Document ID: EPA-HQ-OPP-2007-0940-0007
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-09-10T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

							     

								  PC Code: 071503								         	   DP Barcode: D342828,
348540

Date: March 12, 2008

MEMORANDUM	

SUBJECT:	Tier I Drinking Water Assessment for the Fludioxonil Proposed
New Use on Grapes; and the Proposed IR-4 New Uses on Tomato, Avocado and
Related Tropical Fruits, Herb Subgroup 19A, Root Vegetables, Leaves of
Root Vegetables, Lemon, Lime, Cucurbits, and Tuberous and Corm
Vegetables (Except Potato Subgroup, Except Yam)

 

TO:		Sidney Jackson, Risk Manager Reviewer

		Barbara Madden, Team Leader

		Minor Use Team

		Registration Division (7505P) 

Lisa Jones, Risk Manager Reviewer

Mary Waller, Team Leader

Fungicide Branch

Registration Division (7505P)

John Redden, Team Leader

ARIA

Registration Division (7505P)

	

FROM:	Cheryl Sutton, Ph.D., Environmental Scientist

		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)

EXECUTIVE SUMMARY

This memo summarizes the Tier I Estimated Drinking Water Concentrations
(EDWC) for fludioxonil in drinking water for the proposed Section 3 new
use on grapes, and the proposed IR-4 new uses on tomato, avocado and
related tropical fruits, herb subgroup 19A, root vegetables, leaves of
root vegetables, lemon, lime, cucurbits, and tuberous and corm
vegetables (except potato subgroup, except yam).  Fludioxonil (CAS
131341-86-1), a fungicide, is the active ingredient in the pesticides
SCHOLAR (EPA Reg. No. 100-969), Scholar EC Fungicide (EPA Reg. No.
100-1242), and Medallion® (EPA Reg. No. 100-769); and is an active
ingredient (along with cyprodinil) in the pesticide SWITCH® 62.5 WG
(EPA Reg. No. 100-953). Similar to previous assessments, this evaluation
is limited to the risks associated with fludioxonil alone and does not
include risks associated with fludioxonil in combination with
cyprodinil. 

The assessment is a Tier I screening-level assessment conducted using
the models SCIGROW and FIRST with maximum application rates. Additional
refinements of the assessment can be developed with higher tier
analysis, if requested by HED.

The maximum proposed application rate among the proposed new uses
considered for this assessment is 0.2188 lbs ai/acre/application,
applied four times per year with a 7-day reapplication interval
following the first application and a 21-day reapplication interval for
subsequent applications for a maximum total annual application rate of
0.875 lb ai/A/yr.  Application intervals are based on the label
recommendation for resistance management which states that application
of the fludioxonil-containing product should be alternated with another
fungicide with a different mode of action for two applications (after
the initial two applications).  All applications are by ground spray
with the exception of a single aerial application allowed for tropical
fruits in CA.

The application rate stated above is for all of the crops listed above
with the exception of lemon & lime, for which the maximum single and
total annual application rate is only 0.2188 ai/acre/application; repeat
applications are not allowed for these crops. A second exception is
tuberous and corm vegetables, for which fludioxonil is used as a
post-harvest treatment.  EFED assumes that the proposed post-harvest use
of fludioxonil is an indoor use that would represent a minimal risk to
drinking water; thus, no drinking water numbers are provided for this
proposed use. The IR-4 petition does not discuss how spent treatment
solution will be disposed; however, EFED presumes that spent treatment
solution will be disposed of in a manner that does not represent a means
of entry into drinking water or a route of exposure for non-target
plants and wildlife.   

The computer models FIRST (surface water) and SCI-GROW (groundwater)
were used to develop the EDWCs for use in the human health risk
assessment. Because the maximum application rates for the new uses
assessed here are less than the application rate for turf grass, the
values for turf grass are recommended for use in the human health risk
assessment. In a previous Tier 1 drinking water assessment for
fludioxonil on turf grass (drinking water memo of January 2, 2003; DP
Barcodes 285197, 285514, 286372, 286717), an application rate of 0.67
lb/acre applied 6 times was used. The registrant has indicated that this
rate applies to the product and not the active ingredient. The label
application rate for turf grass, which is used in this current
assessment, is three applications of 0.67 lb ai/A applied using 14-day
intervals, for a total application rate of 2 lb ai/A/yr. 

μg/L (ppb).  The estimated chronic concentration is 37.4 μg/L.  Values
were not corrected for the percentage crop area (PCA) because the
default for turf grass is 1.0.  The FIRST output file is attached.  As a
point of reference, the previously reported acute and chronic values
were 132 and 49 ppb.   

For groundwater sources of drinking water, the estimated concentration
of fludioxonil in shallow groundwater is 0.20 μg/L. The SCIGROW output
file is attached. As a point of reference, the previously reported value
was 0.35 ppb.  

Modeling results for fludioxonil in surface water and groundwater are
presented below in Table 1.  

Table 1.  Maximum Tier I Estimated Drinking Water Concentrations in
surface water based on fludioxonil use on turf grass at 2 lb ai/A/yr.   

DRINKING WATER SOURCE (MODEL USED) 	USE (rate modeled)	MAXIMUM ESTIMATED
DRINKING WATER CONCENTRATION  (EDWC)  ( ppb) 

Groundwater (SCIGROW)	Turf grass (0.67 lbs. a.i./A/applic. x 3 applic.;
total rate of 2 lb ai/A/yr )	Acute and Chronic	0.20

Surface Water  (FIRST)	Turf grass (0.67 lbs. a.i./A/applic. x 3 applic.;
total rate of 2 lb ai/A/yr )	Acute	81.3

	Turf grass (0.67 lbs. a.i./A/applic. x 3 applic.; total rate of 2 lb
ai/A/yr )	Chronic	            37.4

 This assessment is based on available environmental fate data.  There
are no significant data gaps in the environmental fate database
submitted by the registrant.  Although data are not available for
anaerobic aquatic metabolism, the anaerobic phase of the anaerobic soil
metabolism study indicates that fludioxonil is stable under such
conditions.

PROBLEM FORMULATION

This is a Tier I drinking water assessment (DWA) that uses modeling and
available monitoring data to estimate the groundwater and surface water
concentrations of pesticides in drinking water source water
(pre-treatment) resulting from pesticide use on sites that are
vulnerable.   Tier I DWAs are designed to screen out chemicals with low
potential risk for posing a drinking water concern.

ANALYSIS

Use Characterization

	Fludioxonil is a phenylpyrrole derivative of an antibiotic produced by
the soil-borne bacterium Pseudomonas. It is intended to control certain
post-harvest diseases caused by Monilinia fructicola and M. laxa (brown
rot), Botrytis cinerea (gray mold), and Rhizopus stolonifer (Rhizopus
rot). A suggested mode of action of phenylpyrroles derivatives is
inhibition of the trans-membrane transport associated with glucose
phosphorylation.  

Application information is presented in Table 2.

Table 2. Summary use information for fludioxonil proposed new uses and
turf grass. 

Use	Max. Single Applic. Rate             (lbs. a.i./A)	No. of Applic.
Annual Applic. Rate (lbs. a.i./A/yr)	Interval Between Applic. (days)
Applic. Method	Incorporation Depth (inches)

Multiple new use crops1	0.2188 lbs ai/A	4	0.875 lb ai/A/yr	7 days (1st
interval), then 21 days2	Ground spray3	Not Applicable

Lemon, lime	0.2188 lbs ai/A 	1	0.2188 lbs ai/A/yr	Not Applicable	Ground
spray 	Not Applicable

Tuberous and Corm Vegetables	16 oz. Scholar/ 100 gal water or wax/
emulsion	30-second dip	Not Applicable	Not Applicable	Post-Harvest Dip
Not Applicable

Grapes	0.2188 lbs ai/A	4	0.875 lb ai/A/yr	7 days	Ground spray (or aerial
in CA only for 1st applic.)	Not Applicable

Turf grass	3 apps of 0.67 lb ai/A 	3	2 lb ai/A/yr	14 days	Ground spray 
Not Applicable

1Tomato, Avocado and Related Tropical Fruits, Herb Subgroup 19A, Root
Vegetables, Leaves of Root Vegetables, and Cucurbits.  2Application
intervals are based on the label recommendation for resistance
management which states that application of the fludioxonil-containing
product should be alternated with another fungicide with a different
mode of action for two applications (after the initial two
applications). 3 All are applications are by ground spray with the
exception of a single aerial application allowed for tropical fruits in
CA.   

Environmental Fate and Transport Characterization

	Fludioxonil is persistent, with a laboratory soil metabolism half-life
of 220 days, and field dissipation half-lives ranging from 95 to 440
days.  Photolysis is a major route of degradation, with a (near-surface)
soil half-life of 1.6 days and an aqueous (near-surface) half-life of
8.7 days. Fludioxonil is slightly to moderately mobile (FAO
classification scheme) in soil (Koc = 991 - 2440 mL/goc) and is
primarily a concern for surface waters.  Degradates of fludioxonil are
highly mobile; however, none of the four major degradates are considered
to be of toxicological concern.   The fludioxonil physical and chemical
properties, and the environmental fate source data from submitted
studies are presented in Table 3.

There is a potential for fludioxonil to reach surface water through
spray drift, as the compound may be applied by ground spray and aerial
spray (in CA, limited crops).  Because fludioxonil is persistent in
surface soils, there is also the potential for it to reach surface water
through surface runoff either in solution or adsorbed to the soil. 
Based on the moderately high adsorption coefficients and the low
solubility (1.5 ppm), it is unlikely that there will be significant
contamination of surface water with fludioxonil through subsurface flow.

Table 3.  Physical/chemical properties and environmental fate source
data for fludioxonil.

-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine 	–	–

Molecular Weight	248.19	Product chemistry	–

Solubility in Water (20 °C)	1.5 mg/L

 	Product chemistry 	–

Vapor Pressure (20 °C)	5.33 10-9 Torr  	Product chemistry	–

Hydrolysis Half-life (pH 7; 25C)	Stable	MRID 43152502	–

Aqueous Photolysis Half-life (@ pH 7; in days)	8.7 	MRID 43496302 	–

Soil Photolysis Half-life (days)	1.6	MRID  43496303	(corrected for
natural sunlight at 40N latitude)

Aerobic Soil Metabolism Half-life (days)	143, 220, 183, 365, 365, 325,
239, 154 	 MRIDs 43380513, 47169301, 47169302a, 471693012, 471693013,
471693014  	–

Anaerobic Soil Metabolism Half-life (days)	0, 0 (stable)	MRIDs
47169302b, 47169303 	–

Aerobic Aquatic Metabolism Half-life (days)	0 (stable)	47169304	–

Anaerobic Aquatic Metabolism Half-life (days)	No Data	–	–

Soil Partition Coefficient (Kd)	8.64, 5.61, 21.3, 29.8 mL/g	MRID
44382311

	in sand (0.58% oc), sandy loam (0.23% oc), loam (2.15% oc), and loam
(2.38% oc)

Organic Carbon-Normalized Soil Partition Coeffic. (Koc)	 1490, 2440,
991, 1250 mL/goc	MRID 44382311	–

Henry’s Law Constant	1.16 x 10-9 atm-m3-mole-1

–

Bioconcentration Factor in Fish (BCF)	430X	MRID 44382320	–

Drinking Water Exposure Modeling

Models

An Estimated Drinking Water Concentration (EDWC) in groundwater was
estimated using EFED’s Tier I aquatic model SCIGROW (Screening
Concentration in Ground Water, version 2.3; 8/8/2003).  SCIGROW 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)

An Estimated Drinking Water Concentration (EDWC) in surface water was
estimated using EFED’s Tier I aquatic model FIRST (v1.1.0; 1/1/07). 
FIRST (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)

Modeling Approach and Input Parameters

Tier I modeling for the EDWC in surface water and groundwater from
fludioxonil use in a turf grass application pattern was conducted using
the maximum proposed application rate of 0.667 lbs a.i./A/application
applied three times at 14-day intervals for a total application rate of
2 lb ai/A/yr.  Physical/chemical properties and environmental fate
source data (from submitted studies) were presented in Table 3.  Input
values used for surface water modeling with FIRST are presented in Table
4.   Input values used for groundwater modeling with SCI-GROW2 are
presented in Table 5.  

Input parameter values used in this assessment were selected from the
environmental fate data submitted by the registrant and in accordance
with US EPA-OPP EFED water model parameter selection guidelines,
Guidance for Selecting Input Parameters in Modeling the Environmental
Fate and Transport of Pesticides, Version II, February 28, 2002.  d.,
Brit. Crop Protection Council, and The Royal Soc. of Chem. 1994). 

  SEQ CHAPTER \h \r 1 Table 4. FIRST (v1.1.0) input parameter values for
fludioxonil use on turf grass.

PARAMETER (units)	VALUE(S)	SOURCE	COMMENT

Application Rate (lb a.i./A)	3 apps of 0.67 lb ai/A 14 days apart or 6
apps of 0.333 lb ai/A 7 days apart).	Medallion Label	–

Number of Applications	3 or 6	Medallion Label	–

Interval between Applications (days)	7 or 14	Medallion Label	–

Percent Cropped Area (decimal)	1.0	Medallion Label	A PCA is not used for
turf grass.

Soil Partition Coefficient (Kd; (mL/g) or KOC (mL/gOC))	991	MRID
44382311	Represents the lowest non-sand Koc value among four values
ranging from 991 to 2440  mL/g. 

Aerobic Soil Metabolism Half-life (days)	294.9	MRIDs 43380513, 47169301,
47169302a, 471693012, 471693013, 471693014  	Represents the 90th
percentile of the upper confidence bound on the mean (249.3) of 8
half-life values.

Wetted in?	No	Proposed label.	–

Depth of Incorporation (inches)	0	Proposed label.	–

Method of Application	Ground spray	Proposed label.	–

Solubility in Water @ 20 OC, (pH 7; in mg/L or ppm)	1.5	Product
Chemistry	–

Aerobic Aquatic Metabolism Half-life (days)	0 (stable)	MRID 47169304	–

Hydrolysis Half-life @ pH 7, 25 OC (days)	0 (stable)	MRID 43152502	–

Aquatic Photolysis Half-life  @ pH 7 (days)	8.7	MRID 43496302	–

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

Table 5.  SCI-GROW2 input parameter values for fludioxonil use on turf
grass.

Model Input Parameter	Input Value and Unit	Source	Comments

Aerobic Soil Metabolism Half-life (days)	230	MRIDs   43380513, 47169301,
47169302a, 471693012, 471693013, 471693014  	Median value per EFED
guidance

Organic Carbon Normalized Partition Coefficient  Koc	1370	MRID 44382311
Input value is the median of four values, per EFED guidance.

Application Rate	0.67 lb ai/A/application (total of 2 lb ai/A/yr)

	Label  (Medallion Fungicide) 	–

Maximum No. of Applications/Year	3	Label	–

Modeling Results

	Tier I surface water and groundwater modeling results for fludioxonil
for ground spray application to turf grass are presented in Table 6. 
These values are recommended for use in the human health risk
assessment.  Output values for surface water are not modified using the
percentage crop area (PCA) adjustment factor since the default for turf
grass is 1.0.  Output values for groundwater are not adjusted for a PCA.

Table 6.  Maximum Tier I Estimated Drinking Water Concentrations (EDWCs)
for drinking water risk assessment based on ground spray application of
fludioxonil as used in a turf grass application pattern.

DRINKING WATER SOURCE (MODEL USED) 	USE (rate modeled)	MAXIMUM ESTIMATED
DRINKING WATER CONCENTRATION  (EDWC)  ( ppb) 

Groundwater (SCIGROW)	Turf grass (0.67 lbs. a.i./A/applic. x 3 applic.;
total rate of 2 lb ai/A/yr )	Acute and Chronic	0.20

Surface water  (FIRST)	Turf grass (0.67 lbs. a.i./A/applic. x 3 applic.;
total rate of 2 lb ai/A/yr )	Acute	81.3

	Turf grass (0.67 lbs. a.i./A/applic. x 3 applic.; total rate of 2 lb
ai/A/yr )	Chronic	            37.4

The SCIGROW concentration represents the groundwater concentration that
might be expected in shallow unconfined aquifers under sandy soils.  The
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.

Uncertainties and Data Gaps

This assessment is based on available environmental fate data.  There
are no significant data gaps in the environmental fate database
submitted by the registrant.  Although data are not available for
anaerobic aquatic metabolism, the anaerobic phase of the anaerobic soil
metabolism study indicates that fludioxonil is stable under such
conditions.

 

References

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

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

FIRST Users Manual (08/01/2001)

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

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

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



APPENDIX A

TIER I SURFACE WATER MODELING OUTPUT FILES

RUN No.   1 FOR fludioxonil      ON   turf grass     * INPUT VALUES * 

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

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

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

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

   .667(  1.937)   3  14     991.0    1.5   GROUND( 6.4) 100.0    .0

   FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

   METABOLIC  DAYS UNTIL  HYDROLYSIS   PHOTOLYSIS   METABOLIC  COMBINED

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

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

    294.90        2          N/A      8.70- 1078.80      .00   1078.80

   UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0  JAN 1, 2007

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

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

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OFFICE OF PESTICIDE PROGRAMS

U.S. ENVIRONMENTAL PROTECTION AGENCY

SCREENING MODEL

FOR AQUATIC PESTICIDE EXPOSURE

 

 SciGrow version 2.3

 chemical:fludioxonil

 time is  3/10/2008  14:44: 4

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

  Application      Number of       Total Use    Koc      Soil Aerobic

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

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

      0.667           3.0           2.001      13.70E+02      230.0

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

 groundwater screening cond (ppb) =   1.98E-01 

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

 

 PAGE   

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OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES