ORAU TEAM

Dose Reconstruction

Project for NIOSH

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

Page 1 of 9

Document Title:

Use of Coworker Dosimetry Data for External 

Dose Assignment

Document Number: ORAUT-OTIB-0020

Revision: 02 

Effective Date: 12/04/2008

Type of Document OTIB

Supersedes: Revision 01

Subject Expert(s): Matthew H. Smith

Site Expert(s): N/A

Approval: Signature on File Approval Date: 11/19/2008

Matthew H. Smith, Document Owner

Concurrence: Signature on File Concurrence Date: 11/19/2008

John M. Byrne, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 11/25/2008

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Concurrence Date: 11/20/2008

Kate Kimpan, Project Director

Approval: Signature on File Approval Date: 12/04/2008

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. 02 Effective Date: 12/04/2008 Page 2 of 9

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. 

12/04/2008 02 Approved revision that cancels changes from draft revisions 01 PC1-A and 01 PC-1-B. Section 3.0 was revised to include language 

developed during the review of this TIB by the Advisory Board 

Working Group on Procedures. Section 7.0, Attributions and 

Annotations was added. Editorial changes include an update of 

Section 1.0, Purpose, and movement of Section 6.0, References, to 

the end of the document with consequent renumbering of following 

sections. References updated as necessary. Incorporates formal 

internal and NIOSH review comments. Training required: As 

determined by the Task Manager. Initiated by Matthew H. Smith.
Document No. ORAUT-OTIB-0020 Revision No. 02 Effective Date: 12/04/2008 Page 3 of 9

TABLE OF CONTENTS

SECTION TITLE

1.0 Purpose ...................................................................................................................................

PAGE

4

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

3.0 General Approach....................................................................................................................4

4.0 Applications and Limitations.....................................................................................................5

5.0 Development of Site Coworker Datasets and Distributions....................................................... 5

6.0 Application of Site Coworker Percentile Doses and a Comparison to Maximum 

Likelihood Doses......................................................................................................................6

7.0 Attributions and Annotations ....................................................................................................8

References ..........................................................................................................................................9

LIST OF TABLES

TABLE TITLE

7-1 Comparison of K-25 external coworker penetrating doses modified to account for missed 

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

PAGE

8
Document No. ORAUT-OTIB-0020 Revision No. 02 Effective Date: 12/04/2008 Page 4 of 9

1.0

Technical information bulletins (TIBs) are not official determinations made by the National Institute for 

Occupational Safety and Health (NIOSH) but are rather general working documents that provide 

historic background information and guidance to assist in the preparation of dose reconstructions at 

particular sites or categories of sites. They will be revised in the event additional relevant information 

is obtained about the affected site(s). TIBs may be used to assist NIOSH staff 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 (DOE) 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 TIB is to provide general information to allow Oak Ridge Associated Universities 

(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 that were received by one or more claimants with no 

individual monitoring data. 

BACKGROUND

Cases without individual external monitoring data can 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 nonradiological worker).

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

• The worker might have been monitored but the data are not available to the dose 

reconstructor.

• Partial information for the worker might be available, but it 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 onsite 

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 is less than 45%). In relation to the last category 

above, if sufficient information is available, a prorated dose can be assigned in certain circumstances. 

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 assigned 

GENERAL APPROACH
Document No. ORAUT-OTIB-0020 Revision No. 02 Effective Date: 12/04/2008 Page 5 of 9

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

monitored. As described in Section 5.0, 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 for each dosimeter result reported 

as zero or less-than one-half of the limit of detection (LOD) as equal to the LOD divided by 2 using 

OCAS-IG-001 (NIOSH 2007) guidance for monitored workers.

Site-specific coworker datasets that contain 50th- and 95th-percentile penetrating and nonpenetrating 

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. Also note that certain 

construction trades (e.g., pipefitters) might have received higher exposures than construction trade 

workers in general; therefore, they might fall into the category of workers who were expected to have 

been monitored. For workers who are unlikely to have been exposed, external onsite ambient dose 

should be used rather than coworker doses. The site-specific TIBs also provide information on the 

sources of the site data, validation of the data, and conversion of the data to annual doses to be 

applied in dose reconstructions.

The coworker doses in the site-specific TIBs should be treated as constant values. However, they do 

not include all factors that must be applied by the dose reconstructor 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. In addition, 

organ dose conversion factors based on OCAS-IG-001 (NIOSH 2007) must be applied; for likely 

compensable or likely noncompensable cases, they should be applied in the same manner in which

they are applied for monitored employees. Otherwise, the organ dose conversion factors should be 

applied as a triangular distribution.

4.0

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

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

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

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

on coworker data. Cases that are identified as requiring coworker data should be processed as 

described in Section 6.0. 

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 an 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 might

be necessary to modify the dose reconstruction and/or perform additional research.

5.0

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

the Center for Epidemiologic Research databases maintained by ORAU, the Comprehensive 

Epidemiologic Data Resource databases maintained by DOE, other datasets maintained by DOE, and 

data maintained by the sites themselves. In addition, claimant data that has been submitted by DOE 

DEVELOPMENT OF SITE COWORKER DATASETS AND DISTRIBUTIONS 
Document No. ORAUT-OTIB-0020 Revision No. 02 Effective Date: 12/04/2008 Page 6 of 9

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

useful subset of sitewide data.

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

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

available. Before 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 that have been 

submitted to NIOSH by the DOE sites. This comparison helps to verify the accuracy and 

completeness of the site data that was selected for use in coworker studies because the data that 

have been submitted to NIOSH are often more detailed than the sitewide datasets (e.g., individual 

badge data are typically provided to NIOSH, while the sitewide data often represent annual 

summarized data). The comparison also provides information that is needed to adjust the sitewide 

datasets to account for missed dose, partial year data, etc. If significant issues arise during the 

course of this comparison that shed doubt on the accuracy or completeness of the site data that was 

selected for analysis, additional evaluations should take place to ensure that a valid dataset has been 

selected.

The specific datasets that were 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]. Before 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. Before 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 for claimants (NIOSH 2007). 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 that corresponds to one badge exchange (because it 

is not possible that all 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 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 that were 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. 

6.0

Data are presented in a table in each site-specific external coworker TIB as 50th- and 95th-percentile 

annual penetrating and nonpenetrating 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 should be applied if the worker was likely 

APPLICATION OF SITE COWORKER PERCENTILE DOSES AND A COMPARISON TO 

MAXIMUM LIKELIHOOD DOSES 
Document No. ORAUT-OTIB-0020 Revision No. 02 Effective Date: 12/04/2008 Page 7 of 9

exposed intermittently, and the 95th-percentile doses should be applied if the worker was likely 

exposed routinely. External onsite ambient doses should be used instead of external coworker doses 

if the worker was unlikely to have been exposed. Doses should be prorated, as appropriate, to 

account for partial years of exposure.

The approach this document describes 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 datasets [e.g., the use of nLOD/2 as prescribed in OCASIG-001 (NIOSH 2007) and described in Section 5.0 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 low in comparison with the LOD (NIOSH 2007), 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 that are assigned in accordance with the principles that are 

established in this document represent overestimates can be demonstrated by comparing site-specific 

percentile doses that have been calculated in accordance with these principles to doses that have 

been calculated using the maximum likelihood approach. For example, Table 7-1 compares the 

percentile doses for K-25 from ORAUT-OTIB-0026 (ORAUT 2006; the site-specific coworker TIB) to 

doses that were calculated from the same dataset but using the maximum likelihood approach [in the 

same manner as was performed for Y-12 film badge data in ORAUT-RPRT-0032 (ORAUT 2005)]. 

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 zero or low-dose results [i.e., the geometric mean (GM) values for this period 

were very low and the geometric standard deviation (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 GMs and GSDs. 
Document No. ORAUT-OTIB-0020 Revision No. 02 Effective Date: 12/04/2008 Page 8 of 9

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

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

Year

ORAUT-OTIB-0026

50th percentile

ORAUT-OTIB-0026

95th percentile

Maximum 

likelihood 

GM

Maximum 

likelihood 

GSD

Maximum 

likelihood 

95th percentile

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

a. ORAUT (2006).

7.0

All information requiring identification was addressed via references integrated into the reference 

section of this document.

ATTRIBUTIONS AND ANNOTATIONS
Document No. ORAUT-OTIB-0020 Revision No. 02 Effective Date: 12/04/2008 Page 9 of 9

REFERENCES

NIOSH (National Institute for Occupational Safety and Health), 2007, External Dose Reconstruction 

Implementation Guideline, OCAS-IG-001, Rev. 03, Office of Compensation Analysis and 

Support, Cincinnati, Ohio, November 21. 

ORAUT (Oak Ridge Associated Universities Team), 2005, Historical Evaluation of the Film Badge 

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

ORAUT-RPRT-0032, Rev. 00, Oak Ridge, Tennessee, April 13.

ORAUT (Oak Ridge Associated Universities Team), 2006, External Coworker Dosimetry Data for the 

K-25 Site, ORAUT-OTIB-0026, Rev. 00 PC-2, Oak Ridge, Tennessee, November 15.