1

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

July 9, 2013

PC Code: 036602

MEMORANDUM DP Barcode: 409108 & 409109

SUBJECT: Mandipropamid: Drinking Water Exposure Assessment for Proposed Section 3 

New Uses on: Basil, Ginseng and Succulent Beans; and Expanded Uses on Bulb 

Vegetables, Cucurbits, Grapes, and Fruiting Vegetables including Tomatoes.

FROM: Richard Shamblen, Biologist

ERB2/EFED (7507P)

THROUGH: Greg Orrick, Environmental Scientist

Brian Anderson, Branch Chief

ERB2/EFED (7507P)

TO: Dennis McNeilly, Risk Assessor

Christina Swartz, Branch Chief

RAB2/HED (7509P)

Tony Kish, Risk Manager, RM Team 20

Rosemary Kearns, Risk Manager Reviewer

Laura Nollen, Biologist, RIMU ERB/RD

FB/RD (7505P)

The Environmental Fate and Effects Division (EFED) conducted a Tier 1 drinking water 

exposure assessment for the fungicide mandipropamid. The registrant seeks a Section 3 new use

registration for basil, ginseng and succulent beans; and expansion of currently registered 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 rate exceeds those assessed in previous drinking 

water exposure assessments. 

Tier 1 exposure model results 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 μg/L for acute and chronic exposures, 

respectively. These values are as much as 480 times higher than SCI-GROW model results.

Maximum acute and chronic EDWCs in surface waters are 79 and 9.0 μg/L, respectively.
2

Table 1. Tier 1 Estimated Drinking Water Concentrations (EDWC) for Maximum Mandipropamid

Use Patterns.

Drinking Water Source

(Model, Version)

PCA

(%)

Crop Use Pattern

(Maximum Annual Rate)

Acute

(μg/L)

Chronic

(μg/L)

Surface Water (FIRST, 1.1.1) 91 Tomato & Basil

(2.08 lbs a.i./A) 79 9.0

Ground Water (PRZM-GW, 1.01) N/A Tomato & Basil

(2.08 lbs a.i./A)

87 79

Ground Water (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 previous Tier 1 drinking water assessments of mandipropamid produced nearly 

identical exposure estimates (USEPA, 2007; and, 2011). Results of multiple FIRST (v.1.1.0) 

model scenarios indicated EDWCs in surface waters ranging 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 by SCI-GROW (v. 2.3). PRZM-GW (v. 1.01) was not used. 

Differences between the previous two and current drinking water exposure assessments

reveal that ground water exposure concentrations decreased by more than a factor of 13, whereas 

acute surface water exposure concentrations nearly doubled. These differences are likely

attributed 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) Four seasons per year are assumed for tomato and basil, whereas only one season per 

year was assumed for previously assessed use sites1; 

2) Changes to EFED model input parameter guidance, version 2.1 (USEPA, 2009);

3) Higher KOC model input adjustments: mean (575 L/kg) used instead of lowest (405 L/kg); 

4) Lower aerobic soil metabolism model input values: 133 d instead of 81.3 d; 

5) Total Residue modeling approach (USEPA, 2013) was used to calculate aerobic aquatic 

metabolism input of 108 days instead of separately modeling a range of half-lives of 19 

to 1323 days for parent and degradates;

6) Percent Cropped Area (PCA) factor of 0.91 used instead of 0.87 (USEPA, 2012a); 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 Tyler of Syngenta to Johannes Corley of IR-4, February 31, 2013.
3

1. Use Characterization

Mandipropamid is a fungicide used to control downy mildew, phytophthora 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 chemigation2equipment. The proposed label 

specifies a maximum seasonal 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 expanded3and 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 application to tomato

and basil with up to four (4) crop production seasons per calendar year. 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

Rate1)

(lbs a.i./A)

Maximum

Number of 

Applications

per Season

Minimum

Application

Interval2)

(days)

Maximum

Annual 

Application

Rate3)

(lbs a.i./A)

Maximum

Number of

Applications

per Year3)

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 new use registrations for mandipropamid on

the three (3) following crops and crop groups, including hybrids 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 Tyler 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) crops and crop groups, including hybrids and varieties thereof:

1. Bulb vegetables including cultivars, varieties, and/or hybrids of these and others in

 the onion (dry) subgroup 3-07A: daylily; fritillaria; garlic; garlic (great-headed); 

garlic (serpent); lily onion; onion (Chinese); onion (pearl); onion (potato); shallot; 

and,

 the green onion (subgroup 3-07B): 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 true 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, straintneck 

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 kiwifruit): Amur river grape, gooseberry, grape, kiwifruit (hardy); maypop; 

schisandra berry; 

4. Fruiting Vegetable Group (except tomatoes) including cultivars, varieties, and/or 

hybrids of these and others in this group: African eggplant, bell pepper; cocona; 

eggplant, 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 has low to moderate mobility. The primary degradation route is typically expected 

to be metabolism with half-lives ranging from approximately 40 to 90 days in aerobic conditions 

in water and soil laboratory studies. Half-lives from field studies were similar and ranged from 

75 to 100 days. The fungicide degrades relatively quickly via photolysis with a half-life of 

approximately 2 days. However, photolysis 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 slowly via hydrolysis, 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 physical and chemical properties and environmental fate data, and corresponding 

sources of data for mandipropamid.

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 hydrolysis at 

the p = 0.05 confidence level. Based on the level of uncertainty in the hydrolysis 

study due to background variability, the degradation might be as fast as 1900 day at 

pH 7 and not be detected in the current 30 day study. In order to bound the effects of 

hydrolytic degradation in the PRZM-GW simulations, estimates were made using the 

1900 day hydrolysis half-life rather than assuming no hydrolytic degradation and the 

EDWC decreased from 90 to 79 day (12%).

2. Of the three aerobic aquatic metabolism studies, only one study (MRID 46800031) is

currently classified as “supplemental and upgradeable.” Additional information is 

needed related to identification of all major transformation products for both systems.

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) includes four foreign soils, for which 

taxonomic classifications are needed to clarify if they represent domestic agricultural 

use areas where the pesticide is anticipated to be applied. For this assessment, it is 

assumed that three U.S. soils from one study (MRID 46800040) are representative of 

agricultural use areas. Although the USEPA guideline requires five soil types 

(USEPA, 2008b), data from the three domestic soils were used for modeling 

purposes, pursuant to model input parameter guidelines, in the absence of additional 

acceptable data.

4. There are five aerobic soil metabolism studies representing seven soils, yet only one

study (MRID 46800020) with one soil type 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 representativeness of agricultural areas 

where the pesticide will be applied. Although the USEPA guideline requires four soil 

types for determination of transformation rates (USEPA, 2008c), the one soil type 

was used for modeling purposes, pursuant to model input parameter guidelines, in the 

absence of additional acceptable data.

Reported half-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

(C23H22ClNO4)

46800004

Vapor pressure (25 °C)1)

(mmHg)

<7.1x10-946800006

Aqueous solubility (25C)

(mg/L) 4.2 46800006

Henry’s Law Constant: calculated (25 °C)

(atm-m

3

/mol) <9.1x10

-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 significant degradation (pH 5)

1900 (pH 7)

1000 (pH 9)

46800007

Aqueous photolysis

half-life (25C)

(days)

1.9 46800009

Aerobic soil metabolism

half-life (25°C)

(days) (Soil Texture)

44 (Sandy loam) 46800020

Aerobic aquatic metabolism

half-life (25°C)

(days) (Aquatic sample system: Sediment)

79 (Swiss Lake: Loamy Sand)

94 (Calwich Abbey: Silt Loam)

46800031

Mobility

Freundlich organic carbon-normalized 

coefficient (KFOC)

2)

(mL/goc) (Soil Texture)

694 (Sandy loam)

406 (Loamy Sand) 46900040

625 (Loamy Sand)

Field Dissipation

Terrestrial field dissipation

half-life3)

(days) (Soil Texture)

75 (Sandy loam) 46800045

100 (Loamy sand) 46800046

82 (Loamy 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: 35-48x

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 KFOC (0.3) is less than the CV of Kd (0.5), thus sorption was correlated 

with organic carbon content. KFOC was calculated with the following equation: (KF/ % organic matter)*100

(USEPA, 2008b). 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 Modeling

3.1 Model Parameterization

3.1.1 FIRST (Version 1.1.1)

EFED used the FQPA5Index Reservoir Screening Tool (FIRST) Version 1.1.1 (USEPA, 

2008a) to calculate Tier 1 estimated drinking water concentrations (EDWC) for surface water 

systems. The model is used to estimate both acute and chronic potential concentrations in 

untreated drinking water (USEPA, 2001a). Model input parameters (USEPA, 2001a), values 

selected, brief justification statements for values selected (USEPA, 2009), and data sources are 

summarized below in Table 4. 

Total Residue (TR) kinetics calculations were used to estimate the aerobic aquatic 

metabolism half-life model input value (USEPA, 2013). TR kinetics calculations are presented in 

Appendix B. Total residues include the 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 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 number 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 Depth 

(cm) 0

Product is foliar applied via ground or 

aerial spray

Proposed label

Wetted-in No Not applicable US EPA, 2009

Solubility (25C)

(mg/L) 4.2 Maximum value at20 - 25C

46800006

Hydrolysis

Half-life

(days)

1900 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 90th percentile

confidence bound on the mean of two 

total residue half-lives.

46800031

Organic Carbon Partition 

Coefficient (KOC)

(mL/kgOC)

575 Represents the mean of three values. 46800040

Aerobic Soil Metabolism

Half-life

(days)

133 Represents 3x the single acceptable 

value.

46800020

Percent Cropped Area 

(PCA) Adjustment Factor

(decimal)

0.91 National-level PCA for all agricultural 

land US EPA, 2012a

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 model 
9

determine if mandipropamid potentially poses sufficient risk to warrant higher level assessment 

(USEPA, 2001b). Table 5 summarizes the SCI-GROW input parameters (USEPA, 2001b), 

justification for values selected (USEPA, 2009), and appropriate references and data sources 

(USEPA, 2001b; 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 number of applications per year

Proposed label

Meeting Minutes

Organic Carbon Partition 

Coefficient (KOC)

(mL/kgOC)

625 Median of three KOC values;

less than three-fold variation 46800040

Aerobic Soil Metabolism

Half-life

(days)

44

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-year 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, 

2012d). PRZM-GW input parameters are summarized below in Table 6.

A cumulative annual application rate of 2.33 kg a.i./ ha (2.08 lbs a.i./ A) was used in 

PRZM-GW. This rate represents the registrant’s proposed most conservative use pattern (i.e.

four (4) crop production seasons per calendar year 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, values for the following input parameters 

were adjusted: 1) single-event maximum application rate; 2) number of application events per 

year; and, 3) application interval, 4) number of years to simulate.

The single-event maximum application rate was increased from 0.147 kg a.i./ ha (0.13 lbs 

a.i./A) to 0.212 kg a.i./ ha (0.19 lbs a.i./ A). Correspondingly, the number of annual application 

events decreased from sixteen (16) to eleven (11). Moreover, the application interval was equally

distributed across the calendar year. This increased the proposed label’s minimum application 

interval from 7 to 33 days. The cumulative annual application rate of 2.33 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 simulation 

was conducted every year through year 72.
10

An analysis 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 

numbers of applications per year, and increased application intervals with respect to those of the 

proposed product label.

Table 6. PRZM-GW (Version 1.01) Input Parameters

Parameter Value Justification Source

Application Rate1)

(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) 11 Proposed Label

Application interval 

(days) 33 Proposed Label

Application Method 2

1) Proposed use pattern.

2) Above canopy selected: product is 

applied to target foliage.

Proposed Label

USEPA, 2012c

Initial Application

Date2&3) February 2

1) Proposed four crop production 

seasons during the calendar year.

2) Eleven (11) application events 

evenly distributed.

3) Sensitivity analysis (see text 

above table)

USEPA, 2012c

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/gOC)

575 Represents the mean of three

KOC values 46800040

Abbreviations: A= acre; a.i. = active ingredient; cm = centimeters; ha = hectare; kg = kilograms; ml = milliliter; C 

= degree Celsius

Note(s):

1) Unlike the other two models used in this drinking water assessment, the pesticide application rate for 

PRZM-GW requires metric 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 modeled as surrogates for 

tomato and basil crops. The Wisconsin corn scenario provided the most conservative estimates 

for acute and chronic drinking water exposure concentrations, at 87 and 79 μg/L, respectively.

Table 7. PRZM-GW Estimated Drinking Water Concentrations and Average Breakthrough Time

for Mandipropamid Use Scenarios1).

Crop Scenario

Maximum

Daily

Concentration

-Acute-

(μg/L)

Average

Breakthrough 

Time

(years)

Post-breakthrough 

Average

-Chronic-

(μg/L)

Tomato DMV corn 47 14 40

Tomato FL citrus 57 14 52

Tomato FL potato2) 0.14 34 0.08

Tomato GA peanut2) 11 28 10

Tomato NC cotton 31 16 26

Tomato WI corn2) 87 28 79

Abbreviations: μg = micrograms; 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: PRZM-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 layer, 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, 2012e) 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 

Systems Associates, AGVISE Laboratories, Centre Analytical 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, 2001a. 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, 2001b. SCI-GROW Screening Concentration In Ground Water: User Manual. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. November 1, 2001.

USEPA. 2006. Guidance for Developing a Tier 1 Drinking Water Exposure Assessment. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. Jan. 27, 2006.

USEPA. 2007. Drinking water assessment for mandipropamid and its two degradates 

(SYN500003, 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, 2007.

USEPA, 2008a. 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. 2008b. 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. 2008c. 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-C-08-017, 

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. 2012a. Guidance on Development and Use of Percent Cropped Area and Percent Turf 

Area Adjustment Factors in Drinking Water 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. 2012b. Guidance for Using PRZM-GW in Drinking Water Exposure Assessments. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. Oct. 15, 2012.

USEPA. 2012c. Guidance for Selecting Input Parameters for Modeling Pesticide 

Concentrations in Groundwater Using the Pesticide Root Zone Model. Version 1.0. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division; and, Health Canada, Pesticide Management Regulatory Agency, 

Environmental Assessment Directorate. Oct. 15, 2012.

USEPA. 2012d. Approval of PRZM-GW for Use in Drinking Water Exposure Assessments. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division, Memorandum to the Environmental Fate and Effects Division. Dec. 11, 

2012.

USEPA. 2012e. Identification and Evaluation of Existing Models for Estimating Environmental 

Pesticide Transport to Groundwater. Final Report (Draft). U.S. Environmental 

Protection Agency; 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 Output Files, with input values embedded in the Output Files.

Mandi_FIRST.txt Mandi_SCI-GROW.txt

PRZM-GW Input Files

PRZM_GW.zip

Appendix B. Calculations

Aerobic Aquatic Metabolism Total Residue:

Aerobic_Aquatic_Tot

al Residue.xlsx

Aerobic Soil Metabolism with R model degradation kinetics:

Aerobic Soil

Metabolism.xlsx

Soil Adsorption/ Desorption:

Adsorp-Desorp.xlsx