Document ID: EPA-HQ-OPP-2007-0504-0009
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-09-15T04:00Z

U. S. ENVIRONMENTAL PROTECTION AGENCY

Washington, D.C. 20460

OFFICE OF

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

	

PC Code: 125851

DP Barcode: 341497

Date: March 18, 2010

MEMORANDUM	

SUBJECT:	Tier I Drinking Water Assessment for the Isoxaben Proposed New
Use on Bearing Nut Trees and Vineyards

 

TO:		Joanne Miller, Risk Manager 

		Kathyrn Montague, Risk Manager Reviewer

		Herbicide Branch

		Registration Division (7505P) 

		Dennis McNeilly, Risk Assessor

		Christina Swartz, Branch Chief

		RAB2

		Health Effects Division

	

FROM:	Chuck Peck, Environmental Engineer

		Environmental Risk Branch IV

		Environmental Fate and Effects Division (7507P)

REVIEWED

BY:		R. David Jones, Ph.D., Senior Agronomist

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)

A Tier I screening-level drinking water assessment was conducted for
isoxaben for the proposed new use on bearing nut trees and vineyards
(62719-00LIN).  Isoxaben (CAS 82558-50-7), an herbicide, is an active
ingredient in the pesticide FN-3133 (EPA Reg. No. 62719-00LIN) and a
number of other products (see Appendix A for complete list of labels). 
This drinking water assessment is limited to the exposure associated
with isoxaben alone and does not include exposure associated with other
active ingredients that may be combined with isoxaben.

The maximum proposed application rate for the proposed new use on
bearing nut trees and vineyards considered for this assessment is 1.0
lbs ai/acre/application, applied 1 time per year, for a maximum total
annual application rate of 1.0 lb ai/A/yr.  Isoxaben is formulated as a
dry flowable or granular product, or is incorporated into soil
fertilizer.  All applications are made by ground spray (dry flowable) or
drop or rotary spreaders (granular).  Because the maximum annual
application rate for the new use assessed here is less than the
application rate for ornamentals on the label for Isoxaben 75DF (EPA
Reg. No. 34704-917), the values for ornamentals are recommended for use
in the human health risk assessment.  The annual application rate for
ornamentals, which is used in this current assessment, is 3 lbs
ai/A/year with a 60 day re-treatment interval.

The estimated drinking water concentrations (EDWCs) are based on the
maximum proposed application rates specified in the product labels.  The
EDWCs for the human health risk assessment are presented in   REF
_Ref255384952 \h  \* MERGEFORMAT  Table 1 .  Because isoxaben has a
number of major degradates with similar toxicity as isoxaben, a total
toxic residue (TTR) approach was used in the modeling.  In the TTR
approach, half-lives are calculated for the combined isoxaben and
degradate residue and modeling runs are conducted using these
half-lives.  Additionally, a mobility study (MRID 41106303) and EPISuite
analysis indicated that several of the isoxaben degradates were more
mobile than the parent.  As such, two sets of modeling runs were
completed: one set using the mobility estimates of the parent and one
set using mobility estimates derived from the degradate study.  The
maximum 1-in-10-year peak and annual mean EDWCs in surface water were
284 and 120 µg/L, respectively, for ornamental use.  The maximum
estimated acute concentration in groundwater was 43.6 µg/L for
ornamental use.  The maximum 1-in-10-year peak and annual mean EDWCs in
surface water were 87.6 and 37 µg/L, respectively, for bearing nut
trees and vineyards.  The maximum estimated acute concentration in
groundwater was 14.5 µg/L for bearing nut trees and vineyards.

Table   SEQ Table \* ARABIC  1 . Tier I Estimated Drinking Water
Concentrations (EDWCs) resulting from applications of isoxaben and its
degradates on ornamentals and bearing nut trees.

Drinking water source (model)	Use 

(modeled rate)	Acute

(µg/L)	Chronic 

		(µg/L)

Parent Kd Data

Surface water (FIRST)	Ornamental	200	54.7

Groundwater (SCIGROW)	Ornamental	2.13	2.13

Surface water (FIRST)	Bearing nut trees and vineyards	61.5	16.9

Groundwater (SCIGROW)	Bearing nut trees and vineyards	0.71	0.71

Degradate Kd Data

Surface water (FIRST)	Ornamental	284	120

Groundwater (SCIGROW)	Ornamental	43.6	43.6

Surface water (FIRST)	Bearing nut trees and vineyards	87.6	37.0

Groundwater (SCIGROW)	Bearing nut trees and vineyards	14.5	14.5

Use Characterization

	Isoxaben is a pre-emergent benzamide herbicide used for control of
broadleaf (dicotyledonous) weeds.  The specific mode of action for
isoxaben is not well understood, but it has been shown to inhibit the
conversion of glucose to cellulose in the cell wall synthesis for
sensitive species, with grasses (Family: Poaceae) tending to be more
tolerant than other plant groups (Salihue et al. 1998).  Isoxaben is not
thought to be highly mobile in adult plants, limiting its toxicity to
older plants, but allowing efficacy in emerging seedlings.  

Maximum use pattern information is presented in   REF _Ref255384905 \h 
\* MERGEFORMAT  Table 2 .



Table   SEQ Table \* ARABIC  2 . Summary use information for isoxaben
proposed new use and ornamentals.

Use	Max. Single Application Rate 

(lbs. a.i./A)	No. of Application	Annual Application Rate 

(lbs. a.i./A/yr)	Interval Between Application (days)	Application Method

Ornamental	1.0	3	3.0	60	Ground spray

Bearing nut trees and vineyards	1.0	1	1.0	Not Applicable	Ground spray 

Environmental Fate and Transport Characterization

˚ C).  Isoxaben is classified as moderately mobile based on adsorption
Kd values in five soils ranging from 0.81 to 6.63 ml/g.  Major
degradates of isoxaben include hydroxyisoxaben, dimethoxybenzamide,
methoxyphenylpyrimidinol, and AEM hexenoylisoxaben.  Based on structural
analysis of these degradates in EPISuite, three of the degradates
(hydroxyisoxaben, dimethoxybenzamide, and AEM hexenoylisoxaben) have the
potential to be more mobile than isoxaben (Koc values ranging from 4.6
to 102 ml/goc), with methoxyphenylpyrimidinol appearing to be very
immobile (Koc values from 4,800 to 38,000 ml/goc).  The isoxaben
physical and chemical properties and the environmental fate source data
from submitted studies are presented in   REF _Ref239065349 \h  \*
MERGEFORMAT  Table 3 .  Properties and fate data for the major
degradates are presented in   REF _Ref255387192 \h  \* MERGEFORMAT 
Table 4 .

There is a potential for isoxaben and its degradates to reach surface
water through spray drift, as products may be applied via ground spray. 
Because isoxaben and its degradates are persistent in surface soils,
there is also the potential for them to reach surface water through
surface runoff either in solution or adsorbed to the soil.  Isoxaben and
its degradates have the potential to leach to ground water when applied
to certain soils, where high water tables are present, and high
rainfall/ irrigation occurs.

Table   SEQ Table \* ARABIC  3 . Physical/chemical properties and
environmental fate source data for isoxaben and its degradates.

Property	Value	Source 	Comments

Chemical Name	N-[3-(methylpent-3-yl)isoxazol
-5-yl]-2,6-dimethoxy-benzamide

Molecular Weight (g/mol)	332.39

Solubility in Water 

(mg/L @ 20 °C, pH 7)	1	MRID 40059506

	Vapor Pressure 

(torr @ 26 °C)	<3.9x10-7 torr  	MRID 40059506

	Octanol-water partition coefficient (K ow)	437	MRID 40059506

	Hydrolysis Half-life

(pH 7; 25C; in days)	no significant degradation	MRID 00250449

	Aqueous Photolysis Half-life (@ pH 7; in days)	6 (isoxaben)

6 - 15 (TTR1)	MRID 47140003	Two replicates were conducted.

Soil Photolysis Half-life (days)	49 (isoxaben)

63 (TTR)	MRID 47428403

	Aerobic Soil Metabolism Half-life (days)	161 (isoxaben, sandy loam, UK)

210 (isoxaben, silt loam, France)

277 (isoxaben, silt loam, Greece)

866 (isoxaben, sand, UK)

206 (TTR, sandy loam, UK)

342 (TTR, silt loam, France)

358 (TTR, silt loam, Greece)

1,116 (TTR, sand, UK)	MRID 47140004

	Anaerobic Soil Metabolism Half-life (days)	224 (isoxaben)

446 (TTR)	MRID 41106302

	Aerobic Aquatic Metabolism Half-life (days)	21 (isoxaben)

62-166 (TTR)	MRID 46393202	Two replicates were conducted.

Anaerobic Aquatic Metabolism Half-life (days)	18 (isoxaben)

265 (TTR)	MRID 46393201

	Freundlich Adsorption Coefficient (mL/g) (Kd)	0.81 (isoxaben, sand)

2.48 (isoxaben, sandy loam)

4.41 (isoxaben, loam)

6.63 (isoxaben, clay loam)

2.18 (isoxaben, loamy sand)

0.06 (hydroxyisoxaben, sand)

0.22 (hydroxyisoxaben, sandy loam)

0.37 (hydroxyisoxaben, loam)

0.84 (hydroxyisoxaben, clay loam)

0.3 (hydroxyisoxaben, loamy sand)	MRID 41106303

	Henry’s Law Constant 

(atm-m3/mol)	8.5x10-10	–	Estimated from vapor pressure, molecular
weight, and solubility.

1. TTR – total toxic residue. Isoxaben plus its degradates.

Table   SEQ Table \* ARABIC  4 . Physical/chemical properties and
environmental fate data for isoxaben and degradates.

Isoxaben / Degradate	Solubility (mg/L)	Log KOW	KOC1

(mL/gOC)	Source

Isoxaben	1	2.64	434	See Table 3

Hydroxyisoxaben	462	1.53	17-31

57	EPISuite 4.0

MRID 41106303

2,6-Dimethoxybenzamide	8.4x104	-0.22	4.9 – 10	EPISuite 4.0

Methoxyphenylpyrimidinol	41.2	3.56	4,800 – 38,000	EPISuite 4.0

AEM hexenoylisoxaben	265	1.71	21 - 102	EPISuite 4.0

1. Koc estimated in EPISuite using two methods: one using the Molecular
Connectivity Index and one using the Kow.  The range depicts the two
estimates.

Monitoring Data

Isoxaben is not included as one of the analytes monitored in U.S.
surface and groundwater under the USGS’s National Water Quality
Assessment (NAWQA) program (  HYPERLINK "http://water.usgs.gov/nawqa" 
http://water.usgs.gov/nawqa ). There were no detections in six surface
water and sediment samples collected and analyzed for isoxaben by
California Department of Pesticide Regulation (CDPR) in 2006 in
Stanislaus County.

Drinking Water Exposure Modeling

EDWCs were generated using EFED’s standard suite of models.  The FQPA
Index Reservoir Screening Tool (FIRST) is a surface water model that is
used to estimate both acute and chronic potential pesticide
concentrations in untreated drinking water. EDWCs from FIRST represent
concentrations which might occur from a single 1-in-10-year storm event
following the last application of pesticide at a location more
vulnerable than most locations in the United States to runoff,
regardless of the crop being produced. The model considers reductions in
dissolved concentration due to the percentage of the watershed which is
cropped (percent cropped area - PCA), due to adsorption of pesticide to
field soil and to reservoir bottom sediment, due to incorporation of the
pesticide at the time of application, due to degradation in soil before
washoff to the reservoir, and due to degradation of the pesticide within
the water body.  Reservoir water concentrations may be increased due to
deposition of spray drift into the feeding stream or directly into the
reservoir itself. FIRST is designed to mimic a more complex simulation
using the linked PRZM3 (Carsel et. al., 1997) and EXAMS 2.97.7 (Burns
et. al., 2000) models, but requires less time and effort to complete.  A
more detailed description of the index reservoir watershed can be found
in Jones et al., 1998.  The FIRST 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.  The RILP is a function of aerobic soil metabolism and the
soil-water partition coefficient.  The output of SCI-GROW represents the
concentrations of isoxaben 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,
2006).  

Input Parameters

	Input parameters for the FIRST and SCI-GROW models are listed in   REF
_Ref238874419 \h  \* MERGEFORMAT  Table 5  and   REF _Ref238874433 \h 
\* MERGEFORMAT  Table 6 , respectively.  For adsorption to soil, a
regression analysis of the adsorption coefficients versus the organic
carbon content yielded a p-value>0.1; as such, the Koc model was deemed
inappropriate and Kd values were used in the modeling.  Per EFED’s
Input Parameter Guidance, the mean value of the Kd values was used in
FIRST.  SCI-GROW, however, requires the use of the Koc value; as such,
the Koc value estimated from the regression analysis was used.

Table   SEQ Table \* ARABIC  5 . FIRST input parameters for isoxaben and
its degradates

Input Parameter	Value	Source	Comment

Application Rate 

(lbs a.i./A)	1.0	Isoxaben 75DF and FN-3133 labels

	Applications per Year	3 / 1	Isoxaben 75DF and FN-3133 labels	3 for
ornamentals, 1 for bearing nut trees and vineyards

Application Intervals (days)	60	Isoxaben 75DF label	Ornamentals only

Application Method	Ground	Isoxaben 75DF and FN-3133 labels

	Percent Crop Area	1.0

0.87	---

---	Assumption for non-ag uses (ornamental).

Default for agricultural uses.

Solubility in Water at 20oC (mg/L)	1.0	MRID 40059506

	Freundlich Adsorption Coefficient (mL/g) (Kd)	3.3 (isoxaben)

0.36 (hydroxyisoxaben)	MRID 41106303	Mean Kd value.1

Application Method	Ground	Isoxaben 75DF and FN-3133 labels

	Aerobic Soil Metabolism Half-life (days)	710 (TTR)	MRID 47140004
Represents the 90th percentile of the upper confidence bound on the mean
(450) of 5 TTR half-life values.1

Aerobic Aquatic Metabolism Half-life (days)	274 (TTR)	MRID 46393202
Represents the 90th percentile of the upper confidence bound on the mean
(114) of 2 TTR half-life values.1

Aqueous Photolysis

Half-life (days)	15	MRID 47140003	Maximum dark control corrected
half-life.1

1  EFED input parameter guidance is located at:
http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm

Table   SEQ Table \* ARABIC  6 . SCI-GROW2 input parameter values for
isoxaben and its degradates on ornamentals.

Input Parameter	Value	Source	Comment

Aerobic Soil Metabolism Half-life (days)	342 (TTR) 	MRID 47140004	Median
value per input parameter guidance.1

Organic Carbon Normalized Partition Coefficient  Koc	434 (isoxaben)

57 (hydroxyisoxaben)	MRID 41106303	Values derived from regression
analysis.

Application Rate (lb ai/A)	1	Isoxaben 75DF and FN-3133 labels	–

Maximum No. of Applications/Year	3 (ornamental)

1 (bearing nut tree and vineyard)	Isoxaben 75DF and FN-3133 labels	–

1  EFED input parameter guidance is located at:   HYPERLINK
"http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm" 
http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm 

Because isoxaben has a number of major degradates with similar toxicity
as isoxaben, a total toxic residue (TTR) approach was used in the
modeling.  However, a mobility study (MRID 41106303) and EPISuite
analysis indicated that several of the isoxaben degradates were more
mobile than the parent.  As such, two sets of modeling runs were
completed: one set using the mobility estimates of the parent and one
set using mobility estimates derived from the degradate study.

Exposure Modeling Results

	Tier I surface water and groundwater modeling results for isoxaben for
ground spray application to container-grown ornamentals are presented in
  REF _Ref255384858 \h  \* MERGEFORMAT  Table 7 .  These values are
recommended for use in the human health risk assessment.  Output values
for surface water for ornamentals are not modified using the percentage
crop area (PCA) adjustment factor since the value used is 1.0.  Output
surface water values for bearing nut trees and vineyards are modified
using the default agricultural PCA adjustment factor of 0.87.  Output
values for groundwater are not adjusted for a PCA.  The maximum
1-in-10-year peak and annual mean EDWCs in surface water were 284 and
120 µg/L, respectively, for ornamental use.  The maximum estimated
acute concentration in groundwater was 43.6 µg/L for ornamental use. 
The maximum 1-in-10-year peak and annual mean EDWCs in surface water
were 87.6 and 37 µg/L, respectively, for bearing nut trees and
vineyards.  The maximum estimated acute concentration in groundwater was
14.5 µg/L for bearing nut trees and vineyards.

Table   SEQ Table \* ARABIC  7 . Tier I Estimated Drinking Water
Concentrations (EDWCs) resulting from applications of isoxaben and its
degradates on ornamentals and bearing nut trees.

Drinking water source (model)	Use 

(modeled rate)	Acute

(µg/L)	Chronic 

(µg/L)

Parent Kd Data

Surface water (FIRST)	Ornamental	200	54.7

Groundwater (SCIGROW)	Ornamental	2.13	2.13

Surface water (FIRST)	Bearing nut trees and vineyards	61.5	16.9

Groundwater (SCIGROW)	Bearing nut trees and vineyards	0.71	0.71

Degradate Kd Data

Surface water (FIRST)	Ornamental	284	120

Groundwater (SCIGROW)	Ornamental	43.6	43.6

Surface water (FIRST)	Bearing nut trees and vineyards	87.6	37.0

Groundwater (SCIGROW)	Bearing nut trees and vineyards	14.5	14.5

DRINKING WATER TREATMENT

The EDWCs in this assessment are representative of concentrations in
drinking water source water (pre-treatment) and are derived from daily
instantaneous peak concentrations.  For surface water, the conceptual
model assumes that a pesticide reaches surface water via spray drift or
surface runoff, where it is instantaneously mixed and concentrations are
observed in the water body.  Isoxaben is relatively stable to
hydrolysis.  Therefore, isoxaben will not degrade by hydrolysis during
the time that elapses from drinking water intake through distribution to
the first tap. Because of its low Kd values, treatment methods such as
sedimentation, flocculation, and activated carbon, are not expected to
be effective at removing isoxaben.  However, isoxaben does degrade due
to photolysis and aerobic aquatic metabolism.  If ultraviolet light were
used as a means of disinfection, some degradation of isoxaben could also
be expected.  Additionally, while unlikely, if an aerobic digester were
used in the drinking water treatment train, some degradation may
potentially occur, depending on the retention time.  

CONCLUSIONS AND RISK CHARACTERIZATION

	Tier I drinking water exposure estimates are based on isoxaben maximum
use rates currently on the label for ornamentals and bearing nut trees
and vineyards. The maximum 1-in-10-year peak and annual mean EDWCs in
surface water were 284 and 120 µg/L, respectively, for ornamental use. 
The maximum estimated acute concentration in groundwater was 43.6 µg/L
for ornamental use.  The maximum 1-in-10-year peak and annual mean EDWCs
in surface water were 87.6 and 37 µg/L, respectively, for bearing nut
trees and vineyards.  The maximum estimated acute concentration in
groundwater was 14.5 µg/L for bearing nut trees and vineyards.

	The Tier I drinking water assessment was a screening-level assessment
based on simplified models and assumptions.  The modeling assessment
relied on maximum use patterns and national default PCAs to reflect
potential surface and groundwater concentrations.  To the extent that
actual use patterns are less than the labeled maximums and the
location-specific PCAs are less than assumed in this assessment, actual
environmental exposures could be lower.  As such, if EDWCs exceed levels
of concern, refinements can be made to this assessment to account for
regional use patterns. 

	Isoxaben was not detected in surface or ground water monitoring. 
However, monitoring data that is not targeted specifically in isoxaben
use areas or during times of known isoxaben use may not reflect
potential peak isoxaben concentrations that may occur in surface waters
when runoff events occur shortly after application.  

REFERENCES

Burns, L.A. 2000. Exposure Analysis Modeling System (EXAMS),
Environmental Research Laboratory, Office of Research and Development,
U.S. Environmental Protection Agency, Athens, GA.

R.F. Carsel, J.C. Imhoff, P.R. Hummel, J.M. Cheplick and J.S. Donigian,
Jr. 1997. PRZM-3, A Model for Predicting Pesticide and Nitrogen Fate in
Crop Root and Unsaturated Soil Zones: Users Manual for Release 3.0;
Environmental Research Laboratory, Office of Research and Development,
U.S. Environmental Protection Agency, Athens, GA.

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.  Online
at:   HYPERLINK "http://www.epa.gov/scipoly/sap/1999/index.htm" 
http://www.epa.gov/scipoly/sap/1999/index.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.  Online at:  
HYPERLINK "http://www.epa.gov/scipoly/sap/1998/index.htm" 
http://www.epa.gov/scipoly/sap/1998/index.htm 

Salihue, S., Hatzios, K.K., Derr, J.F. 1998. Comparative Uptake,
Translocation, and Metabolism of Root-Applied Isoxaben in Ajuga (Ajuga
reptans) and Two Ornamental Euonymus Species. Pesticide Biochemistry and
Physiology, 60:2 pp. 119-131

USEPA.  2009.  Guidance for Selecting Input Parameters in Modeling the
Environmental Fate and Transport of Pesticides.  U.S. Environmental
Protection Agency, Office of Prevention, Pesticides and Toxic
Substances, Office of Pesticide Programs, Environmental Fate and Effects
Division, Oct. 22, 2009.  Online at:   HYPERLINK
"http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm" 
http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm 

USEPA. 2002. SCIGROW: Users Manual. Online at:   HYPERLINK
"http://www.epa.gov/oppefed1/models/water/#scigrow" 
http://www.epa.gov/oppefed1/models/water/#scigrow  

MRIDs

MRID 00250449

Mosier, J.W. and Saunders, D.G. 1983. Hydrolysis of EL- 107 in buffer
solution. A Chapter within: EL-1 07. Application for 2-year EUP.
Unpublished study conducted by Lilly Research Laboratories, Greenfield,
Indiana. Sponsored and submitted by Elanco Products Company, A Division
of Eli Lilly and Company, Indianapolis, Indiana. Report No.:
I-EWD-82-05. Final report issued June 9, 1983.

MRID 40059506

Rutherford, B. 1986. Physical and Chemical Characteristics of Technical
Isoxaben. Laboratory Project ID BSR8506. Unpublished study performed and
submitted by Lilly Research Laboratories, Greenfield, IN.  Final report
issued October 22, 1986.

MRID 46393201

Sarff, P. and L.G. Heim. Anaerobic soil degradation of isoxaben. 2003.
Unpublished study performed by ABC Laboratories, Inc., Columbia, MO;
sponsored and submitted by Dow AgroSciences LLC, Indianapolis, IN. ABC
Study No.: 46880, Dow study No.: 010045 and Dow PTRNo.: 30258020-5562-1.
Final report issued May 23, 2003.

MRID 46393202

Sarff, P. 2003. Aerobic transformation of isoxaben in aquatic sediment
systems. Unpublished study performed by ABC Laboratories, Inc.,
Columbia, MO and Dow AgroSciences LLC, Indianapolis, IN; sponsored and
submitted by Dow AgroSciences LLC, Indianapolis, IN. ABC Study No.: 4688
1, Dow AgroSciences Study No.: 010044 and Dow AgroSciences PTR No.:
30258020-5037-1. Final report issued May 23, 2003.

MRID 41106302

Rainey, D.P. 1989. 14C Isoxaben anaerobic soil metabolism study.
Laboratory Project ID ABC-0224. Unpublished study performed and
submitted by Lilly Research Laboratories, Greenfield, IN.  Final report
issued May 4, 1989.

MRID 41106303

Saunders, D.G. and F.L. Powers. 1989. Soil adsorption and desorption of
isoxaben and soil metabolite 201469. Laboratory Project ID AAC8851.
Unpublished study performed and submitted by Lilly Research
Laboratories, Greenfield, IN.   Final report issued March 21, 1989.

MRID 47140003

Cook, W.L., F.R. Batzer and J.L. Balcer. Photodegradation of isoxaben in
aqueous buffer. Unpublished study performed, sponsored and submitted by
DowEIanco, Indianapolis, Indiana. Study ID No.: ENV93 144. Final report
issued March 25, 1996.

MRID 47140004

Huhtanen, K. and L. Heim. 2003. Aerobic soil degradation of isoxaben.
Unpublished study performed b ABC Laboratories, Inc., Columbia,
Missouri; sponsored and submitted by Dow AgroSciences LLC, Indianapolis,
Indiana. Lab Study ID.: 46879, Dow Study No. 010043. Final report issued
May 12, 2003.

MRID 47428403

Saunders, D.G., and F.L. Powers. 1996. Isoxaben photodegradation on
soil. Unpublished study performed, sponsored, and submitted by
DowElanco, Indianapolis, Laboratory Study ID No.: ENV95011. Final report
issued March 20, 1996.Appendix A. Current Isoxaben Labels

Trade Name	EPA Reg. No.	% Isoxaben	Maximum Single Application Rate

(lbs ai/A)	Maximum Annual Application Rate (lbs ai/A)	Retreatment
Interval (days)	Comments

FN-133

75.0	1.0	1.0	NA

	Propreen	961-370	0.375	1.0	3.0	60	Contains 1.5% trifluralin

Preen Landscape Mulch	961-408	0.0008	1.02

	Contains 0.0032% trifluralin

Isoxaben 75DF	34704-917	75.0	1.0	3.0	60

	Weed-Free 111	52287-13	0.05	1.0	3.0	60	Contains 0.2% trifluralin

Gallery 75 Dry Flowable	62719-145	75.0	1.0	3.0	60

	Snapshot 2.5TG	62719-175	0.5	1.0	3.0	60	Contains 2% trifluralin

Gallery Turf Fertilizer	62719-178	0.38	1.0	3.2

Turf Fertilizer (Gallery + Team)	62719-192	0.29	1.1	2.2	70	Contains
0.27% trifluralin and 0.53% benefin

T&O Fertilizer (Gallery + Team)	62719-280	0.38	1.0	2.0	70	Contains 0.39%
trifluralin and 0.76% benefin

Showcase	62719-516	0.25	0.5	1.5	60	Contains 2% trifluralin and 0.25%
oxyfluorfen

Turf Fertilizer (Gallery + Team) Pro	62719-565	0.38	1.0	2.0	70	Contains
0.5% trifluralin and 0.5% benefin

Snapshot 80	70506-53	20	1.0	3.0	120	Contains 60% oryzalin

Turf Fertilizer (Gallery + Surflam)	70506-55	0.29	0.7	2.0	90	Contains
0.86% oryzalin

Lawn 3iP Ready-to-Spray	72155-87	2.63	0.49	1.0	14	Contains 4.73% 2,4-D,
0.52% dicamba, and 1.1% mecoprop-p

Lawn 3iP Ready-to-Use	72155-88	0.069

Contains 0.31% 2,4-D, 0.033% dicamba, and 0.072% mecoprop-p

Appendix B. Model output files

SURFACE WATER MODELING OUTPUT FILES  - FIRST Results

  RUN No.   1 FOR isoxaben         ON   ornamental    * INPUT VALUES * 

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

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

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

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

  1.000(  2.833)   3  60       3.3    1.0   GROUND( 6.4) 100.0     0.0

   FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

   METABOLIC  DAYS UNTIL  HYDROLYSIS   PHOTOLYSIS   METABOLIC  COMBINED

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

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

    710.00        2           0.00   15.00- 1860.00  274.00     238.82

   UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.1  MAR 26, 2008

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

            199.498                     54.677

   RUN No.   2 FOR isoxaben         ON   nut tree      * INPUT VALUES * 

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

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

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

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

  1.000(  1.000)   1   1       3.3    1.0   GROUND( 6.4)  87.0     0.0

   FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

   METABOLIC  DAYS UNTIL  HYDROLYSIS   PHOTOLYSIS   METABOLIC  COMBINED

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

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

    710.00        2          N/A     15.00- 1860.00   274.00    238.82

   UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.1  MAR 26, 2008

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

             61.491                     16.869

   

RUN No.   3 FOR isoxaben         ON   ornamental    * INPUT VALUES * 

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

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

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

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

  1.000(  2.833)   3  60       0.4    1.0   GROUND( 6.4) 100.0     0.0

   FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

   METABOLIC  DAYS UNTIL  HYDROLYSIS   PHOTOLYSIS   METABOLIC  COMBINED

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

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

    710.00        2          N/A     15.00- 1860.00   274.00    238.82

   UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.1  MAR 26, 2008

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

            284.441                    120.023

   RUN No.   4 FOR isoxaben         ON   nut tree      * INPUT VALUES * 

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

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

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

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

  1.000(  1.000)   1   1       0.4    1.0   GROUND( 6.4)  87.0     0.0

   FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

   METABOLIC  DAYS UNTIL  HYDROLYSIS   PHOTOLYSIS   METABOLIC  COMBINED

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

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

    710.00        2          N/A     15.00- 1860.00   274.00    238.82

   UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.1  MAR 26, 2008

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

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

             87.587                     36.961

GROUND WATER MODELING OUTPUT FILES

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:Isoxaben

time is  3/15/2010   9:40:54

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

Application      Number of       Total Use    Koc      Soil Aerobic

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

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

1.000           3.0           3.000      4.34E+02      342.0

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

groundwater screening cond (ppb) =   2.13E+00

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

SciGrow version 2.3

chemical:Isoxaben

time is  3/15/2010   9:41:24

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

Application      Number of       Total Use    Koc      Soil Aerobic

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

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

1.000           1.0           1.000      4.34E+02      342.0

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

groundwater screening cond (ppb) =   7.11E-01

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

SciGrow version 2.3

chemical:Isoxaben

time is  3/15/2010   9:41:11

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

Application      Number of       Total Use    Koc      Soil Aerobic

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

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

1.000           3.0           3.000      5.70E+01      342.0

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

groundwater screening cond (ppb) =   4.36E+01

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

SciGrow version 2.3

chemical:Isoxaben

time is  3/15/2010   9:41:29

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

Application      Number of       Total Use    Koc      Soil Aerobic

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

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

1.000           1.0           1.000      5.70E+01      342.0

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

groundwater screening cond (ppb) =   1.45E+01

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

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