1 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION **UNITED STA TES ENVIRONMENTA**  **L PROTECTION A GENCY** 

WA SHINGTON, D.C. 20460
July 9 , 2013 **PC Code: 036602**  **MEMORANDUM DP Barcode:**  **409108 & 409109 SUBJECT**  **: Mandipropamid**  **:** Drinking Water Exposure Assessment for P roposed Section 3

New Use s on: Basil, Gins eng and Succulent Bean s ; and Expand ed U ses on Bulb Vegetables, C ucurbits, Grapes, and F ruiting V egetabl es including T omato es . **FROM :**  Richard Shamblen, Biologist

ERB2 /EFED (7507P) **THROUGH :**  Greg Orrick , Environmental Scientist

Brian Anderson , Branch Chief ERB2 /EFED (7507P) **TO:** Dennis McNeill y , Risk Assessor

Christina S wartz , Branch Chief RAB 2 /HED (7509P) Tony Kish , Risk Manager, RM Team 20 Rosemary

Kearns, Risk Manager Review er Laura Nollen, Biologist, RIMU ERB/RD FB/RD (7505P) The Environmental Fate and Effects Division (EFED ) co nducted a Tier 1 drinking w ater exposure a ssessment for the fungicide mandipropamid . The registrant seeks a Section 3 new u se registration for b asil, g inseng and succulent b ean s ; and expansion of currently regist ered use groups including bulb vegetables, cucurbits, grapes, and fruiting vegetables including tomatoes. Previous exposure assessments evaluated maximum single application rates of 0.13 lbs a.i./A, four times per season. The registrant seeks to increase the total annual application rate to 2.08 lbs a.i./ A for tomato and basil by allowing for up to four crop production seasons per year . This proposed multi
- season total annual application r ate exceeds those assessed in previous drinking water exposure assessments. Tier 1 exposure m odel re sults are summarized in **Table 1**
. PRZM
- GW was used to estimate mandipropamid exposure in ground water. Maximum estimated drinking water concentrations ( EDWC ) in ground water are **87 and 79 μ**  **g /L**  for acute and chronic exposures, respectivel y. These values are as much as 480 times higher than SCI
- GROW model results. Maximum acute and chronic EDWCs in surface waters are **7 9**  **and 9 .**  **0 μg/L**  , respectivel y .2

**Table 1. Tier 1**  **Estimated Drinking Water**  **Concentrations (EDWC)**  **for Maximum**  **Mandipropamid Use**  **Pattern s**  **. Drinking Water**  **Source (Model**  **, Version )**  **PCA (%)**  **Crop Use**  **Pattern (Maximum Annual Rate)**  **Acute (μg/L)**  **Chronic**

**(μg/L)** Surface W ater (FIRST , 1.1.1 ) 91 Tomato & Basil (2.08 lbs a.i./A) 7 9 9.0 Ground W ater (PRZM
- GW , 1.01 ) N/A Tomato & Basil ( 2.08 lbs a.i./A) **87 79**  Ground W ater (SCI
- GROW , 2.3 ) N/A Tomato & Basil (2.08 lbs a.i./A) 0.18 **Abbreviations:** A= acre; a.i. = active ingredient; ha = hectare; kg = kilograms ; μg = micrograms; lbs = pounds (US); N/A = not applicable Two p revious Tier 1 drinking water assessments of mandipropamid produced nearl y identical exposure estimates (USEPA, 2007 ; and , 2011). Results of multiple FIRST (v.1.1.0) model scenarios indicat ed EDWCs in surface water s rang ing from 7 to 36 μg/L for chronic and acute exposures. Ground water exposure estimates in both assessments were about 2.4 μg/L when calculated b y SCI
- GROW (v. 2.3)
. PRZM
- GW (v. 1.01) was not used. Differences between the previous two and current drinking water exposure assessment s reveal that ground water exposure concentrations decreased b y more than a factor of 13, whereas acute surface water exposure concentrations nearly doubled
. These differences are likel y attrib uted to a variety of recent changes incorporated into the drinking water assessment. In particular, the following factors adopted for this risk assessment may account for the differences : 1) F our seasons per ye ar are assumed for tomato and basil, whereas onl y one season per ye ar was a ssumed for previously assessed use sites 1 ; 2) Changes to EFED model input parameter guid ance , version 2.1 (USEPA, 2009); 3) Higher KOC model input adjustments : mean ( 575 L/kg) used instead of lowest (405 L/kg ); 4) Lower a erobic soil metabolism model input values : 13 3 d instead of 81.3 d ; 5) Total Residue modeling approach (USEPA, 2013) was used to calculate a erobic aquatic metabolism input of 108 day s instead of separately modeling a range of half
- lives of 19 to 1323 day s for parent and degradates ; 6) Percent Cropped Area ( PCA) factor of 0.91 used instead of 0.87 (USEPA, 2012 a ) ; and, 7) Revisions to the PestDF kinetics software used to calculate half
- lives. The Total Residue (TR) modeling approach (USEPA, 2013) was used to estimate aerobic aquatic half

- lives, and estimate drinking water concentrations in surface waters. Previous drinking water assessments calculated separate half
- lives for the parent compound and two degradates of concern , for which exposure was estimated with separate model runs . Simple addition of the exposure estimates for mandipropamid and it’s degradates of concern was used to generate estimated drinking water concentrations. Previous authors acknowledge this approach is conservative because the exposure estimates may not be temporally coincident. The TR method , however, tallies the parent compound and it’s degradates of concern prior to calculating a Total Residue half

- life using PestDF
.

1 e - Mail communications from Tammy T yler of Syngenta to Johannes Corley of IR
- 4, February 31, 2013.3

**1. Use Characterization**  Mandipropamid is a fungicide used to control downy mildew, phy

tophthora blight and root rot, blue mold, and late blight in vegetable production
. The fungicide can be applied as a post - emergent, foliar spray using ground, aerial, or chemigation 2 equipment. The proposed label specifies a maximum sea sonal application rate of 0.52 lbs. active ingredient per acre (a.i./A) , and is divided into four separate applications of 0.13 lbs. a.i./A with a 7
- day minimum interval
. The proposed expanded 3 and new use patterns are summarized in **Table 2** 
. For six (6 ) of the eight (8 ) proposed new and expanded crop uses, the maximum application rate per event and season remain consistent with previously assessed application rates (USEPA, 2007; and, USEPA, 2011 ). The registrant proposes , however, to expand the product a pplication to to mato and basil with up to four (4) crop production seasons per calendar ye ar. Thus, the registrant proposes a total of sixteen (16) application events for a cumulative annual application rate of 2.08 lbs a.i./A4

. **Table 2**  **. Proposed Use**  **Patterns for**  **Mandipropamid Registration**  **Status Use Site**  **Maximum Application**  **Rate 1)**  **(lbs a.i./A) Maximum** 

**Number of Application**  **s per**  **Season Minim** **um**

**Application Interval**  **2) (days)**  **Maximum**

**Annual Application**  **Rate 3)**  **(lbs a.i./A) Maximum** 

**Number of Application**  **s per Year**  **3)** Proposed New Use Bean ( succulent) ; Ginseng 0.13 4 7 0.52 4 Basil (fresh and dried) 0.13 4 7 2.08 16
Proposed Expanded Use Bulb Vegetables; Cucurbits; Fruiting Vegetable (except tomato) ; Grapes 0.13 4 7 0.52 4

Tomato 0.13 4 7 2.08 16 **Abbreviations:** A= acre; a.i. = active ingredient; lbs = pounds **Note(s):** 1) Single application event. 2) Minimum number of days between application events. 3) Year is defined as a calendar year; January 1 through December 31. The proposed label covers thirteen (13) use sites . There are no requested use changes for five (5) crops or crop groups : brassica; hops ; leafy vegetables; potatoes and other tuberous and corm vegetables ; and tobacco. The registrant seeks n ew u se registration s for mandipropamid on the three (3) following crops and crop groups , including hy brids and varieties thereof : 1. Basil : (fresh and dried);

2 Pesticide application through irrigation systems. 3 Additional crops, varieties or hybrids within a currently registered crop group. 4 e - Mail communications from Tammy T yler of Syngenta to Johannes Corley of IR
- 4, February 31, 2013.4

2. Bean (succulent subgroup) : Cicer arietinum (chickpea, garbanzo bean); Lupinus spp. (inkling sweet lupine, white sweet lupine, white lupine, and grain lupine). Phaseoulus spp. (including kidney

bean, lima bean, mung bean, navy bean, pinto bean, snap bean, and waxbean); Vicia faba (broad bean, fava bean); Vigna spp. (including asparagus bean, black
- eyed pea and cowpea); in succulent form only ; and, 3. Ginseng
. The registrant seeks to expand the current registration of mandipropamid on the following five (5) crop s and crop groups , including hy brids and varieties thereof : 1. Bulb vegetables including cultivars, varieties, and/or hy brids of these and others in  the onion (dry) subgroup 3
- 07A: daylily ; fri tillaria; garlic; garlic (great
- headed); garlic (serpent); lily

onion; onion (Chinese); onion (pearl); onion (potato); shallot; and ,  the green onion (subgroup 3
- 07 B): chive; chive (Chinese); elegans hosta; fritillaria; kurrat; lady’s leek; leek; leek (wild); onion Beltsville bunching); onion (fresh); onion (green); onion (macrostem); onion (tree tops); onion (Welsh); and shallot; 2. Cucurbit vegetables: Chayote (fruit); Chinese wax gourd (Chinese preserving melon); citron melon; cucumber; gherkin; gourds, edible (includes hyotan, cucuzza, hechima, Chinese okra); Momordica spp. (includes balsam apple, balsam pear, bitter melon, Chinese cucumber); muskmelon (includes tru e cantaloupe, cantaloupe, casaba, crenshaw melon, golden pershaw, melon, honeydew melon, honey balls, mango melon, Persian melon, pineapple melon, Santa Claus melon, and snake melon); pumpkin; squash, summer (includes crookneck squash, scallop squash, stra intneck squash, vegetable marrow, zucchini) ; squash, winter (includes butternut squash, calabaza, hubbard squash, acorn squash, spaghetti squash); watermelon. 3. Grapes including cultivars, varieties, and/or hybrids of subgroup 13
- 07F (except fuzzy kiwifrui t): Amur river grape, gooseberry , grape, kiwifruit (hardy); may pop; schisandra berry ; 4. Fruiting Vegetable Group (except tomatoes) including cultivars, varieties, and/or hy brids of these and others in this group: African eggplant, bell pepper; cocona; eggpl ant, garden huckleberry ; goji berry ; groundcherry ; martynia; naranjilla; okra; pea eggplant; pepino; nonbell pepper; roselle; scarlet eggplant; sunberry ; and, 5. Tomato (includes tomato, bush; tomato, currant; tomatillo; tomato tree). **2. Environmental Fate**  **Characterization** When Mandipropamid is released into the environment, it is expected to be somewhat persistent and ha s low to moderate mobility . The primary degradation route is ty

picall y expected to be metabolism with half
- lives ranging from approximate ly 40 to 90 day s in aerobic conditions in water and soil laboratory studies. Half

- lives from field studies were similar and ranged from 75 to 100 day s. The fungicide degrades relatively quickl y via photol ys is with a half
- life of approximately

2 day s . H ow ever, photol ys is is only relevant under some environmental conditions and field studies suggest that it is not a major degradation route under conditions of those studies. Mandipropamid degrades very slowl y via hydroly sis, and volatilization from soil and water is expected to be minimal. Bioconcentration is also not a primary concern.5

For general characterization and pesticide exposure modeling purposes, **Table 3**  contains selected phys ical and chemical properties and environmental fate data, and correspo nding sources of data for mandipropami d. There are several data uncertainties from pesticide metabolism and mobility studies used in this drinking water assessment, including : 1. There is no statistically significant degradation of mandipropamid by hydroly sis at the p = 0.05 confidence level. Based on the level of uncertainty in the hydroly sis study due to background variability , the degradation might be as fast as 1900 d ay at pH 7 and not be detected in the current 30 d ay study
. In order to bound th e effects of hydrol ytic degradation in the PRZM
- GW simulations, estimates were made using the 1900 day hydrolysis half

- life rather than assuming no hydrol ytic degradation and the EDWC decreased from 90 to 7 9 d ay (1 2 %). 2. Of the three aerobic aquatic metabol ism studies, only one study ( MRID 46800031) is currentl y cl assified a s “supplemental and upgradeable. ” A dditional information is needed related to identification of all major transformation products for both sy stems. The remaining two studies are classified “unacceptable. ” 3. There are two batch equilibrium studies that are classified as “ supplemental and upgradeable. ” One study

(MRID 46800038) include s four foreign soils , for which taxonomic classifications are needed to clarify if they represent do mestic agricultural use areas where the pesticide is anticipated to be applied. For this assessment, it is assumed th at three U.S. soils from one study (MRID 46800040) are representative of agricultural use areas. Although the USEPA guideline requires five soil ty pes (USEPA, 2008 b ) , data from the three domestic soil s were used for modeling purposes , pursuant to model input parameter guidelines, in the absence of additional acceptable data
. 4. There are f

ive aerobic soil metabolism studi es representing seven soils, ye t only one study (MRID 46800020) with one soil ty pe is currently

acceptable. This is because the acceptable soil is domestic and the other six are foreign soils without taxonomic classifications with which to assess their rep resentativeness of agricultural areas where the pesticide will be applied. Although the U SEPA guideline requires four soil ty pes for determination of transformation rates (USEPA, 2008 c ), the one soil ty pe was used for modeling purposes , pursuant to model input parameter guidelines, in the absence of additional acceptable data. Reported h alf

- life values for aerobic soil and aquatic metabolism studies were calculated using the PestDF (version 2.14.1) software from referenced study data ( PestDF model results and metabolism calculations are attached in **Appendix B** ).6

**Table 3**  **. Chemical Properties and**  **Environmental Fate Parameters of Mandipropamid** 

**Parameter (units)**  **Value Reference**  **(MRID) Selected Physical/Chemical Parameters**  Molecular Mass (Empirical Formula) 411.9 g/mol (C 23 H 22 ClNO 4 ) 46800004 Vapor pressure (25 °C) 1 ) (mmHg) < 7.1 x10 - 9 46800006 Aqueous solubility (25  C) (mg/L) 4.2 46800006 Henry’s Law Constant : calculated (25 °C) ( atm - m3 /mol ) <9.1 x 1 0 - 12 46800006 Log octanol
-to -water partition coefficient (25  C) ( log KOW) 3.2 46800006 Dissociation constants (pKa, pKb) No pKa was found in the range of 1.0 to 12.0 by spectrophotometric titration. 46800006 **Persistence** Hydrolysis half
- life (25  C) (days) (pH 4, 7 and 9) no significa nt degradation (pH 5) 1900 (pH 7) 1000 (pH 9) 4 680000 7 Aqueous photolysis half
- life (25  C) (days) 1.9 46800009 Aerobic soil metabolism half
- life (25° C) (days) (Soil T exture ) 44 (Sandy loam) 46800020 Aerobic aquatic metabolism half
- life (25°C) (days) ( Aquatic s ample system : Sediment) 79 (Swiss Lake : Loamy Sand) 94 ( Calwich Abbey : Silt Loam) 4680003 1 **Mobility** Freundlich organic carbon
- normalized coefficient (KFOC ) 2 ) (mL/g oc ) (Soil T exture ) 694 (Sandy loam) 46900040 406 ( L oam

y Sand) 625 ( L oam

y Sand) **Field Dissipation** Terrestrial f

ield dissipation half
- life 3) (days) (S oil T exture) 75 (Sandy loam) 46800045 100 ( L oam

y sand) 46800046 82 ( L oamy sand) 46800047 **Fish Bioconcentration**7 **Parameter (units)**  **Value Reference**  **(MRID)** Fish bioconcentration factors (steady
- state, total residues) (L/kg) Depuration Rate: Edible: 8.8
- 10 Inedible: 160
- 190 Whole body: 35
- 48 x Depuration: >82% in 25 hours 46800109 **Abbreviations:** atm

= atmosphere; °C = degree Celsius; g= gram ; Hg = mercury; L = liter; log = logarithm , base 10 ; m 3 = cubic meter; mg = milligram; mL = milliliter; mm = millimeter; mol = mole; NA = Not applicable ; MRID = master record identification **Note(s):** 1) Converted to torr (mmHg) from Pascal units (Pa). 2) The coefficient of variation (CV) for KFO C (0.3 ) is less than the CV of Kd ( 0.5 ), thus s orption was correlated with organic carbon content. KFOC wa s calculated with the following equation: (KF/ % organic matter)*100 (USEPA, 2008 b ). Calculations are provided in the Adsorption/ Desorption spreadsheet attached in Appendix B
. 3) Field dissipation data are not used for modeling purposes in the Tier 1 drinking water assessment. Thus, half
- lives were not re
- calculated. **3 .**  **Drinking Water Exposure Model** **ing 3.1**  **Model Parameterization 3.1.1**  **FIRST (Version 1.1.1)** EFED used the FQPA 5 In dex Reservoir Screening Tool (FIRST) Version 1.1.1 (USEPA, 2008 a ) to calculate Tier 1 estimate d drinking water concentrations (EDWC) for surface water s ys tem s . The model is used to estimate both acute and chronic potential concentration s in untreated drinking water (USEPA, 2001 a ). Model input parameters (USEPA, 2001a) , values selected, brief justification statement s for values selected (USEPA, 2009), and data sources are summarized below in **Table 4 .**  T otal Residue (TR) kinetics calculations were used to estimate the aerobic aquatic metabolism half

- life model input value (US EPA, 2013). TR kinetics calculations are presented in Appendix B. Total residue s include th e mandipropamid parent compound and its major degradates of concern , SYN500003 and SYN 504851. Other model inputs did not require TR calculations because the degradates of concern were not present in the supporting studies at concentrations greater than 10% of the applied
.

5 FQPA pertains to the Food Quality Protection Act of 1996.8

**Table 4. FIRST (v1.1.1)**  **Input Parameter**  **s Paramete**  **r Value**  **Justification Reference**  **(MRID)** Application Rate (lbs a.i./ A) 0.13 Maximum application rate Proposed label Application Events (per year) 1 6 Maximum num ber of applications per year Proposed label Meeting Minutes Minimum Application Interval (days) 7 Minimum application interval Proposed label Application Method Aerial Application equipment of maximum exposure Proposed label Incorporation D epth (cm) 0 Product is foliar applied via ground or aerial spray Proposed label Wetted
- in No Not applicable US EPA, 200 9 Solubility (25  C) (mg/L) 4.2 M aximum value at 20
- 25  C 46800006 Hydrolysis Half
- life (days) 190 0 Represents the study value at pH 7. 4680007; 46800008 Aquatic Photolysis Half
- life (days) 1.9 Represents the maximum study value
. 46800009 Aerobic Aquatic Metabolism Half
- life (days) 108 Total Residue approach was used to calculate half

- lives. Represents the upper 90 th percentile confidence bound on the mean of two total residue half

- lives
. 4680003 1 Organic Carbon Partition Coefficient (KOC ) (mL/kg OC ) 57 5 Represents the mean of three values
. 46800040 Aerobic Soil Metabolism Half
- lif e (days) 133 Represents 3x the single acceptable value
. 4680002 0 P ercent Cropped Area (PCA) Adj ustment Factor ( decimal ) 0. 91 N ational
- level PCA for all agricultural land US EPA, 2012 a **Abbreviations:** A= acre; a.i. = active ingredient; cm = centimeter; kg = kilogram; L = liter; lbs. = pounds; mg = milligram; mL = milliliter ; MRID = master record identification **3.1.2 SCI**  **- GROW (Version**  **2.3)** The Screening Concentration in Ground Water ( SCI
- GROW version 2.3 ) model was used to estimate drinking water pesticide concentrations in ground water. Results of the Tier 1 model9

determine if mandipropamid potentially po s e s sufficient risk to warrant higher level assessment (USEPA, 2001 b ). **Table 5** summarizes the SCI
- GROW input parameters (USEPA, 2001 b ), justification for values selected (USEPA, 2009), and appropriate references and data sources (US EPA, 2001 b ; and, USEPA, 2009). **Table 5 . SCI**  **- GROW**  **(Version 2.3) Input**  **Parameters Parameter**  **Value Justification**  **Reference (MRID)**  Application Rate (lbs a.i./ A) 0.13 Maximum application rate Proposed label Application Events (per year) 16 Maximum num ber of applications per year Proposed label Meeting Minutes Organic Carbon Partition Coefficient (KOC ) (mL/kg OC ) 625 Median of three KOC value s ; less than three
- fold variation 46800040 Aerobic Soil Metabolism Half
- life (days) 4 4 Single acceptable aerobic soil metabolism value 46800020 **Abbreviations:** A= acre; a.i. = active ingredient; cm = centimeters; kg = kilogram; L = liter; mg = milligrams ; mL = milliliter ; MRID = master record identification **3.1.3 PRZM**  **- GW**  **(Version 1.01)**  As part of a one
- ye ar evaluation period, EFED scientists are using the Pesticide Root Zone Model for Ground Water (PRZM
- GW v. 1.01) model in conjunction with SCI
- GROW to estimate Tier 1 pesticide concentrations in ground water used as drinking water (USEPA, 2012 d )
. PRZM
- GW input parameters are summarized below in **Table 6**
. A cumulative annual application rate of 2.3 3 kg a.i./ ha (2.08 lbs a.i./ A) was used in PRZM
- GW . This rate represent s the registrant’s proposed most conservative use pattern ( i
. e . four (4) crop production seasons per calendar ye ar for use on both tomatoes and basil). PRZM
- GW v.1.01 is limited to eleven (11) pesticide application events per year. In order to model 16 application events using 11 input events , v alues for the following input parameters were adjusted : 1) single
- event maximum application rate; 2) number of application events per ye ar; and , 3) application interval , 4) number of ye ars to simulate
. The single
- event maximum application rate was increased from 0.14 7 kg a.i./ ha (0.13 lbs a.i./A) to 0.21 2 kg a.i. / ha (0.19 lbs a.i./ A). C orresponding ly , the number of annual applicati on events decreased fro m sixteen (16) to eleven (11). Moreover, the application interval was equally distributed across the calendar ye ar. This increased the proposed label’s minimum application interval from 7 to 33 days
. The cumulative annual application rate of 2.3 3 kg a.i. / ha (2.08 lbs a.i./A) , however, remains consistent with the registrant’s proposed label product application scenario. Because PRZM
- GW is limited to 800 total application events, the extended simulati on was conducted every

year through ye ar 72.10

An anal ys is was performed on the effects of adjusting PRZM
- GW input parameters . Results indicate no difference as a result of using higher single
- event application rates, reduced number s of applications per year, and increased application interval s with respect to those of the proposed product label
. **Table 6**  **. PRZM -**  **GW (Version 1.01**  **) Input**  **Parameters Parameter**  **Value Justification**  **Source** Application Rate 1 ) (kg a.i./ ha) 0. 212 See text above table. Maximum annual application rate is divided into 11 application events spread across

the year. Proposed Label Application Events (per year) 1 1 Proposed Label Application interval (days) 33 Proposed Label Application Metho d 2 1) Proposed use pattern. 2) Above canopy selected : product is appli ed to target foliage. Proposed Label USEPA, 2012 c Initial Application D ate 2&3 ) February 2 1) Proposed f our crop production seasons during the calendar year
. 2) Eleven (11) application events evenly distributed
. 3) Sensitivity analysis (see text above table) USEPA, 2012 c Hydrolysis Half
- life (days) 1900 Represents the study value at pH 7. 46800007 Aerobic Soil Metabolism Half
- life (25  C) (days) 133 Represents 3x the single acceptable half
- life at 25°C
. 46800020 Organic Carbon Partition Coefficient (KOC ) (ml/g OC ) 5 75 Represents the mean of three KOC values 46800040 **Abbreviations:** A= acre; a.i. = active ingredient; cm = centimeters; ha = hectare; kg = kilo grams; ml = milliliter ;  C = degree Celsius **Note(s):** 1) Unlike the other two models used in this drinking water assessment, the pesticide appli cation rate for PRZM
- GW requires me tric units. 2) The initial application date selected represents eleven (11) evenly distributed application dates ( i.e. approximately every 33 days) during the calendar year , beginning February 2
. 3) Calendar dates are set to “Absolute.” **3.2 Model**  **Results** Results of the three models used in this drinking water assessment are summarized in **Table 1**
. FIRST model estimated drinking water concentrations ( EDWCs ) were 79 μg/L for acute exposure and 9.0 μg/L for chronic exposure. The SCI
- GROW EDWC was 0.18 μg/L. PRZM
- GW EDWCs are tabulated in **Table 7**
.11

For the PROZM
- GW model, all six geographic scenarios were model ed as surrogates for tomato and basil crops
. The Wisconsin corn scenario provi ded the most conservative estimate s for acute and chronic drinking water exposure concentrations , at 87 and 7 9 μg/L , respectivel y . **Table 7**  **. PRZM -**  **GW E**  **stimated D**  **rinking W**  **ater C**  **oncentration s**  **and Average Breakthrough Time for**  **Mand ipropamid**  **Use Scenarios**  **1) .**  **Crop Scenario**  **Max imum**  **Daily Concentration** 

**- Acute**  **- (μg/L)**  **Ave rage** 

**Breakthrough Time**  **(y ea**  **rs) Post**  **- breakthrough** 

**Average**

**- Chronic**  **- (μg/L)**  Tomato DMV corn 47 14 40 Tomato FL citrus 57 14 5 2 Tomato FL potato 2) 0.1 4 34 0.0 8 Tomato GA peanut2) 1 1 28 1 0 Tomato NC cotton 3 1 16 26 Tomato WI corn2) **87 28**  **79 Abbreviations:**  μg = micro grams ; L = liter **Note(s):** 1) PRZM
- GW model results are reported to two (2) significant figures. 2) The PRZM
- GW extended weather files were created and used for these scenarios.12

**Figure 1**  **: PRZ M**  **- GW WI Corn Extended Weather Scenario** 

Uncertainty regarding PRZM
- GW outputs results from the extended time period of ground water flow and the model’s underlying assumptions, including that soils are sterile below a 1
- meter depth. Bacteria in soils greater than one meter below the surface may degrade the residues of concern (ROC), however potentially at a slower rate than in the surface lay er, and may potentiate over years or decades in order to degrade the ROC at a faster rate. Mandipropamid residues of concern have an average breakthrough time of 28 years with the Wisconsin scenario. Breakthrough times for PRZM
- GW have been up to one order of magnitude shorter than observed for bromide (USEPA, 2012 e) and up to one order of magnitude longer than observed for oxamyl (MRID 45591605). Also, the model represents a drinking water well that is surrounded by a large pesticide
- treated area. Most drinking water wells are not surrounded by large pesticide
- treated areas. Therefore, horizontal convection and dispersion may attenuate persistent, dissolved residues such as these over time.13

**References** MRID 45591605. Hiscock, A., R. Warren, and B. Patterson. A Small

- Scale Prospective Groundwater Monitoring Study for Oxamyl. DuPont Report No. AMR 4318
- 97. Unpublished study

conducted by

Stone Environmental, Inc., Ecologic, Inc., Agricultural Sy stems Associates, AGVI SE Laboratories, Centre Anal ytical Laboratories , Inc., and E.I. du Pont de Nemours and Company ; submitted by E.I . du Pont de Nemours and Company , Wilmington, DE. Jan. 14, 2002. USEPA, 2001 a . FIRST User’s Manual: FQPA Index Reserovir Screening Tool . U.S. Environmental Protection Agency , Office of Pesticide Programs, Environmental Fate and Effects Division. August 1, 2001. USEPA, 2001 b
. SCI

- GROW Screening Concentration In Ground W ater: User Manual. U.S. Environmental Protection Agency , Office of Pesticide Programs, Environmental Fate and Effects Divis ion. November 1, 2001. USEPA. 200 6
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. USEPA. 200 7
. Drinking water assessment for mandipro p amid and its two degradates (SY N500003, SYN504851) use on brassica vegetables, bulb vegetables, cucurbits, fruiting vegetables, grapes, leafy vegetables, potatoes, tomatoes, tuberous and corn vegetables
. DP barcode D339258
. U. S. Environmental Protection Agency, Office of Prevention, Pesticides, and Toxic Substances, Environmental Fate and Effects Division. Memorandum to the Health Effects Division. April 23 , 200 7
. USEPA, 2008 a . FIRST FQPA Index Reservoir Screening Tool, Version 1.1.1. U.S. Environmental Protection Agency , Office of Prevention, Pesticides, and Toxic Substances, Environmental Fate and Effects Division. March 25, 2008. USEPA. 2008 b
. Fate, Transport and Transformation Test Guidelines : OPPTS 835.1230 Adsorption/ Desorption (Batch Equilibrium) , U.S. Environmental Protection Agency , Office of Prevention, Pesticides, and Toxic Substances (7101), Environmental Fate and Effects Division. EPA 712
- C
- 08
- 009, October, 2008. USEPA. 2008 c . Fate, Transport and Transformation Test Guidelines: OPPTS 835.4100 Aerobic Soil Metabolism; and, OPPTS 835.4200 Anaerobic Soil Metabolism , U.S. Environmental Protection Agency , Office of Prevention, Pesticides, and Toxic Substances (7101), Environmental Fate and Effects Division. EPA 712
- C
- 08
- 016, EPA 712
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- 017, October, 2008. USEPA. 2009. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides ; version 2.1
. U.S. Environmental Protection Agency , Office of Pesticide Programs, Environmental Fate and Effects Division. Oct. 22, 2009.14

USEPA. 2011. Mandipropamid: Drinking Water Exposure Assessmnt of Section 3 new Use for Outdoor; Non

-

food Crops. DP barcode D383758. U.S. Environmental Protection Agency , Office of Pesticide Programs, Environmental Fate and Effects Division. Memorandum to the Registration. Division. March 2, 2011. USEPA. 2012 a . Guidance on Development and Use of Percent Cropped Area and Percent Turf A rea Adjustment Factors in Drinking W ater Exposure Assessments: 2012 Update. Internal Environmental Fate and Effects Division memorandum. U.S. Environmental Protection Agency , Office of Chemical Safety and Pollution Prevention. Mar. 16, 2012. USEPA. 2012 b
. Guidance for Using PRZM
- GW in Drinking W

ater Exposure Assessments. U.S. Environmental Protection Agency , Office of Pesticide Programs, Environm ental Fate and Effects Division . Oct. 15, 2012. USEPA. 2012 c . Guidance for Selecting Input Parameters for Mod eling Pesticide Concentrations in Groundwater Using the Pesticide Root Zone Model
. Version 1.0 . U.S. Environmental Protection Agency , Office of Pesticide Programs, Environm ental Fate and Effects Division; and, Health Canada, Pesticide Management Regulatory Agency , Environmental Assessment Directorate. Oct. 15, 2012. USEPA. 2012 d
. Approval of PRZM

- GW for Use in Drinking W

ater Exposure Assessments . U.S. Environmental Protection Agency , Office of Pesticide Programs, Environm ental Fate and Effects Division , Memorandum to the Environmental Fate and Effects Division
. Dec. 11 , 2012. USEPA. 2012 e . Identification and Evaluation of Existing Models for Estimating Environmental Pesticide Transport to Groundwater. Final Report (Draft). U.S. Environmental Protection A gency ; Health Canada. Jan. 27 , 2012. USEPA. 2013. Guidance for Modeling Pesticides Total Toxic Residues (TTR)

- DRAFT: v.01. U.S. Environmental Protection Agency , Office of Pesticide Programs, Environmental Fate and Effects Division. January 3, 2013.15

**Appendix A. Exposure Model Input/Output**  **Files** FIRST and SCI
- GROW O utput F iles, with input values embedded in the O utput F iles. Mandi_FIRST.txt Ma nd i_SCI-G RO W. tx t PRZM
- GW Input Files

PR ZM_GW. zi p **Appendix B. Calculations** Aerobic Aquatic Metabolism Total Residue:
Aerobi c_A qua ti c_Tot alResi due. xl sx Aerobic Soil Metabolism with R model degradation kinetics:

Aerobic Soil Me tab ol is m. xl sx Soil Adsorption/ Desorption:

Ad sorp-D

esorp. xl sx