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science in ACTION
INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE
www.epa.gov/research
High-Throughput Exposure Forecasting
Exposure Forecasting
(ExpoCast)
EPA evaluates the potential human
health and environmental risks
associated with the manufacture
and use of thousands of chemicals.
The process of evaluating the risk
from a chemical involves assessing
both the potential harm, or hazard,
and the degree of exposure.
In addressing the potential hazard
of a chemical, EPA's Toxicity
Forecaster (ToxCast) project is
using advanced high-throughput
screening technology to rapidly
screen thousands of chemicals for
potential hazards.
Complimentary to ToxCast, EPA
is also working on the exposure
piece of the puzzle which requires
estimating levels of exposure to
thousands of chemicals. Currently,
there is a lack of exposure
information for the majority of
chemicals in commerce today. To
address the need for exposure
information, EPA is developing
innovative high-throughput
methods to estimate exposure to
these chemicals. EPA refers to this
high-throughput exposure
estimation or "forecasting"
research effort as ExpoCast
High Throughput Exposure
Predictions
ExpoCast provides high-
throughput exposure estimations
for thousands of chemicals.
ExpoCast quickly
and efficiently looks
at multiple routes of
exposure to provide
exposure estimates,
and has been applied
to almost 8,000 chemicals.
ExpoCast uses two types
of models to estimate
exposure, farfield and
nearfield.
Farfield Exposure
Models
Farfield exposure
models are used to
estimate exposure
from chemicals that
are released into the
environment.
Pictured Above: Farfield Exposure Examples
Pictured Above: Examples of Nearfield Exposure,
Consumer Use and Indoor
ExpoCast uses two
already available models, USEtox
and RAIDAR, to estimate
chemical exposure from industrial
environmental releases. These
models have sufficient throughput
to estimate the average amount of
a chemical in air, water, and soil.
Nearfield Exposure Models
Nearfield exposure models provide
estimates of exposure to chemicals
found in consumer products and
other in-home sources. SHEDS-
Fligh-Throughput (SFIED-FIT) was
developed from EPA's existing
Stochastic Human Exposure and
Dose Simulation Model for
Multimedia, Multipathway
Chemicals (SHEDS-MM) model.
SHEDS-HT estimates population
level distributions of exposure to
nearfield chemical sources.
SFIEDS-FIT can produce estimates
for thousands of chemicals in a
more rapid and cost-effective
manner. SHEDS-FIT accounts for
multiple routes, scenarios, and
pathways of exposure to
understand the total exposure to
these chemicals while retaining
population and life stage
information. It has broad
applicability, is flexible for what
inputs are allowed, and can easily
provide exposure estimates for
new chemicals.
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U.S. Environmental Protection Agency
Office of Research and Development
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High-Throughput Prediction
Evaluation
EPA is currently evaluating the
effectiveness of these high-
throughput exposure models using
the Systematic Empirical
Evaluation of Models (SEEM)
framework.
The SEEM framework includes
calibration and evaluation of the
models using chemical
concentrations found in blood and
urine samples from the National
Health and Nutrition Examination
Study.
EPA's high-throughput models are
continually being refined as more
data is gathered for consumer
product use, non-targeted chemical
exposure screening, and from
estimates for oral doses. The
SEEM framework allows for the
systematic evaluation of whether
the additional data improves the
exposure predictions.
Consumer Product Use
High-throughput exposure models
can be improved by adding more
refined indoor and consumer use
information. The Chemical and
Product Categories database
(CPCat) catalogs the use of over
40,000 chemicals in different
consumer products. The chemical
use information is compiled from
multiple sources while product
information is gathered from
public Material Safety Data Sheets
(MSDS) available from retail
stores. EPA continually updates
this database as more information
is gathered from various data
sources.
Non-Targeted Chemical
Exposure Screening
Most exposure sampling
techniques are chemical-specific
and designed to test for chemicals
that are suspected to be present.
EPA researchers are developing
"Non-Targeted Screening"
methods to test indoor
environmental samples for all
chemicals present in the home.
High-Throughput
Toxicokinetics
It is also important to be able to
link the external dose of a
chemical to an internal blood or
tissue concentration to better
inform predictions of adverse
effects. This process is called
toxicokinetics. EPA researchers
are working to measure the critical
factors that determine the
distribution and metabolic
clearance for hundreds of
chemicals and incorporate these
factors as inputs for computer
models.
Using the computer models, EPA
researchers can calculate the
administered dose required to
achieve biological activity in the
ToxCast high-throughput
screening assays. This process
allows ToxCast data to be
compared with ExpoCast
predictions and other exposure
data to identify chemicals with the
potential to disturb cellular
pathways at relevant human
exposure levels.
How Exposure Fits into Risk
Based Decisions
The goal is to combine HT
exposure predictions with ToxCast
bioactivity data to estimate
potential risk to human health and
the environment. ToxCast and
ExpoCast will help EPA better
evaluate the safety of the
thousands of chemicals found in
products used every day.
For more information
ExpoCast webpage:
http: //www. epa.gov/ncct/expocast/
CPCat webpage:
http: //actor. c pa. go v/c peat/face s/h o
me .xhtml
ToxCast webpage:
http: //www. epa.gov/ncct/toxcast/
Contact
Monica Linnenbrink
Communications Director
linnenbrink .monica@epa. gov
Kristin Isaacs Project Lead
isaacs.kristin@epa.gov
John Wambaugh Project Lead
wambaugh.iohn@epa.gov
Main Office: 919.541.4219
http: //www. epa.gov/comptox
109 T.W. Alexander Drive
Research Triangle Park, NC 27711
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U.S. Environmental Protection Agency
Office of Research and Development
March 2016

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