User's Guide for the Interactive 

RadioEpidemiological Program

(NIOSH-IREP) 

Designed for use by the Department of Labor

in adjudicating claims under the Energy

Employees’ Occupational Illness

Compensation Program Act (EEOICPA) 

Version 5.9 

December 2020 

This User’s Guide was prepared by Oak Ridge Center for Risk Analysis under 

contract with NIOSH. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

User's Guide December 2020 

Interactive RadioEpidemiological Program (NIOSH-IREP) Page 2 

TABLE OF CONTENTS 

Page 

1.0 BACKGROUND .................................................................................................... 3 

2.0 INTRODUCTION................................................................................................... 4 

3.0 DETERMINING PROBABILITY OF CAUSATION ................................................ 5 

Step 1: Log onto NIOSH-IREP ........................................................................... 5 

Step 2: Start Program ......................................................................................... 6 

Step 3: Upload Claimant Input File .................................................................... 7 

Step 4: Perform Calculation................................ ................................................ 8 

Step 5: Print and Save Output Summary Report.............................................. 10 

4.0 MULTIPLE PRIMARY CANCERS....................................................................... 11 

5.0 TECHNICAL ASSISTANCE ................................ ................................ ................ 13 

6.0 INPUT FILE TEMPLATE..................................................................................... 13 

7.0 PROCEDURE FOR CLAIMS WITH A PROBABILITY OF CAUSATION 

EQUAL TO OR GREATER THAN 45% BUT LESS THAN 52%......................... 14 

8.0 GLOSSARY ........................................................................................................ 15 

9.0 DESCRIPTION OF EXAMPLE INPUT FILES..................................................... 20 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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1.0 BACKGROUND 

Under the Energy Employees’ Occupational Illness Compensation Program Act 

(EEOICPA), the National Institute for Occupational Safety and Health (NIOSH) is charged 

with the development of guidelines to determine whether a claimant’s cancer meets the 

criterion for causation by workplace exposure to ionizing radiation (i.e., a 50% or greater 

probability of causation). 

The basis for this determination, as specified in EEOICPA, is the set of 

radioepidemiological tables developed by a National Institutes of Health (NIH) working 

group in 1985. These radioepidemiological tables serve as a reference tool providing 

probability of causation (PC) estimates for individuals with cancer who were exposed to 

ionizing radiation. 

A major technological change to the 1985 radioepidemiological tables represents a 

scientific as well as a practical improvement: the development of a computer program for 

calculating probability of causation. This software program, named the Interactive 

RadioEpidemiological Program (IREP), allows the user to apply the National Cancer 

Institute’s (NCI) risk models directly to data about exposure for an individual employee. 

This makes it possible to calculate the probability of causation using better quantitative 

methods than could be incorporated into printed tables. In particular, IREP allows the user 

to take into account uncertainty concerning the information being used to estimate 

individualized exposure and to calculate the probability of causation. 

Accounting for uncertainty is important because it can have a large effect on the probability 

of causation estimates for a specific individual. The Department of Veterans Affairs (VA), 

in their application of the 1985 radioepidemiological tables, uses the value at the upper 99 

percent credibility limit of the probability of causation estimate. Similarly, as required by 

EEOICPA, the U.S. Department of Labor (DOL) uses the upper 99 percent credibility limit 

to determine whether the cancers of employees were caused by their radiation doses. 

This will help minimize the possibility of denying compensation to claimants under 

EEOICPA for those employees with cancers likely to have been caused by occupational 

radiation exposures. 

A version of IREP was developed to specifically address the workforce covered by 

EEOIPCA. This version, called NIOSH-IREP, is tailored to the risks and radiation 

exposures characteristic of nuclear weapons employees. NIOSH-IREP is used by DOL 

to calculate the probability of causation for each claim. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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2.0 INTRODUCTION 

The NIOSH-IREP computer code is a web-based program that estimates the probability 

that an employee’s cancer was caused by his or her individual radiation dose. Personal 

information (e.g., birth year, year of cancer diagnosis, gender) and exposure information 

(e.g., exposure year, dose) may be entered manually or through the use of an input file. 

For application by the U.S. Department of Labor (DOL), the input file option is used to 

preset all personal information, exposure information, and system variables. These input 

file(s) are created by NIOSH for each individual claim and transmitted to the appropriate 

DOL district office for processing. 

The purpose of this user’s guide is to provide DOL with a concise step-by-step guide to 

the use of NIOSH-IREP in processing energy employee compensation claims. 

A glossary containing definitions of radiation terms and other frequently used terms related 

to NIOSH-IREP is included in Section 8.0 of this user’s guide. Readers interested in a 

more thorough discussion of the science behind NIOSH-IREP are encouraged to review 

the Technical Documentation and similar documents posted on NIOSH’s Division of 

Compensation Analysis and Support (DCAS) web site at www.cdc.gov/niosh/ocas. 

A set of example input files have been prepared to be used in conjunction with this user’s 

guide to demonstrate the use of NIOSH-IREP. These input files may be downloaded from 

the DCAS website (http://www.cdc.gov/niosh/ocas/nioshirep.html). Section 9.0 describes 

the input files and provides pre-calculated solutions for each case. 
 

 

 

 

 

 

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3.0 DETERMINING PROBABILITY OF CAUSATION 

STEP 1: Log onto NIOSH-IREP 

NIOSH-IREP can be accessed through NIOSH’s Division of Compensation 

Analysis and Support (DCAS) web site at: 

https://www.cdc.gov/niosh/ocas/nioshirep.html 

Click the link under “Online Access” section 

Figure 1. NIOSH web page containing the link to NIOSH-IREP Software 
 

 

 

 

 

 

 

 

 

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STEP 2: Start Program 

On the initial log-in screen (Figure 2), select the option “To begin by using a NIOSHprovided input file” to start NIOSH-IREP. 

Figure 2. Initial log-in screen of the NIOSH-IREP computer program 

NOTE: This screen allows a user to enter personal information (e.g., birth year, year of 

cancer diagnosis, gender) and exposure information (e.g., exposure year, dose) manually 

(click on top button) or through the use of an input file (middle button). The bottom button 

allows the user to access the multiple primary cancers calculator. 

As specified by 42 CFR Part 81 (Guidelines for Determining the Probability of Causation), 

DOL uses the data input file option to preset all personal information, exposure 

information, and system variables. This input file is created by NIOSH, as specified by 42 

CFR Part 82 (Methods for Radiation Dose Reconstruction) and transmitted to the 

appropriate DOL District Office for processing. 
 

 

 

 

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STEP 3: Upload Claimant Input File 

A. The first step of uploading a claimant input file is to identify where the file resides. 

Click the “Browse” button on the screen shown in Figure 3. 

B. Locate the input file in the “Choose file” dialog box (Figure 4). Once the input file 

is selected, click the “Open” button to upload it. 

C. The file and path will appear in the window beside the “Browse” button (Figure 5). 

Click “Upload File.” 

D. A status message will appear, including the name of the uploaded file (Figure 6). 

Click “Continue” to populate the fields of the main input screen (as shown in Figure 

7, next page) with the values saved in the input file. 

Figure 3. “Upload Saved File” screen Figure 4. “Choose file” dialog box 

Figure 5. File appears in window Figure 6. Success! 
 

 

 

 

 

 

 

 

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STEP 4: Perform Calculation 

To calculate probability of causation, click the “Generate Results” button on the main 

input screen (Figure 7). 

Figure 7. Main input screen 

The claimant’s information will be sent to the server that hosts NIOSH-IREP. The 

calculation will be performed in real-time, and the results will be returned in the form of 

a summary table suitable for printing and saving (Figure 8, next page). 
 

 

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Figure 8. NIOSH-IREP Probability of Causation Results (Summary Report, truncated) 
 

 

 

 

 

 

 

 

 

 

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STEP 5: Print and Save Output Summary Report 

To Print: 

When the calculation is completed, the output summary report can be printed by using 

the “Print” command in the “File” menu. 

To Save: 

An electronic copy of the output summary report can be saved using the “Save As” 

command in the “File” menu. 

In the “Save Web Page” dialog window (Figure 9), name the file and select the location 

where the file is to be saved. Select “Web Page, HTML only” from the “Save as type” 

pull-down menu. Click “Save.” 

Figure 9. “Save Web Page” dialog window 

Reminder: When saving the Summary Report, select “Web Page, HTML only” from 

the “Save as type” pull-down menu. (Do not use the default choice of “Web Page, 

complete.”) 
 

 

 

 

 

 

 

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4.0 Multiple Primary Cancers 

If a claimant is diagnosed with more than one primary cancer, NIOSH will provide an input 

file for each primary cancer. NIOSH-IREP should be run with each of the input files. Enter 

the results from each run into the “Multiple Primary Cancers” calculator. The Multiple 

Primary Cancers calculator is accessible from the initial log-in screen (Figure 10), by 

clicking the button located at the bottom of the main input screen (Figure 7), or by using 

the link at the bottom of the summary page. 

Figure 10. Initial Log-in Screen showing the “Multiple Primary Cancers” button 
 

 

 

 

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Multiple primary cancers (continued) 

Follow the online instructions to estimate a claimant’s total PC from two or more primary 

cancers (Figure 11). 

[NOTE: As of June 2014, the capabilities of NIOSH-IREP were expanded to allow for the 

estimation of total PC from up to 240 primary cancers (previous limit was 120 primary 

cancers).] 

Figure 11. Multiple Primary Cancers screen 
 

 

 

 

 

 

 

 

 

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5.0 TECHNICAL ASSISTANCE 

Technical information about NIOSH-IREP may be obtained, and comments about NIOSHIREP may be made, by contacting the NIOSH Division of Compensation Analysis and 

Support (DCAS) by e-mail at dcas@cdc.gov, or by mail at: 

National Institute for Occupational Safety and Health 

Division of Compensation Analysis and Support 

Robert A. Taft Laboratories, MS-C45 

1090 Tusculum Avenue 

Cincinnati, OH 45226 

DOL staff requiring immediate technical assistance may call the DCAS office at 

(513) 533-6800. 

6.0 INPUT FILE TEMPLATE 

The input files produced by NIOSH are in Microsoft Excel format. These input files should 

not be modified by DOL. A screenshot of an example input file has been provided (Figure 

12) for informational purposes. 

Figure 12. Screenshot of an example input file 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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7.0 PROCEDURE FOR CLAIMS WITH A PROBABILITY OF CAUSATION 

EQUAL TO OR GREATER THAN 45% BUT LESS THAN 52% 

New procedure (adopted June 6, 2006) for resolving claims 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” 

Previously, each claim 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 claim in NIOSH-IREP. The resulting upper 99% C.L. of PC obtained 

with a sample size of 10,000 determined the claim outcome, supplanting the initial PC 

value that had been obtained with a sample size of 2,000. This procedure was adopted 

in order to provide better statistical precision for claims approaching the compensation 

threshold of 50%. 

To achieve even greater statistical precision for claims close to the compensation 

threshold, the following procedure was adopted on June 6, 2006 and replaced the 

procedure described above. 

For claims in which the initial PC is equal to or greater than 45% but less than 52% using 

the default sample size of 2,000: 

(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 claim outcome. 

(4) For claims 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 claim outcome. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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8.0 GLOSSARY1 

Absorbed dose: The energy deposited by ionizing radiation per unit mass of tissue 

irradiated. It can be expressed in units of gray (Gy) or rad, where 1 Gy = 100 rad. 

Activity: The rate of transformation (or disintegration or decay) of a radioactive material. 

It can be expressed in units of becquerel (Bq) or curie (Ci). 

Acute dose: A radiation dose received by a person over a short period of time (less than 

one day.) For purposes of cancer risk modeling, it has been suggested that a dose 

can be considered acute if it was delivered at a rate greater than 0.006 Gy per hour 

averaged over the first few hours. 

Alpha particle: A particle emitted from a decay of certain heavy radionuclides. It has a 

short range and can be stopped by a sheet of paper or the outer dead layer of skin. 

Alpha particles constitute a health hazard only when alpha-emitting radionuclides 

are deposited in tissues following ingestion or inhalation. 

Background radiation: Radiation emitted by natural sources such as cosmic radiation or 

radionuclides occurring naturally in soil, food, water or air. 

Baseline cancer risk: The risk of cancer in the general population from causes other than 

exposure to the investigated agent (for example, the source of radiation.) 

Becquerel (Bq): The unit of activity equal to one disintegration per second. 

Beta particle: A particle emitted from a decay of certain radionuclides. It has a short 

range but can penetrate the dead layer of skin to produce a skin dose. 

Carcinogen: Any substance or agent that can cause cancer. 

Centi-sievert (cSv): An equivalent dose equal to 0.01 Sv or 1 rem. 

Chronic dose: A radiation dose received by a person over a long period of time (more 

than one day.) For purposes of cancer risk modeling, it has been suggested that a 

dose can be considered chronic if it was delivered at a rate lower than 0.006 Gy per 

hour for more than one day. 

Cohort: A group of individuals sharing one or more characteristics. 

Confidence interval (CI): A range of values around a mean, proportion, or rate that 

serves as an estimate of uncertainty. The upper and lower values of a confidence 

interval are called the confidence limits. 

Confounder (or confounding variable): In an epidemiologic study, a factor that is 

associated with both the exposure of interest (e.g., radiation) and the outcome of 

interest (e.g., cancer), and that distorts or masks the true effect of the exposure. 

Covered employee: A current or former employee of DOE, a DOE contractor or 

subcontractor, or an atomic weapons employer, and for whom DOL has directed 

DCAS to perform a dose reconstruction. 

Curie (Ci): A measure of the amount of radioactivity in a material. One curie is equal to 

37 billion disintegrations per second. 

1 Words appearing in italicized text are also defined in the glossary. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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DCAS: The Division of Compensation Analysis and Support, an Office of NIOSH located 

in Cincinnati and created to fulfill NIOSH’s responsibilities under EEOICPA. 

Dose (or radiation dose): A general term representing either absorbed dose or 

equivalent dose. 

Dose and dose-rate effectiveness factor (DDREF): A mathematical factor that takes 

into account that the response per unit dose at low doses and low dose rates may 

be different from the response per unit dose at high doses and high dose rates. 

Dose reconstruction (DR): Research and analysis leading to a quantitative estimate of 

radiation exposure, particularly when radiation monitoring data are unavailable, 

incomplete, or unreliable. 

Dose-response relationship: A relationship in which a change in the amount, intensity, 

or duration of an exposure is associated with either an increase or decrease in risk 

of a specified health outcome. 

EEOICPA: The Energy Employees Occupational Illness Compensation Program Act of 

2000, Public Law 106-398, as amended. 

Electron volt (eV): The customary unit of energy for all ionizing radiations. 

Epidemiology: The study of factors that affect health and disease in populations. 

Equivalent dose: A measure of biological damage caused by exposure to radiation, 

expressed in units of rem or sievert (Sv), where 1 Sv = 100 rem. 

Excess relative risk (ERR): The risk due to exposure to radiation in excess of the 

baseline risk, divided by the baseline risk. ERR is the same as the relative risk (RR) 

minus one. 

External dose: The dose from radiation sources located outside the body. 

Gamma rays (or gamma radiation): Electromagnetic radiation emitted from a decay of 

certain radionuclides. It can be very penetrating, producing a radiation dose 

throughout the whole body. 

Gray (Gy): The special name for the SI unit of absorbed dose. 1 Gy = 100 rad. 

Health physics: The science of radiation protection to reduce or prevent radiation 

exposure. Health physicists at DCAS specialize in quantifying past radiation 

exposures (i.e., dose reconstruction) in order to evaluate their health effects. 

Healthy worker effect: A phenomenon in which fewer deaths or illnesses (cancers, for 

example) are observed among workers in a given industry compared with the 

general population, even though the workers under study may be more exposed to 

hazardous substances (ionizing radiation, for example) than the general population. 

This counterintuitive effect is often attributed, in part, to the assumption that 

chronically ill or disabled persons are less likely to be employed than healthier 

persons. Thus, a cohort of workers – absent that less robust segment of the 

population – may be more resistant to disease than the population as a whole. 

Internal dose: The dose from radioactive materials that have been absorbed, ingested, 

or inhaled into the body. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Inverse dose-rate effect: A phenomenon in which a given dose delivered chronically or 

in multiple fractions results in a greater biological response than the same dose 

delivered acutely. 

Ionizing radiation: Particles or rays emitted from radioactive materials. If ionization is 

produced in a cell, the ions may damage the cell and the affected cells may become 

cancerous. 

Milli-sievert (mSv): An equivalent dose equal to 0.001 sievert (Sv). 

Missed dose: A radiation dose that was received by an individual, but that was not 

detected by monitory methods nor recorded. 

Monte Carlo simulation: A computerized method for estimating the statistical uncertainty 

of a risk model. Repeated samples are taken from special probability distribution 

functions and the probability of causation (PC) is calculated for each set of samples. 

The upper 99th percentile of the distribution of estimated PC values (upper 99 percent 

credibility limit) is used to determine eligibility for compensation under EEOICPA. 

Neutron: An uncharged particle of radiation produced from certain nuclear reactions. It 

can be very penetrating, producing a radiation dose throughout the whole body. 

NIOSH: The National Institute for Occupational Safety and Health, part of the Centers for 

Disease Control and Prevention, United States Department of Health and Human 

Services. 

Odds ratio (OR): The ratio of the odds of disease among the exposed compared with the 

odds of disease among the unexposed. Under certain conditions, the odds ratio 

may be used as an estimate of the relative risk. 

Organ dose: A general term representing either absorbed dose or equivalent dose 

received by a particular organ or tissue. 

Photon: Electromagnetic radiation emitted from one of several possible sources. Photons 

originating from radioactive decay are called gammas or gamma rays. 

Primary cancer: A cancer defined by the original organ site at which the cancer occurred, 

prior to any spread (metastasis) to other sites in the body. 

Probability of causation (PC or PoC): The probability or likelihood that a cancer was 

caused by radiation exposure incurred by a covered employee while in the 

performance of duty. A PC of 50% or greater means that the claimant’s cancer was, 

as least as likely as not, induced by occupational radiation exposure. 

Rad: A unit of absorbed dose. 100 rad equals one gray (1 Gy). 

Radiation dose: See dose. 

Radiation effectiveness factor (REF): A mathematical factor, similar to relative biological 

effectiveness (RBE), used to account for the fact that different types of radiation are 

more effective at producing an outcome (such as cancer) than others. 

Radioactivity: The process or characteristic of an unstable atomic nucleus to 

spontaneously transform with the emission of energy in the form of radiation, such 

as alpha particles, beta particles, and photons. The term may also refer to 

radioactive materials. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Radioepidemiological Tables: Tables that allow computation of the probability of 

causation (PC) for various cancers associated with a defined exposure to radiation, 

after accounting for factors such as gender, age at exposure, age at diagnosis, and 

time since exposure (TSE). 

Radiogenic: Capable of being caused by exposure to ionizing radiation. Most types of 

cancers are considered to be radiogenic. 

Radon: A radioactive noble-gas element. Radon constitutes a health hazard, primarily to 

the lungs, when it is released into the air and its decay products are inhaled. 

Random seed number: The first number selected in a sequence of random numbers. A 

given seed value will produce the same sequence of random numbers every time a 

Monte Carlo simulation is run in NIOSH-IREP using the same simulation sample 

size. 

Relative biological effectiveness (RBE): A mathematical factor used to account for the 

fact that different types of radiation are more effective at producing an outcome (such 

as cancer) than others. 

Relative risk (RR): The ratio of disease incidence (or mortality) in an exposed population 

to that in an unexposed population. A relative risk of “1” means there is no 

association between exposure and disease. 

Rem: A unit of measure for expressing equivalent dose. One rem is equal to 1 centisievert (cSv) or 0.01 sievert (Sv). 

Risk coefficient: A general term referring to the coefficient of the dose-response 

relationship. In particular, if the dose-response is linear, the risk coefficient is the 

slope of the dose-response, and it represents the risk of cancer per unit dose 

received by the exposed individual. 

Risk model: A mathematical model based on the dose-response relationship determined 

for a given cancer type, used to estimate the probability of causation (PC) using 

information on radiation dose and personal data. 

SEC: Special Exposure Cohort. 

Secondary cancer: A cancer that has spread (metastasized) from its site of origin (the 

primary site) to another part of the body. 

SI: The International System of Units 

Sievert (Sv): A unit of measure for expressing equivalent dose. One sievert (1 Sv) is 

equal to 100 rem. 

Simulation sample size: The number of Monte Carlo simulations used in each NIOSHIREP run. The default simulation sample size in NIOSH-IREP is 2000. 

Threshold dose: Radiation dose below which there is no measurable biological effect. 

Time since exposure (TSE): The number of years between radiation exposure and 

diagnosis of cancer. 

Uncertainty: A term used to describe the lack of precision and accuracy of a given 

estimate, the extent of which depends upon the amount and quality of the evidence 

or data available. 
 

 

 

 

 

 

 

 

 

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Uncertainty distribution: A range of discrete or continuous values arrayed to 

encompass, with high confidence, the true but unknown values of a given quantity 

or parameter. 

Upper 99 percent credibility limit: The 99th percentile of the range of values in an 

uncertainty distribution. The uncertainty distribution of the probability of causation 

(PC) is first estimated, and the upper 99th percentile of this distribution is compared 

to the decision criterion (a PC of 50%) to determine eligibility for compensation. 

Working Level: A unit of measure describing the level of exposure to radioactive radon. 

Working Level Month (WLM): A unit of measure describing a cumulative exposure to 

one working level of radon for one working month (170 hours.) 

X rays: A type of electromagnetic radiation (photon) similar to gamma radiation but 

generally less energetic. 
 

 

 

 

 

 

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9.0 DESCRIPTION OF EXAMPLE INPUT FILES 

Example input files are available online to aid Department of Labor (DOL) staff in learning to use 

NIOSH-IREP. A description of each file is included below. The simulation sample size has been 

set to 2,000 and the random seed value has been set to 99 for all example input files. 

Example 1 is included to illustrate how PC is affected by the claimant’s age at the time of exposure. 

Example 1a 

Filename: irepug1a.xls 

Gender: Female 

Age at exposure: 20 

Age at diagnosis: 50 

Cancer type: Liver 

No. of exposures: 1 

Exposure rate: chronic 

Radiation type: high-energy gamma rays (photons; E=30-250 keV) 

Dose: 10 cSv (constant) 

Example 1a solution 

Probability of 

Causation (%) 

1st 1.68 

5th

Percentile 

3.08 

50th 13.90 

95th 42.20 

99th 55.61 

Example 1b 

Filename: irepug1b.xls 

Gender: Female 

Age at exposure: 40 

Age at diagnosis: 50 

Cancer type: Liver 

No. of exposures: 1 

Exposure rate: chronic 

Radiation type: high-energy gamma rays (photons; E=30-250 keV) 

Dose: 10 cSv (constant) 

Example 1b solution 

Probability of 

Percentile Causation (%) 

1st 0.94 

5th 1.68 

50th 8.17 

95th 28.95 

99th 41.06 
 

 

 

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Example 2 is included to illustrate how PC is affected by smoking history. 

Example 2a 

Filename: irepug2a.xls 

Gender: Male 

Age at exposure: 20 

Age at diagnosis: 50 

Cancer type: 

Smoking history: Never smoked 

Lung 

No. of exposures: 1 

Exposure rate: chronic 

Radiation type: high-energy gamma rays (photons; E=30-250 keV) 

Dose: Lognormal (geometric mean=15 cSv; geometric sd=2.0) 

Example 2a solution 

Probability of 

Percentile Causation (%) 

1st 0.62 

5th 1.48 

50th 9.25 

95th 40.99 

99th 58.94 

Filename: 

Example 2b 

irepug2b.xls 

Gender: Male 

Age at exposure: 20 

Age at diagnosis: 50 

Cancer type: Lung 

Smoking history: Smoker (20-39 cigarettes/day) 

No. of exposures: 1 

Exposure rate: chronic 

Radiation type: high-energy gamma rays (photons; E=30-250 keV) 

Dose: Lognormal (geometric mean=15 cSv; geometric sd=2.0) 

Example 2b solution 

Probability of 

Percentile Causation (%) 

1st 0.08 

5th 0.16 

50th 1.89 

95th 21.91 

99th 40.77 
 

 

 

 

 

 

 

 

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Example 3 is included to show how multiple exposures are handled in NIOSH-IREP. 

Example 3 

Filename: irepug3.xls 

Gender: Male 

Age at exposure: 25, 26, 27, 28, 29 

Age at diagnosis: 60 

Cancer type: Colon 

No. of exposures: 5 

Exposure rate: chronic 

Radiation type: high-energy gamma rays (photons; E=30-250 keV) 

Dose: Lognormal (geometric mean=5 cSv, geometric sd=1.7) 

Example 3 solution 

Probability of 

Percentile Causation (%) 

1st 0.93 

5th 3.38 

50th 13.85 

95th 39.98 

99th 56.02 

Example 4 demonstrates a calculation for a claimant with 3 radon and 3 other radiation exposures. 

Example 4 

Filename: irepug4.xls 

Gender: Male 

Age at exposure: 20, 21, 22 

Age at diagnosis: 50 

Cancer type: Lung 

Smoking history: Never smoked 

No. of exposures: 3 

Exposure rate: chronic 

Radiation type: high-energy gamma rays (photons; E>250 keV) 

Dose: Triangular (min=2, mode=4, max=8) 

Radon exposure: Lognormal (geometric mean=0.4 WLM, geometric sd=2) 

Example 4 solution 

Probability of 

Percentile Causation (%) 

1st 4.38 

5th 6.37 

50th 15.87 

95th 41.76 

99th 56.80