Draft 

ADVISORY BOARD ON 

RADIATION AND WORKER HEALTH 

National Institute for Occupational Safety and Health 

STATUS REPORT ON RESUSPENSION ISSUES AT THE 

NEVADA TEST SITE 

Contract No. 211-2014-58081

Revision 0 

Prepared by 

John Mauro, PhD, CHP 

Lynn Anspaugh, PhD 

Robert Barton 

Amy Meldrum 

S. Cohen & Associates 

1608 Spring Hill Road, Suite 400 

Vienna, Virginia 22182 

July 2015 

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 pre-decisional 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

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NTS Resuspension Issues Status 

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Status Report on Resuspension Issues at the Nevada 

Test Site 

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Task Manager: 

__________________________ Date:____________ 

Arjun Makhijani, PhD 

Supersedes: 

N/A 

Project Manager: 

__________________________ Date:____________ 

John Stiver, CHP 

Peer Reviewer(s): 

 Arjun Makhijani, PhD 

 John Stiver 

 

 

Record of Revisions 

 

 

 

 

 

 

Revision 

Number

Effective 

Date Description of Revision

0 (Draft) 07/21/2015 Initial issue
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TABLE OF CONTENTS 

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

Executive Summary .........................................................................................................................7

1.0 Background ........................................................................................................................10

2.0 Major Overarching Issues ..................................................................................................14

3.0 The Air Sampling Data and Their Usefulness in Reconstructing Ubiquitous Internal 

Environmental Doses to NTS Workers ..............................................................................15

3.1 The Use of Air-Sampling Data for Pu-239/240 .....................................................17

3.2 Other Radionuclides ...............................................................................................20

3.3 Earlier Time Periods ..............................................................................................21

3.4 Radionuclides that Had Decayed Before the RIDP Data Were Collected .............24

3.5 Calculations of Dose from Inhalation ....................................................................25

4.0 Dose from Ingestion of Soil ...............................................................................................27

5.0 The Mass Loading Approach for Inhalation ......................................................................27

6.0 Applications of the TBD Procedure in Actual Dose Reconstruction for Claimants ..........31

References ......................................................................................................................................35

Appendix A: Latest Issues Resolution Matrix Dated December 14, 2012 ...................................38

Appendix B: Partial Evaluation of the McArthur Data and Their Use in the TBD ......................42
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LIST OF FIGURES 

Figure 1. Air-Sampling Locations in 1997 .................................................................................. 18

Figure 2. Resuspension Factor as a Function of Time after Deposition ...................................... 23

Figure 3. Accrued Dose (Coefficient) for Extra-Thoracic Lymph Nodes (LNet) as a 

Function of Time Following Intake of Pu-239 ................................................................. 27

Figure 4. Screenshot of Word Document Included in Some NOCTS Files Providing 

Guidance on the Application of Environmental Intakes ................................................... 34

LIST OF TABLES 

Table 1. Calculations of Dose with Use of the Mass-Loading Approach (1 mg/m3) .................. 29

Table 2. Calculations of Dose from the Nine Radionuclides also considered in Table 2 ............ 30

Table 3. Characterization of the Application of Environmental Doses to 

Relevant NTS Claimants................................................................................................... 31

Table 4. Environmental Intake Rates Observed in Relevant NTS Dose Reconstructions ........... 32

Table 5. Observations Concerning Ambient Environmental Dose Assignment 

to NTS Claimants .............................................................................................................. 33
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ABBREVIATIONS AND ACRONYMS 

Advisory Board 

or ABRWH Advisory Board on Radiation and Worker Health 

Bq Becquerel 

CAD chronic annual dose

Ci Curie 

cm centimeter 

DC dose coefficient

DOE U.S. Department of Energy 

DR dose reconstruction 

EE energy employee 

ER evaluation report 

ET extra-thoracic

g gram 

GSD geometric standard deviation

HPGe high purity germanium 

hr hour 

ICRP International Commission on Radiological Protection 

IMBA Integrated Modules of Bioassay Analysis 

IREP Interactive RadioEpidemiological Program 

kt kiloton 

LANL Los Alamos National Laboratory 

LLNL Lawrence Livermore National Laboratory 

LNet extra-thoracic lymph nodes 

m meter 

m

2

square meter 

m

3

cubic meter

μCi/cc microcurie per cubic centimeter 

mg milligram

mm millimeter 

mR milliroentgen 

μR microroentgen 
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ML mass loading 

NaI sodium iodide 

nCi nanocuries 

NIOSH National Institute for Occupational Safety and Health 

NOCTS NIOSH/OCAS Claims Tracking System 

NTS Nevada Test Site 

OCAS Office of Compensation Analysis and Support 

ORAUT Oak Ridge Associated Universities Team 

ORERP Off-Site Radiation Exposure Review Project 

pCi picocuries 

POC probability of causation 

R Roentgen 

REECo Reynolds Electrical and Engineering Company 

rem roentgen equivalent man 

RIDP Radionuclide Inventory and Distribution Program 

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

SEC Special Exposure Cohort 

SNL Sandia National Laboratories 

Sv Sievert 

t ton 

TBD technical basis document 

TIB technical information bulletin 

TTR Tonopah Test Range 

WG Work Group 
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EXECUTIVE SUMMARY 

A detailed review and analysis is provided of the sections of the Nevada Test Site (NTS) 

Technical Basis Document (TBD) describing the methods, data, and assumptions used to derive 

the annual radionuclide inhalation rates for workers at the NTS from chronic environmental 

exposures to radionuclides resuspended from soil (ORAUT 2012). It is important to note that the 

TBD acknowledges that internal doses from airborne activities cannot be reconstructed for 

outdoor operational activities between 1951 and 1992 when various tests, events, and incidents 

occurred. This is the reason Special Exposure Cohorts (SECs)1 were granted for these time 

periods. The current TBD addresses the reconstruction of what is referred to as “environmental 

doses,” which represent time periods and exposure settings that are best described as more 

quiescent conditions. This distinction is important when evaluating models, data, and

assumptions used in the TBD for this specific purpose. The present version of the TBD does not 

consider enhanced local exposure to material resuspended as a result of activities such as soil 

disturbances on the NTS. The latter activities would be expected to produce much larger 

exposures to employees in the field. 

Before proceeding with our review of the TBD, we would like to commend NIOSH for making 

use of the considerable amount of air- and soil-sampling data that has been compiled at the NTS 

as a means to assign at least some doses to NTS workers who are not covered by the SEC. In 

addition, notwithstanding some of our commentaries and criticisms of the TBD, we would like to 

acknowledge the creative and innovative strategies NIOSH has adopted in making use of the 

available air-sampling and soil-sampling data and the Hicks’ tables to extrapolate back in time as 

a means to reconstruct doses before these data became available. 

Given our understanding of the scope of the TBD and the methods used to reconstruct long-term 

chronic inhalation doses from the resuspension of radionuclides in soil, SC&A has a number of 

concerns that should be discussed with the NTS Work Group (WG), including the following: 

1. On page 12, Section 4.1.2 of the TBD, the following statement is made: 

Therefore, dose reconstructions for individuals employed at NTS during the 

period from 1951 through December 31, 1992, but who do not qualify for 

inclusion in the SEC, can be performed using these data as appropriate. 

We have a concern with this statement, because the TBD actually provides a protocol for 

reconstructing the internal doses from resuspension of radionuclides from January 1, 

1963, through December 31, 1992.2

 This statement should be corrected. We also have a 

concern with the following statement made in Appendix A of the TBD: 

If an internal exposure was suspected, bioassay was performed. Managing 

radioactive material in the form of devices was episodic and limited to a few 

 

1

 SEC #00055; January 27, 1951, through December 31, 1962, and SEC #00070 and #00084; January 1, 

1963, through December 31, 1992. 

2

 . The logical end point is December 31, 1992, but ORAUT (2012) includes the date 2000. 
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workers (e.g., radiation safety and industrial hygiene personnel, miners, and 

experimenters). These workers are identified on the rosters that were 

published before the event, and these workers are likely to have bioassay 

results in the DOE records. 

It is our understanding that an SEC was granted in part because there was inadequate 

bioassay data and many employees were exposed in situations where there were no 

rosters, thereby precluding the ability to develop a coworker model. This topic was 

discussed thoroughly during the NTS WG meetings on October 29, 2008 (ABRWH 

2008); April 23, 2009 (ABRWH 2009a); and December 15, 2009 (ABRWH 2009b). 

2. A method for analyzing chronic environmental exposures associated with resuspension 

processes is provided for the time period beginning in January 1, 1963, approximately 

6 months after the “last above ground test.”

3

 Inspection of the Anspaugh et al. (2002) 

resuspension factor equation reveals that by 180 days after deposition, the resuspension 

factor drops down to about 5 × 10-9/m. For earlier times, closer to the end of aboveground testing, the resuspension factors, according to the Anspaugh model, are orders of 

magnitude greater. SC&A believes that it is possible to back extrapolate the dose 

reconstruction to mid-1962, at the end of aboveground testing. Such calculations would 

be more complete and will likely reveal substantially higher doses from resuspension 

during that 6-month period. The intended time period of coverage for these calculations 

should be discussed and agreed upon with the members of the NTS WG. There is no 

reason that the important time period of July 1962 to December 31, 1962, is not included 

in the material in the TBD. Further confusion on this point arises from the following 

statement on page 42 of the TBD under “Instruction to Dose Reconstructors:”

With the exception of cases that can be worked using the bounding assumption 

in ORAUT-OTIB-0018 (ORAUT 2005), environmental inhalation and 

ingestion intakes listed in Tables 4-7 and 4-11, respectively, shall be applied 

starting in 1964. 

OTIB-0018 seems to be an inappropriate reference within the context of outdoor 

chronic exposures at the NTS. OTIB-0018 is more appropriately employed 

indoors at sites that have a comprehensive health physics and airborne monitoring 

program, which is not the case for the NTS. 

3. It is important that the time period to be covered be carefully considered by the members 

of the NTS WG. SC&A believes that the logical time period to be covered is July 1962 

through December 31, 1992. The method of environmental occupational dose 

reconstruction is strongly based upon measurements of the concentrations of Pu-239/240 

 

3

 ORAUT (2012) repeatedly refers to Small Boy (July 14, 1962, “low” yield) as the last aboveground test. 

Actually, the last aboveground test was Little Feller I (July 17, 1962, “low” yield). Other aboveground, surface, or 

cratering tests during the month of July 1962 were Sedan (July 6, 1962, 104 kt, fission yield less than 30%); Little 

Feller II (July 7, 1962, “low” yield), and Johnnie Boy (July 11, 1962, 500 t). Sedan and Johnnie Boy were cratering 

events. The Sedan event was the most important event in terms of release of radionuclides. The event data are 

taken from DOE (2000). 
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in air samples starting in 1971. SC&A was originally concerned that the air-sampling 

locations were not representative of the locations where workers were exposed. We 

originally detailed these concerns in the Anspaugh report dated October 21, 2008 

(Anspaugh 2008). At that time, these concerns were based on the assumption that our 

interest was in “active environments” where operational activities were ongoing. 

However, within the context of using these air-sampling data as a means to characterize 

airborne Pu-239/240 concentrations during relatively quiescent conditions, referred to as 

chronic environmental exposure, these concerns are greatly diminished. It is important to 

note that the current scope of dose estimation from residual radioactivity is limited to 

environmental dose not associated with work activities. Exposure during work-related 

activities that disturb soil is not included within the scope of the TBD. 

4. The soil radionuclide inventory data collected in the 1980s by the Radionuclide Inventory 

and Distribution Program (RIDP) (Kordas and Anspaugh 1982; McArthur 1991) 

characterized soil contamination at the site during the 1980s. However, the TBD 

extrapolates back in time to derive the soil contamination levels that were present on 

January 1, 1963,4so that doses could be reconstructed from the resuspension process 

during early years following the end of aboveground testing. One of the limitations of 

the back extrapolation process used in the TBD is there is evidence that some areas were 

decontaminated (McArthur 1991, p. 34) before the RIDP measurements were made. 

Also, significant contamination occurred in Areas 20 and 30 from Plowshare activities 

after 1963, and the Baneberry event in 1970 produced major contamination in Areas 8 

and 12. These concerns need to be addressed in terms of the degree to which the TBD 

remains scientifically sound and claimant favorable, notwithstanding these events. 

5. Derivation of the concentration of relatively short-lived radionuclides in soil for January 

1, 1963, employed the Hicks’ tables (Hicks 1982) for the Small Boy event that occurred 

on July 14, 1962. In fact, the contamination in soil on January 1, 1963, reflects fallout 

from numerous tests that resulted in surface contamination, such as the Sedan test on 

July 6, 1962, and Little Feller II on July 7, 1962, which occurred shortly before Small 

Boy, and Little Feller I that occurred after Small Boy on July 17, 1962. As such, NIOSH 

should address whether tests shortly before and after Small Boy on July 14, 1962, could 

also have contributed substantively to the fallout levels in soil derived for January 1, 

1963. In a related matter, the protocol used in the TBD to account for fractionation is

overly simplistic and appears to rely primarily on the Small Boy event. NIOSH will need 

to demonstrate that the approach used to account for fractionation does not substantively

underestimate doses. 

6. The levels of contamination observed in soil by the RIDP performed in the 1980s 

captured some contamination that occurred many years subsequent to the termination of 

aboveground testing. This is a concern that needs to be addressed, because the TBD is 

based on the assumption that all radionuclides observed in soil in the 1980s were as a 

result of aboveground testing that occurred in July 1962. However, some of the 

contamination was deposited many years later. NIOSH should explain how this affects 

 

4

 SC&A believes that this back extrapolation should have been done to July 1962. 
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the dose reconstruction process. In a related manner, the TBD makes use of the 

Anspaugh equation to derive resuspension factors in order to calculate airborne mass 

loadings and associated intake rates after January 1, 1963. NIOSH needs to discuss how 

these resuspension factors might be affected if there are locations where soil 

contamination occurred well after January 1, 1963. 

7. In order to prepare tables of doses to each organ and from each radionuclide as a function 

of time [which would have required an enormous number of Integrated Modules of 

Bioassay Analysis (IMBA) runs], NIOSH elected to prorate all doses based on the intake 

rate of Sr-90 beginning on January 1, 1963, and moving forward in time as the 

resuspension factors decline according to the Anspaugh equation and the radionuclide 

concentrations decline by radioactive decay. A review of the methods used to perform 

these calculations, as provided in Appendix A of the TBD, reveals that errors have been 

made in its use of equation A-2, which could profoundly affect the dose fractions 

provided in Figures A-5 through A-11, and the doses calculated and reported in 

Tables 4-9, 4-14, and A-10.

8. A comparison of actual NIOSH dose reconstructions with the guidance provided in the 

TBD reveals that there are discrepancies and inconsistencies between the TBD guidance 

and the actual dose reconstructions. These inconsistencies need to be discussed with the 

WG. 

In summary, SC&A is in accord with the basic approach employed by NIOSH, but finds that the 

starting date should be pushed back to mid-1962. There are also some errors in the calculations 

that need to be corrected and some assumptions that need to be refined. SC&A has provided 

some interim calculations based on simpler approaches that can be used as quality checks, which 

should help in our discussions of the TBD with the WG. In addition, SC&A generally agrees 

with NIOSH that reconstructing environmental doses during the period of atmospheric 

testing would be too complex to be feasible as a general matter. However, if there are some 

claimants with non-SEC cancers who might benefit from a partial environmental dose, this issue 

might be revisited on a case-by-case basis. 

1.0 BACKGROUND 

This report describes SC&A’s understanding of one of the issues that has been a matter of 

ongoing discussion; namely Issue 5 in the Issues Resolution Matrix as provided in “Update of 

the Nevada Test Site (NTS) Issues Resolution Matrix Based on the SC&A Review of the NIOSH 

Site Profile for the Nevada Test Site,” prepared by Arjun Makhijani, Ph.D. and delivered to 

NIOSH and the Board on December 12, 2012 (SC&A 2012). The issue, as originally stated by 

SC&A, is as follows: 

Resuspension model and resuspension factor are not scientifically defensible or 

claimant favorable, due to a variety of factors. Doses may be underestimated by 

an order of magnitude or more. Mass-loading approach would be preferable for 

internal dose. 
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This current report addresses Issue 5 (and related issues) and its status as we understand it as of 

June 2015. As a means to begin this discussion, the following was excerpted directly from 

Section 5.3, “Discussion,” of SC&A’s December 12, 2012, report: 

The intake due to resuspension of previously deposited radionuclides was among 

the issues discussed in great detail during the 2006–2009 review of site profile 

and SEC issues. This review included preparation of papers by SC&A and 

NIOSH, as well as revisions of the environmental occupational dose section of the 

site profile. The following list summarizes the major points in the discussions, 

which are documented in papers, as well as in the transcripts of the NTS WG 

meetings in the 2006–2009 period. 

SC&A prepared a paper on resuspension elaborating on the problems found in 

the site profile and recommending approaches to intake estimation (Anspaugh 

2006). In particular, this paper suggested that a mass loading model was more 

appropriate than using resuspension coefficients for times more than 2 years after 

the initial radionuclide deposition. 

NIOSH developed and published a mass loading model in response to SC&A’s 

review of the issue (NIOSH 2007). SC&A prepared a brief response (Anspaugh 

2007). 

NIOSH also developed a model based on estimating resuspension intakes using 

measured air concentration data (Rollins 2007). This new model replaced the 

mass loading model and was incorporated into Rev. 1 of the Occupational 

Environmental Dose volume of the site profile (ORAUT 2008, Attachment A). 

SC&A published a review of ORAUT 2008 (Anspaugh 2008). This was discussed 

extensively at the NTS WG meeting held on October 29, 2008 (ABRWH 2008). 

NIOSH revised its occupational environmental dose site profile (ORAUT 2010) to 

reflect the fact of the SEC having been granted, but mostly left Rev. 1 (ORAUT 

2008) unchanged. The air concentration model was carried over into Rev. 2 of 

the document (ORAUT 2010, Attachment A). 

NIOSH responded to a number of SC&A comments made during its review or 

during WG discussions, such as adjusting for decay and selective deposition of 

refractory radionuclides. During the WG discussions, SC&A raised some 

questions about the choice of soil contamination values and, for some situations, 

such as the omission of Area 30 soil data (ABRWH 2007a, p. 20, for instance) and 

higher values for resuspension with higher mass loading values for short periods 

of time (ABRWH 2007b, p. 46, for instance) that are still not fully addressed. 

During WG discussion of SC&A’s review of Rev. 1 of the occupational 

environmental dose site profile (ORAUT 2008b), NIOSH stated that occupational 

environmental doses were not meant to be applied to workers in the field. For 
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these cases, NIOSH proposed to apply an occupational internal dose, either by 

using bioassay measurements or applying a coworker model. Occupational 

environmental dose was meant to be applied to situations where workers were not 

in areas where testing or test preparations were being carried out (ABRWH 2008, 

pp. 150–184). 

Finally, SC&A notes that the revised ER [Evaluation Report] stated that 

environmental occupational dose could be calculated on a claimant-favorable 

basis for NTS workers (NIOSH 2010, pp. 65–66). 

In “Section 5.4 Status and Conclusion” of SC&A (2012), it states the following:

The NTS SEC-00084 for the period January 1, 1963, to December 31, 1992, was 

granted on the grounds of infeasibility of estimating internal dose with sufficient 

accuracy (NIOSH 2010). In reviewing the extensive and complex record, it 

appears to SC&A that NIOSH and SC&A were in agreement that occupational 

environmental dose can be estimated. Therefore, it appears to SC&A that this is 

a site profile issue that could be used to calculate partial doses for non-covered 

cancers. 

The most recent version of the occupational environmental dose site profile does 

not address some of the issues raised in Anspaugh (2008) and the subsequent WG 

discussion in October 2008 (ABRWH 2008) for estimating partial doses for nonSEC cancers. It would therefore appear to merit review. 

One of the challenges both NIOSH and SC&A encountered in addressing alternative methods for 

estimating the chronic long-term airborne dust loadings that many workers experienced pertained 

to the use of the resuspension-factor approach versus the mass-loading approach, including other 

strategies that used air-sampling data. Early in our deliberations, NIOSH agreed that the massloading approach might be best suited for these circumstances and adopted a bounding mass 

loading of 5 mg/m3, which was discussed during several WG meetings. The mass-loading 

approach was considered feasible, because contamination levels in soil were comprehensively 

characterized by RIDP reports authored by McArthur5

and others (the results can be expressed in 

either pCi/m2

or Bq/g of surface contamination), and together with appropriate empirically 

derived resuspension factors, expressed in terms of pCi/m3per pCi/m2(or 1/m), could be used to 

derive airborne concentrations of radionuclides. Alternatively, by using the RIDP data to 

express the radionuclide concentrations in the soil in units of Bq/g, the airborne radionuclide 

concentrations could be estimated by the mass-loading approach. Specifically, numerous reports 

cite a range of airborne mass loadings expressed in units of mg/m3and, knowing the surficial 

concentration of radionuclides in soil, the airborne concentration of radionuclides can be 

estimated. Both methods are widely used to estimate the airborne concentrations of 

radionuclides due to resuspension processes. As will be discussed later, NIOSH, in its latest 

 

5

 The latest Occupational Environmental Dose TBD, ORAUT-TKBS-0008-4, Rev. 3, cites six reports 

(McArthur and Kordas 1985, 1987; McArthur and Mead 1987, 1988, 1989; McArthur 1991) which provide the 

results of soil contamination investigation for different NTS areas. McArthur (1991) provides a useful overview of 

the entire program, which covered many years in the 1980s. 
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TBD, elected to use neither the resuspension-factor approach nor the mass-loading approach.6

Instead, NIOSH elected to use actual plutonium air-sampling data that were collected beginning 

in the early 1970s and soil-sampling data (which included many radionuclides) collected in the 

1980s as a means to reconstruct exposures during the 1980s, but also as the basis for backextrapolating exposures to January 1, 1963. However, as will be discussed later in this report, 

NIOSH also employed resuspension factors to address internal exposures during a portion of this 

time period. 

Earlier in our deliberations, and at the suggestion of SC&A, NIOSH attempted to use the massloading approach to estimate the airborne concentration of radionuclides, because it had access to 

a considerable amount of soil-contamination data as reported in numerous investigations 

(McArthur and Kordas 1983, 1985; McArthur and Mead 1987, 1988, 1989; McArthur 1991) as 

part of the RIDP. However, NIOSH stated that, when applying a bounding mass loading of 

5 mg/m3to the radionuclide concentrations observed in soil to estimate the airborne 

concentrations of radionuclides, the derived doses were “just extraordinary” (ABRWH 2014, pp. 

75–76) and were “extremely high and not reasonable” (ABRWH 2014, p. 69). However, these 

calculations were not documented (ABRWH 2014, p. 75). SC&A believes that such calculations 

may have been in error, and in any event, the calculations should have been documented and 

presented to the NTS WG, as NIOSH had previously indicated that they intended to use such an 

approach (ABRWH 2009a).

With this summary of the historical background of the status of the resuspension issue as of 

December 14, 2012, the following presents (1) a discussion of NIOSH’s use of air-sampling data 

as a means to estimate chronic radionuclide intake rates from the resuspension of ubiquitous 

levels of radionuclides in soil; (2) the use of the resuspension-factor approach, which also makes 

use of data from the RIDP, but applies resuspension factors to these data to derive the airborne 

radionuclide concentrations during the years 1963–1965; (3) a description of the use of the 

Hicks’ tables in order to account for short-lived radionuclides; (4) a description of the massloading approach, which was not used by NIOSH, but which makes use of estimates of the 

chronic outdoor dust loading and the RIDP data characterizing the radionuclide concentrations in 

soil; and (5) an evaluation of how NIOSH has implemented their approach in 241 relevant claims 

for energy employees (EEs) who were onsite after 1962 and had a probability of causation 

(POC) less than 50%. 

To a large extent, the descriptive material provided here is kept at the conceptual level, because 

the actual implementation of the strategies as adopted in the TBD is quite complex. We do go 

into some detail when discussing some of the deficiencies in the basic strategy adopted by 

NIOSH and the data used to implement that strategy. 

Given the long and complex history of issues related to reconstructing environmental doses at the 

NTS, it is instructive to begin with the latest version of the issues resolution matrix, which is 

reproduced in Appendix A. Inspection of Appendix A and a review of the most recent version of 

the NTS Occupational Environmental Dose TBD (ORAUT 2012) dated August 24, 2012, reveals 

 

6

 The Anspaugh et al. (2002) resuspension equation was used only to increase the airborne concentrations 

for the years of 1963–1965. 
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that SC&A, NIOSH, and the Advisory Board need to revisit the available data, and how it can be 

best used to reconstruct environmental internal doses at the site. These are the topics that we 

believe require further discussion. 

The August 24, 2012, version of the Occupational Environmental Dose TBD (ORAUT 2012) is 

extensive and describes briefly the myriad activities that took place at the NTS. Inspection of the 

table of contents alone provides insight into the complexity of the activities and incidents that 

took place at various locations throughout this large site at various times that resulted in the 

deposition of radionuclides onto the soil in both localized and widespread areas due to 

aboveground testing that terminated in 1962, belowground testing that continued up to 1992, 

Plowshare activities that were active from 1962 through 1968, tunnel operations, drill-back 

operations, and other activities too numerous to reiterate here. After carefully reading the 2012 

TBD, it appears that NIOSH acknowledges that doses to operational personnel cannot be 

reconstructed from January 27, 1951 (the beginning of aboveground testing), through December 

31, 1992 (the end of all testing). These exposures are referred to as “occupational exposures,” as 

opposed to “environmental exposures.” This distinction is important, because it was not entirely 

understood during previous discussions. Specifically, occupational exposures are those 

associated with specific activities, campaigns, and incidents (which NIOSH acknowledges 

cannot be reconstructed with sufficient accuracy and therefore establishes the basis for the 

SECs). However, to NIOSH’s credit, the TBD tries to find ways to reconstruct environmental 

doses to workers who are not covered as members of the SEC class, which include primarily 

workers with certain types of cancers, including skin cancer, prostate cancer, chronic 

lymphocytic leukemia, and other types. Environmental exposures and their associated internal 

doses are best thought of as exposures to the long-term average airborne dust loadings that 

represented a sort of ubiquitous cloud over most of the site and resulted in a baseline of internal 

exposures to all workers at the site. It is the purpose of this report to explore what doses can and 

cannot be reconstructed for the workers not covered by the SECs, and the most appropriate 

strategies and data that can be used to at least assign some doses to these workers. As will 

become apparent, the strategy adopted by NIOSH is best referred to as a combination of the airsampling, soil-sampling, and resuspension-factor approaches, while an alternative plausible 

strategy explored here by SC&A is best referred to as the mass-loading approach. 

As will be discussed in subsequent sections of this report, we are in agreement with the use of Pu 

air-sampling data and with the 1980s soil-characterization data for long-lived radionuclides as a 

starting point for deriving ubiquitous chronic internal exposures during these time periods and 

using these data, along with the Hicks’ tables, to back-extrapolate internal doses to the 1960s, 

including the selected use of resuspension factors. We have some reservations about use of longlived radionuclide soil data that we will explain, and we believe that the mass-loading approach 

could be used instead of resuspension factors for the purpose of deriving airborne concentrations 

of radionuclides for time periods when actual airborne sampling data are not available. 

2.0 MAJOR OVERARCHING ISSUES 

There are two overriding major issues that should be discussed by the members of the WG. The 

first is whether some attempt should be made to distinguish the potential doses to persons 

actually working in the field versus those who were simply performing clerical or other 
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activities. The distinction between these two groups of workers had been discussed during the 

April 23, 2009, meeting of the WG (ABRWH 2009a), and NIOSH had indicated that they would 

develop a dual approach. As can be inferred from the above, NIOSH has abandoned the concept 

of a dual approach and has developed a model only for those persons not actively engaged in the 

field. SC&A agrees with this strategy. Much of the rest of this document discusses the TBD as 

it currently exists, identifying areas that appear to be overly simplistic, in error, or difficult to 

understand. 

The second overarching issue is the time period to be covered for calculations of environmental 

occupational exposure. The contents of the present version of the TBD relate only to time 

periods from January 1, 1963, and beyond. The person who wrote the introduction to the TBD 

apparently intended that the document should cover the period “...from 1951 through December 

31, 1992....”7

 There is no apparent reason for a starting point of January 1, 1963, other than 

using material that had been previously prepared by NIOSH in an effort to reconstruct doses and 

recommend denial of SEC petition #00084. SC&A agrees that it is virtually impossible to 

consider environmental doses all the way back to 1951, but believes that the logical starting time 

for the calculation of such doses is mid-July 1962, at the “end” of atmospheric testing, and not 

January 1, 1963.

3.0 THE AIR SAMPLING DATA AND THEIR USEFULNESS IN 

RECONSTRUCTING UBIQUITOUS INTERNAL 

ENVIRONMENTAL DOSES TO NTS WORKERS 

Inspection of the TBD reveals that one of the sources of data that is useful for performing partial 

dose reconstructions includes internal dosimetry data (i.e., bioassay data) that are available for at 

least some workers. Of course, such circumstances can only be addressed on a case-by-case 

basis,8and, as such, are not discussed any further here. However, we do need to discuss other 

sources of data that might be useful for partial dose reconstructions. For example, Section 

4.2.1.2 of the TBD describes data collected at air-sampling stations. In the past, SC&A was

critical of these data, because they were not always located at the most useful locations for 

reconstructing internal exposures to workers and may very well have missed time periods that 

could have been associated with elevated levels of airborne radionuclides. In addition, the types 

of data were not always as complete as we would have liked in terms of quantifying the 

concentrations of specific radionuclides that could have been important contributors to internal 

 

7 An important distinction has been made in the current TBD concerning the “end” of atmospheric testing 

in July 1962. The word end is in quotations, because there continued to be major Plowshare activities that released 

large quantities of radionuclides through 1968, and there were major breaches of containment, such as the Baneberry 

shot in 1970. 

8

 It is noteworthy that at NTS WG meetings, NIOSH and SC&A agreed that sufficient bioassay data do not 

exist for workers who were potentially exposed on the flats and even in the tunnels. And, given that the stated goal 

is to provide a method for the reconstruction of occupational environmental doses from 1951 through 1992, the 

usefulness of bioassay data for dose reconstruction is suspect mainly because no bioassays were performed during 

the earlier periods of the operation of the NTS. Such material was discussed thoroughly during the NTS WG 

meetings on October 29, 2008 (ABRWH 2008); April 23, 2009 (ABRWH 2009a); and December 15, 2009 

(ABRWH 2009b). 
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dose. We believe that NIOSH would not have any dispute with these types of concerns 

regarding the air-sampling data. However, the current TBD now focuses on those circumstances 

where the air-sampling data can be used. In addition, we also discuss alternative strategies that 

can supplement the use of air-sampling data to perform partial dose reconstructions.

Given this perspective, the following sections describe SC&A’s understanding of how NIOSH 

plans to perform partial dose reconstructions using available air-sampling data and the RIDP data 

as the starting point for these calculations. Specifically, the 2012 TBD explains that NIOSH 

plans to take advantage of the airborne Pu-239/240 concentration data collected from numerous 

continuously operating air-sampling stations. NIOSH also plans to take advantage of the 

radionuclide soil inventory data compiled in the 1980s under the RIDP to understand the mix of 

long-lived radionuclides in soil at various locations during the time period that the data were 

collected. 

Given knowledge of the airborne concentration of Pu-239/240 (and also other isotopes of 

plutonium) at a given location and given time period, and also the concentrations of long-lived 

radionuclides in soil at those locations and time periods (e.g., Am-241, Co-60, Cs-137, Pu-238,

Pu-239/240, Sr-90, Eu-152, Eu-154, and Eu-155) provided by the RIDP, one can estimate the 

airborne concentrations of these radionuclides at those locations and time periods by taking 

advantage of the measured ratio of Pu-239/240 to other radionuclides in soil and then 

multiplying that ratio by the measured concentration of Pu-239/240 in air at that location. It 

seems obvious that the inhalation and ingestion of radionuclides can be reconstructed where the 

air-sampling data are representative of the radionuclide concentration in soil and locations of the 

workers. As discussed later in this report, we identify some concerns regarding whether the airsampling data are representative of the radionuclide concentrations in soil because of the 

locations of the air samplers. However, we also discuss some of the strategies NIOSH has 

adopted for using these data in a manner that helps to ameliorate many of these concerns. This 

topic warrants some discussion with NIOSH and the WG. 

NIOSH argues that, not only can they perform partial dose reconstructions for those time periods 

where data are available characterizing the Pu-239/240 levels in soil and in air, but they can use 

that data to back extrapolate to time periods where air-sampling data and soil-inventory data are 

limited or entirely lacking. However, there are many challenges associated with trying to use the 

existing air-sampling data and soil-inventory data as a means to reconstruct internal doses for 

time periods and locations where such data do not exist. Many of these limitations and strategies 

for their resolution are described in Appendix A to the TBD and explored further in this report. 

For earlier years, the concentrations of the radionuclides in soil and air will be higher because of 

subsequent radioactive decay, natural attenuation, and cleanup operations. Radiative decay is 

readily accounted for. However, natural attenuation and cleanup are more problematic. 

Specifically, the concentrations of long-lived radionuclides measured in soil in the 1980s are 

used to extrapolate back to the 1960s without taking into consideration natural attenuation or 

cleanup. The implications are that the concentrations of radionuclides in soil in the 1960s and 

1970s could have been considerably higher than those derived by back-extrapolating using 1980s 

data if natural attenuation is not taken into consideration. In addition, there are locations that 

were remediated before the 1980s. For those locations, the actual concentrations of 
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radionuclides in soil prior to remediation would be higher than those derived by backextrapolating using 1980s data, if remediation is not taken into consideration. As will be 

discussed later in this report, NIOSH was very selective and conservative in choosing which soil 

contamination data collected in the 1980s were used to perform the back-extrapolations. It 

appears that this strategy, as implemented by NIOSH, helps to ameliorate this concern. This 

matter will require some discussion with NIOSH and the WG.

An additional concern with the back-extrapolation process is that many of the shorter-lived 

radionuclides present in soil in the 1960s and 1970s will have decayed away by the time that the 

RIDP data were collected in the 1980s. In order to overcome this challenge, and at least try to 

assign environmental doses to workers during the early years (i.e., from January 1, 1963,

9

into 

the 1980s), NIOSH proposes to take advantage of the Hicks’ tables, with due consideration of 

fractionation and the fact that the potential for resuspension of fresh fallout is far greater than 

that for aged fallout. The following presents a brief description of how the RIDP data and the 

Hicks’ tables can be used for back-extrapolating the radionuclide concentrations in soil prior to 

the time that the RIDP data were collected. Much of the material summarized in the following 

sections was excerpted from Attachment A of the TBD. However, as the material is 

summarized, we point out some of the deficiencies associated with performing these types of 

back-extrapolations; deficiencies that warrant further discussion by the WG. 

3.1 THE USE OF AIR-SAMPLING DATA FOR PU-239/240 

As explained in Attachment A to the TBD, air samples were collected at the NTS from 15 

stations from 1971 to 2001 and measured to determine the airborne concentration of Pu-239/240; 

additional sampling stations were later established at a number of other locations, such as Areas 

2, 3, 4, 7, and 9 (see Figure 1, which is reproduced from the TBD). As explained in the TBD, the 

locations of the air-sampling stations were based on a number of factors, including areas where 

elevated plutonium levels might be expected, areas where large numbers of workers were 

located, and primarily areas where electric power was readily available. In addition, in 1988, the 

number of air-sampling stations was increased as a result of the requirements of DOE Order 

5400.1. Table 4-210 of the TBD presents a detailed summary of the average atmospheric 

concentrations of Pu-239/240 observed under this program by year and location, as originally 

reported in annual NTS environmental reports. 

 

9

 Again, SC&A does not understand why NIOSH chose to start their calculations of environmental 

occupational dose at January 1, 1963. Their method could have been used to calculate doses for the July 1962 

period through December 31, 1992. 

10 These data are reproduced in Table A-1 of the TBD, but the column headings on page 62 are mislabeled. 
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 Source: TBD, Figure 4-1 

Figure 1. Air-Sampling Locations in 1997 
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For the moment, let us not concern ourselves with the correlation between the location of the 

particulate air-sampling stations and the locations of the measured concentrations of 

radionuclides in soil. If we were interested in estimating the annual intake of Pu-239/240 due to 

resuspension from soil, we would want to know the degree to which these sampling locations 

represent the Pu-239/240 concentration in the breathing zone of workers at the time a given 

worker was at a given location. Clearly, the data are not adequate for that purpose. But 

currently NIOSH is not trying to reconstruct the intake of radionuclides for a particular person at 

a particular time. NIOSH is trying to estimate the average intake by individuals who might have 

been present at any or many locations over a given time period, but who were not working in the 

field where soil disturbances were taking place. Data in Table 4-2 of the TBD show the average 

annual concentration (pCi/m3) of Pu-239/240 over time and location for 20 areas and from 1971 

through 2001, as reported in annual NTS environmental reports. On its surface, it would appear 

that this is a comprehensive air-sampling program. However, keep in mind that the site is over 

1,000 square miles of desert and mountain terrain, where the types of tests and incidents varied 

widely as a function of time and location. 

In order to place a plausible upper bound on the annual intake of Pu-239/240 for a given worker 

for a given year for chronic environmental exposures, one might assign the highest average 

annual concentration of Pu-239/240 measured among all areas for a given year, considering all 

locations. For example, for 1974, the average airborne Pu-239/240 concentration across all 

sampling locations was 8.64 × 10-5 pCi/m3and the maximum was 2.11 × 10-4 pCi/m3. Using the 

maximum average concentration as the Pu-239/240 concentration to which the worker was 

continuously exposed in 1974 certainly seems to be a reasonable upper bound for chronic 

environmental exposure. Keep in mind that this is a baseline exposure for chronic environmental 

exposures and not occupational exposures associated with specific operational campaigns. It 

appears that, at a minimum, a Pu-239/240 annual inhalation intake rate for a particular year can 

be assigned at least for years where air-sampling data were collected. However, there are years 

and locations where no data are provided. For those locations and years, there is some question 

whether plausible upper bound Pu-239/240 intake rates can be assigned based solely on airsampling data. 

In principle, these data could also be used to reconstruct Pu-239/240 intakes for time periods 

before air-sampling was performed. However, it could be argued that such calculations could 

overestimate Pu-239/240 exposures during earlier years if no plutonium was deposited at a given 

location at an earlier time period of interest. Of course, such a situation would tend to 

overestimate the plutonium exposures at those earlier time periods. Conversely, it could also be 

argued that the plutonium deposited in soil in the earlier years may have weathered or have been 

removed between the time of its deposition and the time that the air-sampling data were 

collected. This would tend to result in an underestimate of the plutonium concentrations in air 

prior to the institution of airborne monitoring program. Clearly, extrapolating backward in time 

has its challenges, but we believe that these challenges should not preclude an attempt to assign 

at least some environmental doses to workers. For example, by selecting the location and year 

with the highest annual average airborne plutonium concentration for the purposes of partial dose 

reconstruction, there is a level of assurance that reconstructed internal exposures are claimant 

favorable for all workers during those time periods, and also for earlier time periods where backextrapolation was required. One could also argue that this strategy would be reasonable for 
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earlier time periods and locations, even for locations that were cleaned-up prior to the 

commencement of the air-sampling program. 

3.2 OTHER RADIONUCLIDES 

In an effort to assign doses due to additional radionuclides that were not included in the analyses 

of the air-sampling data, NIOSH plans to make use of data collected under the RIDP. The RIDP 

soil-inventory data were collected in the 1980s and estimate the total inventory (Ci) of nine11

radionuclides in each of 21 areas. The areal size of each NTS area is provided, which therefore 

allows one to estimate the average areal deposition density of each radionuclide in the year the 

data were collected. Table 4-4 of the TBD presents the inventory (Ci) of the 9 radionuclides in 

each of 21 areas as detected above background (which includes consideration of global fallout as 

part of ubiquitous background levels in soil) in the soil-inventory program, along with the size of 

each area in square miles.12 It is important to note that Pu-239/240 is included in these data; this 

establishes a relationship between the Pu-239/240 concentration in soil and in air. Table 4-5 of 

the TBD then presents the average deposition density of each radionuclide in each of the 21 areas 

expressed in units of Bq/m2. 

At this point, it is instructive to develop a better understanding of how the values in Table 4-4 of 

the TBD were derived under the RIDP. The methods section of McArthur (1991) explains that 

the program extended from 1974 through 1984 and began with a series of aerial surveys 

performed by EG&G using rotary wing aircraft mounted with NaI(Tl) detectors in order to 

identify locations with elevated gamma-emitting activities. This helped to target the more 

contaminated areas of the site, at least for gamma emitters. The major data-collection activities 

were made with the use of an HPGe detector mounted on a tracked vehicle. Spectra were 

accumulated for later analysis by the technique generally referred to as in situ gamma 

spectrometry. Analysis of the in-situ data required that the relaxation depth of radionuclides in 

soil be determined. For this purpose, soil samples were collected at incremental depths down to 

15 cm, but some (such as those collected at the Sedan test site) extended down to 30 cm.13 

Sampling locations were based on a 400- or 500-foot grid for the regions of higher activity. The 

samples were screened through a 10-mesh (1.7 mm) screen to obtain only fine grained samples. 

The samples were then analyzed by gamma spectrometry and, with the assumption that the 

radionuclide activity in soil decreases exponentially with depth in soil, the inventory was 

estimated by using the relaxation lengths of each gamma emitter in soil. The top few cm of a 

few soil samples were collected and analyzed radiochemically for Sr-90, Pu-238, Pu-239/240, 

and Am-241. Ratios were then calculated for the different radionuclides that could not be 

measured directly by gamma spectroscopy, e.g., the ratio of Sr-90 to Cs-137. The concentrations 

were then decay corrected to be expressed as the concentrations and inventories as of January 1, 

 

11 Additional radionuclides were detected in some of the areas. 

12 The size of Area 30 is mistakenly given in Table 4-4 as 0.03 square miles; the correct value is 0.3 square 

miles. The correct value was used by NIOSH in subsequent calculations. 

13 The Sedan event created a very large crater with massive amounts of throw-out deposited on top of 

native soil. Deeper depths of soil samples were required in order to analyze the distribution with depth of 

radionuclides due to this unusual situation. 
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1990.

14 Radionuclide isopleths were then constructed, so that a complete picture of the 

radionuclide contamination pattern over the contaminated areas of the site can be displayed in 

terms of nCi/m2and also μR/hr (with a lower level of 100 μR/hr). The RIDP reports provide 

information on the number of soil samples collected in each grid, and more detailed information 

is available in each of the separate reports published by McArthur as the senior author. Because 

of the importance of the RIDP, SC&A performed a spot-check analysis of the data. The results 

are provided in Appendix B. As may be noted, we were able to confirm many of the values 

reported in the TBD. However, not all information is provided in the supporting documents to 

allow a complete independent review of the values provided in the TBD. 

In principle, one could assign a plausible upper bound of the intake of Pu-239/240 for a given 

year (as described above) and estimate the intake of the eight other radionuclides by the ratio of 

Pu-239/240 to the other radionuclides present in the soil. Of course, some judgment will need to 

be made regarding which of the 21 areas should be used to assign ratios. Under worst-case 

conditions, the area that gives the highest intakes of other radionuclides would tend to place an 

upper bound on the chronic baseline intake of the other radionuclides for a given year. Such an 

approach would help to overcome many of the challenges associated with reconstructing doses, 

such as those identified and discussed above. 

The TBD acknowledges that the portion of the NTS where the RIDP data are provided is limited 

to only about one-third of the entire area of the NTS. However, the areas selected for the RIDP 

were those with measurable levels of contamination in soil above ubiquitous background. 

Hence, it certainly appears that a combination of the air-sampling data and the RIDP soilinventory data can be used to assign chronic intakes of these nine radionuclides to workers. In 

addition, if high-end air-sampling and soil-inventory data are used, reconstructed doses 

associated with the chronic inhalation of these nine radionuclides would seem to be reasonably 

bounding. As presented in Table 4-6 of the TBD, this is, in fact, the approach adopted in the 

TBD to reconstruct radionuclide intake rates. 

Because these are very large areas, one could argue that the activity in soil in a given area 

represents the average over a very large area, and some workers may have been at locations with 

radionuclide concentrations that are relatively higher than the average. This may be true for 

some workers, but keep in mind that we are interested in annual intakes, and there should be an 

averaging process if workers did not remain in one location for the entire year. In addition, not 

knowing the location of the workers, there is little recourse but to use high-end air-sampling and 

soil-inventory data collected from the entire site in order to provide a level of assurance that 

worker exposures are not underestimated, at least for “environmental exposures.” 

3.3 EARLIER TIME PERIODS 

Because the air-sampling data for Pu-239/240 extend from 1971 to 2001, and the RIDP soil data 

represent the activity in soil in the 1980s, intakes extending back to earlier years for these 

radionuclides can be estimated by decay correction. For example, Table 4-5 in the TBD presents 

 

14 The January 1, 1990, RIDP data were subsequently decay corrected to January 1, 1963, by NIOSH and 

displayed in Table 4-5 of the TBD. 
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the average soil contamination levels (Bq/m2) of the nine radionuclides in 21 areas for 1963 (i.e., 

the first year after the termination of aboveground testing)15 by simply adjusting for radioactive 

decay from the values reported under the RIDP. Table 4-6 of the TBD presents the 

concentration of eight radionuclides in soil scaled to the level of Pu-239/240 for 1963. 

However, NIOSH acknowledges that extrapolation back to January 1, 1963, must involve more 

than just radioactive decay. At this point, a critical implicit assumption is made that the 

resuspension factor in the 1970s and 1980s is equal to 10-9/m. Then, in order to account for 

increased resuspension during the earlier years of 1963–1965, use is made of the Anspaugh et al. 

(2002) resuspension equation,16 which is given as eq. (4-2) in the TBD:

 

5 0.0 7 9 0.003 9 1 1

10 e 6 10 e 10 10 m

      

    

t t

S f

The following figure, excerpted directly from Figure 4-2 of the TBD, shows how the 

resuspension factor changes as a function of time following initial deposition of radionuclides. It 

is important to note that, at the end of the equation, there is an uncertainty factor of 10 higher and 

10 lower than the curve depicted in Figure 1. Therefore, the curve is actually a thick “ribbon” 

with error bars extending a factor of 10 above and below the curve. In light of this, consideration 

should be given to multiplying the resuspension factors by a factor of 10 in order to ensure 

claimant favorability. In addition, note that, in the first 100 days following initial deposition, the 

resuspension factor declines by several orders of magnitude, and from then on declines very 

slowly, revealing the importance of the 6-month period beginning in July 1962 and ending on

January 1, 1963, the time period that was not addressed in the TBD. These two characteristics of 

the Anspaugh resuspension model need to be taken into consideration for the time periods where 

the Anspaugh equation is used in the TBD. 

In order to make the correction for increased resuspension at early times, NIOSH calculates a 

ratio of the integral of the Anspaugh equation over the time period of 180 to 545 days to the 

integral of 10-9/m. The result of this calculation is 3.12, which is the correction for increased 

resuspension during calendar year 1963. Similar values for 1964 and 1965 are 1.72 and 1.24, 

respectively. As we have previously noted, SC&A does not understand why this back 

extrapolation is carried out only to January 1, 1963. Extrapolation should extend back to July 

1962.17 If the Anspaugh equation is integrated from 0 to 180 days, the computed ratio is 799, 

which indicates the importance of resuspension at early times. 

 

15 Again, there should be no reason not to correct the data back to July 1962. 

16 A slightly modified model with better characterized uncertainty was published by Maxwell and 

Anspaugh in 2011. 

17 According to DOE (2000), 30 underground tests were carried out between the last atmospheric test in 

July 1962 and the end of 1962, so it is clear that substantial activity was ongoing at the NTS. An additional 29 tests 

were conducted at the NTS in the first 6 months of 1963; work in preparation for the latter tests was likely going on 

during the last 6 months of 1962. 
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Worker Health for factual accuracy or applicability within the requirements of 42 CFR 82.

 Source: TBD, Figure 4-2 

Figure 2. Resuspension Factor as a Function of Time after Deposition 

It is important to reiterate that the TBD makes use of the highest measured air concentration of 

Pu-239/240 of 4.3 × 10-3 pCi/m3from Area 9 in 1972; this is a very claimant-favorable 

assumption, because it is assumed that this highest concentration is typical of the airborne 

concentration of Pu-239/240 from 1966 through 1992. NIOSH then calculated the highest 

inhalation intake of Pu-239/240 by multiplying that value by an inhalation rate of 2,400 m3

/year 

and converting from pCi to Bq and derived an intake value of 0.381 Bq/year. The intake values 

for the other eight radionuclides reported by the RIDP were calculated as ratios to the 

Pu-239/240 values. Again, the claimant-favorable assumption was made that the maximum 

values of the additional eight radionuclides were used. Hence, the last row in Table 4-6 of the 

TBD presents the inhalation-intake rate of the nine radionuclides for January 1, 1966.18

 SC&A 

agrees that, in theory, these values represent the highest inhalation-intake rates for 1966 and 

beyond, as derived from the air-sampling data and soil-inventory data representative of the 

1980s. We believe that this strategy helps to account for the possibility that doses might have 

been underestimated because of natural attenuation and cleanup of some areas prior to the 

measurements made under the RIDP in the 1980s. 

It is noteworthy that the methodology adopted in the TBD for deriving the scaling factors in 

Table 4-6 of the TBD is the use of the maximum values in Table 4-6 for deposition density, 

which are from Area 20 for four (Am-241, Pu-238, Co-60, and Eu-155) of the eight 

radionuclides. Area 20 did not have a single nuclear test prior to April 1965, and the major 

Plowshare experiments in Area 20 were Palanquin (April 14, 1965), Cabriolet (January 26, 

 

18 The correction factors for short-term resuspension rates in 1963–1965 must also be applied. 
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1968), and Schooner (December 8, 1968). These three shots produced large amounts of 

contaminated soil in Area 20, with smaller amounts elsewhere on the NTS. And some areas, 

particularly Area 25, were cleaned up before the RIDP measurements were made. 

It is clear that the simplifying assumption made in the TBD, i.e., that all of the radionuclide 

inventories were laid down in July 1962, might result in an underestimate (post-1965 to 1968) or 

overestimate (pre-1965 to 1968) of the intakes as a function of time after January 1, 1963, and 

there is still the unresolved issue of neglecting the last 6 months of 1962. Additional discussion 

with respect to these matters would be helpful. 

3.4 RADIONUCLIDES THAT HAD DECAYED BEFORE THE RIDP DATA WERE 

COLLECTED 

Given that data from the air-sampling program are relatively representative of the long-term 

chronic environmental Pu-239/240 concentrations experienced by some workers, it seems that a 

plausible upper bound can be assigned for the chronic baseline environmental intake of the 

radionuclides measured by the air-sampling and soil-inventory programs. However, we know 

that during atmospheric testing, which ended in July 1962, a very large number of radionuclides 

were released to the atmosphere and deposited in the surrounding soil. Most of these 

radionuclides were relatively short-lived and would not have been detected by the RIDP 

performed in the 1980s. In theory, one could stop at this point and not try to address this issue. 

However, to its credit, NIOSH took advantage of the Hicks’ tables to try to include relatively 

short-lived radionuclides (e.g., Ce-144 and Ru-106) in the dose reconstruction associated with 

chronic environmental exposures (not operational exposures) for the time periods following 

aboveground testing. Section 4.2.1.2.6 of the TBD addresses this issue; most of the important 

material is contained in Appendix A of the TBD. 

For the purpose of reconstructing doses to downwind residents from the NTS (Church et al. 

1990), a Hicks’ table was developed for each test, which presents the ground concentration of a 

large number of radionuclides (Bq/m2) as a function of time after detonation normalized to 

1 mR/hr at 12 hours post-detonation (commonly noted as H+12). Data for a total of 152 fission 

products and 25 activation products are included in the Hicks’ tables. These values were based 

on fundamental principles governing the production of fission and activation products associated 

with a given detonation, along with validation of the predicted values by collecting and 

analyzing debris samples after each shot. The tables were originally developed to allow 

researchers, who had historical measurements of external gamma-exposure rates at downwind 

locations after a test, to estimate the soil-surface contamination levels of a large number of 

fission and activation products on soil as a function of time after a test. Given the exposure-rate 

information and the Hicks’ tables, it was possible to infer the ground deposition of all fission and 

activation products. In effect, these tables provide the relative concentration or inventory of a 

broad range of fission and activation products on soil at any time and location following a test, if 

you have either a measurement of the mR/hr, or if you have an estimate of the concentration of a 

given radionuclide in soil at a given location and time after a test based on other measurements, 

such as those performed under the RIDP. The TBD takes advantage of the RIDP data by using 
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Sr-9019 concentrations measured in the 1980s to back-calculate the concentrations of Sr-90 in 

soil in earlier years. With the use of ratios of other radionuclides-to-Sr-90, estimates could be 

made of the concentration of 177 fission and activation products in soil in the earlier years, 

before many of them decayed away. Because the starting point for calculating the Sr-90 

concentrations in the earlier years was to use the high-end concentration of Sr-90 as measured by 

the RIDP in the 1980s, this strategy appears to be scientifically reasonable and claimant 

favorable. 

There are a number of complicating factors that must be taken into consideration when using the 

Hicks’ tables at the NTS for predicting radionuclide concentrations in soil shortly after a given 

test. The first complication is that about 100 aboveground tests were performed, and the fallout 

on the ground from each test at any given location represents a layering of the fallout from many 

tests. NIOSH elected to use the fallout pattern and associated Hicks’ table for one of the last 

atmospheric tests at the NTS (Small Boy), which took place in July 1962. An issue that requires 

additional discussion is whether other, earlier tests could have contributed to the doses shortly 

after the end of aboveground testing in July 1962.

Section A.6 of the TBD takes the analysis a step further by taking into consideration a 

phenomenon referred to as fractionation. As stated in Section A.6 of the TBD, “Fractionation is 

a phenomenon due to chemical and physical separation of the radionuclides in the fireball in the 

first few minutes after detonation.” This means that refractory elements, such as beryllium, 

sodium, manganese, iron, copper, yttrium, zirconium, niobium, rare earths, thorium, uranium, 

neptunium, and americium, condense and fall out more quickly than other less refractory 

elements, and this process is affected by the mass of material in the vicinity of the detonation. A 

degree of judgment is required when determining how fractionation is taken into consideration 

for a given test and the objectives of the test. The Hicks’ tables that were used by NIOSH to 

support the reconstruction of environmental exposures onsite were actually originally derived for 

the purpose of evaluating offsite exposures. As a result, the Hicks’ tables understate the relative 

abundance of refractory elements onsite and overstate the presence of volatile elements. While it 

is desirable to address this issue, we do not believe that it should prevent NIOSH from 

proceeding with the use of the Hicks’ tables. 

3.5 CALCULATIONS OF DOSE FROM INHALATION 

Working with the soil concentration values derived for January 1963 and associated inhalation 

rates, along with the resuspension factor adjustment factors for deriving inhalation rates after 

July 1, 1963, the authors of the TBD undertook a very complex and not explicitly documented 

series of calculations, wherein they took the International Commission on Radiological 

Protection (ICRP 2011) dose coefficients for the 177 radionuclides for each of the ICRP listed 

organs and went through a calculation of dose as a function of time. The starting point in time is 

a critical, but poorly defined, factor. If NIOSH was true to the material existing up to this part of 

their document, they would have started at January 1, 1963; but their multiple figures (A-2 

through A-11) have abscissa labeled “Days after Detonation,” and the starting point is shown as 

 

19 The Hicks’ tables do not include values for Pu-239/240, so it is not possible to continue normalization to 

values of Pu-239/240 in the process used by NIOSH. 
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0. The series of curves provided in the figures express the fraction of total dose contributed by 

Sr-90 for each organ as a function of time. The graphical results show some curvature, but 

NIOSH fit a straight line to such curves. One such fit for debris from the Small Boy event is 

given for the lungs as: 

y  0.0001 x  0.0074 ,

where y is the fraction of total dose contributed by 90Sr and x is time. This is equation A-2 as 

given in the TBD. One unexplained fact here is that this equation does not match the equation 

shown in Figure A-2, which should have been the same as equation A-2. The authors then state 

the following: 

Integrating Equation A-2 for SMALL BOY from 0 to 365 days and dividing the 

results by 365 (the value that represents the integrated total dose for 1 year), it 

was determined that for the first year after detonation the lung dose from 90Sr 

represented 0.0000738 or about 0.00738% of the dose from all 177 radionuclides. 

There are two problems with this. The first is the implication that time zero is the time of the last 

detonation (i.e., July 1962), but this appears to be impossible, given that the authors show in their 

Table A-9 that the relative dose to the thyroid is the same as for 17 other organs. Due to the 

affinity of the thyroid for short-lived radioiodines, this cannot be correct. 

The second problem is the integration. A reproduction of what the authors said they did is the 

following: 

0.026

365

0.0074

2

0.0001

365

(0.0001 0.0074)d

365

0

365 2

0







 

x

x

x x

The calculated value of 0.026 is obviously very different from 0.0000738. The above equation 

is, in fact, the classic definition of an average of the function over the 365-day period, and 

according to the authors’ Figure A-2, the average value has to be about midway between 0.00 

and 0.05. The authors’ contention that they have calculated an integrated total dose does not 

match the reproduction of what they said they did. Because of our uncertainty in how the doses 

were actually calculated, it is not possible to continue with our review of the methods used in the 

TBD. It is a matter of some urgency that NIOSH explains or corrects their calculations on how 

they got from Table 4-7 to Table 4-8.

There is, however, one more issue of concern. We understand that it is necessary to feed 

information in the form of annual dose into IREP. This is easy enough, if the dose from a 

radionuclide is delivered completely within 1 year. However, some radionuclides are long-lived 

in terms of both physical and biological half-lives and, following intake, deliver dose over more 

than 1 year. An example of the importance of this is shown in Figure 3 for the intake of Pu-239 

and subsequent dose over time to the extra-thoracic lymph nodes. For this “organ” and a few 

others, it is very important to consider the dose to the organ beyond just the first year. 
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10- 6

10- 5

0.0001

1 3 5 7 9 Accrued dose coefficient, Sv/Bq

Time after intake, years

Figure 3. Accrued Dose (Coefficient) for Extra-Thoracic Lymph Nodes (LNet) as a 

Function of Time Following Intake of Pu-239 

Note that only a small fraction of the total dose has been accrued during the first year. The curve 

represents a 9-degree polynomial fit to the ICRP (2011) dose coefficients. The red dots are the 

actual dose coefficients for 1, 5, and 10 years following intake. 

NIOSH should clarify whether they have considered annual doses in subsequent years from the 

intake of radionuclides in preceding years. 

4.0 DOSE FROM INGESTION OF SOIL 

The method of calculating dose from ingestion is very similar to the method of calculating dose 

from inhalation. Although consideration of dose from ingestion is beyond the scope of Issue 5, 

we do note that the same problems exist as noted above for the inhalation pathway. 

5.0 THE MASS LOADING APPROACH FOR INHALATION 

One of the original issues raised by SC&A during the review of the NTS site profile (i.e., 

Issue 5) was whether the mass-loading approach was a more appropriate strategy for 

reconstructing inhalation doses from the resuspension process at the NTS, as opposed to the use 

of the resuspension-factor approach. In order to explore this question, this section reconstructs 
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the inhalation-intake rates using the mass-loading approach and compares those values to the 

values derived in the TBD.

A simple method that can be used to compare the results of the airborne Pu-239/240 approach for 

determining inhalation-intake rates (as provided in Table 4-7 of the TBD) and those obtained 

using the mass-loading approach is to take advantage of the radionuclide-concentration values 

provided in Table 4-10 of the TBD. Table 4-10 presents the concentration of the radionuclides at 

the surface of the soil.20

Consistent with the approach used by NIOSH, we have chosen the highest values for each 

radionuclide shown in Table 4-10 with the exclusion of Area 30, which was heavily 

contaminated in 1968, but which is isolated. The highest values by area are for Area 2021 for 

Am-241, Pu-238, Co-60, Eu-154, and Eu-155; Area 10 for Cs-137 and Sr-90; Area 8 for 

Pu-239/240; and Area 5 for Eu-152. As with the NIOSH stated goal of dose calculations, we 

chose the radionuclide type that would give the highest accrued dose for 1 year. For some 

organs, we also include the accrued dose for 5 years, in order to indicate the problem noted 

above in Figure 3. We took dose coefficients directly from the ICRP (2011). Calculations of 

dose, D (Sv), are made according to: 

D  C DC MLIRK ,

where C is the concentration in soil (Bq/g), DC is the dose coefficient (Sv/Bq), ML is the mass 

loading (mg/m3), IR is the breathing rate fixed at 2,400 m3

/year, and K is a constant equal to 

0.001 g/mg. 

The results of the calculations are shown in Table 1 for ML = 1 mg/m3. From a practical 

perspective, only the ET, ET1, and LN(et) doses are of interest, because they are not covered by 

the SEC. However, doses to other organs are provided simply to demonstrate that the inhalation 

doses are, in fact, not unreasonably high using the mass-loading approach (even at a chronic dust 

loading of 1 mg/m3), as stated by NIOSH (see above discussion regarding this issue). The 

highest 1 year dose from a 1-year intake is 4.37 × 10-4 Sv (0.0437 rem) to the bone surface, and 

the highest dose over 5 years from a 1-year intake is 2.49 × 10-3 Sv (0.249 rem). There are also 

relatively high doses to the lungs, ET1 and ET. Contrary to the undocumented findings of 

NIOSH discussed above, these dose values do not seem to be “extraordinarily high.” A major 

point of interest is that almost the entire dose is due to the three actinide radionuclides. 

Comparable values of dose are not presented in the TBD, but we can make a comparison for the 

nine radionuclides shown in our Table 1 by simply multiplying the scaled inhalation intakes 

(Bq/yr) given in TBD Table 4-7 by the same dose coefficients shown in our Table 1. Our 

 

20 SC&A originally believed that radionuclide concentrations reported in Table A-10 of the TBD were the 

average concentrations in the top 15 cm of soil. Discussions with Dr. Anspaugh, who was intimately involved in the 

research performed at the NTS at this time, explained that these concentrations were derived by plotting the 

concentrations of individual radionuclides as a function of depth, and extrapolating back to the concentrations at 

zero depth. 

21 We have previously noted that Area 20 was not appreciably contaminated until 1965, but in this instance, 

for the sole purpose of exploring this dose reconstruction issue, we continue to use the process adopted by NIOSH. 
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Table 2 shows the results of this calculation resulting from 1 year of intake according to the 

scaled inhalation intakes for 1963. The results are smaller with the highest 1-year dose of 

7.34 × 10-5 Sv being to the bone surface; again doses are dominated by the three actinide 

nuclides. 

The calculations shown in our Table 2 were made with an arbitrary mass loading of 1 mg/m3. 

The implications of these calculations are that (1) mass loading is a reasonable approach, (2) a 

mass loading of 0.168 mg/m3gives the same dose as the resuspension method, and (3) 1 mg/m3

is reasonable and would be more claimant favorable. It is SC&A’s opinion that the mass-loading 

approach deserves reconsideration, especially for possible use in considering the occupational 

environmental dose that would have been received by employees working in dusty conditions. 

In such situations, a mass loading of 1 mg/m3 would be reasonable. 

Table 1. Calculations of Dose with Use of the Mass-Loading Approach (1 mg/m3

) 

Radionuclide soil data are from Table 4-10 of the TBD (1963 values). Dose coefficients are from the ICRP (2011).
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Table 2. Calculations of Dose from the Nine Radionuclides also considered in Table 2 

These calculations are performed using the methodology given in NIOSH’s TBD.
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6.0 APPLICATIONS OF THE TBD PROCEDURE IN ACTUAL DOSE 

RECONSTRUCTION FOR CLAIMANTS 

In order to understand the degree to which the methods described in the TBD were actually 

performed, SC&A examined the claim files of energy employees (EEs) who were onsite after 

1962 and had a probability of causation (POC) less than 50%. These criteria were chosen to 

target the NTS claimants who were likely to have environmental doses assigned per the TBD. 

Additionally, only cases that have been evaluated after ORAUT 2012 was approved were 

considered. A total of 241 claimants were identified and their dose reconstruction 

documentation examined. An overall summary of these claims is found in Table 3. 

Table 3. Characterization of the Application of Environmental Doses to 

Relevant NTS Claimants 

Category Total # Percent of Total

Total Relevant Claims 241 -

Full Internal and External DR 127 52.7%

Overestimate DR 114 47.3%

Full TBD Intakes (Full Years, Entire Employment) 183 75.9%

Full TBD Intakes (Full Years, Partial Employment) 7 2.9%

10% TBD Intakes (Full Years, Entire Employment) 4 1.7%

OTIB-0018 Intakes (Entire Employment) 14 5.8%

OTIB-0018 Intakes (Partial Employment) 9 3.7%

Tonopah Test Range Intakes Assigned 5 2.1%

No Environmental Intakes Assigned 19 7.9%

As seen in Table 3, the “Full Internal and External” (i.e., best-estimate) and “Overestimate” dose 

reconstructions were fairly evenly split. For over three-quarters of the affected claimants, the 

maximum intake rates prescribed in the TBD (NIOSH 2012, Tables 4-7 and 4-11) were applied 

for each year of employment and assumed to apply to the entire year. It should be noted that the 

TBD prescribes the following concerning the application of environmental intakes: 

If necessary, these intakes can be prorated for time less than a year for a best 

estimate if the worker was on site for only a fraction of the year. (ORAUT 2012, 

pg. 27)

SC&A did not identify any cases in which prorated intake rates were actually applied, and only 

one case in which prorated intakes appear to have been evaluated, but ultimately discarded for 

full year intakes. 

Of the remaining cases that were not assigned full-year intakes for each year of employment, a 

variety of methods were observed. For example, 7 cases applied full-year TBD intakes, but not 

for every year of employment (see Observations 2a and 9a in Table 6). Four cases were 

observed in which only 10% of the annual TBD intakes were applied (see Observation 4). 

Twenty-three total cases applied ORAUT-OTIB-0018 (ORAUT 2005) methods for 
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reconstructing environmental internal dose (see Observations 1a, 1b, 3, and 8). Five cases 

applied intake rates associated with Tonopah Test Range (see Observation 7). Finally, 19 cases 

did not have environmental intakes assigned (see Observations 2a, 2b, 5, 9a, and 9b). 

The maximum environmental intakes from the TBD can be found in Tables 4-6 and 4-11 of 

ORAUT 2012. ORAUT-OTIB-0018 intake rates are found in Table 4-1 that document. The 

intakes associated with Tonopah Test Range are found in Table 4-8 of ORAUT-TKBS-0037 

(ORAUT 2013). Each of these intake rates are recreated in Table 4 for reference. 

Table 4. Environmental Intake Rates Observed in Relevant NTS Dose Reconstructions 

Radionuclide

TBD 

Inhalation 

Intake*

(Bq/yr)

TBD 

Ingestion 

Intake 

(Bq/yr)

OTIB-0018 

Inhalation

(Bq/yr)

OTIB-0018 

Ingestion 

(Bq/yr)

Tonopah 

Inhalation†

(Bq/yr)

Tonopah 

Ingestion

(Bq/yr)

Am-241 2.33 × 10-14.02 × 101– – 4 × 10-4–

Pu-238 3.47 × 10-16.25 × 101– – 2 × 10-4–

Pu-239/240 3.81 × 10-18.20 × 101– – 8 × 10-5–

Co-60 2.91 × 1005.24 × 102– – – –

Cs-137 7.92 × 10-18.30 × 101– – – –

Sr-90 1.55 × 1005.54 × 101– – – –

Eu-152 3.40 × 1001.53 × 102– – – –

Eu-154 1.44 × 10-12.42 × 101– – – –

Eu-155 2.23 × 1004.01 × 102– – – –

Alpha** – – 1.78 × 1023.74 × 101– –

Beta3– – 1.78 × 1053.74 × 103– –

* Note the inhalation intakes are slightly different for 1963–1965 due to scaling associated with early 

resuspension. 

† It was observed in some cases that inhalation intakes were assigned based on Revision 00 of the TBD; 

based on the dose reconstruction calculation files, these intakes were slightly higher at 0.0005, 0.0002, 

and 0.0001 Bq/yr (Am-241, Pu-238, and Pu-239/240, respectively). 

** Assumed to be radionuclide, which results in the highest organ-specific dose by year. 

 

SC&A also had the following nine observations concerning the environmental intake assignment 

as shown in Table 5. 
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Table 5. Observations Concerning Ambient Environmental Dose Assignment 

to NTS Claimants 

Observation 

#

Description of Observation Example Case 

#'s

1a

OTIB-0018 was utilized instead of environmental intakes when the NTS 

employment period coincided with employment at another site (LLNL, 

LANL, SNL etc.).

7 Case Examples 

Provided

1b OTIB-0018 was applied instead of environmental intakes when 

employment was at NTS and not another site.

11 Case Examples 

Provided

2a

Some employment periods after 1963 were not assigned environmental 

intakes, because there was no dosimeter assigned to the EE for those 

periods.

3 Case Examples 

Provided

2b Lack of a dosimeter during certain employment periods after 1963 was not 

always used to preclude the assignment of environmental intakes.

4 Case Examples 

Provided

3 In some cases, OTIB-0018 was applied, but only for years after 1992. 9 Case Examples 

Provided

4

Four cases assigned only 10% of the environmental intake values. Only 

one of the four cases specifically mentioned this in the DR Report. Two of 

the four cases had POC values that were less than 10%; the other two were 

above 45%.

4 Case Examples 

Provided

5

Many cases did not evaluate ambient internal dose during NTS employment 

and cited the SEC and/or the lack of bioassay in the dose reconstruction 

report.

10 Case Examples 

Provided

6

One case assigned full environmental intakes from 1966–1989, although 

the EE's covered employment was only for a single day in 1971 and 1982.

1 Case Example 

Provided

7

Several cases did not apply NTS environmental intakes and instead applied 

Tonopah Test Range (TTR) intake values, which are significantly lower 

than NTS intake rates (See Table 1). Not all of these observed cases had 

overlapping employment at NTS/TTR.

6 Case Examples 

Provided

8

Both OTIB-0018 and environmental intakes were assigned to the same 

employment period in one case. However, the environmental intakes did 

not include plutonium (inhalation or ingestion) or americium (inhalation 

only).

1 Case Example 

Provided

9a Some cases were not assigned environmental intakes, because the doses 

were deemed too low based on the short duration of covered employment. 

5 Case Examples 

Provided

9b Some cases were assigned full years’ worth of environmental intakes even 

though covered employment was of short duration.

5 Case Examples 

Provided

Based on this review of relatively recently completed dose reconstructions, procedures, and 

instructions for application of environmental doses in the TBD, and used by the dose 

reconstructors, it appears that the dose reconstructions were not always performed in accordance 

with the procedures delineated in the TBD. 

As was noted in Table 5 and Observation 4, four cases were identified that applied intake rates 

that were 10% of the TBD prescribed values. SC&A was able to trace this abnormality to a 
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word document that was sometimes included in NOCTS with the standard dose reconstruction 

documentation titled, “NTS DR Guidance [various dates].” The pertinent section on ambient 

environmental intakes is shown as a screenshot in Figure 4. As can be seen in this figure, for a 

“best-estimate” dose reconstruction, the area-specific inhalation/ingestion intakes can be used. 

In the event that the work location is unknown, 10% of the prescribed intake values can be 

utilized instead. This guidance and approach is not contained in the currently approved TBD. 

As noted earlier, the TBD instructs the dose reconstructor to prorate the maximum intake values 

to the energy employee’s covered employment for “best-estimate” cases.

Figure 4. Screenshot of Word Document Included in Some NOCTS Files Providing 

Guidance on the Application of Environmental Intakes 

SC&A did not observe a case in which an area-specific inhalation intake was utilized. However, 

SC&A did note that area-specific information was available in the four cases utilizing 10% of the 

TBD intakes. This information was generally in the form of the area in which external 

dosimeters were issued. 

Based on these case reviews, there appears to be incongruity between the guidance provided in 

the site profile and the methods used in the actual dose reconstructions. 
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REFERENCES

ABRWH 2007a. Nevada Test Site Work Group meeting transcript, March 27, 2007. Advisory 

Board on Radiation and Worker Health. On the web at 

http://www.cdc.gov/niosh/ocas/pdfs/abrwh/wgtr032707.pdf.

ABRWH 2007b. Nevada Test Site Work Group meeting transcript, August 7, 2007. Advisory 

Board on Radiation and Worker Health. On the web at 

http://www.cdc.gov/niosh/ocas/pdfs/abrwh/wgtr080707.pdf.

ABRWH 2008. Nevada Test Site Work Group meeting transcript, October 29, 2008. Advisory 

Board on Radiation and Worker Health. On the web at 

http://www.cdc.gov/niosh/ocas/pdfs/abrwh/2008/wgtr102808.pdf.

ABRWH 2009a. Nevada Test Site Work Group meeting transcript, April 23, 2009. Advisory 

Board on Radiation and Worker Health. On the web at 

http://www.cdc.gov/niosh/ocas/pdfs/abrwh/2009/wgtr042309.pdf. 

ABRWH 2009b. Nevada Test Site Work Group meeting transcript, December 15, 2009. 

Advisory Board on Radiation and Worker Health. On the web at 

http://www.cdc.gov/niosh/ocas/pdfs/abrwh/2009/wgtr121509.pdf. 

ABRWH 2015. Nevada Test Site Work Group meeting transcript, December 3, 2014. Advisory 

Board on Radiation and Worker Health. On the web at 

http://www.cdc.gov/niosh/ocas/pdfs/abrwh/2014/wgtr120314.pdf.

Anspaugh, L.R., 2006. “The Resuspension Pathway for Nevada Test Site Workers,” Rev. 3. 

SC&A, Inc., Vienna, Virginia. October 8, 2006.

Anspaugh, L.R., 2007. “Preliminary List of Issues for “Ambient environmental intakes at the 

Nevada Test Site based on air sampling and soil contamination data,” dated July 29, 2007.” 

SC&A, Inc., Vienna, Virginia. August 6, 2007.

Anspaugh, L.R., 2008. “Comments on ORAUT-TKBS-0008-4, “Nevada Test Site–Occupational 

Environmental Dose.” SC&A, Inc., Vienna, Virginia. October 21, 2008.

Anspaugh L.R., S.L. Simon, K.I. Gordeev, I.A. Likhtarev, R.M. Maxwell, and S.M. Shinkarev, 

2002. “Movement of radionuclides in terrestrial ecosystems by physical processes.” Health 

Phys 82:669–679; 2002.

Bechtel SAIC 2006. “Inhalation Exposure Input Parameters for the Biosphere Model,” ANLMGR-MD-000001, Rev. 04, Bechtel SAIC Co., Las Vegas, Nevada. June 2006.

Church B.W., D.L. Wheeler, C.M. Campbell, R.V. Nutley, L.R. Anspaugh. 1990. “Overview of 

the Department of Energy’s Off-Site Radiation Exposure Review Project (ORERP).” Health 

Phys 59:503–510; 1990.
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Worker Health for factual accuracy or applicability within the requirements of 42 CFR 82.

DOE 2000. United States nuclear tests, July 1945 through September 1992. DOE/NV -- 209-

Rev. 15: U.S. Department of Energy, Nevada Operations Office, Las Vegas, Nevada. December 

2000.

Hicks, H.G., 1982. “Calculation of the Concentration of Any Radionuclide Deposited on the 

Ground by Offsite Fallout from a Nuclear Detonation.” Health Phys 42:585–600; 1982.

Kordas, J.F. and L.R. Anspaugh, 1982. “Nevada Test Site Radionuclide Inventory and 

Distribution—Project Operations Plan.” Lawrence Livermore National Laboratory, Livermore, 

California. June 1, 1982.

Maxwell, R.M. and L.R. Anspaugh, 2011. “An improved model for prediction of resuspension.” 

Health Phys 101:722–730; 2011.

McArthur, R.D., 1991. “Radionuclides in Surface Soil at the Nevada Test Site.” Report 

DOE/NV/10845-02. Desert Research Institute, University of Nevada System, Las Vegas, 

Nevada, 1991. [SRDB Ref ID: 7872]

McArthur, R.D. and J.F. Kordas, 1983. “Radionuclide Inventory and Distribution Program: 

The Galileo Area.” Report DOE/NV/10162–14. Desert Research Institute, University of 

Nevada System, Las Vegas, Nevada, 1983.

McArthur, R.D. and J.F. Kordas, 1985. “Nevada Test Site Radionuclide Inventory and 

Distribution Program: Report #2, Areas 2 and 4,” Report DOE/NV/10162–20. Desert Research 

Institute, University of Nevada System, Las Vegas, Nevada, 1985.

McArthur R.D. and S.W. Mead, 1987. Nevada Test Site radionuclide inventory and distribution 

program: Report #3, Areas 3, 7, 8, 9, and 10.” Las Vegas, Nevada: Desert Research Institute, 

University of Nevada System; Report DOE/NV/10384–15; 1987.

McArthur R.D. and S.W. Mead, 1988. “Nevada Test Site radionuclide inventory and 

distribution program: Report #4, Areas 18 and 19.” Las Vegas, Nevada: Desert Research 

Institute, University of Nevada System; Report DOE/NV/10384–24; 1988.

McArthur R.D. and S.W. Mead, 1989. “Nevada Test Site radionuclide inventory and 

distribution program: Report #5, Areas 5, 11, 12, 15, 17, 18, 19, 25, 26, and 30.” Las Vegas, 

Nevada: Desert Research Institute, University of Nevada System; Report DOE/NV/10384–26; 

1989.

NIOSH 2007. “NIOSH Responses to S. Cohen & Associates Comment Related to Issues 

Involving Resuspension and Soil Contamination: Comments 5, 6, 7, and 23,” National Institute 

for Occupational Safety and Health, Cincinnati, Ohio. March 23, 2007.

NIOSH 2010. “SEC Petition Evaluation Report for Petition SEC-00084, Nevada Test Site,”

Rev. 1, National Institute for Occupational Safety and Health (NIOSH), Cincinnati, Ohio. 

January 25, 2010.
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Worker Health for factual accuracy or applicability within the requirements of 42 CFR 82.

ORAUT 2005. “Internal Dose Overestimates for Facilities with Air Sampling Programs,”

ORAUT-OTIB-0018, Rev. 01, Oak Ridge Associated Universities Team, Cincinnati, Ohio. 

August 9, 2005.

ORAUT 2008. “Technical Basis Document for the Nevada Test Site: Occupational 

Environmental Dose,” ORAUT-TKBS-0008-2, Vol. 4, Rev. 01, Oak Ridge Associated 

Universities Team, Cincinnati, Ohio. May 27, 2008.

ORAUT 2010. “Technical Basis Document for the Nevada Test Site: Occupational 

Environmental Dose,” ORAUT-TKBS-0008-4, Vol. 4, Rev. 2, Oak Ridge Associated 

Universities Team, Cincinnati, Ohio. April 15, 2010.

ORAUT 2012. “Nevada Test Site – Occupational Environmental Dose,” ORAUT-TKBS-0008-

4, Rev. 3, Oak Ridge Associated Universities Team, Cincinnati, Ohio. August 24, 2012.

ORAUT 2013. “Site Profile for Sandia National Laboratories in Albuquerque, New Mexico, and 

the Tonopah Test Range, Nevada.” ORAUT-TKBS-0037 Rev. 01. Oak Ridge Associated 

Universities Team, Cincinnati, Ohio. January 25, 2013.

Rollins, G. 2007. “Ambient Environmental Intakes at the Nevada Test Site Based on Air 

Sampling and Soil Contamination,” Oak Ridge Associated Universities Team, Cincinnati, Ohio. 

July 29, 2007.

REECo. 1971. “Environmental Radioactivity at the Nevada Test Site. July, 1968 through June, 

1969,” NVO-410-16, Reynolds Electrical & Engineering Co., Inc., Las Vegas, Ohio.

SC&A 2012. “Update of the Nevada Test Site (NTS) Issue Resolution Matrix Based on the 

SC&A Review of the NIOSH Site Profile for the Nevada Test Site,” SCA-SP-IM2012-0042, 

Rev. 1. SC&A, Inc., Vienna, Virginia. December 12, 2012.
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APPENDIX A: LATEST ISSUES RESOLUTION MATRIX DATED 

DECEMBER 14, 2012

On December 14, 2012, the NTS matrix was updated and contained the following exchange 

of information between SC&A and NIOSH:

Review of unaddressed items appears to be warranted. 

NIOSH Response 

The following assumptions (in italics) are excerpts from (Anspaugh 2008). The NIOSH 

replies to the assumptions are in regular bold. 

Assumption 1: No Contamination of the NTS Occurred after July 1962. 

This assumption has already been examined extensively in the section of this document following 

the Introduction. As noted, there were many contaminating events that produced substantial new 

depositions on soil. The contribution of the Buggy event was even acknowledged in Rollins 

(2008a)22 although it was ignored. Events specifically mentioned in the reports of the 

environmental surveillance program were Pike, Nash, Hupmobile, Buggy, Door Mist, Schooner, 

and Baneberry. Events Buggy, Schooner, and Baneberry were even noted to have contaminated 

potable water at the NTS. 

NIOSH Response: 

While it is true that there were many controlled and uncontrolled releases to the 

environment after 1962, the vast majority of these releases were of noble gases and volatile 

iodines which would not have contributed significantly to soil contamination (DOE 1996). 

Of the non-volatiles reported (e.g., W-187, Sr-91, Cs-138, Ru-106, etc.), most had half-lives 

on the order of hours or days and would only be a concern to individuals participating in 

early reentry operations. As shown by Rollins (2007b), exposure to these short-lived fission 

and activation products would be expected to result in minimal doses to the nonpresumptive cancers affecting the larynx (ET2 and LNET), skin, and prostate. 

Also, it should be noted that DOE evacuated non-essential workers from downwind areas 

of the NTS prior to all tests to minimize potential for radiation exposure. In addition, after 

releases, surveys were conducted to characterize the fallout fields and to implement 

controls to prevent inadvertent entry into these areas. 

The only mention of potentially contaminated potable water was in December of 1968 and 

January, 1969 REECo (1971). The maximum concentration was 1.54 × 10-6μCi/cc 

measured on January 19, 1969, at the Area 2 Men’s Restroom. However, these elevated 

levels quickly dissipated and the mean concentration for all samples taken at this location 

for 1969 was 4.60 × 10-9μCi/cc compared with 6.41 × 10-9Ci/cc for 1968; well below the 

 

22 This reference called here is the same as ORAUT (2008), as cited in the main text.
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alert level of 1.0 × 10-7μCi/cc for unidentified radionuclides. Thus, anyone drinking water 

at this location during 1968 and 1969 would be expected to receive inconsequential internal 

dose. 

Assumption 2: The Air Concentrations Recorded by the Air Samplers of the NTS Environmental 

Surveillance Program During 1971 and Beyond Can Be Used to Derive the Air Concentrations 

That Would Have Been Seen at these Same Air-Sampler Locations During 1963–1970. 

As demonstrated above by the detailed consideration of the contaminating events at NTS during 

1963–1970 and the results of the environmental surveillance air-sampling program, there were 

several substantial excursions noted in the air concentrations due to massive releases at the 

NTS. The last such release occurred in December 1970. Thus, it is impossible for air-sampling 

results during the 1971–2001 period to reproduce these massive excursions that occurred in 

1963–1970. 

NIOSH Response 

The purpose of the calculations performed by Rollins (2007b) was not to try to predict air 

sampler measurements between 1963 and 1970 but was to provide a claimant-favorable 

method of assigning environmental intakes to individuals not associated with operations. 

This was done by selecting the highest integrated air concentration measured for Pu-239, as 

part of the environmental surveillance program, anywhere on site between 1971 and 2001 

and correlating it with other radionuclides (decay corrected) persisting in the NTS soils 

across the site to estimate their relative intakes. NIOSH believes the “massive excursions” 

that occurred as a result of controlled and uncontrolled releases are relatively unimportant 

to organ dose because of their brief duration and because nonessential personnel were not 

exposed to them due to the required, pre-test, downwind evacuations. 

Assumption 3: More Generally, the Air Concentrations Actually Experienced by the Workers at 

the NTS. 

This is a more difficult issue, as there do not appear to be any objective data on the inhalation of 

radionuclides at the NTS as measured with a personal air sampler and in comparison to any of 

the locations of the environmental surveillance network. It is known, however, that these airsampling stations were typically located next to cafeterias and dispensaries, where there would 

be relatively little dust. On the other hand, there were many types of work that would have raised 

large amounts of dust. One outstanding example of a major dust raising event was the movement 

of drilling rigs, such as the one shown in Fig. 18, from one location to another without 

disassembly. The drill rig was raised with hydraulic jacks, and large steel beams were placed 

through the rig. Then four “coasters,” one of which is shown in Fig. 19, were attached to the 

beams. The two beams and one of the coasters are shown in Fig. 20. The presumed path of one 

such movement is shown in Fig. 21. 

There has been substantial concern about mass loading and exposure to persons, if there might 

be a volcanic eruption that would influence the Yucca Mountain waste-storage site. As part of 

the evaluation process, there has been a substantial effort to evaluate possibly enhanced mass 
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loading due to outdoor activities in a post eruption environment. The evaluation has consisted of 

reviewing relevant literature and in conducting measurements of mass loadings in Amargosa 

Valley, Nevada. These studies are described in Bechtel SAIC (2006). 

The authors of Bechtel SAIC (2006) considered mass loadings in several environments; two of 

interest to us are the “Inactive Outdoor Environment,” which would be similar to the locations 

where the NTS environmental surveillance air samplers were located. Their review of data and 

of measurements made as part of the Yucca Mountain evaluation program resulted in their 

description of mass loading in this environment with a triangular distribution with a mode of 

0.060 mg m-3, a minimum of 0.025 mg m-3, and a maximum of 0.100 mg m-3.

The “Active Outdoor Environment” was also considered, and would include activities such as 

driving bulldozers, tractors, heavy construction machinery, etc. Their evaluation of literature 

values and of their contracted measurements in Amargosa Valley was again a description by a 

triangular distribution, but now with a mode of 3 mg m-3, a minimum of 1 mg m-3, and a 

maximum of 10 mg m-3.

Thus, according to the evaluation of the Yucca Mountain evaluation group, the mass loading 

experienced by a bulldozer driver would be on the order of 3 divided by 0.06, or 50 times higher 

than the concentration of dust in an inactive outdoor environment. Of course, a person driving a 

bulldozer would not be exposed to such levels 100% of the time, but it is obvious that a 

stationary air sampler located next to a cafeteria or dispensary would not give a realistic 

indication of a working person’s exposure. 

It is also well to remember the words of some of the early investigators of the NTS environmental 

surveillance program: 

Results of environmental surveillance in sampling activity values cannot be used 

in calculating personnel exposure doses.

As a final point, it has often been assumed by NIOSH personnel that “Controlled Areas” at the 

NTS are fenced and that it not possible to enter such areas. This is hardly the case, as many 

Controlled Areas are “controlled” by nothing more than a warning sign. Fig. 22 is a photo of 

one such Controlled Area, which actually has a road right through it. 

NIOSH Response 

As stated above, the purpose of the calculations performed by Rollins (2007b) was not to 

try to predict intakes associated with operational activities but was to provide a claimant 

favorable method of assigning environmental intakes to individuals not associated with 

operations. Therefore, it would be reasonable to position the samplers (cafeterias and 

dispensaries) where they would be unlikely to be exposed to dust clouds associated with 

operational activities (e.g., moving drilling rigs). 
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Assumption 4: There Were No Clean-Ups of Radioactive Materials Between 1962 and the Time 

Period When Measurements of Surface Radionuclides Were Made by the Radionuclide Inventory 

and Distribution Program (RIDP) in the 1980s. 

The measurements of surface-soil contamination performed by investigators of the RIDP are 

critical to the methodology developed in Rollins (2008a) for the reconstruction of internal doses 

via both inhalation and incidental ingestion of soil. The RIDP measurements were not made for 

the purpose of reconstructing doses, but rather for defining the amounts and locations of existing 

contamination for the purposes of control and future clean-up (Kordas and Anspaugh 1982). 

Between 1962 and the time of the measurements made by the investigators of the RIDP, there 

was an active program on cleaning up contaminated soil.

McArthur and Mead (1989) specifically mention that much of the Nuclear Rocket Development 

Station in Area 25 had been cleaned up before the RIDP measurements were started in February 

1984. Thus, the fourth assumption must be considered as invalid, as well. The surface soil 

activities measured in the 1980s cannot be depended upon to represent activity present in 1963–

1970, decay corrected or not.

NIOSH Response

McArther (1991) identified a total of 510 square miles of contaminated soils (about a third 

of the total NTS area) containing more than 2,000 curies of radioactivity. This radioactivity 

was related to radionuclides that are persistent in the environment and are important to 

organ dose. Although there were efforts to decontaminate some of the more highly 

contaminated areas, these efforts focused on contaminated equipment and large, 

nonrespirable particles. The efforts made to decontaminate Nuclear Rocket Development 

Station in Area 25 would likely have had little effect on the air concentrations measured in 

Area 7 that were used to estimate environmental intakes.
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APPENDIX B: PARTIAL EVALUATION OF THE MCARTHUR DATA 

AND THEIR USE IN THE TBD

All of the data presented in McArthur 1991 is gathered from five reports written for the 

Radionuclide Inventory and Distribution Program (RIDP). Each of the five reports covered a 

handful of ‘areas’ of the Nevada Test Site (NTS). Three measurement techniques were used to 

assess the extent of soil contamination at NTS: aerial surveys, in situ spectrometry, and soil 

samples. The aerial measurements were conducted first in order to find areas with elevated levels 

of radiation so that they could be surveyed via in situ spectrometry. The in-situ spectrometry 

measurements were conducted with a collimated HPGe detector mounted on a vehicle, and 

measurements were taken in a regular, grid-like pattern for some parts of each area. Soil samples 

were collected at a few locations where an in-situ measurement was also taken. The soil samples 

were taken along transecting lines that aligned with the ground zero of an associated test 

location. Samples were analyzed primarily to understand how concentrations of the radionuclides 

differed as a function of depth in soil to calculate the inverse relaxation length. A handful of 

samples were analyzed for 90Sr, 238Pu, 239,240Pu, 137Cs, and 241Am. Various ratios of these 

nuclides were calculated so that inventories of 90Sr, 238Pu, and 239,240Pu could be estimated from 

137Cs and 241Am inventories.

We found that when calculating the radionuclide inventories for the areas, the in-situ 

measurements appeared to be used rather than the soil samples. Page 34 of McArthur 1991 talks 

about the decay correction done for the inventory calculations and states that,“The survey date 

used for each area was the approximate date of the highest in situ measurements.” Also, in 

McArthur and Kordas 1983 (the first of the five RIDP reports) the methods section states, 

“Therefore, we believe that the activities in the Galileo ground zero area derived from the in-situ 

data are a much better estimate of the true activity than those derived from soil sampling.” This 

document also states that the methods described in it are to be used for the future RIDP reports.

Example Area/Nuclide to Check Numbers

Pages 31 through 34 of Appendix A in McArthur 1991 indicate where in the RIDP reports the 

inventory values were taken from. We chose to first look at 137Cs in Area 10, since it had the 

highest inventory for 137Cs. McArthur 1991 Appendix A indicates that the data for this area were 

taken from the third RIDP report (McArthur and Mead, 1987). However, when reading the 

document to find the in-situ data, we found that the actual data were not available. What is 

presented in RIDP 3 is a series of figures that depict the Areas surveyed, and, at each in-situ 

measurement point, there is a marker. The legend for the figures says that each marker is 

representative of a range of concentrations for the given radionuclides. For example, Figure 10 of 

RIDP 3 gives the measured activities of 137Cs in Areas 8 and 10, but the range of possible 

concentrations for each point is quite large. Therefore, we were unable to reproduce exactly how 

the inventories were calculated starting from the raw in situ data itself. Upon reading other RIDP 

reports, it was found that RIDP reports 4 and 5 appear to give numerical values for the in-situ 

measurements.

Table A-2 of McArthur 1991 provides the inventory of each Area and its regions as taken from 

their respective RIDP reports, and has not been decay-corrected in any way. Appendix A of 
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McArthur 1991 says that the inventories in Table A-2 for Area 10 were the sum of the 

inventories for regions SE-1 and SE-2, plus 65% of the inventory for SE-3. Table A-1 of 

McArthur 1991 gives the assumed concentrations of the ‘unsurveyed’ regions of each area for 

various nuclides, which is used for Table A-2 as well. Table 5 of RIDP 3 gives the inventory of 

each radionuclide for the regions that comprise Areas 8 and 10, as well as the area of each 

region, and, using these data, we were able to reproduce the inventories for all nine nuclides that 

are given in Table A-2.

The inventories in Table A-2 still need to be decay-corrected to become the values given in 

Table 5 of McArthur 1991, which is also Table 4-4 of the NTS TBD 4. McArthur 1991 clearly 

states that the decay corrections were done such that the inventories in Table 5 are representative 

of January 1, 1990. We tried to do the decay corrections for 137Cs, 90Sr, 241Am, and 239,240Pu 

using the half-lives given by Table 1 of McArthur 1991. We were able to reproduce the 

inventory values for Area 10 in Table 5 of McArthur (Table 4-4 of the TBD) for 137Cs, 241Am, 

and 239,240Pu, within error and significant figure constraints. However, there is a large 

discrepancy in the inventory we calculated for 90Sr and what is reported in the documents. (See 

below).

Nuclide SC&A Calculation 

(Ci) In Document (Ci)

Cs-137 84.3 84

Sr-90 68.1 55

Am-241 19.4 19

Pu-239,240 106 110

When trying to figure out why we could not reproduce the decay-corrected 90Sr inventory, we 

noticed that McArthur 1991 mentions several times that the data from the RIDP reports (those 

that are in Table A-2) were re-evaluated and in some cases recalculated to give the inventories in 

Table 5 of McArthur 1991 and Table 4-4 of the NTS TBD. It is our best guess that the 90Sr data 

(and others for different nuclides/areas) were reevaluated by McArthur, and a different inventory 

value was established. McArthur 1991 mentions that the data from the five RIDP reports were 

reevaluated so that measurements that were below the MDA were treated consistently.

Overall, while we can replicate the data in Table A-2 of McArthur 1991, we cannot replicate all 

of the inventory values in Table 4-4 of the NTS TBD due to the fact that some data from the

RIDP reports were reevaluated when calculating the inventories present in Table 4-4. Also, the 

actual in-situ data are not available in most of the RIDP reports, just ranges of activity on a map 

of each area.

Going from Table 4-4 to Table 4-5

Considering the same four nuclides (137Cs, 90Sr, 241Am, and 239,240Pu) for Area 10, we attempted 

to reproduce the values listed in Table 4-5 of the NTS TBD. Using the values given in Table 4-4 

as is, we first divided the inventory (Ci) by the given area (mi

2

), and converted this to Bq/m2. 

These values then need to be decay corrected back to 1963. The NTS TBD does not specifically 

state the date that the values are decay corrected to, just that it is corrected to 1963. We assume a 

date of January 1, 1963 as the date for decay correction. For three of the four nuclides, we 
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selected for Area 10, we were able to reproduce the Bq/m2for 1963, as given in Table 4-5 within 

rounding error. For 137Cs, the value calculated was 1.11E05, and the value we calculated is 

1.15E05. Hence, good agreement. However, when we use a starting date of January 1, 1991 and 

a 137Cs half-life of 30 years (instead of 30.2), then we calculate 1.15E05 Bq/m2 for the 1963 

decay-corrected 137Cs contamination. We also noticed that on page 20 of the NTS TBD, it is 

stated that “...because the data in Table 4-4 are representative of soil contamination in 1991, the 

values in Table 4-5 were decay-corrected to the beginning of 1963.”

As stated earlier, McArthur 1991 clearly states several times that the inventory values presented 

were decay corrected to January 1, 1990. This raises questions as to whether some of the data in 

Table 4-5 used 1991 as a starting year instead of 1990 for decay-correction, and at the very least, 

the wording in the TBD should be changed to reflect that the McArthur data are representative of 

1990. This one-year difference is not that much of an issue for the longer-lived nuclides, but if 

the wrong year was used for decay correcting the shorter-lived nuclides, it could require some 

corrections.