DISCLAIMER: This is a working document provided by the Centers for Disease Control and Prevention (CDC) 

technical support contractor, SC&A for use in discussions with the National Institute for Occupational Safety and 

Health (NIOSH) and the Advisory Board on Radiation and Worker Health (ABRWH), including its Working Groups or 

Subcommittees. Documents produced by SC&A, such as memorandum, white paper, draft or working documents are 

not final NIOSH or ABRWH products or positions, unless specifically marked as such. This document prepared by 

SC&A represents its preliminary evaluation on technical issues.

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

Memorandum

To: Subcommittee for Procedure Reviews 

From: Robert Anigstein, SC&A, Inc.

Date: August 17, 2021

Subject: Reply to NIOSH Response to SC&A Observation 6 on DCAS-PER-057

Introduction

During the meeting of the Advisory Board on Radiation and Worker Health Subcommittee for 

Procedure Reviews on February 18, 2021, SC&A was tasked with addressing the National 

Institute for Occupational Safety and Health (NIOSH) response to SC&A’s observation 6 on 

DCAS-PER-057: “NIOSH used efficiency measures to estimate internal doses to the kidneys” 

(SC&A, 2016). The basis of the observation was NIOSH’s use of an efficiency method for 

assigning internal doses from intakes of radionuclides. NIOSH developed a tool, the Chronic 

Annual Dose Workbook (CADW), that calculates annual internal doses from annual intakes. 

SC&A (2016) performed several independent dose calculations that confirmed the NIOSH 

results in cases where workers were exposed to a uniform intake during each of several years of 

exposure; i.e., the intake was uniform during each year of exposure, although it could vary year 

by year. However, SC&A found discrepancies in cases where the intake rate was not uniform 

during one or more years: for instance, if the worker’s employment began or ended during a 

given year, or if the operation of the facility where the worker was employed changed during a 

given year. An example of the latter occurrence was the end of the operational period at General 

Steel Industries, which occurred on June 30, 1966. 

NIOSH calculated internal doses from intakes that began or ended during a calendar year by first 

calculating the total intake for the year, then prorating that intake to reflect the exposure duration 

during that year. Because of the long retention of uranium aerosols in the respiratory system, 

intakes occurring only during the first part of a given year produce higher doses than if these 

same total intakes were evenly distributed over the entire year: the longer the uranium intakes 

remain in the body, the higher the dose. Conversely, intakes occurring only during a later part of 

a given year produce lower doses than if these same total intakes were evenly distributed over 

the entire year.

NIOSH Response

In its response to the SC&A comments, NIOSH (2017, p. 2) stated “that the technique does 

cause an over or underestimate of the dose during the year of the intake but the opposite effect 

occurs in subsequent years.” NIOSH (2017, p. 2) further stated that “the CADW tool has been 

modified so that it now allows partial years of exposure to be used.” This last statement is correct 

in that the dose reconstructor no longer needs to calculate the prorated intake if the intake occurs 
SC&A, Inc.

Observation 6 on DCAS-PER-057, page 2 August 17, 2021

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

during only a part of a given year—the CADW tool does this automatically. However, the 

subsequent dose assessment is still based on a uniform (albeit prorated) intake rate during the 

entire year. 

Resolution

This issue was resolved during the February 18, 2021, meeting of the Subcommittee for 

Procedures Review. During the course of the meeting, David Allen (NIOSH/DCAS) stated:

I've told our dose reconstructors they could still prorate and use that for most 

cases, but if it gets into the 45 to 52 percent range, the best estimate range, they 

should use IMBA [Integrated Modules for Bioassay Analysis], which is what 

they've been doing since then. [ABRWH, 2021, p. 72] 

SC&A agrees with this resolution and recommends that the observation be closed by the 

Subcommittee. 

References

Advisory Board on Radiation and Worker Health (ABRWH). (2021). Subcommittee for 

Procedures Review Thursday, February 18, 2021. [Transcript of teleconference meeting].

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2021/sctr021821-508.pdf

National Institute for Occupational Safety and Health (NIOSH). (2017). NIOSH response to 

Sanford Cohen & Associates review of DCAS-PER-057 [Response paper].

SC&A, Inc. (2016). DCAS-PER-057, Subtask 4: Review of five cases reevaluated by NIOSH 

using TBD-6000, appendix BB, revision 1 (SCA-TR-2016-PER057-ST4, rev. 0).