UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON
D.
C.,
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
PC
Code
128825
DP
Barcode
D311012
MEMORANDUM
DATE:
February
7,
2006
SUBJECT:
Tier
I
Estimated
Environmental
Concentrations
of
Bifenthrin
for
the
Use
in
the
Human
Health
Risk
Assessment.

TO:
Shaja
Brothers,
Risk
Manager
Reviewer
Sidney
Jackson,
Risk
Manager
Reviewer
BeWanda
Alexander,
Risk
Manager
Reviewer
Daniel
Rosenblatt,
Risk
Manager
#
5
George
LaRocca,
Risk
Manager
#
13
Registration
Division
(
7505C)

AND:
Karen
Whitby,
Branch
Chief
Registration
Action
Branch
I
Health
Effects
Division
(
7509C)

FROM:
José
Luis
Meléndez,
Chemist
ERBV,
Environmental
Fate
and
Effects
Division
(
7507C)

THROUGH:
Jean
Holmes,
DVM,
Acting
Chief
Environmental
Risk
Branch
V
Environmental
Fate
and
Effects
Division
(
7507C)

This
memo
presents
the
Tier
I
Estimated
Surface
Drinking
Water
Concentrations
and
Estimated
Ground
Water
Concentrations
(
EDWCs)
for
Bifenthrin,
calculated
using
the
Tier
I
aquatic
models
FIRST
and
SCI­
GROW,
respectively,
for
use
in
the
human
health
risk
assessment.

The
Estimated
Drinking
Water
Concentrations
(
EDWCs)
for
bifenthrin
were
calculated
based
on
a
maximum
application
rate
of
0.5
lb
a.
i./
A/
season.
The
acute
drinking
water
concentration
in
surface
water
is
0.0140
ppb
of
bifenthrin,
based
on
applications
of
the
chemical
to
lettuce.
The
cancer/
chronic
drinking
water
concentration
is
0.0140
ppb
(
based
on
applications
of
lettuce,
highest
application
rate).
The
SCI­
GROW
generated
EDWC
is
0.00300
ppb
of
bifenthrin,
which
is
recommended
for
use,
both
for
acute
and
chronic
exposures.
Because
of
the
very
low
solubility
of
bifenthrin,
the
EDWCs
did
not
exceed
0.0140
ppb
(
the
solubility
of
bifenthrin).
Table
1
provides
a
summary
of
the
Tier
I
modeled
drinking
water
concentrations.
Should
there
be
a
need
for
additional
refinements,
the
EFED
can
perform
a
Tier
II
aquatic
assessment,
for
surface
waters.

EXECUTIVE
SUMMARY
Bifenthrin
(
chemical
name
2­
methylbiphenyl­
3­
ylmethyl
(
Z)­(
1RS,
3RS)­
3­(
2­
chloro­
3,3,3­
trifluoroprop­
1­
enyl)­
2,2­
dimethylcyclopropanecarboxylate,
CAS#
82657­
04­
03,
PC
code
128825)
is
a
synthetic
pyrethroid
insecticide.
Its
structure
has
three
rings,
two
phenyl
rings
attached
to
each
other
by
a
single
bond,
and
a
cyclopropyl
ring.
The
chemistry
of
bifenthrin
may
be
dictated
by
its
ester
moiety;
however,
laboratory
studies
show
that
it
is
relatively
stable.
The
molecule
has
some
chiral
centers,
and
a
double
bond
that
brings
isomer
possibilities.

Bifenthrin
is
a
neural
toxic
insecticide
acting
through
direct
contact
and
ingestion,
having
a
slight
repellent
effect.
The
primary
biological
effects
of
bifenthrin
and
other
pyrethroids
on
insects
and
vertebrates
reflect
an
inhibition
of
the
correct
firing
of
neurotransmitter
deliver
signals
from
one
cell
to
another
via
nerve
membrane
inhibition
of
the
voltage­
gated
Ca2+
channels
coupled
with
a
stimulatory
effect
on
the
voltage­
gated
Na+
channels
(
sodium
ion
channels).
All
pyrethroids
act
as
axonic
poisons,
affecting
both
the
peripheral
and
central
nervous
systems,
and
share
similar
modes
of
action.
Pyrethroids,
including
bifenthrin,
stimulate
repetitive
action
in
the
nervous
system
by
binding
to
voltage­
gated
sodium
channels,
prolonging
the
sodium
ion
permeability
during
the
excitatory
phase
of
the
action
potential.
This
action
leads
to
spontaneous
depolarizations,
augmented
neurotransmitter
secretion
rate
and
neuromuscular
block,
which
ultimately
results
in
paralysis
of
the
insect.

This
is
a
Tier
I
screening
assessment
using
Tier
1
aquatic
models
SCI­
GROW
and
FIRST,
and
maximum
application
rates
for
bifenthrin,
with
minimum
application
intervals.
It
was
found
that
the
worse
case
scenario
was
lettuce
for
bifenthrin,
with
the
highest
application
rate,
and
the
highest
PCA.
There
are
no
major
degradates
for
bifenthrin;
therefore,
no
degradates
were
modeled
in
this
assessment.
The
major
uncertainty
with
respect
to
this
assessment
appears
to
be
the
problem
with
the
extremely
low
solubility
of
bifenthrin.
The
hydrolysis,
aqueous
photolysis
and
batch
equilibrium
studies
were
performed
in
the
presence
of
unusually
high
concentrations
of
acetonitrile.

The
proposed
uses
involved
in
this
action
are
the
following
IR4
tolerance
petitions:
leafy
brassica
greens,
tuberous
and
corm
vegetables,
dried
shelled
peas
and
beans,
cilantro
and
okra,
and
an
application
to
amend
the
label
to
include
tobacco
(
refer
to
highlighted
section
of
Table
2).

Table
1.
Maximum
Tier
I
Estimated
Drinking
Water
Concentrations
(
EDWCs)
for
drinking
water
risk
assessment
based
on
aerial
application
of
bifenthrin
on
lettuce.

DRINKING
WATER
SOURCE
(
MODEL
USED)
USE
(
rate
modeled)
MAXIMUM
ESTIMATED
DRINKING
WATER
CONCENTRATION
(
EDWC)
(
ppb)

Groundwater
(
SCI­
GROW)
Lettuce
(
0.5
lb.
a.
i./
A/
season)
Acute
and
Chronic
0.00300
Lettuce
(
0.5
lb.
a.
i./
A/
season)
Acute
0.0140
Surface
water
(
FIRST)

Lettuce
(
0.5
lb.
a.
i./
A/
season)
Chronic
0.0140
PROBLEM
FORMULATION
This
is
a
Tier
I
drinking
water
assessment
that
uses
modeling
and
available
monitoring
data
to
estimate
the
groundwater
and
surface
water
concentrations
in
drinking
water
source
water
(
pretreatment
resulting
from
pesticide
use
on
sites
that
are
highly
vulnerable.
This
initial
tier
screens
out
chemicals
with
low
potential
risk
and
allows
OPP
to
focus
resources
on
more
refined
risk
assessments
for
chemicals
which
potentially
present
more
significant
risks.
This
drinking
water
assessment
will
report
potential
exposure
concentrations
for
the
human
health
dietary
risk
assessment
and
provide
a
clear
and
transparent
description
of
how
those
concentrations
were
determined.

ANALYSIS
Use
Characterization
Table
2
is
a
summary
of
all
agricultural
use
patterns
for
bifenthrin.
The
highlighted
uses
are
those
proposed
new
ones.
The
use
information
was
obtained
from
the
current
label
for
Capture
2EC
Insecticide/
Miticide
and
the
proposed
labels
for
the
same
product.

Table
2.
Summary
use
information
for
bifenthrin,
based
on
Capture
2EC
Insecticide/
Miticide
label
(
EPA
Reg.
No.
279­
3069)

USE
SINGLE
APP.
RATE
(
lbs.
a.
i./
A)
NUMBER
OF
APPS.
SEASONAL
APP.
RATE
(
lbs.
a.
i./
A)
INTERVAL
BETWEEN
APPS.
(
days)
APP.
METHOD
INCORPORATION
DEPTH
(
inches)
PHI
Cotton
0.1
5
0.5
3
Ground
or
aerial
0
14
Corn
0.1
3
0.3
As
necessary
Ground
or
aerial
0
30
Sweet
corn
0.1
2
0.2
As
necessary
Ground
or
aerial
0
1
Succulent
peas
and
beans
0.1
2
0.2
Not
specified
Ground
or
aerial
0
3
Brassicas
0.1
5
0.5
7
Ground
or
aerial
0
7
Canola,
Crambe,
Rapeseed
0.04
2
0.08
14
Ground
or
aerial
0
35
Cucurbits
0.1
3
0.3
7
Ground
or
aerial
0
3
Eggplant
0.1
2
0.2
7
Ground
or
aerial
0
7
USE
SINGLE
APP.
RATE
(
lbs.
a.
i./
A)
NUMBER
OF
APPS.
SEASONAL
APP.
RATE
(
lbs.
a.
i./
A)
INTERVAL
BETWEEN
APPS.
(
days)
APP.
METHOD
INCORPORATION
DEPTH
(
inches)
PHI
Lettuce,
head
0.1
5
0.5
7
Ground
or
aerial
0
7
Caneberries
0.1
2
0.2
One
prebloom
and
one
postbloom
Ground
or
aerial
0
3
Artichoke
0.1
Not
specified
15
Ground
or
aerial
0
5
Peppers
0.1
2
0.2
7
Ground
or
aerial
0
7
Hops
0.1
3
0.3
21
Ground
or
aerial
0
14
Pears
0.2
3
0.5
30
Ground
or
aerial
0
14
Citrus
0.25
2
0.5
Early
and
late
season
Ground
0
1
Tomatoes
0.08
4
0.32
10
Ground
0
1
Spinach
0.1
4
0.4
7
Ground
or
aerial
0
40
Grapes
0.1
1
0.1
N/
A
Ground
or
aerial
0
30
Leafy
Brassica
Greens
0.1
4
0.4
7
Ground
or
aerial
0
7
Tuberous
and
corm
vegetables
0.3
in
furrow
at
planting
and
0.1
foliar
3
0.5
21
Foliar
treatment
not
specified
0
21
Dried
shelled
peas
0.1
2
0.2
Not
specified
Ground
or
aerial
0
14
Dried
shelled
beans
0.1
3
0.3
Not
specified
Ground
or
aerial
0
14
Tobacco
0.1
at
transplant,
and
0.05
foliar
Not
specified
0
N/
A
Cilantro
(
coriander)
0.1
5
0.5
7
Ground
or
aerial
0
3
USE
SINGLE
APP.
RATE
(
lbs.
a.
i./
A)
NUMBER
OF
APPS.
SEASONAL
APP.
RATE
(
lbs.
a.
i./
A)
INTERVAL
BETWEEN
APPS.
(
days)
APP.
METHOD
INCORPORATION
DEPTH
(
inches)
PHI
Okra
0.1
2
0.2
7
Ground
or
aerial
0
7
Capture
2EC
Insecticide/
Miticide
is
an
emulsifiable
concentrate.
It
may
be
applied
by
ground,
air
or
ULV
methods.
The
label
imposes
certain
restrictions
(
buffer
zones)
to
protect
bodies
of
water,
accordingly:
25
ft
for
ground
applications,
150
ft
for
aerial
applications
and
450
ft
for
ULV
applications.
There
is
also
a
granular
formulation
for
use
on
corn
at
plant
(
granules
are
incorporated
into
the
top
one
inch
of
the
soil)
or
foliar
(
as
granules).

The
use
pattern
selected
for
drinking
water
modeling
was
lettuce.
It
has
the
maximum
application
rate
(
maximum
number
of
applications)
with
the
maximum
PCA.

Fate
and
Transport
Characterization
Table
3
provides
a
summary
of
the
major
physical,
chemical,
environmental
fate
and
transport
properties
of
bifenthrin.

Table
3.
Summary
of
physical/
chemical
and
environmental
fate
and
transport
properties
of
bifenthrin.

PARAMETER
VALUE(
S)
(
units)
SOURCE
COMMENT
Chemical
Name
2­
methylbiphenyl­
3­
ylmethyl
(
Z)­
(
1RS,
3RS)­
3­(
2­
chloro­
3,3,3­
trifluoroprop­
1­
enyl)­
2,2­
dimethylcyclopropanecarboxylate
 
IUPAC
name
Molecular
Weight
422.87
g/
mol
 
 

Solubility
(
22
oC)
1.4x10­
5
mg/
L
Laskowski
2002
 

Vapor
Pressure
(
25
oC)
1.8
x
10­
7
mmHg
Tomlin,
C.
editor
1994.
 

Henry's
Law
constant
7.2
x
10­
3
Atm­
m3/
mol
­
­
Estimated
from
vapor
pressure
and
water
solubility.

pKa
(
20
oC)
NA
­
­
 

Octanol­
Water
Partition
Coefficient
(
KOW)
3.00x106
Laskowski
2002
 

Hydrolysis
Half­
life
[
pH
5,
7,
9;
(
25
oC)]
Stable
ACC:
251728,
MRID:
132539.
Stable
at
all
pHs.

Aqueous
Photolysis
Half­
life
Relatively
stable
ACC:
264642.
Samples
were
not
buffered
and
contained
30%
acetonitrile
as
cosolvent.
Natural
sunlight
was
used.
PARAMETER
VALUE(
S)
(
units)
SOURCE
COMMENT
Soil
Photolysis
Half­
life
t1/
2
=
147
days
and
98.5
days
for
cyclopropyl
and
phenyl
labels,
respectively.

Corrected
half­
lives
are
147
days
and
106
days
(
no
significant
degradation
in
dark
control
for
cyclopropyl
label)
ACC:
264642.
Natural
sunlight
in
New
Jersey,
silt
loam
soil
used.

Aerobic
Soil
Metabolism
Half­
life
(
days)
Soil
Cyclopropyl
Phenyl
SL
132
115
SiL
250
156
SiCL
129
96.8
MRID:
141202,
254411,
532540,
251728,
254401,
073225,
073174,
251278.
­
­

Anaerobic
Soil
Metabolism
Stable
MRID:
264642
­
­

Anaerobic
Aquatic
Metabolism
Half­
life
NA
­
­
 

Aerobic
Aquatic
Metabolism
Half­
life
NA
­
­
­
­

Organic
Carbon
Partition
Coefficient
(
KOC)
131,000,
239,000,
302,000,
275,000
mL/
gOC
for
the
S,
SL,
SiL
and
SiCL,
respectively
MRID:
254401.
 

Soil
Partition
Coefficient
(
Kd)
992,
4192,
5430,
3690
mL/
g
for
the
S,
SL,
SiL
and
SiCL,
respectively
MRID:
254401.
 

Terrestrial
Field
Dissipation
Half­
life
Site
Half­
lives
Champaign,
IL
192
days
Fresco,
CA
345
Madera,
CA
155
Imperial
County,
CA
228
Tifton,
GA
122
Marion,
AR
78
Fresno,
CA
193
Champaign,
IL
118
Champaign,
IL
126
Marion,
AR
121
San
Joaquin,
Fresno
DT50
35
MRID:
264642,
42339203,
42339201,
42334167,
41673103,
41673101,
41671302.
­
­

Aquatic
Field
Dissipation
Half­
life
Dallas
County,
Orville,
Alabama
Residues
of
bifenthrin
were
found
in
the
sediments
of
the
pond
during
the
12
months
period
after
application;
there
was
no
discernable
pattern
of
decay.
MRID:
40981803,
40981805,
40981808,
40981812,
40981814,
40981815,
40981816,
40981817,
40981818,
40981819.
­
­

Bifenthrin
is
a
synthetic
pyrethroid.
Its
structure
has
three
rings,
two
phenyl
rings
attached
to
each
other
by
a
single
bond,
and
a
cyclopropyl
ring.
The
molecule
has
some
chiral
centers,
and
a
double
bond
that
bring
isomer
possibilities.
According
to
the
Capture
2EC
Insecticide/
Miticide
label,
a
minimum
of
97%
consists
of
cis
isomers
(
see
figure
in
the
Appendix).

Studies
conducted
on
bifenthrin
indicate
that
it
is
persistent
under
most
conditions
and
bioaccumulative.
It
appears
that
a
major
route
of
degradation
is
aerobic
metabolism.
Bifenthrin
is
relatively
stable
to
hydrolysis
at
all
pH's.
It
is
relatively
stable
to
aqueous
and
soil
photolysis
and
degrades
slowly
under
both
aerobic
and
anaerobic
soil
metabolism
conditions
(
half­
life
range
97­
250
days
in
3
soils,
and
relatively
stable,
respectively).
Bifenthrin
is
relatively
immobile
in
four
soils
tested
(
KOC
range
131,000
to
275,000).
Field
studies
show
a
pattern
consistent
with
the
laboratory
studies,
with
relatively
high
persistence
(
half­
lives
ranging
from
78
to
345
days
in
10
field
trials)
and
low
mobility
of
the
chemical
in
soil.
In
aquatic
environments,
it
appears
that
residues
of
bifenthrin
persist
in
pond
sediments
(
and
in
the
water
column)
for
extended
periods
(
at
least
12
months
of
monitoring).
No
major
metabolites
were
observed
(>
10%
of
the
applied)
in
any
of
the
laboratory
studies.
The
high
octanol/
water
partition
coefficient
suggests
that
bifenthrin
will
bioconcentrate
in
aquatic
organisms.
Bifenthrin
was
highly
bioaccumulative
in
fish
with
slow
depuration.
The
very
low
water
solubility
and
hydrophobic
nature
of
bifenthrin
leads
to
strong
soil
adsorption
and
a
tendency
to
partition
to
sediment
in
aquatic
systems.

Bifenthrin
has
a
vapor
pressure
of
1.8x10 
7
mmHg,
water
solubility
of
0.0140
ppb,
and
an
estimated
Henry's
law
constant
of
7.2x10­
3
atm­
m3/
mol.
Based
upon
its
Henry's
law
constant
and
vapor
pressure,
bifenthrin
is
expected
to
have
a
moderate
to
low
potential
for
volatilization
from
soil
and
water
surfaces.
Bifenthrin's
potential
for
volatilization
is
reduced
significantly
because
it
adsorbs
strongly
to
soils,
suspended
solids,
sediment
and
organic
matter
in
the
water
column.
A
laboratory
volatility
study
showed
a
maximum
volatility
at
40
°
C
of
5.07x10­
4
µ
g/
cm2
hr
(
average
at
14
days),
a
relatively
low
value.

Bifenthrin
can
be
spray
applied
by
ground
or
aerially
on
agricultural
settings.
A
buffer
region
is
label
recommended;
however,
under
a
high
end
drift
scenario,
substantial
amounts
of
the
chemical
can
reach
adjacent
bodies
of
water
via
spray
drift.
Furthermore,
substantial
fractions
of
the
applied
bifenthrin
should
be
available
for
runoff
for
several
weeks
to
several
months.
Due
to
its
low
solubility
(
0.014
ppb)
and
high
level
of
binding
it
appears
that
bifenthrin
would
remain
bound
to
the
soils
during
run­
off
events,
and
that
the
chemical
would
reach
surface
waters
if
the
run­
off
event
is
accompanied
by
erosion.
Once
bifenthrin
reaches
surface
water,
the
fate
of
the
chemical
is
of
concern
since
bifenthrin
is
very
toxic
to
fish
and
aquatic
invertebrates.
The
Agency
believes
that
bifenthrin,
due
to
its
high
level
of
binding,
would
remain
bound
to
the
sediments
and
would
dissolve
only
very
slowly
into
the
water
column.
Organisms
that
live
near
the
sediments
may
be
particularly
at
risk.
The
sediments
may
serve
as
reservoirs
of
bifenthrin,
where
it
will
persist.

A
supplemental
aquatic
field
dissipation
study
employing
a
site
in
Alabama
showed
that
bifenthrin
in
aquatic
environments
(
a
pond)
persists
for
extended
periods
of
time.
It
was
found
throughout
the
12
months
of
monitoring
after
the
last
pesticide
application,
that
residues
were
observed
in
the
water
column
and
in
the
sediment,
with
no
clear
pattern
of
decline.

On
the
other
hand,
bifenthrin
is
not
likely
to
reach
subsurface
soil
environments
or
ground
waters.
Various
terrestrial
field
dissipation
studies
confirm
that
bifenthrin
remains
mostly
in
the
upper
soil
level.

Due
to
the
slow
dissipation
pathways
for
bifenthrin,
no
transformation
products
were
observed
to
be
higher
than
10%
of
the
applied
in
any
of
the
laboratory
studies.

The
major
uncertainties
with
respect
to
the
environmental
fate
studies
on
bifenthrin
are
related
to
the
extremely
low
solubility
of
bifenthrin
and
the
problems
found
when
the
registrant
performed
these
studies.
The
hydrolysis,
aqueous
photolysis,
and
batch
equilibrium
studies
were
performed
in
unusually
high
concentrations
of
acetonitrile.
The
cosolvent
may
have
had
an
effect
on
the
results.
Furthermore,
the
batch
equilibrium
studies
were
performed
at
a
single
concentration
(
a
Freundlich
isotherm
was
not
developed).
The
EFED
had
to
rely
on
a
single
point
result.

Table
4
is
a
summary
of
degradate
formation
for
bifenthrin.
Note
that,
because
bifenthrin
is
relatively
stable
or
dissipates
very
slowly
in
all
studies,
no
major
transformation
products
( 
10%
of
the
applied)
were
observed.
Table
4.
Summary
of
degradate
formation
from
degradation
of
bifenthrin.

DEGRADATE
and
MAXIMUM
CONCENTRATION
STUDY
TYPE
SOURCE
DEG1
(%
applied)
DEG2
(%
applied)
DEG3
(%
applied)

Hydrolysis
ACC:
251728,
MRID:
132539.
NO
hydrolysis
product
exceeded
10%
of
the
applied
during
the
study.

Aqueous
Photolysis
ACC:
264642.
NO
aqueous
photolysis
product
exceeded
10%
of
the
applied
during
the
study.

Soil
Photolysis
ACC:
264642..
NO
soil
photolysis
product
exceeded
10%
of
the
applied
during
the
study.

Aerobic
Soil
Metabolism
MRID:
141202,
254411,
532540,
251728,
254401,
073225,
073174,
251278.
NO
aerobic
soil
metabolism
product
exceeded
10%
of
the
applied
during
the
study.

Anaerobic
Soil
Metabolism
.
MRID:
264642
NO
anaerobic
soil
metabolism
product
exceeded
10%
of
the
applied
during
the
study.

Aerobic
Aquatic
Metabolism
.
NA
­
­

Anaerobic
Aquatic
Metabolism
NA
­
­

Terrestrial
Field
Dissipation
MRID:
40981803,
40981805,
40981808,
40981812,
40981814,
40981815,
40981816,
40981817,
40981818,
40981819.
4'­
OH­
Bifenthrin
detected
in
certain
studies.

No
degradates
were
considered
"
major"
(>
10%
of
applied
in
parent
equivalents),
nor
were
they
flagged
for
further
quantitation.
There
is
uncertainty
with
respect
to
the
aqueous
photolysis
study,
which
was
conducted
in
the
presence
of
30%
acetonitrile.
Even
though
no
substantial
photolysis
was
observed,
it
is
not
known
if
the
cosolvent
may
have
affected
the
formation
of
transformation
products.

Drinking
Water
Exposure
Modeling
Models
SCI­
GROW
(
Screening
Concentration
in
Ground
Water)
is
a
regression
model
used
as
a
screening
tool
for
ground
water
used
as
drinking
water.
SCI­
GROW
was
developed
by
regressing
the
results
of
Prospective
Ground
Water
studies
against
the
Relative
Index
of
Leaching
Potential
(
RILP).
The
RILP
is
a
function
of
aerobic
soil
metabolism
and
the
soil­
water
partition
coefficient.
The
output
of
SCI­
GROW
represents
the
concentrations
that
might
be
expected
in
shallow
unconfined
aquifers
under
sandy
soils,
which
is
representative
of
the
ground
water
most
vulnerable
to
pesticide
contamination
likely
to
serve
as
a
drinking
water
source.
(
Ref.
2)

FIRST
(
FQPA
Index
Reservoir
Screening
Tool)
is
a
screening
model
designed
by
the
Environmental
Fate
and
Effects
Division
(
EFED,
2001a)
of
the
Office
of
Pesticide
Programs
to
estimate
the
concentrations
found
in
drinking
water
from
surface
water
sources
for
use
in
human
health
risk
assessment.
As
such,
it
provides
upper
bound
values
on
the
concentrations
that
might
be
found
in
drinking
water
due
to
the
use
of
a
pesticide.
FIRST
is
a
single
event
model
(
one
runoff
event),
but
can
account
for
spray
drift
from
multiple
applications.
Spray
drift
(
resulting
in
direct
deposition
of
the
pesticide
into
the
reservoir)
is
assumed
to
be
16%
of
the
applied
active
ingredient
for
aerial
application,
6.3%
for
orchard
air
blast
application,
and
6.4%
for
other
ground
spray
application.
FIRST
is
hardwired
to
represent
the
Index
Reservoir,
a
standard
water
body
used
by
the
Office
of
Pesticide
Programs
to
assess
drinking
water
exposure
(
Office
of
Pesticide
Programs,
2002).
It
is
based
on
a
real
reservoir
(
albeit
not
currently
in
active
use
as
a
drinking
water
supply),
Shipman
City
Lake
in
Illinois,
that
is
known
to
be
vulnerable
to
pesticide
contamination.
The
single
runoff
event
moves
a
maximum
of
8%
of
the
applied
pesticide
into
the
reservoir.
This
amount
can
be
reduced
due
to
degradation
on
the
field
and
the
effects
of
binding
to
soil
in
the
field.
FIRST
also
uses
a
Percent
Cropped
Area
(
PCA)
factor
to
adjust
for
the
area
within
the
watershed
that
is
planted
to
the
modeled
crop.
The
default
agricultural
PCA
is
0.87.
(
Ref.
3
and
4)

For
volatile
and
semi­
volatile
compounds,
Tier
I
modeling
will
tend
to
over­
estimate
EDWCs
because
there
are
no
parameters
in
SCI­
GROW
and
FIRST
that
explicitly
take
into
account
volatility
(
ie.,
no
vapor
pressure
input).
Therefore,
in
reality,
more
of
the
compound
will
be
volatilizing
than
Tier
I
can
account
for.
If
drinking
water
levels
of
concern
are
exceeded
for
overestimated
Tier
I
EDWCs,
Tier
II
modeling
will
be
able
to
refine
these
EDWCs
by
including
volatility
considerations.

Modeling
Approach
and
Input
Parameters
Table
5
provides
the
input
parameter
values
used
for
modeling
of
bifenthrin
using
SCI­
GROW.
Table
6
provides
the
input
parameter
values
used
for
modeling
of
bifenthrin
using
FIRST.
As
indicated
earlier,
no
degradates
were
included
in
the
modeling
because
none
exceded
10%
of
the
applied
in
the
laboratory
studies.

Table
5.
SCI­
GROW
(
v2.3)
input
parameter
values
for
bifenthrin
use
on
lettuce1.

PARAMETER
(
units)
VALUE(
S)
SOURCE
COMMENT
Maximum
Application
Rate
(
lb
a.
i./
A)
0.1
Label.
 

Number
of
Applications
per
Year
5
Label.
Represents
most­
conservative
scenario
in
which
the
total
maximum
rate
per
year
is
applied
in
one
application.

Organic
Carbon
Partition
Coefficient
(
Koc;
mL/
g)
257,000
MRID:
254401.
Represents
the
median
value
of
four
values
ranging
from
131,000
to
302,000
mL/
g
for
the
parent
compound.

Aerobic
Soil
Metabolism
Half­
life
(
days)
130.5
MRID:
141202,
254411,
532540,
251728,
254401,
073225,
073174,
251278.
Represents
the
median
half­
life
of
six
values
available
(
132,
250,
129,
115,
156,
96.8
days).

1
Parameters
are
selected
as
per
Guidance
for
Selecting
Input
Parameters
in
Modeling
the
Environmental
Fate
and
Transport
of
Pesticides;
Version
I,
February
28,
2002.

Table
6.
FIRST
(
v1.0)
input
parameter
values
for
bifenthrin
use
on
lettuce1.

PARAMETER
(
units)
VALUE(
S)
SOURCE
COMMENT
Application
Rate
(
lb
a.
i./
A)
0.1 
Label.
 

Number
of
Applications
5
Label.
­
­

Interval
between
Applications
(
days)
3
Label.
­
­

Percent
Cropped
Area
(
decimal)
0.87
­
­
National
default.
PARAMETER
(
units)
VALUE(
S)
SOURCE
COMMENT
Soil
Partition
Coefficient
(
Kd;
(
mL/
g)
or
KOC
(
mL/
gOC))
275,000
MRID:
254401.
Represents
the
lowest
non­
sand
KOC
value
among
four
values
ranging
from
131,000
to
302,000
mL/
g;
the
KOC
model
was
utilized
as
per
recommendation
of
the
SAP..

Aerobic
Soil
Metabolism
Half­
life
(
days)
176.4
MRID:
141202,
254411,
532540,
251728,
254401,
073225,
073174,
251278.
Represents
the
90th
percentile
of
the
upper
confidence
bound
on
the
mean
of
six
half­
life
values:
132,
250,
129,
115,
156,
96.8
days;
mean
=
146.5
days;
std.
dev.=
49.6
days
Wetted
in?
No
Label.
 

Depth
of
Incorporation
(
inches)
0
Label.
 

Method
of
Application
Aerial
spray
Label.
 

Solubility
in
Water
@
22
OC,
unbuffered
(
mg/
L
or
ppm)
0.000014
Laskowski
2002
 

Aerobic
Aquatic
Metabolism
Half­
life
(
days)
352.8
MRID:
141202,
254411,
532540,
251728,
254401,
073225,
073174,
251278.
No
aerobic
aquatic
metabolism
data
are
available
and
the
pesticide
is
hydrolytically
stable,
2X
the
aerobic
soil
metabolism
half­
life
input
value
is
used.

Hydrolysis
Half­
life
@
pH
7
(
days)
0
ACC:
251728,
MRID:
132539
Stable.

Aquatic
Photolysis
Half­
life
@
pH
7
(
days)
0
ACC:
264642
 

1
Parameters
are
selected
as
per
Guidance
for
Selecting
Input
Parameters
in
Modeling
the
Environmental
Fate
and
Transport
of
Pesticides;
Version
I,
February
28,
2002
Modeling
Results
Table
7.
Maximum
Tier
I
Estimated
Drinking
Water
Concentrations
(
EDWCs)
for
drinking
water
risk
assessment
based
on
aerial
application
of
bifenthrin.

DRINKING
WATER
SOURCE
(
MODEL
USED)
USE
(
rate
modeled)
MAXIMUM
ESTIMATED
DRINKING
WATER
CONCENTRATION
(
EDWC)
(
ppb)

Groundwater
(
SCI­
GROW)
Lettuce
(
0.5
lb
a.
i./
A/
season)
Acute
and
Chronic
0.0140
Lettuce
(
0.5
lb
a.
i./
A/
season)
Acute
0.0140
Surface
water
(
FIRST)

Lettuce
(
0.5
lb
a.
i./
A/
season)
Chronic
0.00300
SCI­
GROW
concentration
(
ppb)
represents
the
groundwater
concentration
that
might
be
expected
in
shallow
unconfined
aquifers
under
sandy
soils.
Output
is
used
for
both
acute
and
chronic
endpoints.

FIRST
concentrations
(
ppb)
represent
untreated
surface
water
concentrations.
The
peak
day
concentration
(
over
30
years)
is
used
for
acute
endpoints
and
the
annual
average
concentration
(
over
30
years)
is
used
for
chronic
endpoints.

The
estimated
concentrations
provided
in
this
assessment
are
conservative
estimates
of
concentrations
in
drinking
water.
If
dietary
risks
require
refinement,
higher
tiered
cropspecific
and
location­
specific
models
and
modeling
scenarios
can
be
utilized.
Monitoring
Data
Monitoring
data
usually
provide
different
kinds
of
information
than
modeling
(
e.
g.,
monitoring
reflects
current
use
pattern,
underestimates
frequency
of
occurrence,
often
misses
peaks,
inputs
cannot
be
adjusted
as
modeled
ones
can,
usually
done
for
purposes
other
than
characterizing
exposure
from
a
particular
pesticide),
and,
consequently,
tend
to
complement
the
modeling
rather
than
refine
it.
In
general,
a
useful
interpretation
of
monitoring
values
requires
in­
depth
assessment
of
the
data,
which
is
beyond
the
scope
of
a
Tier
I
assessment.

Drinking
Water
Treatment
It
is
likely
that
primary
treatment
may
reduce
the
levels
of
cypermethrin
due
to
its
tendency
to
bind.
However,
there
is
no
information
available
at
this
time
to
determine
the
levels
of
reduction
(
Ref.
7).

CONCLUSIONS
The
following
can
be
concluded
about
bifenthrin:

C
This
is
a
Tier
I
level
analysis,
refinements
may
be
available
should
they
be
needed.
The
acute
levels
of
surface
drinking
waters
was
0.0140
ppb,
the
chronic
level
of
drinking
waters
was
0.0140
ppb
of
bifenthrin.
The
groundwater
concentration
of
cypermethrin,
suitable
for
acute
and
chronic
is
0.000300
ppb.
All
the
concentrations
were
limited
by
the
solubility
limit
of
bifenthrin.
It
was
assumed
that
the
maximum
application
rate
was
used
on
lettuce,
with
the
minimum
interval
between
applications.
The
major
uncertainty
is
presence
of
acetonitrile
in
several
of
the
laboratory
experiments.
Furthermore,
the
batch
equilibrium
constants
were
obtained
at
only
one
concentration
(
no
Freundlich
isotherms).

C
Despite
the
weaknesses
of
the
data,
this
is
considered
a
conservative
(
screening
level)
analysis.
APPENDIX
SCI­
GROW
and
FIRST
model
output
files.

RUN
No.
1
FOR
Bifenthrin
ON
Lettuce
*
INPUT
VALUES
*
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
RATE
(#/
AC)
No.
APPS
&
SOIL
SOLUBIL
APPL
TYPE
%
CROPPED
INCORP
ONE(
MULT)
INTERVAL
Koc
(
PPTr)
(%
DRIFT)
AREA
(
IN)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
.100(
.474)
5
7
275000.0
14.0
AERIAL(
16.0)
87.0
.0
FIELD
AND
RESERVOIR
HALFLIFE
VALUES
(
DAYS)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
METABOLIC
DAYS
UNTIL
HYDROLYSIS
PHOTOLYSIS
METABOLIC
COMBINED
(
FIELD)
RAIN/
RUNOFF
(
RESERVOIR)
(
RES.­
EFF)
(
RESER.)
(
RESER.)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
176.40
2
N/
A
.00­
.00
352.80
352.80
UNTREATED
WATER
CONC
(
NANOGRAMS/
LITER
(
PPTr))
Ver
1.0
AUG
1,
2001
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
PEAK
DAY
(
ACUTE)
ANNUAL
AVERAGE
(
CHRONIC)
CONCENTRATION
CONCENTRATION
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
14.000
14.000
SCIGROW
VERSION
2.3
ENVIRONMENTAL
FATE
AND
EFFECTS
DIVISION
OFFICE
OF
PESTICIDE
PROGRAMS
U.
S.
ENVIRONMENTAL
PROTECTION
AGENCY
SCREENING
MODEL
FOR
AQUATIC
PESTICIDE
EXPOSURE
SciGrow
version
2.3
chemical:
Bifenthrin
time
is
1/
18/
2006
10:
23:
25
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
Application
Number
of
Total
Use
Koc
Soil
Aerobic
rate
(
lb/
acre)
applications
(
lb/
acre/
yr)
(
ml/
g)
metabolism
(
days)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
0.100
5.0
0.500
2.57E+
05
130.5
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
groundwater
screening
cond
(
ppb)
=
3.00E­
03*
*
Estimated
concentrations
of
chemicals
with
Koc
values
greater
than
9995
ml/
g
are
beyond
the
scope
of
the
regression
data
used
in
SCI­
GROW
development.
If
there
are
concerns
for
such
chemicals,
a
higher
tier
groundwater
exposure
assessment
should
be
considered,
regardless
of
the
concentration
returned
by
SCI­
GROW.
************************************************************************
Molecular
structure
of
BIFENTHRIN.

************************************************************************
References:
1.
Policy
Establishing
Current
Versions
of
Exposure
Models
and
Responsibility
for
Model
Maintenance
(
11/
06/
2002)
2.
SCIGROW:
Users
Manual
(
11/
01/
2001,
revised
08/
23/
2002)
3.
FIRST
Users
Manual
(
08/
01/
2001)
4.
FIRST:
A
Screening
Model
to
Estimate
Pesticide
Concentrations
in
Drinking
Water
(
05/
01/
2001)
5.
Guidance
for
Selecting
Input
Parameters
in
Modeling
the
Environmental
Fate
and
Transport
of
Pesticides,
Version
II
(
02/
28/
2002)
6.
Use
of
the
Index
Reservoir
and
Percent
Crop
Area
in
EFED
Drinking
Water
Assessments
(
12/
01/
1999)
7.
The
Incorporation
of
Water
Treatment
Effects
on
Pesticide
Removal
and
Transformations
in
Food
Quality
Protection
Act
(
FQPA)
Drinking
Water
Assessments
(
10/
25/
2001)
8.
Laskowski,
D.
A.
2002.
Rev.
Environ.
Contam.
Toxicol.
174:
49­
170
9.
Tomlin,
C.
editor.
1994.
The
Pesticide
Manual
10th
Edition.
British
Crop
Protection
Council
and
Royal
Society
of
Chemistry,
UK.
