Applying An Innovative Model

(SHEDS; Stochastic Human Exposure And Dose Simulation Model)

To Assess Children's Exposures To Pesticides

Valerie Zartarian, Jianping Xue, Haluk Ozkaynak: Office of Research and Development, National Exposure Research Laboratory

Moving Science
into Action

Issue being Addressed

>	Accurately quantifying children's aggregate exposures to pesticides is critical for the Agency to make
regulatory decisions on pesticide usage

r Not feasible to measure actual personal exposures for entire populations of children with different age
and behavior dependent characteristics

>	Regulatory decisions often use scenario-based models with varying levels of sophistication

>	Risk assessors and managers need more realistic exposure and dose prediction tools beyond the
currently available screening level methods

Scientific Approach to Resolve Issue

SHEDS is a state-of-the-science model for
simulating contact with and uptake by pesticides
that can answer the following questions;

What is the population distribution
of exposure and dose, accounting
for variability in activities, pesticide
levels contacted, and other factors?

What is the uncertainty
in modeled estimates?



30 40 H) 60 70

What is the time profile of
exposures and doses for
an individual in the
population?

lI

Which model inputs are
most important?

Which are the most important routes
and pathways of exposures and doses
for different populations and scenarios?

l-low do exposures and
doses change after a
pesticide application?

Case Studies to Date

Modeling Children's Exposures to Organophosphate Pesticides from Lawn, Garden, and Indoor Crack and Crevice Treatments

>	Relative abundance of data allowed for initial model development and
evaluation (publication in Environmental Health Perspectives 2000).

>	Results of aggregate assessment indicated hand-to-mouth and
dermal routes appear more important for highly exposed individuals;
dietary and inhalation routes for lower exposed individuals.

>	Initial sensitivity and uncertainty analyses helped prioritize additional
data needs.

>	Modeled estimates of urinary levels compared well to field
measurements, but additional data and model evaluation are needed.

>	2001 Aggregate Residential Exposure Model Comparison Workshop
led by ORD/NERL provided guidance for OPP to conduct model
comparisons as part of their regulatory process.

Modeling Children's Exposures to Wood Preservatives on Playsets and Home Decks

>	Collaboration between ORD and OPP led to successful review of SHEDS wood preservative exposure
assessment methodology by OPP Science Advisory Panel (SAP) August 2002.

>	SAP comments being addressed to refine model and conduct SHEDS application for CCA (chromated
copper arsenate)-treated wood.

>	SHEDS-generated exposure and dose estimates for CCA will be used by OPP as part of public health
risk assessment.

>	SAP review of arsenic and chromium exposure and risk assessment scheduled for December 2003.

>	Consumer Product Safety Commission (CPSC) deferred action on petition to ban CCA-treated wood for
use in playground equipment until EPA's CCA assessment is complete.

Modeling Children's Exposures to Pyrethroid Pesticides from Lawn, Garden, Crack and Crevice, Fogger, and Pet Treatments

>	Collaborative effort among ORD Labs and Centers, and OPP as part of ORD Safe
Foods Project.

>	Aggregate SHEDS model will be enhanced to simulate real-world uses of multiple
pesticides and application methods for cumulative exposure and dose assessment.

>	Model predictions to be compared against several real-world measurement studies.

>	SHEDS exposure estimates intended for use in OPP regulatory-decision making
process for pyrethroids under the Food Quality Protection Act of 1996.

>	SAP review of SHEDS model for pyrethroids assessment planned for late 2004.



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Dietary Ingestion Exposures ||

Impact on Science

>	Modeling tool for Agency to improve pesticide-related risk assessment and management
decisions and to prioritize data needs

>	Produces population exposure distributions to enhance Agency risk assessments

>	Helps identify areas of critical data needs for measurement programs

>	Utilizes innovative computational techniques to address emerging issues

Partnering	to Protect Human

CPx


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