Document ID: EPA-HQ-OPP-2013-0504-0009
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2014-09-03T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION' PREVENTlON

 .

PC Code: 129112

DP Barcodes: 413801

MEMORANDUM	January 28, 2014

SUBJECT: 	Trifloxystrobin: Drinking Water Exposure Assessment in Support
of a Proposed

New Use on Dry Peas, Chickpeas, and Lentils (Reg. Nos. 264-776
(technical) and

264-1055).

TO: 	Christine Olinger, Branch Chief

Nancy Tsaur, Chemist

Risk Assessment Branch 3

Health Effects Division (7509P)

                                                  

Cynthia Giles-Parker, Branch Chief Tony Kish, Product Manager Dominic
Schuler, Reviewer Registration  Division (7505P)

FROM: 	Melanie Biscoe, Physical Scientist

Environmental  Risk Branch 3

Environmental Fate and Effects Division

THROUGH:

DanaSpatz,BranchChief 	h_	1/2."11Z.,.lt

Environmental Risk Branch 3 	'-

Environmental Fate and Effects Division (7507P)

Executive Summary

This drinking water assessment was conducted in response to Bayer
Corporation's request to register tri:floxystrobin for use on dry peas,
chickpeas, and lentils.  When considering this request, the
Environmental  Fate and Effects Division (EFED) determined  that a
currently registered use, turf,  continues to have the highest annual
use rate (1.33 lb a.i./acre) of all the proposed and existing uses
oftritloxystrobin, and would result in the highest estimated drinking
water concentrations (EDWCs).  This DWA takes into account
tri:floxystrobin plus a major

degradate, CGA-321113, as recommended by the Metabolism Assessment
Review Committee

(MARC)1 using the total toxic residue (TTR) approach.

Surface water and groundwater EDWCs for turf, using the TTR approach,
were previously developed in a 2010 drinking water assessment
(D378919).2  Since the 2010 assessment, EFED has implemented the use of
the PRZM-GW model to estimate groundwater concentrations. Therefore,
this assessment relies on surface water EDWCs from the 2010 DWA and
presents updated Tier I EDWCs for groundwater using the PRZM-GW model. 
Maximum surface water EDWCs from the 2010 DWA and maximum groundwater
EDWCs developed for this assessment are reported in Table 1.

The Tier I groundwater EDWCs for trifloxystrobin total toxic residues in
this assessment are greater than the surface water EDWCs from the 2010
DWA. The highest estimated peak (acute) concentration of total toxic
residues in groundwater is 427 μ?g/L, and the highest estimated
(chronic) concentration in groundwater is 365 μ?g/L (Table 1).  EFED
recommends using these values for the human health dietary risk
assessment.

Table 1. Maximum estimated drinking water concentrations (EDWCs) of
total toxic residues in parts per billion (μ?g/L) resulting from
applications of trifloxystrobin on turf at an annual application rate of
1.33 lb a.i./acre

                                     

			

1Drinking Water Assessment for Tolerance Petition for New Uses of
Trifloxystrobin in Trifloxystrobin Flowable

Fungicide [EPA Reg. No. 264-989].  D378919.

Background

Trifloxystrobin [E,E)-alpha-(methoxyimino)-2-[[[[1-[3-(trifluoromethyl)
phenyl] ethylidene]amino]oxy]methyl]-methyl ester] is an active
ingredient used in several agricultural fungicide products used to
control fungal pathogens on various grain, vegetable, fruit, nut crops,
ornamental plants, and turf.  It is used via aerial, chemigation and
ground applications, as well as in seed treatment.  Trifloxystrobin is
classified as an oximinoacetate fungicide in the strobilurin class.

                                                     1 Trifloxystrobin. 
Results of HED Metabolism Assessment Review Committee Meeting held
6/15/99.  DP Barcode

257835.  July 13, 1999.

2 Drinking Water Assessment for Tolerance Petition for New Uses of
Trifloxystrobin in Trifloxystrobin Flowable

Fungicide [EPA Reg. No. 264-989].  D378919.

The registrant, Bayer Corporation, requested new uses of trifloxystrobin
on dry peas, chickpeas, and lentils.  The proposed single application
rate for these new uses is 12.0 fluid ounces of product per acre, or
0.12 lb ai/acre.  The maximum annual application rate is 0.24 lb
ai/acre. The minimum re-application interval for these proposed uses is
10 days.

The currently registered turf use has the highest single and annual
application rates of all existing aerial, chemigation and ground uses of
trifloxystrobin.  The turf use has a single application rate over two
times higher than the proposed new uses on chickpea, dry peas and
lentils, and an annual application rate more than four times higher than
these proposed new uses.  It is therefore expected that EDWCs calculated
for the turf use would be protective of the proposed new uses

on chickpea, dry peas, and lentils.  Table 2 provides additional details
concerning the proposed uses as compared to the turf use.

The turf use was assessed most recently in 2010 using the TTR approach
(D378919), which considered drinking water exposures of parent
trifloxystrobin and its free acid degradate CGA-

321113.  The EDWCs from the 2010 assessment were 29 

Table 2. Comparison of Proposed Chickpea, Dry Peas, and Lentils Uses to
Existing Turf

                                                                        
                                                                        
                                                     Uses.

 

Use Site

Application

MethodMaximum

Single Application RateMaximum

Annual Application Rate

Maximum Applications Per Year1

Minimum Reapplication Intervallb ai/acrelb ai/acredaysProposed Use

Chickpea, Dry peas, LentilsAerial, Ground, and Chemigation equipment

0.12

0.24

2

10Existing UseTurf,

Residential, Commercial, or IndustrialAerial, Ground

Sprayer, Hand-held or Backpack Sprayer

0.34

1.08

3

14

Turf, golf courseAerial, Ground

Sprayer, Hand-held or Backpack Sprayer

0.34

1.08

3

14Ground Sprayer, Hand-Held or Backpack Sprayer

0.31

1.33

6 (4.3)

14

                                                     3 Drinking Water
Assessment for Tolerance Petition for New Uses of Trifloxystrobin in
Trifloxystrobin Flowable

Fungicide [EPA Reg. No. 264-989].  D378919.

                                                                        
                    

Environmental Fate and Transport Characterization

The environmental fate and physiochemical properties of trifloxystrobin
and its major

degradation product CGA-321113 are summarized in Table 3 and Table 4,
respectively. Table 4

also includes the aerobic soil metabolism half-life for the total toxic
residues.  Chemical structures for trifloxystrobin and CGA-321113 are
available in Appendix 1.

Parent: Trifloxystrobin

Trifloxystrobin has a low solubility (0.61 mg/L @ pH 7) in water. The
vapor pressure is 2.55 x

10-8 torr at 25 

Trifloxystrobin is non-persistent in soil. Laboratory studies indicate
that biotransformation is an important route of trifloxystrobin
transformation in aerobic soil. Trifloxystrobin degraded rapidly in
aerobic soils with half-lives ranging between 0.41 and 0.91 days. In
aerobic soils the major degradate is CGA-321113. Photodegradation in
soil results in the isomerization and subsequent formation of
CGA-321113. The photo-induced isomerization half-life (t1/2) was 2.1
days on soils. Based upon the soil organic carbon coefficient, Koc
(median Koc =2709 mL/goc), trifloxystrobin would fall into the slightly
mobile class4.

Laboratory studies indicate that trifloxystrobin is also not persistent
in water. Hydrolysis of trifloxystrobin is dependent on pH; while
trifloxystrobin is stable to hydrolysis under acidic conditions (pH 4),
it readily hydrolyzes to CGA-321113 in alkaline conditions (t1/2 = 55.2
days at pH 7 and 0.83 days at pH 9). In the aquatic environment, the
photo-induced isomerization half- life (t1/2) was 14.8 days. In an
aerobic aquatic sediment system, the major transformation product was
CGA-321113.

Trifloxystrobin demonstrated a biphasic degradation pattern in field
dissipation studies

conducted in California, New York, and Georgia.  For the first
degradation phase, trifloxystrobin half-life values ranged from 1.9 to
24 days.  In the second degradation phase, half-life values ranged from
6.5 days to 4 months.

Degradate of Concern: CGA-321113

CGA-321113 is the major transformation product identified in
trifloxystrobin soil metabolism studies.  Fate studies indicate that
CGA-321113 is quite persistent in soil (DT50 250 to 350 days) and
aquatic environments (DT50 = 289 days).  It is stable to hydrolysis and
metabolism;

therefore, CGA-321113 is expected to degrade at a slower rate than
trifloxystrobin in both soil

and water.  The aqueous solubility for CGA-321113 (30.9 mg/L) is three
orders of magnitude higher than the aqueous solubility for
trifloxystrobin. CGA-321113 is a carboxylic acid, and therefore being
anionic, is expected to be more mobile than parent trifloxystrobin. The

                                                                        
                    

adsorption/desorption mobility classification of CGA-321113 is mobile to
moderately mobile5. Because of its persistence and mobility, CGA-321113
has greater potential for leaching than trifloxystrobin.

In contrast to laboratory data, CGA-321113 was not detected above 0.02
percent of the applied amount in leachates from a field lysimeter study.
In field dissipation studies conducted in Georgia, California, and New
York, under bare ground and cropped conditions, CGA-321113
concentrations reached or were slightly above the Limit of Quantitation
of 10 30-36 inch soil segments.

                                        

Table 3. Chemical Properties and Environmental Fate Parameters For
Trifloxystrobin.

a USEPA Fact Sheet reports 3.4 x 10-6 torr (@25 b PMRA Reg2004-03 and
Trifloxystrobin (213) report 3.4 x 10-6 Pa @ (@25                       
                 

Table 4. Chemical Properties and Environmental Fate Parameters For
CGA-321113 and Residues of Concern (trifloxystrobin + degradate
CGA-321113).

 Parameter Values1 Source CGA-321113 Molecular Formula C19H17F3N2O4 MRID
44496801 Molecular Weight 394.35 MRID 44496801 Solubility @ 20 ◦?C
30.9 mg/L MRID 44496816 Vapor Pressure 7.5 x 10-08 mm Hg @ 20 ◦?C MRID
44496801 Henry’s Constant 1.26 x 10-09   atm m3 mol-1 Hydrolysis
Half-life Stable MRID 44496727 Aquatic Photolysis Half-life Stable MRID
44496727 Photolysis on soil Half-life Stable MRID 44496727 Aerobic
Aquatic Metabolism Half- life Stable MRID 44496734 Anaerobic Aquatic
Metabolism

Half-lifeStableMRID 44496733Organic Carbon Partition

Coefficient (Koc) (mL/g)127, 235, 130, 48, and 80

mean 124.0 mL/goc

median 127 mL/goc

Coef. Determination (r2) = 0.89 for

Kf   vs. omMRID 44496801Soil Partition Coefficient (Kf) (mL/g)Kf
(texture class)

4.0	Loam (5.4% om)

1.9	Sand

3.2	Clay loam

0.28	Sandy loam (1% om)

0.65	Sandy loam

mean = 2.0 mL/g

[1/n = 0.81 to 0.85]MRID 44496801Persistence for Residues of Concern
(parent trifloxystrobin + CGA-321113)(DP D309489 see Table 9)[Residues
of Concern]:

Aerobic Soil Metabolism Half-life254.8 days

271.3 days

199.7 days

282.75 days

(90th percent upper bound on mean) Median = 254.8 daysMRID 44496732

MRID 44496730

MRID 44496731Models and Model Scenarios Used

Detailed descriptions, documentation, and links for running the exposure
models used in this assessment may be found at     HYPERLINK
http://www.epa.gov/oppefed1/models/water/index.htm  
http://www.epa.gov/oppefed1/models/water/index.htm.

Groundwater EDWCs for total toxic residues of trifloxystrobin resulting
from the turf use were derived with PRZM-GW (Pesticide Root Zone Model
for Groundwater, version 1.0, August 31,

2012), using the GW-GUI (Graphical User Interface, version 1.0, August
31, 2012).  EDWCs for the Screening Concentration in Groundwater model
were calculated in a 2010 DWA and are reported in this assessment
(SCI-GROW v2.3, compiled 08/08/03).6   Surface water EDWCs

were derived using PRZM/EXAMS as described in the 2010 DWA.

Model Input Parameters

The model input parameters for PRZM-GW are summarized in Table 4.  Model
input values were prepared following EFED input guidance7,8.

For each PRZM-GW scenario, EDWCs were calculated for each year in a
30-year simulation where trifloxystrobin was applied at the maximum
label rate for 30 consecutive years.  The initial application date was
assumed to be the date of emergence for the PRZM-GW scenario used. 
Figure 1 is the PRZM-GW User Interface that shows the model inputs for
the trifloxystrobin total toxic residues and illustrates how multiple
applications were included in the modeling.

Table 4. Input Values Used to Model Total Toxic Residue EDWCs in
Groundwater for the

Trifloxystrobin Turf Use.

 

Model Input Parameter

PRZM-GW Input Value and Unit

Source/Comments

Maximum Application Rate

0.347 kg a.i./ha for the first four applications, 0.101 kg a.i./ha for
the fifth application for an annual application rate of 1.489 kg
a.i./haLabel; Corresponds to four applications of 0.31 lb a.i./acre and
a fifth application of 0.9 lb a.i./acre

for an annual application rate of

1.33 lb a.i./acre.

Maximum Number of Applications

5

The label indicates 6 applications may be made, but not at the maximum
single application rate.

                                                     6 Drinking Water
Assessment for Tolerance Petition for New Uses of Trifloxystrobin in
Trifloxystrobin Flowable

Fungicide [EPA Reg. No. 264-989].  D378919.

7 Parameters are selected as per Guidance for Selecting Input Parameters
in Modeling the Environmental Fate and

Transport of Pesticides; Version 2.1, October 22, 2009.

8 Baris, R.; Barrett, M.; Bohaty, R.; Echeverria, M.; Kennedy, I.;
Malis, G.; Wolf, J.; Young, D. PRZM-GW Input

Parameter Guidance; Health Canada, U.S. Environmental Protection Agency,
October 12, 2012.

 

Model Input Parameter

PRZM-GW Input Value and Unit

Source/Comments

Method of Application

CAM 1, Bare Ground

Label

Date of Initial Application

120 days post-emergence

Emergence dates are specified in each PRZM-GW scenario.

Minimum Interval between

Applications

14 days

Label

Soil Partition Coefficient Koc

(CGA-321113)

124 mL/goc

(mean)

MRID 44496801

Hydrolysis Half-Life

(CGA-321113)

Stable

MRID 44496727

Aerobic Soil Metabolism Half-Life

(parent trifloxystrobin + CGA-

321113)

282.75 days

(90th percent upper bound on mean)

MRID 44496732

MRID 44496730

MRID 44496731Figure 1. Trifloxystrobin - Example of PRZM-GW User
Interface and Inputs for Foliar

Applications to Turf.

                   

Modeling Results

Table 5 reports the EDWCs calculated for each PRZM-GW (i.e.,
groundwater) scenario for applications at 120 days post-emergence. EDWCs
calculated for 0- and 60-days post-emergence were also calculated and
yielded EDWCs approximately 10-30 427 

EDWCs for the turf use were calculated using SCI-GROW in the 2010 DWA,
which resulted in acute and chronic EDWC of 5.87 

EFED recommends using the maximum peak and post-breakthrough average
concentrations from the 30-year PRZM-GW simulation for the Wisconsin
corn scenario for human health risk assessment (i.e., 427 and 365
μ?g/L). and are not expected to be greater than

Table 5. Tier I PRZM-GW Total Toxic Residue Estimated Drinking Water
Concentrations

(EDWCs) for 30 Years for the Trifloxystrobin Turf Use.

 

Scenario

Peak (

Throughputs*First Application 120 Days Post‐?EmergenceFL
Citrus24118712508.8DMV Corn25820212398.8FL Potato554928623.8GA
Peanuts1139630233.6NC Cotton25021620565.3WI
Corn42736528483.8*Throughputs are the estimated pore volumes/retardation
factors that occur in the simulation.

                                                     9 Drinking Water
Assessment for Tolerance Petition for New Uses of Trifloxystrobin in
Trifloxystrobin Flowable

Fungicide [EPA Reg. No. 264-989].  D378919.

Figure 2. PRZM-GW Wisconsin Corn Scenario Time Series Graph for 30 Years

Trifloxystrobin Application to Turf (ppb is equivalent to               
    

Tier I PRZM-GW Modeling Assumptions

In estimating pesticide concentrations in water resources, OPP uses a
tiered screening approach involving a combination of models and
monitoring data. The intent of the screening approach is to estimate
pesticide concentration in water from sites that are highly vulnerable
to runoff or leaching so that the program can be confident that any
pesticide that passes the screening tiers poses a low possibility of
harming human health, wildlife, or the environment. Failing a tier,
however, does not necessarily mean the chemical is likely to cause
health or environmental problems, but rather that there is a need to
move to a higher tier and conduct a more refined assessment. This tiered
modeling system is designed to provide a thorough analysis of each
pesticide, while at the same time focus OPP's efforts on those
pesticides that pose the greatest potential risk.

In this assessment, PRZM-GW is used as a Tier-1 screen.  In other words,
the modeling conducted for this assessment preserves default
conservative assumptions in the PRZM-GW model.  As such, Tier 1 PRZM-GW
modeling is expected to result in conservative groundwater EDWCs that
would rarely, if ever, occur in the environment.

Depending on the Tier I results, Tier II (or “refined”) EDWCs may be
modeled to take into account usage data, well setback requirements,
additional fate inputs, and an exposure duration specific to the
exposure duration of concern for humans.  A more representative scenario
may also be developed as part of Tier II EDWC modeling.  This assessment
has not calculated Tier II EDWCs using PRZM-GW, and thus does not
consider trifloxystrobin usage data, well setbacks, additional fate
inputs, specific exposure durations, or new scenario development.  For
more information on potential Tier II refinements in PRZM-GW modeling,
see     HYPERLINK
http://www.epa.gov/oppefed1/models/water/przm_gw/wqtt_przm_gw_guidance.h
tm)  
http://www.epa.gov/oppefed1/models/water/przm_gw/wqtt_przm_gw_guidance.h
tm).

The default PRZM-GW assumptions used in calculating Tier I groundwater
EDWCs for trifloxystrobin total toxic residues include the following:

?	Trifloxystrobin is used at the maximum labeled rate for 30
consecutive years.

?	There are no well setbacks.

?	Removal of the pesticide via runoff or erosion is negligible.

?	The saturated zone is a shallow (<100 feet), unconfined aquifer
with a water table depth that corresponds to its respective scenario
location.

?	The well screen extends from the aquifer surface to 1 meter below
the aquifer surface.

?	The pesticide undergoes aerobic soil metabolism in the top 10 cm of
soil; the aerobic soil metabolism rate declines linearly to 1 meter
below the soil surface, below which only abiotic degradation processes
(i.e., hydrolysis) occur.

These assumptions are designed to introduce a high level of protection
into the modeling results.

Monitoring Data

Surface water and groundwater data from one state and three nationwide
pesticide monitoring programs were reviewed to provide additional
context concerning the potential presence of trifloxystrobin in drinking
water resources.  These water monitoring programs do not target sample
collection to peak use locations or application times for particular
pesticides, nor do they target sample collection to high precipitation
events (i.e., high-runoff events).  Additionally, the sampling frequency
in these monitoring programs was not designed to capture peak
concentrations.  Therefore, the monitoring data reported by these
programs may not represent the highest concentrations in drinking water
source water, and are considered qualitative information for the
purposes of this drinking water assessment.

 USGS-EPA Pilot Reservoir Monitoring Program - Trifloxystrobin and
CGA-321113 data were not analyzed as part of this program.

 USGS National Water-Quality Assessment (NAWQA) Program Data -
Trifloxystrobin data were available from USGS NAWQA surface water and
sediment data.  Surface water detections were from Cobb and Coweta
counties in Georgia in 2010 (2 samples with detections less than 4.7
ng/L), Cameron County in Texas in 2013 (1 sample with a detection less
than 2 ng/L), and San Joaquin and Sacramento Counties in California in
2012 (11 samples with detections less than 4.7 ng/L).  In Georgia’s
Cobb, Coweta, and Sumter counties, sediment samples taken from 2010 to

2011 had trifloxystrobin detections less than 1.4 ug/kg. 
Trifloxystrobin was not detected in groundwater.  NAWQA has not analyzed
surface water or groundwater samples for CGA-

321113.  NAWQA program data are available at     HYPERLINK
http://infotrek.er.usgs.gov/nawqa_queries/index.jsp  
http://infotrek.er.usgs.gov/nawqa_queries/index.jsp.

 California Surface Water Monitoring Program Data - The California
Surface Water Monitoring Program represents pesticide occurrence data
for surface waters in the Sacramento Valley, San Joaquin Valley, and
other locations in the state. The California surface water and
groundwater monitoring data included a total of 43 surface water
detections for trifloxystrobin, all below the level of quantitation
(LOQs of 0.02 to 0.05 μ?g/L) from Colusa, Sutter, Yolo and Yuba
counties from 2006 to 2008.  The California Surface Water Monitoring
Program has not analyzed surface water or groundwater for CGA-321113. 
California Surface Water Monitoring Program data are available at    
HYPERLINK http://www.cdpr.ca.gov/docs/emon/surfwtr/surfdata.htm  
http://www.cdpr.ca.gov/docs/emon/surfwtr/surfdata.htm.

 Pesticide Data Program (PDP) Data - The PDP drinking water monitoring
project provides non- targeted pesticide occurrence data in raw water,
finished water (treated/tap), and groundwater in the United States.  The
PDP has not analyzed surface water or groundwater for detections of
trifloxystrobin or CGA-321113.  PDP data are available at     HYPERLINK
http://www.ams.usda.gov/AMSv1.0/pdp  
http://www.ams.usda.gov/AMSv1.0/pdp.

Appendix 1.  Chemical Structures for Trifloxystrobin and CGA-321113

 Trifloxystrobin

                   

 CGA-321113