1
Terrestrial
Investigation
Model
x2.0
Dermal
Exposure
2
Development
Goals
°
Tool
reliant
on
existing
fate
data
sets
°
Consider
adapting
existing
Agency
approaches
°
Relate
exposure
to
available
toxicity
information
3
Dermal
Conceptual
Model
Directly
applied
spray
Dislodged
residues
from
foliage
Residues
associated
with
soil
particulate


X

proposed
model
addresses
X
not
addressed
4
Interception
of
Directly
Applied
Spray
IDD
A
SA
BW
rate
ercept
=
int
where:
IDD
=
Intercepted
Dermal
Dose
mg/
kg
Arate
=
application
rate
from
label
converted
to
mg/
m2
SAintercept
=
exposed
surface
area
of
bird
intercepting
applied
pesticide
(
m2)

BW
=
bird
body
weight
(
kg)
5
Incidental
Dermal
Contact
with
Dislodgeable
Foliar
Reside
IDCD
C
F
R
SA
TC
BW
plant
dfr
foliar
contact
foliar
contact
=

where:
IDCD
=
Incidental
Dermal
Contact
Dose
mg/
kg
C
plant
=
concentration
of
the
pesticide
in
crop
foliage
at
time
t
(
mg/
kg)

F
dfr
=
dislodgeable
foliar
residue
adjustment
factor
(
kg/
m2)

R
foliar
contact
=
rate
of
foliar
contact
(
m2
foliage/
hr/
m2
body
surface)

SA
foliar
contact
=
surface
area
of
bird
in
contact
with
foliage
(
m2)

TC
=
residue
transfer
coefficient
BW
=
bird
weight
(
kg)
6
Surface
Area
(
)

SA
BW
total
=
10
1000
1000
0
667
(
)
.

SA
SA
ercept
total
int
.

=
0
5
where:
BW
=
bird
weight
in
kg
Interception
of
spray
assumes
SA
is
for
upper
half
of
bird
Incidental
foliar
contact
assumes
contact
with
lower
leg
and
foot
SA
SA
foliar
contact
total
(
m
)
.

2
0
07
=
7
Pesticide
Concentration
on
Plant
°
Uses
the
foliar
concentrations
from
dietary
exposure
module
of
the
model
8
Dislodgeable
Foliar
Residue
Adjustment
Factor
F
DPR
TPR
dfr
=

where:
DPR
=
Dislodgeable
pesticide
residues
(
mg/
m2)

reported
in
submissions
to
the
Agency
TPR
=
Total
pesticide
residues
(
mg/
kg)

reported
in
submissions
to
the
Agency
9
Foliar
Contact
Rate
°
Surface
area
bird
contacts
over
a
given
exposure
period
°
Agency
has
no
data
specific
to
birds
°
Field­
worker
exposure
contact
rates
are
used
as
a
surrogate
°
Focus
on
measured
contact
rates
for
fruit/
vegetable
picker
hands
as
surrogate
for
bird
feet
(
11.9
to
5050
cm2/
hr)

°
Contact
rates
are
normalized
to
hand
surface
area
using
840
cm2
estimate
of
hand
surface
area
°
Foliar
contact
rate
used
in
the
model
is:

(
5050
cm2/
hr)/
840
cm2
=
6.01
cm2/
hr/
cm2
10
Foliar
Contact
Rate
°
Contact
rates
represent
an
"
effective
rate"

°
Dosimetry
studies
measure
residues
on
body
°
Dislodgeable
residues
are
measured
on
plants
°
Contact
rates
are
the
ratio
of
dosimetry:
dislodgeable
residues
°
Dosimeters
may
saturate
before
end
of
exposure
period
or
transfer
of
residues
may
be
less
than
complete
°
Question
of
surrogacy,
future
research
needed
°
Importance
of
other
areas
of
the
bird
surface
for
foliar
contact
11
Transfer
Coefficient
°
Place
holder
in
the
model
°
Anticipates
eventual
information
on
bird
foliar
contact
rates
°
Would
allow
for
consideration
of
the
efficiency
of
residue
transfer
from
foliage
to
bird
12
Scenarios
for
Dermal
Exposure
°
Direct
Spray
Interception
Exposure
 
First
time
step
following
application
 
In­
field
residents
(
air
and
ground
spray
applications)

 
Edge
residents
(
air
spray
applications)

°
Incidental
Foliar
Contact
Exposure
 
Every
time
step
bird
is
actively
feeding
on
field
13
Relating
Dermal
Exposure
to
Available
Toxicity
Data
°
No
Agency
requirement
for
acute
dermal
toxicity
testing
in
birds
°
TIM
x2.0
relies
on
avian
single
oral
dose
toxicity
°
Model
goal
is
to
evaluate
cumulative
exposure
from
multiple
routes
°
Need
a
method
to
relate
external
dermal
dose
to
available
toxicity
endpoints
14
Developing
a
Route
Relative
Potency
Factor
where:
Fred
=
the
avian
route
equivalency
factor
for
dermal
exposure
Need
a
dermal
toxicity
estimate.

F
LD
LD
red
avian
oral
for
species
x
avian
dermal
for
species
x
=
50
50
(
)

(
)
15
Dermal
Toxicity
Estimate
°
Estimate
relies
on
available
comparative
toxicity
testing
for
both
dermal
and
acute
oral
exposure
in
birds
*
error
estimates
in
next
presentation
°
Incorporated
into
the
Fred
calculation
(
)

log
.
.
log
*

(
)
(
)

LD
LD
dermal
oral
50
50
0
84
0
62
=
+

(
)

F
LD
red
avian
oral
LD
oral
=
+
50
0
84
0
62
10
50
(
)

.
.
(
log
(
)
16
Applying
Fred
to
Dermal
Exposure
Estimates
°
Uses
existing
toxicity
data
for
birds
°
Estimates
of
acute
dermal
toxicity
are
for
external
dose,
simplifying
exposure
adjustments
°
Limited
by
power
of
correlation
between
oral
and
dermal
exposures
°
Limited
by
chemicals
represented
in
the
toxicity
database
equivalent
oral
dose
mg/
kg
=
(
model
dermal
dose
mg/
kg)(
Fred)
17
Mortality
0
0.2
0.4
0.6
0.8
1
Exposure
Scenario
Mortality
Rate
(

n=

10,000)
Food
and
Dew
Food,
Dew
,
Direct
Dermal
Spray
Food,
Dew
,
Dermal
Contact
Food,
Dew
,
Dermal
Spray,

Dermal
Contact
Impact
of
Dermal
Exposure
on
Risk
Assessment
Chem
X
Scenario
°
Field
Resident
Insectivore
°
0.5
lb
ai/
acre,
aerial
application
at
8am
Average
Total
Dose
at
Death
1
1.2
1.4
1.6
1.8
2
Exposure
scenario
m
g/

kg
oral
dose
equivalent
Food
and
Dew
Food
Dew
,
Direct
Dermal
Spray
Food,
Dew
,
Dermal
Contact
Food,
Dew
,
Dermal
Spray,

Dermal
Contact
18
Next
Steps
°
Sensitivity
analysis
(
parameter
influences
on
exposure
estimates
and
risk
estimates)

°
Improved
methods
for
dermal
contact
and
transfer
of
residues
°
Longer
term
investigation
of
PBTK
models
19
Relating
external
dermal
dose
to
oral
dose
equivalents
°
If
dermal
and
oral
data
are
available,
a
route
equivalence
factor
(
Fred)
is
calculated
as:

°
Currently
Agency
does
not
have
data
requirement
for
avian
acute
dermal
toxicity
test.
)

x
species
for
dermal
avian
(

50
)

x
species
for
oral
avian
(

50
LD
LD
red
F
=
20
If
only
oral
data
are
available..

°
Must
estimate
a
dermal
LD50
°
To
accomplish
this
used:

 
Definitive
oral
and
dermal
LD50'
s
are
available
for
42
individual
avian
studies
 
Explored
data
to
evaluate
relationship
between
oral
and
dermal
LD50'
s
 
Used
linear
regression
to
define
relationship,
similar
to
Mineau
(
2002)
21
Dermal
LD50
vs.
Oral
LD50
r
=
0.55
22
°
In
addition
to
using
oral
LD50
to
predict
dermal
LD50,
several
chemical
properties
were
included
in
the
regression
to
try
to
improve
predictive
ability
 
molecular
weight,
density,
molar
volume
 
none
of
the
chemical
properties
significantly
improved
fit
of
the
regression
model
23
Final
Regression
Equation
Therefore,
Fred
is
estimated
as:
)

LD
(
log
62
.

0
84
.

0
(
)

oral
avian
(

50
red
)

oral
avian
(

50
10
LD
F
+

=

log
(
Dermal
LD50)
=
0.84
+
0.62*
log
(
Oral
LD50)

standard
errors:
(
0.14)
(
0.15)

p­
value
(
slope)
=
0.0002
model
Rsquare
=
0.30
