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Model Report


Last Revision Date: 08/31/2009 View as PDF
General Information Back to Top
Model Abbreviated Name:

Model Extended Name:

Model Overview/Abstract:
The Unified Radon Relative Risk Model (UR3M) is a Windows program for PCs. It was developed to fill the need for a comprehensive approach to radon health risks and to allow users or their clients to make informed decisions with respect to radon. The model combines three radon sources, three exposure pathways, and two risk reduction methods to give a composite assessment of health risks, attainable risk reductions, and cost factors associated with risk reduction. Risks are presented both numerically and graphically, calculated for the general population according to environmental factors. Individuals may customize their risk estimate based on their smoking histories.

Version 2.0 contains a number of new functions dealing with Public Water Supply radon issues:

  • MCL and AMCL water risk differentials
  • AMCLs and Multimedia Mitigation (MMM)
  • Risk reduction equivalent to MCL treatment
  • Calculating the number of MMM houses for equivalent risk
The goal of UR3M is to communicate radon risks to the public more effectively than has been done in the past. It accomplishes this in two ways. First, through selection of the focus of the risk estimate to either the individual houses or to multiple house groups, including all significant risk parameters. Second, by presenting risks graphically as personalized bar graphs, much of the communication barrier between the scientific-technical community and the public can be overcome.

The health effects of radon were reevaluated by the Environmental Protection Agency and the National Academy of Sciences in 1999.

Model Technical Contact Information:
Stan Rydell, Ph.D.
U.S. EPA, Region 1
(617) 918-1637

The model was developed and is maintained by Stan Rydell.

Model Homepage: www.epa.gov/region01/eco/wrsdp.html

User Information Back to Top
Technical Requirements
Computer Hardware
PC with 64 MB / 128 MB virtual, 128 MB / 256 MB virtual, or better
Compatible Operating Systems
Windows 95, 98, NT, or later
Other Software Required to Run the Model
Visual Basic
Download Information
The model is publicly available from the U.S. EPA, Region 1.

The equations are available; but, source code is not.

Using the Model
Basic Model Inputs
Screening model with moderate input requirements.
User Support
User's Guide Available?
Documentation can be downloaded.

Provides: (1) an abstract or abstract equivalent in the introduction, (2) equations, equation solution methodologies, and related simplifying assumptions, and (3) example input/output files.

User Qualifications
The user needs only moderate level of technical education and/or modeling experience. The software was designed to be user friendly and to address potential limitations in a user's technical background.

Model Science Back to Top
Summary of Model Structure and Methods
The model uses mixed U.S. / S.I. units and flexible (user-defined) units.

Governing equations are solved numerically.

Model Evaluation
Code verification has been performed in U.S. EPA Region 1.

The model has been internally peer reviewed by the U.S. EPA Region 1, New England Radon Committee, New England Radiological Health Committee.

The model has been externally peer reviewed by experts outside of U.S. EPA Region 1.

Software Beta testing has been used for QA/QC.

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