MEMORANDUM

DATE:	August 11, 2010

SUBJECT:	Tier I Estimated Environmental Concentrations of Bifenthrin for
the Use in the Human Health Risk Assessment; IR-4 Petition for the Use
of the Chemical on Grass, Forage and Hay (PC Code 128825; DP Barcode
D372556)

TO:		Laura Nollen, Risk Manager Reviewer

		Barbara Madden, Review Manager #05

		Daniel (Dan) Rosenblatt, Chief

		Minor Use Branch

		Registration Division (7505P)

and:		William Irvin, Risk Assessor

Jack Arthur, Chief

		Registration Action Branch V

		Health Effects Division (7509P)

		Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

THROUGH:	Mah T. Shamim, Ph.D., Chief

Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

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 registrant is proposing the uses on grass, forage and hay.  Based on
an inspection of the new uses of bifenthrin, it was found that lettuce
still represents the scenario with the highest EDWCs, and, therefore,
the drinking waters assessment results do not change from the previous
ones.  For electronic copy of the last assessment see Attachment A.

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 14.0 ppt of
bifenthrin, based on applications of the chemical to lettuce.  The
cancer/ chronic drinking water concentration is 14.0 ppt (based on
applications of lettuce, with the highest application rate and PCA). 
The SCI-GROW generated EDWC is 3.00 ppt 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 14.0 ppt
(the solubility of bifenthrin).  Should there be a need for additional
refinements, the EFED can perform a Tier II aquatic assessment, for
surface waters.

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)  ( ppt) 

Groundwater (SCI-GROW)	Lettuce (0.5 lb. a.i./A/season)	Acute and Chronic
3.00

Surface water  (FIRST)	Lettuce (0.5 lb. a.i./A/season)	Acute	14.0

	Lettuce (0.5 lb. a.i./A/season)	Chronic	            14.0           



Use Characterization

Table 2 provides a summary of the new use proposed in this action for
bifenthrin.  The use information was obtained from the proposed
supplemental labels for Brigade 2EC Insecticide/ Miticide and Brigade
WSB Insecticide/ Miticide.

  SEQ CHAPTER \h \r 1 Table 2.  Summary of new uses for bifenthrin,
based on the proposed supplemental labels for Brigade 2EC Insceticide/
Miticide (EPA Reg. No. 279-3313) and Brigade WSB Insecticide/ Miticide
(EPA Reg. No. 279-3108).

USE	SINGLE  APP. RATE   (lb a.i./A)	NUMBER OF APPS.	SEASONAL APP. RATE
(lb a.i./A)	INTERVAL BETWEEN APPS. (days)	APP. METHOD	INCORPO-RATION
DEPTH (inches)	PHI

Grass Forage, Fodder, and Hay Group and Grass Grown for Seed, Pasture
and Rangeland (including bahiagrass, barnyardgrass, bentgrass,
Bermudagrass, Kentucky bluegrass, big blueastem, smooth bromegrass,
buffalograss, reed canarygrass, centipedegrass, crabgrass, cupgrass,
dallisgrass, sand dropseed, Kentucky fescue, meadow foxtail, eastern
gramagrass, side-oats grama, guinea grass, Indian grass, Johnsongrass,
lovegrass, napiergrass, oatgrass, orchardgrass, pangolagrass, paspalum,
redtop, Italian ryegrass, St. Augustine grass, sprangletop,
squirreltailgrass, stargrass, switchgrass, timothy, crested wheatgrass,
wildrye grass and zoysia grass.  Also included are sudangrass and
sorghum forages and their hybrids.)	0.033-0.20	Not specified	0.2	14	G or
A	0	30 for forage and hay

Attachment A: PREVIOUS DWA FOR BIFENTHRIN



UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

                                                                     
OFFICE OF 

                                                                 
PREVENTION, PESTICIDES AND

                                                                   
TOXIC SUBSTANCES

  SEQ CHAPTER \h \r 1 					PC Code 	128825

				 DP Barcode	D334155, D334162,

						D334166, D334169

MEMORANDUM

DATE:	February 7, 2007

SUBJECT:	Tier I Estimated Environmental Concentrations of Bifenthrin for
the Use in the Human Health Risk Assessment;  IR-4 Petition for the Use
of the Chemical on Vegetable Roots (except for sugar beet and garden
beet, Subgroup 1B), Beets, Radish, Pistachio, Peanuts, Soybean, Fruiting
Vegetables (Subgroup 8), and Mayhaw

TO:		Shaja Brothers, Risk Manager Reviewer

		Daniel Rosenblatt, Chief

		Barbara Madden, Chief

		Minor Use Branch

		Registration Division (7505P)

AND:		PV Shaw, Chief

		Registration Action Branch I

		Health Effects Division (7509P)

FROM:	José Luis Meléndez, Chemist

		Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

THROUGH:	Mah T. Shamim, Ph.D., Chief

Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

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. 
Based on an inspection of all the uses of bifenthrin, it was found that
lettuce is still the use with the major exposure and the highest PCA,
and, therefore, the drinking waters assessment results do not change
from the previous ones.  An electronic copy of the previous assessment
is attached.

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, with the highest application rate and PCA). 
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 (that is, 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.

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

Surface water  (FIRST)	Lettuce (0.5 lb. a.i./A/season)	Acute	0.0140

	Lettuce (0.5 lb. a.i./A/season)	Chronic	              0.0140           



Use Characterization

Table 2 is an updated summary of all agricultural use patterns for
bifenthrin.  The highlighted uses are those proposed new ones.  The use
information was obtained from the proposed labels for Capture 2EC
Insecticide/ Miticide, Brigade WSB Insecticide/ Miticide and Capture
1.15G Insecticide/ Miticide.

  SEQ CHAPTER \h \r 1 Table 2.  Updated summary use information for
bifenthrin, based on the proposed labels for Capture 2EC Insecticide/
Miticide (EPA Reg. No. 279-3069), Brigade WSB Insecticide/ Miticide (EPA
Reg. No. 279-3108) and Capture 1.15G Insecticide/ Miticide (EPA Reg. No.
279-3244).

USE	SINGLE  APP. RATE   (lb a.i./A)	NUMBER OF APPS.	SEASONAL APP. RATE
(lb a.i./A)	INTERVAL BETWEEN APPS. (days)	APP. METHOD	INCORPO-RATION
DEPTH (inches)	PHI

Cotton*	0.1	5	0.5	          3	Ground, aerial or ULV	0	14

Field corn (grain and silage), popcorn, field corn grown for seed-at
plant use	0.08	Not specified	0.1	Not specified	In furrow	0	N/A

Field corn (grain and silage), popcorn, field corn grown for seed-pre
emergence (PRE) or pre-plant incorporated (PPI)	0.062            

0.040	1	0.062             

0.040	N/A	PPI            

PRE	PPI-not deeper than 3 in.

PRE-not specified	N/A

Field corn (grain and silage), popcorn, field corn grown for seed	0.1	3
0.3 including at plant, PPI and PRE	Not specified	Ground or aerial	0	30

Sweet corn, sweet corn grown for seed-at plant use	0.08-0.1	Not
specified	0.1	Not specified	In furrow; granules must be incorporated
into the top 1”	0-1”	N/A

Sweet corn, sweet corn grown for seed	0.1	2	0.2	Not specified	Ground or
aerial	0	1; 18 for corn that is hand harves-ted

Succulent peas and beans: Pea (Pisum spp.) dwarf pea, edible-pod pea,
English pea, garden pea, green pea, snow pea, sugar snap pea, Pigeon pea
       Bean (Phaseolus spp.) broadbean (succulent), lima bean (green),
runner bean, snap bean, wax bean    Bean (Vigna spp.) asparagus bean,
blackeyed pea, Chinese longbean, cowpea, mothpea, Southern pea, yardlong
pea       Jackbean Soybean (immature seed) Sword bean	0.1	2	0.2	Not
specified	Ground or aerial

May be applied in furrow with the seed or transplant for fireworm	0	3, 
9 for peas/ beans that are hand harves-ted

Dried shelled peas and beans: bean (Lupinus); bean (Phaseoulus) field,
kidney, lima, navy, pinto, tepary; bean (Vigna) adzuki, blackeyed,
catjang, cowpea, crowder pea, moth, mung, rice, southern, urd; broad
bean (dry); chickpea; guar; lablab bean; lentil; pea (Piscum), field
pea; pigeon pea	0.1	2	0.2	Not specified	Ground or aerial	0	14

Head and Stem Brassica Vegetables including: broccoli, Chinese broccoli,
Brussels sprouts, cauliflower, cavalo broccolo, kohlrabi, cabbage,
Chinese cabbage (napa), Chinese mustard cabbage (gai choy)	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: chayote, citron melon, cucumber, gherkin, edible ghourd
(various), muskmelon (various, for example cantaloupe and pineapple
melon), pumpkin, summer squash (various), winter squash (various),
watermelon (includes hybrids)	0.1	3	0.3	7	Ground or aerial	0	3

Lettuce, head	0.1	5	0.5	7	Ground or aerial	0	7

Caneberries including blackberriesbingleberrie dewberries lowberries
marion-berries olallie-berries young-berries loganberrie raspberries	0.1
2	0.2	One pre-bloom and one post-bloom	Ground or aerial	0	3

Artichoke	0.1	5	0.5	15	Ground or aerial	0	5

Hops*	0.1	3	0.3	21	Ground or aerial	0	14

Pears	0.2	~2.5	0.5	30	Ground or aerial	0	14

Eggplant	0.1	2	0.2	9	Ground or aerial	0	9

Citrus	0.25

0.5	2

1	0.5

0.5	Early and late season

N/A	Ground

Ground	0

0	1

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: broccoli raab, bok choy, collards, kale, mizuna,
mustard greens, mustard spinach, rape greens	0.1	4	0.4	7	Ground or
aerial	0	7

Tuberous and corm vegetables: potato, sweet potato, arracacha,
arrowroot, Chinese artichoke, Jerusalem artichoke, edible canna,
cassava, chufa, dasheen, ginger, leren, tanier, turmer, yam bean, true
yam	0.3 in furrow at planting; 0.15 as  lay-by;        and 0.1 foliar
nmt 2 foliar applications	0.5 including soil applications	21 for foliar
applications	In furrow, lay-by  and foliar treatments	0	21

Cilantro (coriander)	0.1	5	0.5	7	Ground or aerial	0	3

Okra	0.1	2	0.2	7	Ground or aerial	0	7

Strawberries	0.2	~2.5	0.5	7	Ground or aerial	0	0

Tree nut crop: almond, beech nut, Brazil nut, Butternut, cashew,
chestnut, chinquapin, filbert (hazelnut), hickory nut, macadamia nut
(bush nut), pistachio, walnut (black and English)	0.2	~2.5	0.5	15	Ground
or aerial	0	7

(21 for pecans)

Root Crops: carrots, celeriac, turnip rooted chervil, chicory, ginseng,
horseradish, turnip rooted parsley, parsnip, radish, oriental radish,
rutabaga, salsify, black salsify, Spanish salsify, skirret, turnip
(0.006 lb ai/linear ft)

0.1	1 in furrow application at planting

5	

0.5	

7	In Furrow and Foliar	

0	

21

Root Crops: Garden Beets	0.1	4	0.4	7	Foliar	0	1

Soybeans	0.1	3	0.3	30	Foliar	0	18

Fruiting Vegetables: Eggplant, pepper (bell and non-bell), groundcherry
pepino	0.1	2	0.2	7	Ground or aerial	0	7

Fruiting Vegetables:    tomato, tomatillo	0.1	4	0.4	10	Ground or aerial
0	1

Peanut	0.1	5	0.5	14	Foliar	0	14

Mayhaw	0.1	2	0.2	7	Foliar	0	30

*Not for use in California.



UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

                                                                     
OFFICE  OF 

                                                                 
PREVENTION, PESTICIDES AND

                                                                   
TOXIC SUBSTANCES

COPY

								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   SEQ CHAPTER \h \r 1
2-methylbiphenyl-3-ylmethyl
(Z)-(1RS,3RS)-3-(2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-dimethylcyclop
ropanecarboxylate, CAS# 82657-04-03, PC code 128825)  SEQ CHAPTER \h \r
1  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.

  SEQ CHAPTER \h \r 1 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

Surface water  (FIRST)	Lettuce (0.5 lb. a.i./A/season)	Acute	0.0140

	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 (pre-treatment) 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.

  SEQ CHAPTER \h \r 1 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

Lettuce, head	0.1	5	0.5	7	Ground or aerial	0	7

Caneberries	0.1	2	0.2	One pre-bloom and one post-bloom	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

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.

  SEQ CHAPTER \h \r 1 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-dimethylcyclop
ropanecarboxylate	–	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.

  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.	- -



  SEQ CHAPTER \h \r 1 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 μg/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.

ansformation products (≥10% of the applied) were observed.

Table 4.  Summary of degradate formation from degradation of bifenthrin.

STUDY TYPE	SOURCE	DEGRADATE and MAXIMUM CONCENTRATION



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 over-estimated 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.

  SEQ CHAPTER \h \r 1 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.

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

Surface water  (FIRST)	Lettuce (0.5 lb a.i./A/season)	Acute	0.0140

	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 crop-specific 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:

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).

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:

Policy Establishing Current Versions of Exposure Models and
Responsibility for Model Maintenance (11/06/2002)

SCIGROW: Users Manual (11/01/2001, revised 08/23/2002)

FIRST Users Manual (08/01/2001)

FIRST: A Screening Model to Estimate Pesticide Concentrations in
Drinking Water (05/01/2001)

Guidance for Selecting Input Parameters in Modeling the Environmental
Fate and Transport of Pesticides, Version II (02/28/2002) 

  SEQ CHAPTER \h \r 1 Use of the Index Reservoir and Percent Crop Area
in EFED Drinking Water Assessments (12/01/1999) 

The Incorporation of Water Treatment Effects on Pesticide Removal and
Transformations in Food Quality Protection Act (FQPA) Drinking Water
Assessments  (10/25/2001)

Laskowski, D.A.  2002.  Rev. Environ. Contam. Toxicol. 174:49-170

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

