>~
i
C£
UJ
H-
D;
-
— i
_i
<
^D
^
^
a
D
a
a
a
n
SAMPLE
Air Fil
Gross
239pu
Soil:
Diet:
Urine:
Gases:
FREQUENCY DESIRED
I
1 ^^ >—
fy* ^- |
LJJ 2: _i
C^ >"— * — 1
<
ter: 2" dia. T|
«, 3 [J [_1 C or
/I II _l • 1 1
ana4 dia- D
239Pu n r^
sr, Y nan
3H nan
85Kr Q f]
I certify this laboratory is authorized to receive the samples
requested.
Signature
Date
Title
-------
-------
SUBJECT: Participation in Intercomparison Studies Program
TO: U.S. Environmental Protection Agency
National Environmental Research Center
Quality Assurance Branch (TSQ)
P.O. Box 15027
Las Vegas, NV 89114
Please include our laboratory in the cross-check studies we have
indicated below. All samples are to be shipped to:
Contact Person
Title
Laboratory
Address
AEC License
and/or
State License Number(s)
Type(s)
NOTE: When requesting participation in a study containing either
nuclear byproducts or special nuclear materials, a copy of
the AEC license(s) must accompany the request.
If your laboratory prefers participation other than the pub-
lished frequency, please indicate months samples are desired,
FREQUENCY
SAMPLE TYPES
Mi
Ik: Sr, Y
>-
i
•_n
I—
^z.
o
•SL
CD
^]
>~
_i
D;
UJ
I—
en
~
— i
_i
<
ID
z:
^
D
Water:
Gross a, B
Y
3H
239pu
226Ra
n
n
n
n
n
n
D
n
D
n
n
n
n
n
n
n
p
FREQUENCY
SAMPLE
Air Fil
Gross
239pu
Soil:
Diet:
Urine:
Gases:
TYPES
ter:
a, B
239pu
Sr, Y
3H
85Kr
>-
— i
C£
UJ
1 —
C£
cC
IO
__
n
n
n
i
_i
<
rD
•z.
•z.
—
i
_i
— i
^
eC
2" dia. n
rn °r
/in i • t ~
n 4 dia-Q
n
n
n
n
I certify this laboratory is authorized to receive the samples
requested.
Signature
Date
Title
-------
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-680/4-75-002b
3. RECIPIENT'S ACCESSION NO.
4 TITLE AND SUBTITLE
Environmental Radioactivity Laboratory Intercomparison
Studies Program, 1975
5. REPORT DATE
May 1975
6. PERFORMING ORGANIZATION CODE
1 AUTHOR(S)
Quality Assurance Branch
Technical Support Laboratory
8. PERFORMING ORGANIZATION REPORT NO.
N/A
9. PERFORMING ORG '\NIZATION NAME AND ADDRESS
National Environmental Research Center
U.S. Environmental Protection Agency
P.O. Box 15027
Las Vegas, NV 89114
10. PROGRAM ELEMENT NO.
1HA327
11. CONTRACT/GRANT NO.
in-house report
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC 20460
13. TYPE OF REPORT AND PERIOD COVERED
interim (1975)
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The U.S. Environmental Protection Agency's intercomparison studies program for
laboratories involved in environmental radiation measurements is described. The
types of environmental samples distributed, the analysis required for each sample,
the distribution schedule, and the statistical analysis and reporting of results
are discussed. Instructions and application forms are included for laboratories
desiring to participate in the program.
This document is not a research report. It is designed for use by laboratories
participating or desiring to participate in this quality assurance program.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
qua! ity assurance
quality control
quantitative analysis
radioactivity
statistical quality control
c. COS AT I Field/Group
07 05/14 04
13. DISTRIBUTION STATEMENT
Release unlimited
(NERC-LV, NTIS)
19 SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
24
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
,V GPO 693-414
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