1 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION **UNITED ST AT**  **ES ENVIRONMENT AL**  **PROTECTION A GENCY** 

WA SHINGTON, D.C. 20460

PC Code: 128847 DP Barcode: 4 21092 **Date:** November 13 , 201 4 **MEMORANDUM SUBJECT:**  D rinking W ater E xposure A ssessment in support of the new use registration

of multiple difenoconazole formulated product s on Artichoke, Berry Bushberry

Subgroup 13 - 07B, Ginseng, and Bean and Pea, Dried Shelled (except Soy

b ean) Subgroup 6C as well as Conversion of Stone Fruit Crop Group 12 - 12 and Tree Nuts Crop Group 14 - 12 . **TO:** Laura Nollen , Risk Manager Reviewer

Barbara Madden, Risk M anager Marion Johnson, Branch Chief Registration Division (7505 P ) Thurston Morton , Chemist Elissa Reaves , Branch Chief Risk Assessment Branch IV Health Effects Division (750 9 P ) **FROM:** Faruque Khan, Ph.D., Senior Fate Scientist

Environmental Risk Branch I Environmental Fate and Effects Division (7507P) **APPROVED BY**  **:** Sujatha Sankula , Ph.D., Branch Chief,

Environmental Risk Branch I Environmental Fate and Effects Division (7507P) This assessment provides estimated drinking water concentrations (EDWC s ) of difenoconazole and its major metabolite, CGA - 205375 (M1) in surface water and groundwater in support of human health risk assessment on the Interregional Research Project Number 4 ( IR4 ) proposed new uses on gi nseng, artichoke, and conversion on stone fruit group 12 - 12 and tree nut group 14 - 12 . The Residues of Concern Knowledgebase Subcommittee (ROCKS) of the Health2

Effects Division (HED) recommended to include CGA - 205375 as a residue of concern for drinking water (USEPA, 20 11, D P 391350 ) . Therefore, this drinking water assessment was performed using total toxic residue (TTR; i.e. parent plus CGA 205375) method in support of the proposed Section 3 new uses following the approach used in a previous drinking water assessment for canola (US EPA 201 3 a , DP 412614 ). Foliar spray applications (both aerial and ground spray

application s) and chemigation , are being proposed for these crops . The EDWCs of difenoconazole and its major metabolite, CGA - 205375 (M1) were generated using a pp lication rate s of 0.46 to 0.52 lbs a.i./A. with the Surface Water Concentration Calculator model for surface water as well as the maximum application rate of 0.52 lbs a.i./A with the PRZM - GW and SCI - GROW models for groundwater. The Interregional Research Project Number 4 ( IR - 4 ) also revised the existing crop groupings b y converting stone fruit Group 12 to stone fruit Group 12 - 12 and nut tree Group 12 to nut tree Group 14 - 12. Since there are no changes in the application rates and methods for the revised crop groupings, previous drinking water assessments (stone fruit; USEPA, 2010; D P 426124 and tree nut; USE PA 2009, D P 340378) fulfill the requirement for refining EDWCs for these crops . EFED noticed that the application rate for cucur bit is higher in the submitted Inspire Super (EPA Reg. No. 100 - 1317) label as compared to previous label, which was stamped on August 03, 2012 . Since the maximum applicant rate of 0.52 lbs a.i. /A for cucurbit is higher than previously

assessed application rate of 0.46 lbs a.i. /A (USEPA 2009; D P 361398 the EDWCs for the revised rate of cucurbit w as reassessed . Surface water and gro undwater modeling were conducted for the maximum annual application rate of 0.46 to 0.5 2 lbs a.i ./A for aerial application only as aerial applications produce conservative estimates . Remaining model input parameters were chosen according to current guidance (USEPA, 200 9 and USEPA, 2013 b ). For surface water, the EDWCs for new uses and the revised application rate for cucurbit did not exceed the recommended peak (acute) concentration of 20.0 μg/L, annual mean (non - cancer chronic) concentration of 13.6 μg/L and the 30 year annual average concentration (cancer chronic) of 9.9 μg/L reported in the previous drinking water assessment based on grape use (US EPA, 2013; DP 398836 ). Recentl y, PRGM GW scenarios were revised and consequently the estimated PZRM - GW groundwater concentration s were reduced to 1.77 μg/L from 2.24 μg/L and chronic concentration of 0.66 μg/L from 0.78 μg/Lfor the maximum application rate for FL citrus scenario. Recommended surface water and groundwater EDWCs for human health are listed in **Table 1**  . **Table 1**  **. Tier II Drinking Water Exposure Estimates for Total Toxic Residues of Difenoconazole Use on Canola/**  **Oilseed Subgroup 20A.**  **Source Peak Exposure (μg/L)**  **Annual Mean Exposure (μg/L)**  **30 -**  **year Average Exposure (μg/L)**  Surface water 1 20.0 13.6 9.9 Groundwater2 1.77 --- 0.66 1 EDWCs generated using PRZM/EXAMS mo del for aerial application of 0.46 lbs a.i./A for grape use (USEPA 2013) 2 Groundwater EDWCs are based on PRZM - GW 100 years simulation and the highest application rate for difenoconazole3

**Drinking Water Exposure Modeling Models**  The EDWCs were generated using EFED’s standard suite of models. Since there is no modification of input parameters for SWCC ( same as PRZM/EXAMS, PRZM - GW and SCI GROW models, detailed description of models and inputs parameters can be obtained from the previous assessment (USEPA, 201 3 , D 412416 ). However, inputs for SWCC in **Table A -**  **1 ,**  for SCI GROW in **Table A -**  **2** , **for** PRZM - GW in **Table A -**  **3** as well as sample output s of SWCC, PRZM - GW and SCIGROW models were provided in the **Appendix A.** In formation concerning the model can be found on the EPA Wat er Models web - page 1 (USEPA, 2010b ) **Surface Water** The Surface Water Concentration Calculator (SWCC v 1.106) model was used to generate E DW Cs for the Tier II aquatic exposure assessment. The SWCC is a graphical user interface that runs the Pesticide Root Zone Model (PRZM, v 5, November 15, 2006) and the Variable Volume Water Body Model (VVWM, 3/6/2014) (USEPA, 2006b). Simulations are run for multiple (usually

3 0) years and the E DW Cs represent peak values that are expected once every ten ye ars based on the thirty years of daily

values generated during the simulation. The default PCA of 1.0 was used for the proposed uses because difenoconazole can be used in both agricultural and non - agricultural settings (USEPA 2012). Estimated difenoconazole concentrations in surface water used for drinking water are summarized in **Table 2.**  The EDWCs for surface water for new uses and cucurbit did not supersede the previously reco mmended drinking water concentrations based on canola use (Table 1) . **Table 2**  **. EDWCs Based on Total Toxic Residues of Difenoconazole for Proposed New Uses**  **Drinking Water Source**  **Crop Crop**  **Scenario Peak (Acute)**  **Exposure Annual Mean** 

**(chronic) Exposure**  **30 -**  **year Mean**

**(cancer chronic)**  **Exposure**

**----------------------- (μg/L)**  **-----------------------** Surface Water 1 Artichoke CArowcropRLF 6.54 5.28 3.97 Ginseng MNsugarbeetST

D 7.48 5.50 4.19 Bushberry NYgrapesSTD 15.0 10.4 7.52

ORberriesOP 7.58 5.61 4.54 Legumes MIbeanSTD 8.89 5.38 3.96

WAbeanNMC 9.52 6.97 4.95 Cucurbit FLcucumberSTD 8.81 3.66 2.74

CAmelonRLF 8.13 5.57 4.50 Ground water FL Citrus Scenario 2 1.77 --- 0.66 Generic Scenario 3 1.48E - 02 --- 1.48E - 02 1 EDWCs generated using SWCC model for aerial application 1 http://www.epa.gov/oppefed1/models/water /index.htm4

**Table 2**  **. EDWCs Based on Total Toxic Residues of Difenoconazole for Proposed New Uses**  **Drinking Water Source**  **Crop Crop**  **Scenario Peak (Acute)**  **Exposure Annual Mean** 

**(chronic) Exposure**  **30 -**  **year Mean**

**(cancer chronic)**  **Exposure**

**----------------------- (μg/L)**  **-----------------------** 2 Highest EDWCs generated using PRZM - GW model based on 0.52 lbs a.i/A for cucurbit for the highest exposure observed in the previous drinking water assessment (USEPA, 2013) 3 EDWCs generated using SCIGROW mo del and assume d 5 equal application rate of 0.114 lbs a.i./A for cucurbit **Groundwater** The Screening Concentration in Ground Water (SCI - GROW v2.3, Jul. 29, 2003) model 1 is a regression model used as a screening tool to estimate pesticide concentrations found in groun dwater that is used for drinking water. SCI - GROW was developed by fitting a linear model to ground water concentrations with the Relative Index of L eaching Potential (RILP) as the independent variable. Ground water concentrations were taken from 90 - day av erage high concentrations from Prospective Ground Water studies. PCAs are not applicable for the SCI GROW model. In addition, Tier 1 groundwater EDWCs for difenoconazole , resulting from its use on cucurbit for its higher application rate of 0. 52 lbs a.i./A w as also estimated using the PRZM - GW model (USEPA, 2012 c ), with the GW - GUI (Graphical User Interface, version 1.0, August 31, 2012). PRZM - GW is a one - dimensional, finite - difference model that estimates the concentrations of pesticides in groundwate r. It accounts for pesticide fate in the crop root zone by simulating pesticide transport and degradation through the soil profile after a pesticide is applied to an agricultural field. PRZM - GW permits the assessment of multiple years of pesticide applic ation (up to 100 years) on a single site. PRZM - GW output values represent pesticide concentrations in a vulnerable groundwater suppl y that is located directl y beneath a rural agricultural field following many ye ars of pesticide application. Recently , PRGM - GW scenarios were revised and consequentl y the e stimated PZRM - GW groundwater concentration s were reduced to 1.77 μg/L from 2.24 μg/L and chronic concentration of 0.66 μg/L from 0.78 μg/L for the maximum application rate for FL citrus scenario reported in previous drinking water assessment (USEPA, 201 3 , D P 412416) . The EDWCs for groundwater for new uses and cucurbit **(Table 2**  **)** supersede d the previousl y recommended drinking water concentrations (Table 1) . **Monitoring Data** Monitoring data for difenoconazol e were available from the United States Geological Survey (USGS ) National Water- Quality Assessment (NAWQA) P rogram Data Warehouse 2 , searched on November 06, 2014. D ifenoconazole was detected in only one of seventy two surface water samples from multiple states ( CA, GA, IA , IN, MO, NE and WI) ; the reported maximum

2 (http://infotrek.er.usgs.gov/nawqa_queries/jsp/swmaster.jsp5

concentration ( 18.2 ng/L ) was detected in California. Difenoconazole was not detected at the limits of quantitation (LOQ) of 0.6 and 1.0 μg/kg - sediment in any of the 83 s ediment s amples collected from multiple states (GA, IA, IN, KS, KY , MO, NE, OH, SD and WI) . However, the study design of NAWQA is not targeted to account for all difenoconazole use areas ; timing of application and other factors which may more accuratel y represent spatially and temporall y dependent variables influencing runoff vulnerability . No groundwater data are available at this time. Monitoring data for surface water, groundwater , and sediment from the California Department of Pesticide Regulation (CDPR) 3 were searched on November 06 , 201 4 . No monitoring data were available for difenoconazole on CDPR’s website .

3 http://www.cdpr.ca.gov/docs/emon/ehap.htm6 **References** US EPA, 2009 a . Difenoconazole Drinking Water Assessment in Support of New Use Registration Action for Bulb Vegetables, Brassica (Cole) Leafy Vegetables, Cucurbit Vegetables, Citrus Fruit, Grapes, and Tree Nuts. May 28, 2009. (D361398) USEPA. 2009b . Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides , Version 2.1 . U.S. Environmental Protection Agency , Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Environmental Fate and Effec ts Division, October 22, 2009 . USEPA. 2010 . Drinking Water Exposure Assessment to Establish a Tolerance of parent difenoconazole on carrot, chickpeas, so yb ean, stone fruits, and strawberry . Environmental Fate and Effects Division, Office of Chemical Saf ety and Pollution Prevention. U. S. Environmental Protection Agency (D426124) . USEPA. 2011 . Difenoconazole **:** Report of the Residues of Concern Knowledgebase Sub committee (ROCKS) . Health Effects Division , Office of Chemical Safety and Pollution Preventio n. U. S. Environmental Protection Agency ( D391350 ) US EPA . 20 12c. Memorandum: Approval of PRZM - GW for use of Drinking Water Exposure Assessment. Environmental Fate and Effects Division, Office of Chemical Safety and Pollution Prevention. U. S. Environmental Protection Agency . USEPA 2013a. D rinking W ater E xposure A ssessment in support of the new use registration of difenoconazole formulated product Inspire on Canola/Oilseed Subgroup 20A. Environmental Fate and Effects Division, Office of Chemical Safety and Pollution Prevention. U. S. Environmental Protection Agency (D 412614) . USEPA, 2013b. Guidance on modeling off - site deposition of pesticides via spray drift for ecological and drinking water assessments. Environmental Fate and Effects Division, Office of Chemical Safety and Pollution Prevention. U. S. Environmental Protection Agency7 **APPENDIX A**  **The input parameters used for SWCC**  **modeling. Table A**  **- 1.**  **Chemical Specific SWCC Model**  **Input Parameters for Difenoconazole**

**Parameter Input Value and Unit**  **Source/Comments Crops**  Artichoke Ginseng Bushberry Legumes Cucurbit **Scenario** CArowcrop RLF MNsugarbeetSTD ORberriesOP and NYgrapeSTD MIbeanSTD and WAbeanNMC FLcucumberSTD an CAMelonRLF Surrogate scenario Surrogate scenario Surrogate scenarios Standard and surrogate scenarios Standard and surrogate scenarios **Maximum single application rate**  **x Maxim um** **# of application** Artichoke, ginseng, bushberry, and legume s Cucurbit 0.11 5 lbs a.i. /A (0.12 9 kg a . i/HA) x 4

0.11 4 lbs a.i. /A (0.12 8 kg a.i. /HA) x 4 and 0.064 lbs a.i. /A (0. 072 kg a.i. /HA) x 1 EPA Reg. No. 100 - 1262, EPA Reg. No. 100 - 1312 EPA Reg. No. 100 - 1313 EPA Reg. No. 100 - 1317 EPA Reg. 100 - 1317 Method of application CAM = 2 Foliar Spray Product Label as above Application efficiency 0.95 (Aerial Spray) Generally aerial scenario generates higher exposure as compared to ground and chemigation scenarios EFED Model Input Guidance, Version 2.1 (2009b) a Spray drift 0. 135 (Aerial Spray) USEPA 2013. **Crop** Scenario: Application date and minimum interval between applications (days) **Artichoke** CArowcrop: June 9 (14) Assumed 21 - days for application intervals between 2 nd and 3 rd **Ginseng** MNsugarbeet: Sept 17 (7) Assumed 14 - days for application intervals between 2 nd and 3 rd **Busherry** ORberries: June 19 (7) NYgrape: Sept 10 (7) Assumed 14 - days for application intervals between 2 nd and 3 rd **Legume** MIbean: July 03 WAbeanOP: July 01 Assumed 14 - days for application intervals between 2 nd and 3 rd **Cucurbit** FLcucumber: Oct 22 (7) CAmelon: June 14 (7) Assumed 14 - days for application intervals between 2 nd and 3 rd and 4 th and 5 th Hydroly sis Stable MRID 422451278 **Parameter Input Value and Unit**  **Source/Comments** Aerobic soil metabolism (t 1/2 ) b 489.6 days MRIDs: 42245131, 46950109 - 12, and 46950114 Aerobic aquatic metabolism (t 1/2 ) c 632.9 days MRIDs: 46950116 & 46950117 Anaerobic aquatic metabolism (t 1/2 ) d 1485.3 days MRID 46950119 Aquatic photolysis t 1/2 (days) e Stable MRID 46950105 Vapor pressure 2.5 x 10 - 10 mm Hg (25 o C) MRID 46515901 Solubility in water 15 mg/L (25 o C) MRID 46515901 Molecular Weight 406.27 MRID 46950104 Partition coefficient Koc 5381 mL/g MRIDs: 42245135 and 46950121 a Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides (Version 2.1; Oct. 22, 2009) b The 90% of the UCL of the mean metabolism Half - life. c The 90% of the UCL of the mean metabolism Half - life of all av ai lable Half

- lives but those obt ained for high test rate. d Half - life was multiplied by three (i.e., 3 x 495.1 days). e Estimated Half

- life is beyond the duration of study, thus considered stable. 

## Sample Output: **Summary of Water Modeling of Difenoconazole and the USEPA Standard Reservoir**  Estimated Environmental Concentrations for Difenoconazole are presented in Table 1 for the USEPA standard reservoir with the NYGrapesSTD 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 2.3% of Difenoconazole applied to the field eventually reaches the water body. The main mechanism of trans port from the field to the water body is by erosion ( 68% of the total transport), followed by spray drift (17.6%) and runoff (14.5%). In the water body, pesticide dissipates with an effective water column half- life of 199.7 days. (This value does not incl ude 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 washout (effective average half- life = 228.7 days) followed by metabolism (1579.9 days) and volatilization (3.965328E+07 days). In the benthic region, pesticide dissipation is negligible (3702.7 days). The main source of dissipation in the benthic region is metabolism (effective average half- life = 3702.7 days). Th e vast majority of the pesticide in the benthic region (99.83%) is sorbed to sediment rather than in the pore water. **Table 1. Estimated Environmental Concentrations (ppb) for Difenoconazole.** Peak (1 - in - 10 yr) 15.0 4 - day Avg (1 - in - 10 yr) 14.2 21 - day Avg (1 - in - 10 yr) 12.69

60 - day Avg (1 - in - 10 yr) 11.6 365 - day Avg (1 - in - 10 yr) 10.4 Entire Simulation Mean 7.52 **Table 2. Summary of Model Inputs for Difenoconazole.** Scenario NYGrapesSTD Cropped Area Fraction 1.0 Koc (ml/g) 5381 Water Half- Life (days) @ 25 °C 632.9 Benthic Half- Life (days) @ 25 °C 1483.3 Photolysis Half - Life (days) @ 40 °Lat 0 Hydrolysis Half- Life (days) 0 Soil Half- Life (days) @ 25 °C 489.6 Foliar Half- Life (days) Molecular Wt 406.27 Vapor Pressure (torr) 2.5E - 10 Solubility (mg/l) 15 **Table 3. Application Schedule for Difenoconazole.** Date (Mon/Day) Type Amount (kg/ha) Eff. Drift 09/10 Foliar 0.129 0.95 0.135 09/17 Foliar 0.129 0.95 0.135 10/01 Foliar 0.129 0.95 0.135 10/08 Foliar 0.129 0.95 0.135 **Figure 1. Yearly Peak Concentrations** 1011 **Input and Output of SCI -**  **GROW Model The input parameters used for SCI**  **- GROW modeling**  **Table A** **- 2. SCI**  **- GROW Input Parameters for Difenoconazole Applied on**  **Multiple Crops**  **at the Maximum Label Application Rate. Model**  **Input Variable Input**  **Values** Koc ( the lowest value of all available Koc s, MRIDs: 42245135 and 46950121 ) 1 3471 ml/g Application Rate 0. 114 lb . a.i./acre Number of Applications 5 Aerobic Soil Metabolism half - life 2 223.6 days Hydroly sis Stable 1 The Koc shows greater than three - folds variation, thus, the lowest value was uses per guidance as of Oct . 2 2 , 200 9 (USEPA 2009b) . 2 Median of seven values. **O utput of**  **SCIGROW modeling**  SCIGROW VERSION 2.3 ENVIRONMENTAL FATE AND EFFECTS DIVISION

OFFICE OF PESTICIDE PROGRAMS U.S. ENVIRONMENTAL PROTECTION AGENCY

SCREENING MODEL FOR AQUATIC PESTICIDE EXPOSURE SciGrow version 2. 3 chemical:Difenoconazole time is 10/27/2014 16:32:17

------------------------------------------------------------------------ Application Number of Total Use Koc Soil Aerobic rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------

0.114 5.0 0.570 3.47E+03 223.6

------------------------------------------------------------------------

groundwater screening cond (ppb) = 1.48E - 02 ************************************************************************12 **Input and Output of**  **PRZM -**  **GW modeling**  **Table A**  **- 3**  **. PRZM -**  **GW Input Parameters**  **1 for**  **Difenoconazole Uses**  **Variable Nam e**  **Data Value Data Source**  **MRID(s) Comment**  Application Method Aerial (Cucurbit) Proposed labels EPA Reg# 100 - 1317 Maximum Single Application Rate X Maximum # of application (lbs. a.i./acre) [kg/ha] Cucurbit 0.11 4 [0.12 8 ] x 4 plus 0. 064 (0. 072 ) x 1 Proposed labels EPA Reg# 100 - 1317 Application Interval (days) 7 Proposed labels EPA Reg# 100 - 1317 Hydroly sis, DT 50 (Days) stable MRID 42245127 --- Aerobic Soil Metabolism DT 50 (Days) 489.6 days MRIDs.: 469501 16 & 469501 17 The 90% of the upper

confidence limit (UCL ) of the mean metabolism half - life . Koc ( mL/g oc ) 5381 MRID s: 42245135 and 469501 21 Average Koc **1** EFED input parameter guidance: http://www.epa.gov/oppefed1/models/water/przm_gw/wqtt_przm_gw_input_guidance.htm 

## Groundwater Analysis for Difenoconazole and the Florida Citrus **- FL Central Ridge, Polk County**  **- (Tam** **pa) Met File (12842.Dvf) -**  **Astatula Sand, Hrgb A Scenario** Estimated groundwater concentrations and breakthrough times for Difenoconazole are presented in Table 1 for the Florida Citrus - FL Central Ridge, Polk County - (Tampa) Met File (12842.dvf) - Astatula sand, hrgb A groundwater scenario. A graphical presentation of the dail y 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 Difenoconazole and the Flori da Citrus**  **- FL Central Ridge, Polk County**  **- (Tampa) Met File (12842.dvf)**  **- Astatula sand, hrgb A Scenario.**  Peak Concentration (ppb) 1.78 Post - Breakthrough Mean Concentration (ppb) Incomplete Entire Simulation Mean Concentration (ppb) 0.65913

Average Breakthrough Time (days) Incomplete Throughputs 0.8163512 **Table 2. Chemical Properties for Groundwater Modeling of Difenoconazole.** Koc (ml/g) 5381 Surface Soil Half Life (days) 490 Hydroly sis Half Life (days) 0 Diffusion Coefficint Air (cm2/day) 0 Henry's Constant 0.0 Enthalpy (kcal/mol) 0.0 **Table 3. Pesticide application scheme used for Difenoconazole. This application scheme was applied every year of the simulation.**  Application Date (Month/Day) Application Method Application Rate (kg/ha) 10/22 Ground application with mass distribution increasing proportionally with depth to 4 cm 0.128 10/29 Ground application with mass distribution increasing proportionally with depth to 4 cm 0.128 11/12 Ground application with mass distribution increasing proportionally with depth to 4 cm 0.128 11/19 Ground application with mass distribution increasing proportionally with depth to 4 cm 0.128 12/03 Ground application with mass distribution increasing proportionally with depth to 4 cm 0.072 **Figure 1. Aquifer Breakthrough Curve for Difenoconazole and the Florida Citrus -**  **FL Central Ridge, Polk County**  **- (Tampa) Met File (12842.Dvf)**  **- Astatula Sand, Hrgb A**  **Scenario**14