Description:

SHEDS-Pesticides (Stochastic Human Exposure and Dose Simulation Model for Pesticides) is a physically-based stochastic model developed to quantify exposure and dose of humans to multimedia, multipathway pollutants. 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 (multimedia, single chemical) of children to pesticides (e.g., chlorpyrifos). The aggregate model is currently being expanded to address cumulative exposures (multimedia, multiple chemicals), with the first application focusing on children?s exposures to pyrethroids.

Record Details:

Record Type:MODEL

Product Published Date:01/13/2004

Record Last Revised:07/11/2011

Record ID: 75824

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Model Detail:

Model Evaluation :Initial model evaluation has been conducted by comparing the modeled urinary metabolite concentrations against available measurement data from field studies (e.g., EOHSI/Rutgers residential chlorpyrifos study; NHEXAS Minnesota Children's Study). Although initial model evaluation has revealed that the model produces reasonable results compared to available measurements data, model evaluation will be ongoing as the model inputs and algorithms are refined and as new human exposure field measurements become available.

Conceptual, mathematical and chemical/physical verification has been performed by model developers. Peer reviewed publications on earlier version of the SHEDS-Pesticides model are available. The aggregate SHEDS-Pesticides chlorpyrifos case study was presented to and favorably reviewed by the ORD University Partnership Agreements peer consultation panel in 2002. Several iterations of sensitivity and uncertainty analyses have been conducted for the aggregate chlorpyrifos case study to identify key inputs and parameters influencing results. A scientific advisory panel specific for further evaluation and refinement of the SHEDS model is being planned.

An Aggregate Residential Exposure Model Comparison Workshop was conducted by ORD and OPP in October 2001 in which SHEDS-Pesticides was compared to other aggregate exposure models being developed (Lifeline, CARES, Calendex). The SHEDS results compared well to those of other models for the case studies considered.

Model Guidance Documents :Currently not available.

Model Decision Documents :Select publications describing the model:

1) Zartarian V.G., Ozkaynak H., Burke J.M., Zufall M.J., Rigas M.L., and Furtaw Jr. E.J. (2000). "A Modeling Framework for Estimating Children's Residential Exposure and Dose to Chlorpyrifos via Dermal Residue Contact and Non-Dietary Ingestion." Environmental Health Perspectives. 108(6): 505-514.

2) Zartarian V.G., Ozkaynak H., Xue J., 2001. "Assessing Residential Exposure Using the Stochastic Human Exposure and Dose Simulation (SHEDS) Model," International Society for Exposure Analysis (ISEA) Conference, Charleston, SC, November 2001.

Model Download Information :Currently not available. The model is presently being refined and will be beta tested prior to its public release.

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, pesticide usage information (e.g., amount per application and area, application method, time, and frequency), environmental concentrations and residues (air, soil, dust, food, surface residues), exposure factors (e.g., surface-to-skin residue transfer efficiency, frequency of hand-to-mouth contact, fraction skin surface area contacted), CSFII food consumption survey data, pharmacokinetic rate constants

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 exposure, mass metabolite in blood, and mass metabolite eliminated in urine via the inhalation, dietary ingestion, dermal contact, and non-dietary ingestion routes, and also the absorbed and eliminated dose aggregated across all routes.

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 (C++ prototype version available)

other_req :User friendly GUI?s