DRAFT 

NATIONAL INSTITUTE FOR 

OCCUPATIONAL SAFETY AND HEALTH 

ADVISORY BOARD ON RADIATION AND WORKER HEALTH 

A REVIEW OF NIOSH’S PROGRAM EVALUATION REPORT 

OCAS-PER-008, MODIFICATION OF NIOSH-IREP CANCER RISK MODEL: EFFECT 

OF “COMBINED” LUNG MODEL ON NON-COMPENSABLE LUNG CANCER CLAIMS

Contract No. 200-2009-28555 

SCA-TR-PR2010-0008, Revision 0 

Prepared by 

U. Hans Behling, PhD, MPH 

S. Cohen & Associates 

1608 Spring Hill Road, Suite 400 

Vienna, VA 22182 

Saliant, Inc. 

5579 Catholic Church Road 

Jefferson, Maryland 21755 

December 2010 

Disclaimer 

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

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

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

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

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

information only and that premature interpretations regarding its conclusions are unwarranted.

 
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Document No. 

SCA-TR-PR2010-0008 

S. COHEN & ASSOCIATES: 

Technical Support for the Advisory Board 

on Radiation & Worker Health Review of 

NIOSH Dose Reconstruction Program 

Effective Date: 

Draft – December 15, 2010 

A Review of NIOSH’s Program Evaluation 

Report OCAS-PER-008, Modification of 

NIOSH-IREP Cancer Risk Model: Effect of 

“Combined” Lung Model on Non-Compensable 

Lung Cancer Claims

Page 2 of 26 

Task Manager: 

________________________ Date: ___________ 

U. Hans Behling, PhD, MPH 

Supersedes: 

N/A 

Project Manager: 

________________________ Date: ___________ 

John Mauro, PhD, CHP 

Reviewer: 

 John Mauro 

Record of Revisions 

Revision 

Number 

Effective 

Date Description of Revision 

0 (Draft) 12/15/2010 Initial issue – Cleared for potential Privacy Act-protected information on 01/11/2011 
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TABLE OF CONTENTS 

 

Abbreviations and Acronyms ..........................................................................................................4 

1.0 Statement of Purpose ...........................................................................................................5 

2.0 Subtask 1: Identify the Circumstances that Necessitated OCAS-PER-008........................7 

2.1 NIH-IREP ................................................................................................................7 

3.0 Subtask 2: Assess NIOSH’s Specific Methods for Corrective Action ...............................8 

4.0

.....................................................................................................................12 

Subtask 3: Evaluate the PER’s Stated Approach for Identifying the Potentially 

Affected DRs

4.1 SC&A - General Comments..................................................................................13 

4.2 Limitations and Issues Regarding OCAS-PER-008 ..............................................17 

4.3

..........................................................17 

The Failure of NIOSH-IREP and the Limited Ability of NIH-IREP to 

Account for Age at Exposure/Attained Age

4.4 Summary Conclusions...........................................................................................22 

5.0 Subtask 4: Selection Criteria for a Sample Set of DRs.....................................................24 

6.0 References..........................................................................................................................25 

LIST OF EXHIBITS 

Exhibit 1: Tables 2, 3, and 4 from Apostoaei and Trabalka (2004) ...............................................9 

Exhibit 2: Table 1 and Table 2 from OCAS-PER-008 .................................................................13 

Exhibit 3: NIOSH-IREP PC Results with Dose Entered as a Constant Value .............................15 

Exhibit 4: NIOSH-IREP PC Results with Dose Entered with a Lognormal Distribution............16 

Exhibit 5: SEER Incidence Data for Lung and Bronchus ............................................................19 

Exhibit 6: Lifetime Attributable Risk of Cancer Incidence..........................................................21 

Exhibit 7: Rank by Compensation Rate for Ten NIOSH-IREP Cancer Models..........................23 
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ABBREVIATIONS AND ACRONYMS 

Advisory Board 

or ABRWH Advisory Board on Radiation and Worker Health 

CDC Centers for Disease Control and Prevention 

CFR Code of Federal Regulations 

cSv centi-Sievert 

DDREF Dose and Dose-Rate Effectiveness Factor 

DR Dose Reconstruction 

EAR excess absolute risk 

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000 

ERR excess relative risk 

GSD geometric standard deviation 

Gy gray 

HHS Health and Human Services (U.S. Department of) 

IREP Interactive RadioEpidemiologic Program 

keV kilo electron volt 

NAS National Academy of Sciences 

NCI National Cancer Institute 

NIH National Institutes of Health 

NIOSH National Institute for Occupational Safety and Health 

OCAS Office of Compensation Analysis and Support [now known as the Division of 

Compensation and Analysis Support (DCAS)] 

ORAUT Oak Ridge Associated Universities Team 

PEP Program Evaluation Plan 

PER Program Evaluation Report 

PC Probability of Causation 

rad Radiation Absorbed Dose 

RERF Radiation Effects Research Foundation 

rem Roentgen equivalent man 

SEER Surveillance, Epidemiology, and End Results 

Sv sievert 
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1.0 STATEMENT OF PURPOSE 

 

To support dose reconstruction (DR), the National Institute for Occupational Safety and Health 

(NIOSH) and the Oak Ridge Associated Universities Team (ORAUT) assembled a large body of 

guidance documents, workbooks, computer codes, and tools. In recognition of the fact that all of 

these supporting elements in DR may be subject to revisions, provisions exist for evaluating the 

effect of such programmatic revisions on the outcome of previously completed DRs. Such 

revisions may be prompted by document revisions due to new information, misinterpretation of 

guidance, changes in policy, and/or programmatic improvements. 

The process for evaluating potential impacts of programmatic changes on previously completed 

DRs has been proceduralized in OCAS-PR-008, Preparation of Program Evaluation Reports 

and Program Evaluation Plans (OCAS 2006a), Revision 2, dated December 6, 2006. This 

procedure describes the format and methodology to be employed in preparing a Program 

Evaluation Report (PER) and a Program Evaluation Plan (PEP). 

A PER provides a critical evaluation of the effect(s) that a given issue/programmatic change may 

have on previously completed DRs. This includes a qualitative and quantitative assessment of 

potential impacts. Most important in this assessment is the potential impact on the Probability of 

Causation (PC) of previously completed DRs with PCs of <50%. 

As needed, a PEP may be issued that serves as a formal notification of an impending PER. The 

PEP provides a preliminary description of the issue(s) that will be addressed in the PER, and 

summarizes the likely scope of the effort required to complete the PER. 

During an Advisory Board meeting on May 20, 2010, SC&A was tasked by the Advisory Board 

to conduct a review of OCAS-PER-008, Modification of NIOSH-IREP Cancer Risk Model: 

Effect of “Combined” Lung Model on Non-Compensable Lung Cancer Claims (OCAS 2007). In 

conducting a PER review, SC&A is committed to perform the following five subtasks, each of 

which is discussed in this report: 

Subtask 1: Assess NIOSH’s evaluation/characterization of the “issue” and its potential impacts 

on DR. Our assessment intends to ensure that the “issue” was fully understood and 

characterized in the PER. 

Subtask 2: Assess NIOSH’s specific methods for corrective action. In instances where the PER 

involves a technical issue that is supported by document(s) (e.g., white papers, technical 

information bulletins, procedures) that have not yet been subjected to a formal SC&A 

review, Subtask 2 will include a review of the scientific basis and/or sources of 

information to ensure the credibility of the corrective action and its consistency with 

current/consensus science. Conversely, if such technical documentation has been 

formalized and previously subjected to a review by SC&A, Subtask 2 will simply provide 

a brief summary/conclusion of this review process. 
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NOTICE:

Subtask 3: Evaluate the PER’s stated approach for identifying the universe of potentially 

affected DRs, and assess the criteria by which a subset of potentially affected DRs was 

selected for re-evaluation. The second step may have important implications in instances 

where the universe of DRs is too large and, for reasons of practicality, NIOSH’s reevaluation is confined to a subset of DRs. In behalf of Subtask 3, SC&A will also 

evaluate the timeliness for the completion of the PER. 

Subtask 4: Conduct audits of DRs affected by the PER under review. Based on information 

contained in Table 1 (and discussed in Section 3.1 below), the number of DRs selected 

for audit for a given PER will vary. (It is assumed that the selection of the DRs and the 

total number of DR audits per PER will be made by the Advisory Board.) 

Subtask 5: Prepare a comprehensive written report that contains the results of the above-stated 

subtasks, along with our review conclusions. 
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2.0 SUBTASK 1: IDENTIFY THE CIRCUMSTANCES THAT 

NECESSITATED OCAS-PER-008 

Under federal regulations defined in 42 CFR Part 81 published in May 2002, risk models used by 

NIOSH to adjudicate cancer claims filed by civilian nuclear weapons workers were based on a 

computational software package referred to as NIOSH-IREP (Interactive RadioEpidemiologic 

Program). NIOSH-IREP employs the National Cancer Institute’s (NCI’s) approach to adjust risk 

estimates that are based on direct evidence from Atomic bomb (A-bomb) survivors who were 

exposed as adults. While the NIOSH-IREP models do incorporate a trend of decreasing risk 

with increasing age for some cancers, these models do not incorporate any age-at-exposure 

effects for other cancers that include lung cancer (resulting from non-radon exposures). 

At the time of the rulemaking, it was acknowledged that, in addition to the A-bomb study cohort, 

a substantial body of scientific data existed that suggested a variable effect for the age at 

exposure. While some studies showed no effect, others suggested an increased risk with age at 

exposure. At the time of the rulemaking, these data were regarded as insufficient to support the 

selection of age-specific adjustment factors for the determination of risk. 

As indicated in the rule, HHS is committed to re-evaluate this issue in response to future 

advances in scientific information that may affect NIOSH-IREP models. 

2.1 NIH-IREP 

A concurrent, but separate, computer model referred to as NIH-IREP was developed primarily 

for the purpose of adjudicating cancer claims filed by veterans exposed to radiation during 

military service. Initially, NIOSH-IREP and NIH-IREP were essentially identical. However, in 

May 2003, the NCI substantially updated its NIH-IREP lung model (that includes cancer of the 

trachea and bronchus) for exposure to radiation other than radon. This revision was based on 

more recent analysis of lung cancer incidence among A-bomb survivors (Pierce et al. 2003). 

In the revised NIH-IREP lung model, the excess relative risk (ERR) is adjusted for age at 

exposure and age at diagnosis. Currently, the NIOSH-IREP lung model does not adjust for these 

age-dependent factors. Additionally, the NIH-IREP lung model is less heavily weighted toward 

the multiplicative causal interactions of cigarette smoking and radiation on lung cancer than the 

NIOSH-IREP lung model. 

Due to the fact that the NIH-IREP lung model incorporates more recent data regarding the risk of 

radiation-induced lung cancer, and in compliance with the regulatory mandate to re-evaluate 

NIOSH-IREP upon advances in scientific information, NIOSH issued OCAS-PEP-008, 

Modification of NIOSH-IREP Lung Cancer Risk Model: Impact of “Combined” Lung Model on 

Non-compensable Lung Cancer Claims, on December 7, 2006 (OCAS 2006b), and OCAS-PER008 on April 12, 2007 (OCAS 2007). 
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3.0 SUBTASK 2: ASSESS NIOSH’S SPECIFIC METHODS FOR 

CORRECTIVE ACTION 

NIOSH concluded that the same inputs when entered into NIOSH-IREP and NIH-IREP produce 

PC values that differ significantly and, therefore, posed a potential dilemma to the DR of 

workers covered under the Energy Employees Occupational Illness Compensation Program Act 

of 2000 (EEOICPA). To resolve this issue, NIOSH requested SENES Oak Ridge, Inc., to 

provide an assessment of the differences between the two IREP models. In a report issued in 

September 2004 (Apostoaei and Trabakla 2004), SENES provided a detailed comparison of the 

two models. Key differences included the following: 

 The NIH-IREP risk model is based on lung cancer incidence and smoking history of 

A-bomb survivors for the follow-up period of 1950 to 1994, as compared to the NIOSHIREP lung model that is based on the reduced follow-up period of 1950 to 1990. 

 Considered the most significant difference is the dependency on age at exposure and 

attained age at time of cancer diagnosis on the ERR of lung cancer per unit dose 

(ERR/Sv). No age dependency is included in the NIOSH-IREP lung model. 

 For a “never smoker,” NIH-IREP specifies ERR/Sv for age at exposure of 30 years and 

attained age of 50 years. (As noted above, in NIOSH-IREP, the ERR/Sv represents any 

age at exposure or attained age). 

 While both lung models account for the interaction of smoking and radiation exposure, 

their contribution to total risk is modeled differently. In brief, the NIH-IREP lung model 

relies less on the multiplicative interaction than does the NIOSH-IREP model. Thus, the 

NIH model generally produces a higher PC value for smokers for some exposure profiles, 

and the NIOSH model generally yields higher PC values for non-smokers. 

To illustrate these differences, SENES derived PC values by means of the NIH-IREP and 

NIOSH-IREP lung models for a common lung dose of 50 cSv (or 50 rem) delivered acutely or 

chronically to non-smokers and smokers and for three discrete ages at exposure/attained age 

profiles. As a convenience to the reader, Tables 2, 3, and 4 of Apostoaei and Trabalka (2004) are 

enclosed herein as Exhibit 1. 
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Exhibit 1: Tables 2, 3, and 4 from Apostoaei and Trabalka (2004) 

Table 2. Comparison of 99th percentiles of assigned shares (probability of causation) for lung cancer 

calculated by the NIH and NIOSH versions of IREP for single doses of 50 cSv to a male age 20 at exposure 

and age 40 at diagnosis

Acute exposure Chronic exposure

Photons >250 keV Photons >250 keV Alpha Electrons <15 keV 

Smoking status NIH NIOSH NIH NIOSH NIH NIOSH NIH NIOSH 

Never smoker 52.94 53.75 53.66 50.97 74.99 70.73 78.22 76.81 

Current smoker 

< 10 cigs/day 48.31 29.53 45.81 29.98 71.85 52.69 71.62 55.83 

10-19 cigs/day 47.91 25.62 44.78 25.35 70.76 47.34 70.88 50.85 

20–39 cigs/day 47.78 25.00 44.45 24.57 70.58 45.61 70.74 49.96 

40+ cigs/day 47.72 24.92 44.32 24.15 70.50 45.54 70.70 49.77 

Table 3. Comparison of 99th percentiles of assigned shares (probability of causation) for lung cancer 

calculated by the NIH and NIOSH versions of IREP for single doses of 50 cSv to a male age 40 at exposure 

and age 60 at diagnosis 

Acute exposure Chronic exposure

Photons >250 keV Photons >250 keV Alpha Electrons <15 keV 

Smoking status NIH NIOSH NIH NIOSH NIH NIOSH NIH NIOSH 

Never smoker 28.79 53.75 30.94 50.97 54.03 70.73 57.95 76.81 

Current smoker 

< 10 cigs/day 26.51 29.53 24.56 29.98 49.63 52.69 49.02 55.83 

10-19 cigs/day 25.94 25.62 23.57 25.35 48.97 47.34 48.85 50.85 

20–39 cigs/day 25.88 25.00 23.47 24.57 48.86 45.61 48.35 49.96 

40+ cigs/day 25.85 24.92 23.35 24.15 48.82 45.54 47.78 49.77 

Table 4. Comparison of 99th percentiles of assigned shares (probability of causation) for lung cancer 

calculated by the NIH and NIOSH versions of IREP for single doses of 50 cSv to a male age 20 at exposure 

and age 60 at diagnosis 

Acute exposure Chronic exposure

Photons >250 keV Photons >250 keV Alpha Electrons <15 keV 

Smoking 

Status NIH NIOSH NIH NIOSH NIH NIOSH NIH NIOSH 

Never smoker 44.34 53.75 44.60 50.97 67.76 70.73 71.31 76.81 

Current smoker 

< 10 cigs/day 39.66 29.53 37.21 29.98 64.21 52.69 64.07 55.83 

10-19 cigs/day 39.22 25.62 35.96 25.35 63.08 47.34 63.35 50.85 

20–39 cigs/day 39.17 25.00 35.80 24.57 62.87 45.61 63.12 49.96 

40+ cigs/day 39.13 24.92 35.78 24.15 62.79 45.54 63.02 49.77 
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However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

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

Inspection of Exhibit 1 demonstrates the following: 

 For exposure at age 20 and diagnosis at age 40 (i.e., Table 2 of Exhibit 1), NIH-IREP is 

more favorable for all profiles other than the acutely exposed non-smoker. 

 Table 3 of Exhibit 1, however, shows that for exposure at age 40 and diagnosis at age 60, 

NIOSH-IREP is more claimant favorable for the non-smoker and select profiles of light 

smokers. 

 Table 4 of Exhibit 1 shows higher PC values for the NIH-IREP lung model for all 

profiles other than those involving the “never smoker.” 

 Noteworthy are the identical PC values generated by the NIOSH-IREP lung model 

among the three tables for a given profile that are independent of age at exposure and at 

age of diagnosis. For example, a single acute lung exposure of 50 rem to a never smoker 

yields the identical value of 53.75% for a male (1) exposed at age 20 and diagnosed at 

age 40, (2) exposed at age 40 and diagnosed at age 60, and (3) exposed at age 20 and 

diagnosed at age 60. 

Recommendations Made by SENES

In their report (Apostosei and Trabalka 2004), the authors suggested the following two potential 

options to NIOSH for resolving differences between the two lung models: 

. . . update the lung model in NIOSH-IREP because the new lung model 

represents the most advanced state of knowledge about radiation-induced lung 

cancer. . . . the newer NIH lung model includes more follow-up years of the 

Japanese cohort (1950–1994; Pierce et al., 2003). Also, in perhaps more than 

half of the possible exposure situations the NIH lung model is more claimantfriendly. 

 [But] Since there are categories of people for whom the NIH-IREP lung model is 

less friendly, NIOSH could consider programming NIOSH-IREP to choose 

between the new NIH-IREP lung model and the current NIOSH-IREP lung model, 

and report whatever PC is larger for a given exposure situation . . . [Emphasis 

added.]

A third suggestion offered by the authors of the SENES report was for NIOSH to seek the 

opinion of outside experts regarding the use of the two IREP lung models. 

Recommendations by Outside Experts

In response to SENES’ third suggestion, NIOSH sought the advice of the following four 

internationally recognized experts: 

 David Brenner, PhD, Professor of Radiation Oncology and Public Health, Columbia 

University of Epidemiology, Columbia University School of Public Health 
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 David B. Richardson, PhD, Assistant Professor of Epidemiology, University of North 

Carolina School of Public Health 

 Faith G. Davis, PhD., Professor of Epidemiology and Biostatistics, University of Illinois 

at Chicago, School of Public Health 

 Jonathan M. Samet, MD, MS, Professor and Chairman, Department of Epidemiology, 

John Hopkins University School of Public Health 

Responses by these experts prompted a wide array of comments in the form of questions, 

concerns, and recommendations regarding the selection of either lung model. However, an 

opinion shared by three of the four experts was that the current state of scientific knowledge and 

residual uncertainties regarding the available study data do not support the exclusive use of either 

of the two lung cancer models. For example, in his conclusions, Dr. Jonathan Samet stated 

(Samet 2005): 

. . . In this setting of model uncertainty and the impossibility of selecting one 

model as “correct,” maintaining the two models seems warranted. . . . I would 

not weigh the finding of the new analysis by Pierce et al. so heavily as to use only 

the NIH model. . . . For these reasons, I favor the retention of both models, with 

decision-making based on the higher probability of causation. 

Similarly, Dr. David Richardson stated the following in his conclusion (Richardson 2005): 

The current epidemiological literature provides an inadequate basis for 

determining whether the current NIOSH-IREP or NIH-IREP model provides a 

more appropriate characterization of the joint effects of smoking and radiation 

dose on lung cancer risk. One alternative suggested by NIOSH is to run both 

models and use the result that provides the higher probability of causation. . . .

NIOSH agreed with the experts’ opinion that the most reasonable option within the context of 

compensation and claimant favorability was to reprogram NIOSH-IREP to run both models 

separately and then select the model with the higher PC value for determining the compensability 

of a claim. 

NIOSH-IREP was reprogrammed and, as of February 28, 2006, automatically runs both risk 

models and reports results associated with the higher PC value at the 99th percentile. Important 

to note is that the modified “lung (IDC-9 code 162)” risk model (versions 5.5 and 5.5.1) can 

result in no lower PC value for the same set of claim inputs than had been calculated previously 

under the old versions (i.e., versions 5.4 and earlier) of NIOSH-IREP. 

In addition, the modified NIOSH-IREP versions 5.5 and 5.5.1 incorporate a bias correction 

factor for random errors in dosimetry for “never smokers” who were also exposed to radon. Due 

to a programming oversight, this correction had not been incorporated in previous versions 

(version 5.4 and earlier) for “never smokers,” but had only been applied to smokers. NIOSHIREP v.5.5 corrected the error.
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4.0 SUBTASK 3: EVALUATE THE PER’s STATED APPROACH FOR 

IDENTIFYING THE POTENTIALLY AFFECTED DRs 

On April 12, 2007, NIOSH issued OCAS-PER-008, Modification of NIOSH-IREP Lung Cancer 

Risk Model: Effect of “Combined” Lung Model on Non-compensable Lung Cancer Claims. 

Due to the fact that for select claimants’ exposure profiles, (1) the inclusion of the NIH-IREP 

model had been shown to both increase as well as decrease PC values relative to those generated 

by the NIOSH-IREP model (see Exhibit 1 above), and (2) potential differences on PC values for 

individuals’ lung cancer claims were not readily predictable, NIOSH elected to re-evaluate all 

non-compensated (<50% PC) lung cancer claims. 

In total, NIOSH identified a total of 920 claims that met this criterion. Of the 920 claims that 

were re-evaluated, 729 were “single cancer” claims, with the balance of 191 claims representing 

two or more cancers of which lung (ICD-9 code 162) was at least one of the cancers. The reevaluation showed that, of the 920 claims, a total of 95 claims now yielded higher PC values due 

to the inclusion of the alternative NIH lung cancer risk model, with four claims benefiting from 

the inclusion of the bias correction factor for random errors in dosimetry for never smokers 

exposed to radon. A summary of these results was cited in Table 1 of OCAS-PER-008, which is 

reproduced herein in Exhibit 2. 

Of the 99 claims with higher PC values, the revised PC for 88 claims, nevertheless, remained 

below the threshold value of 45% and precluded further evaluation. The remaining 11 claims 

with preliminary PC values of >45% but <50%, were subject to the more rigorous evaluation 

involving 30 IREP runs with 10,000 iterations each for an average PC value. Lastly, all but 1 of 

the 11 claims represented a DR that had previously been based on a protocol of “maximizing” or 

“overestimating” the lung dose and, therefore, intentionally overestimated the original PC. For 

compensability, these 10 claims, therefore, also required a rework of the organ dose that 

complied with the “best-estimate” approach. Changes in PC values during these sequential steps 

and the final outcome for each of the 11 claims are summarized in Table 2 of OCAS-PER-008 

and enclosed herein in Exhibit 2. As shown in the last column, only two (i.e., claims #3 and #9) 

of the original 920 claims that represented the universe of claims potentially impacted by OCASPER-008 for compensability did, in fact, transition from being non-compensable to compensable. 
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Exhibit 2: Table 1 and Table 2 from OCAS-PER-008 

Table 1: Preliminary evaluation of non-compensable lung cancer claims processed before 

2/28/06: initial effect of NIOSH-IREP “combined” lung cancer risk model on probability of 

causation (PC) based on single IREP run at 2000 iterations 

Type of 

Claim 

Number 

of 

Claims 

No PC 

Increase 

PC 

Increase 

Increase 

Due to 

NIH 

Model 

Increase 

Due to Bias 

Correction 

Factor 

New PC 

< 45% 

New PC 

= 45 – 

49.99% 

New PC 

≥ 50% 

1 cancer 729 652 77 74 3 70 3 4 

>1 cancer 191 169 22 21 1 18 4 0 

Totals 920 821 99 95 4 88 7 4 

Table 2: Final evaluation of 11 claims in which the PC value had increased to ≥45% after 

single IREP run at 2000 iterations using NIOSH-IREP v5.5.1 “combined” lung model 

Claim No. Original DR 

Original Claim 

PC (1 IREP 

Run) 

Interim 

Claim PC 

(1 IREP 

Run) 

Interm 

Claim PC 

(30 IREP 

Runs) 

Final Claim Outcome 

1 Overestimate 45.91% 46.05% 45.26% PC remains below 50% 

2 Overestimate 45.50% 45.79% 44.94% PC remains below 50% 

3 Best Estimate 46.14% 50.94% 50.05% PC exceeded 50% 

4 Overestimate 38.28% 48.08% 43.33% PC remains below 50% 

5 Overestimate 46.56% 53.03% 49.15% PC fell below 50% after 

rework 

6 Overestimate 43.81% 49.04% 48.93% PC remains below 50% 

7 Overestimate 

44.38% 56.15% N/A 

Reworked for reasons 

unrelated to lung model; 

PC decreased to 23.29% 

8 Overestimate 34.35% 46.93% 47.44% PC remains below 50% 

9 Overestimate 

44.60% 47.56% 52.17% 

After ‘best estimate” 

rework, PC=52.08% 

(single IREP run) 

10 Overestimate 41.16% 45.08% 45.87% PC remains below 50% 

11 Overestimate 42.72% 53.22% N/A PC decreased to 42.82% 

after rework 

4.1 SC&A - GENERAL COMMENTS 

Central to the need for the issuance of OCAS-PER-008 was the re-analysis of lung cancer 

incidence in A-bomb survivors as provided in the 2003 study by Pierce et al. and the adoption of 

these data for estimating the risk of lung cancer, as defined in the NIH-IREP model. The major 

change introduced into the NIH-IREP lung model is that the excess relative risk per dose (i.e., 

ERR/Sv) is affected by the individual’s age at exposure and attained age at time of cancer 

diagnosis. In the NIH-IREP model for a given attained age, the ERR/Sv decreases 

exponentially between ages at exposure of 15 and 30, but is constant above this age interval. 

Similarly, for a given age at exposure, the ERR/Sv decreases linearly with attained age, but 
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NOTICE:

only up to the attained age of 50, after which it remains constant. No age-dependency is 

included in NIOSH-IREP lung model, which was principally based on data contained in the 1985 

Report of the NIH Ad Hoc Working Group to Develop Radioepidemiological Tables (NIH 1985). 

With regard to the interaction of smoking and radiation on the induction of lung cancer, both the 

NIH and NIOSH versions of IREP have adopted the same smoking-related adjustment factors 

provided by the Centers for Disease Control and Prevention (CDC) (CDC 1995). However, a 

difference between the two models is the way in which these factors are applied. In brief, for 

NIOSH-IREP, smoking adjustment factors are applied to the parameter α (i.e., ERR/Sv), which 

represents an average for all smoking categories; in contrast, smoking adjustment factors in NIHIREP are applied to the parameter α that is defined by the ERR/Sv representing the “never 

smoker.” 

A brief summary as well as a numerical comparison of parameter values employed in the NIHIREP and NIOSH-IREP risk models are provided in Appendix A and Appendix B, respectively, 

of Apostoaei and Trabalka (2004). SC&A verified the accuracy of these summary model data by 

comparing them against those originally reported by Land et al. 2003 and Land et al. 2002. 

Furthermore, SC&A ran the NIOSH-IREP model using the identical parameter values identified 

in Exhibit 1 above and was able to match all of the corresponding PC values. For illustration, 

Exhibit 3 shows the IREP input data for the 20 year-old male never smoker who was exposed to 

an acute lung dose of 50 cSv and diagnosed with lung cancer at age 40. At the 99th percentile, 

the PC of 53.75% matches the first entry, as previously shown in Exhibit 1. 

Important to note, however, is that all PC values cited in Exhibit 1 (and verified in Exhibit 3) 

assume a lung dose of 50 cSv (or 50 rem) that was entered as a constant (i.e., with no 

uncertainty). Use of an organ dose as a constant is generally limited to a “maximized” and noncompensable DR. Thus, when the lung dose of 50 cSv is entered with a reasonable uncertainty 

(e.g., a lognormal value with a GSD of 1.52), the 99th percentile NIOSH-IREP PC value 

increases to 61.44%, as shown in Exhibit 4. 
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Exhibit 3: NIOSH-IREP PC Results with Dose Entered as a Constant Value 

NIOSH-Interactive RadioEpidemiological Program 

Probability of Causation Results

Uploaded file: N/A DOL District Office: CL

Date of Run: 12/2/2010 NIOSH-IREP version: 5.6

Time of Run: 3:06:02 PM Analytica/ADE version: 3.0

NIOSH ID #: 123456 DOL Case No: 123-45-6789

Claimant Name: John Q. Doe

Claimant Cancer Diagnoses:

Primary Cancer #1: N/A Date of Diagnosis: N/A 

Primary Cancer #2: N/A Date of Diagnosis: N/A

Primary Cancer #3: N/A Date of Diagnosis: N/A

Secondary Cancer #1: N/A Date of Diagnosis: N/A

Secondary Cancer #2: N/A Date of Diagnosis: N/A

Secondary Cancer #3: N/A Date of Diagnosis: N/A

Claimant Information Used In Probability of Causation Calculation:

Gender: Male Race (skin cancer only): N/A

Birth Year: 1940 Year of Diagnosis: 1980

Cancer Model: Lung (162) Should alternate cancer model be run?: No

Smoking history (trachea, bronchus, or lung cancer only): Never smoked

NIOSH-IREP Assumptions and Settings:

User Defined Uncertainty Distribution: Lognormal(1,1) 

Number of Iterations: 2000 Random Number Seed: 99

General Exposure Information:

# Exp. Year Organ Dose (cSv) Exp. Rate Radiation Type

1 1960 Constant (50) acute photons E>250keV 

Radon Exposure Information:

 N/A (applies only to cases of Lung Cancer with Radon Exposures) 

Probability of Causation (PC) *

 1st percentile 4.93 %

 5th percentile 8.63 %

 50th percentile 24.03 %

 95th percentile 45.67 %

 99th percentile 53.75 %

* NIOSH-IREP is programmed with two different lung cancer risk models. Under current guidelines, each lung cancer claim is run 

separately using both risk models and the higher PC will determine the outcome of the claim. The results displayed above are derived 

from the NIOSH-IREP lung model, which is the model that produced the higher PC at the 99th percentile for this particular claim. The 

lower PC at the 99th percentile, derived from the NIH-IREP lung model, is 51.49 %. This lower PC value is reported here for 

information only and will have no bearing on the claim outcome. 
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Exhibit 4: NIOSH-IREP PC Results with Dose Entered with a Lognormal Distribution 

NIOSH-Interactive RadioEpidemiological Program 

Probability of Causation Results

Uploaded file: N/A DOL District Office: CL

Date of Run: 12/2/2010 NIOSH-IREP version: 5.6

Time of Run: 2:59:51 PM Analytica/ADE version: 3.0

NIOSH ID #: 123456 DOL Case No: 123-45-6789

Claimant Name: John Q. Doe

Claimant Cancer Diagnoses:

Primary Cancer #1: N/A Date of Diagnosis: N/A 

Primary Cancer #2: N/A Date of Diagnosis: N/A

Primary Cancer #3: N/A Date of Diagnosis: N/A

Secondary Cancer #1: N/A Date of Diagnosis: N/A

Secondary Cancer #2: N/A Date of Diagnosis: N/A

Secondary Cancer #3: N/A Date of Diagnosis: N/A

Claimant Information Used In Probability of Causation Calculation:

Gender: Male Race (skin cancer only): N/A

Birth Year: 1940 Year of Diagnosis: 1980

Cancer Model: Lung (162) Should alternate cancer model be run?: No

Smoking history (trachea, bronchus, or lung cancer only): Never smoked

NIOSH-IREP Assumptions and Settings:

User Defined Uncertainty Distribution: Lognormal(1,1) 

Number of Iterations: 2000 Random Number Seed: 99

General Exposure Information:

# Exp. Year Organ Dose (cSv) Exp. Rate Radiation Type

1 1960 Lognormal (50, 1.52) acute photons E>250keV 

Radon Exposure Information:

 N/A (applies only to cases of Lung Cancer with Radon Exposures) 

Probability of Causation (PC) *

 1st percentile 3.72 %

 5th percentile 7.93 %

 50th percentile 23.97 %

 95th percentile 49.97 %

 99th percentile 61.44 %

* NIOSH-IREP is programmed with two different lung cancer risk models. Under current guidelines, each lung cancer claim is run 

separately using both risk models and the higher PC will determine the outcome of the claim. The results displayed above are derived 

from the NIOSH-IREP lung model, which is the model that produced the higher PC at the 99th percentile for this particular claim. The 

lower PC at the 99th percentile, derived from the NIH-IREP lung model, is 61.40 %. This lower PC value is reported here for 

information only and will have no bearing on the claim outcome. 
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4.2 LIMITATIONS AND ISSUES REGARDING OCAS-PER-008 

A key limitation to SC&A’s evaluation of OCAS-PER-008 is the fact that for this reviewer, 

IREP remains a “black box” with outputs that cannot be readily verified by manual 

computations. Thus, SC&A’s ability to reproduce PC values cited by Apostosei and Trabalka 

(2004) provides no insight or assurance of compliance with the purported mathematical lung 

models and algorisms that represent NIH-IREP and NIOSH-IREP. Correspondingly, SC&A’s 

concurrence with NIOSH’s method for identifying the universe of potential claims affected by 

OCAS-PER-008, the final evaluation of 11 claims (see Exhibit 2 above), and attendant 

conclusions are conditional. 

SC&A’s conditional concurrence is further clouded by SC&A’s concerns regarding the 

credibility of the NIOSH-IREP and, to a lesser extent, the NIH-IREP lung model for DR, as 

explained below. 

4.3 THE FAILURE OF NIOSH-IREP AND THE LIMITED ABILITY OF NIH-IREP 

TO ACCOUNT FOR AGE AT EXPOSURE/ATTAINED AGE 

In Section D of the Final Rule of 42 CFR Part 81 (Fed. Register/Vol. 67, No. 85, May 2, 2002), 

NIOSH provided the following explanation: 

 Probability of Causation is a technical term generally meaning an 

estimate of the percentage of cases of illness caused by a health hazard among a 

group of persons exposed to the hazard. . . . 

In this rule, the potential hazard is ionizing radiation to which U.S. 

nuclear weapons workers were exposed in the performance of duty; the illnesses 

are specific types of cancer. The probability of causation (PC) is calculated as 

the risk of cancer attributable to radiation exposure (RadRisk) divided by the sum 

of the baseline risk of cancer to the general population (BasRisk) plus the risk 

attributable to the radiation exposure, then multiplied by 100 percent, as follows: 

RadRisk

RadRisk BasRisk x



100%  PC Eq. 1 

From this simple equation, it is clear that the PC value is not only driven by the organ dose, but 

also by the baseline cancer risk to the non-exposed general population. Thus, for a given dose 

of radiation, the PC increases when baseline risk decreases and decreases when baseline risk 

increases. While the baseline risk for a given population cohort is affected by many variables, an 

important risk factor for most cancers, including lung cancer, is attained age. 

NIOSH-IREP. As demonstrated in Exhibit 1, the NIOSH-IREP lung model does not incorporate 

any age at exposure effect, but assumes that the relative excess risk per unit dose is a constant, 

which is used as a simple multiplier for a baseline risk that, nevertheless, may change drastically 

as a function of attained age. 
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As shown in Tables 2, 3, and 4 of Exhibit 1 above, a photon dose of 50 cSv yields the identical 

PC value of 53.75% in behalf of a never-smoking male exposed at age 20 and diagnosed 

20 years later at age 40, and a male exposed at age 40 and diagnosed at age 60, even though the 

baseline lung cancer risk may have changed dramatically. 

To assess just how much the baseline lung cancer risk shifts with attained age, SC&A evaluated 

SEER cancer incidence data for lung/bronchus, shown herein as Exhibit 5. Exhibit 5 shows the 

following baseline age-specific lung cancer incidence values: 

 Individual #1 (exposed age 20 and diagnosed age 40): 

 baseline risk – 10/100,000 or 1 × 10-4 

 Individual #2 (exposed age 40 and diagnosed age 60): 

 baseline risk – 208.4/100,000 or 2.084 × 10-3

By means of these two baseline cancer risks and the common PC value of 53.75% derived by 

NIOSH-IREP, Equation 1 can be used to derive the absolute radiation cancer risk for Individuals 

#1 and #2: 

 Individual #1

PC = 53.75% = 0.5375 = 

RadRisk

RadRisk BasRisk  

 RadRisk = 0.5375 (RadRisk + (1 × 10-4)) 

 RadRisk = 1.162 × 10-4 lung cancer/50 cSv 

 Individual #2

PC = 53.75% = 0.5375 = 

RadRisk

RadRisk x   2 084 10 3 . 

 RadRisk = 2.422 × 10-3 lung cancer/50 cSv 

The above-derived radiation lung cancer risk of 2.422 × 10-3/50 cSv for the older Individual #2 is 

20.8-fold higher than the lung cancer risk of 1.162 × 10-4 /50 cSv for the younger Individual #1. 

In essence, this would imply that the lung cancer risk per unit dose for a male exposed at age 

40 is 20.8 times higher than that of a 20-year old male. 

Based on the steep rise in baseline cancer risk as a function of attained age shown in Exhibit 5, a 

common PC value, as derived by NIOSH-IREP, for these two individuals is counter intuitive and 

raises concerns about the validity of the NIOSH-IREP model that does not address the effects of 

age at exposure and/or attained age. 

NOTICE:
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Exhibit 5: SEER Incidence Data for Lung and Bronchus 

Source: Table 15.9 Reproduced from NCI 2009 

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NIH-IREP. As previously described, the NIH-IREP lung model does take into consideration the 

age at exposure as well as attained age. However, due to the limited available epidemiologic 

data, these two variables received only restricted consideration as modifiers in the NIH-IREP 

lung model, as noted by the National Research Council in their recent BEIR VII Report (NAS 

2006): 

 From page 299 of BEIR VII (NAS 2006): 

 The following general linear dose-response function was used to model 

the ERR or EAR: 

ERR (D, s, e, a) or EAR (D, s, e, a) = 

βs D exp [h(e, a)], (12B-4) 

where D is dose in sieverts, βM and βF are sex-specific estimates of ERR/Sv, e is 

age at exposure in years, and a is attained age in years. The function h includes 

parameters to be estimated. Most commonly, h is of the form 

h(e, a) = γ f(e) + η g(a). (12B-5) 

As noted above, recent analyses by RERF investigators of A-bomb 

survivor solid cancer mortality (Preston and others 2003) and incidence data 

have taken f(e) = e and g(a) = log a; note that exp (η log a) = aη

. Others 

(Kellerer and Barclay 1992) have developed models with g(a) = a. Some post 

risk assessments (BEIR V) have taken h to be a function of sex, age at exposure, 

and time since exposure (t). Note that any two of the variables e, a, and t 

determine the third (t = a – e) so models based on e and t are included in the 

equation (12B-4) specification. 

In recent analyses conducted for the purpose of updating 

radioepidemiologic tables (NIH 2003), the NIH evaluated models of the form 

indicated above, but the ERR was allowed to vary over only a limited range of 

exposure ages or attained ages. . . . [Emphasis added.] 

Thus, the NIH-IREP model allowed the ERR values to vary with age at exposure only over the 

narrow age range of 15 to 30 years and the attained age of only up to 50 years. 

Given the likelihood that a significant fraction of EEOICPA workers were exposed above the age 

of 30 years and attained ages well above 50 years, and the dramatic rise in baseline lung cancer 

incidence above the age of 50 years (see Exhibit 5), the NIH-IREP lung model is only able to 

partially address the critical impacts of age at exposure and attained age in the derivation of PC. 

For illustration, the NIH-IREP PC values of 52.94% for the aforementioned never smoker 

exposed at age 20 and the PC value of 28.79% for the never smoker exposed at age 40 (see 

Exhibit 1 above), the respective lung cancer radiation risks per 50 cSv of 1.11 × 10-4 and 8.42 × 

10-4 still suggests that the exposed 40-year old is nearly 8 times higher at risk per unit dose than 

the 20 year old. 
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In the 2006 BEIR VII Report, the NAS Committee reviewed and evaluated a total of 17 cancer 

models that included the model used by NIH-IREP (see Table 12B-2, page 300 of BEIR VII, 

NAS 2006). The NAS, however, concluded that model #4 (i.e., the BEIR VII ERR model) 

provided the best fit of data. This model allows for the variation in the ERR with age at 

exposure only over the range of 0 to 30 years, but allows for variation in attained age over the 

full range. By means of the BEIR VII ERR model, the NAS Committee derived lifetime cancer 

incidence risks in Table 12D-1 of the BEIR VII Report as a function of age at exposure for a 

single dose of 0.1 Gy (i.e., 10 rads). 

As a convenience to the reader, Table 12D-1 of the BEIR VII Report is reproduced herein as 

Exhibit 6. The BEIR VII model suggests a steady decline in the lifetime lung cancer risk as a 

function of age at exposure. 

Exhibit 6: Lifetime Attributable Risk of Cancer Incidence 

Table 12D-1 Reproduced from BEIR VII (NAS 2006) 
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4.4 SUMMARY CONCLUSIONS 

SC&A’s comparative evaluation of outputs generated by the two IREP lung models suggests the 

following: 

 NIOSH-IREP lung model generates excessively high PC values due to the model’s 

failure to account for the age at exposure, as well as the attained age of the exposed 

individual at the time of cancer diagnosis. As shown in our example, it is inconceivable 

that an identical acute lung dose received at age 40 is more than 20 times as likely to 

induce a lung cancer as the same dose received at age 20. Our preliminary assessment 

suggests that NIOSH-IREP PC values derived in behalf of persons exposed above the age 

of 30 with attained ages above 50 are progressively and excessively too high. 

 NIH-IREP lung model adjusts on a limited basis the effects of age at exposure and 

attained age. A potentially significant shortcoming of this model is that there is no 

further adjustment for attained age greater than age 50 years. As shown in Exhibit 5 

above, there is an exponential rise in baseline lung cancers above the age of 50, which is 

not accounted for and is a likely contribution to PC values that are still excessive for 

claimants with attained age at time of cancer diagnosis greater than 50 years. (As noted 

above, the BEIR VII model does account for attained ages >50 years.) 

SC&A’s concern regarding the concurrent use of NIOSH-IREP and NIH-IREP as dictated by 

OCAS-PER-008 and their potential contribution to unrealistically high PCs/compensable lung 

cancers parallel concerns raised in the November 2010 draft report entitled, Ten Year Review – 

Phase I Report Dose Reconstruction. 

In Topical Subsection 7, “Individual Dose Reconstruction Compensation Results Based on the 

Cancer Model Used” (Wade and Adams 2010), the authors of the draft report raised the 

following question: 

One question that comes to mind when reviewing the data in Table 9, is whether 

or not this rank by compensation rate “makes sense.” [Emphasis added.] 

Table 9, as referenced above, is reproduced herein as Exhibit 7. Exhibit 7 shows the following: 

 At 3,438 claims, lung cancer (162) represented by far the highest number of total cancer 

claims. 

 Of the 3,428 lung cancer claims, a total of 2,413 claims (or 70.2%) were compensated. 

The compensation rate of 70.2% stands in contrast with the collective compensation rate 

of 28.5 for all cancer claims. 

Although NIOSH provided some compelling reasons that may have contributed to the 

differentially high compensation rate for lung cancer, the potential contribution of the IREP lung 

models and their inherent limitations were not mentioned. 
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SC&A concludes that further discussion by the Subcommittee on Procedures Review regarding 

the use of and appropriateness of both IREP lung models is warranted. 

Exhibit 7: Rank by Compensation Rate for Ten NIOSH-IREP Cancer Models 

Table 9 Reproduced from Wade and Adam (2010) 

Table 9: Rank by Compensation Rate for Ten NIOSH‐IREP Cancer Models

Rank by  

Compensation  

Rate  

NIOSH‐IREP Cancer

Model  

(ICD‐9 Code)  

Percent  

Compensated  

(PC greater than or

equal to 50%)  

Percent Not  

Compensated  

(PC less than

50%)  

Number of

Claims with

this  

ICD‐9 Code  

Percent of Claims

with this ICD‐9 Code

of the Total Number  

Of Claims  

1   Lung (162)   70.2   29.8   3438   22.5  

2   Chronic Myeloid  

Leukemia (205.1)  

59.7   40.3   67   0.4  

3   Non‐melanoma Skin  

Basal Cell (173)  

57.8   42.2   1108   7.3  

4   Acute Lymphocytic  

Leukemia  

(204.0)  

56.9   43.1   65   0.4  

5   Liver (155.0)   48.2   51.8   112   0.7  

6   Acute Myeloid

Leukemia  

(205.0)  

41.6   58.4   149   1.0  

7   Malignant

Melanoma  

(172)  

38.8   61.2   405   2.7  

8   Lymphoma &

Multiple  

Myeloma(200‐203)  

38.1   61.9   1161   7.6  

9   Leukemia, excl. CLL  

(204‐208, excl

204.1)  

35.4   64.6   99   0.6  

10   Other respiratory

(160,161,163‐165)  

34.9   65.1   436   2.9  
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5.0 SUBTASK 4: SELECTION CRITERIA FOR A SAMPLE SET OF 

DRS 

Selection of a sample of DRs affected by OCAS-PER-008 for audit by SC&A may at this time 

be premature and may have to await potential discussion/resolution by the Subcommittee on 

Procedures Review regarding concerns raised by SC&A in Section 4.3 above. 

On the assumption that the Subcommittee may dismiss SC&A’s concerns and accept OCASPER-008 in its present state, the selection of DRs for audit is limited to the following eight 

claims identified in Table 2 of OCAS-PER-008 (and included herein in Exhibit 2): Claims #1, 

#2, #4, #5, #6, #8, #10, and #11). 

Given the limited number of DRs that may require audit, one option may be to audit all eight 

claims. If the Subcommittee were to select only a subset of DRs, priority should be given to 

those DRs with the highest “Interim Claim PC” values, as given in Column 5 of Table 2 in 

Exhibit 2. Claims with the highest re-evaluated PC (but less than 50%) include Claim #5 

(49.15%), Claim #6 (48.93%), and Claim #8 (47.44%). 

Since all eight claims that may be selected for audit were originally DRs that represent an 

“overestimate” of lung (152) dose, our audit of these claims would entail a full-blown bestestimate assessment of assigned doses from all sources of external and internal lung doses. 

 
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6.0 REFERENCES 

42 CFR 81. 2002. Guidelines for Determining the Probability of Causation Under the Energy 

Employees Occupational Illness Compensation Program Act of 2000; Final Rule, Federal 

Register/Vol.67, No. 85/Thursday, May 2, 2002, p. 22296. 

42 CFR 82. 2002. Methods for Radiation Dose Reconstruction Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule, Federal 

Register/Vol.67, No. 85/Thursday, May 2, 2002, p. 22314. 

Apostoaei, A. I. and Trabalka, J. R. 2004. Differences in the Estimation of Lung Cancer Risk 

Between NIOSH-IREP and NIH-IREP, SENES Oak Ridge, Inc.: Oak Ridge, Tennessee. 

Centers for Disease Control and Prevention (CDC) 1995. Morbidity and Mortality Weekly 

report: Cigarette Smoking Among Adults – United States, 1993; Excerpted in JAMA 1995; 

273(5):369-370. 

Kellerer, A.M. and M. Barclay. 1992. Age Dependencies in the Modeling of Radiation 

Carcinogenesis. Radiat. Prot. Dosim. 41:273-281. 

Land, C.E., E.S. Gilbert, J.M., Smith, F.O. Hoffman, I. Apostoaei, and B. Thomas, 2002. 

Draft Report of the NCI-CDC Working Group to Revise the 1985 NIH Radioepidemiological 

Tables. May 17, 2002. U.S. Department of Health and Human Services, National Institutes of 

Health, National Cancer Institute, Bethesda, Maryland. 

Land, C.E., E.S. Gilbert, J.M., Smith, F.O. Hoffman, I. Apostoaei, B. Thomas, D.C. Kocher, 

2003. Report of the NCI-CDC Working Group to Revise the 1985 NIH Radioepidemiological 

Tables. NIH Publication No. 03-5387. U.S. Department of Health and Human Services (HHS), 

National Institutes of Health, National Cancer Institute, Bethesda, Maryland. 

NAS 2006. Health Risks from Exposure to Low Levels of Ionizing Radiation, BEIR VII Phase 2, 

National Academy of Sciences, National Research Council of the National Academies, National 

Academies Press: Washington, DC. 

NCI 2009. SEER Cancer Statistics Review, 1975-2006, National Cancer Institute, Bethesda, 

Maryland, http://seer.cancer.gov/csr/1975_2006/, based on November 2008 SEER data 

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