1

OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 128940

Barcode: D422918

March 4, 2015

MEMORANDUM

Subject: Drinking Water Assessment for Proposed New Uses (R170, PP# 4F8294) 

for Flutriafol for the establishment of tolerances for residue on Hops (ESubmission 6115).

TO: Tamue Gibson, Risk Manager Reviewer 

 Hope Johnson, RM 21

Fungicide Branch

Registration Division (7505P)

Charles (Billy) Smith, Branch Chief

RAB1

Health Effects Division (7509P)

 

THROUGH: Dana Spatz, Branch Chief

Environmental Risk Branch 3

Environmental Fate and Effects Division 

 

FROM: James K. Wolf, Ph.D., Environmental Scientist

Environmental Risk Branch 3

Environmental Fate and Effects Division (7507P)

REVIEWED BY: James A. Hetrick, Ph.D., Senior Science Advisor

Rosanna Louie-Juzwiak, RAPL

Environmental Risk Branch 3

Environmental Fate and Effects Division 

This memo presents recommended drinking water exposure concentrations for the proposed 

new use on or in hops for the Cheminova Flutriafol Technical (80.0 % a.i.; EPA Reg. No. 4787-55),
2

Cheminova Flutriafol Technical 98.3% (EPA Reg. No. 4787-61), and TopGuard® Fungicide (11.8 % 

a.i.; EPA Reg. No. 67760-75) Supplemental Labeling).

The estimated drinking water concentrations (EDWCs) for flutriafol for use in the human health 

risk assessment are summarized in Table 1. The EDWCs for flutriafol in groundwater as a source

for drinking water are not expected to exceed 193 μg/L for peak and the 165 μg/L for long-term 

average concentrations. For the proposed new uses, the EDWCs for flutriafol in surface water

source drinking water are not expected to exceed 15.9 and 5.39 μg/L for peak and chronic 

exposure, respectively, and 3.53 μg/L for cancer. EFED recommends that the Health Effects 

Division use 193 μg/L for the peak concentration and the 165 μg/L for long-term average 

concentration in the human health assessment. 

This drinking water exposure assessment is a screening-level assessment using the PRZM-GW

(version 1.07) (groundwater) and the SWCC (version 1.106) (surface water) models1 and is based 

upon the maximum number of applications, maximum application rates, and minimum 

reapplication intervals (Table 2). The estimated flutriafol concentrations in groundwater are 

recommended for the Health Effects Division’s (HED) human health risk assessment as the 

current EFED policy is to recommend the highest estimated drinking water concentrations 

(EDWCs). It should be noted that the estimates for both surface water and groundwater differ

somewhat from the previous assessment even though the application rates and environmental 

fate data used for model inputs are same, the models are not. The SWCC (Surface Water 

Concentration Calculator) has replaced PRZM/EXAMS (and FIRST) and a more recent version of 

PRZM-GW (with updated standard groundwater scenarios) was used for this assessment (1.07 

versus 1.01). Because the maximum use rates (per application and per year basis) is the same for 

the other uses, this assessment would update the EDWCs for flutriafol for all uses.

 

Uncertainty exists in these EDWCs as the estimates may not consider all dissipation/degradation 

pathways, especially for groundwater, and it is also unlikely that flutriafol, a fungicide, would be 

used continually for a 30 year or longer period. It also should be noted that while these 

screening-level EDWCs are representative of potential upper bound exposures, these predictions 

are based on exposure scenarios that are based on known vulnerable sites – shallow, unconfined 

aquifers under an agricultural field with leaching-prone soils, and adequate precipitation and/or 

irrigation. Furthermore, it is unlikely that people will be exposed to flutriafol concentrations at 

these levels based on the available fate data, as well as the predicted breakthrough time of over 

10 years. The surface water scenarios were selected for the proposed hops use and may not 

represent the most vulnerable surface water associated with other use sites. However, the 

estimates for surface water are less than those predicted for groundwater.

 

 

1 http://www.epa.gov/oppefed1/models/water/models4.htm and http://www.epa.gov/oppefed1/models/water/
3

Table 1. Maximum Tier I Surface Water and Groundwater EDWCs in μg/L resulting from the proposed use of flutriafol 

on hops with 30-year simulations [4 applications @ 0.114 lb a.i./A/year]. 

Drinking water source (model) 1-in-10 year 30-year simulation 

Acute Chronic Acute Chronic/Cancer

Surface water (SWCC)a,b 15.9 5.39 - 3.53

Ground water (PRZM-GW, v1.07)

c

- - 193 165 

a Michigan Bean Standard Scenario (included with the SWCC).b Note: no PCA is applied to these concentrations.

c North Carolina Eastern Coastal Plain Scenario.

Previously, HED determined that the 1,2,4-triazole (and the triazole conjugates) degradates 

should be considered residues of concern in the human health risk assessment. 1,2,4-Triazole 

and triazole conjugates triazole analine and triazole acetic acid, are common degradates of 

conazole pesticides, and are addressed in a separate document2 which was prepared by EFED to 

address the inclusions of 1,2,4-Triazole and triazole conjugates in Tier 2 drinking water 

assessments. 

Proposed New Use 

TopGuard®fungicide is formulated as a soluble concentrate containing 11.8 % of the active 

ingredient (a.i.) flutriafol (1.04 lb a.i./gallon of product) and is proposed for use on or in hops. 

The proposed methods of application are broadcast foliar by ground and air spray methods. 

Flutriafol may not be applied by chemigation. The maximum rate proposed for hops is 

comparable to application rates, number of applications, and seasonal maximum rate previously 

assessed (Table 2).

Table 2. Flutriafola Application Rates for Proposed New Use and some Previously Assessed Rates. 

Crop or Crop Group 

Maximum Single 

Application Rate (lb 

a.i./A) 

Number of 

Applications 

(Minimum 

Reapplication 

Interval) 

Maximum Seasonal 

Use Rate (lb a.i./A) 

Maximum Proposed Hops Use Rates

Hopsa 0.114 4 (14) 0.455

Maximum Rates Previously Assessed

Cucurbits, Peppers and other Fruiting 

vegetables, Pecan and other Tree 

Nuts, Stone fruit

0.114 4 (7) 0.455

a EPA Reg. No. 67760-75 TOPGUARD®

(11.8% a.i.) Density = 1.04 lb a.i./gallon * 1 gallon/128 fl oz = 0.008125 lb a.i./fl oz; 0.455 lb 

a.i./A/year (56 fl oz product/A/year).

 

 

 

2 1,2,4-Triazole, Triazole Alanine, Triazole Acetic Acid: Drinking Water Assessment in Support of Reregistration and Registration 

Actions for Triazole-derived Fungicide Compounds. 02/28/06. PC 600074, 600011, 600082 D320682.
4

Environmental Fate and Transport Characterization 

 

Flutriafol is persistent in soil (t1⁄2>1 year) and moderately mobile (Koc <500 mL/goc) in the 

environment. Flutriafol is expected to dissipate slowly with a half-life of years [never achieved in 

terrestrial field studies] in the terrestrial environment and therefore repeated applications may 

lead to accumulation of flutriafol residues in soil. Flutriafol is expected to reach surface water 

through drift and runoff, and groundwater via leaching. Detailed information on the 

environmental fate of flutriafol can be found in prior assessments (D360863, D356830, D340508, 

D396757). The environmental fate data are summarized in Table 3.

 

Table 3. Summary of physical/chemical and environmental fate and transport properties of flutriafol. 

Parameter Value(s) (units) Source (MRID) Comment 

Chemical Name Flutriafol

CAS Name:

α-(2-fluorophenyl)-α-(4-fluorophenyl)-

1H-1,2,4-triazole-1-ethanol

IUPAC Name: 

(RS-1-(2-fluorophenyl)-α-(4-

fluorophenyl)-1H-1,2,4-triazole-1-

ethanol

47129901

-

Chemical Structure -

Molecular Formula C16H13F2N3O 47129901 -

Molecular Weight 301.3 amu 47129901 -

Solubility (20 °C) 130 mg/L 47129901 -

Vapor Pressure (20 °C) 4 x 10-7 Pa 

3.00025x10-9torr

47129901 -

Henry’s Law constant 9.16 x10-12 atm m3/mol - Calculated

pKa (20 °C) 2.3 47129901 -

Octanol-Water 

Partition Coefficient 

(log KOW @ pH 7)

2.29 47129901 -

Hydrolysis Half-life (t1⁄2) 

pH 5 and 7 Stable 47090416 Stable at all pHs. 

Aqueous Photolysis 

Half-life (t1⁄2)

Stable 47090417

47287601

Florida sunlight 

Conditions latitude 

not specified -

Soil Photolysis Half-life 

(t1⁄2)

Stable 47090420

47418401

D353179 D350986

[@ 37.5°N]
5

Parameter Value(s) (units) Source (MRID) Comment 

Aerobic Soil 

Metabolism Half-life 

(t1⁄2)

697 weeks

120, 161, 257, 84, 98, and 315 weeks 

347, 239, and 3,466 weeks

47090421

47090422

47090423

Note: values in 

weeks. [see D416293, 

D416294]

Anaerobic Aquatic 

Metabolism (t1⁄2)

Stable 47090424 (Total system)

Aerobic Aquatic 

Metabolism t1/2 = 42.6 and 36.3 days 47090419 (Total system)

Organic Carbon 

Partition

Coefficient (KOC)

498, 205, 379, 230, 340, 428, 140 

mL/gOC

47090425

47090426

47090427

-

Soil Partition 

Coefficient (Kd)

3.7, 13.6, 10.6, 6.5, 2.0 mL/g

47090425

47090426

47090427

-

Terrestrial Field 

Dissipation

Half-life (t1⁄2)

t1/2 = 1155 days 

3466 days

2310 days

1155, 866, 770, 866, 1155, 1386 

days

47115502

47090431

- Loamy sand.

- Clay loam.

- Sandy clay loam. 

- Study conducted at 

6 sites in Germany, 

soil texture classes 

were not reported. 

No major degradation products (i.e., > 10% of applied radioactivity) were identified in any water 

or soil studies. The degradation products formed in the laboratory studies are discussed in detail 

in prior assessments (D412882). Two minor transformation products3 were identified in the 

photolysis on soil study [1H-1,2,4-Triazole and 2,4’-Difluorobenzophenone] and three minor [1H1,2,4-Triazole; Triazole-1-acetic acid; 1,2,4-Triazole-1-alanine] degradation products were 

identified in the anaerobic aquatic metabolism study.

 

Modeling 

 

The Tier 1 drinking water estimates for the proposed hops were modeled using the PRZM-GW 

model (version 1.07) estimates for groundwater (USEPA, 2014). For surface water, the SWCC

(version 1.106) was used to confirm that the surface water estimates remained less than the 

groundwater EDWCs. The six standard PRZM-GW scenarios4 used in the groundwater 

simulations were developed to be representative of known vulnerable sites—shallow, 

unconfined aquifers under an agricultural field with leaching prone soil and adequate 

precipitation and/or irrigation. Output values represent pesticide concentrations that may be 

observed in private drinking water wells resulting from the use of groundwater vulnerable to 

pesticide contamination. The results are expected to represent the upper bound values on the 

concentrations of flutriafol that might be found in drinking water supplied by vulnerable 

groundwater sources. The 90th percentile upper bound on the mean aerobic soil metabolism 

 

3 Note the previous drinking water assessment (D360863) incorrectly included the 1,2,4-Triazole-1- acetic acid degradate. This 

error would not change the estimated drinking water concentrations (EDWCs).

4

Florida Central Ridge, Florida Potato, Wisconsin Central Sands, Georgia Southern Coastal Plain, North Carolina 

Eastern Coastal Plain, and Delmarva Peninsula. 
6

half-life was re-evaluated and the average Koc for modeling were used for modeling inputs 

(USEPA. 2014; D416293, D4162045). The selection and procedures for selecting model input 

parameters followed EFED guidance6. 

 

Modeling Inputs 

The basic input requirements for PRZM-GW and the SWCC models are summarized in Table 4.

Table 4. PRZM-GW and SWCC input parameter values for flutriafol. 

Parameter (units) Value Source 

(MRID) 

Comment

Both PRZM-GW and the SWCC Models 

Organic Carbon Partition 

Coefficient (Koc; mL/goc)

322

47090425

47090426

47090427

Represents the mean value of seven values 

ranging from 140 to 498 mL/goc for the 

parent compound. 

Aerobic Soil Metabolism Half-life

@ 25°C (t1⁄2) (days) 7,202

47090421

47090422

47090423

Represents 90% Upper bound confidence 

interval for 10 values for the aerobic soil 

metabolism of the parent compound.

[see D416293, D416294]

Hydrolysis Stable 47090416 Stable at pH 5, 7, 9

First App; Days After Emergence 

(DAE) 10 -

10, 24, 38, 52 days after emergence (defined 

by scenario)

SWCC Model only 

Aerobic Aquatic Metabolism 

Half-life @ 25°C (t1⁄2) (days) 49.2 47090419

Represents the 90th percentile of the upper 

confidence bound on the mean of two halflife values (39.5).

Anaerobic Aquatic Metabolism

Half-life @ 25°C (t1⁄2) (days) 0 - No Data

Anaerobic Soil Metabolism

Half-life @ 25°C (t1⁄2) (days) 0 47090424 >365 days in Total system (water/sediment)

Benthic Metabolism Half-life @ 

25°C (t1⁄2) (days) 0 - No Data

Aqueous Photolysis Half-life @ 

25°C (t1⁄2) (days) 0

47109017

47287601

Stable

Soil photolysis 0 47418401 Stable

Foliar Half-life @ 25°C 0 - No Data

Molecular Weight (g) 301.3 47129901 -

Vapor Pressure @ 25°C (torr) 3.0x 10-9 47129901 -

Solubility (mg/L) @ 20°C 130 47129901 -

 

5

 USEPA, 2014. Drinking water assessment for proposed new uses (R190, PP# 3F8199) of Flutriafol on leafy vegetables (Group 4), 

brassica (cole) leafy vegetables (Group 5), grain sorghum, and cotton and (R190, PP# 3F8174) for cucurbit vegetables, fruiting 

vegetables, strawberries, tree nuts, and wheat uses. (D416293, D416294; 04/03/14). 

6 http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm
7

Parameter (units) Value Source 

(MRID) 

Comment

Spray Drift Fraction (aerial spray) 0.135 EFED Guidance

Application Efficiency 

(aerial spray) 0.95 EFED Guidance

Michigan Application (first) Days 

After Emergence (DAE) 10 10, 24, 38 and 52 Days after emergences

Oregon Application (first) Days 

After Emergence (DAE) 50 50, 64, 78, 92

Surface Water Concentrations 

The EDWCs for flutriafol (parent) for surface water using the SWCC model for the maximum hops 

use rates are provided in Table 5. Two sites (Oregon Hops and MI Bean) were considered for 

surface water to confirm that groundwater estimates remained higher then surface water. The 

Michigan bean exposure scenario was also modeled as a surrogate for use in Wisconsin because 

of Oregon’s lower precipitation and that hops are also grown in Wisconsin7. The previous 

estimate using the FIRST model are also included in Table 5. The highest peak 1-in-10 year (15.9 

μg/L) and annual average flutriafol concentration (5.4 μg/L) and 30 year average (3.5 μg/L) were 

estimated using the SWCC. Representative input/output file is given in Appendix 1.

Table 5. Surface Water EDWCs in μg/L resulting from the proposed flutriafol use rate on hops [4 applications @ 0.114 

lb a.i./A/year] using the SWCC (this assessment) and FIRST (previous assessments). 

Surface Water Concentrations 1-in-10 year 30-year simulation 

Acute Chronic Acute Chronic/Cancer

Oregon Hops Scenario (SWCC)a 4.65 1.81 - 1.37

Michigan Bean (SWCC)a 15.9 5.39 - 3.53

Previous Drinking Water Assessment (D416293, D416293) 

Surface water (FIRST)b 29.48 2.92 -

a Note: No PCA has been applied to these concentrations.

b PCA of 0.91 was used. 

Groundwater Concentrations 

The highest daily groundwater EDWCs estimated by PRZM-GW (version 1.07) ranged from 51 to 

193 μg/L and the simulation averages ranged from 44 to 165 μg/L (Table 6) depending upon the 

scenario. The Wisconsin Central Sands and North Carolina Eastern Coastal Plains had the highest 

EDWCs. Representative PRZM-GW input/output files are given in Appendix 1. Due to the 

persistence and mobility of flutriafol, the date of the initial application made little difference in 

the estimated groundwater concentrations with PRZM-GW.

The PRZM-GW (version 1.01) estimates are also listed in Table 7 for comparison. With the 

exception of the NC Eastern Coastal Plain scenario, the results with version 1.07 (Table 6) are 

 

7 http://labs.russell.wisc.edu/vegento/files/2012/08/2012-Hop-Growers-Meeting_Groves.pdf
8

similar to those obtained with version 1.01 (Table 7). The difference appears to be related to 

changes in the soil water holding property values which were updated in standard groundwater

scenarios. 

 

Table 6. PRZM-GW (version 1.07) estimated flutriafol groundwater concentrations (EDWCs) for the 

six standard scenarios. 

4 applications @ 0.114 lb a.i./A; 14-day reapplication interval

 

Highest daily 

Concentration 

Post-Breakthrough 

Average 

Average Breakthrough Time 

Scenario μg/L Days 

Delmarva Peninsula 120 111 4865

FL Central Ridge Citrus 132 117 3956

FL Potato 69.8 60 7611

GA Southern Coastal Plain 50.7 44.4 6552

NC Eastern Coastal Plain 193 165 4932

WI Central Sands 142 129 6683

Table 7. PRZM-GW (version 1.01) estimated flutriafol groundwater concentrations (EDWCs) for the 

six standard scenarios (USEPA, 2014; D416293, D416294). 

4 applications @ 0.114 lb a.i./A; 7-day reapplication interval

 Highest daily 

Concentration 

Post-Breakthrough 

Average 

Average Breakthrough Time 

Scenario μg/L Days 

Delmarva Peninsula 100 86.4 2872

Florida Central Ridge 103 89.2 2865

Florida – Potato 30 yr 60.3 53.2 7031

GA - Southern Coastal Plain 49.2 43.2 6245

NC Eastern Coastal Plain 123 104 3664

WI Central Sands 124 115 4018

Cotton 1 application @ 0.26 lb a.i./A and 2 @ 0.114 lb a.i./A (7-day interval) 

Delmarva 107.7 92.8 2872

Florida Central Ridge 110.3 95.0 2864

Florida – Potato 64.6 57.0 7035

GA - Southern Coastal Plain 52.6 46.6 6245

NC Eastern Coastal Plain 132.2 110.4 3664

WI Central Sands 133.5 124.4 4018 
9

Appendix 1. Representative Output from the SWCC and PRZM-GW Models. 

Surface Water (Surface Water Concentration Calculator, version 1.07)

Summary of Water Modeling of flutriafol and the USEPA Standard Reservoir

Estimated Environmental Concentrations for flutriafol are presented in Table 1 for the USEPA standard reservoir with the 

MIbeansSTD field scenario. A graphical presentation of the year-to-year peaks is presented in Figure 1. These values were 

generated with the Surface Water Concentration Calculator (SWCC Version 1.106). Critical input values for the model are 

summarized in Tables 2 and 3.

This model estimates that about 2.4% of flutriafol applied to the field eventually reaches the water body. The main mechanism of 

transport from the field to the water body is by runoff (81.2% of the total transport), followed by spray drift (17.1%) and erosion 

(1.7%).

In the water body, pesticide dissipates with an effective water column half-life of 65.3 days. (This value does not include 

dissipation by transport to the benthic region; it includes only processes that result in removal of pesticide from the complete 

system.) The main source of dissipation in the water column is metabolism (effective average half-life = 124.6 days) followed by 

washout (137 days) and volatilization (4.031344E+07 days).

In the benthic region, pesticide is stable. The vast majority of the pesticide in the benthic region ( 97.2%) is sorbed to sediment 

rather than in the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for flutriafol.

Peak (1-in-10 yr) 15.9

4-day Avg (1-in-10 yr) 15.4

21-day Avg (1-in-10 yr) 13.7

60-day Avg (1-in-10 yr) 11.5

365-day Avg (1-in-10 yr) 5.39

Entire Simulation Mean 3.53

Table 2. Summary of Model Inputs for flutriafol.

Scenario MIbeansSTD

Cropped Area Fraction 1.0

Koc (ml/g) 322

Water Half-Life (days) @ 25 °C 49.2

Benthic Half-Life (days) @ 25 °C 0

Photolysis Half-Life (days) @ 40 °Lat 0

Hydrolysis Half-Life (days) 0

Soil Half-Life (days) @ 25 °C 7202

Foliar Half-Life (days) 0

Molecular Wt 301.3

Vapor Pressure (torr) 3.0e-9

Solubility (mg/l) 130
10

Table 3. Application Schedule for flutriafol.

Date (Days Since 

Emergence)

Type Amount (kg/ha) Eff. Drift

10 Foliar 0.128 0.95 0.135

24 Foliar 0.128 0.95 0.135

38 Foliar 0.128 0.95 0.135

52 Foliar 0.128 0.95 0.135

Figure 1. Yearly Peak Concentrations

PRZM-GW (version 1.07)

Groundwater Analysis for flutriafol and the NC Eastern Coastal Plain - Norfolk Loamy Sand - Cotton 

Scenario

Estimated groundwater concentrations and breakthrough times for flutriafol are presented in Table 1 for the NC 

Eastern Coastal Plain - Norfolk loamy sand - Cotton groundwater scenario. A graphical presentation of the daily 

concentrations in the aquifer is presented in Figure 1. These values were generated with the PRZM-GW (Version 

1.07). Critical input values for the model are summarized in Tables 2 and 3.

Table 1. Groundwater Results for flutriafol and the NC Eastern Coastal Plain - Norfolk loamy sand - Cotton 

Scenario.

Peak Concentration (ppb) 193

Post-Breakthrough Mean 

Concentration (ppb)

 165

Entire Simulation Mean 

Concentration (ppb)

 94.3

Average Breakthrough Time 

(days)

4931.997

Throughputs 2.222224
11

Table 2. Chemical Properties for Groundwater Modeling of Flutriafol.

Koc (ml/g) 322

Surface Soil Half Life (days) 7202

Hydrolysis Half Life (days) 0

Diffusion Coefficint Air (cm2/day) 0.0

Henry's Constant 0.0

Enthalpy (kcal/mol) 0.0

Table 3. Pesticide application scheme used for flutriafol. This application scheme was applied every year of 

the simulation.

Application Days 

Relative to Emergence 

Date (05/15)

Application Method Application Rate

(kg/ha)

10 Above canopy application 0.128

24 Above canopy application 0.128

38 Above canopy application 0.128

52 Above canopy application 0.128

Figure 1. Aquifer Breakthrough Curve for flutriafol and the NC Eastern Coastal Plain - Norfolk Loamy Sand 

- Cotton Scenario