Supplemental M&C Data Sufficiency, 

Adequacy, and Precedent Discussion

Joe Fitzgerald, MS, MPH

Bob Barton, CHP

Advisory Board on Radiation and Worker Health, Metals and 

Controls Corp. Work Group

May 12, 2023
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Background

 M&C work group (WG) tasked SC&A (March 3, 2022) to focus on 

any remaining lines of inquiry or outstanding issues relevant to 

WG’s review of SEC-00236 evaluation report (ER)

 SC&A’s issued supplemental review on August 22, 2002. Based on:

– Record of WG discussions

– Former worker input

– Supporting NIOSH and SC&A reports, responses, white papers, and 

presentations

 Purpose: Support M&C WG in its assessment and interpretation of 

proposed exposure modeling and bounding assumptions

 Three lines of inquiry applied
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Line of inquiry 1

Are conditions and work activities associated with the M&C 

residual period unusual or different such that (a) standard 

modeling procedures do not apply and (b) exposure potentials 

higher than those addressed by OTIB-0070 and TBD-6000, and 

supporting bounding analyses may have resulted?
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Line of inquiry 1: Background

 Concern: M&C maintenance activities during residual period 

may have been unique and dissimilar to activities at other 

Atomic Weapons Employer (AWE) facilities

– Intrusiveness (excavations, pipe cutting, and cleaning)

– Work environments (confined spaces)

– Uncertain or unknown source terms (contaminated pipe 

sediments/scale, effect of coagulants, potential dilution over time) 

 NIOSH: “M&C operations were similar to operations at [other 

AWE sites]” and the “methods proposed for M&C by NIOSH 

and SC&A are similar and consistent with those previously 

approved by the Board” (NIOSH, 2020a, slide 12)
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SC&A review for line of inquiry 1

 Salient discussion point is the unknowns and uncertainties 

associated with exposure pathways

– Regular releases of coagulant oil into drainage system

– Cutting of pipes containing contaminated scale

– Maintenance work activities performed in confined spaces (elevated 

dust loading/resuspension of contamination)

 Unlike decontamination and decommissioning (D&D) workers, 

M&C maintenance workers were unaware of radiological 

contamination and were essentially unprotected
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Discussion for line of inquiry 1

 Standard exposure model, as founded in OTIB-0070 and TBD-6000, and 

complemented by six exposure pathway models, may not be sufficiently 

accurate or appropriate for one or more pathways because:

– Higher exposure potentials than can be appropriately bounded might have existed

– Is there sufficient information to rule out the possibility?

 NIOSH response: “incorporated extreme conservatism in its modeling to 

account for intrusive activities, high exposure conditions, uncertain facility 

activities, or unknown contamination sources” (NIOSH, 2023, p. 17)

 Work group will need to judge whether this approach is plausible, given:

– Level of uncertainty involving bounding exposure models

– Lack of information for direct M&C worker exposures during the residual period
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Line of inquiry 2

Are the exposure pathway bounding methods prescribed by the 

ER and subsequent NIOSH reviews appropriate and consistent 

with how other AWE sites have been addressed?
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SC&A review for line of inquiry 2

 Examined whether: 

– NIOSH bounding approach for exposure pathways for M&C consistent 

with past practice and precedent for AWE residual periods

– Dose reconstruction methods for M&C pathways are plausible and 

sufficiently accurate

 Like other AWEs: 

– Residual uranium and thorium contamination, and many work activities 

were similar

– However, nature of some M&C activities likely differed by degree of 

intrusiveness: Placed workers close to elevated contamination sources 

in normally inaccessible locations (e.g., subsurface maintenance 

activities)
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Board policy decision on back extrapolating 

survey data

 Are such bounding formulations sufficiently accurate?

 Is it plausible to back apply them for a 27-year period when 

actual information about M&C work activities or conditions is 

lacking?
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WG considerations for inside subsurface 

(line of inquiry 2)

 Each AWE had its own unique operations, equipment, and facility engineering; 

radiological, chemical, and mechanical processes; drain pipe composition and 

layout; and effluent handling practices.

 For M&C, regular releases of coagulant oil may have influenced consolidation 

and concentration of contaminated sediments.

 To unclog drainage pipes, M&C workers cut and cleaned out pipes, with 

potential exposure to contaminated sediments and internal scale. 

 Presence and effect of extensive confined spaces at M&C not reflected in 

exposure modeling. Leads to increased dust loading and resuspension of 

contaminant particulates and aerosols.

 Remedial work on drain pipes differed from M&C maintenance and clean out 

activities: The remedial work removed and disposed of the piping, while 

maintenance activities would have included cleaning and repairing pipe sections.
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Supplemental finding 1, inside subsurface 

(line of inquiry 2) 

 Finding 1: The back application of a high 1995 sediment survey result to 

bound inside subsurface activities is not adequately supported by 

information for M&C worker activities from the earlier residual time period

 NIOSH (2023) response:

– Disputes the effects of coagulant oil and cutting of pipe containing contaminant scale 

but does not appear to address the effects of confined spaces 

– Disagrees that there is any difference in how D&D and M&C workers handled pipe 

cutting

 SC&A: WG issue remains the sufficient accuracy of applying pre-D&D 

data and the plausibility of the inside subsurface bounding model
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WG considerations for outside subsurface 

areas (line of inquiry 2)

 Appropriateness of NIOSH bounding assumption can be judged on 

whether: 

– Outside maintenance excavations prior to 1984 substantially spread, diluted, or 

altered the levels/contours of elevated subsurface contamination

– Is the 95th percentile sufficiently conservative and plausible to back apply these 

measurements?

 Burial site and Metals Recovery Area:

– Uranium soil concentrations in excess of 5,000 pCi/g and 17,000 pCi/g, respectively

– CPS found “presence of contaminants, at nonuniform distributed concentrations, at 

varying depths” (CPS, 1992, p. 3)

 Key question: Can “blended” bounding model accommodate significantly 

varying uranium concentrations (hot spots) at varying locations and 

depths?
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Conclusions for outside subsurface areas 

(observation 1, line of inquiry 2)

 Observation 1: The use of blended D&D characterization survey 

data from 1984 and 1992 to support a bounding dose from outside 

subsurface activities may not be necessarily bounding for work in 

nonuniform soil contamination, given the presence of hot spots that 

existed during the residual period at M&C (SC&A, 2022, p. 27).

 NIOSH response: 95th percentile distribution is applied as opposed 

to maximum value for hot spots, given that they are limited 

exposures and not normally expected condition (NIOSH, 2023, 

p. 20).

 SC&A: SC&A accepts NIOSH’s clarification of this issue given the 

availability of soil measurements.
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Line of inquiry 3

Are the available source term, survey data, and other information 

applied by NIOSH to support its dose bounding methods 

sufficiently accurate and plausibly applied?
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SC&A review for line of inquiry 3

 NIOSH guiding principle for addressing the “uncertainty [or understanding] around the 

work performed” is that it is “NOT an issue when the bounding doses are very low, and 

specifically, during AWE residual periods such as at M&C” (NIOSH, 2020a, slide 14).

 Question of deriving bounding dose in absence of monitoring data by applying sufficient 

conservatism is not without precedent and carries with it the question of plausibility.

 Board Chair noted during Linde review: “carried to an extreme, we could take any site 

. . . and we could come up with what we think is the highest possible exposure at that 

site that would occur, and that would be bounding, and apply that to everybody that ever 

worked at the site.” However, “is that a plausible bound? And then, who are we trying to 

characterize?” (ABRWH, 2011, p. 129).

 NIOSH’s position that it has “incorporated extreme conservatism in its modeling to 

account for intrusive activities, high exposure conditions, uncertain facility activities, or 

unknown contamination sources” (NIOSH, 2023, p. 17) raises the very question cited by 

the former Board Chair.
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Considerations for confined spaces 

(line of inquiry 3)

 Not apparent how Mound project data being applied for M&C outdoor 

dust loading factor addressed increased resuspension or dust loading in a 

confined space (e.g., various manholes, trenches, pits, and vault spaces 

at M&C)

 Lack of natural ventilation in a confined space is demonstrable and has a 

direct impact on resuspension and dust loading

 M&C maintenance workers entered confined spaces to perform various 

activities:

– Excavations

– Operate saws, grinders, and drills

– Pull, cut, clean out, and repair drain and air lines 

 Potential for exposure to fine aerosols and particulates generated from 

sawing, grinding, drilling, and welding activities
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Key question for confined space dust loading 

assumption

Were the dust loading concentrations within the trenches of the 

Mound excavation adequately similar that these data can be 

applied to corresponding confined work spaces at M&C?
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Finding 2 on confined spaces 

(line of inquiry 3)

 Not apparent how Mound project addressed confined space considerations that 

existed at M&C.

 It appears that Mound project air samplers were positioned near to excavation 

activities but were not sampling air at (or within) the trenches.

 Finding 2: The application of surrogate data from the Mound project to provide 

a dust-loading factor for M&C subsurface activities does not satisfy the Board’s 

surrogate data policy.

 NIOSH response: SC&A seeks clarification on the finding. The response has 

provided an account of past NIOSH and SC&A exchanges where it is 

acknowledged that dust loading factors in OTIB-0070 will need to be “uniquely 

evaluated at each site” and that “one size will not fit all” (NIOSH. 2023, pp. 21–

22).

 SC&A: Reaffirms its position on Board judgment concerning surrogate data.
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Conservatism of 95th percentile 

(line of inquiry 3)

 NIOSH original position: “M&C’s area monitoring assures that the 95th percentile soil- contamination value is conservative based on routine surveys of Building 10 during the 

first 14 years of the residual period (1968-1981),” with obtained surveys for 1968–1969 

(NIOSH, 2020b, pp. 7–9).

 Cites contamination survey requirements and procedures from the health and safety 

manual, NRC inspections during the residual period for the regulated HFIR facility, and 

“typical” alpha contamination surveys for HFIR.

 SC&A observation 2: References to the M&C safety and health manual, NRC 

inspection results, operator training, and other programmatic considerations do not 

necessarily substantiate the conservatism of the 95th percentile soil contamination value 

being applied.

 NIOSH response: Is not using the M&C safety manual, NRC inspection results, operator 

training, and other programmatic considerations to “justify” using the 95th percentile 

(NIOSH, 2023, p. 23).

 SC&A comment: Reaffirms its observation and seeks clarification of how such 

programmatic considerations assure the conservatism of NIOSH’s bounding values.
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Overall policy considerations for the WG and 

Board

 Precedent suggests that while less precision or technical accuracy can be 

tolerated if the exposure of a worker cohort is relatively low, the use of a high 

exposure or concentration values based on these data to bound or represent 

that of other workers in a facility or on a site for long time periods would not be 

appropriate if: 

– their exposure potential could be higher,

– conditions were different, or 

– there is lack of information upon which to make those judgments. 

 As noted in the Board’s deliberations on the Linde residual period, the question 

of where to draw the line for applying such bounding constructs is a subjective 

one, weighing the precision (or accuracy) of the bounding assumption and data, 

as well as the plausibility of their application to the target worker population.
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NIOSH response to general conclusions

NIOSH 2023

 NIOSH response cites SC&A’s general 

conclusion but appears to parse it:

– Cites low exposure precept and 

attributes it to M&C. NIOSH finds that it 

has a “more complete data set” for 

M&C and a better understanding of 

M&C work processes than it did with 

Linde

– Cites application of “high exposure” for 

bounding purposes and attributes it to 

Linde. NIOSH finds Linde case does 

not apply to M&C because potential 

exposure level is much higher 

(5,479 mrem/yr CED)

SC&A 2023

 SC&A is not referring to a specific 

bounding value (i.e., Linde), but rather to 

site monitoring data not related to actual 

operations being back applied over a 

long period of time with a formulation 

made extremely conservative to 

(1) compensate for the lack of data, and 

(2) address the inherent uncertainties 

and unknowns in the proposed approach

 Original question remains about 

plausibility: Where does the Board 

decide the appropriate application of 

bounding values?
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SC&A general comments on NIOSH response 

to supplemental review

 NIOSH response to SC&A supplemental review issued on January 13, 

2023

 SC&A issued review of NIOSH response on April 25, 2023

 SC&A general comments:

– NIOSH response contains the recurring comment that it does not find any “new 

technical information or technical justifications”

– NIOSH response notes in several places that NIOSH and SC&A “have done 

extensive work” on each issue and have “previously agreed” on them

– Purpose and intent of the WG’s most recent tasking: SC&A was to provide a 

supplemental means to inform final WG deliberations, considering various (and 

additional) interpretations of the plausibility and sufficient accuracy of proposed 

exposure models and bounding assumptions
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Overarching WG question

Are the data sufficiently accurate, appropriate, and representative 

of a set of plausible exposure models to support dose 

reconstruction for M&C workers during the entirety of the residual 

period (1968–1997)?

Ultimately, this is a work group and Advisory Board judgment.
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References

Advisory Board on Radiation and Worker Health. (2011). 75th meeting Thursday February 24, 

2011 [Transcript]. https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2011/tr022411.pdf

Creative Pollution Solutions, Inc. (CPS). (1992). Radiological characterization of Texas 

Instruments, Incorporated Attleboro Industrial Facility Attleboro, Massachusetts. SRDB Ref. ID 

164755, PDF pp. 16–71

National Institute for Occupational Safety and Health (NIOSH). (2020a, Sept. 2). SEC-00236 

Metals and Controls Corp. NIOSH response to working group comments [PowerPoint 

presentation to the Metals and Controls Corp. Work Group]. 

https://ftp.cdc.gov/pub/FOIAREQ/182969-508.pdf

NIOSH. (2020b). Response to comments from the Metals and Controls Corp. Work Group 

meeting held on September 2, 2020 [Response paper]. 

https://ftp.cdc.gov/pub/FOIAREQ/184642_red-508.pdf

NIOSH. (2023). NIOSH response to SC&A’s supplemental review of M&C Work Group issues

[Response paper]. https://www.cdc.gov/niosh/ocas/pdfs/dps/dc-sca-mcwgissues-508.pdf

SC&A, Inc. (2022). Supplemental review of M&C Work Group issues (SCA-TR-2022-SEC002, 

rev. 0). https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-metcontwgissues-508.pdf