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Model Report

Ecposure Related Dose Estimating Model

Last Revision Date: 10/08/2009 View as PDF
General Information Back to Top
Model Abbreviated Name:

Model Extended Name:

Ecposure Related Dose Estimating Model
Model Overview/Abstract:
ERDEM is a physiologically based pharmacokinetic (PBPK) modeling system consisting of a general model and an associated front end. An actual model is defined when the user prepares an input command file. Such a command file defines the chemicals, compartments and processes that are to be used. A graphical-user-interface (GUI) Front End is utilized to prepare the input data.
Model Technical Contact Information:
Agency Contact: Rogelio Tornero-Valez
Human Exposure and Atmospheric Sciences Division
National Exposure Research Lab
Office of Rearch and Development

Cecilia Tan
Human Exposure and Atmospheric Sciences Division
National Exposure Research Lab
Office of Rearch and Development

Model Homepage: http://www.epa.gov/heasd/products/erdem/erdem.htm

User Information Back to Top
Technical Requirements
Computer Hardware
Minimum 700 MHz chip with at least 512 Megabytes of RAM
Compatible Operating Systems
Microsoft Windows 98, NT 4.0, 2000, or XP
Other Software Required to Run the Model
A User's Guide, Video Tutorial, Extensive Help, and Release Notes are supplied with the ERDEM system.
Download Information
The download of the ERDEM model is in preparation. The ERDEM GUI Front End for the latest model is in development. The ERDEM 3.6a beta may be made available for review. It does not contain enzyme inhibition and certain dermal exposure types.

See the model's home page for download information.

Using the Model
Basic Model Inputs
The inputs consist of the user's choice of lung, GI, or dermal model, and the other compartments. Then the user chooses the processes to model, such as binding, elimination, metabolism, and enzyme inhibition (if included). The physiological parameters such as body weight and compartment weight, cardiac output, breathing rate and blood flow to each compartment are input for the chosen species. The partition coefficients for the flow of chemical throughout the blood and compartments are then input. The metabolism, binding, elimination and inhibition parameters are input.
Basic Model Outputs
These consist of time profiles of amount, concentration, Area Under the Curve and other outputs as desired by the user. Plots can be generated by the model, and time profiles can be printed for inserting into other plotting packages.
User Support
User's Guide Available?

Model Science Back to Top
Problem Identification
Develop a deterministic physiologically based pharmacokinetic (PBPK) modeling system to be used by scientists to build models that take exposure to multiple xenobiotics and determine their dose and that of their metabolites to various organ systems, as well as their elimination and effect on the species enzyme system (pharmacodynamic effects). A front end will be developed to provide the scientist with a well organized approach to preparing the complex inputs to such a system. This front end will provide a mechanism for the user to utilize exposure time profiles from other exposure models as well as measuring instruments. It will provide an aid to the user in preparing and running multiple runs for sensitivity analysis, Monte Carlo and Bayesian Markov Chain analysis. The user determines the chemicals and metabolites to model, the compartments (such as liver, kidney, etc.), the type of lung and GI and dermal models to use as well as which exposures and their definition.
Summary of Model Structure and Methods
The compartments in the modeling system are developed based on the work of toxicologists, modelers, physiologists, and other experts in the transport of chemicals in mammalian systems, such as Dr. Jerry Blancato, Dr Jeff Fisher, Dr. Mel Anderson, Dr. Richard Corley, Dr. Harvey Clewell, Dr. Kanan Krishnan, and many others (please see references). The compartments are connected to the arterial and venous blood system which is connected to the lung , the liver is connected to the GI tract model. The system is mostly flow limited with dispersion modeled in more detailed representations of certain models.

The equations and algorithms are provided in the EPA Report, Exposure Related Dose Estimating Model (ERDEM) for Assessing Human Exposure and Dose.

Model Evaluation
Extensive QA and testing procedures followed with each enhancement; specific test data sets are maintained for testing and evaluation purposes; comparisons are made with independent data sets.

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