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Model Report


Last Revision Date: 07/11/2011 View as PDF
General Information Back to Top
Model Abbreviated Name:

Model Extended Name:

Model Overview/Abstract:
E-FAST Version 2 is an exposure assessment tool that conservatively models screening-level estimates of the concentrations of chemicals released to air, surface water, landfills, and from consumer products. This model also estimates inhalation, dermal and ingestion potential dose rates from these releases. In addition, it estimates the number of days per year that an aquatic ecotoxicological concern concentration will be exceeded for organisms in surface water.
Keywords: Exposure assessment model; screening-level
Model Technical Contact Information:
Conrad Flessner
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue N.W. (7406M)
Washington, DC 20460
(202) 564-8541
Model Homepage: http://www.epa.gov/oppt/exposure/pubs/efast.htm
Substantive Changes from Prior Version:
  • Data sources are updated
  • MSWord output now available
  • Expanded documentation
  • Ambient air releases modeled with SCREEN3, a USEPA Office of Air model
  • More at Home Page
Plans for further model development: Occasional updates; most water data sources will change in next update

User Information Back to Top
Technical Requirements
Computer Hardware
Pentium PC or equivalent, 32 MB RAM plus 85 MB hard disk capacity
Compatible Operating Systems
Windows 95 or later; Windows Vista users must run E-FAST V2.0 as Administrators
Other Software Required to Run the Model
Windows Vista users must download a patch from Microsoft’s download center (www.microsoft.com/downloadsexit EPA, search for Winhlp32.exe and Vista) to use the E-FAST V2.0 help screens
Download Information
Using the Model
Basic Model Inputs
  • Release media
  • Release amount per day and release days per year
  • P-chem properties
  • Generic or specific site characteristics
  • Consumer product type
Basic Model Outputs
  • Potential surface water and ambient air concentrations
  • Potential inhalation and ingestion (drinking water and fish) dose rates from chemical releases to the environment
  • Potential inhalation and dermal dose rates from consumer product chemicals
User Support
User's Guide Available?
User's Guide
Other User Documents
Selected references at website
Availability of User Support
Limited support from technical contact; online training from model web site; face-to-face training available at USEPA Sustainable Futures program, www.epa.gov/oppt/sf/
User Qualifications
Intended to be used by scientists and engineers familiar with exposure assessment principles

Model Science Back to Top
Problem Identification
Developed for screening-level non-occupational exposure assessment of chemical releases considered in USEPA New Chemicals Program administered by USEPA Office of Pollution Prevention and Toxics under Toxic Substances Control Act Section 5
Summary of Model Structure and Methods
Consists of four modules: General Population and Environmental Exposure from Industrial Releases, Down the Drain, Consumer Exposure Pathway, and Probabilistic Dilution Model. The General Population module estimates chemical concentrations in surface water, groundwater, and air. Concentrations are estimated in the following manner: in surface water via simple dilution of chemical release amounts in measured or estimated site-specific or generic streamflows, in groundwater as modeled in SESOIL and AT123D models by chemical LogKoc, in air via the USEPA Screen3 model-a Gaussian distribution model. The Down the Drain module uses simple dilution for surface water releases, but only for releases of consumer products into typical Publically Owned Treatment Works. The Consumer module estimates inhalation and dermal exposures. It uses survey information to estimate release amounts per consumer use and user activity patterns. For inhalation, it estimates emissions via the Chinn empirical relationship or a double-exponential equation, depending on the product, then utilizes the Runge-Kutta method to predict time-varying concentration in each of two indoor zones. Dermal exposures are generally estimated using estimated film thickness of chemical product on the surface area exposed. The Probabilistic Dilution Model (PDM) predicts the likelihood that a chemical release in surface water will exceed a target concentration of concern. It uses either the distribution of measured streamflows for known sites, or the Di Toro method for sites with estimated streamflows. PDM is also incorporated as an option in the General Population and Down the Drain modules.
Model Evaluation
Where possible, model output QA/QC checked against spreadsheet calculations. Update version calculations checked against previous version. Limited model evaluation except for latex paint scenario in consumer exposure module; other methods based on established models, e.g., Gaussian distribution, Runge-Kutta, Chinn relationship. External letter peer review of consumer exposure module in 1998 and the general population, down-the-drain, and probabilistic dilution model modules in 2001

Key Limitations to Model Scope
For screening-level, conservative (protective) estimates; not comprehensive

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