### Page **1** 

## of14 **UNITED STA** 

**TES ENVIRONMENTAL**  **PROTECTION AGENCY**  **WAS H**  **I NGTO**  **N D**  **. C**  **., 20460**  OFFICE OF CHEMICA L SAFETY AND POLLUTION' PREVENTlON



### . .. PC Code: 1 29112 

## DP Barcodes: 413801 **MEMORANDUM** January 28, 2014 **SUBJECT:** Trifloxystrobin: Drinking Water Exposure Assessme n t in Support of a Proposed New Use on Dry Pea s , Chickpeas, and Le ntils (Reg. Nos. 26 4 - 776 (technical) and 264 - 1055). **TO:** Christine Olinger, Branch Chief

Nancy Tsaur, Chemist Risk Assessment Branch 3 Health Effects Division (7509P) Cy nth i a Giles - Parker, Branch Chief Tony Kish, Product Manager Dominic Schuler, Reviewer Regi s t ration Division (7505P) **FROM:** Melanie Biscoe, Physical S c ientist

Environmental Risk Branch 

### 3 Environmental Fate and Effects Division **THROUGH:** 

## DanaSpatz,BranchChief 

# h_ 1/2." 1 

# 1 Z.,.lt Environmental Risk Branch 

### 3 ' - Environmental Fate and Effects Division (7507P) **Executive Summary**  This drinking water assessment was conducted in response to Bay er Corporation's re q u est to register tri:floxystrobin for use on dry peas, chickpeas, and lent i l s. 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:floxys t r obin plus a maj o r

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**Drinki n**  **g wat**  **e r**  **source (**  **m ode**  **l )**  **Model Scena r**  **io & Application**  **Method Acu**  **t e**  **Ch r**  **o n**  **i c**  **C a**  **ncer Unit**  **s :**  **μ /L**  Surface Water 1 (P RZM - EXAMS) Penn syl v an ia T urf scenar i o Aerial Ap p licati o n Peak 1 - i n - 1 0 Ye ar C hr on i c

1 - i n - 1 0 Ye ar 30 - year Annu a l

Av e r a g e 2 9 ppb 2 3 ppb 1 9 ppb Gr o un dwat e r (PRZ M - G W 3 0 - y ear s i m u lati on) W i sconsin Corn scenar i o Gr o und Ap p licati o n Peak Post - B reak through Aver a g e 4 2 7 p pb 3 6 5 p pb 

### degradate, CGA - 321113, as recomm e nded by the Metab o lism Assess m ent Review Committee (MARC ) 1 

### using the t o tal toxic residue (TTR) approach. Surface water and groun dwater EDWCs for turf, using the T TR approach, were pre v iously developed in a 2010 drinking water assess m ent (D378919) . 2 

### Since the 2010 assess m ent, EFED has i m pl e m ented the use of the PRZM - GW m od e l to esti m ate groundwater concentrations. Therefore, this assess m e nt relies on surface water EDWCs from the 2010 DWA and presents updated Tier I ED W Cs for groundwater using th e PRZM - GW m odel. Maxi m um surface water EDWCs from the 2010 DWA and maxi m um groundwater E D WCs developed for this assess m ent are reported in Table 1 

### . The Tier I groundwater EDWCs for trifloxy strobin total toxic residues in this assess m e nt are greater th an the surface wat e r EDWCs from the 2010 DWA. **The highest estim a**  **ted peak**  **(acute) concentration of total toxic residues in groundwater is 427 μ**  **g/L, and the highest estimated (chronic)**  **concentration in ground**  **w ater is 365**  **μ g/L (Table 1). EFED**  **recommends using the s**  **e values for the human health diet a**  **ry ri s**  **k assessment.**  **Table 1.**  **Maximum estimated**  **drinking water**  **con c**  **entrations (EDWCs)**  **of total**  **toxic residues**  **in parts**  **per billion**  **( μ**  **g/L) resulting**  **from applications**  **of trifloxystrobin**  **on turf**  **at an**  **annual application**  **r a**  **te of**  **1.33 lb**  **a.i./acre**

1 Drinki ng W at er Assess m e nt f o r T o leran ce Petiti o n f

o r New U s es of Trifl ox y stro b in in Triflo x y stro b i n Flowab le F ungicide [ EP A R e g. N o . 26 4 - 9 89 ] . D3 7 89 1 9 . 

### Background Triflox ys trobin [E,E) - alpha - ( m ethox yi m i n o ) - 2 - [[[[1 - [3 - (trifluoro m ethyl) phenyl] ethylidene]am ino]ox y] methyl] - m eth yl ester] is an active ingredient used in several agricultural fungicide products used to contr o l fungal pathogens on various grain, vegetable, fruit, nut crops, ornam ental plants, and turf. It is used via aerial, che m igation and ground applications, as well as in seed treatm ent. Trifloxy strob i n is classified as an oxi m i noace t ate fungicide in the strobilurin class.

1 Tri f l ox y stro bin. Results of HED M etab o lism Assess m ent Revie w C o mm ittee M eeting held 6 / 15 / 9 9 . DP B a rc o d e 2 57 8 3 5 . Ju l y 1 3 , 1 99 9 . 2 Dr ink i n g Water Assess m e nt f o r T o leran ce Petiti o n f

o r New U s es of Trifl ox y stro b in in Triflo x y stro b in Flowab le F ungicide [ EP A R e g. N o . 26 4 - 9 89 ] . D3 7 89 1 9 .

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The registrant, Bay er Corporation, requested new uses of triflox ys trobin 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/ac re. The m ax i m um annual application rate is 0.24 lb ai/acre. The m i n i m um re - application interval for these proposed uses is 10 day s. The currently

registered turf use has the highest single and annual applicat i on rates of all existing aerial, che m ig ation and ground uses of triflox ys trob i n. 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 ti m es higher than these propo s ed new uses. It is therefore expected that ED W Cs c a lculated for the turf u s e would be protective of the proposed new uses on chickpea, dry

peas, and lentils. **Table 2** provides additional detai l s concerning the proposed uses as co m

pared to the turf use. The turf use was assessed m ost rece ntly in 2010 u sin g the T T R approach (D378919), which considered drinking water exposures of parent trifloxy strobin and its free acid degradate CGA 321113. The EDWCs f

r om the 2010 assess m ent were 29 μg/L(1 - in - 10 - ye ar peak), 23 μg/L (1 - in - 10 - ye ar annual average), and 19 μg/L(30 - ye ar average) f or surface w ater (using P RZM EXAMS), and 5.87 μg/L for groundwater (using SCI - GRO W ) . 3 

### Table 2. Comparison of Proposed Chickpea, Dry Peas, and Lentils Uses to Existing Turf **Uses. Use**  **S i** **te Application** 

**Me t**  **h o**  **d M**  **a ximum** 

**Single Application**  **R a**  **te M**  **a ximum** 

**An n**  **ual Application**  **R a**  **te M**  **a ximum** 

**Applications Per**  **Y e**  **a r**  1 **Minim um** 

**Reapplicati o**  **n Inte**  **r val**  lb ai/acre lb ai/acre day s P rop o se d Use C h ick p ea, Dry p eas, Le ntils Aerial, Gr o und, and

C h e mi g ati o n equ ip ment 0 . 12 0 . 24 2 10 E x isti n g Use Turf, Resi d e ntial, C o mmercial, or Indu strial Aer i al, Gr o und

S p ray er, H an d - h eld or Backpack S p ray er 0 . 34 1 . 08 3 14 Turf, golf course Aer i al, Gr o und

S p ray er, H an d - h eld or Backpack S p ray er 0 . 34 1 . 08 3 14 Gr o und Sp r ay e r , Hand - He l d or Backpa c k S p r ay er 0 . 31 1 . 33 6 ( 4 . 3 ) 14

3 Dr ink i n g Water Assess m e nt f o r T o leran ce Petiti o n f

o r New U s es of Trifl ox y stro b in in Triflo x y stro b in Flowab le F ungicide [ EP A R e g. N o . 26 4 - 9 89 ] . D3 7 89 1 9 .4 USEPA Office of Pestici d e Program s, E nviro nm e ntal Fa t e and Effects Di v i sio n . Stan d ar d ized S o il M ob ility

Classification Gu i d ance. A p ril 21 , 20 0 6. 

### Page **4** of **14 Environmental Fate a**  **n d Transport Characteri**  **z ation**  The environm ental fate and phy sioche m ical properties of trifloxy strobin and its m ajor degradation product CGA - 321113 are summ arized in **Table 3** and **Table 4** , respectivel y. **Table 4** also i n clud e s the a e robic soil m etabolism hal f - li f e f or the t o t a l toxic re s i d

ues. Che m ical structures for trifloxy strobin and CGA - 321113 are available in **Appendix 1**  . Parent: Trifloxystrobin Triflox ys trobin has a low solubil i ty (0.61 m g/ L @ pH 7) in water. The vapor pressure is 2.55 x 10 - 8 

### torr at 25 °C, and the calculated Henry ’s Law Constant is 2.25 x 10 - 8 

### atm - m3 

### mol - 1



### . These values sug g est th at trifl o xy strobin is non - volatile under field conditions from water an d m oist soil s urfaces. Volatilization is not a likely ro ut e of dissipation. Triflox ys trobin is non - persistent in soil. Laboratory studies indicate that biotransfor m ation is an i m portant route of trifloxystrobin transfo rm ation in aerobic soil. Triflox ys trobin degraded rapidl y in aerobic soils with half

- lives ranging between 0.41 and 0.91 d a ys . In aerobic soils the m ajor degradate is CGA - 321113. Photod egradation in soil results in the iso m erization and subsequent fo rm ation of CGA - 321113. The photo - i nduced iso m erization half - life ( t 1/2 

### ) was 2.1 day s on soils. Based upon the soil organic carbon coefficient, Koc 

### ( m edian Koc =2709 mL/ g o c 

### ), trifloxy strobin would f all i nto the s lightly m obile cl a s s 4



### . Laboratory

studies i ndicate that trifloxy strobin is also not persistent in water. Hydrol ys is of trifloxy strobin is dependent on pH; while triflox ys trobin is stable to hydroly sis under acidic conditions (pH 4), it readily hydrol yz es to CGA - 321113 in alkaline conditions ( t 1 / 2 

### = 55.2 day s at pH 7 and 0.83 day s at pH 9). In the aquatic environm ent, the photo - induced iso m erization halfli f e ( t 1/ 2 

### ) was 14.8 day s. In an aerobic aquatic sedi ment sy stem, the m ajor trans for m ation product was CGA - 321113. Triflox ys trobin de m onstrated a biphasic degradation pattern in field dissipation studies conducted in California, New York, and Georgia. For the first degradation phase, triflox ys trobin half - life values ranged f

r om 1.9 to 24 day s. In the second degradation phase, half - life values ranged from 6.5 day s to 4 m onths. Degradate of Concern: CGA - 321113 CGA - 321113 is the m ajor transformation product identified in trifloxy s trobin soil m etabolism studies. Fate studies indicate that C GA - 321113 is quite persi s tent in soil (D T 5 0 

### 250 to 350 days) and aquatic environm ents (DT 5 0 

### = 289 day s). It is stable to hydrol ys is and m etabolis m ; therefore, C GA - 321113 is expected to degrade at a slower rate than trifloxy strobin in both soil and water. The aqueous solubility for CGA - 321113 (30.9 m g/L ) is three orders of m a gnitude higher than the aqueous solubility for tri f loxy strobin. CGA - 321113 is a carbox yl ic acid, and therefore being anionic, is expected to be m ore mobile than parent trifloxystrobin. The5 USEPA Office of Pestici d e Program s, E nviro nm e ntal Fa t e and Effects Di v i sio n . Stan d ar d ized S o il M ob ility

Classification Gu i d ance. A p ril 21 , 20 0 6. 

### Page **5** of **14 Pa**  **r a**  **me ter**  **Value Source**  M o lecular mass ( molecular fo rm ula) 4 0 8 .3 7 g/mo l ( C 20 H 19 F 3 N 2 O 4 ) 2 013 EPA Pro b lem F o rm u l ati o n V apor pr essur e ( 2 5°C) 2 . 5 5 x 10 - 8 tor r a,b Aqu e ou s s o lubili ty (2 0  C) 0 . 6 1 mg/L @ pH7 MRID 4 45 0 28 0 1 He nry ’s La w Const ant (2 5 ° C) 2 . 25 x1 0 - 8 atm- m3 /mol 2 013 EPA Pro b lem F o rm u l ati o n Log o ctan o l - to - water p artiti o n c o efficie nt (l o g K O W ) ( 2 5 ° C) 4 . 5 MRID 4 45 0 28 0 1 H ydr ol y sis half

- life ( 25 ± 1  C) pH 4: stable pH 7: 5 5 . 2 day s pH 9: 0 .8 3 day s MRID 4 44 9 67 2 7 Aqu e ou s ph o tolysis h alf

- life ( 2 5± 1  C) 1 4. 8 d ay s @p H 5 MRID 4 44 9 67 2 7 S o il ph o t o lysis h alf

- life (2 5 ± 1  C) 2 . 1 d ays MRI D 4 44 9 67 2 9 Aero b ic s o il metabo lism h alf - life [ d iss ip ation h alf - life A ] (25 ± 1°C) 0 . 7 4 , 0 . 4 1 , an d 0 .9 1 day s mean = 0.69 d , std = 0.25 d MRID 4 44 9 67 3 2 MRID 4 44 9 67 3 0 MRID 4 44 9 67 3 1 An aer ob i c aquatic m etabo lism h alf - life ( 2 0 - 2 9  C) 0 . 72 day s MRID 4 44 9 67 3 3 Aero b i c aqu atic m e tabo lism h alf - life [ d iss ip ati o n h a l f

- life A ] ( 2 5  C) 0 . 6 0 d ay s ( sup p le me ntal) MRI D 4 44 9 67 3 4

Fre un d lich s o il - water p artiti o n c o efficie nts ( KF ); o r g an i c car

bo n - n o rma l i ze d F r e un d lich coefficients ( KFOC ) KF ( mL/g); 6 . 8, 7 . 7, 1 6 . 0 , 5 9 . 4 , 9 1 . 8 , 3 3 . 2 M ean = 3 5 . 82; Std = 3 3 . 8 KFOC ( mL/g OC ) 2 35 4 , 9 5 1, 3 06 4 , 3 9 2 7 , 98 7 1, 9 5 1 coefficient of determination ( r2 ) = ( K f v s . o r g anic matter = 0 .0 3 ) MRID 4 44 9 68 0 2 

### adsorption/desorption mobility classification of CGA - 321113 is m obile to moderatel y mobile 5



### . Because of its per s istence and m obility , CGA - 321113 has greater p o tential for leac h i n g than trifloxy strobin. In contrast to laboratory

d ata, CGA - 321113 was not detected above 0.02 percent of th e applied am ount in leachates from a field ly si m eter study . In field dissipation stu d ies conducted in Georgia, California, and New York, und e r bare ground and cropped conditions, CGA - 321113 concentrati o ns reac h ed o r were slightl y above th e Li m it of Quantitation of 10 μg/L in 1 2 - 18 and 30 - 36 inch soil segm ents. **Table 3.**  **Chemical Properties**  **and Environ**  **m ental**  **Fate Parame**  **t ers**  **For Trif**  **l oxystrobin.** 

a USEPA Fact Sheet repo rts 3.4 x 1 0 - 6 torr (@25 °C) b PMRA Reg2004 - 03 and Tri f lo x y strobin (213) report 3.4 x 10 - 6 P a @ (@25 °C)

### Page **6** of **14**

**Table 4.**  **Chemical Properties**  **and Environme**  **n tal**  **Fate Parame**  **t ers**  **For CGA**  **- 321113**  **and Residues**  **of Concern**  **( trifloxystrobin**  **+ degradate**  **CGA -**  **321113). Pa**  **r a**  **me ter**  **Values 1**  **Source C**  **G A**  **- 3**  **211 1**  **3** Molecular Form

ula C 19 H 17 F 3 N 2 O 4 MRID 4 44 9 68 0 1 M o lec u lar We i ght 3 9 4 .35 MRID 4 44 9 68 0 1 S o lu b ility @ 20 ◦ C 3 0 .9 mg/L MRI D 4 44 9 68 1 6 Vapo r P res s ure 7 . 5 x 10 - 08 mm H g @ 2 0 ◦ C MRID 4 44 9 68 0 1 He nry ’s C o ns tant 1 . 26 x 1 0 - 09 at m m3 mo l - 1 H y dr o ly sis Half

- life Stab le MRID 4 44 9 67 2 7 Aqu atic P ho to l ysis Half

- life Stab le MRID 4 44 9 67 2 7 Ph o t o l ysis on s o il Half

- life Stab le MRID 4 44 9 67 2 7 Aero b ic Aqu atic Metabo lism Halflife Stable MRID 4 44 9 67 3 4 An aer ob i c A quatic Metab o lism Half - life Stab le MRI D 4 44 9 67 3 3 Or g an i c Car

b on Partiti o n Coefficient (Koc) ( mL/g) 1 2 7 , 23 5 , 1 3 0, 4 8 , an d 80 mean 1 2 4.0 mL/g oc me d i an 127 mL/ g oc C o ef. Determin ati o n ( r2 ) = 0. 8 9 f o r K f vs. om MRID 4 44 9 68 0 1

S o il Partiti o n C o efficie nt ( K f ) ( mL/g) K f (t e xture class) 4 . 0 L o am (5 . 4 % o m

) 1 . 9 S an d 3 . 2 Clay loam 0 . 28 S an d y l o am (1% o m ) 0 . 65 S an d y l o am mean = 2.0 mL/g [1 / n = 0 .8 1 to 0 . 85] MRID 4 44 9 68 0 1

**Persistence for Residues**  **of Concern**  **(pa r**  **ent tri**  **f loxyst**  **r o**  **bin + CGA**  **- 321113**  **) (DP**  **D309489 see T**  **a ble 9)**  [Resi dues of Conc ern ] : Aero b ic S o il Metabo lism Half - life 2 5 4 . 8 day s 2 7 1 . 3 day s 1 9 9 . 7 day s 2 8 2 .7 5 day s ( 9 0 th perc e nt u

pp e r b o un d on m ean) Me d i an = 25 4 . 8 d ays MRID 4 44 9 67 3 2 MRID 4 44 9 67 3 0 MRID 4 44 9 67 3 1

### Page **7** of **14**

**Models and Model Scenarios Used**  Detailed descriptions, docum entation, and links f or running the exposure models used in this assess m ent m ay

be found at http://www.epa.gov/oppefed1/models/water/index.htm . Groundwater ED W C s for total toxic residues of triflox ys trobin resu l ting f rom the turf use were derived with PRZM - GW (Pesticide Root Z one Model for Groundwater, version 1.0, August 31, 2012), using the G W - GUI (Graphical User Interface, version 1.0, August 31, 2012). E DWCs for the Screening Concentration in Groundwater m o del were calculated in a 2010 DWA and are reported in this assess m e nt (SCI - GROW v2.3, compiled 08/08/03) . 6 

### Surface water E D WCs were derived using PRZM/EXAMS as described in the 2010 DWA. **Model Input Parameters**  The m odel input param eters for PRZM - GW are summ arized in **Table 4** . Model input values were prepared following EFED input guidanc e 7 , 8



### . For each PRZM - GW scenario, EDWCs were calcul ated for each ye ar in a 30 - ye ar s i mulation where triflox ys trobin w as applied at the m ax i m u m label rate for 30 consecutive y ears. The initial appli c ation d ate w as assum ed to be the date of e m ergence for the P RZM - GW scenario used. **Figure 1** is th e PRZM - GW U s er Interface that shows th e m odel inputs for the trifloxy s tro b in total to x i c residues an d illu s trates how m ultiple applicati o ns were included in the modeling. **Table 4.**  **Input Values**  **Used to**  **Model Total**  **Toxic Residue**  **EDWCs in**  **Groundwater for**  **the Trifloxystrobin**  **Turf Use.**  **Model I n**  **put Pa**  **r a**  **me ter**  **PR Z**  **M -**  **G W**  **I nput Value**  **a n**  **d Unit**  **Source /**  **Com m**  **ents**

Max i m u m A p plicati o n Rate 0 . 3 4 7 kg a. i . / h a f o r th e f i rst f o ur app li catio ns, 0 . 1 0 1 kg a. i . / h a f o r th e fifth ap plication f

o r an annu al applicati o n rat e o f 1 . 4 8 9 kg a .i./h a Labe l ; Co rre sp o n ds to f our applicati o ns of 0 .3 1 lb a.i./acre and a fifth ap p licati o n o f 0.9 lb a.i./acre for an annu al app lication rate o f 1 . 3 3 lb a.i./acre. M ax i m u m Num b er of A pp lic ati ons 5 The l abel indicates 6 ap plications may be made, but n o t at th e ma xi m u m si n g le app lication rate.

6 Dr ink i n g Water Assess m e nt f o r T o leran ce Petiti o n f

o r New U s es of Trifl ox y stro b in in Triflo x y stro b in Flowab le F ungicide [ EP A R e g. N o . 26 4 - 9 89 ] . D3 7 89 1 9 . 7 Parameters are selected as per Gu i d an ce for Selecti n g I n p ut Para meters in Mo d eli n g t h e Env ir onm e ntal Fate and Transp o rt of Pestici d es; Vers i o n 2.1, Octo b e r 2 2 , 2 00 9 . 8 Baris, R.; Barrett, M.; B oh aty , R.; Ec h e v e rr i a, M.; Kenn edy, I.; Malis, G.; Wo l f , J.; Y oun g, D . PRZ

M - GW Input Pa ra me ter G u i d

a n ce ; Health Canad a , U. S . E nv ir o nm ental Protecti o n Ag en c y , Oct o b e r 1 2 , 20 1 2 .

### Page **8** of **14**

**Model I n**  **put Pa**  **r a**  **me ter**  **PR Z**  **M -**  **G W**  **I nput Value**  **a n**  **d Unit Source**  **/ Com**  **m ents** 

Meth od o f Ap p licati o n C AM 1, Bar e Gr o und Lab el

Date of I n itial Ap p licati o n 1 2 0 d ays p o st - e m er g e n ce E mergence dates are specifi e d in each PRZ M - GW sc e n ar i o . Mini m u m Interval be tween Ap p licati on s 14 day s Label S o il Partiti o n C o efficie nt K oc ( C G A - 3 21 1 13) 1 2 4 mL/g oc ( mean) MRID 4 44 9 68 0 1 Hydr o lysis Half

- Life ( C G A - 3 21 1 13) Stab le MRI D 4 44 9 67 2 7

Aero b ic S o il Metabo lism Half - Life ( p are nt t riflo x y stro b i n + CGA 3 21 1 13) 2 8 2 .7 5 day s ( 9 0 th perc e nt u

pp e r b o un d on m ean) MRID 4 44 9 67 3 2 MRID 4 44 9 67 3 0 MRID 4 44 9 67 3 1

### Page **9** of **14**

**Figure 1.**  **Trifloxystrobin -**  **Example of**  **P R** **Z M**  **- GW**  **User Interface**  **and Inputs**  **fo r**  **Foliar Applications**  **to Turf.** 

### Page **10** of **14**

**Modeling Results Table 5**  rep orts th e EDWCs calculated for each PRZM - GW ( i.e. , groundwater) scenario for applications at 120 day s post - e m ergence. ED W C s calculated for 0 - and 60 - day s post - e m ergence were also calculated and yi elded E D WCs approxi m ately 10 - 30 μg/L in their respective scenarios. P eak ED W C s for all sce n arios and application periods m odeled ranged from 55 to 427 μg/L, and the post - breakthrough average E D WCs ranged from 48 to 365 μ g/ L. The W i sconsin Corn scenario resulted in the m axi m um EDWCs. The PRZM - GW t i m e series graph f or the W isconsin Corn s cenario ED WC s is presented in **F i**  **g ure 2**  . EDWCs for the turf use were calculated using S C I - GROW in th e 2010 DWA, which resulted in acute and chronic EDWC of 5.87 μg/L . 9 

### EFED recommends using the m aximum peak and post - breakthrough average concentrations from the 30 - ye ar PRZM - GW s i m ulation for the W is c onsin corn scenario for hum an health risk assess m ent ( i.e., 427 and 365 μ g/ L). and are not expected to be gre ater th an **Table 5. Tier I PR Z**  **M -**  **G W Total Toxic Residue**  **Estimated Drinking Water Concentrations (EDWCs) for 30 Years for the Trifloxystrobin Turf Use.**  **Scenario Peak**  **(μg/L) Po**  **s t**  **** **Breakthrough Average**  **(μg /**  **L) Average** 

**Breakthrough Time**  **(days) Throu**  **g hp**  **u t**  **s** ***** **First Appli**  **c ation**  **120 D**  **a y**  **s Po**  **s t**  **- E**  **m erg**  **e nce**  FL Citrus 241 187 1250 8.8 DMV Corn 258 202 1239 8.8 FL Potato 55 49 2862 3.8 G A Peanuts 113 96 3023 3.6 NC Cotton 250 216 2056 5.3 WI Corn 427 365 2848 3.8 *Throughputs are the estimated pore volumes/retardat i on f a ctors t hat occur in the simulation.

9 Dr ink i n g Water Assess m e nt f o r T o leran ce Petiti o n f

o r New U s es of Trifl ox y stro b in in Triflo x y stro b in Flowab le F ungicide [ EP A R e g. N o . 26 4 - 9 89 ] . D3 7 89 1 9 .

### Page **11** of **14**

**Figure 2. PR Z**  **M -**  **GW Wisconsin Corn Scena r**  **io Time Series Graph for 30 Years Trifloxystrobin Application to Turf (ppb is equivalent to**  **μg/L total**  **toxic residues).** 



### Tier I PR**Z M**  **- GW M**  **o deling Assumptions**  In esti m ating pesticide c oncentr atio n s in water resources, O P P uses a tiered screening approach involving a co m

bination of m odels and m onitoring d ata. The intent of the screening app roach is to esti m ate pesticide co n centr ation in water f rom sites that are highly

vulnerable to runoff or leac h ing so that the p rogram can be confident th at any pestici d e that p asses the screeni n g tiers poses a low possibility

of harm ing hum an health , wildli f e, or the enviro nm ent. Failing a ti e r, however, does not nece s sarily m ean the che m ical is li k ely to cause he a lth or environm ental proble m s, but rather that there is a need to m ove to a higher tier and conduct a m ore refined assess m ent. This tiered m odeling s ys tem is d e signed to provide a tho r ough anal ys is of each pesticide, while at the s am e ti m e f ocus OPP ' s efforts on th o se pesticides that pose the greatest potential risk. In this assess m ent, PRZM - GW is used as a T i er - 1 screen. In other words, the m odeling conducted f

or this assess m ent preserves defa u lt conservative assum

ptions in the PRZM - GW model. As such, Tier 1 PRZM - G W modeling is expected to res u lt in conservative groundwater EDWCs that would rarely, if ever, occur in the environm ent. Depending on the Tier I results, Tier II (or “re f ined”) EDWCs m ay

be m o deled to take into account u s age data, well setback re quire m ents, a dditio n al fate inputs, and an exposure duration specific to the exposure duration of concern for hum ans. A more representative scenario m ay also be developed as part of Tier II E D WC m od e ling. This assess m ent has not calculated Tier II EDWCs using PRZM - GW, and thus does not consi d er triflox ys trobin usage data, well setbacks, additional fate inputs, specific exposure durations, or new scenario develop m ent. For m ore infor m ation on potential Tier II r e fine m ents in PRZM - GW modeling, see http://www.epa.gov/oppefed1/m ode l s/wate r /przm_gw/wqtt_prz m

_gw_ guidance.htm ). The default PRZM - GW assum ptions used in calculating Tier I groundwater ED W C s for trifloxy strobin total toxic residues include the following:

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 Triflox ys trobin is used at the m aximum labeled rate for 30 consecutive ye ars.  There are no well setbacks.  Re m oval of the pe s ti c ide via r unoff or erosion is negligible.  The saturated zone is a shallow (<100 feet), unconfined aquifer with a water table depth that corresponds to its r e spective scenario location.  The well screen exten d s from the aquifer s u rface to 1 m eter below the aquifer surface.  The pestici d e undergoes aerobic soil m etabolism in the top 10 cm of soil; the aero b ic s oil m etabolism rate d eclines linearly to 1 m eter bel o w the soil s urface, below which only abiotic degradation processes ( i.e. , hydroly sis) occur. These assumptions are designed to introduce a high level of prote c tion i nto the m odeling res u lts. **Monitoring Data** Surface water and groun dwater data from one s t ate and three nationwide pesticide m onitoring program s were reviewed to provide additional context concerning the potential presence of trifloxy strobin in drinking water resources. These water m onitoring program s do not target sam ple coll e ction to pe ak use loc ations o r application ti m es for p articular pesticides, nor do they targ e t sam

ple collection to high precipitation events ( i . e. , high - runoff events). Additionally , the sam pling frequency

in these m onitoring program s was not designed to capture peak concentrations. Therefore, the m onitoring data reported by these program s m ay

not represent the highest concentrations in drink i ng water source w ater, and are con s idered qualitative info rm ation for the purposes of this drinking water assess m e nt. USGS -EPA Pilot Reservoir Monitoring Program **-** Triflox ys trobin and CGA - 321113 data were not anal y zed as part of this program . USGS National W

ater- Q uality Assessment (NAWQA) Program Data **-** Trifloxy strobin data were available fr o m USGS NAWQA surface water an d sedi m ent data. Surface water detections were from Cobb and Coweta counties in Georgia in 2010 (2 sam ples with d e tections less than 4.7 ng/L), Cam e ron Count y i n Texas in 2013 (1 sam p le with a detection less than 2 ng/L), and San Joaquin and Sacram ento Counties in C alifornia in 2012 (11 samples with d e tections less than 4.7 ng/L). In G eorgia’s Cobb, Coweta, and Sumt er counties, sedi m ent s amples taken from 2010 to 2011 had triflox ys trobin detections less than 1.4 ug/kg. Trifloxy strobin was not detected in groundwate r. NAWQA has not anal yz ed sur f ace water or groundwater sam ples for CGA 321113. NAWQA program data are available at http://infotrek.er.usgs.gov/nawqa_queries/index.js p . Californ ia S

urface W a te r Monito ri ng Program Data **-** The Cali f ornia S ur f

ace W ater Monit o ri n g Program represents pesticide occ urrence data for surface waters in th e Sacram ento Valley , San Joaquin Valley , and other locations in the state. The California surface water and groundwater monitoring data i n cluded a total of 43 surface water detectio n s f o r triflox y strobin, all b elow the level of quantitation ( L OQs of 0.02 to 0.05 μ g/ L) from Colusa, Sutter, Yolo and Yuba counties from 2006 to 2008. The California S urface W ater Mo nit o ri n g Program has not anal y zed surface water or g r o undwater for CGA - 321113. Califor ni a Surface Water Monitoring Pro g ram data are available at http://www.cdpr.ca.gov/docs/e m on/surfwtr/surfdata.htm .

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Pesti c ide D ata Progra m ( P DP) Data - The PDP drinking water m onitoring project provides non targeted pe st icide o ccurrence data in raw water, finished water (treate d /tap), and groundwater in the United S t ates. The PDP has not anal yz ed s urface water or groundwater for detections of trifloxy strobin or CGA - 321113. PDP data are available at http://www.am s.usda.g o v/AMSv1.0/pdp .

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**Appendix 1. Chemical Structures for Trifloxys**  **t robin and CGA**  **- 321113**  Triflox ys trobin

CGA - 321113