Draft White Paper 

REVIEW OF PROPOSED NIOSH METHODS FOR 

RECONSTRUCTING THORIUM DOSES AT FERNALD 

(1979–2006) 

 

Contract No. 211-2014-58081

Revision 0 

Prepared by 

Bob Barton 

Joyce Lipsztein 

S. Cohen & Associates 

1608 Spring Hill Road, Suite 400 

Vienna, VA 22182 

November 2014

Disclaimer 

This document is made available in accordance with the unanimous desire of the Advisory Board on 

Radiation and Worker Health (ABRWH) to maintain all possible openness in its deliberations. However, 

the ABRWH and its contractor, SC&A, caution the reader that at the time of its release, this report is predecisional and has not been reviewed by the Board for factual accuracy or applicability within the 

requirements of 42 CFR 82. This implies that once reviewed by the ABRWH, the Board’s position may 

differ from the report’s conclusions. Thus, the reader should be cautioned that this report is for 

information only and that premature interpretations regarding its conclusions are unwarranted.
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S. Cohen & Associates:

Technical Support for the Advisory Board on

Radiation & Worker Health Review of

NIOSH Dose Reconstruction Program

Document No.: Review of NIOSH

Thorium Reconstruction Methods

Effective Date: 

Draft – November 24, 2014

Revision No.:

0 (Draft)

Review of Proposed NIOSH Methods for 

Reconstructing Thorium Doses at Fernald

(1979–2006)

Page 2 of 50

Task Manager:

_____________________________ Date: ___________

John Stiver, MS, CHP

Supersedes:

N/A

Project Manager:

_____________________________ Date: ___________

John Stiver, MS, CHP

Reviewers:

 

 John Stiver

Record of Revisions

Revision 

Number

Effective 

Date Description of Revision

0 (Draft) 11/24/2014 Initial issue
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TABLE OF CONTENTS 

Abbreviations and Acronyms ..........................................................................................................5

1.0 Introduction and Executive Summary .................................................................................7

2.0 Proposed Approach for Reconstruction of Thorium Internal Doses ..................................10

3.0 Additional Information on Thorium Processing/Production Activities Post-1979............13

4.0 Overview of In Vivo Record Completeness and Adequacy Analysis (1979–1989) .........15

5.0 SC&A Review of the Interpretation of In Vivo Monitoring Results for Thorium in 

Terms of Intakes ................................................................................................................18

6.0 Review of Job Titles Selected for Coworker Intake Assignment ......................................22

7.0 Review of Coworker Assignments Based on DAC Model (1990–1994) ..........................30

8.0 Characterization and Analysis of Breathing Zone Sampling (1995–2006) .......................35

9.0 Evaluation of Thoron Exposures at Fernald ......................................................................40

References ......................................................................................................................................43

Attachment 1: Assessment of Thorium Inquiries (1977 through 1985) Taken from Leist 

1985, Attachment 3 ............................................................................................................45

Attachment 2: Excerpts from the ABRWH Transcript Regarding Selection of Workers for 

Thorium Internal Dose Assignment and Exposure Potential Post-1994 ...........................46
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LIST OF TABLES 

Table 1. Internal Thorium Dose Reconstruction Methods by Time Period ................................. 10

Table 2. Thoron Exposure Recommendations ............................................................................. 12

Table 3. Excerpt from Bonfer 1988 Listing Thorium Production Orders Post-1979 .................. 13

Table 4. Overview of Available In Vivo Data 1979–1988 .......................................................... 15

Table 5. Comparison of In Vivo Results by Job Title (1979–1988) ............................................ 16

Table 6. Comparison of In Vivo Results by Plant Area (1979–1988) ......................................... 17

Table 7. Number of Days Elapsed for Workers with Samples Above or Below the MDA ........ 17

Table 8. Examples of In Vivo Monitoring Results in nCi with High U-235 Chest Burdens ...... 20

Table 9. 50th Percentile Time-Weighted OPOS Compared to the Pb-212 Detection Levels 

Given in NIOSH 2014a ................................................................................................ 21

Table 10. Breakdown of Job Types for Claimants Employed 1979–1994 with a POC of 

Less than 50% .............................................................................................................. 23

Table 11. Breakdown of Category 2 Claimants by NIOSH 2014a Job Types ............................ 24

Table 12. Survey of Claimants with Job Titles Not Currently Included in NIOSH 2014A 

and a POC Less than 50% ............................................................................................ 25

Table 13. Examination of 22 Unmonitored Claimants in the 1990–1994 Period with 

Occupations with the Potential for Thorium Exposure ................................................ 32

Table 14. Breakdown of Thorium Breathing Zone Samples by Year ......................................... 35

Table 15. Number of Samples per Monitored Worker per Year ................................................. 37

Table 16. Breathing Zone Results for Worker Involved in Thorium Overpack Project .............. 38

Table 17. Summary of NIOSH 2014a Thoron Exposure Estimates (1979–2006) ...................... 40
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ABBREVIATIONS AND ACRONYMS 

Advisory Board 

or ABRWH Advisory Board on Radiation and Worker Health 

BZ breathing zone 

CATI Computer-Assisted Telephone Interview 

DAC derived air concentration 

DCAL Dose and Risk Calculation Software 

DL detection limit 

DOE (U.S.) Department of Energy 

DOL (U.S.) Department of Labor 

FERMCO Fernald Environmental Restoration Management Corporation 

FMPC Feed Materials Production Center 

H&S Health and Safety 

HEPA high efficiency particulate air 

ITO industrial truck operator 

IVEC In Vivo Examination Center 

kg kilogram 

LANL Los Alamos National Laboratory 

MDA minimum detectable activity; minimum detectable amount 

μCi/ml microcurie per milliliter 

MIVRML Mobile In-Vivo Radiation Monitoring Laboratory 

mrem millirem

MT Metric Tons 

nCi nanocuries 

ND not detected 

NIOSH National Institute for Occupational Safety and Health 

NOCTS NIOSH/OCAS Claims Tracking System 

OCAS Office of Compensation Analysis and Support 

OPOS One Person – One Sample

ORAUT Oak Ridge Associated Universities Team 

PAPR Powered Air-Purifying Respirator 

pCi/g picocuries per gram 
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POC probability of causation 

QA quality assurance 

RF release fraction

SC&A S. Cohen and Associates (SC&A, Inc.) 

SEC Special Exposure Cohort 

SRDB Site Research Database 

TLD thermoluminescent dosimeter 

WLM working level month 
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1.0 INTRODUCTION AND EXECUTIVE SUMMARY

On June 24, 2014, the National Institute for Occupational Safety and Health (NIOSH) 

transmitted a white paper titled, Fernald Dose Reconstruction Methodology for the Post Special 

Exposure Cohort (SEC) Period, 1979–2006 Rev. 02 (NIOSH 2014a), which contains the 

proposed dose reconstruction methods for assigning internal thorium doses to unmonitored 

workers.1

Subsequent to this, SC&A was tasked with reviewing the white paper to assess 

whether the proposed methods represent a plausible, sufficiently accurate and claimant-favorable 

approach to assigning coworker intakes. The contents of NIOSH 2014a were also presented and 

discussed during the Fernald Work Group meeting on September 3, 2014 (ABRWH 2014),

which facilitated preliminary points of clarification regarding the coworker model. 

This document presents SC&A’s review of the proposed approach to assigning thorium doses in 

the post-Special Exposure Cohort (SEC) period (1979–2006). The dose reconstruction methods 

presented in NIOSH 2014a can be separated into three time periods: 1979–1989, 1990–1994, 

and 1995–2006. Section 2 of this report provides a summary description of the three methods 

presented in NIOSH 2014a to assign thorium intakes by period. Section 3 provides some 

additional information identified by SC&A on the historical sources of thorium exposure 

potential that were not necessarily discussed in NIOSH 2014a. SC&A had previously performed 

an evaluation of the completeness and adequacy of in vivo monitoring records in the 1979–1989 

period (SC&A 2012); the salient points from that review are discussed in Section 4. Section 5 

discusses the current method of interpreting thorium in vivo measurements in terms of the 

thorium intake analysis during the 1979–1989 period. Section 6 reviews the proposed method of 

assigning unmonitored thorium intakes based on predefined worker job types and includes a 

review of a number of sampled claimants who might be affected. Sections 7 and 8 review the 

proposed dose reconstruction methods for after 1989 which include the use of the derived air 

concentration (DAC) in place in the 1990–1994 period, as well as the use of worker breathing 

zone (BZ) samples from 1995–2006, respectively. 

Based on SC&A’s review, the following seven findings were noted: 

Finding 1: While it appears that the majority of the thorium exposure potential at Fernald in the 

post-SEC period was related to redrumming and repackaging activities, some evidence exists 

that small-scale handling and possibly production may have occurred after 1979. Given that it is 

currently infeasible to identify which workers were involved in these operations and potentially 

exposed, and by extension whether those workers were properly monitored, NIOSH should 

assign unmonitored thorium intakes for all workers who may have entered radiological areas and 

been exposed to thorium materials. 

Finding 2: Given that the monitoring program does not appear to be directly focused on areas 

where thorium exposure potential existed, coupled with the inability to effectively identify which 

workers may have handled thorium materials, NIOSH should instruct the dose reconstructors to 

assign the 95th percentile coworker intake value to all unmonitored claimants who may have 

been directly involved in thorium operations. 

 

1

 Coworker dose assessment is only proposed through 1994 in NIOSH 2014a; after this time, only 

monitored worker doses are reconstructed. 
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Finding 3: Given the broad work locations and duties contained among worker job types not 

currently defined as a thorium worker in NIOSH 2014a, NIOSH should provide explicit 

instructions to the dose reconstructor that thorium coworker intakes should be assigned unless 

sufficient evidence exists that the claimant did not enter radiological areas where thorium 

exposure potential may have existed. 

Finding 4: Unless sufficient evidence exists that thorium exposure potential at Fernald was 

restricted to solubility class “W,” NIOSH should consider using the more conservative and 

claimant favorable DAC value for solubility class “Y.”

Finding 5: NIOSH should not restrict the assignment of thorium intakes to workers who 

submitted pre-employment fecal samples, but rather assign intakes based on the potential for 

radiological exposure (see discussion in Section 6). 

Finding 6: The underlying assumptions employed in NIOSH 2014a to reconstruct doses to 

thoron appear to be arbitrary and are not well established or referenced. The assumptions 

concerning thorium source term inventory, release fraction, equilibrium factor, occupancy time, 

and specific activity of thoron should be more carefully defined based on credible documentation 

and site specific records. 

Finding 7: It is necessary that NIOSH evaluate the thoron/thoron daughters’ exposures due to 

Ra-228. Independent of the time assumed after separation, it is necessary to evaluate whether 

workers could have worked in areas where Ra-228 was handled or stored and consider the 

associated thoron exposures. As stated on page 105 of NIOSH 2014a, Ra-228 has a half–life 

long enough to permit its presence in the workplace for years independent of the original parent 

isotope (Th-232). 

In addition, during the course of this review, SC&A documented the following seven 

observations: 

Observation 1: It appears that the monitoring program was focused towards job categories that 

had the highest exposure potential, as evidenced by the large proportion of in vivo results 

attributed to chemical operators. 

Observation 2: Workers who registered above MDA results for either Pb-212 or Ac-228 were 

resampled approximately 10 times faster than workers who had results below the MDA. 

Observation 3: SC&A agrees with the following claimant-favorable assumptions presented in 

NIOSH 2014a: triple separation of thorium; adjustment for bias on the chest counts of Ac-228 

and Pb-212; Pb-212 monitoring results should be used to calculate thorium intakes; and chest 

counts with a high Ac-228:Pb-212 ratio (greater than 1.5:1) be interpreted as intakes of a mixture 

of triple-separated thorium and unsupported Ra-228. 

Observation 4: Given that discussions related to the method for analyzing coworker data are 

ongoing, a complete review of the in vivo coworker analysis is inappropriate until the timeweighted OPOS methodology is accepted by the Advisory Board. 
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Observation 5: Based on the review of the DOE records, CATI Reports, and associated job 

descriptions of 22 unmonitored claimant records, it is highly unlikely that the workers would 

have been continually exposed to airborne thorium levels above 10% of the DAC for the entire 

duration of their employment in the 1990–1994 period. 

Observation 6: NIOSH should cite the aforementioned review and/or provide additional 

discussion of the underlying evidence that BL-13, BL-65, Cell 8, KS-65 and RT-210 are 

representative of thorium material. 

Observation 7: It is not immediately clear what the temporal criteria was for collecting and 

analyzing breathing zone samples; however, it is evident that they were not necessarily collected 

on a daily basis. One likely possibility is that the breathing zone sample was measured over 

longer periods of time. However, documentation or other evidence should be provided to 

sufficiently establish that the breathing zone data are complete and represent comprehensive 

monitoring for thorium activities. 
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2.0 PROPOSED APPROACH FOR RECONSTRUCTION OF 

THORIUM INTERNAL DOSES

It should be noted that prior to 1979, it was determined that reconstruction of internal thorium 

doses was infeasible and therefore two separate SECs were recommended by the Advisory Board 

on Radiation and Worker Health on May 29, 2012 (ABRWH 2012) and August, 28, 2013 

(ABRWH 2013b). The internal thorium dose reconstruction methods for unmonitored workers 

post-1978 can effectively be split into three time periods: 1979–1989, 1990–1994, and 1995–

2006. These three time periods delineate different approaches to assigning doses to both 

monitored and unmonitored workers. An unnumbered table contained on pages 12 and 13 of 

NIOSH 2014a (presented here as Table 1) summarizes the proposed methods for thorium dose 

assignment. 

Table 1. Internal Thorium Dose Reconstruction Methods by Time Period 

Timeframe In Vivo Data Exist (Yes/No) Evaluation Method Source/Basis

1979–1994 Yes In Vivo Results aLaBone documents

1979–1989 No Coworker Data bThorium In Vivo 

Coworker Study

1990–1994 No 10% Th-232 Class W DAC cThorium Inh/Ing intake 

from air limit calculation 

(DOE 5480.11 & Project 2 

documentation)

1995–2006 Yes - may use to decide if in vivo 

results reflect a lung burden that 

had been previously identified 

from earlier exposure. Positive 

in vivo is used in place of 

negative BZ results unless it is an 

artifact of an earlier detected lung 

burden. For in vivo results below 

MDA use BZ results.

No – use BZ data

BZ Air Monitoring results 10 CFR 835 compliance 

and thorium bioassay 

technology shortfall

(SRDB Ref ID: 3545 & 

HIS-20 database)

a Evaluation of Fernald Ac-228/Pb-212 Chest Count Data, 04/18/2013; Activity Ratios for various types of 

Thorium, 06/21/2013; Approximate Evaluation of Pb-212 Chests Counts Following Intakes of Thorium, 

07/19/2013; and Using Ac-228 and Pb-212 to Measure Intakes of Th-232, 09/18/2013 (see Attachments B.1-4 

of NIOSH 2014a). 

b Thorium In Vivo Coworker Study (in development), Attachment C of NIOSH 2014A. 

c Thorium Inhalation/Ingestion intake from air limit calculation, Attachment D of NIOSH 2014A. 

Source: NIOSH 2014a, pp. 12 and 13. 

As seen in Table 1, the prime method for reconstructing thorium doses for monitored workers is 

to utilize available in vivo records from 1978 through 1994. After 1994, the dose reconstructor 

is to use the in vivo records only if it can be established that the positive in vivo result is not a 

reflection of intakes occurring in the prior timeframe (1979–1994). If no in vivo results are 

available for a given worker, then the application of coworker intakes would be applied for the 

1979–1989 period based on the available in vivo data. An overview of the in vivo data available 

for coworker modeling in the 1979–1989 timeframe can be found in Section 4 of this report. 

According to NIOSH 2014a, coworker intakes will only be applied to workers with the following 
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job types: chemical operators, fork truck drivers, laborers, transportation laborers, operations, 

production workers, and maintenance personnel. 

For 1990–1994, in vivo data will be used when it is available for the worker. For unmonitored 

workers, potential internal exposure is modeled by assuming that the given worker was exposed 

to airborne concentrations of thorium equal to 10% of the derived air concentration (DAC). The 

stated DAC value of 5 × 10-13 μCi/ml is based on Department of Energy Order 5480.11 

Appendix A (DOE 1988) for Th-232 of solubility type “W.” The ingestion component is 

estimated using OCAS 2014, which calculates ingestion based on contaminated food/drink, as 

well as inadvertent ingestion from the potentially contaminated hands of the worker. For each 

pathway, OCAS 2014 estimates the ingestion intake is 10% of the contaminant air concentration 

(for a combined 20%). Based on NIOSH 2014a, unmonitored thorium exposures will be applied 

in cases for which the worker submitted a thorium fecal sample. Specifically, NIOSH 2014A 

states on page 16: 

1990–1994: Thorium workers with no in vivo results, but with pre-job fecal 

sample results during this employment period at Fernald are recommended to be 

assigned a dose based on a thorium air concentration of 5×10-14 μCi/ml (10% 

DAC), as a maximum potential exposure. 

It is not clear based on Table 1 and the above quote whether thorium exposures would be 

assigned for 1990–1994 only if pre-job fecal samples were obtained. 

After 1994, NIOSH proposes to use available BZ data where available. Unmonitored workers 

are assumed to have not been exposed to thorium and will not be assigned a thorium coworker 

dose. Presumably, the unmonitored workers will be assigned ambient environmental intakes in 

accordance with ORAUT 2014a, Table 4-2. During the September 3, 2014, Fernald Work Group 

meeting, NIOSH stated the following concerning the post 1994 period (ABRWH 2014): 

MR. HINNEFELD: And then for the, and then Fluor instituted a 100 percent BZ 

air sampling regimen for thorium work while they were there. But it appears to 

me that that wasn’t fully in effect until ’95 even though Fluor got there in, like, 

’92. The 100 percent BZ, we haven’t found that it’s completely 100 percent 

implemented until ’95. So from ’95 until 2006, which was site closure, everyone 

who worked around thorium, every person wore a BZ sampler and we do have 

that BZ sampling database, all the data from that. So we would propose to use 

the BZ sampling database for individuals from ’95 to 2006. (ABWRH 2014, pg.

70) 

Table 1 indicates the following when a particular claimant has both BZ and in vivo monitoring 

data: 

Positive in vivo is used in place of negative BZ results unless it is an artifact of an 

earlier detected lung burden. For in vivo results below MDA use BZ results. 
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This was further clarified during the September 3, 2014, Work Group meeting: 

Now, we also have in vivo data from there [during the period from 1995–2006]

so, you know, in this case if we have positive data from in vivo it would trump 

negative data from BZ and vice versa, I mean, a negative in vivo, if you’ve got 

less in vivo, then you use the BZ data for the person. – Stu Hinnefeld (ABRWH 

2014, pp. 70–71) 

So it appears that the method for reconstructing doses to monitored workers is to select the 

method (in vivo or BZ) that results in the highest thorium intake on a case-by-case basis, the only 

caveat being that the in vivo monitoring is discarded if it is clear that the positive lung burden is 

reflective of an intake that occurred before the period of interest. 

NIOSH 2014a also presents methods for reconstructing doses to thoron which may have 

occurred during repackaging and stewardship activities at Fernald, as well as limited production 

activities. Table F-7 of NIOSH 2014a presents the calculated thoron exposures for 3 locations 

and/or activities, this table is recreated below for convenience. 

Table 2. Thoron Exposure Recommendations 

Time Period* Area/Plant WLM**/year

1977–1979 Pilot Plant 0.03

1972–1989 Storage facilities, repackaging, etc. 1.6

1972–2006 Closure Various Storage 0.5

* Note that because thoron exposures are associated with thorium exposures, they 

are not assigned during the thorium SEC periods, (1954–1967 and 1968–1978). 

** WLM = Working Level Month 

Source: NIOSH 2014a, Table F-7 

In the case of thoron exposures, NIOSH does not specify a particular job category or work 

location in which doses should apply and states: 

The dates and bounding levels of calculated potential exposures represent 

recorded operational history. However, thorium was present on site for most of 

its history. For unknown work locations and time periods of concern, Dose 

Reconstructors should assume that thoron exposure potential existed, as a 

claimant favorable assumption, and assign thoron doses based on the guidance 

from the table. (NIOSH 2014a, pg. 19)
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3.0 ADDITIONAL INFORMATION ON THORIUM 

PROCESSING/PRODUCTION ACTIVITIES POST-1979

The section titled “Post Production Thorium Activities” in NIOSH 2014A provides a detailed 

description of the types of activities involving thorium post-1979. Attachment A of that same 

report also provides an annotated timeline of thorium-related activities beginning with the 

cessation of production activities. Specifically, NIOSH 2014A notes: 

An inventory of thorium production orders shows that there were no orders after 

1985 and only a few from 1979–1985. It is likely that most or all of these 

production orders involved just taking stored material out of the warehouse and 

shipping it to a customer.

A summary of these production orders is listed in Attachment 3 of Bonfer 1988 and is presented 

in Table 3: 

Table 3. Excerpt from Bonfer 1988 Listing Thorium Production Orders Post-1979

Production 

Order Number Description Date Order Issued

Date 

Completed

D-649 ThO2 for Sandia 5/15/1981 Unknown

D-650 ThO2 – Los Alamos 5/15/1981 Unknown

D-651 ThO2 to Lawrence Livermore 5/18/1981 Unknown

D-656 ThO2 Powder to Public Service of Colorado 10/27/1981 Unknown

D-659 ThO2 to Sandia (Bettis Material) 1/15/1982 Unknown

D-660 ThO2 Samples (Bettis Material) Public Service of Colorado 1/26/1982 Unknown

D-661 Surplus Bettis Oxide (9 lots) to Public Services of Colorado 3/11/1982 Unknown

D-663 (RI) Thorium Oxide for EG&G, Idaho 9/24/1982 Unknown

D-667 Th to LANL (150 kg.) 8/23/1982 Unknown

D-668 ThO2 for LANL (1,000 kg.) 9/24/1982 Unknown

D-713 ThO2 samples for PCC211/19/1984 Unknown

D-714 ThO2 Samples for MEI111/19/1984 Unknown

M-572 ThO2 for Precision Castparts Corp. Unknown 4/9/1985

M573 Thoria for 3M Co. Unknown 6/14/1985

M-574 Thorium Nitrate for 3M Co. Unknown 8/15/1985

Interestingly, the completion dates on the majority of the orders shown in Table 3 are unknown,

as the source document simply leaves that column blank. During the September 3, 2014, Fernald 

Work Group meeting, production operations were described by NIOSH as follows: 

Mr. Hinnefeld: There were a handful of task orders. When you talk about 

thorium work, there were a handful of task orders after 1979 up through maybe 

’85 or so, not very many. But those appear to be small amounts to a particular 

customer and I believe what was going on there was they were taking material out 

of storage. Some of the stuff was good-quality product, thorium oxide that had 

been made for shipping or for their thorium reactor but had never been sent. It 

 

2 Unclear what “MEI” and “PCC” represent, though it is likely they are commercial facilities. 
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was good quality and well packaged. Those containers held up fine. (ABRWH 

2014) 

SC&A identified additional information concerning the sale of thorium materials to Public 

Service of Colorado in 1982 (see items D-660 and D-661 in Table 3). The sale was described in 

a late 1985 report as follows: 

Principal customers [for thorium material] included government laboratories for 

refractory development, fuels, and other applications, Public Service of Colorado 

for fuel production by General Atomics, the development of casting refractories. 

The largest sale, 6.76 MT, occurred in 1982 when surplus Bettis ThO2 was sold to 

Public Services of Colorado for a price of $27.46 per kilogram of thorium 

(including $4.50 for intrinsic thorium value, $15.50 for purification and oxide 

conversion, with the remainder for packaging, freight, depreciation, and DOE 

burden charges). (Leist 1985)

Leist 1985 also contains a list of thorium sales inquiries made at Fernald for the period of 

interest; these are presented in Attachment 1 of this report. Furthermore, the FY-1985 Issue 

Environmental, Safety and Health Plan (Rixner 1984) described plans for more significant 

thorium processing work: 

A total of 423.6 MT Th high-grade residues and impure thoria gel will be 

processed to a pure dense oxide for industry needs. All processing equipment 

located in the Pilot Plant for purification, precipitation, drying and calcination 

via the sol gel process must be reactivated. Improvements will be needed for 

personnel protection during the drying and calcining operations. (Rixner 1984) 

This would indicate that significant processing and production operations were planned to occur 

in the Pilot Plant at Fernald during this later period; however, additional information was not 

located. SC&A agrees that any production operations would only likely affect a very small 

portion of the worker population. However, given the inability to accurately identify all Fernald 

workers who may have been involved, significant care must be taken to assure that all potentially 

exposed workers are appropriately assigned thorium coworker intakes. 

Finding 1: While it appears that the majority of the thorium exposure potential at Fernald in the 

post-SEC period was related to redrumming and repackaging activities, some evidence exists 

that small-scale handling and possibly production may have occurred after 1979. Given that it is 

currently infeasible to identify which workers were involved in these operations and potentially 

exposed, and by extension whether those workers were properly monitored, NIOSH should 

assign unmonitored thorium intakes for all workers who may have entered radiological areas and 

been exposed to thorium materials.
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4.0 OVERVIEW OF IN VIVO RECORD COMPLETENESS AND 

ADEQUACY ANALYSIS (1979–1989) 

On November 26, 2012, SC&A released the white paper, Completeness and Adequacy of 

Thorium In-Vivo Records (1979–1989) (SC&A 2012), which provided an in-depth review of the 

available in vivo records from 1979 through 1989. 

SC&A 2012 was separated into 3 main sections: 

1. A review of historical documentation and relevant reports to define thorium operations 

during the period of interest 

2. An evaluation of the completeness of the available in vivo data for 1979–1988

3. An evaluation of the technical adequacy of the available thorium in vivo data 

The historical information contained in Section 1 of SC&A 2012 has mainly been discussed in 

the previous section of this report (Section 3), and will not be duplicated here. This section 

summarizes SC&A’s completeness analysis (item 2 above). An updated discussion of the 

adequacy of the thorium in vivo records (item 3) can be found in Section 5. 

Table 4 shows the number of available in vivo samples by year. As seen in the table, only a 

small portion of the available data contained results above the minimum detectably activity 

(MDA).3 As expected, the highest percentage of positive results occurred in 1979 and 1980 

when the last major thorium processing campaigns ended. For all other years, nearly 95% of the 

available data was below the assumed MDA. 

Table 4. Overview of Available In Vivo Data 1979–1988

Year # 

Samples

# Samples with 

both Ac and Pb 

Results above the 

MDA3

# Samples with 

Only the Ac 

Result above the 

MDA3

# Samples with 

Only the Pb 

Result above 

the MDA3

# Samples with 

no Results 

above the 

MDA3

1979 177 26 (14.7%) 4 (2.3%) 2 (1.1%) 145 (81.9%)

1980 188 13 (6.9%) 14 (7.4%) 1 (0.5%) 160 (85.1%)

1981 141 8 (5.7%) 3 (2.1%) 1 (0.7%) 129 (91.5%)

1982 180 8 (4.4%) 1 (0.6%) 5 (2.8%) 166 (92.2%)

1983 169 4 (2.4%) 1 (0.6%) 1 (0.6%) 163 (96.4%)

1984 371 9 (2.4%) 3 (0.8%) 0 (0.0%) 359 (96.8%)

1985 382 2 (0.5%) 3 (0.8%) 4 (1.0%) 373 (97.6%)

1986 463 4 (0.9%) 2 (0.4%) 5 (1.1%) 452 (97.6%)

1987 562 4 (0.7%) 1 (0.2%) 5 (0.9%) 552 (98.2%)

1988 108 1 (0.9%) 1 (0.9%) 0 (0.0%) 106 (98.1%)

All In Vivo Data 

(1979–1988) 2741 79 (2.9%) 34 (1.2%) 24 (0.9%) 2604 (95.0%)

 

3

 The MDA for Ac-228 and Pb-212 were assumed to be 0.24 and 0.23 nCi, respectively, in accordance with 

SC&A 2012. Alternate detection limits were derived in Attachment B-1 of NIOSH 2014a; however, the report also 

notes: “For simplicity, a single DL of 0.12 nCi will be adopted for both nuclides for all years. If a minimum 

detectable amount (MDA) is need [sic] for dose reconstruction purposes, a value of 2DL=0.24 nCi should be used 

for both nuclides.” (NIOSH 2014a, pg. 32) 
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SC&A also analyzed the available data by job type and work area; the results can be seen in 

Tables 5 and 6, respectively. Based on the job title analysis, it is clear that the highest proportion 

of in vivo results were taken for workers classified as “chemical operators” (55% of the total 

samples). This job category also had the highest numerical results when evaluated at the 95th

percentile. 

 

Observation 1: It appears that the monitoring program was focused towards job categories that 

had the highest exposure potential, as evidenced by the large proportion of in vivo results 

attributed to chemical operators. 

Table 5. Comparison of In Vivo Results by Job Title (1979–1988) 

Job Title # of Samples (% of Total)

Magnitude of Results

95th Percentile*

(Ac-228)

95th Percentile*

(Pb-212)

Chemical Operator 1207 (55.0%) 0.387 0.330

Unknown 549 (25.0%) 0.150 0.160

Construction Trades 248 (11.3%) 0.096 0.056

Other Operator 156 (7.1%) 0.278 0.194

Millworker 141 (6.4%) 0.100 0.020

Engineer/Technician 81 (3.7%) 0.100 0.030

Supervisor 73 (3.3%) 0.186 0.200

Industrial Truck Operator (ITO) 68 (3.1%) 0.120 0.113

Laborer 59 (2.7%) 0.104 0.071

Inspection/QA 53 (2.4%) 0.084 0.050

Oiler/Degreaser 28 (1.3%) 0.097 0.070

Health and Safety 21 (1.0%) 0.090 0.260

Administrative 20 (0.9%) 0.061 0.057

Mechanic 16 (0.7%) 0.073 0.040

Security 12 (0.5%) 0.183 0.282

Laundry 10 (0.5%) 0.081 0.000

*95th percentile evaluated using Microsoft Excel’s Percentile Function

As seen in Table 6, the highest proportion of in vivo results was not generally attributable to a 

specific plant, with over 37% associated with “other areas.”4 This might suggest that the 

monitoring program was not focused on any specific area, but rather on a diverse cross section of 

work locations at Fernald. The Pilot Plant (where the last major thorium processing campaigns 

took place) exhibited the highest observed in vivo results at the 95th percentile; however, this 

constituted only about 4% of the observed samples. The main thorium storage facilities 

(Buildings 64, 65, 67, and 68, as well Plant 8 Bin and Silos) were not specifically listed for any 

of the in vivo results. 

While the sampling criteria by work area appear somewhat ambiguous, it does not appear that in 

vivo monitoring for thorium was unduly biased towards plant areas with lower exposure 

potential. However, considering the inability to associate specific workers and monitoring 

results with the thorium handling and redrumming operations, it is important that any doses 

 

4

 Locations designated as “other areas” include Administration Buildings, Safety and Health, Inspection, 

Garage, Laundry, Maintenance, Mechanical, Medical, Production, Quality Assurance, Security, Services, Tank 

Farm, Technology Area, Transport, and Water Treatment. 
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assigned via a coworker model properly bound the potential exposures to these unidentified 

workers. 

Finding 2: Given that the monitoring program does not appear to be directly focused on areas 

where thorium exposure potential existed, coupled with the inability to effectively identify which 

workers may have handled thorium materials, NIOSH should instruct the dose reconstructors to 

assign the 95th percentile coworker intake value to all unmonitored claimants who may have 

been directly involved in thorium operations. 

Table 6. Comparison of In Vivo Results by Plant Area (1979–1988)

Plant Area # of Samples 

(% of Total)

Magnitude of Results

95th 

Percentile* 

Ac-228

95th 

Percentile* 

Pb-212

Other Areas 1,033 (37.7%) 0.150 0.170

Plant 5 650 (23.7%) 0.320 0.210

Plant 9 189 (6.9%) 0.146 0.086

Unknown 168 (6.1%) 0.157 0.167

Plant 6 156 (5.7%) 0.143 0.150

Plant 4 152 (5.5%) 0.230 0.180

Plant 1 111 (4.0%) 0.221 0.238

Pilot Plant 99 (3.6%) 0.355 0.305

Plant 2/3 94 (3.4%) 0.110 0.063

Plant 8 90 (3.3%) 0.136 0.121

*95th percentile evaluated using Microsoft Excel’s Percentile Function

SC&A also analyzed the number of days that elapsed between samples for the monitored worker 

population, the summary of which can be seen in Table 7. The average number of days between 

consecutive in vivo samples was 463, although the geometric mean and rank-ordered median are 

somewhat lower and closer to 1 year. When only positive samples (samples above the assumed 

MDAs for Pb-212 and Ac-228 of 0.24 and 0.23 nCi) are considered, the time elapsed between 

the positive result and the next result drops considerably. When considering the geometric mean 

and rank ordered median, the elapsed time to the next sample is approximately a factor of 10 

shorter for positive samples than for samples that were less than the MDA. This indicates that 

workers who registered positive results were resampled much more quickly than workers who 

had results less than the MDA. 

Observation 2: Workers who registered above MDA results for either Pb-212 or Ac-228 were 

resampled approximately 10 times faster than workers who had results below the MDA. 

Table 7. Number of Days Elapsed for Workers with Samples Above or Below the MDA 

Sample Type Number of Days Elapsed to Next Sample

Arithmetic Average Geometric Mean Rank-Ordered Median

All Samples 463 331 377

Positive Samples 106 36 31

Samples Less than the MDA 479 364 384
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5.0 SC&A REVIEW OF THE INTERPRETATION OF IN VIVO 

MONITORING RESULTS FOR THORIUM IN TERMS OF INTAKES 

SC&A is in general agreement with NIOSH’s proposed method for estimating Th-232/Th-228 

intakes using Pb-212 chest count results. However, concerns had been expressed in SC&A 2012 

about the relative amounts of Ac-228 and Pb-212 measured in some observed chest counts. 

Specifically, SC&A 2012 states: 

SC&A agrees that the triple separation hypothesis (Th-228/Th-232=0.19) is 

claimant favorable, for the period 1979–1988, when Pb-212 results are used to 

calculate the doses. Ac-228 activities in the lung are not affected by the number 

of separations, but are very sensitive to the time after purification. Nonetheless, 

SC&A believes that the use of Pb-212 results instead of Ac-228 remains 

problematic. Most of the Th-232 progeny results above the MDA are for Ac-228, 

and in most cases Ac-228 activities are higher than the Pb-212 activities in the 

lung. While SC&A recognizes that the triple separation assumption is intended to 

mitigate some of the uncertainties associated with the Pb-212 measurements, 

NIOSH has not explicitly addressed this problem. 

Subsequent to SC&A 2012, NIOSH calculated an adjustment for the observed bias in the chest 

counts of Ac-228 and Pb-212. SC&A agrees with the adjustments for bias using a method that 

had previously been proposed during work group deliberations. Plots of chest burdens where 

both Ac-228 and Pb-212 are greater than the DL are presented in NIOSH 2012 and show that 

most measurements, after bias adjustments, indicate equal quantities of Ac-228 and Pb-212 in 

the chest (to within measurement uncertainty). 

In Attachment B-2 of NIOSH 2014a, NIOSH justifies that the chest counts with a high 

Ac-228:Pb-212 ratio (greater than 1.5:1) can be interpreted as intakes of a mixture of tripleseparated thorium and unsupported Ra-228. NIOSH 2014a states: 

During the Fernald working group call on June 17, it was suggested that we 

should instead interpret these chest counts as being the result of intakes of some 

form of freshly separated thorium. 

However, SC&A believes this is a misinterpretation of the discussions during the June 17, 2013, work 

group meeting. It is assumed the author is referring to the quote on page 192 of the transcript (ABRWH 

2013a): 

Dr. Lipsztein: Okay. So after the production years, then we have measurements of lead 

and actinium. While lead-212 is very sensitive to the number of separations that the 

source had, immediately after the exposure, after the source is separated while actinium, 

it’s not a fact that by the number of separations because it comes just after thorium-232 

and radium, but it is very sensitive to the lag of time between measurement and 

separations. 

During that meeting, SC&A also stated that one plausible scenario for Ac-228 being higher than Pb-212 

is to assume a long time between thorium exposures and thorium monitoring. Depending on the number 
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of separations, Ac-228 might be higher than Pb-212 if monitoring occurs after 1 year after separation. On 

page 193, SC&A stated that in vivo monitoring that takes place a long time after exposure is a plausible 

scenario, because there is evidence that the main processing campaigns for thorium ended in 1979. 

Measurements for many workers could have been performed several years after separation, when Ac-228 

can be expected to be higher than Pb-212. The first three plots in Attachment B-2 of NIOSH 2014a are in 

agreement with SC&A’s position. As seen in the plots, the red line crosses the blue line (relative activity 

of Ac-228 becomes higher than that for Pb-212) and becomes higher some years after exposure, the time 

lag depending on the number of separations. 

SC&A has conducted a similar study to Attachment B-2, although SC&A assumed a continuous exposure 

of Th-232 for 1 year (see Section 5 of SC&A 2012). The one-step separation requires 5 years for Ac 

activities in the body to be higher than Pb, the two-step separation requires 3 years and the three-step 

separation requires 1 year. 

Note that the graphs in Attachment B-2 show that Pb-212 should be higher than Ac-228 if 

measurements occurred right after separation. This contradicts the graphs in Attachment B-1

(Appendix B) of NIOSH 2014a which contain plots of Ac-228 versus Pb-212 for various years 

with results >0.12 nCi. These figures show that most of the results corrected for bias show 

similar quantities of Ac-228 and Pb-212. 

In the section “Discussion of Ac-228 and Pb-212 in Chest Counts” on page 33 of NIOSH 2014a,

NIOSH states: 

In Figure B-4, chest burdens from 1978, where both Ac-228 and Pb-212 are 

greater than the DL, are presented. These data are considered to be above the 

level of analytical noise and represent actual material in the chest.5

 The diagonal 

blue line has a slope of 1 and an intercept of 0. Data falling exactly on this line 

have equal quantities of Ac-228 and Pb-212. All of these measurements, except 

for one, are considered to indicate equal quantities of Ac-228 and Pb-212 in the 

chest (to within measurement uncertainty).”

Thus on one hand, there is the hypothesis of unsupported Ra-228 present, and on the other hand, there is 

the hypothesis that the separation occurred a long time before the monitoring. As noted in SC&A 2012, 

the hypothesis of monitoring a long time after separation does not explain why many workers show 

results higher than the MDA at random years after the production period, without continuity. 

Attachment B-3 of NIOSH 2014a suggests ways to adjust intakes and intake rates of Th-232 and 

Th-228 calculated from Pb-212 chest burdens, so that the intakes and intake rates will not 

underestimate those calculated with exact methods using the Dose and Risk Calculation Software 

(DCAL). Attachment B-4 discusses the use of Ac-228 and Pb-212 to measure intakes of 

thorium. SC&A agrees with most statements in this attachment. 

Observation 3: SC&A agrees with the following claimant-favorable assumptions presented in 

NIOSH 2014a: triple separation of thorium; adjustment for bias on the chest counts of Ac-228 

and Pb-212; Pb-212 monitoring results should be used to calculate thorium intakes; and chest 

 

5

 If one looks at the Ac-228 to Pb-212 ratio and includes results that are basically noise, one can expect to 

see quite a range of ratios beyond the anticipated 1:1 that will be very difficult to interpret in a meaningful way. 
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counts with a high Ac-228:Pb-212 ratio (greater than 1.5:1) be interpreted as intakes of a mixture 

of triple-separated thorium and unsupported Ra-228. 

In addition to NIOSH 2014a, coworker intakes were evaluated in a companion document: 1979–

1989 Thorium In Vivo Coworker Study for Fernald – A Proposed Attachment for ORAUT-TKBS0017-5 Rev. 2 (NIOSH 2014b). Sections 1 and 2 of this document summarize important 

information already contained in the NIOSH 2014a. Section 3 of NIOSH 2014b states: 

...those workers with the highest uranium and thorium exposure potential would 

be counted most frequently and those with virtually no exposure potential would 

not be routinely counted at all.

While SC&A did find that workers with positive lead and actinium in vivo results were generally 

recounted quicker than workers with no positive result, monitoring data for the SEC period has 

shown that many times workers were probably selected for monitoring based on uranium 

exposure potential. Many workers that were repeatedly monitored presented high U-235 lung 

burdens, while their Pb-212 results were below DLs. Table 8 shows a few examples of 

monitoring results with high U-235 chest counts. 

Table 8. Examples of In Vivo Monitoring Results in nCi with High U-235 Chest Burdens 

Worker Date U-235 U Pb-212

A 6/11/1979 40 15.4 0.1

A 10/8/1979 67 17.2 0.1

B 3/20/1979 73 13.6 0.02

B 10/15/1979 132 15.4 0.04

C 3/26/1979 107 11.8 0.1

C 10/8/1979 34 7.6 -0.1

D 1/2/1979 36 16.6 0.1

D 3/12/1979 90 45.8

D 10/8/1979 57 15.3 -0.01

D 12/19/1979 17 27.2 0.05

E 5/19/1980 47.1 2.7 -0.8

E 6/18/1980 45 3.7 -0.07

F 2/1/1980 53 6.1 -0.11

F 6/27/1980 95.8 10.8 -0.01

In Section 3.2 of NIOSH 2014b, NIOSH utilizes a time-weighted One Person – One Sample 

(OPOS) methodology described in ORAUT 2014b to derive the 50th and 84th percentile chest 

burdens of the monitored worker population. Note that at the time that this report was delivered, 

the time-weighted approach was still under discussion. SC&A has suggested the use of a 

variation of the time-weighted approach (pre-weighted) in coworker modeling (SC&A 2014). 

In that document, SC&A argues that the time-weighting methodology gives a better estimate of 

the intake if the time-weighted OPOS is calculated using the product of the sample measurement 

with the number of days between that measurement and the prior sample. In addition, it is 

important to decide on the use of zero and negative bioassay results and on the use of results 

below the DL. 
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NIOSH has pointed out, in the June 23, 2014, white paper that if one looks at the Ac-228 to Pb-212 ratio 

and includes results that are basically noise, one can expect to see quite a range of ratios beyond the 

anticipated 1:1 that will be very difficult to interpret in a meaningful way. Despite the uncertainties, 

NIOSH has used results that are below the DL to calculate the time-weighted OPOS and the annual 50th

percentile lung burden for the monitored worker population. An overview of the time-weighted OPOS in 

relation to the presumed detection limit is reproduced in Table 9. 

Table 9. 50th Percentile Time-Weighted OPOS Compared to the Pb-212 Detection Levels 

Given in NIOSH 2014a 

Year

Effective Bioassay

Date

# of Time-weighted 

OPOS Results

50thpercentile

(nCi)

DL

(nCi)

84thpercentile

(nCi)

1979 6/30/1979 124 0.039 0.156 0.129

1980 6/30/1980 149 0.032 0.123 0.116

1981 6/30/1981 129 0.035 0.108 0.121

1982 6/30/1982 167 0.054 0.121 0.147

1983 6/30/1983 167 0.036 0.122 0.120

1984 6/30/1984 322 0.042 0.1112 0.107

1985 6/30/1985 355 0.041 0.117 0.103

1986 6/30/1986 433 0.037 0.128 0.103

1987 6/30/1987 523 0.038 0.123 0.097

1988 6/30/1988 108 0.045 0.181 0.104

Observation 4: Given that discussions related to the method for analyzing coworker data are 

ongoing, a complete review of the in vivo coworker analysis is inappropriate until the timeweighted OPOS methodology is accepted by the Advisory Board. 
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6.0 REVIEW OF JOB TITLES SELECTED FOR COWORKER 

INTAKE ASSIGNMENT

Page 16 of NIOSH 2014a specifies that coworker intakes are assigned to unmonitored workers 

with the following job designations: chemical operators, fork truck drivers, laborers, 

transportation laborers, operations, production workers and maintenance personnel. During the 

September 2014 Fernald work group meeting, the specification of who would be assigned 

thorium coworker intakes was further discussed; specifically, ABRWH 2014 pg. 66-68 states: 

Mr. Hinnefeld: So for individuals then who have in vivo data, and that’s a lot of 

people because anybody who got in vivo’ed in the mobile counter or anybody who 

got in vivo’ed is going to have an in vivo result. We intend to use the in vivo data 

and missed doses and things like that if they are a job category that could have 

been involved in the repackaging. And we’d be pretty encompassing about that. 

You figure almost anybody in operations could have done that, most anybody in 

maintenance. Transportation could have been involved in it. You could have 

safety and health people. Might have security people there. So you’ve got to be 

pretty inclusive about the kinds of people that you would include in that. Even if 

it’s only probably a small group of people who actually did the overpacking, we 

don’t want to miss someone who should be included. So we would include in 

those, those people who might have been involved in some sort of exposure.” 

[Emphasis added.] (ABRWH 2014, pp. 66–68)6

It should be noted that “health and safety” as well as “security” job classifications were not 

included in the original list of “thorium workers” as defined in NIOSH 2014a.

 

Additional discussion during the September 2014 meeting further expounded on the application 

of coworker doses from 1979–1994: 

Mr. Hinnefeld: Yes. I think it's going to be a pretty wide net [of workers who 

would be applied thorium coworker intakes] because, you know, to avoid 

excluding people that should be included. 

Mr. Barton: It almost seems like it would have been better to just go from the 

other direction and say everybody gets it unless you were clearly an 

administrative worker, that kind of thing, because I mean --

Mr. Hinnefeld: Well, I think that's probably, I mean, we put some examples of 

jobs here that, and the jobs we listed were jobs that were identified I think by the 

training roster, right?’ But I think in actuality the approach will be unless this 

person was clearly administrative or cafeteria worker or, you know, someone who 

clearly is not going to be in a process area, unless it's somebody like that, they're 

going to be in. 

 

6

 For additional discussion of job title inclusion from ABRWH 2014, please refer to Attachment 2. 
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Based on these statements, it appears that the list of occupations in NIOSH 2014a may not be 

exclusive for the purposes of coworker model application. In order to gain better understanding 

of the practical application of the thorium coworker model based on occupation, SC&A 

examined the NIOSH/OCAS Claims Tracking System (NOCTS) files of Fernald claimants for 

job title information in relation to potential exposures. Claimants were selected to encompass 

the periods of interest (1978–1994) in addition to currently being designated with a probability of 

causation (POC) that is less than 50% (i.e., the claimants who would be effected by the 

application of coworker intakes). In the following analysis, SC&A has assumed that the job 

classifications of “security” and “health and safety” would be included in thorium coworker 

assignment per the first quote from ABRWH 2014 shown above. 

SC&A classified worker job titles into four main categories based on the current guidance 

concerning coworker intake assignment: 

 Category 1 – Not likely to be assigned intakes: the job title indicates an administrativetype worker for which entrance to radioactive areas is not probable. 

 Category 2 – Likely to be assigned intakes: the claimant job title qualifies as one of the 

aforementioned “thorium workers” (chemical operators, fork truck drivers, laborers, 

transportation laborers, operations, production workers, maintenance, security, health and 

safety personnel). 

 Category 3 – Unknown: these job types generally were similar to the job types in 

Category 2, but did not match exactly (for example: a “dump truck driver” which is 

similar to a “transportation laborer”). Additionally, job types that were actually 

designated as “unknown.”

 Category 4 – Potentially assigned intakes: job titles are such that they have the potential 

to enter radiological areas and incur thorium intakes, but are not specifically delineated 

under Category 2. 

It is the fourth category that is the focus of this section, although select claims that fall into 

Category 3 were also examined. An overview of the number of claims that were included in 

each of the above categories is shown in Table 10. As shown, a little over one quarter of eligible 

claimants would be assigned unmonitored coworker intakes based on the current list of job titles 

in NIOSH 2014a (Category 2). Based on SC&A’s judgment, nearly 50% of eligible claimants 

fall into Categories 3 and 4, where it is unclear whether coworker intakes would be assigned 

based on the current job title. 

Table 10. Breakdown of Job Types for Claimants Employed 1979–1994 with a POC of 

Less than 50% 

Job Type Category Potential for Thorium Exposure Number of Claims (% of Total)

1 Not likely 94 (24.5%)

2 Likely 108 (28.2%)

3 Unknown 25 (6.5%)

4 Potentially 156 (40.7%)
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Table 11 breaks down the claimant job types that fell into Category 2 (thorium intakes assigned 

to unmonitored works). “Laborer/Trades” workers made up the highest portion of Category 2 

claimants, with “chemical operator,” “maintenance,” and “health and safety” each comprising 

approximately 17% of the total. “Production workers” are showing no claimants; however, this 

is largely because these types of workers were subsumed by the other job types in Table 11, such 

as “chemical operator” or general “operations.”

Table 11. Breakdown of Category 2 Claimants by NIOSH 2014a Job Types7

NIOSH 2014a

Thorium Worker Types

Total Claimants

(% of Total)

Chemical Operator 18 (16.7%)

Fork Lift Operator 4 (3.7%)

Laborer/Trades 27 (25.0%)

Transportation 5 (4.6%)

Operations 7 (6.5%)

Production Workers 0 (0.0%)

Maintenance 19 (17.6%)

Health and Safety 19 (17.6%)

Security 9 (8.3%)

Table 12 contains a summary of 20 claimant files that SC&A classified as part of Categories 3 or 

4. As can be seen in the table, these job categories include: engineers, fire protection, 

technicians, analytical chemists, supervisors, inventory control, clerks, laundry, and various 

trades workers. Many of the sampled claimants indicated the potential for exposure to thorium 

in their Computer-Assisted Telephone Interview (CATI) reports. Additionally, many of the 

claimants who worked after 1988 were monitored via the In Vivo Examination Center (IVEC) 

facility, but were not monitored (or monitored sporadically) via the Mobile In-Vivo Radiation 

Monitoring Laboratory (MIVRML) prior to this time. Several claimant interviews also illustrate 

that individuals often worked in a variety of locations and capacities at Fernald, and it would be 

difficult to sufficiently establish that they did not enter areas where thorium exposure potential 

may have existed. 

Finding 3: Given the broad work locations and duties contained among worker job types not 

currently defined as a thorium worker in NIOSH 2014a, NIOSH should provide explicit 

instructions to the dose reconstructor that thorium coworker intakes should be assigned unless 

sufficient evidence exists that the claimant did not enter radiological areas where thorium 

exposure potential may have existed.

 

7 As noted previously, “security” and “health and safety” were not included in NIOSH 2014A, but were 

mentioned in ABRWH 2014. 
Effective Date:

November 24, 2014

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Page No.

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NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82. 

Table 12. Survey of Claimants with Job Titles Not Currently Included in NIOSH 2014A and a POC Less than 50%

Ref 

#

NOCTS Job 

Title(s)

Employment 

Start

Employment 

End Information Found in CATI DOE/DOL Information

1

[Redacted]

Engineer, 

Engineer II, 

[Redacted]

Engineer, 

[Redacted]

Coordinator, 

[Redacted] 

Coordinator

[Redact]/1955 [Redact]/1986 Claimant indicates potential exposure to thorium.

Work locations: "all over plant"

No in vivo monitoring.

DOL Job titles during pertinent period (1979+) 

[Redacted] Coordinator (1979-1984) and [Redacted]

Engineer (remaining employment)

Description of duties during latter part of employment 

is cut off.

2

[Redacted]

specialist, 

[Redacted]

specialist

[Redact]/1970 [Redact]/1993

Claimant indicates potential exposure to thorium.

Worked in every building and every room

Very descriptive job duties by area, notes that he performed 

thorium work in Pilot Plant building on a frequent basis.

MIVRML In Vivo monitoring in 1971 and 1972 

(results are in mg Th). Job listed as [Redacted], Plant 

listed H&S

IVEC monitoring results found for 1990–1995

Claimant was in [Redacted] until 1993.

DOL: Affidavit from former supervisor states: 

"[Redacted]."

DOL page 13 indicates worker was in the Health And 

Safety Department during the entire employment 

(specifies [Redacted] specialist only on the hire date)

[Redacted] 

Specialist [Redact]/1993 [Redact]/1995

[Redacted]

Specialist [Redact]/1995 [Redact]/1995

3

Technician III 

(part time) [Redact]/1974 [Redact]/1977

Claimant indicates potential exposure to thorium.

Main duties described as "analyzing uranium samples"

No In Vivo monitoring via MIVRML

In Vivo monitored in IVEC facility 5/89 (ND)

NOTE from DOL: Flour Fernald defines technician 

duties that are closer to a radtech or health physicist 

(2001, see page 42)

It appears all work was done in either the analytical 

lab or the medical department laboratory

Technician 

III/technologist I 

(full time)

[Redact]/1977 [Redact]/1989
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Table 12. Survey of Claimants with Job Titles Not Currently Included in NIOSH 2014A and a POC Less than 50%

Ref 

#

NOCTS Job 

Title(s)

Employment 

Start

Employment 

End Information Found in CATI DOE/DOL Information

4

Technical 

Assistant/ 

Technologist II

[Redact]/1981 [Redact]/1989

Claimant doesn't know if they were exposed to thorium.

Description of Location/Duties: "Technical building/lab, 

analytical/wet chemistry side, and at times was in the plant.... 

During production, analyzed production samples for levels of 

U235. During cleanup mode, analyzed environmental 

samples."

IVEC In Vivo result in August 1989 (< 0.68 nCi) 

NOTE: significantly higher than MDA for MIVRML

5

Lab tech, 

technologist III [Redact]1957 [Redact]/1960

Claimant indicates potential exposure to thorium.

Work locations were the "spec lab" and "radiochem lab."

Incident in mid 1980s exposed while retrieving uranium and 

thorium standards which were displaced when the lab 

building's basement flooded.

"first part of 1980s (until production ceased), [Redacted]. 

This was in a very fine powder form which had to be weighed. 

They had to put the powder in capsules which were put on an 

instrument that mixed them. The capsules were not sealed 

tightly and dust would come out of them during the mixing 

process. This work was done on an open bench with no hood."

Earliest in vivo results for thorium were in 1990 using 

the IVEC system (all results were "ND")

Analytical 

chemist [Redact]/1982 [Redact]/1996

6

Engineer, 

manager of 

[Redacted], 

project engineer

II

[Redact]/1983 [Redact]/1996

CATI indicates potential exposure to thorium

"They went through various buildings and [Redacted] in these 

buildings. Under this contract, he had to go into the Thorium 

Warehouse and this warehouse was in really poor condition... 

He said building 64 and 65 was the Thorium Warehouse 

(around 1985) this building was full, stacked three high of 

drums on skids."

CATI contains a very lengthy and descriptive account of duties 

and conditions.

Claimant was not monitored via the MIVRML

IVEC In Vivo monitoring in '91, '95, and '96 (Th-232 

was "ND")

No breathing zone samples were available for this 

claimant

7

[Redacted]

Supervisor, 

Engineer, 

[Redacted] 

Scientist

[Redact]/1984 [Redact]/2001

Claimant indicates potential exposure to thorium.

Worked throughout the site, though noted most production 

work he was involved in occurred in Plant 5.

In Vivo MIVRML count on 6/87 (0.17 nCi, Pb-212).

In Vivo by IVEC starting in 1989 and on a near 

yearly basis until (all were ND)

Four Breathing Zone results from 1996–1998 for 

U-238 only

DOL file states claimant was also exposed to thorium
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Table 12. Survey of Claimants with Job Titles Not Currently Included in NIOSH 2014A and a POC Less than 50%

Ref 

#

NOCTS Job 

Title(s)

Employment 

Start

Employment 

End Information Found in CATI DOE/DOL Information

8

[Redacted]

Engineer -

[Redacted] Staff 

Engineer

[Redact]/1982 [Redact]/1989

CATI performed with survivor.

Locations: Plants 2, 3, 5, 6, and 9

Duties: "He did [Redacted] in the different plants from 1985-

89. [Redacted]."

MIVRML In Vivo in 1984 and 85 (positive Ac-228 

result 0.23 nCi, recounted same day to 0.07 nCi)

IVEC In Vivo result in June 1989 (Ac-228 results 

<1.5 to <2.7 nCi)

DOL file has descriptions of exposure scenarios but 

not indication directly to thorium was made.

9

Pipe Fitter, 

[Redacted]

Engineer

[Redact]/1982 [Redact]/2005

CATI indicates potential exposure to thorium.

"Claimant said while working in Building 64 where the 

thorium repacking project was going to take place they did not 

have to wear PPE; they were working right next to the drums. 

He said when the process began workers were not permitted to 

enter the area without being behind a 2 foot concrete wall and 

working with robotics."

Duties:

Thorium Storage Tank (First Street) - they welded supports 

1992 (lasted 3 months)

Building 64 and 65 Thorium Repacking Project: 1991 (lasted 

6 months)

No MIVRML results located.

IVEC In Vivo result from 2001 (0.104 nCi, MDA 

listed as 0.536 nCi), 2000 (0.128 nCi, MDA 0.536), 

1999 (0.247 nCi, MDA 0.557), 1998 (<0.46 nCi), 

1997 (<0.47 nCi), 1994 (<0.4 nCi), 1994 (<0.85 nCi), 

1992 (<1.2 nCi), 1991 (<10 nCi), 1991 (<0.9 nCi), 

1991 (<1 nCi), 1990 (<1 nCi)

BZ results in 1996 for U-238, no thorium

DOL File states facilities worked in: "Buildings 2, 3, 

5, 6, 8, 9, 13, 45, 51, 64, 65, Silos, Pilot Plant, Tank 

Farm and thorium tanks and service building"

10 Hazardous Waste [Redact]/1982 [Redact]/2001

CATI performed with survivor.

Locations: "All locations as required"

Job titles: Electrician, Heating/Air Conditioning Maintenance

BZ results in 1995 and 1996 for U-238 in Plant 6

IVEC In Vivo: '90, '93-'95, '97-'01 (all "ND")

MIVRML In Vivo: '84 and '86 (Pb results are 

negative)

11

Sheet Metal 

Worker [Redact]/1981 [Redact]/1986 CATI indicates potential exposure to thorium.

"[Claimant] [Redacted]. This was during his whole time of 

employment."

Worked in Plants 1 and 6 during early employment period.

No MIVRML monitoring records.

Monitored in the IVEC facility in 1995.

Millwright [Redact]/1994 [Redact]/1998

12

[Redacted] [Redact]/1960 [Redact]/1971

Claimant indicates potential exposure to thorium.

"[Claimant] said [Redacted] was around the Quonset hut 

where the thorium was stored. [Redacted] said if they were 

around it when it was being moved s[Redacted]would have to 

wear a pencil dosimeter."

"[Claimant] said they always went in the backside and parked 

their bikes and went into the Pilot Plant to do different work. 

[Redacted] there were barium and thorium tanks in this area. 

[Redacted] said years later after the plant was closed down, 

people could not go into the area without a respirator and full 

protective clothing."

Claimant was not monitored via the MIVRML

Annual IVEC In Vivo monitoring beginning in 1995 

through 1999. U238 BZ results cover a 1 month 

period in 1995

[Redacted]

Control Tech [Redact]/1973 [Redact]/2003
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However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82. 

Table 12. Survey of Claimants with Job Titles Not Currently Included in NIOSH 2014A and a POC Less than 50%

Ref 

#

NOCTS Job 

Title(s)

Employment 

Start

Employment 

End Information Found in CATI DOE/DOL Information

13 Technician [Redact]/1980 [Redact]/1982 "[Survivor] said her [Redacted] went out in the field to gather 

samples"

Claimant was monitored in June 1980 in the 

MIVRML.

14 Cable splicer 

([Redacted])

[Redact]/1980 [Redact]/1990

Claimant indicates potential exposure to thorium.

Work locations: "All over the site, every man hole, building, 

closet, basement, lab, lab basement, Plant 6, K-65 Silos."

Claimant was badged every day on site.

"[Redacted]."

Claimant was not monitored.

15 [Redacted] 

Mechanic [Redact]/1979 [Redact]/2000

Claimant indicates potential exposure to thorium.

Work Locations: "Plant 1, 2, 3, 4, 5, 6, 9, Building 64, 65, 

Pilot Plant Storage, Lab Building, Laundry, Building 55"

"He had to go into the 64 and 65 buildings to [Redacted]. 

This was a high contamination area. The truck was used to 

grab the barrels of thorium from Manhattan Project days."

"He had the in-vivo/whole body counts once per year starting 

in the middle 1980's."

Claimant was not monitored in the MIVRML facility.

IVEC monitoring results found in '89, '94, '95, '97, 

and '98.

U238 BZ results from April to August 1995.

16

Laboratory 

technician: I, II, 

III: laboratory 

technician 

[Redacted]: 

[Redacted] 

supervisor

[Redact]/1963 [Redact]/2001

Claimant indicates potential exposure to thorium. 

Worked mainly in Laboratory, Water Plant, and Advanced 

Waste Water Treatment.

"Urine tests were given every month. Fecal samples were 

required only after some specific jobs. Whole body counts and 

breath samples were required twice per year."

Not monitored via MIVRML.

IVEC In Vivo monitoring in 1991 and 1995 through 

2001.

U-238 breathing zone samples starting in 1996.

17

Insulator [Redact]/1949 [Redact]/1950

Claimant doesn't know if they were exposed to thorium. Claimant was not monitored. Insulator [Redact]/1951 [Redact]/1964

Insulator [Redact]/1966 [Redact]/1980

18

Clerk, Clerk III, 

[Redacted]

Clerk, 

Supervisor, 

[Redacted]

Supervisor, 

[Redacted]Super

visor

[Redact]/1956 [Redact]/1993 CATI was declined.

Claimant was not monitored via MIVRML.

Claimant monitored in the IVEC facility from 1989 to 

1993.
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Health for factual accuracy or applicability within the requirements of 42 CFR 82. 

Table 12. Survey of Claimants with Job Titles Not Currently Included in NIOSH 2014A and a POC Less than 50%

Ref 

#

NOCTS Job 

Title(s)

Employment 

Start

Employment 

End Information Found in CATI DOE/DOL Information

19

Manager, 

[Redacted], 

[Redacted] Rep

[Redact]/1952 [Redact]/1988

Claimant indicates potential exposure to thorium. 

Work location is listed as the Health and Safety Building, 

Administration Building, Laboratory

Job duties during period of interest involved being the 

[Redacted] of nuclear material control.

"He opened and observed drums of U3O8, UO3, UF4, Uranium 

and Thorium metal and residues."

Claimant was not monitored via In Vivo.

20 [Redacted] [Redact]/1952 [Redact]/1993 CATI performed with survivor.

Survivor does not know if they were exposed to thorium.

Claimant has MIVRML in vivo monitoring result in 

1986

IVEC In Vivo monitoring in 1990, 1992 and 1993.
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Health for factual accuracy or applicability within the requirements of 42 CFR 82. 

7.0 REVIEW OF COWORKER ASSIGNMENTS BASED ON DAC 

MODEL (1990–1994) 

As outlined in NIOSH 2014a and summarized in Section 2, NIOSH proposes to use 10% of the 

derived airborne concentration (DAC) value that was in place during the 1990–1994 period. 

NIOSH 2014a cites the value of 5 × 10-13 μCi/ml as listed in DOE Order 4085.11 and 10 CFR 

835 Appendix A (U.S. 2014) for solubility class “W.” However, the DAC value for solubility 

class “Y” is a factor of two higher (1 × 10-12 μCi/ml). 

Finding 4: Unless sufficient evidence exists that thorium exposure potential at Fernald was 

restricted to solubility class “W,” NIOSH should consider using the more conservative and 

claimant favorable DAC value for solubility class “Y.”

Many workers were also monitored via the IVEC facility during this time period. In order to 

gain insight as to the number of unmonitored but potentially exposed workers at Fernald during 

this time, SC&A examined the monitoring records of claimants employed during this time who 

had POC values less than 50%. Overall, there were 252 claimants examined during the 1990–

1994 period,8 with nearly 75% monitored via the IVEC in vivo monitoring system. There were 

490 total IVEC monitoring results for these claimants, and SC&A only observed 3 results that 

were flagged as positive measurements.9

 

Of the 67 claimants that were unmonitored via the IVEC system in the 1990–1994 period, 45 can 

be considered job classifications that would have little (if any) exposure potential. These job 

titles include clerk, secretary, contract administrator, HR representative, computer programmer, 

occupational health nurse, contract attorney, mail courier, intermittent auditor, estimator, and 

data entry/analyst. 

The remaining unmonitored claimants had job titles which potentially could have been exposed 

to thorium. These job titles included trades workers (laborers, maintenance, painters, iron 

workers, heavy equipment operators), technologist, quality assurance, health physics, and 

engineers. SC&A closely examined these claims for evidence of unmonitored exposure to 

thorium that may not be bounded by the proposed approach of assigning 10% of the DAC. Each 

of these 22 claims is summarized in Table 13. Some key observations from Table 13 include: 

 Many claimants indicated that they worked “all over the site” during their employment 

(see cases 3, 4, 6, 8, 11, 12, 14, 15, and 18). 

 Some cases indicated that exposure in radiological areas where thorium exposure 

potential existed was intermittent or non-existent (see cases 1, 2, 4, 7, 10, 12, and 16–20). 

 External film badging was intermittent to non-existent in some cases, indicating the 

claimant did not enter radiological areas (see cases 6, 8, 11, 12, and 14–19). 

 

8

 Claimants with less than 3 months of employment during the 1990–1994 period were not included in this 

analysis; there were 19 claimants out of 271 that were excluded. 

9

 Curiously, the results flagged as positive (0.799, 0.46, and 0.68 nCi) were below the most commonly 

observed censoring level (~1.3 nCi). 
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 Many claimants monitored for external radiation and internal uranium exposure do not 

appear to have been exposed, since the film badge readings are zero and uranium 

urinalysis values are less than the MDA (see cases 1–7, 9, 10, 13–15, 20).

 One claimant indicated involvement in the thorium overpacking operations for 

approximately 1 year. This claimant stated that a respirator and two pairs of anticontamination suits were worn. While the date of the overpacking operation is not stated, 

the claimant has extensive BZ samples for thorium for approximately a 1-year period 

from 1996–1997 (see Section 8 for more discussion of this claim). 

Observation 5: Based on the review of the DOE records, CATI Reports, and associated job 

descriptions of 22 unmonitored claimant records, it is highly unlikely that the workers would 

have been continually exposed to airborne thorium levels above 10% of the DAC for the entire 

duration of their employment in the 1990–1994 period. 

As noted in Section 2, NIOSH 2014a seems to indicate that thorium exposure to unmonitored 

workers would be restricted to claimants who had submitted a pre-job fecal sample, based on the 

quote from page 16: 

1990–1994: Thorium workers with no in vivo results, but with pre-job fecal 

sample results during this employment period at Fernald are recommended to be 

assigned a dose based on a thorium air concentration of 5×10-14 μCi/ml (10% 

DAC), as a maximum potential exposure. 

However, the table on pages 12–13 of NIOSH 2014a does not delineate who is to be assigned 

thorium doses based on 10% of the DAC value. 

Finding 5: NIOSH should not restrict the assignment of thorium intakes to workers who 

submitted pre-employment fecal samples, but rather assign intakes based on the potential for 

radiological exposure (see discussion in Section 6).
Effective Date:

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Health for factual accuracy or applicability within the requirements of 42 CFR 82. 

Table 13. Examination of 22 Unmonitored Claimants in the 1990–1994 Period with Occupations with the 

Potential for Thorium Exposure

Ref # Job Title Emp. Start Emp. End Relevant Information

1

[Redacted]

Chemist [Redact]/1993 [Redact]/1996

CATI Work Location: Lab bldg.

Routine Duties: “Updated analytical procedures, -anion exchange chromatography,” "Procedures for 

compliance with the terms of radiation work permits were implemented and followed only in the last few 

months of [Claimant]'s employment"

External monitoring until up through 1993 (no accrued dose), IVEC monitoring in March '95 and April 

'96

Access Logs only indicate permission to access laboratory bldg.

2

Program 

Manager 

([Redacted])

[Redact]/1993 [Redact]/2002

CATI report only covers prior employment at Mound.

Claimant was badged but no external dose was accrued.

Access logs indicate entry into radiological areas for "auditing" purposes.

3

[Redacted]

Engineer [Redact]/1994 [Redact]/2000 CATI Work Location: All areas as required.

Film badged and uranium bioassayed throughout employment, no recorded dose.

4 Technologist [Redact]/1954 [Redact]/1995

CATI Work Location: All locations as required, esp. Technical lab bldg.

CATI Job 1990: [Redacted] engineer - production, 1991–1995: [Redacted] technical program specialist.

No external dose accrued after 1986, all urinalysis was less than the MDA during this time.

5

[Redacted] 

engineer [Redact]/1993 [Redact]/1993 CATI was declined.

No external dose accrued at Fernald.

6 Insulator [Redact]/1982 [Redact]/1990

CATI Work Location: Every building, inside and out.

CATI Job Duties: "Insulated lines and other equipment indoors and outdoors: heating, ventilating and 

air-conditioning lines, tanks, vessels, steam lines; removed and replaced insulation"

Film badge in 1990 was either "not assigned" or "not worn" for 8 of 12 months, the remaining months had 

zero recorded external dose. All uranium bioassay were below detection limits.

7

Health 

Physics 

Technician

[Redact]/1994 6/17/2002

CATI Job Title: "Analytical Technician"

CATI Work Locations: H&S/Bioassay Lab (1994-1998), Lab Bldg (1998+, worked in clean area)

No external dose accrued during employment, all uranium bioassay samples were below MDA.

8 Painter [Redact]/1989 [Redact]/1990

CATI Work Locations: All over facility, painted inside and out.

CATI and DOL files indicate claimant was badged during period but that physical employment at Fernald 

1989-1990 was not constant.

No internal or external monitoring during 1990.

9 Painter [Redact]/1994 [Redact]/1994

CATI Job Duties: Painter - Did grinding on rusty surfaces, did sandblasting and spray painting. 

[Redacted], later in CATI report states [claimant] wore [Redacted] and wore [Redacted]. "Worked near the 

2 giant silos."

No external exposure accrued, all uranium bioassay were less than the MDA.
Effective Date:

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Table 13. Examination of 22 Unmonitored Claimants in the 1990–1994 Period with Occupations with the 

Potential for Thorium Exposure

Ref # Job Title Emp. Start Emp. End Relevant Information

10 Ironworker [Redact]/1994 [Redact]/1994

CATI Job Duties: Water treatment plant - welding, grinding and bolting steel together. "[Claimant] was 

told they were working next to one building which was supposed to be the dirtiest building on the plant 

site."

No external exposure accrued, all uranium bioassay were less than the MDA.

11 Laborer/Maso

n

[Redact]/1955 [Redact]/1996

Survivor CATI Job Duties: Worked all over site. Dug holes, did brick work on silos, masonry repairs.

External monitoring ended in 1991 with a total of 16 mrem assigned (shallow and deep) from 1990 to 

1991. Only bioassay in period was in response to a UO3 incident in 1988.

12 [Redacted] 

Engineer [Redact]/1991 [Redact]/2003

CATI Job Duties: TACOS Trailers, Security, Administration, Lab , Work Trailers by Waste Pits and 

Silos, cell containment areas, perimeter of production areas where things were being torn down and dug 

up, services building... had to walk around the site and into different areas in order to do the job.

Was not assigned a film badge.

13 Ironworker [Redact]/1989 [Redact]/1990 CATI Job Duties: Ironworker. Used a torch and welded structural steel. Wore a respirator "daily"

No external dose was accrued during period, uranium bioassay was less than the MDA.

14 Laundry / 

painter [Redact]/1985 [Redact]/2001

CATI Job Duties: Work all over site. Sometimes wore a respirator when "fully dressed out." In laundry

- separated, washed, dried, and put clothes in bins. As i[Redacted] - went into contaminated areas, 

handled uranium cores using gloves. As painter - did motors, industrial painting, office work on 

weekends, airless spraying of roofs, hand painting or rollers, stenciled numbers on railroad cars.

External film badging ends in 1992, no external dose accrued. All uranium bioassay results were below 

the MDA.

Was monitored in both the MIVRML (June 1987) and IVEC facility (November 1989) - both results were 

non-detectable.

15 Welder/Iron 

worker [Redact]/1988 [Redact]/1990

CATI Job Duties: All over site. Welding hand rails around pits, decking, misc. duties, erecting building.

External badging was sporadic. Only monitored during June for 1990 (no dose accrued). Uranium 

bioassay results are less than the MDA. 

16 Pipefitter [Redact]/1991 [Redact]/1991

Had several other brief employment periods at Fernald prior to this period.

CATI Job Duties: Dismantling Plants 5 and 7 (this may have occurred during 1989 when claimant was 

monitored). Not all jobs required [claimant] to be around radioactive materials. 

No external monitoring during this period (1991).

17 sheetmetal 

worker [Redact]/1994 [Redact]/2001

CATI Job Duties: worked in heating/air conditioning. He would put duct work in any building as 

needed. He put grills and diffusers in rooms as the work progressed. He is not sure of the potential for 

radiation exposure. No one ever told him if he was working in radiation areas.

Claimant had baseline fecal samples for Th-228, Th-230, Th-232 prior to employment start date. 

No external dosimetry is available; claimant stated they were badged in CATI. Records indicate claimant 

was terminated in May 1994.

DOL records indicate he worked building a new office building "outside the fenced area"
Effective Date:

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Table 13. Examination of 22 Unmonitored Claimants in the 1990–1994 Period with Occupations with the 

Potential for Thorium Exposure

Ref # Job Title Emp. Start Emp. End Relevant Information

18 Electrician [Redact]/1994 [Redact]/1994

CATI Job Duties: All over the site. Claimant notes he was probably exposed to radiation 40-50% of the 

time. "at the Thorium Building they had concrete barriers that were four feet thick and twelve feet high. 

[Redacted]. He entered the area, drilled the holes, and set the pole; he was not wearing any form of 

protection."

Worked intermittently after 1994 as well, has several IVEC counts beginning in 1996.

Claimant not monitored for external radiation during 1994.

19 Cable splicer 

([Redacted])

[Redact]/1980 [Redact]/1990

From CATI: "[Redacted]."

From CATI: "Some weeks he'd be out there 8 hours per day, and other days he would be there for a few 

hours a day."

Claimant was not monitored for external or internal exposure.

20

[Redacted]/ 

Heavy 

Equipment 

Operator

[Redact]/1988 [Redact]/1990

CATI was declined.

TLD Issue forms indicate claimant was issued temporary access to Plant 5 as an ironworker during 1990, 

no external dose accrued. 

21

Laborer, 

Transportatio

n; Motor 

Vehicle 

Operator; 

Locomotive/ 

Switchman

[Redact]/1993 [Redact]/2006

CATI Job Duties: "[Claimant] worked in the Thorium Overpack site where she remotely operated a 

device that would move drums around. [Redacted] had to dress out and enter the building to get an 

electric forklift, went over to the actual boxes they loaded the drums in (overpacks), [Redacted] put a lid 

on the boxes and set them in an area for the Chemical Operators to clean, then the Rad Techs came in to 

survey them, if they were clean they were sent out to a driver on the "clean" area on process side and then 

they were sent to an area to be readied to ship offsite. [Redacted]... In the Thorium Overpack [Redacted]. 

[Redacted]... [Redacted] always wore a full-face respirator in the Thorium Overpack area... [Redacted]

had lapel monitoring done when [Redacted] was in Thorium Overpack when [Redacted] was dressed out 

in double sets of anti-contamination clothing."

Claimant has numerous breathing zone samples for isotopic thorium from April 1996 -April 1997.

External monitoring from start of employment.

22

On Site 

[Redacted] 

and 

Millwright

[Redact]/1988 [Redact]/1990 Radiation exposure investigation from May to June 1989 indicated: "worked in vicinity of thorium, but 

not close to the area" no other information is available including why the radiation exposure investigation 

took place. 10 mrem external dose was assigned (beta and gamma). Separate incident investigation a 

couple of months later indicates claimant wore a full face respirator. [Redact]/1990 [Redact]/1991
Effective Date:

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Health for factual accuracy or applicability within the requirements of 42 CFR 82. 

8.0 CHARACTERIZATION AND ANALYSIS OF BREATHING ZONE 

SAMPLING (1995–2006) 

As stated in NIOSH 2014a and summarized in Section 2, no coworker model is being proposed 

for the post-1994 period. Instead, the BZ results available in Fernald’s electronic radiation 

monitoring database (known as the HIS_20), as well as relevant in vivo monitoring, will be used 

to reconstruct thorium exposures to individual claimants. This issue was initially discussed 

during the September 2014 Work Group meeting; for a transcription of the relevant discussions, 

refer to Attachment 2. In addition to BZ samples specifically labelled as thorium, NIOSH 2012a 

states: 

In addition to isotopic thorium results in HIS-20, a review conducted in August 

2013 indicated five “custom” nuclides identified as: BL-13, BL-65, CELL 8, KS65 and RT-210.

No direct reference was provided as to what study was conducted and how it reached its 

conclusions. 

Observation 6: NIOSH should cite the aforementioned review and/or provide additional 

discussion of the underlying evidence that BL-13, BL-65, Cell 8, KS-65 and RT-210 are 

representative of thorium material. 

Nonetheless, the thorium-related BZ samples analyzed in this section were assumed to be 

Th-232, Th-228, BL-13, BL-65, CELL 8, KS-65 and RT-210.

10

 A breakdown of each sample 

type by year is shown in Table 14, and the sum of thorium BZ samples is plotted in Figure 1. 

Figure 2 plots the number of monitored workers per year from 1995–2006. 

Table 14. Breakdown of Thorium Breathing Zone Samples by Year 

Year BL-13 BL-65 Cell 8 KS-65 Th-228 Th-232 RT-210 Total Thorium 

Samples

1993 5 5

1994 51 51

1995 10 1,636 1,646

1996 749 7 3,905 4,661

1997 1,346 2 910 2,258

1998 214 9 123 346

1999 688 158 846

2000 223 5 227 455

2001 418 51 57 526

2002 620 8 860 1,488

2003 85 1,002 3 2,625 240 3,955

2004 839 1,776 5 682 31 3,333

2005 2 11,625 3 40 154 11,824

2006 9633 6 9 7 9,652

 

10 NIOSH 2014a also lists thorium-230 as an isotope of interest. However, thorium-230 is part of the 

uranium decay chain, not part of the thorium decay chain, and was therefore not considered in this report. 
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Figure 1. Total Number of Thorium Breathing Zone Samples by Year (1993–2006) 

Figure 2. Total Number of Monitored Workers by Year (1993–2006) 

As can be seen in Table 14 and Figure 1, very few samples exist in 1993 and 1994; however, the 

number of thorium BZ samples increases substantially in 1995. For most years, the thorium BZ 

samples were labelled “BL-65” or “Th-232.” Starting in 2004, samples labelled “KS-65” 

dominate the available data. Figure 2, which plots the number of monitored workers, generally 

mirrors the total number of samples observed in any given year. 
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Table 15 shows the average, median, 95th percentile, and maximum number of samples per 

worker per year. As seen, the maximum number of samples per worker in any given year was 

200. In the period of interest, 8 of the 12 years had a maximum number of samples per worker 

that was less than 100. The 95th percentile number of samples was less than 100 for all years. 

The average number of samples was generally less than 10 with the exception of 1996, 2003, 

2005, and 2006. The median number of samples per worker was always less than 10. 

Table 15. Number of Samples per Monitored Worker per Year 

Year Total Workers Average Median 95th Percentile Max

1993 5 1.0 1 1.0 1

1994 36 1.4 1 3.3 4

1995 260 6.3 2 31.0 68

1996 414 11.3 4 39.7 91

1997 232 9.7 2 49.5 108

1998 121 2.9 2 8.0 42

1999 100 8.5 2 42.0 76

2000 116 3.9 1 16.0 34

2001 85 6.2 2 33.2 41

2002 200 7.4 2 33.1 52

2003 353 12.3 2 61.9 200

2004 322 9.4 4 36.4 70

2005 555 21.3 6 91.0 171

2006 549 17.6 9 60.0 147

Attachment A of NIOSH 2014a provides an extensive list of thorium-related activities that took 

place from 1995 through 2006. It is likely that workers who were involved in such activities 

would perform thorium-related work until each individual project, such as thorium overpacking, 

was complete. 

As noted in Section 7, SC&A identified a claimant who was involved in the thorium overpacking 

project. The CATI Report for that individual stated the following: 

[Claimant] worked in the Thorium Overpack site where [redacted] remotely

operated a device that would move drums around. [Redacted] had to dress out 

and enter the building to get an electric forklift, went over to the actual boxes they 

loaded the drums in (overpacks), [redacted] put a lid on the boxes and set them in 

an area for the Chemical Operators to clean, then the Rad Techs came in to 

survey them, if they were clean they were sent out to a driver on the "clean" area 

on process side and then they were sent to an area to be readied to ship offsite. 

[Redacted]... In the Thorium Overpack she had to wear double sets of cloth 

coveralls. [Redacted] had to wear a cloth hood... [Redacted] always wore a 

full-face respirator in the Thorium Overpack area... [Redacted] had lapel 

monitoring done when [redacted] was in Thorium Overpack when [redacted]

was dressed out in double sets of anti-contamination clothing.

Based on the worker’s monitoring record, it is likely that this activity took place from May 1996 

to April 1997. The BZ samples for that worker are shown in Table 16. As shown in the table, 

the worker has 58 BZ results that span from May 9, 1996, to April 30, 1997, which comports 
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with the claimant’s statements that they were involved in overpacking for “one year.” However, 

it is also evident from the BZ records that samples were not taken on a daily basis or necessarily 

a consistent schedule. 

Table 16. Breathing Zone Results for Worker Involved in Thorium Overpack Project

BZ_DATE NUCLIDE SOL_ 

CLASS

RESPIRATOR 

_TYPE

DAC_ 

HRS_ 

PF

MDI_ 

DAC_ 

HRS

RESP_ 

WORN 

_FLAG

DAC_ 

HRS_ 

NOPF

LOCATION

NEW_ 

AIR_ 

CONC

05/09/1996 BL-65 W PAPR 0 0.003 Y 0.000 BLDG 65 0

05/20/1996 BL-65 W PAPR 0 0.004 Y 0.000 BLDG 65 0

05/28/1996 BL-65 W PAPR 0 0.003 Y 0.000 BLDG 65 0

05/31/1996 TH-232 W None 1.154 4.317 N 1.154 BLDG 64 0

06/03/1996 BL-65 W None 0.139 0.671 N 0.139 BLDG 64 0

06/06/1996 BL-65 W PAPR 0.002 0.003 Y 2.000 BLDG 64 0

06/12/1996 BL-65 W None -0.229 1.142 N -0.229 BLDG 64 0

06/17/1996 BL-65 W None 0.197 0.974 N 0.197 BLDG 64 0

06/18/1996 BL-65 W PAPR 0.001 0.003 Y 1.000 BLDG 65 0

06/20/1996 BL-65 W None -0.552 1.543 N -0.552 BLDG 64 0

06/24/1996 BL-65 W None -0.541 1.52 N -0.541 BLDG 64 0

06/27/1996 BL-65 W PAPR 0.007 0.003 Y 7.000 BLDG 65 0.007

07/02/1996 BL-65 W PAPR 0 0.003 Y 0.000 BLDG 65 0

07/10/1996 BL-65 W PAPR 0.01 0.003 Y 10.000 BLDG 65 0.01

07/22/1996 BL-65 W PAPR 0.004 0.003 Y 4.000 BLDG 65 0.004

07/31/1996 BL-65 W PAPR 0.016 0.004 Y 16.000 BLDG 65 0.016

08/14/1996 BL-65 W PAPR 0.001 0.003 Y 1.000 BLDG 65 0

08/21/1996 BL-65 W PAPR 0.016 0.004 Y 16.000 BLDG 65 0.016

09/03/1996 BL-65 W PAPR 0.014 0.004 Y 14.000 BLDG 65 0.014

09/12/1996 BL-65 W PAPR 0.043 0.004 Y 43.000 BLDG 65 0.043

09/24/1996 BL-65 W PAPR 0.03 0.003 Y 30.000 BLDG 65 0.03

09/27/1996 BL-65 W PAPR 0.035 0.003 Y 35.000 BLDG 65 0.035

10/03/1996 BL-65 W PAPR 0.098 0.003 Y 98.000 BLDG 65 0.098

10/15/1996 BL-65 W PAPR 0.061 0.004 Y 61.000 BLDG 65 0.061

10/17/1996 BL-65 W PAPR 0.048 0.002 Y 48.000 BLDG 65 0.048

10/29/1996 BL-65 W PAPR 0.037 0.002 Y 37.000 BLDG 65 0.037

11/07/1996 BL-65 W PAPR 0.005 0.003 Y 5.000 BLDG 65 0.005

11/20/1996 BL-65 W PAPR 0.054 0.003 Y 54.000 BLDG 65 0.054

11/27/1996 BL-65 W PAPR 0.066 0.002 Y 65.900 BLDG 65 0.066

12/03/1996 BL-65 W PAPR 0.086 0.002 Y 86.000 BLDG 65 0.086

12/12/1996 BL-65 W PAPR 0.036 0.003 Y 36.000 BLDG 65 0.036

01/08/1997 BL-65 W PAPR 0 0.004 Y 0.000 BLDG 65 0

01/10/1997 BL-65 W PAPR 0.134 0.003 Y 134.000 BLDG 65 0.134

01/29/1997 BL-65 W

PAPR 

COMBO 0.011 0.003 Y 11.477 BLDG 65 0.011

02/04/1997 BL-65 W None 0 2.55 N 0.000 BLDG 64 0

02/07/1997 BL-65 W PAPR HEPA 0.036 0.003 Y 36.170 BLDG 65 0.036

02/11/1997 BL-65 W None 0.908 2.384 N 0.908 BLDG 64 0

02/13/1997 BL-65 W None 0 1.234 N 0.000 BLDG 64 0

02/25/1997 BL-65 W None -0.028 0.931 N -0.028 BLDG 64 0

02/26/1997 BL-65 W None 0.208 1.457 N 0.208 BLDG 64 0

03/03/1997 BL-65 W PAPR HEPA 0.003 0.003 Y 2.569 BLDG 65 0

03/06/1997 BL-65 W None 0.042 1.217 N 0.042 BLDG 64 0

03/10/1997 BL-65 W None -0.111 1.059 N -0.111 BLDG 64 0

03/18/1997 BL-65 W None 0.826 1.25 N 0.826 BLDG 64 0

03/19/1997 BL-65 W None -0.238 1.608 N -0.238 BLDG 64 0

03/22/1997 BL-65 W None 0.125 1.118 N 0.125 BLDG 64 0

03/24/1997 BL-65 W PAPR HEPA 0.048 0.002 Y 48.423 BLDG 65 0.048

03/25/1997 BL-65 W None 0.042 1.217 N 0.042 BLDG 64 0
Effective Date:

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Table 16. Breathing Zone Results for Worker Involved in Thorium Overpack Project

BZ_DATE NUCLIDE SOL_ 

CLASS

RESPIRATOR 

_TYPE

DAC_ 

HRS_ 

PF

MDI_ 

DAC_ 

HRS

RESP_ 

WORN 

_FLAG

DAC_ 

HRS_ 

NOPF

LOCATION

NEW_ 

AIR_ 

CONC

03/27/1997 BL-65 W None -0.041 1.297 N -0.041 BLDG 64 0

04/08/1997 BL-65 W None 0.11 1.415 N 0.110 BLDG 64 0

04/09/1997 BL-65 W None -0.265 1.726 N -0.265 BLDG 64 0

04/14/1997 BL-65 W PAPR HEPA 0.03 0.003 Y 29.923 BLDG 65 0.03

04/17/1997 BL-65 W None 0.36 1.165 N 0.360 BLDG 64 0

04/21/1997 BL-65 W None -0.496 1.334 N -0.496 BLDG 64 0

04/23/1997 BL-65 W PAPR HEPA 0.043 0.003 Y 43.480 BLDG 65 0.043

04/25/1996 TH-232 W PAPR -0.001 0.009 Y -1.000 BLDG 65 0

04/29/1997 BL-65 W None -0.014 1.125 N -0.014 BLDG 64 0

04/30/1997 BL-65 W None 0.281 1.275 N 0.281 BLDG 64 0

Observation 7: It is not immediately clear what the temporal criteria were for collecting and 

analyzing breathing zone samples; however, it is evident that they were not necessarily collected 

on a daily basis. One likely possibility is that the breathing zone sample was measured over 

longer periods of time. However, documentation or other evidence should be provided to 

sufficiently establish that the breathing zone data are complete and represent comprehensive 

monitoring for thorium activities. 
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9.0 EVALUATION OF THORON EXPOSURES AT FERNALD 

As outlined in Section 2 of this report and described in NIOSH 2014a, exposures to Rn-220 and 

associated daughters (also known as thoron) are derived based on characterizing the source term 

(by weight) of thorium in specific buildings, establishing the release fractions for Rn-220 in 

stored material as well as materials in process, and finally converting it to exposure using an 

assumed volume of respirable air in each facility. This derivation also includes an equilibrium 

factor of 0.02 and an assumed occupancy time. 

Table F-5 of NIOSH 2014a gives the summary of thoron exposure estimates for various time 

periods. The time period that is relevant to this review is 1979–2006 and so the pertinent entries 

of Table F-5 are reproduced in Table 17. 

Table 17. Summary of NIOSH 2014a Thoron Exposure Estimates (1979–2006) 

Location 

& Time 

Period

Available Thoron Activity

Reduction & 

Calculation 

Factors

Eff. 

Facility 

VolumeLiters11

Rn-220/ 

Po-216 

Activity

(pCi/l)

Pb-212/

Bi-212 

Activity

WLM 

Per year

1954–1989

Various 

Storage 

Sites

300 metric Tons Th =

2 × 1013 pCi Rn-220 source term 

in Storage Facilities

RF12 1E-4

Feq13 2E-2

Focc.

14 3 mo 

per yr

1 × 107200 0.53WL 1.55WLM

1972–2006 

Final 

Closure 

Storage

300 metric tons Th =

2 × 1013 pCi Rn-220 source term 

in Storage Facilities

RF 1E-4

Feq 2E-2

Focc. 1 mo/yr

1 × 107200 0.53WL 0.53WLM

* For maximization purposes the mixing of the thoron and daughters during the processing of thorium is assumed to 

be in a 20’ hemispherical volume immediately around the release point, which in turn is assumed to be the process 

work station and for the short term stored thorium in the process facilities. For long term storage facilities the 

volume of the storage facilities was used. 

In this table, various assumptions are made that are discussed individually: 

1. The mass of thorium present in the storage site is assumed equal to 300 metric tons; 

however, this assumption is not referenced or explained. On the page preceding 

Table F-5 of NIOSH 2014a, the summary assumptions specify that 450 metric tons is to 

be used,15 although no explanation or reference is provided to justify this quantity as well. 

Table F-2 of NIOSH 2014a provides the thorium storage inventory in 1987, and shows 

338 metric tons in Building 68 and 351 metric tons in the Pilot Plant liquid tank. 

However, it is not evident that the quantities in Table F-2 are representative for the entire 

 

11 For maximization purposes the mixing of the thoron and daughters during the processing of thorium is 

assumed to be in a 20’ hemispherical volume immediately around the release point, which in turn is assumed to be 

the process work station and for the short-term stored thorium in the process facilities. For long-term storage 

facilities, the volume of the storage facilities was used. 

12 Release Fraction 

13 Equilibrium Factor 

14 Occupancy Factor 

15 NIOSH 2014a, pg. 132: “Long-term DOE storage – 100 to 450 MT in any given storage location, 450 

assumed.”
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period of interest (1979–2006). In addition, the values provided in Table F-2 appear to 

contradict other information in NIOSH 2014a, such as the unlabeled table on page 4 of 

the introduction, which also presents source term inventory for 1987. The total inventory 

of thorium material in this table is 2062.2 metric tons, in addition to the Plant 8 

silo/storage bins and thorium nitrate solution in the Pilot Plant storage tank. The total 

thorium inventory listed in Table F-2 is only 1,436 metric tons. 

2. The release fraction of Rn-220 assumed in NIOSH 2014a was based on few examples 

and did not provide adequate references to verify its validity. A release fraction of 1×10-6

was calculated based on measurements made for the Plant 8 storage silo (Example 3 on 

page 129 of NIOSH 2014a). In Example 2, a release fraction of the order of 1×10-3 was 

indicated for Building 65 storage facility operations in 1996. However, NIOSH indicated 

that the calculated release fraction cannot be used quantitatively, because of “many 

unknowns in this example: ventilation of the building, fraction of the stored material 

containers that were breached, location of the air sample in relation to leaking drums, 

etc.”

According to the report, Radon /Thoron Occupational Monitoring Decision Basis 

(Daniels 1997), the areas and practices in which personnel without respiratory protection 

were likely to have the highest potential exposure to thoron consisted of the Thorium 

Warehouse, Building 64; (Old) Plant 5 Warehouse, Building 65; Metals Fabricating Plant 

Thorium Furnace, Building 6; and Pilot Plant Wet Side, Building 13A; Quonset Hut #1, 

Building 60; and Breech of Containment of Thorium Nitrate Tank, T-2. The release 

fraction (RF) for the period of interest, 1979–2006, was assumed equal to 1×10-4 (as seen 

in Table F-5 of NIOSH 2014a), although no specific justification of this value is given. 

This RF is not based on measurements taken in areas with the highest potential for 

exposure to thoron, nor in areas with low exposure potential. 

3. The equilibrium factor adopted in NIOSH 2014a is equal to 0.02. According to Daniels 

(1997): 

...progeny equilibrium varies markedly with ventilation; standard 

equilibrium factors were not acknowledged. Although equilibrium values of 

2% to 10% have been documented at several FEMP locations, more precise 

studies are warranted to accurately relate 220Rn concentrations to WL 

[Working Levels].

The choice of the equilibrium factor was not based on measurements made in all 

buildings at representative times, so appears somewhat arbitrary. 

4. The occupancy time for the period of 1979–2006 was assumed to be 3 months per year 

for various storage sites up through 1989. Final closure storage facilities were assumed 

to be 1 month per year in the period of interest. There appears to be no distinct indication 

of which storage sites should be assigned occupancy times of 3 months per year versus 

1 month per year. Additionally, the justification for the assumed occupancy times is not 

well established and appears somewhat arbitrary. In order to credibly establish the 
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occupancy in a given location the work-load of affected personnel at different times and 

facilities must be considered. 

5. The specific activity of thoron in thorium bearing materials at Fernald was considered 

equal to 6.4 × 104pCi/g based on exposures ranging from 6 months to 1 year after 

separation, as well as an equilibrium fraction of Th-228/Th-232=0.65. This assumption 

is inappropriate to assume for all years in the waste repository. The document, Technical 

Basis for the Effective DAC for Th232 Stored in Building 65 (Allen 1995), assumes at 

least 95% equilibrium: 

The thorium in building 65 was put in the building in the 1960s and early 

1970s. Since the thorium was chemically processed before the 1970s, at least 

25 years have past. This would indicate that at least 95% of the equilibrium 

activity of the daughters has been reached. This equilibrium condition has 

been verified with analysis of the material in the building (see attachment B). 

Finding 6: The underlying assumptions employed in NIOSH 2014a to reconstruct doses to 

thoron are not well established or referenced. The assumptions concerning thorium source term 

inventory, release fraction, equilibrium factor, occupancy time, and specific activity of thoron 

must be thoroughly defined based on credible documentation and site specific records. 

Finding 7: It is necessary that NIOSH evaluate the thoron/thoron daughters’ exposures due to 

Ra-228. Independent of the time assumed after separation, it is necessary to evaluate if workers 

could have worked in areas where Ra-228 was handled or stored and consider the associated 

thoron exposures. As stated on page 105 of NIOSH 2014a, Ra-228 has a half–life long enough 

to permit its presence in the workplace for years independent of the original parent isotope (Th232). 
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REFERENCES 

ABRWH 2012. Letter to the Secretary of the Department of Health and Human Services –

Advisory Board Recommendation on SEC Petition. Advisory Board on Radiation Worker 

Health. May 29, 2012. 

ABRWH 2013a. Transcript of the Work Group on Fernald – 6/17/2013. Advisory Board on 

Radiation Worker Health, U.S. Department of Health and Human Services, Centers for Disease 

Control, National Institute for Occupational Safety and Health. 

ABRWH 2013b. Letter to the Secretary of the Department of Health and Human Services –

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ABRWH 2014. Transcript of the Work Group on Fernald – 9/3/2014. Advisory Board on 

Radiation Worker Health, U.S. Department of Health and Human Services, Centers for Disease 

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Allen 1995. Technical Basis for the Effective DAC for Th232 Stored in Building 65. D.E. Allen. 

Document No. SD-S&H-BAS-3025. Fernald Environmental Restoration Management 

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Bonfer, D.C., 1988. Thorium – A Search of Available Records at the FMPC. Document 

Number: PO(DCB)88-012. Westinghouse Materials Company of Ohio. November 15, 1988. 

Daniels 1997. Radon/Thoron Occupational Monitoring Decision Basis. R. Doug Daniels –

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Effective Date:

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Page No.

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SC&A 2012. Completeness and Adequacy of Thorium In-Vivo Records (1979–1989). S. Cohen 

and Associates, Vienna, Virginia. November 26, 2012. 

SC&A 2014. Memo to the SEC Issues Work Group - Status of Issues Relating to the 

Development of Coworker Models. S. Cohen and Associates, Vienna, Virginia. September 5, 

2014.

U.S. 2014. U.S. Code of Federal Regulations – 10CFR835 Appendix A: Derived Air 

Concentrations (DAC) for Controlling Radiation Exposure to Workers at DOE Facilities. CFR -

Title 10 – Chapter 3 – Part 835 – Appendix A. United States Government. January 1, 2014.
Effective Date:

November 24, 2014

Revision No.

0 – Draft

Document Description: 

Review of NIOSH Thorium Reconstruction Methods

Page No.

Page 45 of 50

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82. 

ATTACHMENT 1: ASSESSMENT OF THORIUM INQUIRIES (1977 

THROUGH 1985) TAKEN FROM LEIST 1985, ATTACHMENT 3 

Inq. 

No. Company/Location Contact Date

Description of 

Request

Quantity 

Req’d.

Purity 

Req’d

Material 

Shipped

Future 

Potential

78-P

3 M Co.

St. Paul, MN

February 

1985

Thorium Nitrate 

Crystals 2.72 MT >99.9% 2.09 MT Program Cancelled

77-P

Magnesium Electron, 

Inc.

Flemington, NJ

November 

1984

ThO2 (Application 

Unknown)

10–30 

MT/Yr. >98% Samples Possible

AP64.2Teledyne Cast Products

Los Angeles, CA

September 

1984 Metal Pellets Samples High None Unlikely

AP64.2NERCO

Portland, OR

September 

1983

ThO2 (Ceramic 

Applications) Samples 99.99% None Unlikely

70-P

Precision Castparts 

Corp.

Portland, OR

August 1983 ThO2 (ceramics for 

investment casting)

Up To 20 

MT/yr. 99.9%

Samples 

& 0.23 

MT

Possible

AP64.2GSD

Washington, DC May 1983

Convert Thorium 

Nitrate Stockpile to 

ThO2

About 

3,200 MT Unknown NA Needs DOE Approvals

AP64.2Phone Poulenc

Freeport, TX May 1983

Convert Thorium 

Nitrate By-Product 

to Sell

Unknown >99.5% NA

Needs 

Capital & 

Approvals

295-

A

EG&G

Idaho Falls, ID

December 

1982

Thorium Metal 

(R&D Samples) NA 99.9% None None

289-

A

Los Alamos National 

Lab

Los Alamos, NM

July 1982

ThO2 (R&D 

Studies with 

EG&G)

1 MT 99.9% 1.15 MT Unlikely

AP64.2

Department of 

Commerce

Washington, DC

June 1982 Convert Thorium 

Nitrate to Dry Form 54 MT/Yr. Unknown NA Need DOE Approvals

283-

A

EG&G

Idaho Falls, ID May 1982 ThO2 (R&D Studies) 1 MT 99.9% 1 MT Unlikely

66-P

Battelle Pacific NW Lab

Richland, WA March 1982 ThO2 (Canadian AECL Program) 0.65 MT 99.9% None Unlikely

65-P

Ronson Metals Corp.

Newark, NJ

November 

1981

Metal or Oxide 

(Electronics 

Applications)

27 kg/Yr. 99.5% None Unlikely

277-

A

Sandia National Lab

Albuquerque, NM

October 

1981

ThO2 (R&D 

Studies) 2 MT 99.9% 2 MT Unlikely

64-P

General Atomics

San Diego, CA March 1981

ThO2 (For Public 

Service of 

Colorado)

7.5 MT 99.9% 6.764 MT Possible

AP64.2San Jose State U.

San Jose, CA

February 

1981 Metal Foil Samples 99.9% None None

265-

A

Euratom

Karlsruhe, W. Germany

February 

1981

ThO2 (Application 

Unknown) Unknown 99.9% None Unlikely
Effective Date:

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Revision No.

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Document Description: 

Review of NIOSH Thorium Reconstruction Methods

Page No.

Page 46 of 50

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution.

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ATTACHMENT 2: EXCERPTS FROM THE ABRWH TRANSCRIPT 

REGARDING SELECTION OF WORKERS FOR THORIUM INTERNAL 

DOSE ASSIGNMENT AND EXPOSURE POTENTIAL POST-1994

Beginning on Page 68 of ABRWH 2014:

16

R. HINNEFELD: Yes, I mean, the building was, yes, health and safety building was torn down. 

The in vivo facility was, actually to a good extent I think it outlived the health and safety 

building. It was almost sort of a little appendage on it but I think it outlived the health and safety 

building by a little bit.

So for individuals then who have in vivo data, and that's a lot of people because anybody who 

got in vivo'ed in the mobile counter or anybody who got in vivo'ed is going to have an in vivo 

result. 

We intend to use the in vivo data and missed doses and things like that if they are a job category 

that could have been involved in the repackaging. 

And we'd be pretty encompassing about that. You figure almost anybody in operations could 

have done that, most anybody in maintenance. Transportation could have been involved in it. 

You could have safety and health people. Might have security people there.

So you've got to be pretty inclusive about the kinds of people that you would include in that. 

Even though it's only probably a small group of people who actually did the overpacking, we 

don't want to miss someone who should be included. So we would include in those, those people 

who might have been involved in some sort of exposure.

And, in fact, this period then extends into the remediation period as well but people who might 

have been exposed, they will get, if they have in vivo data they will a missed dose. And this goes 

through '94. I'll explain that in a little bit.

If you don't have in vivo data, then from '79 through '89, which is I guess the mobile period, 

that's when we have all, for the mobile period we have all the bioassay results that were done 

because they were kept in log books, in a log book or essentially a book of results. And so all the 

in vivo results for anybody, regardless of whether they're a claimant or not, we have those.

After 1990 when you go to the FITS system, we only would have the in vivo results for claimants. 

We don't have the comprehensive list of in vivo data, so the coworker model then is intended to 

address the years of the mobile monitoring when we have all the in vivo data.

For the years '90 to '94 when we no longer have all the in vivo data, all we have is claimant, you 

know, data from the claimants, we're proposing to use the control level that was exercised...

 

16 Note: Page numbers may not reflect Privacy Act-cleared version of transcript.
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Continued on Page 76 of ABRWH 2014.

MR. STIVER: One kind of overarching question I guess is I see in a lot of these thorium White 

Papers that have been going on, exchanging over the course of several years now, I guess, you 

know, your contractor, ORAU, always mentions that this would be applied to thorium workers, 

you know... A lot of your papers have identified we're going to apply this towards thorium 

workers and, you know, our research has shown that prior to about 1994 I guess when some of 

this new information came along, this really job- identifying information is kind of sparse to say 

the least.

And so, you know, the two SECs that were based on thorium really give it to everybody because, 

you know, it's just impossible to say who was, you know, exposed at what time in what building 

and so forth.

So I see that kind of logic is kind of being carried through in this paper, so I'm just kind of 

curious. Do you guys have other sources of information you'd be able to find that identify job 

categories prior to 1994?

MR. HINNEFELD: Well, I mean, there are --

MR. STIVER: Anything new I guess that we haven't looked at before?

MR. HINNEFELD: There was a fair amount of thorium work done by subcontract. If you read 

the paper, there's Project 1, 2 and 3.

MR. STIVER: Yes.

MR. HINNEFELD: Project 1 was done by IT Corporation, which was removal of the thorium 

from silos within Plant A. Project, or now it wasn't 2 or 3. It was the neutralization of the UNH. 

The Pilot Plant was done by Chem-Nuclear. And so, I mean, those are separate, distinct 

categories of people we know who do that.

There's some information here about a list of job titles of people who were trained I think for one 

of the thorium projects, you know, the kinds of people who were involved in that.

But I really, I don't know that we're ever going to find, like, names that we can say this person 

specifically went in and, at least not with the data available.

MR. STIVER: So you're saying that the three projects, all three of them used subs for the entire 

amount of work?

MR. HINNEFELD: No, no, no.

MR. STIVER: They were separate?

MR. HINNEFELD: No, thorium overpack was in-house.
Effective Date:

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MR. STIVER: Project 3 was the --

MR. HINNEFELD: Project 3 was in-house.

MR. STIVER: Okay.

MR. HINNEFELD: Project 1 was bins and silos and I forget what -- Oh, Project 2 was the 

outside storage. Yes, that was in-house.

MR. STIVER: Okay, that was in-house as well.

MR. HINNEFELD: Yes.

MR. BARTON: Seemed like from your description and reading the paper there's kind of a list of 

pretty broad job categories. Those would be, at least being proposed to be applied up through 

1994 or just for the in vivo period through '89, because it seems like once you get to 1995 you're 

kind of saying that they're pretty much defined by the fact that they have breathing zone.

MR. HINNEFELD: Yes, current breathing zones. From '95 forward they're defined by having 

breathing zone air sampler for thorium.

MR. BARTON: Right. So you're essentially saying there's no coworker model after 1994?

MR. HINNEFELD: Correct.

MR. BARTON: Right, okay. I guess another question I had about that with the breathing zone 

specifically and I haven't been able to dive into the references yet but, I mean, when we say that 

breathing zone is provided for all thorium workers, I mean, are we talking, you know, the main 

handlers of it?

But what about, like, you know, sort of ancillary workers that might have been in close vicinity, 

like a security guard or something like that? I mean, would they have to also been included in 

the breathing zone?

I mean, is there a possibility that you'd have workers who do have exposure potential but maybe 

weren't considered thorium workers for the purposes of breathing zone?

MR. HINNEFELD: Well, by this time, by '94, things were pretty controlled. You know, Fluor 

had been there a while and they brought a lot of rigor to these things, even more so than 

Westinghouse.

MR. BARTON: So pretty much if you were in the vicinity of a project, you were going to have a 

breathing --

MR. HINNEFELD: A project, you know, a thorium work area would, you know, the thorium 

area would be defined.
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MR. BARTON: And anyone entering that --

MR. HINNEFELD: And if you're going into this, into the thorium radiological area or the 

airborne, you know, potential airborne area, everybody had a BZ with them.

You know, I went in. When I would go in to do an observation, you know, I was some pencilpushing manager, I wore a BZ. That's what I was. I didn't do any real work.

MR. STIVER: So you didn't have to worry about, like, janitors and staff?

MR. HINNEFELD: If they went in, they wore BZ.

MR. STIVER: You're pretty confident that --

MR. HINNEFELD: Yes.

MR. STIVER: -- anybody who went in that area had --

MR. HINNEFELD: You went into that area, you wore a BZ.

MR. STIVER: And all that data is captured?

MR. HINNEFELD: It is all in HIS-20.

MR. STIVER: It seemed like a pretty high bar to set, that we have no unmonitored workers 

during this period of time.

MR. HINNEFELD: I'm pretty sure there are not. I mean, it was controlled. The area was 

controlled, you know, to the point of having manned, you know, manned patrol and so I'm pretty 

sure that anybody who went into the thorium area from '95 on had a BZ sampler.

MR. STIVER: Now, back to Project 1 and 2, I know that IT did the Project 1 in '89. Were they 

also doing the D&D of Plant 8 silo, did they also do all of the, do it from start to finish?

MR. HINNEFELD: Yes, I believe, IT did that whole thing.

MR. STIVER: Okay, all right. Those kind of questions, whether there were somebody else or 

some of the in-plant workers might have done the D&D but it was all contracted out then?

MR. HINNEFELD: Well, I don't really remember. The paper reports that that was all part of 

Project 1, of the silos, the bins, not Plant 8 itself. You know, Plant 8 was still there when that 

project was done.

MR. BARTON: So I might have heard the answer and it just passed right through one ear and 

out the other. I'm trying to get a handle on how we're assigning the proposed coworker intakes. 

Like I said, there's a list of workers that, and one of them is, you know, operations, you know 
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what I mean, pretty broad category. It seems like what you're actually saying is that unless you 

were a secretary or something like that, an administrative position, then you wouldn't even have 

come close to these sites of operations so it's not appropriate to apply coworker intakes. I mean, 

is that essentially what we're saying or, I mean.

MR. HINNEFELD: Yes. I think it's going to be a pretty wide net because, you know, to avoid 

excluding people that should be included.

MR. BARTON: It almost seems like it would have been better to just go from the other direction 

and say everybody gets it unless you were clearly an administrative worker, that kind of thing, 

because I mean --

MR. HINNEFELD: Well, I think that's probably, I mean, we put some examples of jobs here 

that, and the jobs we listed were jobs that were identified I think by the training roster, right?’

But I think in actuality the approach will be unless this person was clearly administrative or 

cafeteria worker or, you know, someone who clearly is not going to be in a process area, unless

it's somebody like that, they're going to be in.