National Institute for Occupational Safety and Health

NIOSH’s Response to SCA-TR-2021-SEC004

and SCA-TR-2021-SEC005

LaVon Rutherford, CHP

NIOSH, Health Science Administrator

Advisory Board on Radiation and Worker Health

Metals and Controls Work Group Meeting

May 12, 2023
Overview

 Introduction

 NIOSH Responses

– SCA-TR-2021-SEC004, “Metals and Controls Corp. 

Exposure Pathway Evaluation” 

– SCA-TR-2021-SEC005, “SC&A Commentary on NIOSH’s 

Approach to Quantifying Outdoor and Indoor Airborne 

Dust Loadings,”

 NIOSH Conclusion

5/12/2023 2
Introduction 
Introduction (1 of 2)

 On October 25, 2021, NIOSH received the SC&A report 

Metals and Controls Corp. Exposure Pathway 

Evaluation [SC&A 2021a], which provides SC&A's 

evaluation of the six exposure pathways

 NIOSH’s response paper was issued on January 12, 

2022

 The response paper addresses comments, 

observations, and findings from that review

5/12/2023 4
Introduction (2 of 2)

 As for the second paper, SCA-TR-2021-SEC005, SC&A 

Commentary on NIOSH’s Approach to Quantifying 

Outdoor and Indoor Airborne Dust Loadings, NIOSH 

will refer to their previous presentation

 NIOSH’s response paper was issued on January 12, 

2022

 The response paper addresses comments from that 

review

5/12/2023 5
NIOSH Response to SC&A’s Metals and Controls 

Corp. Exposure Pathway Evaluation and Dust 

Loading Commentary
SC&A Finding 1 - Building 10 subsurface external 

exposures not bounded (1 of 2)

 SC&A finds that NIOSH's proposed external dose rate 

assumptions are inconsistent with the contamination 

levels assumed for the subsurface of Building 10. 

SC&A's independent calculations suggest dose rates 

from the modeled pathway are expected to be 

substantially greater. 

5/12/2023 7
SC&A Finding 1 - Building 10 subsurface external 

exposures not bounded (2 of 2)

 NIOSH's 2017 SEC ER proposed using the 95th 

percentile dosimetry values (with adjustments for 

missed dose) of 200 mrem/year (16.7 mrem/month). 

 SC&A believes it is more appropriate to assign 

elevated subsurface exposures inside Building 10 using 

the 95th percentile of the dosimetry with occupancy 

adjustments

5/12/2023 8
NIOSH Response (1 of 2) 

 Although SC&A recommends using the 95th percentile 

film-badge data for the indoor subsurface model, they 

do not recommend it for outdoor subsurface exposures 

because of their comparison to a value calculated using 

Federal Guidance Report (FGR) No. 12. 

 NIOSH concludes using the actual soil contamination 

data workers were exposed to (as calculated by SC&A) is 

more appropriate for modeling subsurface exposures. 

5/12/2023 9
NIOSH Response (2 of 2) 

 NIOSH can use the dose coefficients for exposure to soil 

contaminated to an infinite depth tabulated in FGR 12 

and the same soil contamination values used in our 

subsurface internal exposure model to assign doses

 If NIOSH changes the model, we will also use this 

method to model outdoor subsurface exposures to 

remain consistent

5/12/2023 10
SC&A Observation: Indoor and outdoor subsurface scenarios

 SC&A reviewed the claimant interviews and does not 

believe that there is sufficient evidence to limit any 

individual's subsurface exposures to a single 

subsurface scenario. 

 The interviews indicate that, irrespective of an 

individual's job title, they may have been asked to 

complete any task on site.

 SC&A believes that means an individual could have 

participated in both indoor and outdoor subsurface 

scenarios within a year

5/12/2023 11
NIOSH Response – Subsurface exposure duration 

 NIOSH's understanding of this observation is that SC&A 

recommends increasing the total subsurface exposures 

duration (combined indoor and outdoor) to four months

 Although this assumption is inconsistent with the 

interviews indicating two months total, NIOSH will 

consider this change 

 This change would amount to four months of subsurface 

exposure, and NIOSH would assign the remaining eight 

months as “remaining exposures” 

5/12/2023 12
SC&A Finding 2 - Welding prep resuspension factor

 SC&A raised a concern (finding 2) in its 2019 (SC&A, 

2019) and 2020 (SC&A, 2020b) reviews of welding and 

thorium activities that a resuspension factor of 10-3/m 

may not be adequate to represent the dust generated 

by grinding and wire brushing to prepare a surface for 

welding

 The work group members echoed this concern during 

the September 2, 2020, M&C Work Group meeting 

 SC&A agrees that this is a "TBD issue" rather than an 

SEC issue

5/12/2023 13
NIOSH Response – Resuspension Factor 

 NIOSH believes a 10-3 resuspension factor is 

representative and bounding for work activities and 

conditions at M&C

 Work activities are a distribution of actions in which the 

majority of resuspension factors in Table 3-1 of OTIB0070 are sizably smaller (in most cases orders of 

magnitude smaller) than the proposed 10-3 resuspension 

factor

5/12/2023 14
SC&A Exposure Pathway Conclusion

 With the modifications suggested in the finding and 

observation, SC&A believes internal and external 

doses from each maintenance exposure pathway can 

be bounded

 SC&A recommended NIOSH develop guidance for 

dose reconstructors

 NIOSH plans to turn the current DR methodology into 

a TBD

– Guidance developed during this review will be 

incorporated into the TBD 5/12/2023 15
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.