HES2D:
SHEDS
and
ERDEM
March
3,
2003
The
Human
Exposure
Source­
to­
Dose
Modeling
(
HES2D)
framework
houses
a
number
of
exposure
and
dose
models
including
SHEDS
and
ERDEM.
The
Stochastic
Human
Exposure
and
Dose
Simulation
(
SHEDS)
modeling
system
is
being
developed
for
analyzing
multimedia
multipathway
exposures
of
both
the
general
and
sensitive
subpopulations,
such
as
children
and
the
elderly.
The
Exposure­
Related
Dose
Evaluation
Model
(
ERDEM)

Purpose:
HES2D
was
designed
to
provide
a
scientifically­
robust,
complete
multimedia,
multipathway
modeling
framework
that
can
1)
estimate
exposures
and
doses
to
both
the
general
population
and
to
identifiable
susceptible
subpopulations,
and
2)
predict
and
diagnose
the
complex
relationships
between
source
and
exposure
and
dose.
The
modeling
framework
software
and
its
various
components
and
modules
and
other
analytical
tools
will
assist
researchers
engaged
in
the
development,
refinement,
and
interpretation
of
human
exposure
modeling
techniques.
In
addition,
the
tools
in
HES2D
will
provide
the
risk
assessment
community
with
a
set
of
useful
modeling
software
packages
to
enable
multimedia,
multipathway
exposures
to
be
estimated
­
with
explicitly
quantified
variability
and
uncertainty
­
for
a
wide
variety
of
subpopulations
and
environmental
contaminants.
This
capability
will
also
provide
EPA
Program
Offices
with
analytical
software
tools
and
algorithms
to
support
the
prioritization
of
pollutants
and
pollutant
source
categories
in
support
of
future
mitigation
strategies
to
evaluate
human
exposure
and
risk
implications
of
pollutants
in
air,
soil,
food
and
water.

The
Stochastic
Human
Exposure
Dose
Modeling
System
(
SHEDS)
models
have
been
developed
to
assess
exposure
to
pesticides
and
particulate
matter
(
PM)
and
when
considered
collectively
provide
estimates
of
exposures
through
four
routes
of
exposure:
inhalation,
dermal
absorption,
dietary
ingestion,
and
non­
dietary
ingestion.
SHEDS
is
a
physically­
based,
probabilistic
computer
model
that
predicts,
for
user­
specified
cohorts,
exposures
and
doses
incurred
via
eating
contaminated
foods
or
drinking
water,
inhaling
contaminated
air,
touching
contaminated
surface
residues,
and
ingesting
residues
from
hand­
or
object­
to­
mouth
activities.
To
do
this,
it
combines
information
on
pesticide
usage,
human
activity
data
(
from
time/
activity
diary
surveys
and
videography
studies),
environmental
residues
and
concentrations,
exposure
and
dose
factors
using
1­
stage
or
2­
stage
Monte
Carlo
probabilistic
sampling
methods.

ERDEM
is
a
modeling
system
that
allows
the
development
of
physiologically
based
pharmacokinetic
models
for
any
chemical
of
interest.
Exposure
inputs
are
multimedia
and
multipathway
in
nature.
To
date
the
system
has
been
applied
to
several
pesticides,
trichloroethylene
and
other
chlorinated
solvents
and
by­
products
found
in
drinking
water
and
air,
MTBE.
Current
work
is
on
extending
the
applications
for
carbamates
and
pyrethroid
pesticides.
ERDEM
can
examine
scenario­
based
aggregate
exposure
along
several
pathways
(
e.
g.,
dermal
transfer
from
surfaces,
inhalation
within
micro­
environments,
and
ingestion
of
food
as
well
as
extraneous
matter
via
hand­
to­
mouth
activity)
as
simultaneous
inputs
to
internal
dose
from
several
routes
(
e.
g.,
dermal
absorption,
oral,
and
respiratory)
as
a
means
to
assess
cumulative
risk.

Status:
Work
began
in
October
1,
1998
and
will
continue
through
September
30,
2003.
To
date,
research
has
focused
on
the
development
of
the
conceptual
components
for
a
source­
to­
dose
human
exposure
modeling
framework
and
software
system.
Initial
testing
has
been
done
on
the
framework
for
exposures
and
dosimetry
using
the
Stochastic
Human
Exposure
and
Dose
System
(
SHEDS)
models.
Significant
progress
has
been
made
in
the
development
and
refinement
of
important
framework
components
such
as
an
improved
understanding
of
phase,
spatial,
and
temporal
distributional
characteristics
for
various
pollutants
of
interest
and
the
prediction
of
variability
and
uncertainty
in
modeling
outputs.
Critical
inputs
to
the
SHEDS
and
ERDEM
models,
such
as
the
Consolidated
Human
Activity
Database
(
CHAD)
or
the
Human
Exposure
Database
System
(
HEDS)
are
being
linked
to
HES2d.

Contact:
Eric
Hall
(
919)
541­
3147?

Short­
term
Followup:
Discuss
with
HES2D,
SHEDS,
and
ERDEM
staff
the
status
of
the
framework
and
the
models
to
determine
ways
to
utilize
them
as
a
screening
level
tool
for
identifying
national­
level
concerns
or
trends
in
human
health
and
the
environment.

Long­
term
Followup:
Discuss
with
HES2D,
SHEDS,
and
ERDEM
staff
the
possibility
of
using
these
tools
for
in­
depth
evaluation
of
the
stressors
identified
in
the
short­
term
(
and
their
possible
sources)
to
support
the
more
detailed
investigation
phase
of
the
304(
m)
planning
process.
