Executive
Summary,
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1
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5
Executive
Summary
A.
Background
In
May
29
­
31,
1996,
the
Agency
presented
two
ecological
risk
assessment
case
studies
to
the
Scientific
Advisory
Panel
(
SAP)
for
review
and
comment.
While
recognizing
and
generally
reaffirming
the
utility
of
EPA's
current
deterministic
assessment
process,
the
SAP
offered
a
number
of
suggestions
for
improvement.
Foremost
among
their
suggestions
was
a
recommendation
to
move
beyond
the
present
single
point
assessment
process
by
developing
the
tools
and
methodologies
necessary
to
conduct
a
probabilistic
assessment
of
effects.
Such
an
assessment
would
estimate
the
magnitude
and
probability
of
the
expected
impact
and
define
the
level
of
certainty
and
variation
involved
in
the
estimate.

The
recommendations
of
the
SAP
were
consistent
with
issues
that
risk
managers
within
EPA's
Office
of
Pesticide
Programs
(
OPP)
raised
in
the
past,
namely
questions
about
the
magnitude
of
the
risk
described
for
a
particular
pesticide,
the
probability
of
the
risk
occurring,
and
the
certainty
of
the
evaluation.

Following
the
recommendations
of
the
SAP
and
in
response
to
issues
raised
by
OPP
risk
managers,
the
Agency
began
an
initiative
to
refine
the
ecological
risk
assessment
process
for
pesticides.
The
refined
process
focuses
on
evaluating
the
effects
of
pesticides
to
terrestrial
and
aquatic
species
within
the
context
of
FIFRA
(
Federal
Insecticide,
Fungicide,
and
Rodenticide
Act),
the
main
statutory
authority
for
regulating
pesticides
at
the
federal
level.

The
key
goals
and
objectives
of
EPA's
initiative
include
the
following:

°
Develop
a
conceptual
approach
to
refine
the
ecological
assessment
process;
°
Incorporate
probabilistic
tools
and
methods
to
provide
an
estimate
on
the
magnitude
and
probability
of
effects;
°
Address
the
broad
spectrum
of
responses
to
pesticide
exposure;
°
Establish
more
realistic
actual
use
scenarios
and
field
conditions;
°
Build
upon
existing
data
requirements
for
registration;
°
Utilize,
wherever
possible,
existing
data
bases
and
create
new
ones
from
existing
data
sources
to
minimize
the
need
to
generate
additional
data;
and
°
Focus
additional
data
requirements
on
reducing
uncertainty
in
key
areas.

The
initiative
began
with
the
formation
of
The
Ecological
Committee
on
FIFRA
Risk
Assessment
Methods
(
ECOFRAM),
a
stakeholder
workgroup,
who
was
tasked
with
identifying
and
developing
probabilistic
tools
and
methods
for
terrestrial
and
aquatic
assessments
under
the
FIFRA
regulatory
framework.
The
conclusions
and
recommendations
of
the
ECOFRAM
were
summarized
in
the
draft
reports,
which
were
peer
reviewed
during
two
public
workshops.

Once
the
reports
and
the
peer
review
workshops
were
completed,
the
Agency
formed
the
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Summary,
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of
5
Refined
Risk
Assessment
Implementation
Team
(
Implementation
Team),
who
was
charged
with
developing
a
plan
to
incorporate
probabilistic
tools
and
methods
into
the
assessment
process.
After
evaluating
the
ECOFRAM
reports
and
workshop
comments,
the
Implementation
Team
developed
a
conceptual
approach
for
implementing
changes
to
the
current
deterministic
assessment
process,
using
the
reports
and
workshop
comments
as
a
starting
point.
This
approach,
which
was
evaluated
and
endorsed
by
the
SAP
in
2000,
is
based
on
a
four­
level
risk
assessment
scheme.

After
proposing
the
four­
level
risk
assessment
scheme,
the
Implementation
Team
focused
on
developing
pilot
models
(
Version
1.0)
and
on
conducting
a
case
study.
The
refined
aquatic
risk
assessment
followed
the
approach
outlined
in
the
Agency's
four­
level
risk
assessment
scheme
for
Level
II.
The
refined
terrestrial
assessment
went
beyond
the
Level
II
assessment
and
fell
somewhere
between
a
Level
II
and
III.
The
case
study
was
presented
to
the
SAP
in
2001
as
a
generic
chemical
(
Chem
X).

Following
the
case
study
with
ChemX,
the
Agency
refined
the
models
based
on
the
SAP
comments
made
in
2001.
In
addition,
the
terrestrial
Level
II
model
was
also
refined
to
include
dermal
and
inhalation
exposure
based
on
recommendations
from
ECOFRAM.
These
routes
of
exposure
were
also
discussed
during
the
2000
SAP
meeting.
The
Level
II
models
(
Version
2.0)
are
the
subject
of
this
SAP
session.

B.
Terrestrial
Level
II
Model
(
Version
2.0)

1.
Overview
The
terrestrial
Level
II
model
(
Version
2.0)
is
a
multimedia
exposure/
effects
model
which
evaluates
acute
mortality
levels
in
generic
or
specific
species
over
a
user­
defined
exposure
window.
The
spatial
scale
is
at
the
field
level,
which
includes
the
field
and
surrounding
area.
Both
areas
are
assumed
to
meet
the
habitat
requirements
for
each
species,
and
contamination
of
edge
or
adjacent
habitat
from
drift
is
assumed
to
be
zero.
It
is
anticipated
that
future
modifications
to
the
assessment
model
will
address
offsite
transport
of
pesticide
residues
via
drift.

The
major
parameters
addressed
in
the
model
are:

°
Multimedia
(
vegetation,
water,
and
air)
estimates
for
oral,
inhalation,
and
dermal
routes
of
exposure;
°
Food
habits
of
defined
generic
species
or
selected
specific
species
that
are
proportioned
for
each
food
type
consumed
by
the
species;
°
Hourly
ingestion/
inhalation
rates
of
food,
water
and
air
as
a
function
of
body
weight,
randomly
assigned
from
species
specific
body
weight
distributions
or
defined
generic
species
body
weight
distributions;
°
Hourly
dermal
residue
transfer
rates
from
contaminated
vegetation
as
a
function
of
body
weight,
randomly
assigned
from
species
(
generic
or
specific)
body
weight
distribution
and
Executive
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5
frequency
in
contaminated
area;
°
Frequency
of
feeding
and
drinking
on
the
sprayed
field,
determined
in
hour
time
steps;
°
Distribution
of
residues
on/
in
vegetation,
water
(
dew
and
puddles),
and
air
as
a
function
of
application
rates;
°
Degradation/
dissipation
rates
of
pesticides
residues
in
each
environmental
media
considered,
i.
e.,
food,
vegetation,
air
and
drinking
water;
and
°
Acute
toxicity
dose­
response
relationship
based
on
a
specific
species
(
when
data
are
available)
or
inter­
species
extrapolations
from
distributions
fit
to
available
effects
data.

For
each
individual
bird
considered
in
a
run
of
the
Level
II
model,
a
random
selection
of
values
is
made
for
the
major
exposure
input
parameters
to
estimate
an
external
(
ingested)
oral
dose
equivalent
for
that
individual
that
accounts
for
body
elimination
rates
in
hourly
time
steps.
The
estimated
external
oral
dose
equivalent
is
compared
to
a
randomly
assigned
tolerance
for
the
individual
preselected
from
the
log
probit
dose/
response
distribution.

The
status
of
this
individual
(
dead
or
not
dead)
for
this
time
step
is
assigned
by
comparing
the
estimated
oral
dose
equivalent
to
the
random
assigned
tolerance.
If
the
dose
is
greater
than
the
tolerance,
the
individual
is
scored
`
dead'.
If
the
dose
is
less
than
or
equal
to
the
tolerance,
the
individual
is
scored
`
not
dead'.
If
scored
`
not
dead',
the
loop
is
continued
until
the
dose
is
greater
than
the
tolerance
or
the
user­
defined
model
duration
is
reached.
This
procedure
is
repeated
using
Monte
Carlo
sampling.
After
multiple
iterations
of
individuals,
a
probability
density
function
of
percent
mortality
is
generated.

2.
Major
Modifications
to
the
Level
II
Model
(
Version
1.0)

The
Level
II
model
was
modified
based
on
changes
suggested
by
the
SAP
in
2000
and
2001.
The
major
changes
suggested
by
the
SAP
in
2001
that
have
been
incorporated
are:

16.
Establishment
of
generic
birds
that
represent
species
that
occur
in
and
around
agroenvironments
The
model
can
use
generic
attributes
to
represent
the
more
vulnerable
species
yet
retains
the
ability
to
address
specific
focal
species,
when
appropriate,

17.
Incorporation
of
a
1­
hour
exposure
time
step
to
allow
the
inclusion
of
a
bimodal
feeding
pattern,
as
well
as
a
higher
resolution
simulation
of
daily
feeding
behavior
between
treated
and
untreated
areas,

18.
Incorporation
of
an
algorithm
(
Markov
Chain)
to
address
serial
correlation
between
sequential
foraging
events,
and
19.
Development
of
a
new
model
for
estimating
pesticide
residues
in
on­
field
drinking
water
sources
(
puddles)
that
accounts
for
a
number
of
parameters
that
affect
puddling
after
a
rainfall
event.
These
parameters
include
rainfall
amount,
rainfall
duration,
soil
infiltration
rates,
evaporation,
degradation
and
the
stochastic
nature
of
field
topography
and
its
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5
relation
to
puddle
formation
and
duration.

In
addition,
an
inhalation
and
a
dermal
model
were
developed.
Limited
data
are
available
regarding
these
routes
of
exposure,
resulting
in
uncertainty
in
the
estimates
of
risks.
However,
if
these
routes
of
exposure
are
ignored
or
assumed
to
be
minimal,
the
uncertainty
in
risk
estimates
is
not
addressed.
This
is
of
concern
because
dermal
and
inhalation
routes
may
contribute
significantly
to
total
dose
in
some
situations.
The
incorporation
of
the
dermal
and
inhalation
exposure
models
provide
an
important
initial
step
to
evaluate
the
potential
significance
of
these
routes
of
exposure
to
the
overall
risk
estimates.

C.
Aquatic
Level
II
Model
(
Version
2.0)

The
aquatic
Level
II
model
is
a
two­
dimensional
Monte
Carlo
risk
model
consisting
of
three
main
components:
exposure,
effects,
and
risk.
The
Version
1.0
model
was
presented
to
the
SAP
in
2001
and
has
been
refined
(
Version
2.0)
to
include
a
varying
volume
surface
water
fate
model
(
VVWM)
to
replace
the
previous
fixed­
volume
surface
water
fate
model.

The
exposure
scenarios
used
at
Level
II
are
intended
to
provide
estimates
of
vulnerable,
edge­
of­
field
situations
across
a
wide
range
of
geographical
conditions
under
which
the
product
is
used.
These
surface
waters
are
considered
vulnerable
because
of
their
size
and
spatial
relationship
to
the
treated
field.
In
addition,
the
soil
series
selected
for
use
in
crop
scenarios
are
considered,
based
on
best
professional
judgement,
to
be
more
vulnerable
to
soil
erosion
in
the
use
area.

The
exposure
component
of
the
model
simulates
field­
scale
pesticide
application,
daily
field
run­
off
and
erosion,
and
fate
to
a
surrogate
surface
water.
Version
1.0
of
the
aquatic
model
uses
the
Pesticide
Root
Zone
Model
(
PRZM)
to
simulate
temporal
run­
off
and
erosion
of
a
pesticide
from
an
agricultural
field,
and
Exposure
Analysis
Modeling
System
(
EXAMS)
to
simulate
the
fate
of
the
pesticide
in
this
run­
off
in
a
fixed
volume
of
surface
water.
In
Version
2.0,
EPA
is
proposing
to
replace
EXAMS
with
a
new
surface
water
fate
model,
VVWM,
which
simulates
the
fate
and
temporal
hydrology
in
a
receiving
water
using
stochastic
temporal
variations
in
weather.
For
both
versions,
the
simulated
daily
surface
water
concentrations
provide
typical
36­
year
maximum
annual
peaks
for
acute
and
chronic
exposure.
After
calculating
these
peak
values,
the
maximum
annual
peak
data
are
fit
to
a
mixed
empirical
distribution
function.

Thus,
these
surface
waters
would
be
expected
to
be
among
the
highest
exposure
concentrations
observed.
However,
this
scenario
is
not
unrealistic
or
overly
conservative
because
these
surface
waters
are
expected
to
be
present
across
the
country.
The
challenge
is
to
develop
an
aquatic
exposure
scenario
that
produces
estimated
environmental
concentrations
(
EECs)
that
are
not
worst
case,
do
not
often
underestimate
pesticide
concentrations,
and
present
a
realistic
and
scientifically
defensible
representation
for
vulnerable,
edge­
of­
field
surface
waters
across
a
wide
range
of
geographical
conditions.

The
Level
II
acute
effects
or
toxicity
component
uses
current
acute
toxicity
tests
for
Executive
Summary,
Page
5
of
5
freshwater
and
saltwater
fish
and
invertebrates
required
for
a
Level
I
risk
assessment
and
includes
slopes
of
the
concentration­
response
curves.
The
Level
I
uses
a
single
point
estimate
based
on
the
most
sensitive
species
tested.
In
contrast,
the
Level
II
uses
a
species
sensitivity
distribution
constructed
for
each
group
and
assumed
to
represent
the
range
of
responses
likely
to
be
encountered.
The
5th,
50th,
and
95th
percentiles
of
the
distribution,
representing
the
generic
5th,
50th,
and
95th
most
sensitive
species
LC
50
(
EC
50)
values,
are
identified.

The
Level
II
chronic
effects
assessment
includes
current
early­
life
stage
and
sensitive
partial
and
full
life­
cycle
tests.
Measurement
endpoints
are
no
observable
adverse
effects
concentrations
for
survival,
reproduction,
and
growth
effects
for
invertebrates
and
embryo
and
larval/
juvenile
survival
and
larval/
juvenile
growth
effects
in
fish.
If
a
test
contains
more
than
one
measurement
endpoint
(
e.
g.,
survival
and
growth),
the
lowest
value
for
a
given
test
is
used.
If
there
are
sufficient
chronic
effects
data,
a
species
sensitivity
distribution
is
constructed,
and
the
5th,
50th,
and
95th
percentiles
are
determined.
However,
in
most
cases,
chronic
data
are
limited,
and
the
risk
analyses
are
restricted
to
individual
species.

The
Level
II
risk
evaluation
process
yields
estimates
of
likelihood
and
magnitude
of
effects
for
acute
exposures.
For
the
estimate
of
acute
risks,
a
distribution
of
estimated
exposure
and
a
distribution
of
lethal
effects
are
combined
through
a
two­
dimensional
Monte
Carlo
analysis
to
obtain
a
distribution
of
joint
probability
functions.
For
the
estimate
of
chronic
risks,
a
distribution
of
exposure
concentrations
is
compared
to
a
chronic
measurement
endpoint.
The
risk
analysis
for
chronic
effects
provides
information
only
on
the
probability
that
the
chronic
endpoint
assessed
will
be
exceeded,
not
on
the
magnitude
of
the
chronic
effect
expected.
The
assessment
then
proceeds
to
outline
the
consequences
of
the
potential
effects.
