To determine probability of causation for a cancer case under the Act, the Department of Labor (DOL) uses a computer software application NIOSH has developed in collaboration with the National Cancer Institute, called NIOSH-IREP (Interactive RadioEpidemiological Program).

NIOSH-IREP was adapted from the National Institutes of Health’s (NIH) Interactive RadioEpidemiological Program (NIH-IREP) developed by the National Cancer Institute (NCI) to update the 1985 NIH Radioepidemiological Tables.

NIOSH-IREP 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 case depends on a number of important factors such as the dose estimates of past exposures and the type of cancer that has been diagnosed. NIOSH is responsible for maintaining and updating this software and the scientific elements (cancer risk models) that it uses.

Access and Use

Online Access

The NIOSH-IREP interactive software program can be found at: Data can be entered manually or by using a NIOSH-provided input file. Users also have the ability to calculate PC from multiple primary cancers.

User’s Guide

  • User’s Guide Version 5.9 [902 KB (22 pages)]
    (December 2020)
    Recently, an issue with the Acute Lymphocytic Leukemia cancer model was found, and it is now corrected in the IREP version v.5.9. Here is a complete description with all the changes that were made in NIOSH-IREP v.5.9:

    1. Fixed issue related to Acute Lymphocytic Leukemia claims
      A small issue was identified and fixed related to Acute Lymphocytic Leukemia claims involving exposures to neutrons or alpha particles. Claims evaluated using v.5.9 will result in slight changes in PC values, with a tendency towards larger PC values for claims involving exposures to neutrons and towards lower PC values for claims involving exposures to alpha particles.

    2. Improved Validation Checks
      This version includes additional validation checks on user input to provide friendly warnings or messages when invalid inputs are entered.

Example Input Files

Below are example input files that may be uploaded into NIOSH-IREP. The User’s Guide provides instructions for uploading input files. Summaries of the example files are also provided. 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 program.

Technical Documentation

Subject Matter Expert Review

Previous Versions

Information on previous updates to the NIOSH-IREP program can be found at

Submitting Comments

The public may comment on NIOSH-IREP at any time. Comments can be sent by e-mail to

Comments can be mailed to:

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

Frequently Asked Questions (FAQs)

More information on NIOSH-IREP can be found on the FAQs: NIOSH-Interactive RadioEpidemiological Program (NIOSH-IREP) page of our website.