Document ID: EPA-HQ-OPP-2007-0309-0006
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-12-26T05:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

                                                                     
OFFICE OF 

                                                                 
PREVENTION, PESTICIDES AND

                                                                   
TOXIC SUBSTANCES

  SEQ CHAPTER \h \r 1 								PC Code 	107091

				DP Barcode	D335338

MEMORANDUM

DATE:	April 24, 2007

SUBJECT:	Tier I Estimated Drinking Water Concentrations of Etoxazole and
Its Transformation Products for the Use in the Human Health Risk
Assessment:  IR-4 Petition for the Use of the Chemical on Cherries,
Melons (Subgroup 9A), and Hops

TO:		Sidney Jackson, Risk Manager Reviewer

		Barbara Madden, Team Leader

		Daniel Rosenblatt, Chief 

		Risk Integration Minor Use and Emergency Response Branch

		Registration Division (7505P)

AND:		Jennifer Tyler

		PV Shah, 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 Drinking Water Concentrations
(EDWCs) for etoxazole, and for its major transformation products R-8 and
R-13, calculated using the Tier I aquatic models FIRST (surface water)
and SCIGROW (ground water) for use in the human health risk assessment. 
The registrant seeks registration for the outdoor uses of the chemical
on cherries, melons subgroup 9A and hops. 

Exposure to surface water is possible through surface water runoff, soil
erosion, and off-target spray drift.  Due to relatively high adsorption
of etoxazole (slightly mobile to hardly mobile, KOC’s on the order of
~5000 to ~55,300 mL/g, FAO classification), the exposure to ground
waters is expected to be moderately low.  The Tier I Estimated Drinking
Water Concentrations (EDWCs) for etoxazole and for its major
transformation products R-8 and R-13 (as requested by HED), calculated
using FIRST (surface water) and SCIGROW (ground water) for use in the
human health risk assessment were as follows:   For etoxazole surface
water, the acute value is 3.49 ppb and the chronic value is 0.332 ppb. 
The groundwater screening concentration for both acute and chronic is
0.00173 ppb.  For R-8 surface water, the acute value is 2.80 ppb and the
chronic value is 0.913 ppb.  The groundwater screening concentration for
both acute and chronic is 0.366 ppb.  For R-13 surface water, the acute
value is 0.802 ppb and the chronic value is 0.0285 ppb.  The groundwater
screening concentration for both acute and chronic is 0.000322 ppb.

A more definitive assessment could be performed, using Tier II aquatic
models PRZM/EXAMS. Should any questions arise, please, contact José
Meléndez at 787-977-5856 or 787-799-3021.

Identification of specific data gaps:

No major data gaps were identified.

EXECUTIVE SUMMARY 

   

Etoxazole: CAS name:
2-(2,6-difluorophenyl)-4-[4-(1,1-dimethylethyl)-2-ethoxyphenyl]-4,5-dihy
drooxazole; IUPAC name:
(RS)-5-tert-butyl-2-[2-(2,6-difluorophenyl)-4,5-dihydro-1,3-oxazol-4-yl]
phenetole; CAS number 153233-91-1; PC Code 107091; and Molecular Formula
C21H23F2NO2; is an acaricide/miticide.  Its chemical class is diphenyl
oxazoline.  The registrant, Valent, has claimed in a prior submission
(02/15/02) that they have not yet determined a mode of action, but
states that “it appears to control susceptible mites by inhibiting the
molting process through disruption of the cell membrane.”  It
reportedly works by contact of the mite juvenile stages (eggs to
nymphs), but does not kill adult mites.  

this IR-4 package:  ZEAL™ MITICIDE, ZEAL™ WP Miticide, and SECURE
Miticide.  The proposed uses are cherries (sweet and tart), melon
subgroup 9A (cantaloupe, citron melon, muskmelon, watermelon), and hops.
 The application methods vary depending on the crop.  For cotton,
applications may be by ground or aerial methods.  For pome fruits,
non-bearing fruits, and tree nuts, the applications may be by ground
methods via airblast.  For other crops, the applications are by ground
spray methods.

 

The models used for this screening level assessment (Tier I) are FIRST
and SCIGROW, with the crop with the maximum application rate (hops) and
the maximum PCA (0.87, or national default).  Two degradates were
modeled along with etoxazole, R-8
(2-amino-2-(4-tert-butyl-2-ethoxyphenyl)ethanol), and R-13
(4-(4-tert-Butyl-2-ethoxyphenyl)-2-(2,6-difluorophenyl)-oxazole) (as
requested by HED).  The total residues approach was not utilized because
it was found that the mobility characteristics of the transformation
products were different than those of the parent, furthermore, the
structures of the transformation products were not necessarily similar
to the parent (refer to a summary of the results in Table 1, and
structures in Appendix)

For this DWA, it has been assumed that at a given time, the maximum
amount of etoxazole has been applied to the field, and, at the same
time, certain amounts of R-8 and R-13 are applied by granular method. 
The EFED acknowledges that this approach does not have mass balance,
that is, the amount of pesticide plus degradates applied exceeds the
maximum application rate.  However, the Division believes that the
results obtained are suitable for a screening level assessment and are
conservative.

 

There is considerable uncertainty concerning the various degradates of
etoxazole (some of which are relatively persistent).  The absence of
full environmental fate information about such degradates constitutes an
uncertainty at this time; however, a conservative approach was taken in
this assessment in the absence of data.  There is also uncertainty in
the role of various competing dissipation and/or degradation mechanisms
of etoxazole.  Various studies have been deemed supplemental.  Despite
these facts, the EFED believes that this assessment is conservative. 

Table 1 provides a summary of Tier I modeled drinking water
concentrations of etoxazole, R-8 and R-13.  Additional refinements of
the assessment can be developed with higher tier analysis, if requested
by HED. 

Table 1.  Maximum Tier I Estimated Drinking Water Concentrations (EDWCs)
for drinking water risk assessment based on ground application of
etoxazole, based on one application on hops at 0.18 lb a.i./A.

Chemical	

Acute EDWC   Surface Water FIRST (ppb)	

Chronic EDWC Surface Water  FIRST (ppb)	

Acute and Chronic EDWC Ground Water  SCIGROW (ppb)

Etoxazole	3.49	0.332	0.00173

R-8	2.80	0.913	0.316

R-13	0.802	0.0285	0.000322

PROBLEM FORMULATION

This is a Tier I drinking water assessment that uses modeling and
monitoring data, if available, to estimate the ground water and surface
water concentrations of pesticides and transformation products 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 provides estimated exposure
concentrations for the human health dietary risk assessment.  

ANALYSIS

Use Characterization

A summary table of all use patterns, highlighting Tier I modeled use, is
illustrated below (Table 2).

Zeal™ WP Miticide, Secure™ Miticide, and Zeal™ Miticide label(s). 
New uses are highlighted, while modeled use is bolded.

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

Cotton	0.045	1	0.045	N/A	Ground, aerial	28

Grape	0.135	1	0.135	N/A	Ground	14

Pome Fruit (apple, crabapple, loquat, pear, quince)	0.135	1	0.135	N/A
Ground with airblast equipment	14-28

Strawberry	0.135	1	0.135	N/A	Ground	1

Non-Bearing Fruit Trees	0.135	1	0.135	N/A	Ground with airblast equipment
365

Christmas Trees	0.135	1	0.135	N/A	Ground	N/A

Tree Nuts (almond, beech nut, Brazil nut, butternut, cashew, chinquapin,
filbert (hazelnut), hickory nut, macadamia nut, pecan, pistachio, walnut
(black, English)	0.135	1	0.135	N/A	Ground with airblast equipment	28

Cherry (sweet and tart)	0.135	1	0.135	N/A	Ground	7

Melon Subgroup 9A (cantaloupe, citron melon, muskmelon, watermelon)
0.135	1	0.135	N/A	Ground	7

Hop	0.18	1	0.18	N/A	Ground	7

There are various application methods for this miticide.  It can be
applied aerially or by ground methods to cotton.  It may be applied by
ground methods via ground spray or airblast to all other crops (no
aerial applications for other crops).

The use pattern selected for modeling was hops.  It involved the highest
application rate among all the crops.  Even though cotton may be applied
aerially, it involves a much smaller application rate, and certain crops
may be applied by airblast, but their application rate is also smaller
than that for hops.  Hops utilizes the highest PCA, with the default of
87%.  The interval between applications does not apply in any case,
because for all crops only one application is allowed per season.

Fate and Transport Characterization

A detailed summary table of physical/chemical and environmental
fate/transport properties of the pesticide, including measured
parameters, values, data sources, and comments, are included in this
section.   (Table 3)

  SEQ CHAPTER \h \r 1 Table 3.  Summary of physical/chemical and
environmental fate and transport properties of etoxazole and
transformation products.

PARAMETER	VALUE(S) (units)	SOURCE	COMMENT

  Chemical Name
2-(2,6-difluorophenyl)-4-[4-(1,1-dimethylethyl)-2-ethoxyphenyl]-4,5-dihy
drooxazole	_	CAS name

  Molecular Weight	359.42 g/mole	_	–

  Solubility (20°C)	0.075 mg/L or ppm	MRID: 45089902 and 45089903.	–

  Vapor Pressure (20°C)	7 x 10-6 mmHg	MRID: 45089902.	–

  Henry’s Law constant	8.5 x 10-6 atm-m3/mol	_	Estimated from vapor
pressure and water solubility.

  pKa (20°C)	_	_	–

 Octanol-Water Partition Coefficient  (KOW)	3.31x105	MRID: 45089902.	–

  Hydrolysis Half-life 

  [pH 5, 7, 9; (20°C)]	pH 5 9.6 days;  pH 7 ~stable (99 days); pH 9
~stable (98 days)	MRID: 45090017.	_

  Aqueous Photolysis Half-life 

  (pH 5)	28.8 days of 12 hours of sunlight/ 12 hours dark	MRID:
46658101.	_

  Soil Photolysis Half-life	CL from UK, t1/2  = 19.3 days	MRID:
45090020, 46299904.	–

  Aerobic Soil Metabolism Half-life	Study performed using
[U-14C-tert-butylphenyl] and [U-14C-difluorophenyl] radiolabels

SL from UK 10.2-12.0 days.

SL from CA 19.4-23.2 days.

Studies performed using [U-14C-tert-Butylphenyl] radiolabel

S from Germany 12.7 days.

LS from Germany 21.5 d.  CL from UK 44.7 days.   SL from UK 26.2 days
(@10(C).                SL from UK, same soil as above 2.3 days (@30(C).
	MRID: 45090019, 45090021, 45090022.	_

  Anaerobic Soil Metabolism   

  Half-life	SL from UK 101.9-111.8 days.

	MRID: 45090023.	–

  Anaerobic Aquatic Metabolism   

  Half-life	Water clay sed. from Greenville, MS 138-155 days.  Etoxazole
was associated with the sediment.	MRID: 45621718.	–

  Aerobic Aquatic Metabolism 

  Half-life	N/A	N/A	N/A

  Organic Carbon Partition

  Coefficient (KOC)	5420, 5230, 11000, 4910, 18000, 23100, 55300, 14200
mL/gOC

	MRID: 45090024, 45090026, 46299905, 46299906.	Parent Etoxazole

  Soil Partition Coefficient (Kd)	131, 68, 66, 103, 156, 335, 193, 156 
mL/g	MRID: 45090024, 45090026, 46299905, 46299906.	Parent Etoxazole

  Organic Carbon Partition

  Coefficient (KOC)	1125, 7540, 2330 mL/gOC

	MRID: 45250906.	Transformation Product R-7

  Soil Partition Coefficient (Kd)	27, 98, 14  mL/g	MRID: 45250906.
Transformation Product R-7

  Organic Carbon Partition

  Coefficient (KOC)	103, 351, 207 mL/gOC

	MRID: 45250907.	Transformation Product R-8

  Soil Partition Coefficient (Kd)	2.48, 4.56, 1.24 mL/g	MRID: 45250907.
Transformation Product R-8

  Organic Carbon Partition

  Coefficient (KOC)	36540, 83230, 13670 mL/gOC

	MRID: 45250908.	Transformation Product R-13

  Soil Partition Coefficient (Kd)	877, 1082, 82 mL/g	MRID: 45250908.
Transformation Product R-13

  Terrestrial Field Dissipation 

  Half-life	St. Martin des Bois (Northern France) SiCL; DT50=8 days

Montech (Southern France) CL; DT50=8 days

Senas (Southern France) CL; DT50=4 days

Schleithal (Northern France) SiL; DT50=9 days

The degradate R-8 was no detected at any test interval.

Bare ground in Santa Cruz Co., CA, SL; t½=7.0 days, major product
detected R-7 (generally 0-7.5 cm soil layer)

Bare ground in Payette Co., ID, SL; t½=11.7 days, major product
detected R-7 (only in the 0-7.5 cm soil layer)

Bare ground in Washington Co., MS, SiL; t½=<1 day, major product
detected R-7 (only in 0-7.5 cm soil layer)	MRID: 45250909, 45621721,
45621722, 45621723.	_

Accumulation in Fish    (Maximum BCF)	1600X for edible tissues

4700X for nonedible tissues

3300X for whole fish

After 5 days depuration, 70-78% of the [14C]residues were depurated (t½
depuration estimated at 2.6 days for edible tissues, and 4.6-6.2 days
for nonedible tissues.	MRID: 45621615, 46269907.	_

Based on a number of valid and supplemental studies, it appears that the
major routes of dissipation of etoxazole are aqueous and soil
photolysis, and aerobic soil metabolism.  The relatively high soil
organic carbon adsorption coefficient (generally,  KOC > 5000), of
etoxazole, indicates that it may not be a direct threat to ground
waters; however, modeling results indicated that it may reach levels in
adjacent bodies of water that may pose a threat to certain aquatic
organisms.

Important transformation products of etoxazole appear to be R-4, R-7,
and R-8.  Of these, R-8 is more mobile and relatively persistent.  R-7
shows moderate mobility.  Compared to the aerobic conditions, the
anaerobic metabolism is a relatively minor route of dissipation of
etoxazole (half-lives were >100 days).  The major transformation
products were R-11 in an anaerobic soil metabolism study and R-11 and
R-4 in an anaerobic aquatic metabolism study.

Three field dissipation studies, conducted in bare soils in CA (Elder
sandy loam soil, representative of a typical strawberries site), Idaho
(Cashmere sandy loam soil, representative of a typical apples site), and
MS (Dundee silt loam soil, representative of a typical cotton site),
confirmed that etoxazole is relatively short lived (half-lives ranged
from <1 day to 11.7 days).  The only transformation product observed in
the field in substantial amounts was R-7 (generally detected only in the
0-7.5 cm soil depth).

Etoxazole shows a significant potential to bioaccumulate, as expected
from its very high octanol/water partition coefficient (331,000). 
Residues bioaccumulated in Rainbow trout with maximum bioconcentration
factors of 1600X for the edible tissue, and 3300x for whole fish. 
However, depuration was relatively rapid (half-life 2.6 days for edible
tissue).

There is uncertainty in the role of the various competing dissipation
and/or degradation mechanisms of etoxazole.  In addition, various
studies have been deemed supplemental.  There is considerable
uncertainty concerning the various degradates of etoxazole (some of
which appear to be relatively persistent).  The absence of full
environmental fate information about such degradates constitutes an
uncertainty at this time; however, a conservative approach was taken in
this assessment in the absence of such data. 

The summary of the various degradation products formed by each process
in the studies reviewed is provided in the following table (Table 4).

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

STUDY TYPE	DEGRADATE and MAXIMUM CONCENTRATION	SOURCE

	R-4 (% applied)	R-7 (% applied)	R-13 (% applied)

	  Hydrolysis	60.6% @ 21 days, pH 5	13.0% @ 30 days, pH 7	_	MRID:
45090017.

  Aqueous Photolysis	_	_	R-11, 30.2% at 14 days, study termination.
MRID: 46658101.

  Soil Photolysis	_	_	R-3, 11.7% @ 295 hr; R-11, 12.0% @ 295 hr or study
termination	MRID: 45090020, 46299904.

  Aerobic Soil Metabolism	11.9% @ 30 days	21.6% @ 7 days	30.0% @ 62
days; R-8, 14.6% @ 120 days; R-3 10.4% @ 61 days, various studies	MRID:
45090019, 45090021, 45090022.

  Anaerobic Soil Metabolism	_	_	Major degradates R-8, R-11	MRID:
45090023.

 Anaerobic Aquatic Metabolism 

	_	_	Major degradates R-11, R-4	MRID: 45621718.

 Terrestrial Field Dissipation	_	Detected in 0-7.5 cm layer	_	MRID:
45250909, 45621721, 45621722, 45621723.

The major degradates observed in the hydrolysis study were R-4 and R-7. 
In the aqueous photolysis study, the major transformation product was
R-11.  In the soil photodegradation study, the major transformation
products were R-3 and R-11.  In various aerobic soil metabolism studies,
various transformation products were observed: R-4, R-7, R-13, R-8 and
R-3.  Under anaerobic conditions R-11 was common to the anaerobic soil
metabolism study, and the anaerobic aquatic metabolism study. 
Furthermore, R-4 and R-8 were observed.  Important transformation
products of etoxazole appear to be R-4, R-7, and R-8.  Of these, R-8 is
more mobile and relatively persistent.  R-7 shows moderate mobility. 
There are uncertainties regarding the degradation products because,
different ones were observed in different studies, a closer inspection
of the transformation products yielded the proposed transformation
pathway that follows.  In general, the aerobic soil metabolism of
etoxazole proceeds via oxidation and hydroxylation of the dihydrooxazole
ring.  Further degradation of open ring moieties of etoxazole results in
benzene-ring cleavage via dehalogenation, halogen replacement,
oxygenolytic halogen-carbon bond cleavage, and ortho- and meta-cleavage.
 Ring cleavage is followed by halogen elimination, leading to
transformation into smaller molecules that are eventually mineralized to
CO2.

There is considerable uncertainty concerning the various degradates of
etoxazole (some of which appear to be relatively persistent).  The
absence of full environmental fate information about such degradates
constitutes an uncertainty at this time.

Drinking Water Exposure Modeling

  SEQ CHAPTER \h \r 1 

Models (Ref. 1)

SCIGROW v.2.3 (v 2.3, 8/5/03) (Screening Concentration in Ground Water)
is a regression model used as a screening tool to estimate pesticide
concentrations found in ground water used as drinking water.  SCIGROW
was developed by fitting a linear model to groundwater concentrations
with the Relative Index of Leaching Potential (RILP) as the independent
variable.  Groundwater 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 SCIGROW 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 (v 1.1.0, 12/18/07) (FQPA Index Reservoir Screening Tool) is a
metamodel of PRZM and EXAMS used as a screening tool to estimate
pesticide concentrations found in surface water used as drinking water. 
FIRST was developed by making multiple runs of PRZM using varying
sorption coefficients and determining the concentration in the EXAMS
index reservoir scenario after a two-inch single storm event.  (The
Index Reservoir is 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 by degradation or
effects of binding to soil in the field.  Additionally, FIRST can
account for spray drift and adjusts for the area within a watershed that
is planted with the modeled crop (Percent Cropped Area).   Spray drift
(modeled as 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. Despite being a single event model, FIRST can
account for spray drift from multiple applications.  The default
agricultural Percent Cropped Area (PCA) is 87%.  The PRZM scenario used
for FIRST development was among the most vulnerable, and thus resulting
surface water concentrations represent the upper bound values on the
concentrations that might be found in drinking water from the use of a
pesticide.  (Ref. 3 and 4)

For volatile and semi-volatile compounds, Tier I modeling will tend to
over-estimate surface water EDWCs because there are no parameters in
FIRST that explicitly take into account volatility (ie., no vapor
pressure or Henry’s Law inputs).  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 surface
water EDWCs, Tier II modeling will be able to refine these EDWCs by
including volatility, Henry’s Law, diffusion in air, and enthalpy
considerations.  Since SCIGROW is a regression model developed from
actual pesticide data with a range of volatilities, systematic
conclusions cannot be drawn about over or underestimation of groundwater
EDWCs at Tier I. 

Modeling Approach and Input Parameters

Etoxazole labels indicate that the worst case scenario is for hops. The
crop was chosen for this assessment because the label permits use of the
maximum application rate of 0.18 pounds active ingredient per acre at a
single application.  The assessment uses the default percent cropped
area (PCA) of 0.87.  Laboratory studies indicate that the major
mechanisms of degradation are metabolism, soil photodegradation and
aqueous photolysis.  Tables 5 and Table 6 summarize the input values
used in the model runs for SCIGROW and FIRST, respectively.  The lowest
non-sand Kd was used in FIRST.  The lowest Koc value was used in SCIGROW
because there was greater than three-fold variation in the values. 
There were seven available aerobic soil metabolism half-lives for
etoxazole, obtained in five soil types and two radiolabel positions. 
The upper confidence bound value (90th percentile) of the half-life was
used for the aerobic soil metabolism in FIRST.  The median half-life was
used in SCIGROW modeling.  The modeling results associated with maximum
allowable rate per year (0.18 lb a.i./A applied once) are presented in
Table 1.  Attached to this memorandum are copies of the original
printouts generated from FIRST and SCIGROW runs.

The primary transformation products of concern are R-8 and R-13 (as
requested by HED).   They were also simulated using the screening
models, FIRST and SCIGROW.  EFED had only limited environmental fate
data for these transformation products; however, mobility data, a very
important parameter in the screening models, were available.  It was
assumed that the transformation products were very persistent, and the
half-lives were set to stable to hydrolysis and to aqueous photolysis. 
There are five available aerobic soil metabolism studies for the parent
etoxazole.  Three of those studies provided useful data about the decay
of R-8 under such conditions.  Two studies provided useful data for
R-13.  Based on the decay of these degradates, half-lives were
estimated.  The upper confidence bound value (90th percentile) was used
in FIRST, and the mean value for SCIGROW.

R-8 reached a maximum of 44.2% of the applied parent in one aerobic soil
metabolism study. It is simulated by multiplying the label application
rate by 44.2%.  R-13 reached a maximum of 30.0% of the applied parent in
one aerobic soil metabolism study.   It is simulated by multiplying the
label application rate by 30.0%.  It is noted that by selecting the
highest percentage observed out of five studies, the results are likely
overestimations (particularly of the peak values), and represent
upper-bound estimates of the concentrations that might be found in
surface waters and ground waters due to the use of etoxazole on hops at
the maximum application rate.  In the FIRST simulation it was assumed
that the formulation was granular.  The reason is that FIRST assumes
that there is no spray drift for that type of formulation.  Drift is not
expected for a degradate formed in aerobic soil conditions.  The input
parameters for R-8 and R-13 are presented in Tables 5 and 6.  The
modeling results are shown in the Table 1. 

≥4        Mean n=3                  Mean n=2

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

Table 6. FIRST (v.1.1.0) input parameter values for etoxazole, R-8 and
R-13, use on hops1.

PARAMETER (units)	Value(s) for Etoxazole	Value(s) for R-8	Value(s) for
R-13	SOURCE	COMMENT

Application Rate (lb a.i./A)	0.18	0.0526(3)	0.0537(4)	Proposed label.
Refer to comments (3) and (4) below.

Number of Applications	1	1	1	Proposed label.	Represents
most-conservative scenario in which the total maximum rate per year is
applied in one application.

Interval between Applications (days)	N/A	N/A	N/A	Proposed label.	_

Percent Cropped Area (decimal)	0.87	0.87	0.87	Proposed label.	National
default.

Soil Partition Coefficient (Kd; (mL/g) or KOC (mL/gOC))	68 (9)	4.56 (9)
1082 (9)	MRID: 45090024, 45090026, 46299905, 46299906, 45250907,
45250908	(9) Represents the lowest non-sand Kd value among eight values
ranging from 66 to 335 mL/g.           Among three ranging from 1.24 to
4.56 mL/g         Among three ranging from 82 to 1082 mL/g. 

Aerobic Soil Metabolism Half-life (days)	26.9 (5)	473 (5)	715 (5)	MRID
45090019, 45090021, 45090022	(5)Upper confidence bound value, 90th
percentile, from 7 values.         From 3 values.            From 2
values.

Wetted in?	No	No	No	Proposed label.	_

Depth of Incorporation (inches)	0	0	0	Proposed label.	–

Method of Application	Ground spray	Ground/ Granular	Ground/ Granular
Proposed label.	Granular application for the degradates because drift is
not expected for the degradates.

Solubility in Water @ 20 OC, unbuffered (mg/L or ppm)	0.075	>>5.0 (2)
683 (2)	MRID# 45089902, 45089903, 45250907, 45250908	

_

Aerobic Aquatic Metabolism Half-life (days)	53.8 (6)	946 (6)	1430 (6)
MRID 45090019, 45090021, 45090022	(6) 2X the aerobic soil metabolism
input.

Hydrolysis Half-life @ pH 7 (days)	Stable 	Stable 	Stable 	MRID#
45090017	Relatively stable for etoxazole.  No data available for R-8 and
R-13, assumed stable.

Aquatic Photolysis Half-life  @ pH 7 (days)	28.8	Stable 	Stable 	MRID
46658101	No data available for R-8 or for R-13, assumed stable.

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

2. Water solubility was provided in the mentioned study for the compound
in 0.01 M CaCl2.

3. Maximum concentration observed in the aerobic soil metabolism study
by application rate by mole ratio = 

                                                                        
                                             
(0.442)(0.18)(237.4/359.42) = 0.0526

4. Maximum concentration observed in the aerobic soil metabolism study
by application rate by mole ratio =

                                                                        
                                              
(0.300)(0.18)(357.4/359.42) = 0.0537

The Percent Cropped Area (PCA) used was the national default of 0.87
(options for Tier I are national scale cotton, wheat, corn, soybeans, or
default; regional PCAs are a Tier II tool intended for refined
assessment). (Ref. 6)

Modeling Results

Table 7 provides a summary of the modeling results for all model runs.

Table 7.  Maximum Tier I Estimated Drinking Water Concentrations (EDWCs)
for drinking water risk assessment based on ground application of
etoxazole, based on one application on hops at 0.18 lb a.i./A.*

Chemical	

Acute EDWC   Surface Water FIRST (ppb)	

Chronic EDWC Surface Water  FIRST (ppb)	

Acute and Chronic EDWC Ground Water  SCIGROW (ppb)

Etoxazole	3.49	0.332	0.00173

R-8	2.80	0.913	0.316

R-13	0.802	0.0285	0.000322

* Results presented in ppb of the chemical, as opposed to ppb of parent
equivalent.

SCIGROW 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 one-in-10-year peak day concentration is used for acute endpoints
and the one-in-10-year annual average concentration 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 used.

Monitoring Data

No monitoring data are available for etoxazole.

Drinking Water Treatment

Due to relatively high adsorption of etoxazole (slightly mobile to
hardly mobile, KOC’s on the order of ~5000 to ~55,300 mL/g, FAO
classification), it is likely that primary treatment may reduce the
levels of etoxazole due to its tendency to bind.  However, there is no
information available at this time to determine the levels of reduction.
(Ref. 9) 

CONCLUSIONS 

There is considerable uncertainty concerning the various degradates of
etoxazole (some of which appear to be relatively persistent).  The
absence of full environmental fate information about such degradates
constitutes an uncertainty at this time; however, a conservative
approach was taken in this assessment in the absence of such data. There
is uncertainty in the role of the various competing dissipation and/or
degradation mechanisms of etoxazole.  In addition, various studies have
been deemed supplemental.

For this DWA, it has been assumed that at a given time, the maximum
amount of etoxazole has been applied to the field, and, at the same
time, certain amounts of R-8 and R-13 are applied by granular method. 
The EFED acknowledges that this method does not have mass balance, that
is, the amount of pesticide plus degradates applied exceeds the maximum
application rate.  However, the Division believes that the results
obtained are suitable for a screening level assessment.

Despite these facts, the EFED believes that this assessment is
conservative.  A more definitive assessment could be performed, using
Tier II aquatic models PRZM/EXAMS, and if additional data are obtained
from the registrant about the degradates of concern.

 

APPENDIX

Nomenclature:

Applicant's Code	IUPAC Chemical Names

Etoxazole/Oxazole
(RS)-5-tert-butyl-2-[2-(2,6-difluorophenyl)4,5-dihydro-1,3-oxazole-4-yl]
phenetole

R-3			N-(2,6-Difluorobenzoyl)-4-tert-butyl-2-ethoxybenzamide

R-4		
N-(2,6-Difluorobenzoyl)-2-amino-2-(4-tert-butyl-2-ethoxyphenyl)ethanol	

R-7			2-amino-2-(4-tert-butyl-2-ethoxyphenyl)ethyl-2'
,6'-difluorobenzoate hydrochloride

R-8			2-amino-2-(4-tert-butyl-2-ethoxyphenyl)ethanol

R-11			2,6-Difluorobenzoic acid			

R-12			4-tert-Butyl-2-ethoxybenzoic acid			

R-13			4-(4-tert-Butyl-2-ethoxyphenyl)-2-(2,6-difluorophenyl)-oxazole

R-15			4-tert-Butyl-2-ethoxybenzamide

DBF			2,6-Difluorobenzamide

Applicant’s Code	CAS Name, available for etoxazole only:

Etoxazole/Oxazole	2-(2,6-difluorophenyl)4-[4-(1,1-demethylethyl)
2-ethoxyphenyl-4,5-dihydrooxazole

Structure of Etoxazole

Output files from FIRST and SCIGROW:

                           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:Etoxazole

 time is  2/ 7/2007   7:23:29

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

  Application      Number of       Total Use    Koc      Soil Aerobic

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

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

      0.180           1.0           0.180      4.91E+03       20.5

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

 groundwater screening cond (ppb) =   1.73E-03 

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

 

                           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:R-8

 time is  2/ 7/2007   7:25:39

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

  Application      Number of       Total Use    Koc      Soil Aerobic

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

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

      0.053           1.0           0.053      1.03E+02      377.0

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

 groundwater screening cond (ppb) =   3.66E-01 

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

 

 

                          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:R-13

 time is  2/ 7/2007   7:27:26

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

  Application      Number of       Total Use    Koc      Soil Aerobic

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

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

      0.054           1.0           0.054      1.37E+04      256.0

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

 groundwater screening cond (ppb) =   3.22E-04*

 *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.

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

 

   

   RUN No.   1 FOR Etoxazole        ON   Hops          * INPUT VALUES * 

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

   RATE (#/AC)   No.APPS &   SOIL  SOLUBIL   APPL TYPE  %CROPPED INCORP

    ONE(MULT)    INTERVAL     Kd   (PPB )    (%DRIFT)     AREA    (IN)

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

   .180(   .180)   1   1      68.0   75.0   GROUND( 6.4)  87.0      .0

   FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

   METABOLIC  DAYS UNTIL  HYDROLYSIS   PHOTOLYSIS   METABOLIC  COMBINED

    (FIELD)  RAIN/RUNOFF  (RESERVOIR)  (RES.-EFF)   (RESER.)   (RESER.) 

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

     26.90        2          N/A     28.80- 3571.20    53.80     53.00

   UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

              3.486                       .332

   RUN No.   2 FOR R-8              ON   Hops          * INPUT VALUES * 

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

   RATE (#/AC)   No.APPS &   SOIL  SOLUBIL   APPL TYPE  %CROPPED INCORP

    ONE(MULT)    INTERVAL     Kd   (PPM )    (%DRIFT)     AREA    (IN)

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

   .053(   .053)   1   1       4.6    5.0   GRANUL(  .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.) 

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

    476.00        2          N/A       .00-     .00   946.00    946.00

   UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

              2.796                       .913

   RUN No.   3 FOR R-13             ON   Hops          * INPUT VALUES * 

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

   RATE (#/AC)   No.APPS &   SOIL  SOLUBIL   APPL TYPE  %CROPPED INCORP

    ONE(MULT)    INTERVAL     Kd   (PPM )    (%DRIFT)     AREA    (IN)

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

   .054(   .054)   1   1    1082.0  683.0   GRANUL(  .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.) 

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

    715.00        2          N/A       .00-     .00   ******   1430.00

   UNTREATED WATER CONC (NANOGRAMS/LITER (PPTr)) Ver 1.1.0 DEC 12, 2005

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

            802.038                     28.530

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

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) 

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er Assessments (12/01/1999)

Golf Course Adjustment Factors for Simulated Aquatic Exposure
Concentrations (06/01/2005)

  SEQ CHAPTER \h \r 1 Policy for Estimating Aqueous Concentrations from
Pesticides Labeled for Use on Rice (10/29/2002)

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

	10.      Food and Agriculture Organization of the United Nations.  FAO
PESTICIDE 		DISPOSAL SERIES 8.  Assessing Soil Contamination: A
Reference Manual.  	Appendix 2. Parameters of pesticides that influence
processes in the soil.  Editorial 	Group, FAO Information Division:
Rome, 2000.  	  HYPERLINK
"http://www.fao.org/DOCREP/003/X2570E/X2570E00.htm" 
http://www.fao.org/DOCREP/003/X2570E/X2570E00.htm  

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