Document ID: EPA-HQ-OPP-2012-0420-0006
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2013-12-27T05:00Z

U. S. ENVIRONMENTAL PROTECTION AGENCY

Washington, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

PC Code: 067710

DP Barcode: 402100

MEMORANDUM	November 6, 2012

SUBJECT:	Tier II Drinking Water Assessment for the New Use Registration
of Indoxacarb on Dry Beans, Snap Beans, Small Fruit Vine Climbing
Subgroup 13-07F and Low-Growing Berry Subgroup 13-07H.

TO:		 	Laura Nollen, Risk Manager Reviewer

			Barbara Madden, Risk Manager

			Registration Division (7505P)

	Mike Metzger

	Risk Assessment Branch 5

	Health Effects Division (7509P)

	

	

FROM:	Christopher M. Koper, Chemist

	Environmental Fate and Effects Division (7507P)

THROUGH:	He Zhong, Ph.D., Biologist

	Sujatha Sankula, Ph.D., Lead Biologist

	Ed Odenkirchen, Ph.D., Acting Branch Chief

	Environmental Fate and Effects Division (7507P)EXECUTIVE SUMMARY

A Tier II screening-level drinking water assessment was conducted to
support the human health risk assessment for the proposed new use
registration for indoxacarb.  Modeled application rates represent the
maximum application rates from the proposed labels (DuPont ™ Avaunt®,
EPA Reg. No. 352-597 and DuPont ™ Steward® EC,  EPA Reg. No. 352-638)
for use on dry beans, snap beans, small fruit vine climbing subgroup
13-07F and low-growing berry subgroup 13-07H.  For dry and snap beans
and the low-growing berry subgroup, the proposed maximum application
rate is 0.44 lbs. a.i./acre (4 applications at 0.11 lbs. a.i./acre). 
For cranberry and the small fruit vine climbing subgroup, the proposed
maximum application rate is 0.22 lbs. a.i./acre (2 applications at 0.11
lbs. a.i./acre).  In addition, aerial and ground foliar spray
applications and chemigation techniques are the proposed application
methods.  

Blockage of the neuronal sodium channel produces the insecticidal mode
of action of indoxacarb.  The insecticidal activity of the compound is
believed to be attributed to the rapid and extensive conversion of
indoxacarb in insects to a more active metabolite (IN-JT333).  In
insects, IN-JT333 has greater affinity for the sodium channel complex
compared to the parent compound.  Indoxacarb exists as an isomer pair
taking form as the active (S) isomer and inactive (R) isomer.  The major
routes of degradation of indoxacarb include alkaline-catalyzed
hydrolysis, photodegradation in water, and microbial mediated
degradation.  

A cumulative residue modeling approach was used to account for the
environmental fate and transport of indoxacarb plus degradation products
with toxicological concern (IN-JT333, IN-KG4333, IN-KT413, IN-ML437-0H)
(USEPA 2000).  The Metabolism Assessment Review Committee (MARC) of the
Health Effects Division (HED) reviewed the degradate structures to
determine residues of concern.  Based on the MARC memorandum, a Total
Toxic Residue (TTR) approach (Table 1) should be applied for the parent
indoxacarb and the degradation products with toxicological concern
(IN-JT333, IN-KG4333, IN- KT413, IN-ML437-0H) for the drinking water
assessment.    

Table 1.  Total Toxic Residue (TTR) Expression

Matrix:	Residues of Concern:	Structure:

Drinking Water 	Indoxacarb

((S) active isomer)

 

Based on MARC decision memorandum (D267726)

The recommended estimated drinking water concentrations (EDWCs) for the
human health risk-assessment are based on highest predicted value for
surface water and groundwater (Table 2), which are based on two
applications of 0.11 lbs. a.i./acre/season on cranberry and four
applications of 0.11 lbs. a.i./acre on beans and berries respectively.

Table 2.  Recommended Estimated Drinking Water Concentrations (EDWCs)1
for Surface Water and Ground Water 

Drinking Water Source	Model

Scenario	Method2	Maximum 

Application Rate

(interval between applications)	1-in-10 year acute (µg/L)	1-in-10 year
chronic (µg/L)	30- year average (µg/L)

Surface Water	Provisional Cranberry Model

Cranberry	PCM	2 app @ 0.11 lb a.i./acre	59.26	18.48	18.48

Ground Water	SCI-GROW

(Beans, Berries)	--	4 app @ 0.11 lb a.i./acre	0.33	0.33	0.33

1 For surface water (PRZM/EXAMS), EDWC values adjusted with a Percent
Cropped Area (PCA) factor of 0.87.  For ground water (SCI-GROW), no PCA
adjustment was utilized.  

2  PCM = The Provisional Cranberry Model (PCM) is a provisional
refinement to the Tier I Rice Model (v1.0, May 8, 2007).   Refinements
include the addition of simple degradation processes in dry and flooded
conditions and a water depth of twelve inches, rather than the water
depth of four inches used in the rice model. These modifications allow
estimation of screening-level peak and annual mean EDWCs of residues of
concern that may occur in untreated surface water used as drinking water
following use on cranberries.

PROBLEM FORMULATION

A Tier II drinking water assessment (DWA) utilized modeling to estimate
the surface water and groundwater concentrations of indoxacarb in
drinking water source water (pre-treatment) resulting from use on
vulnerable sites.  No monitoring data are available for indoxacarb at
the time of this assessment.

While Tier I DWAs are designed to screen out chemicals with low
potential risk for posing a drinking water concern, the Tier II
assessment provides more site-specific, refined modeling estimates of
exposure by using additional environmental fate parameters, specific
soil data, weather information, and management practices to estimate
daily concentrations for an extended period of time (up to 30 years). 
This Tier II surface water assessment reflects application of indoxacarb
at the maximum label rate and with scenarios intended to be
representative of an environment that is more vulnerable to runoff and
leaching than where most of the assessed commodities may be present.

Background

Indoxacarb insecticidal mode of action is the blockage of the insect’s
neuronal sodium channels.  The insecticidal activity of the compound is
believed to be attributed to the rapid and extensive conversion of
indoxacarb to a more active metabolite (IN-JT333).  In insects, IN-JT333
has greater affinity for the sodium channel complex compared to the
parent compound.  Indoxacarb was initially registered in October 2000
for control of certain lepidopteran pests including beat army worm and
is also considered an organophosphate (OP) replacement.  

Use Characterization

The registrant is seeking new use registration on dry beans, snap beans,
small fruit vine climbing subgroup 13-07F and low-growing berry subgroup
13-07H.  For dry and snap beans and the low-growing berry subgroup, the
proposed maximum application rate is 0.44 lbs. a.i./acre (4 applications
at 0.11 lbs. a.i./acre).  For cranberry and the small fruit vine
climbing subgroup, the proposed maximum application rate is 0.22 lbs.
a.i./acre (2 applications at 0.11 lbs. a.i./acre).   The proposed
application methods are aerial and ground foliar spray applications and
chemigation techniques.  The maximum proposed uses of indoxacarb can be
found in Table 3.  

Table 3. Application Information for the Proposed New Uses of Indoxacarb

Use Pattern	Formula	Application Method	PHI (days)	Application Interval 
  (days)	Maximum Single Application Rate (lbs. a.i./acre)	Maximum Number
of Applications (season)	Seasonal Maximum Application Rate 

(lbs a.i./acre)

Beans

(Dry)	DuPont™ Avaunt®	Foliar 

Chemigation	7	7	0.11	

4

	0.44

Beans

(Snap)	DuPont™ Avaunt®	Foliar 

Chemigation	7	3	0.11	

4

	0.44

Low-Growing Berry	DuPont™ Avaunt®	Foliar 

Chemigation	30	7	0.11	

4

	0.44

Small Fruit Vine Climbing	DuPont™ Avaunt®	Foliar 

Chemigation	7	21	0.11	

2

	0.22

Beans (Dry)	DuPont™ Steward®EC	Foliar 

Chemigation	7	7	0.11	

4

	0.44



2.3.	Conceptual Model 

Risk hypothesis

The following risk hypothesis is being employed for this national-scale
drinking water assessment:

Indoxacarb, when used in accordance with proposed labels, can result in
off-site movement of the chemical through runoff after rain events, soil
and possible wind erosion, and spray drift, leading to human exposure
through consumption of contaminated drinking water.  

Conceptual model

The source of the stressor is the insect sodium channel blocker,
indoxacarb.   The mechanisms of release of indoxacarb are foliar aerial
and ground applications, as well as through chemical irrigation systems
(chemigation).  Environmental transport of indoxacarb can occur through
surface water runoff after rain events, soil and possible wind erosion
and spray drift.   Leaching into groundwater is not expected to be a
major dissipation pathway based on submitted batch equilibrium, aged
soil column leaching and terrestrial field dissipation studies which
showed that indoxacarb having a low potential to leach.  Surface water
runoff from the areas of application is assumed to follow topography. 
Spray drift will follow the wind directions.  Potential emission of
volatile compounds is not considered as a viable release mechanism for
indoxacarb, since volatilization is not expected to be a significant
route of dissipation for this chemical because of the low vapor pressure
and Henry’s Law constant of the compound. 

ANALYSIS

Environmental Fate and Transport Characterization

proposed Dupont™ Avaunt® insecticide contains 30% of active
ingredient of (S) isomer of Indoxacarb which is formulated as a water
dispersible granule formulation. In addition, the proposed Dupont™
Steward® EC insecticide contains 15.84% of active ingredient of (S)
isomer of Indoxacarb which is formulated as an emulsifiable concentrate.
  Most of the environmental fate studies were carried out with the
either one of two older formulations: DPX-JW062 with a 50:50 (S: R)
racemic mixture and DPX-MP062 with a 75:25 (S:R) racemic mixture. 

The following fate and transport characterization is for indoxacarb
(parent) only. The half lives differ in Table 4 because of the total
toxic residue (TTR) approach recommended by the MARC memorandum
(D267726).  More information regarding the TTR approach including
calculations can be found in the original assessment (USEPA 2000).  

The major routes of degradation for indoxacarb (DPX-JW062) are
alkaline-catalyzed hydrolysis, photodegradation in water, and microbial
mediated degradation.  Appendix III summarizes indoxacarb’s
degradation profile, including maximum percent formation.  DPX-JW062 had
abiotic hydrolysis half-lives of 519 days in pH 5 buffer solution, 38
days in pH 7 buffer solution, and 1 day in pH 9 buffer solution (MRID
44477301).  The major hydrolysis degradation product was IN-KT413 (48%).
 Additional abiotic hydrolysis data indicate indanone and
trifluroromethoxyphenyl labeled DPX-MP062 (3S: 1R ratio) had hydrolysis
half-lives of 577.62 days in pH 5 buffer solution, 21.80 days in pH 7
buffer solution, and 1.11 days in pH 9 buffer solution (MRID 45795801). 
Major degradation products included IN-KT413 (88.1%) and IN-MF014
(14.7%).  A supplementary hydrolysis study showed the enantiomeric ratio
of the isomers of indoxacarb remained constant during the study.    

	

The photodegradation half-life for DPX-JW062 was 3.16 days in pH 5
buffer solution (MRID 44477302). Major degradation products included
IN-KB687 (22.1%) and IN-MF014 (37.8%) for phenyl labeled DPX-JW062 and
IN-MH304 (19.9%) and MW297 (14.1%) for indanone labeled indoxacarb. 
Additional aqueous photolysis data indicate DPX-MP062 had a
environmental phototransformation half-life of approximately 5 days
(MRID 45795802).  Major photodegradation products were identified as
IN-MH304 (32.3%), IN-CO639 (10.2%) and IN-MA573 (19.9%) for indanone
labeled indoxacarb; and IN-MF014 (37.6 %), IN-KB687 (28.7%) for phenyl
labeled indoxacarb.   Additionally, numerous unidentified polar and
non-polar degradation products were found for both labels of indoxacarb.
A supplementary photodegradation study showed the enantiomeric ratio of
the isomers of indoxacarb remained constant during the study.     

	

The extent of DPX-JW062 photodegradation on soil is questionable because
there was extensive degradation in dark controls with similar
degradation products (MRID 44477303).  The dark control corrected
half-life was 126 days.  The major degradation product was IN-KB687
(22%).

	

DPX-JW062 degraded with half-lives ranging from 3 to 693 days in aerobic
soil metabolism studies (MRIDs 44477304, 45166303, 457950803, 45795812,
45906701).  Maximum formation rates for major degradates included
IN-JT333 (18.6% - 45906701), IN-KG433 (39.7% - 45166303), IN-JU873
(12.9% - 45166303), IN-ML438 (9.7% - 45166303), IN-MK643 (12% -
45166303, 44477304), IN-MK638 (28.1% - 45166303), IN-ML 437OH (13% -
44477304), IN-KB687 (11% - 44477304), CO2 (35.73% - 45795803) and
non-extractable residues (66.1% - 45906701).

DPX-JW062 degraded with half-lives ranging from 18 to 34 days in
near-neutral aerobic aquatic environments (MRID 44477306).  Maximum
formation rate for major degradates included IN-JT333 (10.5% of applied,
half-life of 54 days under aerobic soil conditions), Unknown A (24.1%),
CO2 (19%) and non-extractable residues (38%).  In addition, DP-MP062
degraded with total system half-lives of 30.7 and 21.3 days in a pond
water/sediment and lake water/sediment systems, respectively (MRID
45793301).  For the pond water/sediment system, maximum formation rates
for major degradation products included IN-KT413 (42.1%), IN-MP819
(10.3%) and IN-MS775 (12.8%).  In the lake water/sediment system,
maximum formation rates for major degradation products included IN-JT333
(25.7%), IN-KT413 (31.4%) and CO2 (25.8%).

DPX-JW062 degraded with half-lives of 147 and 231 days in anaerobic
soil-water environments (MRID 44477305).   Maximum formation rate for
major degradates included IN-JT333 (28.2% of applied), IN-KT413 (16.0%)
and non-extractable residues (43%).  In addition, DPX-JW062 degraded
with total system half-lives of 192 and 315 days for the indanone and
phenyl label indoxacarb, respectively, in a flooded-silt loam sediment
system (MRID 45795804).  Similarly, major degradates included IN-JT333
and IN-KT413 (16.0%).  Enantiomeric ratios of the R and S isomers
remained constant during the study.

Degradation products of indoxacarb had different half-lives in aerobic
soils.  IN-KT413 and IN-MK638 were non-persistent (t1/2 1.3 to 16.2
days) in foreign and US mineral soils (MRID 45906703, 45795816). 
IN-KG433 and IN-JU873 were non-persistent to moderately persistent (t1/2
10.5 to 58.7 days) in aerobic soils (MRIDs 45795815 and 45795814). In
contrast, IN-MK643 was persistent (t1/2 141.5 to 346.6 days) in aerobic
soils (MRID 45795817).  Degradation products except for CO2 were not
identified.  However, the degradation pathways were generally associated
with oxidative mineralization to CO2 and residue incorporation into
non-extractable soil organic matter.      

The results of batch equilibrium studies suggest low mobility of
DPX-JW062 and IN-JT333 in terrestrial and aquatic environments. 
Reviewer calculated soil: water partition coefficients for DPX-JW062 are
29 ml/g in Myaka sand soil, 30 ml/g in Donna sandy clay loam soil, 99
ml/g in Chino loam soil, and 40 ml/g in a Tama silt loam soil (MRIDs
44477308 and 45795809).  Soil: water partition coefficients for IN-JT333
are 251 ml/g in Myaka sand soil, 115 ml/g in Donna sandy clay loam soil,
308 ml/g in Chino loam soil, and 147 ml/g in a Tama silt loam soil. 
There was no correlation between soil organic matter content and
indoxacarb soil: water partitioning coefficients.  The calculated Kds
for indoxacarb degradation products (IN-KT413, IN-KG433, IN-MK638, and
IN-MK643) ranged from 1.2 to 11.3 ml/g in five US and foreign mineral
soils (MRIDs 45795808, 45906702, 45795807, 45795806).  In contrast, the
calculated Kds for IN-JU873 ranged from 52.1 to 406.4 (MRID 45795805). 
With an exception of IN-JU873, the batch equilibrium data suggest
indoxacarb degradation products may exhibit some mobility in soil.  Aged
soil column leaching studies, however, indicate aged residues of
DPX-MP062 have low mobility in packed soil columns (MRID 44477309).

Plant and soil volatility studies indicate that DPX-JW062 has low
volatility from plant and soil surfaces, since after 168 hours of
incubation, < 3% of applied radioactivity had volatilized from lettuce
plants and soil surface (MRID 44491703).  

For DPX-JW062, at 10 and 100 ug/L concentrations, the calculated fish
bioconcentration factors were 395 to 504X for edible tissues, 1568-2081X
for nonedible tissues, and 1044-1351X for whole fish tissues,
respectively (MRIDs  44477319 and 45805301).   When based on residues of
the active isomer, DPX-KN128, maximum BCFs were 24 in fillet, 153 in
viscera, and 90 in whole fish for the 10 ppb exposure.   The major
degradation product in fish tissues (>10% recovered) was IN-JT333. 
Minor degradation products (<10% recovered) were IN-ML811, IN-KT319,
IN-KG433, and IN-JU873.  The depuration half-life of bioaccumulated
indoxacarb 14C residues ranged from 6.55 to 7.88 days.

For DPX-JW062 applied at 0.6 lbs ai/A on bare sand soil, the calculated
field dissipation half-lives ranged from 72 to 79 days in Florida and
California, respectively (MRIDs 44477312, 44477315 and 44477316).  Field
studies on bare ground soils using radiolabeled DPX-JW062 and with 0.88
lb a.i./A application rate indicated field dissipation half-lives
ranging from 29 to 113 days in Delaware and Texas and 73 to 119 days in
California and Florida, respectively (MRIDs 44477311 and 45850002 ). 
The degradate IN-JT333 was detected in all field studies.  The degradate
IN-KG433 was only detected in the radiolabeled field studies.  Some
leaching of parent and residues occurred but were not detected below 45
cm (18 inches).

Drinking Water Exposure Modeling

Estimated drinking water concentrations (EDWCs) were generated using
EFED’s standard suite of models.  Since there is no standard scenario
to model berry, the specialty Oregon Berry OP scenario was utilized.  In
addition, the Provisional Cranberry Model was utilized to model
cranberry.  The maximum application rate for the proposed new uses was
modeled.  

Models

Pesticide Root Zone Model (PRZM v3.12.2, May 12, 2005) and Exposure
Analysis Modeling System (EXAMS v2.98.04.06, April 25, 2005) are
simulation models coupled with the input PE5.pl shell (PE5, PE Version
5.0, November 15, 2006) to generate EDWCs of indoxacarb residues that
may occur in surface water used as drinking water.  The PRZM model
simulates pesticide movement and transformation on and across the
agricultural field resulting from crop applications.  The EXAMS model
simulates pesticide loading via runoff, erosion, and spray drift
assuming a standard watershed of 172.8 ha that drains into an adjacent
standard drinking water index reservoir of 5.26 ha, an average depth of
2.74 m.  A more detailed description of the index reservoir watershed
can be found in Jones et al., 1998.  The coupled PRZM/EXAMS model and
users manuals may be downloaded from the U.S. Environmental Protection
Agency (EPA) Water Models web-page (USEPA, 2011).  Percent Crop Areas
(PCA) that account for the maximum area within a watershed that may be
planted with the modeled crop are applied to concentrations predicted by
PRZM/EXAMS.

Screening Concentration in Ground Water (SCI-GROW v2.3, Jul. 29, 2003)
is a regression model used as a screening tool to estimate pesticide
concentrations found in ground water used as drinking water.  SCI-GROW
was developed by fitting a linear model to ground water concentrations
with the Relative Index of Leaching Potential (RILP) as the independent
variable.  Ground water concentrations were taken from 90-day average
high concentrations from Prospective Ground Water studies.  The RILP is
a function of aerobic soil metabolism and the soil-water partition
coefficient.  The output of SCI-GROW represents the concentrations of
residues that might be expected in shallow unconfined aquifers under
sandy soils, which is representative of the ground water most vulnerable
to pesticide contamination and likely to serve as a drinking water
source.  The SCI-GROW model and user’s manual may also be downloaded
from the EPA Water Models web-page (USEPA, 2011).  

The Provisional Cranberry Model is a provisional refinement to and based
on the same assumptions as the Tier I Rice Model (v1.0, May 8, 2007).
Refinements include the addition of simple degradation processes in dry
and flooded conditions and a water depth of twelve inches, rather than
the water depth of four inches used in the rice model.  These
modifications allow estimation of screening-level peak and annual mean
EDWCs of indoxacarb residues of concern that may occur in untreated
surface water used as drinking water following use on cranberries. 
Degradation of indoxacarb residues of concern on dry cranberry bog soil
is assumed to occur predominantly via aerobic microbial metabolism. 
Residue degradation in flooded bogs is assumed to occur via aerobic
microbial metabolism in the water column and via anaerobic microbial
metabolism in the sediment.

Cranberry bogs are not typically flooded until the night before
harvesting.  Because use of indoxacarb on cranberries is proposed for up
to two applications, each seven days apart, with a thirty-day
pre-harvest interval, the proposed single application rate (0.22 lbs
a.i./A) was aged on dry soil with the Provisional Cranberry Model for
two durations, applied at thirty seven and thirty days before harvest. 
The resulting residues (in lbs a.i./A) were then summed together and
input used as for the flooded component of the model to estimate peak
and annual mean EDWCs in bog tailwater following harvest.

The cranberry bog water depth of twelve inches is a maximum depth
recommended by the Cape Cod Cranberry Growers Association (2001). 
Previous assessments of mesotrione uses that employed the Provisional
Cranberry Model assumed a water depth of eighteen inches (DP barcode
339984, USEPA, 2004; DP barcode 325840, USEPA, 2006a), which is within
the range of water depths traditionally used.  However, modern water
conservation pressures are causing cranberry growers to reduce the flood
depth to fewer inches above the vertical cranberry branches, which grow
up to eight inches high (Cape Cod Cranberry Growers Association, 2001;
The Cranberry Institute, 2008).  Therefore, a twelve-inch deep flood is
a reasonable refinement to model assumptions.  The equations used in the
Provisional Cranberry Model are briefly described in Appendix II.  

Input Parameters

For dry and snap beans and low growing berries, the maximum application
rate (4 applications at 0.11 lbs. a.i./acre) was modeled to capture the
maximum EDWCs.  In addition, the maximum application rate (2
applications at 0.11 lbs. a.i./acre) was modeled for cranberries and the
small fruit vine climbing subgroup.  Foliar (aerial and ground) spray
applications and chemigation methods were modeled for these maximum use
rates.  

Application timing was based on the crop scenario’s harvest date,
pre-harvest interval (PHI), application interval and total number of
applications.  Chemical property input values were chosen according to
the current input parameter guidance (USEPA, 2009).  Standard PCAs were
used for all uses as estimates of the extent of watershed on which crops
are grown (Effland et al., 1999).  The default agricultural PCA of 0.87
was used for the proposed new uses because they are not confined to
specific regions of the U.S.  Actual fractions of cropped areas could be
less in some areas of the country.  

Input parameters and explanations for the PRZM/EXAMS and SCI-GROW and
Provisional Cranberry models are listed in Table 4, Table 5, and Table
6, respectively.  

	

Table 4.  PRZM/EXAMS Input Parameters for Indoxacarb

Input Parameter:	Value:	Comment:	Source:

Scenario(s):	Beans (Dry and Snap): 

MI Bean

Low Growing Berry: 

OR Berry

Cranberry

Small Fruit Vine Climbing: 

NY Grape	representative scenarios for each use	EFED Scenarios

Maximum Single 

Application Rate

lbs a.i./acre (kg a.i./ha)	All proposed uses: 

0.11  (0.124)

	proposed rate	Proposed labels

Applications per Year	Beans (Dry and Snap): 

4

Low Growing Berry: 

OR Berry:  4

Cranberry:  2

Small Fruit Vine Climbing: 

2	Label directions.  Label specifies rates per crop.  If there are
multiple crops grown per year, yearly rates may be higher. 

	Proposed labels

Application Interval (days)	Beans (Dry and Snap): 7

Low Growing Berry: 7

Small Fruit Vine Climbing: 21	Label directions	Proposed labels

Date of Initial Application

(scenario: day-month)	Bean (Dry): 

MI Bean:  07-08

Bean (Snap): 

MI Bean: 11-08

Low Growing Berry: 

OR Berry:  09-06

Small Fruit Vine Climbing: 

NY Grape:  17-09	For all crops, the date of initial application was
calculated from the harvest date from the crop profile and the
Pre-Harvest Interval (PHI) and number and interval of applications from
the proposed label.	Crop Scenarios and proposed labels

Application Method	Aerial (foliar)

Ground  (foliar)

Chemigation	label directions	Proposed labels

CAM Input	2  (foliar: aerial and ground)

1  (chemigation)

	(1) Soil applied, default incorporation depth, linearly decreasing with
depth (2) linear foliar based on crop canopy	US EPA, 2005

IPSCND Input	Beans (Dry and Snap): 2

Low Growing Berry: 3

Small Fruit Vine Climbing: 3	…remaining pesticide on foliage is (1)
converted to surface application to the top soil layer, (2) completely
removed after harvest, (3) is retained as surface residue and continues
to decay.	US EPA, 2005

Spray Drift Fraction	0.16  (aerial)

0.064  (ground)

0  (chemigation)	--	Input parameter guidance (USEPA, 2009) 

Application Efficiency	0.95  (aerial)

0.99  (ground)

1.0  (chemigation)	--	Input parameter guidance 

(USEPA, 2009)

Molecular Mass (g/mol)	527.8	--	Product Chemistry

Vapor Pressure at 25°C (torr)	1.9  x 10-10	--	Product Chemistry

Henry’s Law Constant

(atm-m3/mol)	1.6  x 10-10	--	Calculated from water solubility, vapor
pressure and molecular weight

Solubility in Water (mg/L)	0.8	pH 7 at 20°C	Product Chemistry

Organic Carbon Partition Coefficient (KOC) (L/kgOC)	400	Since this
assessment is based on cumulative residues, the mean value for IN-KG433
was used because it has the lowest non-sand Kf and Koc of the residues
of toxicological concern	MRID 45795806

Aerobic Soil Metabolism Half-life (days)	267	Rate Constant = 0.0026/day.
 Linear fitting techniques using the first order degradation model
provided a poor description of the data as shown by non-significant F
tests and R2. Therefore, nonlinear fitting techniques with the first
order decay model were used to estimate rate constants for indoxacarb
residue degradation.	MRID 44477304

MRID 44477307

Aerobic Aquatic Metabolism Half-life (days)	71	Rate Constant = 4.0 x
10-4/hour.  Non-linear fitting techniques were utilized as described in
ASM above.	MRID 44477306

Anaerobic Aquatic Metabolism Half-life (days)	577	Rate Constant = 5.0 x
10-5/hour.  Non-linear fitting techniques were utilized as described in
ASM above.	MRID 44477305

Hydrolysis Half-lives (days)	0  (stable)	Rate Constant = 1.5 x
10-4/hour.  Non-linear fitting techniques were utilized as described in
ASM above.	MRID 44477301

Aqueous Photolysis

Half-life (days)	0  (stable)	--	MRID 44477302

Table 5.  SCI-GROW Input Parameters for Indoxacarb

Input Parameter	Value	Comment	Source

Maximum Single Application Rate per growing season (lbs a.i./A)	0.11
maximum single application rate	Proposed labels

Applications per Year	4  (beans, berries)

	label directions	Proposed labels

Organic Carbon Partition Coefficient (KOC) (L/kgOC)	360	1 median value
of IN-KG433 degradate data because there was not a greater than a
three-fold variation among five values	MRID 45795806

Aerobic Soil Metabolism

Half-life (days)	267	2 Rate Constant = 0.0026/day.  	MRID 44477304

MRID 44477307

1 =  Individual Koc values for the degradate IN-KG433 (518, 360, 433,
348, 343).

2 =  Linear fitting techniques using the first order degradation model
provided a poor description of the data as shown by non-significant F
tests and R2. Therefore, nonlinear fitting techniques with the first
order decay model were used to estimate rate constants for idoxacarb
residue degradation.

Table 6.  Provisional Tier 1 Cranberry Model Input Parameters for
Indoxacarb

Input Parameter	Value	Source

Application Rate (lbs a.i./A)	0.11	Proposed label

Applications per Year	2	Proposed label

Organic Carbon Partition Coefficient (KOC) (L/kgOC)	400	Represents the
mean value for IN-KG433

Aerobic Soil Metabolism Half-life (days)	267	Rate Constant = 0.0026/day

Aerobic Aquatic Metabolism Half-life (days)	71	Rate Constant = 4.0 x
10-4/hour

Anaerobic Aquatic Metabolism Half-life (days)	577	Rate Constant = 5.0 x
10-5/hour

Modeling Results

The maximum use patterns were modeled to yield the maximum EDWCs for
surface water and groundwater (Table 7).  The recommended maximum EDWC
concentrations are as follows.  For surface water, cranberry yielded the
highest EDWCs.  The 1-in-10 yr annual peak (acute) concentration was
59.26 µg/L, the 1-in-10 yr annual mean (chronic) concentration was
18.48 µg/L and the 30-year annual mean (cancer chronic) concentration
was 18.48 µg/L.  For groundwater, based on the proposed highest annual
use rate for beans and berries, the SCI-GROW model estimated the
indoxacarb concentration at 0.33 µg/L.  Since these values are greater
than the previous established EDWCs for cotton (D293793, D355124), they
will supersede all previous EDWCs generated for indoxacarb.

Representative PRZM/EXAMS, SCI-GROW and Cranberry model outputs with
input parameter data are attached in Appendix I.

Table 7.  Indoxacarb Estimated Drinking Water Concentrations (EDWCs)1
for Surface Water and Ground Water based on selected Crop Scenarios

Proposed Label Use	PRZM/EXAMS

Scenario1

(first app date)	Method2	Maximum 

Application Rate

(interval between applications)	1-in-10 year acute (µg/L)	1-in-10 year
chronic (µg/L)	30- year average (µg/L)

DuPont™ Avaunt® and Steward® EC Insecticides

Surface Water

Beans (Dry)	MI Bean

(August 7)	A	4 app @ 0.11 lb a.i./acre

(7 days)	18.68	6.03	3.50

G

18.50	5.81	3.18

C

17.01	5.40	3.13

Beans (Snap)	MI Bean

(August 11)	A	4 app @ 0.11 lb a.i./acre

(7 days)	18.90	5.77	3.14

G

18.38	5.53	2.80

C

15.74	4.92	3.10

Low Growing Berry

(including Cranberry)	OR Berry3

(June 9)	A	4 app @ 0.11 lb a.i./acre

(7 days)	4.19	1.97	1.54

G

3.55	1.53	1.10

C

3.03	1.16	0.74

	Provisional Cranberry Model	--	2 app @ 0.11 lb a.i./acre

(7 days)	59.26	18.48	18.48

Small Fruit Vine Climbing Subgroup	NY Grape

(September 17)	A	2 app @ 0.11 lb a.i./acre

(21 days)	4.49	1.86	1.32

G

3.94	1.60	1.04

C

3.16	1.21	0.75

Ground Water

SCI-GROW	Bean

Berry	--	4 app @ 0.11 lb a.i./acre	0.33	0.33	0.33

1  For surface water (PRZM/EXAMS), EDWC values adjusted with a Percent
Cropped Area (PCA) factor of 0.87.  For ground water (SCI-GROW), no PCA
adjustment was utilized.  Bold numbers denote maximum EDWC values.

2  A = aerial application, G = ground application, C = chemigation.

3  Since there is no standard scenario to model berry, the specialty
Oregon Berry OP scenario was utilized.

Monitoring Data

There was no surface water or groundwater monitoring data available;
therefore, the surface water and ground water assessment was based
solely on the PRZM/EXAMS, SCI-GROW and Provisional Cranberry modeling,
respectively.  

3.2.5	Drinking Water Treatment

There is no available information on the drinking water treatment
effects on indoxacarb.

Uncertainties, Assumptions and Limitations

A major uncertainty in the assessment is the lack of environmental fate
data for the toxic transformation products of DPX-JW062 (Indoxacarb). 
In order to address this uncertainty, EFED has conducted the Tier II
modeling on the summed DPX-JW062 residues instead of individual
residues. This approach was taken because the environmental fate studies
were deficient in addressing the identification and fate of DPX-JW062
transformation products in the tolerance expression. In cases where the
environmental fate data did not adequately identify DPX-JW062 residues
such as the aerobic aquatic and anaerobic aquatic studies, the
half-lives were calculated on cumulative residues rather than the
summation of toxic DPX-JW062 residues.  

The cumulative residue modeling method assumes environmental fate
properties for indoxacarb and its degradation products (IN-JT333,
IN-KG4333, IN-KT413, IN-ML437-0H) are similar.  This modeling approach
provides a conservative assessment process for consideration of
simultaneous formation and decline of indoxacarb residues. 

Indoxacarb degradation can be characterized as a “hockey stick”
behavior with a rapid degradation rate followed by a slower degradation
rate. Selection of a suitable soil degradation half-life is difficult
due the large discrepancy of half-lives estimated using linearized
first-order degradation model and 2 parameter exponential decay model.

 Other uncertainties in the modeling are associated with the selection
of the most representative model for describing DPX-JW062 residue
degradation. Linear fitting techniques using the first order degradation
model (ln(y/a)=-bt) provided a poor description of the aerobic soil
metabolism data as shown by non-significant F tests and low coefficients
of determination (R2).  Therefore, nonlinear fitting techniques (as
employed through Sigmaplot-Regression Wizard) with the first order decay
model (y=ae -bx) were used to estimate rate constants for DPX-JW062
residue degradation. This fitting procedure was used to estimate the
degradation rate constants for hydrolysis, aerobic soil metabolism,
aerobic aquatic metabolism, and anaerobic aquatic metabolism. 

The lowest adsorption Koc coefficient of the toxic DPX-JW062 residues
(IN-KG433) was used to represent sorption in soil and aquatic
environments.  

The proposed label specifies rates per crop.  If there are multiple
crops grown per year, the yearly rate may be higher resulting in
underestimation of risk if the proposed commodities are grown more than
one crop per year.  

In general, the likelihood that multiple crops from the list of proposed
uses will be found within a single watershed where indoxacarb is used is
unknown; therefore, the default Percent Crop Area (PCA) of 0.87 was
utilized.   

Conclusions:

The Tier II drinking water exposure estimates are based on the
indoxacarb proposed new uses represented by the maximum use patterns
based on the proposed label.  Review of the surface water and
groundwater data, the Provisional Cranberry Model yielded the maximum
EDWCs in this assessment.  The 1-in-10 yr annual peak (acute)
concentration was 59.26 µg/L, the 1-in-10 yr annual mean (chronic)
concentration was 18.48 µg/L and the 30-year annual mean (cancer
chronic) concentration was 18.48 µg/L.  For groundwater, based on the
proposed highest annual use rate representing beans and berries, the
SCI-GROW model estimated the indoxacarb concentration at 0.33 µg/L.  

The estimated drinking water concentrations generated in this assessment
supersede all other values for indoxacarb since they represent the
highest concentrations to date.

REFERENCES

Cape Cod Cranberry Growers Association.  2001.  Cranberry Water Use: An
Information Fact Sheet.  

	June, 2001.  Online at:   HYPERLINK
"http://www.cranberries.org/pdf/wateruse.pdf" 
http://www.cranberries.org/pdf/wateruse.pdf 

Effland, W. R., N. C. Thurman, I. Kennedy.  1999.  Proposed Methods for
Determining Watershed-derived Percent Crop Areas and Considerations for
Applying Crop Area Adjustments to Surface Water Screening Models. 
Presentation to the FIFRA Science Advisory Panel, May 27, 1999.  

The Cranberry Institute.  2008.  About Cranberries.  2003-2008.  Online
at:   HYPERLINK "http://www.cranberryinstitute.org/about_cranberry.htm" 
http://www.cranberryinstitute.org/about_cranberry.htm 

Jones, R. D., S. Abel, W. R. Effland, R. Matzner, R. Parker.  1998.  An
Index Reservoir for Use in Assessing Drinking Water Exposure.  Proposed
Methods for Basin-scale Estimation of Pesticide Concentrations in
Flowing Water and Reservoirs for Tolerance Reassessment.  Presentation
to FIFRA Science Advisory Panel, June 29-30, 1998.  

USEPA  2000.  Index Reservoir Drinking Water Assessment for DPX-JW062
{(R,S)-methyl-7-chloro-2,5-dihydro-2-[(methylcarbonyl)[4-(trifluorometho
xy) phenyl]
amino]carbonyl]indeno[1,2-e][1,3,4]oxadiazine-4a(3H)-carboxylate} and
its Transformation Products.  DP 267726. 

USEPA.  2004.  Wolf, J.  Section 18 Request for Use of Mesotrione on
Cranberry in Oregon and Washington.  DP Barcode D339984.  EFED
memorandum to RD.  Undated.

USEPA.  2006.  Standardized Soil Mobility Classification Guidance.  U.S.
Environmental Protection Agency, Office of Prevention, Pesticides and
Toxic Substances, Office of Pesticide Programs, Environmental Fate and
Effects Division, Memorandum.  April 21, 2006.

USEPA.  2009.  Guidance for Selecting Input Parameters in Modeling the
Environmental Fate and Transport of Pesticides, Version 2.1.  U.S.
Environmental Protection Agency, Office of Chemical Safety and Pollution
Prevention, Office of Pesticide Programs, Environmental Fate and Effects
Division, October 22, 2009.  

USEPA.  2011.  Water Models.  U.S. Environmental Protection Agency,
Pesticides: Science and Policy.  Last updated: June 30, 2011.  Online
at:   HYPERLINK "http://www.epa.gov/oppefed1/models/water/" 
http://www.epa.gov/oppefed1/models/water/ 

Appendix I:

Model Outputs: PRZM/EXAMS, SCI-GROW, Cranberry

Representative PRZM/EXAM Output:  Michigan Bean – Aerial Application

SCI-GROW Output:

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:Idoxacarb

time is 10/10/2012  23:40:11

------------------------------------------------------------------------

  Application      Number of       Total Use    Koc      Soil Aerobic

  rate (lb/acre)  applications   (lb/acre/yr)  (ml/g)   metabolism
(days)

------------------------------------------------------------------------

      0.110           4.0           0.440      3.60E+02      267.0

------------------------------------------------------------------------

Groundwater screening cond (ppb) =   3.34E-01 or 0.33 ug/L

************************************************************************

Provisional Cranberry Output:

Appendix II:  Provisional Cranberry Model Equations

The Provisional Cranberry Model is a refinement of the Tier I Rice Model
v1.0 (Equations 1 and 2), which is a simple equilibrium partitioning
equation that calculates a single, screening-level concentration in rice
paddy water and released tailwater based on a compound’s application
rate and soil mobility.

Equations 1-2:  Tier I Rice Model v1.0 (USEPA, 2007b).

 	(1)

and, if appropriate:

 	(2)

where,

	Cw0 = initial water concentration [µg/L]

mai' = mass applied per unit area [kg/ha]

Kd = water-sediment partitioning coefficient [L/kg]

KOC = organic carbon partitioning coefficient [L/kg]

dw = water column depth = 0.10 m

dsed = sediment depth = 0.01 m

θsed = porosity of sediment = 0.509

ρb = bulk density of sediment = 1300 kg/m3

First, the Tier I Rice Model was provisionally modified (Equation 3) to
include as inputs degradation rate constants in order to estimate
single, screening-level concentrations in paddy water or tailwater at a
given time after application.

Equation 3:  Provisional Modified Rice Model (Jones, 2006).

 	(3)

where,

	Cw = water concentration [µg/L]

t = interval since last application [d]

k1 = upper 90th percentile rate constant in water column [1/d]

k2 = upper 90th percentile rate constant in pore water [1/d]

k3 = upper 90th percentile rate constant for adsorbed residues [1/d]

Then, the Provisional Modified Rice Model water column depth was
lengthened to a depth that is used to flood cranberry bogs (i.e., 12
inches; Cape Cod Cranberry Growers Association, 2001).

i.e.,

dw = water column depth = 0.305 m

In order to model degradation prior to the flood at harvest, the
application rates for n number of pre-harvest applications were
independently degraded over the interim until flooding and then summed
(Equation 4).

Equation 4:  Degradation in a Dry Bog.

 	(4)

where,

mai' = mass per unit area at flood [kg/ha]

mai'n = mass applied per unit area on the nth application [kg/ha]

k4 = upper 90th percentile rate constant on dry bog [1/d]

tn = interval from the nth application to harvest [d]

n = number of pre-harvest applications

The following four equations and parameter sets constitute the
Provisional Cranberry Model (Equations 1-4).

Equations 1-4:  Provisional Cranberry Model.

 	(1)

and, if appropriate:

 	(2)

where,

	Cw0 = initial water concentration [µg/L]

Kd = water-sediment partitioning coefficient [L/kg]

KOC = organic carbon partitioning coefficient [L/kg]

dw = water column depth = 0.305 m

dsed = sediment depth = 0.01 m

θsed = porosity of sediment = 0.509

ρb = bulk density of sediment = 1300 kg/m3

and, lastly:

 	(3)

where,

	Cw = water concentration [µg/L]

t = interval since flood [d]

k1 = upper 90th percentile rate constant in water column [1/d]

k2 = upper 90th percentile rate constant in pore water [1/d]

k3 = upper 90th percentile rate constant for adsorbed residues [1/d]



Appendix III:  Indoxacarb’s Degradation Profile

Code Name/ Synonym	Chemical Name	Chemical Structure	Study Type	MRID
Maximum Formation

(% Applied)

IN-KT413	CAS Name:  

sodium 7-chloro-2,5,-dihydro-2-[[(methoxycarbonyl)[4-

(trifluoromethoxy)phenyl]amino]carbonyl]indeno[1,2-

e][l,3,4]oxadiazine-4a(3H)-carboxylic acid

Molecular Weight: 513.82 g/mol (free acid)  

	

 	Hydrolysis     	44477301	48.0

	Hydrolysis     pH 7	45795801	47.1

	Hydrolysis     pH 9

88.1

	Aerobic Aquatic Metabolism	45793301	42.1

	Anaerobic Aquatic Metabolism	44477305	16.0

IN-MF014	CAS Name:  

methyl 2-[[[4-(trifluoromethoxy)phenyl]

amino ]carbonyl]hydrazine carboxylate

 	Hydrolysis     pH 5	45795801	6.1

	Hydrolysis     pH 7

14.7

	Aqueous Photolysis	44477302	37.8

	Aqueous Photolysis	45795802	37.6

IN-MH304	CAS Name:  

Not Reported

 	Aqueous Photolysis	44477302	19.9

	Aqueous Photolysis	45795802	32.3

MW 297	CAS Name:  

Not Reported

 

Proposed structure; not proven due to inability to synthesize standard
Aqueous Photolysis	44477302	14.1

IN-KB687	CAS Name:  

methyl[4(trifluoromethoxy)phenyl]carbamate

                                                  	Aqueous Photolysis
44477302	22.1

	Aqueous Photolysis	45795802	28.7

	Soil Photolysis	44477303	22.0

	Aerobic Soil Metabolism	44477304	11.0

IN-C0639	CAS Name:  

4-chloro-1,2-benzenedicarboxylic acid

 	Aqueous Photolysis	45795802	10.2

IN-MA573	CAS Name:  

2-carboxy-5-chloro benzeneacetic acid

 	Aqueous Photolysis	45795802	19.9

IN-JT333	CAS Name:  

methyl-7-chloro-2,5-dihydro
-2-[[[4(trifluoromethoxy)phenyl]amino]carbonyl]indeno[1,2e][1,3,4]oxadia
zine -4a(3H)-carboxylate

 	Aerobic Soil Metabolism	45906701	18.6

	Aerobic Aquatic Metabolism	44477306	10.5

	Aerobic Aquatic Metabolism	45793301	25.7

	Anaerobic Aquatic Metabolism	44477305	28.2

IN-KG433	CAS Name:  

Methyl-5-chloro-2,3-dihydro-2-hydroxy-1[[[(methoxycarbonyl)[4-(trifluoro
methoxy)phenyl]amino]carbonyl]hydrazono]-1H-indene-2-carboxylate



 

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IN-JU873	CAS Name:  

1-[[[[4-(trifluoromethoxy)phenyl] amino]
carbonyl]hydrazono]-1H-indene-2-carboxylate

 	Aerobic Soil Metabolism	45166303	12.9

IN-ML438	CAS Name:  

7-chloro-2,4-dihydro-4-[4-4
-(trifluoromethoxy)phenyl]-3H-indeno[2,1-e]-1,2,4-triazin-3-one

 	Aerobic Soil Metabolism	45166303	9.7

IN-MK643	CAS Name:  

l,2-dihydro-5-(trifluoromethoxy)-2H-benzimidazol-2-one

 	Aerobic Soil Metabolism	45166303

44477304	12.0

IN-MK638	CAS Name:  

[4-(trifluoromethoxy)phenyl)urea

 	Aerobic Soil Metabolism	45166303	28.1

IN-ML437-OH	CAS Name:  

 	Aerobic Soil Metabolism	44477304	13.0

IN-MP819	CAS Name:  

lndenol[1 ,2-e][1 ,3,4]oxadlazine-1 (2H)-carboxylic acid,
7-chloro-3,5-dlhydno-2-[[[4-(triftuoromethoxy)phenyl]amino]carbonyl]-,
methyl ester

 	Aerobic Aquatic Metabolism	45793301	10.3

IN-MS775	CAS Name:  

7-Chloro-4a,5-dihydro-N-(4-(trifluoromethoxy)phenyl]idenol[1 ,2-e][1
,3,4]oxadiazine-2(3H)-carboxamide

 	Aerobic Aquatic Metabolism	45793301	12.8

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Unidentified	Aerobic Aquatic Metabolism	44477306	24.1

CO2	Carbon Dioxide	O=C=O	Aerobic Soil Metabolism	45795803	35.7

	Aerobic Aquatic Metabolism	44477306	19.0

	Aerobic Aquatic Metabolism	45793301	25.8

Unextractable

Residues

	Aerobic Soil Metabolism	45906701	66.1

	Aerobic Aquatic Metabolism	44477306	38.0

	Anaerobic Aquatic Metabolism	44477305	46.8

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