Description:

SHEDS-Wood (Stochastic Human Exposure and Dose Simulation Model for Wood Preservatives) is a physically-based stochastic model that was developed to quantify exposure and dose of children to wood preservatives on treated playsets and residential decks. Probabilistic inputs are combined in physical/mechanistic algorithms to estimate exposure and dose using a two dimensional Monte-Carlo methodology that quantifies variability and uncertainty in model inputs and outputs. To date the model has focused on simulating aggregate exposures of children to chromated copper arsenate (CCA)-treated wood.

Record Details:

Record Type:MODEL

Product Published Date:01/13/2004

Record Last Revised:08/31/2009

Record ID: 75823

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Model Detail:

Model Evaluation :No biomonitoring studies are currently available to compare against SHEDS-Wood model predictions. Initial model evaluation has been conducted by comparing SHEDS-Wood dose predictions against other deterministic model results for CCA (e.g., CPSC, Exponent, Gradient). Although model-to-model comparison revealed that the model produces reasonable results compared to other models, model evaluation will be ongoing as new human exposure field measurements become available.

Conceptual, mathematical and chemical/physical verification has been performed by model developers. The SHEDS-Wood methodology was reviewed by the OPP FIFRA SAP in August 2002, and the refined model applied to a CCA case study. The SHEDS-Wood CCA assessment was presented to and favorably reviewed by the December 2003 OPP FIFRA SAP. The technical report for this assessment is posted on the SAP web site for that meeting. This report describes algorithms and model inputs in detail, as well model predictions for dose and results of sensitivity and uncertainty analyses to identify key inputs and parameters influencing results.

Model URL :http://www.epa.gov/scipoly/sap/tools/atozindex/sheds.htm

Model Guidance Documents :The User's Guide is not yet available for the current version.

Model Download Information :Documentation of model assumptions, data inputs, model outputs and analyses can be viewed and downloaded from the OPP FIFRA SAP December 3-5, 2003 web sites:

http://www.epa.gov/scipoly/sap/tools/atozindex/sheds.htm

A Probabilistic Exposure Assessment for Children Who Contact CCA-Treated Playsets and Decks, Draft Preliminary Report, September 25, 2003.

modelcontactinfo :Dr. Valerie Zartarian
EPA/ORD/NERL/HEASD
Zartarian.valerie@epa.gov
617-918-1541

Dr. Haluk Ozkaynak
EPA/ORD/NERL
Ozkaynak.haluk@epa.gov
202-564-1531

Model Inputs :CHAD time-location-activity diaries, other activity pattern information (e.g., days per year child plays on/around playsets/decks, fraction outdoor time child contacts treated wood), soil concentrations and wood surface residues, exposure factors (e.g., surface-to-skin residue transfer efficiency, frequency of hand-to-mouth contact, fraction skin surface area contacted, soil ingestion rates), dermal and GI absorption rates

Model Outputs :Output options include individual daily exposure and dose time profiles, population cdfs, summary statistics tables, contributions by route and pathway, sensitivity analyses, and uncertainty analyses for predicted absorbed dose via the dermal contact and non-dietary ingestion routes for wood residues and soil concentrations.

The model offers user the options for generating correlations, multiple regressions and uncertainty analysis using multiple stepwise regression analysis techniques to identify the variables and parameters that are most influential and those that contribute to greatest uncertainty in the predicted estimates.

Model Computer Requirements:

Model Operating Systems Needs :Windows NT, Windows 2000, Windows XP

Model Hardware Needs :PC Computer, at least 128 MB RAM, at least 500 MHz, at least 10GB hard drive, CD-ROM drive; faster processor and higher RAM recommended

Model Programming Language(s) :SAS version 8 for PC including AF, Base, Stat, SASGraph, and Access