UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

							     

								 PC Code: 121027							         	   		 DP Barcode: D357984

 Date: March 3, 2009

MEMORANDUM	

SUBJECT:	Drinking Water Assessment for the IR-4 New Use Petitions for
the Use of Methoxyfenozide on Dried Pea and Bean Subgroup 6C (Except
Soybean), Pomegranate, Popcorn, and (Regional Use) Citrus Crop Group 10.
 

TO:		John Redden, ARIA Team Leader

		Registration Division (7505P)

CC:		Sydney Jackson, IR-4 Team

		Barbara Madden, Team Leader

Mark Suarez, Risk Manager Reviewer

Richard Gebken, Product Manager   

		Registration Division (7505P) 

FROM:	Cheryl Sutton, Ph.D, Environmental Scientist  

		Environmental Risk Branch IV

		Environmental Fate and Effects Division (7507P)

REVIEWED

BY:		Marietta Echeverria, RAPL

		Environmental Risk Branch IV

		Environmental Fate and Effects Division (7507P)

APPROVED

BY:		Elizabeth Behl, Branch Chief

		Environmental Risk Branch IV

		Environmental Fate and Effects Division (7507P)

Executive Summary

	  SEQ CHAPTER \h \r 1 EFED has reviewed the IR-4 request for
methoxyfenozide (Intrepid™) registration as an insecticide on dried
pea and bean subgroup 6C (except soybean), pomegranate, popcorn, and
(regional use) citrus crop group 10.  The maximum proposed single
application rates for these crops range from 0.12 to 0.25 lbs a.i./acre,
but the maximum annual application rate for each of the crops is
restricted to a total 1.0 lb a.i./acre/season.  The maximum application
rate for each of the assessed uses is less than that assessed for a
previous Section 3 request (DP Barcode D249466; re-evaluated in DP
Barcodes 331949, 340542) for pome fruits, i.e., 0.3 lbs. a.i./acre
applied up to six times at 10- to 18-day intervals for a maximum of 1.8
lbs. a.i./acre/season.   

Table 1 lists the EDWCs recommended for use in HED’s dietary risk
assessment; these were reported previously in the two most recent EFED
Drinking Water Assessments (11/08, DP Barcode D354232; 10/07, DP
Barcodes D331949, D340542).  These values are based on the pome fruit
use previously assessed.  It is noted that the current labeled rate for
pome fruits is actually only 0.25 lbs. a.i./acre/application rather than
what was previously assessed (0.30 lbs a.i./acre/application). 
Therefore, the EDWCs reported here are conservative.

EFED continues to have concerns that the combination of high persistence
and moderate mobility of methoxyfenozide makes it plausible that this
compound may pose a greater long-term risk than what is suggested by the
screening-level drinking water assessments.   In particular, once
introduced into the environment, this compound could travel to key
aquatic environmental compartments and persist for extended periods of
time.   One outstanding data requirement from the conditional
registration of this compound is for the monitoring of surface water and
sediment in a representative sample of high use areas in proximity to
surface water.

For further details on the environmental fate and transport of
methoxyfenozide, please refer to DP Barcode D249466.

Table 1. Tier II estimated drinking water concentrations (EDWCs)
resulting from applications of methoxyfenozide.

Drinking water source (model)	Use 

(modeled rate)	1-in-10 year acute (ppb)	1-in-10 year chronic (ppb)	30-
year average (ppb)

Surface water (PRZM/EXAMS)	Pome fruit

(0.3 lb a.i./A x 6 applic.; total of 1.8 lb/A/yr)	52.2	33.1	22.3

Groundwater (SCIGROW)	Pome fruit

(1.8 lb/A/yr)	7.43	<7.43	<7.43



use Characterization

	Methoxyfenozide is currently registered for use on corn, cotton,
cucurbits vegetables, grapes, pome and stone fruits, root vegetables,
spearmint and peppermint, berries (including strawberries and
cranberries), tree nuts, leafy vegetables, globe artichokes, legume
vegetables, a variety of tropical fruits, black-eyed and southern peas,
bushberries, dry beans, grass forage, peanuts, tuberous and corm
vegetables, non-grass forage, avocado, green onion and ornamentals. 
Methoxyfenozide is the sole active ingredient in Intrepid 2F, and it is
applied aerially or through ground equipment.  

The maximum single application rates for the proposed IR-4 new uses are
listed in Table 2.  The proposed rates for these uses are lower than
that assessed for a previous Section 3 request (DP Barcode D249466) for
pome fruits, i.e., 1.8 lbs. a.i./acre/season (USEPA, 2001). 

 

Table 2.  Summary use information for methoxyfenozide proposed new uses,
based on Intrepid®2F supplemental labels (EPA Reg. No. 6279-442; IR-4
PR Nos. 09367, 07527, 10094, 10160).



Use	Max. Single Application Rate             (lbs. a.i./A)	Max. No. of
Applications 	Max. Seasonal Application Rate (lbs. a.i./A)	Min.
Application Interval (days)	Application Method	Comments

Dried pea and bean (except soybean) subgroup 6C	0.25 lb ai/A	4 (per
season)	1.0 lb ai/A/season1	7	Ground or aerial spray (foliar)	 none

Pomegranate	0.25 lb ai/A	Not stated on label.	1.0 lb ai/A/season	10
Ground or aerial spray (foliar)	Label Restriction:  Not for use in NY
state.

Popcorn	0.12 lb ai/A	Not stated on label.	1.0 lb ai/A/season	5	Ground or
aerial spray (foliar)	Label Restriction:  Not for use in NY state.

Citrus crop group 10	0.25 lb ai/A	Not stated on label.	1.0 lb
ai/A/season	14	Ground spray (foliar)	Label Restriction: Only for use &
distribution in states west of the Mississippi River.

1For the purposes of this assessment, the maximum annual use rate was
assumed to be equal to the reported “per season” rate (i.e., it was
assumed only one crop per year would be grown).  Use on more than one
crop per year (either the same crop or other crops with registered
methoxyfenozide uses) on the same site may require further assessment to
determine new estimated drinking water concentrations.

Environmental fate and transport characterization

Methoxyfenozide is very persistent (t1/2 = 1 to 3 years in soil and
water) and moderately mobile (Koc = 219 – 922 L/kgoc in various
soils).  It is stable to photolysis and hydrolysis, is not significantly
volatile, and degrades only very slowly by microbial activity. 
Degradates are predominantly RH-117236 (3,5-Dimethylbenzoic acid
N-tert-butyl-N'-(3-hydroxy-2-1nethylbenzoyl)hydrazide) and RH-131154
(3-[N-tert-butyl-N'-(3-methoxy-2-methylbenzoyl)-hydrazinocarbonyl]-5-met
hylbenzoaicci d), but these are only present at low concentrations.
Because of its resistance to degradation and its mobility,
methoxyfenozide has the potential to accumulate and to move off the site
of application by leaching and erosion/runoff. Table 3 summarizes the
physico-chemical properties of methoxyfenozide.  For further details on
the environmental fate and transport of methoxyfenozide, please refer to
DP Barcode D249466.

Table 3.  General Chemical Properties and Environmental Fate Parameters
of Methoxyfenozide.

Chemical/Fate Parameter	Value	Source

Chemical name
n-tert-butyl-N’-[2-methyl-3-methoxybenzoyl]-3,5-dimethylbenzohydrazide
D249466

Molecular mass	368 g/mol	D249466

Vapor pressure (25(C)	2.0 x 10-8 torr	D249466

Solubility  (25(C)	3.3 mg/L	D249466

Octanol-water partition coefficient (Kow)	103.72	D249466

Organic carbon partitioning coefficient (Koc) 	267, 922, 678, 219, 365
L/kgoc	MRID 44144433

Hydrolysis half-life (pH 5, 7, 9)

	Stable	MRID 44144430

Aqueous photolysis half-life

	Stable	MRID 44617805

Soil photolysis half-life	Stable	MRID 44617806

Aerobic soil metabolism half-life	573, 1100, 772, 336 d	MRIDs 44617808,
44617807, 4414432

Aerobic aqueous metabolism half-life	387, 962 d	MRID 44617809

Anaerobic aqueous metabolism half-life	654 d	MRID 44617810

Terrestrial field dissipation half-life 

	237, 139, 151, 92 d	MRID 44617812, 44617811



drinking water modeling

Estimated drinking water concentrations (EDWCs) were generated using
EFED’s standard suite of models.  The proposed uses and the currently
registered maximum use pattern (pome fruit) were assessed. 

Models

	Pesticide Root Zone Model (PRZM 3.12.2 dated May 12, 2005) and Exposure
Analysis Modeling System (EXAMS 2.98.04.06 dated April 25, 2005) are
simulation models coupled with the input shell PE 5.0 (November 15,
2006) to generate EDWCs of methoxyfenozide 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, 2006).  Percent Cropped 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
methoxyfenozide residue 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, 2006a).  

Input Parameters

	Input parameters for the PRZM/EXAMS and SCI-GROW models are listed in
Table 4, Table 5 and Table 6.  Explanations of various model input
parameters are discussed below.

Table 4.  PRZM/EXAMS application-specific input parameters for
methoxyfenozide.  

Uses	PRZM Scenario	Max App rate (lbs ai/A)	# Apps	Interval	% Drift/
Efficiency	IPSCND	Date of 1st of application

Pome fruit	PA apple	0.3	6	10	0.16/ 0.95	3	May 4th



Table 5.  PRZM/EXAMS chemical-specific input parameters for
methoxyfenozide.  

Input Parameter	Value	Comment	Source

Molecular Mass (g/mol)	368	Product chemistry data	D249466

Vapor Pressure at 25°C (torr)	2.0 x 10-8	Product chemistry data	D249466

Solubility in Water at 25oC (mg/L)	33	10X the solubility	D249466

Organic Carbon Partition Coefficient (KOC) (L/kgOC)	490	Represents the
average KOC.	MRID 44144433

Aerobic Soil Metabolism Half-life (days)	960	Represents the 90th %-ile
confidence bound on the mean half-life.	MRIDs 44617808, 44617807,
4414432

Aerobic Aquatic Metabolism Half-life (days)	1559	Represents the 90th
%-ile confidence bound on the mean half-life.	MRID 44617809

Anaerobic Aquatic Metabolism Half-life (days)	1962	3x one data point
MRID 44617810 

Hydrolysis Half-lives (days)	0	Stable	MRID 44144430

Aqueous Photolysis

Half-life (days)	0	Stable	MRID 44617805

Foliar Degradation Half-life (days)	0	Stable, no data	Default

Foliar Washoff Extraction Coefficient (cm-1)	0.5

Default



Table 6.  SCI-GROW input parameters for methoxyfenozide.  

Input Parameter	Value	Comment	Source

Application Rate (lbs a.i./A)	See Table 4	Label directions	Proposed and
current labels

Applications per Year	See Table 4	Label directions	Proposed and current
labels

Organic Carbon Partition Coefficient (kOC) (L/kgOC)	219	Lowest KOC
value;  > 3x variability in data	MRID 44144433

Aerobic Soil Metabolism

Half-life (days)	695	Average of 4 values	MRIDs 44617808, 44617807,
4414432



A currently approved PRZM scenario was used in modeling (PA Apple).  The
application method and rate were obtained from a previous assessment (DP
Barcodes 331949, 340542).  Application timing of methoxyfenozide is
related to various pest pressures.  For the purposes of this assessment,
it was assumed that applications were made two weeks after crop
emergence (as specified in the standard scenario).  Applications were
modeled with aerial application input values as specified on the label.

Chemical property input values were chosen in accordance with current
input parameter guidance (USEPA, 2002b).  The upper 90% confidence bound
on the mean was selected for the aerobic soil metabolism half-life (960
d) for surface water and the median value (695 d) was used for
groundwater modeling with SCI-GROW as per current input parameter
guidance for these models.  The hydrolysis and photolysis were modeled
as stable and the upper 90% confidence bound on the mean was selected
for the aerobic aquatic metabolism half-life (1559 d) and 3x the
anaerobic aquatic metabolism value was used since there is only one data
point.  The average and lowest koc value (490 and 219 L/kgoc) was used
for PRZM/EXAMS and SCI-GROW.

	The default agricultural PCA of 0.87 was used for pome fruits 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.  

Modeling Results

The maximum use pattern that has yielded the maximum surface water and
groundwater EDWCs listed below in Table 7 for use in drinking water
exposure estimation is pome fruit (which has the highest application
rate).  Model input/output data for these estimates can be found in the
EFED Drinking Water Assessment (10/07; DP Barcodes D331949, D340542). 
Because the actual rate for pome fruits is only 0.25 lbs.
a.i./acre/application rather than the assessed rate of 0.30 lbs
a.i./acre/application, the EDWCs reported here are conservative.

Table 7.  Tier II estimated drinking water concentrations (EDWCs)
resulting from application of methoxyfenozide.

Drinking water source (model)	Uses 

(modeled rate)	PCA	PRZM Scenario	1-in-10 year acute (ppb)	1-in-10 year
chronic (ppb)	30- year average (ppb)

Surface water (PRZM/EXAMS)	Pome fruit

(1.8 lb/A/yr)	0.87	PA apple	52.2	33.1	22.3

Groundwater (SCIGROW)	Pome fruit

(1.8 lb/A/yr)	--	--	7.43	<7.43	<7.43



Monitoring Data

There are no available monitoring data for methoxyfenozide.  Due to
uncertainties identified during the Section 3 Registration process,
methoxyfenozide is conditionally registered.  One of the outstanding
conditional registration requirements is:

Three years after use, obtaining approval for and conducting monitoring
of surface water and sediment in a representative sample of high use
areas in proximity to surface water.

 

Conclusions

The EDWCs reported here are conservative since they reflect a higher
application rate than is currently labeled for pome fruit.  While the
maximum proposed single application rates for the new uses assessed here
range from 0.12 to 0.25 lbs a.i./acre (with a maximum seasonal
application restricted to a total 1.0 lb a.i./acre/season), the EDWCs
reported here are based on the pome fruit use previously assessed (0.30
lbs a.i./acre/application with a maximum annual application of 1.8 lbs
a.i./acre).  It is noted that the current labeled rate for pome fruits
is actually only 0.25 lbs. a.i./acre/application, rather than what was
previously assessed.  

There remains an outstanding data requirement (a condition of
registration) for monitoring of surface water and sediment in a
representative sample of high use areas in proximity to surface water. 
Additionally, EFED continues to have concerns that the persistence of
methoxyfenozide, makes it plausible that this compound may pose a
greater long-term drinking water exposure concern than what is suggested
by the screening-level assessment.  In particular, once introduced into
the environment, this compound could travel to key aquatic environmental
compartments, such as aquatic sediment, and persist for extended periods
of time.  Thus, there are significant uncertainties regarding the
potential long-term drinking water exposure associated with the use of
methoxyfenozide.  

There is also a continuing concern regarding label language.  The
proposed label currently specifies a maximum application rate on a
seasonal basis rather than an annual basis.  Given the persistence of
methoxyfenozide, repeat applications for crops for which there is more
than one season per year could result in accumulation and increased
aquatic exposure than reported in this assessment.  

 

 

Attachment 1. Modeling Input and Output: 

stored as PAapple.out

Chemical: methoxyfenozide

PRZM environment: PAappleSTD.txt	modified Tueday, 29 May 2007 at
13:01:58

EXAMS environment: ir298.exv	modified Thuday, 29 August 2002 at 15:34:12

Metfile: w14751.dvf	modified Wedday, 3 July 2002 at 09:06:14

Water segment concentrations (ppb)

Year	Peak	96 hr	21 Day	60 Day	90 Day	Yearly

1961	33.26	32.66	31.55	29.61	27.82	12.1

1962	24.85	24.54	23.31	21.44	21.57	16.95

1963	19.51	19.29	18.48	18.03	17.66	14.92

1964	26.14	25.78	24.38	22.31	21.76	16.12

1965	18.81	18.58	17.97	17.57	17.42	13.86

1966	58.61	57.63	54.2	48.39	44.87	20.56

1967	48.63	48.1	45.98	43.81	42	31.06

1968	41.01	40.46	39.67	37.88	35.61	27.85

1969	83.03	81.65	76.39	67.93	62.54	35.14

1970	46.54	45.95	44.09	41.39	39.5	31.56

1971	45.86	45.19	42.58	39.25	36.68	25.41

1972	143	141	132	115	105	53.15

1973	52.63	52.3	50.95	48.46	46.15	41.75

1974	39.96	39.55	37.68	35.73	34.34	28.42

1975	52.74	51.97	49.48	44.78	41.47	27.96

1976	31	30.62	29.67	27.51	27.22	22.31

1977	23.46	23.17	22.01	20.15	19.21	15.63

1978	40.46	39.83	37.42	33.78	31.28	19

1979	28.27	27.9	26.43	24.35	23.4	18

1980	23.21	22.93	22.21	21.28	20.26	15.78

1981	24.12	23.81	23.38	22.52	21.66	16.44

1982	55.01	54.17	52.41	47.81	45.05	25.6

1983	26.95	26.64	25.91	24.97	23.81	19.65

1984	44.26	43.61	42.17	38.68	36.2	22.22

1985	26.02	25.72	25.02	23.93	23.13	18.69

1986	33.85	33.38	31.85	28.85	27.36	18.69

1987	32.95	32.49	31.01	27.88	26.51	19.56

1988	30.85	30.43	28.8	25.88	24.17	18.24

1989	41.21	40.74	38.88	36.29	34.96	22.92

1990	38.87	38.36	36.34	35.11	34.4	24.24

Sorted results

Prob.	Peak	96 hr	21 Day	60 Day	90 Day	Yearly

0.032258064516129	143	141	132	115	105	53.15

0.0645161290322581	83.03	81.65	76.39	67.93	62.54	41.75

0.0967741935483871	58.61	57.63	54.2	48.46	46.15	35.14

0.129032258064516	55.01	54.17	52.41	48.39	45.05	31.56

0.161290322580645	52.74	52.3	50.95	47.81	44.87	31.06

0.193548387096774	52.63	51.97	49.48	44.78	42	28.42

0.225806451612903	48.63	48.1	45.98	43.81	41.47	27.96

0.258064516129032	46.54	45.95	44.09	41.39	39.5	27.85

0.290322580645161	45.86	45.19	42.58	39.25	36.68	25.6

0.32258064516129	44.26	43.61	42.17	38.68	36.2	25.41

0.354838709677419	41.21	40.74	39.67	37.88	35.61	24.24

0.387096774193548	41.01	40.46	38.88	36.29	34.96	22.92

0.419354838709677	40.46	39.83	37.68	35.73	34.4	22.31

0.451612903225806	39.96	39.55	37.42	35.11	34.34	22.22

0.483870967741936	38.87	38.36	36.34	33.78	31.28	20.56

0.516129032258065	33.85	33.38	31.85	29.61	27.82	19.65

0.548387096774194	33.26	32.66	31.55	28.85	27.36	19.56

0.580645161290323	32.95	32.49	31.01	27.88	27.22	19

0.612903225806452	31	30.62	29.67	27.51	26.51	18.69

0.645161290322581	30.85	30.43	28.8	25.88	24.17	18.69

0.67741935483871	28.27	27.9	26.43	24.97	23.81	18.24

0.709677419354839	26.95	26.64	25.91	24.35	23.4	18

0.741935483870968	26.14	25.78	25.02	23.93	23.13	16.95

0.774193548387097	26.02	25.72	24.38	22.52	21.76	16.44

0.806451612903226	24.85	24.54	23.38	22.31	21.66	16.12

0.838709677419355	24.12	23.81	23.31	21.44	21.57	15.78

0.870967741935484	23.46	23.17	22.21	21.28	20.26	15.63

0.903225806451613	23.21	22.93	22.01	20.15	19.21	14.92

0.935483870967742	19.51	19.29	18.48	18.03	17.66	13.86

0.967741935483871	18.81	18.58	17.97	17.57	17.42	12.1

0.1	58.25	57.284	54.021	48.453	46.04	34.782

					Average of yearly averages:	23.126

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: PAapple

Metfile:	w14751.dvf

PRZM scenario:	PAappleSTD.txt

EXAMS environment file:	ir298.exv

Chemical Name:	methoxyfenozide

Description	Variable Name	Value	Units	Comments

Molecular weight	mwt	368	g/mol

Henry's Law Const.	henry		atm-m^3/mol

Vapor Pressure	vapr	2e-8	torr

Solubility	sol	33	mg/L

Kd	Kd		mg/L

Koc	Koc	490	mg/L

Photolysis half-life	kdp	0	days	Half-life

Aerobic Aquatic Metabolism	kbacw	674	days	Halfife

Anaerobic Aquatic Metabolism	kbacs	654	days	Halfife

Aerobic Soil Metabolism	asm	960	days	Halfife

Hydrolysis:	pH 7	0	days	Half-life

Method:	CAM	2	integer	See PRZM manual

Incorporation Depth:	DEPI		cm

Application Rate:	TAPP	0.33	kg/ha

Application Efficiency:	APPEFF	0.95	fraction

Spray Drift	DRFT	0.16	fraction of application rate applied to pond

Application Date	Date	4-5	dd/mm or dd/mmm or dd-mm or dd-mmm

Interval 1	interval	10	days	Set to 0 or delete line for single app.

app. rate 1	apprate		kg/ha

Interval 2	interval	10	days	Set to 0 or delete line for single app.

app. rate 2	apprate		kg/ha

Interval 3	interval	10	days	Set to 0 or delete line for single app.

app. rate 3	apprate		kg/ha

Interval 4	interval	10	days	Set to 0 or delete line for single app.

app. rate 4	apprate		kg/ha

Interval 5	interval	10	days	Set to 0 or delete line for single app.

app. rate 5	apprate		kg/ha

Record 17:	FILTRA	

	IPSCND	3

	UPTKF	

Record 18:	PLVKRT	

	PLDKRT	

	FEXTRC	0.5

Flag for Index Res. Run	IR	Reservoir

Flag for runoff calc.	RUNOFF	total	none, monthly or total(average of
entire run)

 PAGE   

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OFFICE OF

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