Department of Health and Human Services with stylized eagle made up of silhouetted human faces C D C
Department of Health and Human Services
Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health (NIOSH)
Search NIOSH NIOSH Home NIOSH Topics Site Index Databases and Information Resources NIOSH Products Contact Us

NIOSH Program Area:

Radiation Dose Reconstruction

 

Probability of Causation--NIOSH-IREP

On May 2, 2002, the Department of Health and Human Services published its final rule on the guidelines to be used by the Department of Labor (DOL) to determine the probability that a cancer included in a claim under The Act was caused by workers' exposure to radiation during nuclear weapons production. DOL will make such a determination, determining "probability of causation," for each claim for which NIOSH is required to complete a radiation dose reconstruction. Generally, with some exceptions, these claims are for workers who are not a member of the Special Exposure Cohort.

Notice of Revision of Guidelines on Non-Radiogenic Cancers

In a notice of proposed rulemaking published in the Federal Register on March 21, 2011, the Department of Health and Human Services (HHS) proposed to treat chronic lymphocytic leukemia (CLL) as a radiogenic cancer under the Energy Employees Occupational Illness Compensation Program Act of 2000 (EEOICPA) (76 FR 15268). On February 6, 2012, the final rule was published. Under the final rule, CLL will now be treated as being potentially caused by radiation and as potentially compensable under EEOICPA. This reverses the earlier decision by HHS to exclude this cancer from consideration. This change will become effective on March 7, 2012.

Notice of Proposed Rulemaking:
Guidelines for Determining Probability of Causation Under the Energy Employees Occupational Illness Compensation Program Act of 2000; Revision of Guidelines on Non-Radiogenic Cancers
(March 21, 2011)
this document in PDF PDF 270 KB (8 pages)

Final Rule:
Guidelines for Determining Probability of Causation Under the Energy Employees Occupational Illness Compensation Program Act of 2000 (The Act); Revision of Guidelines on Non-Radiogenic Cancers
(February 6, 2012)
this document in PDF PDF 145 KB (4 pages)

Please Note: The Final Rule does not add CLL to the list of "specified cancers" or qualifying cancers for the Special Exposure Cohort.

Top of Page

Probability of Causation Final Rule

Final Rule: Guidelines for Determining the Probability of Causation--42 CFR 81
this document in PDF PDF 184 KB (20 pages)

Public Comments on the Probability of Causation Rule

Top of Page

NIOSH-IREP

To determine probability of causation for a cancer claim under The Act, DOL uses a computer software application NIOSH has developed in collaboration with the National Cancer Institute, called NIOSH-IREP. This computer software is a science-based tool that allows DOL to determine the probability a cancer was caused by a person's radiation dose from nuclear weapons production work. The actual outcome of a claim depends on a number of important factors such as the dose estimates of past exposures and the type of cancer that has been diagnosed. DCAS is responsible for maintaining and updating this software and the scientific elements (cancer risk models) that it uses.

NIOSH-IREP (on-line, interactive software program)
External Link: http://www.niosh-irep.com/irep_niosh

User's Guide for the Interactive RadioEpidemiological Program (NIOSH-IREP)

  • User's Guide Version 5.7.1
    (July 21, 2014)
    this document in PDF PDF 1 MB (22 pages)

    NIOSH-IREP was upgraded to v.5.7 on July 21, 2014. The main change in Version 5.7.1 allows for age at exposures as low as 14 years old (previously, only exposures of 15 years or older were allowed). The following updates were made:

    1. Changed Minimum Exposure Age:
      The original domain of application of NIOSH-IREP included the ability to estimate Probability of Causation (PC) for exposures to radiation at ages 15 or greater. The minimum exposure age has now been lowered to 14 years.

    2. Increased Number of Multiple Primary Cancers:
      The maximum number of primary cancers allowed by NIOSH-IREP was increased from 120 to 240.

    3. Improved Accessibility for Multiple Primary Cancers Input Screen:
      The Multiple Primary Cancers Input screen was modified to operate with recent versions of commonly-used web browsers (2014 and earlier versions of Internet Explorer, Chrome, Safari, and Firefox).

  • Attachments: Example input files that may be uploaded into NIOSH-IREP. Page 7 of the User's Guide provides instructions for uploading input files; summaries of the example files are provided on pages 20-22. To work properly, the files must first be saved to a disk or to your computer. From there, they can be uploaded directly into the IREP program.
    Example 1a
    (Microsoft Excel File; 169 KB)

    Example 1b
    (Microsoft Excel File; 169 KB)

    Example 2a
    (Microsoft Excel File; 169 KB)

    Example 2b
    (Microsoft Excel File; 169 KB)

    Example 3
    (Microsoft Excel File; 169 KB)

    Example 4
    (Microsoft Excel File; 169 KB)

Information regarding the development and use of the NIOSH-IREP program can be found in:

Top of Page

Compensation Results by NIOSH-IREP Cancer Model


Compensation Results by NIOSH-IREP Cancer Model
this document in PDF PDF 168 KB (1 page)

The compensation rates are based on the claims with dose reconstructions approved by NIOSH and sent to DOL through February 20, 2014.

Top of Page

Graphs Showing POC Values for Various Levels of Acute Radiation Exposure


Graphs Showing POC Values for Various Levels of Acute Radiation Exposure
this document in PDF PDF 96 KB (22 pages)

  • What do these graphs illustrate?

    These graphs are intended to illustrate the relationship between the probability of causation (PC) and acute exposure to ionizing radiation for the cancer models employed in IREP. Although these graphs are not in themselves useful for predicting the PC for an individual case, they can be used to examine the relative differences in radiation sensitivity among organs for two selected ages at diagnosis.

  • What characteristics were used to generate these graphs?

    These graphs show the changes in the probability of causation at various doses for two scenarios. The red line represents a person whose cancer was diagnosed at 40 years of age, and the blue line represents a person who was diagnosed at 50 years of age. In addition, the following parameters were used in the generation of these graphs:

    • Male (except in the case of breast or ovarian cancer);
    • One acute exposure to high energy (i.e. >250 keV) photons;
    • The latency period (the time from the first occupational exposure to radiation to the time when the cancer was diagnosed) was 20 years for most of the solid cancers, but was 10 years for leukemia, bone or thyroid cancer;
    • In case of lung cancer, the smoking history.

  • What limitations do these graphs have?

    As described above, these graphs depict the probability of causation for a specific scenario. Because of this, they can not be used to interpret the outcome of a specific case.

Top of Page

New Procedure for Resolving Cases Close to 50% Probability of Causation


New procedure for resolving cases in which the upper 99th percentile credibility limit of probability of causation is equal to or greater than 45% but less than 52% using the default simulation sample size of 2000 and default random number seed of "99"

(Effective June 6, 2006)

Previously, each case with an initial probability of causation (PC) value falling between 45% and 50% at the upper 99th percentile credibility limit (C.L.) was processed by increasing the simulation sample size to 10,000, choosing a new random number seed, and rerunning the case in NIOSH-IREP. The resulting upper 99% C.L. of PC obtained with a sample size of 10,000 determined the case outcome, supplanting the initial PC value that had been obtained with a sample size of 2000. This procedure was adopted in order to provide better statistical precision for cases approaching the compensation threshold of 50%.

To achieve even greater statistical precision for cases close to the compensation threshold, the following new procedure was adopted on June 6, 2006 and replaces the procedure described above.

For cases in which the initial PC is equal to or greater than 45% but less than 52% using the default sample size of 2000:

  1. The simulation sample size will be increased to 10,000.
  2. 30 additional IREP runs will be performed, using a new random number seed for each run.
  3. The average value (arithmetic mean) of the upper 99% C.L. of PC of the 30 runs will determine the case outcome.
  4. For cases with more than one primary cancer in which the initial PC calculated from the "multiple primary" equation is equal to or greater than 45% but less than 52%, 30 runs will be performed for each primary cancer per steps 1 and 2 above. The arithmetic mean of the upper 99% C.L. of PC of the 30 runs for each cancer will then be entered into the multiple primary equation. The newly calculated PC, based upon the arithmetic mean PC value of each cancer as entered into the multiple primary equation, will determine the case outcome.

The NIOSH-IREP User's Guide is currently being revised to reflect this procedural change.

Top of Page

Changes to the NIOSH-IREP Lung Cancer Risk Model

Top of Page

Program Evaluation Reports (PERs) and Program Evaluation Plans (PEPs)

NIOSH is committed to applying the best available science in dose reconstructions. In keeping with this commitment, completed cases with probabilities of causation less than 50% are reviewed as relevant new information becomes available. The results of these reviews are described in a Program Evaluation Report (PER). The PER details the effect, if any, of the new information on the completed dose reconstruction. If it appears that the new information may result in an increase in dose for a completed dose reconstruction with a probability of causation of less than 50%, NIOSH is committed to working with the Department of Labor to reopen and rework the dose reconstruction, as appropriate. A Program Evaluation Plan (PEP) describes plans for evaluating specific program details or issues.

  • PER 16: Implementation of IREP Procedure for Claims near 50% Probability of Causation
    this document in PDF PDF 132 KB (4 pages)

    Document Number: OCAS-PER-0016 Rev-00

    About this Document: New document to evaluate the effect of implementing a new IREP procedure on previously completed claims.

    Approved: September 25, 2007

    Summary: A total of 109 previously non-compensable claims with PC values of 45% or greater were evaluated. The average PC value remained below the 50% compensation threshold for each of the 109 claims. An itemized list of claims was provided to DOL containing the final evaluation result for each of the 109 claims.


  • Program Evaluation Plan 8: Modification of NIOSH-IREP Lung Cancer Risk Model: Impact of "Combined" Lung Model on Non-Compensable Lung Cancer Claims
    this document in PDF PDF 132 KB (5 pages)

    Document Number: OCAS-PEP-008 Rev-00

    About this Document: New document to evaluate the modification of the NIOSH-IREP lung cancer model on previously competed cases.

    Approved: December 7, 2006

  • Program Evaluation Report 9: Target Organs for Lymphoma
    this document in PDF PDF 17 KB (2 pages)

    Document Number: OCAS-PER-009 Rev-00

    About this Document: New document to change target organs for lymphoma.

    Approved: March 8, 2007

    Summary: In February, 2006, OCAS determined that the internal and external dosimetry target organs used for several forms of lymphoma should be changed. The detailed rationale for this decision is described in OCAS-TIB-012. The change resulted from a detailed investigation by OCAS of the etiology of lymphoma.

Additional PERs and PEPs have been developed on various topics and/or sites. To view all PERs and PEPs that have been developed, please refer to the Program Evaluation Reports (PERs) and Program Evaluation Plans (PEPs) page.

Top of Page

Submitting Comments on NIOSH-IREP

The public may comment on NIOSH-IREP at any time. Comments can be sent electronically by e-mail to dcas@cdc.gov or ocas@cdc.gov. The preferred formats for electronic documents sent by e-mail are Word or WordPerfect. Comments can be mailed to:

NIOSH-IREP Comments
National Institute for Occupational Safety and Health
Division of Compensation Analysis and Support
1090 Tusculum Avenue
Mailstop C-45
Cincinnati, Ohio 45226

Top of Page

Subject Matter Expert Review of NIOSH-IREP

Top of Page

Other Related Materials

  • NIOSH-IREP User's Guide Version 5.7 (older version)
    (January 24, 2013)
    this document in PDF PDF 632 KB (22 pages)

    NIOSH-IREP was upgraded to v.5.7 on January 24, 2013. Version 5.7 features the addition of the CLL cancer risk model. The following additions were made:

    1. Added Chronic Lymphocytic Leukemia Risk Model: NIOSH reviewed the current literature and epidemiological data on the relationship between radiation and Chronic Lymphocytic Leukemia (CLL). Based on this review, NIOSH proposed that CLL be considered as a radiogenic cancer under the Energy Employees Occupational Illness Compensation Program Act of 2000 (EEOICPA). A risk model was developed to estimate Probability of Causation. The newly-developed risk model passed the review process and is now incorporated in NIOSH-IREP. More on this topic can be found on the NIOSH Docket page POC - Nonradiogenic Cancer Reconsideration.

      More detailed information about the review, synthesis, and application of information on the human lymphatic system to radiation dosimetry for CLL can be found in the document below:

    2. Added 3-Parameter Lognormal Distribution Option: Dose reconstructions have identified scenarios where a claimant's dose is best represented by a 3-parameter lognormal distribution. The first 2 parameters remain unchanged (geometric mean and geometric standard deviation). Users now have the ability to enter a 3rd parameter (location) to describe a lognormal distribution in the dose input table. The location parameter is sometimes called a "shift" parameter.

    3. Added Weibull Distribution Option: Dose reconstructions have identified scenarios where a claimant's dose is best represented by a Weibull distribution. Users now have the ability to select a Weibull distribution in the dose input table, described by 3 parameters. Enter "Shape" for Parameter 1, "Scale" for Parameter 2, and "Location" for Parameter 3 (optional).

  • NIOSH-IREP Version 5.6 Upgrade (older version)
    (September 2009)
    this document in PDF PDF 1 MB (22 pages)

    NIOSH-IREP was upgraded to v.5.6 on September 21, 2009. Version 5.6 features four changes, from which the first three are based on the findings in the Verification of the NIOSH-IREP Computer Code Version 5.5.3 Report.

    • Corrected Acute Lymphocytic Leukemia Algorithm: During recent quality control verification calculations, it was identified that NIOSH-IREP contained an incorrect algorithm for a specific set of input parameters used when processing acute lymphocytic leukemia claims. For all types of leukemia (including acute lymphocytic leukemia), in the case of acute exposure to low-LET radiation, the dose response obtained from the epidemiological data is linear-quadratic. Therefore, the ERR should be a function of [dose*(1+dose)]. In versions of NIOSH-IREP prior to v.5.6, the ERR for acute lymphocytic leukemia was programmed to depend only on dose instead of using the linear-quadratic algorithm. This modification has the potential to slightly increase the PC results for acute lymphocytic leukemia claims, if the claim included acute exposures to low-LET radiation.

    • Corrected Age Dependency for Selected Cancers: The recent quality control verification calculations identified a small difference between the NIOSH-IREP code and its documentation. The difference occurred in an algorithm that models the uncertainty in the adjustment factor describing the dependency of risk on age at exposure and attained age for cancer types included in Group 2. The NIOSH-IREP v.5.6 code has been modified to match the documentation. The PC values estimated for Group 2 cancers using NIOSH-IREP v.5.6 are identical to the results obtained from previous versions of NIOSH-IREP for any cancer diagnosed at ages 50 or older, and for any radiation exposures that occurred at ages 30 or older. However, this modification has the potential of slightly reducing the uncertainty in the estimated PC, and as a consequence to slightly decrease the PC results, for Group 2 cancer types, diagnosed at ages less than 50, and with exposures at ages less than 30.

    • Corrected Age Dependency for NIH Lung Model: The programming of the algorithm that describes the uncertainty in the adjustment factor for the dependency of risk on age at exposure and attained age for the NIH lung model was different from the algorithm given in the documentation of the code. In versions of NIOSH-IREP prior to v.5.6, there were two signs (+/-) that were reversed in an algorithm for males. This modification will cause no change in PC estimates for males diagnosed with lung cancer and with exposures occurring at ages greater than 30, for males diagnosed with lung cancer at age 50 or greater, and for females with lung cancer. However, this modification has the potential to slightly increase or decrease the PC results for males with exposures occurring at ages less than 30 and a diagnosed lung cancer at age less than 50.

    • Multiple Primary Cancers Link on Initial Screen: A button was added to the initial login screen on NIOSH-IREP to allow a user to directly access the calculation that estimates the PC from multiple primary cancers. In versions of NIOSH-IREP prior to v.5.6, the link to the multiple primary cancer calculation was located at the bottom of the main input screen.

    Verification of the NIOSH-IREP Computer Code Version 5.5.3 Report
    (July 2009)
    this document in PDF PDF 5 MB (512 pages)

    This report presents the results of a formal verification effort organized to ensure that the most current version of NIOSH-IREP software (version 5.5.3) calculates risk and probability of causation (PC) according to the methodology agreed upon by NCI and NIOSH. This verification process was performed by individuals of SENES Oak Ridge, Inc. who were not involved in the initial development of the code. It is important to note that this effort has not attempted to "validate" or question the models and procedures developed by NCI and NIOSH; this effort "verifies" that each part of the NIOSH-IREP code operates according to its intended use described in its technical documentation.

  • NIOSH-IREP Version 5.5.1 Upgrade
    (May 16, 2006)

    NIOSH-IREP v.5.5.1, introduced on May 16, 2006, displays the name of the uploaded template file on the summary results page. In addition, v5.5.1 incorporates memory and speed enhancements which allow a larger number of exposures for a given case. Probability of causation (PC) results from Version 5.5.1 are identical to those calculated using Version 5.5, the previous version of NIOSH-IREP. See below for more details:

    • Filename displayed on summary page: Based on a recommendation by a Department of Labor claims examiner, the name of the Excel template file uploaded for a given IREP run is now displayed on the IREP Summary (PC results) page. This makes it easier to identify printed summary pages for claims with multiple cancers.

    • Memory and speed improvements: Due to the need to adjudicate claims with large numbers of exposures, the underlying NIOSH-IREP source code has been streamlined for efficiency. As a result, NIOSH-IREP v5.5.1 requires 30-40% less memory than v5.5 on the server that houses it and the processing speed has been increased by 10-20%. These modifications have absolutely no effect on PC results. The PC results for a case processed using NIOSH-IREP v5.5.1 are exactly the same as if the case were processed using NIOSH-IREP v5.5.


  • Draft: 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 (OCAS-PER-008)
    Contract No. 200-2009-28555
    SCA-TR-PR2010-0008, Revision 0
    December 2010
    this document in PDF PDF 414 KB (26 pages)


  • Final: Report to the Senate Appropriations Committee on The Radiogenicity of Specific Cancers Under the Energy Employees Occupational Illness Compensation Program Act of 2000 as Amended
    (December 2009)
    this document in PDF PDF 53 KB (10 pages)

    Note: This document was submitted to Congress on December 17, 2009.


  • Report to the Senate Appropriations Committee on the Radiogenicity of Specific Cancers under the Energy Employees Occupational Illness Compensation Program Act of 2000 as Amended
    (June 2007)
    this document in PDF PDF 30 KB (11 pages)


  • CIRRPC
    Science Panel Report No. 6
    Use of Probability of Causation by the Veterans Administration in the Adjudication of Claims of Injury Due to Exposure to Ionizing Radiation

    Complete document
    this document in PDF PDF 1.71 MB (43 pages)

    Pages i-15

    this document in PDF PDF 1.05 MB (21 pages)

    Pages 16-B9
    this document in PDF PDF 682 KB (22 pages)


  • Report of the NCI-CDC Working Group to Revise the 1985 NIH Radioepidemiological Tables
    External Link: http://dceg.cancer.gov/files/NIH_No_03-5387.pdf
    NIH Publication No. 03-5387

    This updated report, published in September 2003, uses epidemiological dose-response data and uncertainty analyses in providing a scientific basis for quantifying radiation-related cancer risks. The tabular version is an interactive radio-epidemiological computer program known as "NIH-IREP" and corresponds to the report. NIH-IREP can be accessed online at http://www.irep.nci.nih.gov/.

    Both the Report and NIH-IREP may also be accessed on the National Cancer Institute's Interactive Radioepidemiological Computer Program Web page.

Top of Page

Page last updated: July 22, 2014
Page last reviewed: August 10, 2013
Content Source: National Institute for Occupational Safety and Health (NIOSH) Division of Compensation Analysis and Support