ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 8 

Document Title:

Use of Coworker Dosimetry Data For 

External Dose Assignment

Document Number: ORAUT-OTIB-0020

Revision: 01

Effective Date: 10/07/2005

Type of Document: OTIB

Supersedes: Revision 00

Subject Expert: Steven E. Merwin

Document Owner

Approval: Signature on File Approval Date: 10/04/2005

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Concurrence Date: 10/04/2005

Richard E. Toohey, Project Director

Approval: Signature on File Approval Date: 10/07/2005

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

FOR DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE, REPLACE THE PRIOR 

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-OTIB-0020 Revision No. 01 Effective Date: 10/07/2005 Page 2 of 8

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

12/29/2004 00 New technical information bulletin to provide general information to 

allow ORAU Team dose reconstructors to assign doses to workers at 

DOE sites who have no or limited monitoring data, based on site 

coworker external dosimetry data. First approved issue. Initiated by 

Steven E. Merwin.

10/07/2005 01 Provides clarifications and updates to reflect recent OCAS guidance. 

Approved issue of Revision 01. Training required: As determined by 

the Task Manager. Initiated by Steven E. Merwin. 
Document No. ORAUT-OTIB-0020 Revision No. 01 Effective Date: 10/07/2005 Page 3 of 8

TABLE OF CONTENTS

SECTION TITLE PAGE

1.0 Purpose ...................................................................................................................................4

2.0 Background..............................................................................................................................4

3.0 General Approach.................................................................................................................... 5

4.0 Applications And Limitations ....................................................................................................5

5.0 References .............................................................................................................................. 6

6.0 Development Of Site Coworker Data Sets And Distributions.................................................... 6

7.0 Application of Site Coworker Percentile Doses And A Comparison to 

 Maximum Likelihood Doses ...................................................................................................7

LIST OF TABLES

TABLE TITLE PAGE

7-1 Comparison of K-25 external coworker penetrating doses (rem) modified

 to account for missed dose from ORAUT-OTIB-0026 to doses calculated

 using maximum likelihood approach.......................................................................................... 8 
Document No. ORAUT-OTIB-0020 Revision No. 01 Effective Date: 10/07/2005 Page 4 of 8

1.0

Technical Information Bulletins (TIBs) are general working documents that provide guidance 

concerning the preparation of dose reconstructions at particular sites or categories of sites. They will 

be revised in the event additional relevant information is obtained. TIBs may be used to assist the 

National Institute for Occupational Safety and Health in the completion of individual dose 

reconstructions.

PURPOSE

In this document the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act of 2000 (42 U.S.C. § 7384l(5) and (12)).

The purpose of this Technical Information Bulletin (TIB) is to provide general information to allow 

ORAU Team dose reconstructors to assign doses to workers at DOE sites who have little or no 

individual monitoring data, based on site coworker external dosimetry data. This TIB is to be used in 

conjunction with separate TIBs or other approved documents that provide site-specific coworker data.

2.0

The ORAU Team is conducting a series of coworker data studies to permit dose reconstructors to 

complete certain cases for which external and/or internal monitoring data are unavailable or 

incomplete. For the purpose of this document, coworkers are considered to be workers at a site 

(potentially grouped by work location, job description, or other appropriate category) whose measured 

doses are considered representative of those received by one or more claimants with no individual 

monitoring data. 

BACKGROUND

Cases without individual external monitoring data may fall into one of several categories, including:

• the worker was unmonitored and, even by today’s standards, did not need to be monitored 

(e.g., a non-radiological worker).

• the worker was unmonitored, but by today’s standards would have been monitored.

• the worker may have been monitored but the data are not available to the dose reconstructor.

• the worker may have partial information, but the available information is insufficient to facilitate

a dose reconstruction.

Some cases with little or no individual monitoring data can be processed in the absence of completed 

coworker studies, most notably those falling under the first category listed above. For example, nonradiological workers with no potential for workplace radiation exposures may be assigned on-site 

ambient doses. Even some cases falling under the second and third categories above do not require 

coworker studies, e.g., radiological workers who may in some cases be assigned reasonable upper

limits provided that the total probability of causation (POC) is less than 45%. Regarding the last 

category above, if sufficient information is available, a prorated dose could be assigned in certain 

circumstances. 
Document No. ORAUT-OTIB-0020 Revision No. 01 Effective Date: 10/07/2005 Page 5 of 8

3.0

The general approach to applying coworker data for cases with little or no individual external 

monitoring data is to assign either 50th or 95th percentile doses with the intent that the doses assigned 

represent, but do not underestimate, the doses that would be assigned had the employee been 

monitored. As described in section 6.0, the percentile doses include consideration of missed dose. 

This is necessary because the coworker data are intended to represent the results for unmonitored 

workers had they been monitored, and missed doses are assigned to null monitoring results for 

monitored workers.

GENERAL APPROACH

Site-specific coworker data sets containing 50th and 95th percentile penetrating and non-penetrating 

doses are provided in separate, site-specific TIBs. In general, the 50th percentile dose may be used 

as a best estimate of a worker’s dose when professional judgment indicates the worker was likely 

exposed to intermittent low levels of external radiation. The 50th percentile dose should not be used 

for workers who were routinely exposed. For routinely exposed workers (i.e., workers who were 

expected to have been monitored), the 95th percentile dose should be applied. For workers who are 

unlikely to have been exposed, external on-site ambient dose should be used rather than co-worker 

doses. The site-specific TIBs also provide information on the sources of the site data, validation of 

the data, and conversion of the data into annual doses to be applied in dose reconstructions.

The coworker doses presented in the site-specific TIBs shall be treated as constant values. However, 

they do not include all factors that must be applied by the dose reconstructor in order to assign doses. 

Specifically, site-specific adjustments based on technical considerations (e.g., dosimeter bias) must 

be incorporated by the dose reconstructor based on the site Technical Basis Documents (TBDs). 

Additionally, organ dose conversion factors based on OCAS-IG-001 must be applied; for likely 

compensable or likely non-compensable cases, they shall be applied in the same manner in which

they are applied for monitored employees, and otherwise they shall be applied as a triangular 

distribution.

4.0

In parallel with the development of site-specific TIBs that document the external coworker data sets to 

be used in dose reconstructions, cases not yet completed are screened to identify those cases 

requiring external coworker data to facilitate case processing. As described previously, some cases 

with little or no individual monitoring data have been processed using methods not dependent on 

coworker data. Cases identified as requiring coworker data shall be processed as described in 

Section 7.0. 

APPLICATIONS AND LIMITATIONS

Some workers are concerned that their dose records are not accurate because they were encouraged 

or instructed by a supervisor not to wear their badges (dosimeters), or they were not given badges 

while doing jobs that could have resulted in exposures sufficient to exceed an administrative or 

regulatory dose limit. If this concern is expressed by a claimant verbally in the CATI interview or in 

written correspondence, the dose reconstructor should try to determine if this could have happened by 

examining the dose records and considering the workplace conditions, potential source terms, and 

incident reports. In cases in which the dose reconstructor believes this could have happened, it may 

be necessary to modify the dose reconstruction and/or perform additional research.
Document No. ORAUT-OTIB-0020 Revision No. 01 Effective Date: 10/07/2005 Page 6 of 8

5.0

1. NIOSH (National Institute for Occupational Safety and Health), External Dose Reconstruction 

Implementation Guideline, Rev. 0, OCAS-IG-001, Office of Compensation Analysis and Support, 

Cincinnati, Ohio, 2002.

REFERENCES

2. ORAUT (Oak Ridge Associated Universities Team), ORAUT-OTIB-0026, External Coworker 

Dosimetry Data for the K-25 Site, Rev 00, May 31, 2005.

3. ORAUT (Oak Ridge Associated Universities Team), ORAUT-RPRT-0032, Historical Evaluation of 

the Film Badge Dosimetry Program at the Y-12 Facility in Oak Ridge, Tennessee: Part 1 – Gamma 

Radiation, Rev 00, April 13, 2005.

6.0

External dosimetry data for DOE sites are potentially available from several sources. These include 

the Center for Epidemiologic Research (CER) databases maintained by Oak Ridge Associated 

Universities (ORAU), the Comprehensive Epidemiologic Data Resource (CEDR) databases 

maintained by the Department of Energy, other data sets maintained by the Department of Energy, 

and data maintained by the sites themselves. Additionally, claimant data submitted by DOE sites to 

NIOSH in response to requests for the purposes of this dose reconstruction project provide a useful 

subset of site-wide data.

DEVELOPMENT OF SITE COWORKER DATA SETS AND DISTRIBUTIONS 

Development of site-specific data summaries and distributions involve a careful examination of the 

various data sources with the objective of identifying the most complete and accurate data set 

available. Prior to the analysis of the selected data and the development of summary statistics and 

dose distributions, a sampling of the data are compared to claim-specific data submitted to NIOSH by 

the DOE sites. This comparison helps verify the accuracy and completeness of the site data selected 

for use in coworker studies since the data submitted to NIOSH are often more detailed than the sitewide data sets (e.g., individual badge data are typically provided to NIOSH, while the site-wide data 

often represent annual summarized data). The comparison also provides information needed to 

adjust the site-wide data sets to account for missed dose, partial year data, etc. Should significant 

issues arise during the course of this comparison that shed doubt on the accuracy or completeness of 

the site data selected for analysis, additional evaluations will take place to ensure that a valid data set 

has been selected.

The specific data sets selected for a particular site and the rationale for their selection are 

documented in site-specific coworker data TIBs titled “External Coworker Dosimetry Data for the 

[DOE Site].” Prior to publication of these site-specific TIBs, the data are subjected to an independent 

and separately documented validation process. 

Once coworker data have been selected to represent a particular site, the data are analyzed for the 

purpose of developing annual 50th and 95th percentile doses.. Prior to calculating the percentile doses, 

however, the doses are adjusted to account for missed dose based on the badge exchange frequency 

and the dosimeter limit of detection (LOD). For example, the median annual reported dose might be 

zero at a particular site and in a particular year, but it would be inappropriate to assign a dose of zero 

as a median value because of the potential for missed dose, which must be included in the dose 

estimates to claimants.1

 Specifically, one-half of the maximum annual missed doses are added to the 

reported annual doses, except for reported positive doses in which case the maximum missed dose is

reduced by the dose corresponding to one badge exchange (because it is not possible that all 
Document No. ORAUT-OTIB-0020 Revision No. 01 Effective Date: 10/07/2005 Page 7 of 8

individual badge results were zero if a positive annual dose was reported). The 50th and 95th

percentile annual penetrating and shallow doses are then derived by ranking the data into cumulative 

probability curves and extracting the 50th and 95th percentile doses for each year. Additional details 

on the incorporation of missed dose in the site coworker data are provided in the site-specific TIBs.. 

The site-specific external coworker dosimetry data TIBs provide information on adjustments to the 

data that were necessary to develop annual doses and distributions for use in dose reconstructions. 

For example, partial-year dosimetry data included in the site data are extrapolated to provide annual 

values that represent the doses that would have been received for a full year of employment for all 

monitored employees. The objective is to provide data on the annual doses received by employees 

had they been monitored for a full year; dose reconstructors may then prorate the data for individual 

cases, as appropriate, to account for partial years of employment. 

7.0

Data are presented in Table 2 of each site-specific external coworker TIB as 50th percentile and 95th

percentile annual penetrating and non-penetrating doses for monitored workers. These doses, 

together with the application of dosimeter bias factors and organ dose conversion factors as 

described in Section 3.0, are intended to represent reasonable estimates of doses for workers who 

were not monitored. Also as described in Section 3.0, the 50th percentile doses are to be applied if the 

worker was likely exposed intermittently, and the 95th percentile doses are to be applied if the worker 

was likely exposed routinely. External on-site ambient doses are to be used instead of external 

coworker doses if the worker was unlikely to have been exposed. Doses shall be prorated, as 

appropriate, to account for partial years of exposure.

APPLICATION OF SITE COWORKER PERCENTILE DOSES AND A COMPARISON TO 

MAXIMUM LIKELIH0OD DOSES 

The approach described in this document is highly likely to result in a significant overestimate of 

external dose for unmonitored workers. This overestimate is attributable largely to the manner in 

which missed doses are applied to the coworker data sets (e.g., the use of nLOD/2 as prescribed in 

OCAS-IG-001 and described in Section 6.0 above). This overestimate is intentional, because the 

nLOD/2 approach is known to overestimate a monitored individual’s actual dose when the majority of 

monitoring results are null,1 and it would be inappropriate to treat unmonitored individuals who 

perhaps should have been monitored differently than individuals who happen to have been monitored. 

The extent to which the coworker data assigned according to the principles established in this 

document represent overestimates can be demonstrated by comparing site-specific percentile doses 

calculated according to these principles to doses calculated using the maximum likelihood approach. 

For example, Table 7-1 below compares the percentile doses for K-25 obtained from ORAUT-OTIB0026 (the site-specific coworker TIB2

) to doses calculated from the same data set but using the 

maximum likelihood approach (in the same manner as was performed for Y-12 film badge data3

). 

When comparing the values in Table 7-1, note that the LOD assumed for the maximum likelihood 

analysis was the same as given in ORAUT-OTIB-0026. Also, the calculated maximum likelihood 

doses for 1954-1958 were replaced with the value from 1959 because of an overwhelming number of 

individuals who had null results (i.e., the geometric mean values for this period were very low and the 

GSD values were very high), and the year 1945 has not been included in the table because the data 

were insufficient to facilitate a maximum likelihood analysis. Finally, the 95th percentile doses 

provided in the table for the maximum likelihood approach are calculated from the relevant geometric 

means (GMs) and geometric standard deviations (GSDs). 
Document No. ORAUT-OTIB-0020 Revision No. 01 Effective Date: 10/07/2005 Page 8 of 8

Table 7-1. Comparison of K-25 external coworker penetrating doses (rem) modified to account for 

missed dose from ORAUT-OTIB-0026 to doses calculated using maximum likelihood approach.

a

Year

ORAUTOTIB-0026

50th%

ORAUTOTIB-0026

95th%

Maximum 

Likelihood

Geometric

Mean (GM)

Maximum 

Likelihood

Geometric

Standard 

Deviation 

(GSD)

Maximum 

Likelihood

95th%

1946 0.805 1.455 0.046 6.383 0.970

1947 0.780 1.015 0.031 4.110 0.317

1948 0.780 1.264 0.013 7.321 0.344

1949 0.780 1.035 0.021 5.168 0.313

1950 0.780 0.841 0.006 5.518 0.100

1951 0.780 1.052 0.014 5.324 0.219

1952 0.780 0.951 0.017 4.150 0.177

1953 0.780 1.096 0.029 4.316 0.321

1954 0.780 0.913 0.037 4.783 0.486

1955 0.780 0.835 0.037 4.783 0.486

1956 0.780 0.855 0.037 4.783 0.486

1957 0.780 1.088 0.037 4.783 0.486

1958 0.780 1.049 0.037 4.783 0.486

1959 0.810 1.245 0.037 4.783 0.486

1960 0.791 1.154 0.032 4.497 0.379

1961 0.778 0.942 0.023 3.112 0.149

1962 0.780 0.824 0.015 2.423 0.064

1963 0.780 0.840 0.019 2.261 0.073

1964 0.780 0.841 0.016 2.208 0.059

1965 0.780 0.936 0.026 3.172 0.174

1966 0.780 0.952 0.022 3.744 0.193

1967 0.780 0.928 0.026 3.691 0.223

1968 0.780 0.906 0.006 7.157 0.153

1969 0.780 0.946 0.012 4.911 0.164

1970 0.780 1.041 0.012 6.720 0.275

1971 0.780 1.092 0.019 4.007 0.186

1972 0.779 1.034 0.026 2.822 0.143

1973 0.780 0.871 0.012 3.521 0.095

1974 0.835 1.065 0.079 2.416 0.337

1975 0.062 0.111 0.016 2.564 0.075

1976 0.060 0.149 0.045 1.643 0.102

1977 0.060 0.089 0.023 1.896 0.066

1978 0.052 0.136 0.040 1.746 0.100

1979 0.060 0.088 0.029 1.619 0.064

1980 0.060 0.145 0.064 2.051 0.209

1981 0.060 0.085 0.046 1.546 0.094

1982 0.060 0.060 0.046 1.478 0.087

1983 0.060 0.060 0.037 1.723 0.091

1984 0.060 0.060 0.032 1.787 0.083

1985 0.060 0.060 0.033 1.601 0.072