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Model Report

Total Human Exposure Risk Database and Advance Simulaiton Environment

Last Revision Date: 11/16/2009 View as PDF
General Information Back to Top
Model Abbreviated Name:

Model Extended Name:

Total Human Exposure Risk Database and Advance Simulaiton Environment
Model Overview/Abstract:
THERdbASE is no longer supported by EPA and is no longer available as download.

THERdbASE is a collection of databases and models that are useful to assist in conducting assessments of human exposure to chemical pollutants, especially for inhalation exposure to indoor airborne volatile organic compounds (VOCs). THERdbASE is a user-friendly Windows-type application for personal computers. It contains eleven (11) different human exposure-related modeling modules and the data necessary to use these models. The models within THERdbASE, some of which can be run in a coordinated manner, include the following, with model numbers corresponding to those in THERdbASE:

101. Subsetting Activity Pattern Data

102. Locations Patterns - Simulated

103. Source - Timed Application

104. Source - Instantaneous Application

105. Indoor Air - 2 Zones

106. Indoor Air - N Zones

107. Exposure - Inhalation - BEAM [Benzene Exposure Assessment Model]

108. Exposure - Inhalation - Multiple Chemicals

109. Dose - Dermal - Film Thickness

110. Scenario - Dose - Inhalation/Dermal

201. Soil Exposure/Dose Assessment

Most of the models in THERdbASE can conduct either single-scenario or Monte Carlo simulations. Models 101 and 102 are used to select demographic subpopulations and simulate the activity and location sequences of people within that subpopulation. Simulations are based on data from human activity surveys. Those data are stored within datafiles within THERdbASE. Models 103 and 104 simulate the release of volatile organic compounds, over either a user-selected period of time, or in an instantaneous release, respectively, into indoor air. Models 105 and 106 simulate the airborne concentrations of VOCs in multi-zone indoor environments. The simulated VOCs are those whose emissions were simulated in Models 103 and 104. Models 107 and 108 simulate the inhalation exposure to benzene or other VOCs, respectively, of people as they inhabit multiple environments as defined by their location and activity patterns. Model 109 simulates peoples' dermal (skin) exposure to chemicals. Model 110 combines inhalation and dermal exposure simulations. Model 201 simulates exposure to chemical contaminants on soil.

A significant limitation of THERdbASE is the limited ability of users to import their own data. Many of the models are constrained to using the existing databases that are also a built-in part of THERdbASE.

THERdbASE was created as a research and development prototype of a user-friendly software system for linking data and models in performing human exposure and risk assessments. No further versions or improvements to THERdbASE are planned by the EPA.

The next generation of EPA's human exposure data will be made available in an Internet-accessible system referred to as HEDS, the Human Exposure Data System. HEDS will not contain exposure models. Further developments of the exposure modeling concepts of THERdbASE, using other program names, are being pursued by Info Scientific Inc. of Henderson, Nevada.

Model Technical Contact Information:
THERdbASE is no longer supported by EPA and is no longer available as download.

Questions or comments should be referred to Peter Knudsen at knudsen.peter@epa.gov

Model Homepage: http://epa.gov/heasd/edrb/therd/therd-home.htm Exiting the EPA Site
Substantive Changes from Prior Version: N/A
Plans for further model development: N/A

User Information Back to Top
Technical Requirements
Computer Hardware
Compatible Operating Systems
Windows 3.1 or earlier
Windows 95, 98, or later
Other Software Required to Run the Model
C or C+
Download Information
THERdbASE is publicly available on CD by request to William Engelman.
Using the Model
Basic Model Inputs
Screening model with moderate input requirements.
User Support
User's Guide Available?
Documentation is available by request to William Engelman.

It provides: (1) an abstract or abstract equivalent in the introduction, (2) schematic/diagram showing model structure and interaction of model components, (3) equations, equation solution methodologies, and related simplifying assumptions, (4) example input/output files, (5) input and output variable documentation including definitions, units, temporal/spatial dimensions, and temporal/spatial resolution options, (6) guidance on selecting and/or estimating values and/or distributions for input variables (including guidance on calibration and selecting default values and/or distributions).

User Qualifications
User needs only moderate level of technical education and/or modeling experience.

Model Science Back to Top
Summary of Model Structure and Methods
Simulates movement of potentially exposed populations.

The model uses fixed units (S.I.).

The model provides mathematical guidance to assist the user when selecting modeling parameters.

Model Evaluation
The concept of THERdbASE in it current version, i.e., a Windows-based, user-friendly suite of linkable human exposure-related models and databases, was externally peer reviewed.

The THERdbASE models are contained within an object-oriented framework.

Governing equations are solved numerically by Monte Carlo simulation.

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