APPENDIX
A
STANDARD
FORMULAS
USED
FOR
CALCULATING
OCCUPATIONAL
AND
RESIDENTIAL
EXPOSURES
TO
2,4­
D
Appendix
A
­
Page
2
A.
Introduction
This
document
is
a
summary
of
the
formulas
used
to
calculate
occupational
and
residential
exposures
to
2,4­
D.
These
formulas
and
a
basic
description
of
how
they
are
used
were
taken
from
References
A
through
F.
These
references
also
contain
more
detailed
information
on
the
rationale
behind
these
formulas.
Only
those
formulas
that
are
pertinent
to
2,4­
D
exposures
are
discussed
in
this
document.

B.
Occupational
Handler/
Applicator
Exposures
The
basic
rationale
for
these
formulas
is
that
the
daily
exposure
is
the
product
of
the
amount
of
active
ingredient
(
a.
i.)
handled
per
day
times
a
unit
exposure
value.
The
amount
of
ai
handled
per
day
is
the
product
of
the
application
rate
times
the
area
treated.
For
example,
if
2.0
lb/
acre
of
2,4­
D
were
applied
to
200
acres
in
one
day,
the
amount
of
2,4­
D
handled
that
day
would
be
400
lbs.
The
unit
exposure
value
is
the
amount
of
exposure
that
results
from
handling
a
given
amount
of
active
ingredient
by
a
certain
method
while
using
certain
PPE.
For
example,
the
dermal
unit
exposure
value
for
open
mixing
and
loading
of
liquids
with
only
minimal
PPE
is
2.9
mg
per
pound
of
ai
handled.
In
this
example,
the
daily
exposure
would
be
400
lbs
ai
handled
times
2.9
mg
unit
exposure
per
pound
of
ai
handled
which
equals
1160
mg
per
day.
The
daily
absorbed
dose
(
mg/
kg
BW)
is
calculated
from
the
exposure
by
multiplying
the
exposures
times
an
absorption
factor
(
0.058)
and
dividing
the
result
by
the
body
weight
(
60
kg).
In
this
example
the
daily
dose
would
be
(
1160
mg/
day
*
0.058)/
60
kg
which
would
equal
1.12
mg/
kg/
day.

Daily
dermal
exposure
is
calculated:

Daily
dermal
exposure
=
Unit
exposure
x
Application
rate
x
Area
Treated
(
mg/
day)
(
mg/
lb
ai)
(
lb
ai/
acre)
(
acres/
day)

Where:

Unit
exposure
=
normalized
exposure
value
(
mg
exposure
per
pound
ai
handled)
derived
from
chemical
specific
study
data
or
from
the
PHED
Surrogate
Exposure
Table
in
Reference
A.
Application
rate
=
normalized
application
rate
based
on
a
logical
unit
treatment
such
as
acres,
a
maximum
value
is
generally
used
(
lb
ai/
acre);
and
Area
treated
=
normalized
application
area
such
as
acres/
day.

[
Note:
(
lb
ai/
acre)
and
(
A/
day)
are
replaced,
respectively,
with
(
lb
ai/
gal)
and
(
gal/
day)
when
appropriate]

Daily
inhalation
unit
exposure
values
were
calculated
for
inclusion
into
the
PHED
surrogate
exposure
tables
and
presented
as
(

g/
lb
ai)
based
on
a
human
inhalation
rate
of
29
L/
minute
and
an
8­
hour
working
day.
Appendix
A
­
Page
3
Daily
inhalation
exposure
is
calculated:

Daily
inhalation
exposure
=
[
Unit
exposure
x
Application
rate
x
Area
Treated]
/
Conversion
Factor
(
mg/
kg/
day)
(
1
mg/
1000
ug)

Where:

Unit
exposure
=
normalized
exposure
value
(

g/
lb
ai
handled)
derived
from
study
data
or
PHED;
Application
rate
=
same
as
for
dermal
exposure
(
lb
ai/
acre);
and
Daily
treatment
=
same
as
for
dermal
exposure
(
acres/
day).

Absorbed
daily
dermal
and
inhalation
doses
are
then
calculated
by
adjusting
for
dermal
and
inhalation
absorption
and
normalizing
by
body
weight.
A
body
weight
of
60
kg
(
adult
female
body
weight)
was
used
for
short
term
exposure
because
the
effects
observed
in
the
short
term
toxicological
study
were
of
concern
for
females
13­
50
years
of
age.
A
body
weight
of
70
kg
was
used
for
intermediate
term
exposures
because
the
effects
were
not
gender
specific.

Absorbed
Daily
Dose
is
calculated:

Absorbed
daily
dermal
or
inhalation
dose
=
(
Daily
dermal
or
inhalation
exposure
x
absorption
factor)
/
body
weight
(
mg/
kg/
day)
(
mg/
day)
(
unitless)
(
kg)

[
Note:
an
absorption
factor
of
0.058
was
used
for
dermal
exposures
and
1.0
for
inhalation
exposures.]

Because
2,4­
D
exposures
from
the
dermal
and
inhalation
routes
have
the
same
toxicological
effects,
a
combined
absorbed
daily
dose
can
be
calculated.
Once
the
combined
absorbed
daily
doses
are
calculated,
the
combined
Margins
of
Exposure
(
MOEs)
can
be
calculated.

Combined
Absorbed
Daily
Dose
is
calculated:

Combined
Dose
(
mg/
kg/
day)
=
Absorbed
dermal
dose
(
mg/
kg/
day)
+
Absorbed
inhalation
dose
(
mg/
kg/
day)

Combined
Margin
of
Exposure
is
calculated:

Combined
MOE
(
unitless)
=
NOAEL
(
mg/
kg/
day)
/
Combined
Dose
(
mg/
kg/
day)

The
target
MOEs
are
100
for
occupational
handlers.
Scenarios
with
MOEs
greater
than
the
target
MOEs
do
not
exceed
the
Agency's
level
of
concern
for
the
occupational
population.
Appendix
A
­
Page
4
C.
Residential
Handler
Exposures
Residential
handler
exposures
are
calculated
in
the
same
manner
as
described
above
for
occupational
handlers,
however,
there
are
a
few
differences
in
the
assumptions
used.
These
differences
are
described
in
References
B
and
C
and
include
the
following:

*
Clothing
consists
of
short
sleeved
shirt
and
short
pants.
*
PPE
such
as
chemical
resistant
gloves
and
respirators
are
not
worn.
*
The
areas
treated
are
much
smaller.

D.
Post­
Application
Occupational
Exposures
The
formulas
used
to
estimate
daily
dermal
dose
and
the
MOE
for
the
dermal
postapplication
scenarios
are
similar
to
those
described
above
for
the
handler/
applicator
scenarios.
The
only
major
difference
is
that
the
daily
dermal
exposure
is
calculated
by
multiplying
the
dislodge­
able
foliar
residue
level
(
ug/
cm2
of
leaf
area)
times
a
transfer
coefficient
(
amount
of
leaf
area
contacted
per
hour
for
a
given
activity).
Inhalation
exposures
are
not
calculated
for
the
postapplication
scenarios
because
inhalation
exposures
have
been
shown
to
account
for
a
negligible
percentage
of
the
overall
body
burden.
This
is
particularly
true
for
2,4­
D
which
has
a
very
low
vapor
pressure.

The
following
equation
taken
from
Reference
D
is
used
to
calculate
dermal
doses
for
2,4­
D
on
each
post­
application
exposure
day
after
application.

Post­
Application
Dermal
Exposure
is
calculated:

Dermal
exposure
(
mg/
day)
=
(
DFR
at
day
t)
x
CF1
x
TC
x
DA
x
#
hours/
day
)

Where:

DFR
=
dislodgeable
foliar
residue
(
ug/
cm2)
at
day
(
t)
after
application
CF1
=
conversion
factor
to
convert
DFR
value
in
ug/
cm2
to
mg/
cm2
TC
=
transfer
coefficient
(
cm2/
hour)
DA
=
dermal
absorption
factor
=
0.058
for
2,4­
D
Hours/
day
=
standard
assumption
is
8
hours
exposure
per
day
Once
the
post­
application
dermal
exposure
are
calculated,
the
dermal
dose
and
MOEs
are
calculated
in
the
similar
manner
as
described
for
handlers.
The
single
difference
is
that
only
the
dermal
route
of
exposure
is
considered.
The
target
MOE
is
100
for
occupational
exposures.
Appendix
A
­
Page
5
Absorbed
Daily
Dose
is
calculated:

Absorbed
daily
dose
(
mg/
kg/
day)
=
(
daily
dermal
exposure
(
mg/
day)
x
dermal
absorption
factor)
/
BW
(
kg)

[
Note:
an
absorption
factor
of
0.058
was
used
for
dermal
exposures
Margin
of
Exposure
is
calculated:

MOE
(
unitless)
=
NOAEL
(
mg/
kg/
day)
/
Absorbed
Daily
Dose
(
mg/
kg/
day)

E.
Residential
Post
Application
Exposure
on
Treated
Turf
The
SOPs
For
Residential
Exposure
Assessment
(
Reference
B)
define
several
pathways
that
apply
to
post
application
exposure
on
treated
turf.
The
SOPs
and
the
associated
pathways
are
presented
below:


Dose
from
dermal
exposure
on
treated
turf
calculated
using
SOP
2.2:
Postapplication
dermal
dose
among
toddlers
from
playing
on
treated
turf,
adults
working
on
treated
turf
and
adults
playing
golf
on
treated
turf;


Dose
from
hand­
to­
mouth
activity
from
treated
turf
calculated
using
SOP
2.3.2:
Postapplication
dose
among
toddlers
from
incidental
non­
dietary
ingestion
of
pesticide
residues
on
treated
turf
from
hand­
to­
mouth
transfer
(
i.
e.,
those
residues
that
end
up
in
the
mouth
from
a
child
touching
turf
and
then
putting
their
hands
in
their
mouth);


Dose
from
object­
to­
mouth
activity
from
treated
turf
calculated
using
SOP
2.3.3:
Postapplication
dose
among
toddlers
from
incidental
non­
dietary
ingestion
of
pesticide
residues
on
treated
turf
from
object­
to­
mouth
transfer
(
i.
e.,
those
residues
that
end
up
in
the
mouth
from
a
child
mouthing
a
handful
of
treated
turf);
and

Dose
from
soil
ingestion
activity
from
treated
turf
calculated
using
SOP
2.3.4:
Postapplication
dose
among
toddlers
from
incidental
non­
dietary
ingestion
of
pesticide
residues
from
ingesting
soil
in
a
treated
turf
area
(
i.
e.,
those
soil
residues
that
end
up
in
the
mouth
from
a
child
touching
treated
soil
and
turf
then
putting
their
hands
in
their
mouth).

Exposures
were
calculated
by
considering
the
potential
sources
of
exposure
(
i.
e.,
TTRs
on
lawns)
then
calculating
dermal
exposure,
and
risks
in
the
same
manner
as
described
for
the
occupational
post
application
risk
assessments.

The
other
aspects
of
the
turf
exposure
scenario
involves
calculating
dose
from
non­
dietary
ingestion
that
arises
from
the
hand­
to­
mouth,
object­
to­
mouth
and
soil
ingestion
pathways.
The
algorithms
used
for
each
type
of
calculation
are
presented
below.
Appendix
A
­
Page
6
Dermal
Exposure
from
Treated
Turf
Dermal
exposure
from
treated
turf
is
calculated
using
the
following
formula
(
SOP
2.2):

Dermal
exposure
(
mg/
day)
=
(
TTR
at
day
t)
x
CF1
x
TC
x
conversion
factor
x
#
hours/
day)

Where:

TTR
=
transferable
turf
residue
(
ug/
cm2)
at
day
(
t)
after
application
CF1
=
conversion
factor
to
convert
TTR
value
in
ug/
cm2
to
mg/
cm2
TC
=
transfer
coefficient
(
cm2/
hour)
DA
=
dermal
absorption
factor
=
0.058
for
2,4­
D
Hours/
day
=
standard
assumption
is
2
to
4
hours
of
exposure
per
day
depending
upon
the
activity
In
the
case
of
2,4­
D
the
TTR
data
were
taken
from
submitted
studies
which
used
the
ORETF
roller,
therefore,
the
TTR
values
could
be
used
directly
as
discussed
in
Reference
B.
The
transfer
coefficients
are
500
cm2/
hour
for
golfing,
5200
cm2/
hour
for
toddlers
playing
on
treated
turf
and
14,500
cm2/
hour
for
adults
performing
heavy
yardwork.
An
exposure
duration
of
2
hours
per
day
is
used
for
toddlers
playing
on
treated
turf
and
for
adults
performing
heavy
yardwork.
An
exposure
duration
of
4
hours
per
day
is
used
for
golfing.

The
formula
for
calculating
the
dissipation
rate
when
TTR
data
are
available
is
as
follows:

TTRt
=
TTRi*
e­
kt
where:

TTRt
=
TTR
at
time
t
after
application
TTRi
=
TTR
initially
after
application
(
i.
e.
at
Day
0)
e
=
2.718
k
=
Slope
of
the
regression
of
the
ln
transformed
TTR
values
vs
time
t
=
Dissipation
time
after
application
(
days)

Exposures
from
Hand
to
Mouth
Behavior
on
Treated
Turf:

The
following
formula
illustrates
the
approach
used
to
calculate
the
non­
dietary
ingestion
exposures
that
are
attributable
to
hand­
to­
mouth
behavior
on
treated
turf
(
SOP
2.3.2).

PDR
=
TTR
*
(
SE/
100)
*
SA
*
Freq
*
Hours
*
(
1
mg/
1000
ug)
where:

PDR
=
potential
dose
rate
from
hand­
to­
mouth
activity
(
mg/
day);
TTR
=
Turf
Transferable
Residue
where
dissipation
is
based
on
TTR
study
and
the
0­
day
value
is
based
on
the
5%
initial
transferability
factor
(

g/
cm2);
SE
=
saliva
extraction
factor
(
50%);
SA
=
surface
area
of
the
hands
(
20
cm2);
Freq
=
frequency
of
hand­
to­
mouth
events
(
20
events/
hour);
and
Appendix
A
­
Page
7
Hours
=
exposure
duration
(
2
hours).

When
used
for
hand
to
mouth
exposures,
the
TTR
value
is
based
upon
the
default
assumption
of
5
percent
of
the
application
rate
and
not
the
TTR
study
because
the
TTR
studies
do
not
account
for
"
the
sticky
hand
effect"
as
discussed
in
Reference
C.
The
TTR
study
data
are
used,
however,
to
determine
the
dissipation
rate.

The
formula
for
calculating
the
TTR
value
on
Day
0
is
given
below:

TTR
=
Application
Rate
*
F
*
CF1
*
CF2
*
CF3
Where:
Application
Rate
=
lbs
ai/
acre
F
=
fraction
of
applied
ai
that
is
available
for
hand
to
mouth
exposure
(
5
percent)
CF1
=
1.0
lb
ai/
acre
equals
2.3
x
10­
5
lbs
ai
per
ft2
CF2
=
4.54
x
108
ug/
lb
CF3
=
0.00108
ft2/
cm2
Note:
CF1
*
CF2
*
CF3
=
11.23
Exposures
from
Object
to
Mouth
Behaviors
on
Treated
Turf
The
following
formula
illustrates
the
approach
used
to
calculate
exposures
that
are
attributable
to
object­
to­
mouth
behavior
on
treated
turf
that
is
represented
by
a
child
mouthing
on
a
handful
of
turf
(
SOP
2.3.3):

PDR
=
TTR
*
IGR
*
(
1mg/
1000ug)
where:
PDR
=
potential
dose
rate
from
mouthing
activity
(
mg/
day);
TTR
=
Turf
Transferable
Residue
where
dissipation
is
based
on
TTR
study
and
the
0­
day
value
is
based
on
the
20%
initial
transferability
factor
(

g/
cm2);
and
IgR
=
ingestion
rate
for
mouthing
of
grass
per
day
(
25
cm2/
day).

When
used
for
object
to
mouth
exposures,
the
TTR
value
is
based
upon
the
default
assumption
of
20
percent
of
the
application
rate
and
not
the
TTR
study
because
the
TTR
studies
do
not
account
for
"
saliva
washing
effect"
as
discussed
in
Reference
C.
The
TTR
study
is
used,
however,
to
determine
the
dissipation
rate.

Exposures
from
Soil
Ingestion
on
Treated
Turf
The
following
formula
illustrates
the
approach
used
to
calculate
exposures
that
are
attributable
to
soil
ingestion
(
SOP
2.3.4):
Appendix
A
­
Page
8
PDR
=
SR
*
IgR
*
(
0.000001
gm/
1
ug)
Where:
PDR
=
dose
from
soil
ingestion
activity
(
mg/
day)
SR
=
Soil
Residue
where
dissipation
is
based
on
TTR
study
and
the
0­
day
value
is
based
on
the
application
rate,
1
cm
depth
of
surface
soil,
and
the
density
of
soil
(

g/
cm3)
IgR
=
ingestion
rate
for
daily
soil
ingestion
(
mg/
day)

MOE
Calculations
for
Each
Pathway
The
MOEs
are
calculated
for
each
individual
pathway
using
the
MOE
formula:

MOE
(
unitless)
=
NOAEL
/
(
Dose
/
BW)

where
NOAEL
=
mg/
kg/
day
Dose
=
mg/
day
BW
=
15
kg
(
toddlers)
and
60
kg
(
adults)

MOEs
Calculations
for
All
of
the
Pathways
Combined
When
assessing
adult
exposures
only
the
dermal
pathway
is
considered
and
when
assessing
toddler
exposures
all
of
the
pathways
are
considered.
The
doses
from
the
four
pathways
are
combined
as
shown
below
to
yield
a
total
dose:

Total
Dose
=
(
Dermal
Dose
+
Hand­
to
Mouth
Dose
+
Object
to
Mouth
Dose
+
Soil
Ingestion
Dose)/
BW
Where:
Dose
=
mg/
kg/
day
BW
=
15
kg
for
toddlers
The
total
dose
is
then
used
to
calculate
an
MOE
as
shown
above.

F.
Swimmer
Exposures
The
swimmer
exposures
were
calculated
using
dermal
and
ingestion
formulas
taken
from
the
SWIMODEL
(
version
2.0
of
November
20,
2001)
which
is
discussed
in
the
residential
SOPs.

Dermal
Exposures
of
Recreational
Swimmers
The
formula
for
dermal
exposure
of
recreational
swimmers
is
as
follows:
Appendix
A
­
Page
9
ADR
=
Cw
*
SA
*
ET
*
Kp
*
(
1
liter/
1000
cm3)

where:

ADR
=
absorbed
dose
rate
Cw
=
concentration
of
ae
in
lake
water
ET
=
exposure
time
(
hours
per
day)
SA
=
surface
area
of
the
body
(
cm2)
Kp
=
permeability
coefficient
(
cm/
hr)

The
formula
for
dermal
dose
is
as
follows:

Dose
=
ADR/
BW
where:

Dose
=
absorbed
dose
in
mg/
kg/
day
BW
=
body
weight
(
22
kg
for
children
and
60
kg
for
adults)

Ingestion
Exposures
of
Recreation
Swimmers
The
formula
for
ingestion
exposure
is
as
follows:

PDR
=
Cw
*
IgR
*
ET
where:
PDR
=
potential
dose
rate
Cw
=
concentration
of
ae
in
lake
water
IgR
=
ingestion
rate
of
lake
water
ET
=
exposure
time
(
hours/
day)

MOE
Calculations
for
Each
Pathway
The
MOEs
are
calculated
for
each
individual
pathway
using
the
same
MOE
formula
as
described
above
for
the
other
exposure
scenarios.

MOE
(
unitless)
=
NOAEL
/
Dose
where
NOAEL
=
mg/
kg/
day
Dose
=
mg/
kg/
day
Appendix
A
­
Page
10
MOEs
Calculations
for
All
of
the
Pathways
Combined
When
assessing
swimmer
exposures
the
dermal
and
ingestion
pathways
are
considered
for
both
adults
and
children.
The
dose
from
the
dermal
and
ingestion
pathways
are
combined
as
shown
below
to
yield
a
total
dose:

Total
Dose
=
(
dermal
dose
+
ingestion
dose)

The
total
dose
is
then
used
to
calculate
an
MOE
as
shown
above.
Appendix
A
­
Page
11
References
(
A)
PHED
Surrogate
Exposure
Guide,
V1.1.
Health
Effects
Division,
Office
of
Pesticide
Program.
August,
1998.

(
B)
Standard
Operating
Procedures
for
Residential
Exposure
Assessments.
U.
S.
EPA.
December
18,
1997.

(
C)
ExpoSAC
SOP
#
12
"
Recommended
Revisions
to
the
Standard
Operating
Procedures
(
SOPs)
for
Residential
Exposure
Assessments.
February
22,
2001
(
D)
Series
875
­
Occupational
and
Residential
Exposure
Test
Guidelines,
Group
B
­
Post
Application
Exposure
Monitoring
Test
Guidelines.
U.
S.
EPA.
February
10,
1998.

(
E)
Overview
of
Issues
Related
to
the
Standard
Operating
Procedures
for
Residential
Exposure
Assessment,
Presented
to
the
FIFRA
Scientific
Advisory
Panel
on
September
1999
(
F)
Dang,
W.
(
1996)
The
swimmer
exposure
assessment
model
(
SWIMODEL)
and
its
use
in
estimating
risks
of
chemical
use
in
swimming
pools.
EPA
internal
guidance
document.
